The 5S System – Lean Thinking

Lean Manufacturing and the Environment

From the Environmental Protection Agency (EPA)

Introduction

5S is a system to reduce waste and optimize productivity through maintaining an orderly workplace using visual cues to achieve more consistent operational results. Implementation of this method “cleans up” and organizes the workplace basically in its existing configuration, and it is typically the first lean method which organizations implement.

The 5S pillars (originally 5 Japanese words, they have been loosely translated for English adaptation)

• Sort (Seiri)
• Set-in-order (Seiton)
• Shine (Seiso)
• Standardize (Seiketsu)
• Sustain (Shitsuke)

provide a methodology for organizing, cleaning, developing, and sustaining a productive work environment. In the daily work of a company, routines that maintain organization and orderliness are essential to a smooth and efficient flow of activities. This lean method encourages workers to improve their working conditions and helps them learn to reduce waste, unplanned downtime, and in-process inventory.

A typical 5S implementation would result in significant reductions in the square footage of space needed for existing operations. It also would result in the organization of tools and materials into labeled and color coded storage locations, as well as “kits” that contain just what is needed to perform a task. 5S provides the foundation on which other lean methods, such as TPM, cellular manufacturing, just-in-time production, and six sigma can be introduced.

Method and Implementation Approach

5S is a cyclical methodology: sort, set in order, shine, standardize, sustain the cycle. This results in continuous improvement.

The 5S Pillars

Sort. Sort, the first S, focuses  on eliminating unnecessary items from the workplace that are not needed for current production operations. An effective visual method to identify these unneeded items is called “red tagging”. which involves evaluating the necessity of each item in a work area and dealing with it appropriately. A red tag is placed on all items that are not important for operations or that are not in the proper location or quantity. Once the red tag items are identified, these items are moved to a central holding area for subsequent disposal, recycling, or reassignment. Organizations often find that sorting enables them to reclaim valuable floor space and eliminate such things as broken tools, scrap, and excess raw material.

Set in Order. Set in Order focuses on creating efficient and effective storage methods to arrange items so that they are easy to use and put away. Set in Order can only be implemented once the first pillar, Sort, has cleared the work area of unneeded items. Strategies for effective Set in Order include painting floors, affixing labels and placards to designate proper storage locations and methods, outlining work areas and locations, and installing modular shelving and cabinets.

Shine. Once the clutter that has been clogging the work areas is eliminated and remaining items are organized, the next step is to thoroughly clean the work area. Daily follow-up cleaning is necessary to sustain this improvement. Working in a clean environment enables workers to notice malfunctions in equipment such as leaks, vibrations, breakages, and misalignment. These changes, if left unattended, could lead to equipment failure and loss of production. Organization often establishes Shine targets, assignments, methods, and tools before beginning the Shine Pillar.

Standardize. Once the first 3S’s have been implemented, the next pillar is to standardize the best practices in the work area. Standardize, the method to maintain the first three pillars, creates a consistent approach with which tasks are procedures are done. The three steps in this process are assigning 5S (Sort, Set in Order, Shine) job responsibilities, integrating 5S duties into regular work duties, and checking on the maintenance of 5S. Some of the tools used in standardizing the 5S procedures are: job cycle charts, visual cures (e.g., signs, placards, display scoreboards), scheduling of “5-minute” 5S periods, and check lists. The second part of Standardize is prevention- preventing accumulation of unneeded items, preventing procedures from breaking down, and preventing equipment and materials from getting dirty.

Sustain. Sustain, making a habit of properly maintaining correct procedures, is often the most difficult S to implement and achieve. Changing entrenched behaviors can be difficult, and the tendency is often to return to the status quo and the comfort zone of the “old way” of doing things. Sustain enforces on defining a new status quo and standard of work place organization. Without the Sustain pillar the achievements of the other pillars will not last long. Tools for sustaining 5S include posters, newsletters, pocket manuals, team and management check-ins, performance reviews, and department tours. Organizations typically seek to reinforce 5S messages in multiple formats until it becomes “the way things are done”.

Proper discipline keeps the 5S circle in motion.

Implications for Environmental Performance

Potential Benefits: Painting the machines and the equipment light colors and cleaning the windows, often done under the Shine pillar, decreases energy needs associated with lighting. Painting and cleaning makes it easier for workers to notice spills or leaks quickly, thereby decreasing spill response. This can significantly reduce waste generation from spills and clean-up.

The removal of obstacles and the marking of main thoroughfares decreases the potential of accidents that could lead to spills and associated hazardous waste generation (e.g., spilled material, absorbent pads and clean up materials). Regular cleaning, as part of the Shine Pillar, decreases the accumulation of cuttings, shavings, dirt, and other substances that can contaminate production processes and result in defects. Reduction in defects has significant environmental benefits (e.g., avoided materials, wastes, and energy needed to produce the defective output; avoided need to dispose of defective output).

5S implementation can significantly reduce the square footage needed for operations by organizing and disposing of unused equipment and supplies. Less storage space decreases energy needed to heat and light the space.

Organizing equipment, parts and materials so they are easy to find can significantly reduce unneeded consumption. Employees are more likely to finish one batch of chemicals or materials before opening or ordering more, resulting in less chemicals or materials expiring and needing disposal.

5S visual cues (e.g., signs, placards, scoreboards, laminated procedures in workstations) can be used to raise employee understanding of proper waste handling and management procedures, as well as workplace hazards and appropriate emergency response procedures. 5S techniques can be used to improve labeling of hazardous materials and wastes. In addition, environmental procedures are often separate from operating procedures, and they are not easily accessible to the workstation. 5S implementation often results in easy to read, laminated procedures located in workstations. Integration with 5S visual cues and operating procedures can improve employee environmental management. 

Potential Shortcomings: Regularly painting and cleaning machines and equipment could lead to increased use of paints and cleaning supplies. Paints and cleaning supplies may contain solvents and/or chemicals that can result in air emissions or increased waste generation.

Disposing of unneeded equipment and supplies creates a short term surge in waste generation. In some cases, there may be unlabeled wastes that could be hazardous. Failure to involve environmental personnel in waste handling could result in some wastes being disposed improperly or in lost opportunities for reclamation or recycling.

Useful Resources

Greif, M.. The visual Factory: Building Participation Through Shared Information (Portland, Oregon: Productivity Press, 1995).

Hirano, Hiroyuki. 5 Pillars of the Visual Workplace (Portland, Oregon: Productivity Press, 1995).

Peterson, Jim, Roland, Smith, Ph.D.. The 5S pocket Guide (Portland, Oregon: Productivity Press, 1998).

Pojasek, Robert B. “5Ss: A Tool That Prepares an Organization for Change”. Environmental Quality Management (Autumn 1999) 97-103.

Productivity Press Development Team. 5S for Operators: 5 Pillars of the Visual Workplace (Portland, Oregon: Productivity Press, 1996)

Productivity Press Development Team. 5S Safety Implementation Toolkit: Creating Safe Conditions Using the 5S System (Portland, Oregon: Productivity Press, 2000)

Productivity Press Development Team. 5S for Safety: New Eyes for the Shop Floor (Portland, Oregon: Productivity Press, 1999)

Shimbun, Nikkan Kogyo, ed. Visual Control Systems (Portland, Oregon: Productivity Press, 1999)Tel-A-Train and the Productivity Development Team. The 5S System: Workplace Organizations Standardization (Video) (Portland, Oregon: Productivity Press, 1997).

Ergonomics for the Standing Worker

By Lisa O’Dell, VP of Marketing at Wearwell

The word “ergonomics” is defined as “the natural laws of work”. Optimal performance, which many of us define as productivity, is the ultimate goal of ergonomic design. It’s therefore reasonable to expect that the implementation of ergonomic concepts offers tremendous value to any company, and can be realized with the creation of comfortable, healthy, and safe work environments. Providing anti-fatigue  matting for standing workers is an excellent example of ergonomic design.

Past research has been shown that long-term standing on hard surfaces negatively effects workers’ productivity and health. On a simplistic level everyone knows that it’s uncomfortable. On a more complex level, standing on hard surfaces is uncomfortable because leg muscles become static, continuously flexed in an attempt to keep your body in an upright position. In the short term, this reduces the natural flow of oxygen and blood back to your heart causing fatigue and blood pooling in your lower extremities. In the long term, it will take a toll on your body in the form of varicose veins, low back pain, leg pain, and fallen arches, just to name a few of the most common ailments. The most functional, comfortable and effective solution for eliminating standing workers aches and pains is the use of well-designed anti-fatigue matting. These ergonomic products can play a huge part in injury prevention, the reduction of standing worker fatigue, and increased productivity.

Anti-fatigue mats work by encouraging subtle movements of leg and calf muscles. As the muscles contract and relax they pump blood back to the heart and eliminate blood pooling in the lower extremities which often occurs if a worker’s muscles are totally static.

Once anti-fatigue mats are installed, it is very common to hear stories about how they dramatically help a particular employee. For example, a Rolls Royce assembly plant purchased anti-fatigue matting for several operations including welding stations. One of their employees, a 39 year old welder, suffered from Plantar Fasciitis, which is an inflammation of the connective tissue on the bottom of the foot. This is a very painful condition often caused by prolonged standing. Rolls Royce tried several remedies including gel insoles, which were found to be a nuisance and not very effective. After standing on Wearwell® WeldSafe® Anti-fatigue matting for several weeks, the production manager said that the welder was much more comfortable and had in fact stated that his work conditions are 90% improved.

Not all companies have such dramatic results, but virtually all would tell you that anti-fatigue mats make a very positive impact on their employees’ morale and performance. To insure that the overall experience with matting is good, it’s imp0rtant to:

1. Understand that you will probably not be able to please very employee because everyone enjoys a different level of comfort, and
2. Select products that optimize performance.

Here are some classic examples:

• If you have an area where carts are pushed from workstation to workstation, it is best to find a product that will withstand cart traffic (ErgoDeck)
• If you have over-spray buy a mat that has an abrasive coating on the surface to provide necessary traction (Diamond-Plate with GritWorks!)
• Buy wet area matting for wet areas and dry mats for dry areas (24/Seven for wet areas and Diamond-Plate for dry areas)
• If you frequently reconfigure workstations or have very large areas to cover, look at the modular on the market (ErgoDeck)
• IF you use caustic chemicals in your facility, test the mat yourself to make sure it will withstand the rigors of your environment (24/Seven CFR)
• If you have employees that require an extra level of comfort, look for the greater compression deflection test results or the lower durometer (UltraSoft Diamond-Plate)

Perhaps most importantly, always purchase anti-fatigue mats that adapt the work environment to the needs of the worker. This will ensure optimal performance and that is truly ergonomics at work.

You can find all of the Wearwell matting options at Production Automation’s website (www.gotopac.com) and for a limited time, all Wearwell mats ship free! If you have questions or need help deciding which mat is right for your environment, feel free to call us at 888-903-0333 Monday through Friday, or Email us at info@gotopac.com. We would be more than happy to help you decide what would work best for you!

Air Showers – Are They Worth It?

A Discussion about Air Showers, from Liberty Industries “Air Shower Newsletter”

Do they really reduce contamination?

The efficacy of air showers in the contamination control process has been a source of debate for several years.

Tests have been conducted which prove the effectiveness of air showers. The tests do show that an air shower does reduce particulate. For the most part, reduction in particulate matter is dependent upon the particle size, the type of garment worn, the cycle time, and directly relates to the air shower design and how it is used and maintained.

Does the use of an air shower justify its cost?

As a percentage of the total cost of the modern cleanroom, the cost of an air shower is virtually insignificant. In any application where contamination is critically important- such as life science, biomedical, pharmaceutical, parenteral drug, microelectronics, aerospace, and precision manufacturing- air showers should be considered essential equipment.

If its use could eliminate contamination of one expensive batch of pharmaceutical chemicals or the rejection of one semiconductor wafer, for example, it is m0ney well spent. Perhaps millions of dollars could be saved.

In addition, from a psychological point of view, having operating personnel pass through an air shower before entering the work area, reinforces the fact that cleanliness to the operation is essential. This, hopefully, reinforces the concept that protection of the product from personnel is a significant concern.

A brief history of the emergence of contamination control technology:

In today’s modern world of manufacturing and research, and development, contamination control has become a necessary of the manufacturing process. In fact, without it, many of the advances made in the last twenty years or so would not have been possible.

Contamination control technology is not confined to any one industry. Its practice transcends specific industries and is used, to some degree, in just about all manufacturing and research and development processes.

Without contamination control technology, the developing broad field of life sciences encompassing biotech, biomedical, pharmaceutical, parenteral drug, microelectronics, aerospace, and precision manufacturing would not have been able to achieve some of the discoveries that have been made to date nor the discoveries yet to be made. While nanotechnology, a new emerging field of study in which its research is done at the at the atomic or molecular level, could not exist without the advancements made in contamination control technology over the years.

Dealing with the issues of contamination control on a microscopic or smaller scale has lead to the creation of the modern cleanroom and along with it, the air shower.

The primary focus of a cleanroom is to control the levels of contamination by creating a differential pressure between the cleanroom and the surrounding area and to filter the air entering the room to prevent the entry of unwanted particulate matter and to change the air in the room with an air-handling system to purge particulate matter created within the room. The cleanroom itself is constructed of materials that tend to resist particulate generation, hence minimizing additional contamination. More sophisticated cleanrooms can also control temperature and humidity in the workspace.

In the conventional cleanroom, low velocity air enters from the ceiling plenum through perforated diffusers and carries out contamination through wall exhausts close to floor level. In the laminar flow cleanroom, air is introduced uniformly at low velocities into a space confined on four sides and through an opening equal to the cross sectional area of the confined space- a technique that stratifies the air and minimizes cross-stream contamination.

To keep this particulate matter from being recycled, both types of rooms use HEPA (High Efficiency Particulate Air) Filters. HEPA Filters are manufactured from glass fiber, accordion-style pleated filters that can be up to 99.99% efficient in removing particles .03 microns and larger. For more stringent requirements , an ULPA (Ultra Low Particulate Air) Filter may be used. An ULPA filter has the ability to remove a higher percentage of 0.3 micron particles than a HEPA filter.

Contamination vs. Particulate Matter: 

So far in this discussion the terms “particulate matter” and “contamination” have been used interchangeably.

A contaminate is any foreign substance that will have a detrimental effect on whatever you are trying to accomplish. This most significant form of contamination in cleanrooms is submicroscopic matter that are distributed in the air in the form of fine particles or fibers or carried into the cleanroom and redeposited by workers.

To be technically correct, however, it should be pointed out that not all particulate matter is a contaminate. To be considered a contaminate, a particulate matter must meet three criteria:

1. It must be able to migrate to the vulnerable area, either by air currents, by fluids, or through transference from personnel
2. It must be significant in number
3. It must have physical properties that cause damage

Sources of Contamination:

Just about all industrial activities produce contaminates. Operating personnel present the most significant source contaminates – hair, skin, dandruff, as well as nasal and oral emissions- to name a few. While contaminates can and do differ in terms of hardness, size, shape, translucency, color, ect. their size in most cases, determines the degree of potential harm they can cause.

There is a very delicate balance between the contamination level, the number of personnel in a cleanroom and how they go about performing their assigned tasks. Some contamination is inevitable. In reality, there is very little you can do about this natural propensity to create contaminates except to instruct workers in correct cleanroom procedure and to deal with the unavoidable contamination as it arises. This is what cleanrooms have always done. You can certainly help matters by limiting the amount of contaminates that any specific individual brings in from the outside.

An air shower can be an integral part of the contamination control process because it can minimize the amount of contaminates brought into the cleanroom from the outside:

An air shower is nothing more than a device meant to limit the contamination brought into a controlled area such as a cleanroom. It works by moving air over the worker at a specific high velocity for a specified period of time. In a properly designed air shower, particles are driven off and away from the body and deposited on the upstream side of the HEPA or ULPA filters.

Air showers have been used effectively in the cleanroom industry for over thirty-five years and have been instrumental in reducing the level of contamination brought into the cleanroom.

Normally positioned between the cleanroom and the outside environment, an air shower is a chamber equipped with a blower unit, interlocking doors, HEPA filters and prefilters, a recirculating air system and multiple air nozzles. Various size nozzles are arranged on the walls and ceiling in a predetermined pattern for the most effective removal of loose particles, dust, or other particulate matter from the garments.

Filtered air is blown through the nozzles directly against the individual standing within the air shower, creating a flapping and shearing effect designed to remove loose contaminates prior to entering a change room, wash room, ante-room, or cleanroom. The air is sucked and taken from the chamber, stripped of its contaminates through the filtration system, and recycled back to the air shower to continue the cleaning job.

Today’s air shower is equipped with a powerful blower unit, solid state electrical control panels complete with safety monitors and and emergency shut down capabilities that may be activated from both the interior and exterior of the unit. Fluorescent lighting flush ceiling mounted for maximum brightness.

Is there a difference between Air Showers and an Air Lock? 

An air shower is usually built into an air lock. It is important to remember that there is a big difference between the two.

An air lock is a room, corridor or some other space which separates the cleanroom from a less clean area. Generally, it has two doors at opposite ends and is frequently designed with an electrical or mechanical interlock so that one door cannot be opened unless the other one is closed. Its purpose is to prevent the loss of valuable cleanroom air whenever a person leaves or enters the room and also to prevent contaminated air from entering the cleanroom when a door is opened. It also has the ability to conserve energy.

While an air shower can function in this capacity, it also has the additional advantage of being able to actively clean off contamination from the person entering the cleanroom with jets of filtered air coming out of the nozzles.

How does an Air Shower work?

Typically an air shower can be operated in three distinctly different ways depending on process requirements:

1. One Way
2. Two Way, One Way
3. Two Way

One Way Operation:

• Exit door locked at rest, entrance door unlocked. When the user enters the air shower, the entrance door closes and locks; then the air shower cycle starts.
• At the end of the cycle, the entrance door stays locked and the exit door unlocks so that the user can leave.
• When the exit door is closed, it locks again and the entrance door unlocks.
• The air shower is now ready for use again.

Two Way, One Way Operation:

• The air shower is used in both directions, but operates the air shower in only one direction.
• Only one door at a time can be opened.
• Both doors are unlocked at rest. The user enters the air shower via the entrance door. At the end of the air shower cycle, he leaves the exit door.
• Or a user can enter the unit via the exit door, once the exit door closes the user can immediately leave via the  door without activation of the cycle. Both doors cannot be opened at the same time.

Two Way Operation:

• In this mode, the cycle runs in both directions.
• only one door at a time can be opened. The user can go in either direction and the air shower will cycle.

Test data has been obtained which prove that air showers are effective in reducing contamination brought into the cleanroom.

Data developed by a Japanese company several years ago indicates that, depending on the particle size, particle removal can be up to 90%. The larger particle the higher the efficiency.

It is to be noted that proper operating protocol in using an air shower weighs greatly on its effectiveness. Training is of utmost importance to insure reduced contamination levels in cleanrooms and to ensure that the air shower is operating at maximum effectiveness. Proper protocol suggests personnel should be trained to rotate continuously 360 degrees, with hands on their heads, as shown during the air shower cycle to insure contamination removal is as efficient as possible.

The Air Force has very exacting standards regarding acceptable levels of contamination while at the same time, has equally exacting standards when it comes to investing in equipment. In order to determine the efficacy of air showers the Air Force conducted tests of it own.

 

The test consisted of sending a team of twenty operating personnel through two air showers, one located before the entrance to the change room and the other before the entrance to the cleanroom itself with a cycle time of eight seconds each. operators were instructed to raise their arms and make a 360 degree turn. Prior to the entrance to the first shower, outer garments are removed and stored. Once passed the first air shower, the individual enters the change room where he puts on the cleanroom garments and goes through the second air shower, entering the cleanroom. After each test condition, the cleanroom was allowed to return to normal contaminate level before a new test was begun and collections of samples were made.

As can be seen, the level of contamination removal was at least 44% with at least one air shower in operation. With two air showers in operation, contamination removal was 80%.

Further independent testing on the type of material workers are clothed in demonstrates that what the worker wears can make a significant difference in the amount of particulate removed by the air shower as indicatd in the chart below:

Today’s Air Showers can keep a significant amount of residual contamination from entering a cleanroom workplace as long as certain criteria are met:

1. The air shower must be properly designed and sized to maintain effective and efficient operations
2. At a minimum, HEPA filters are 99.99% efficient at 0.3 microns or optional ULPA filter at 99.999% efficient at 0.12 microns
3. Sufficient “wash down time” – at least 45 seconds – must be allowed in the air shower
4. The air supplied to the shower must be finely filtered to prevent personnel  from being impinged with contaminants during the actual cleaning cycle
5. A fixed nozzle pattern must be followed and the nozzles must be preset to direct air in a downward flow to produce a shearing, wash down effect.  It is essential to have a fluttering of garments strong enough to loosen dust.
6. The garments themselves must be made of material such as Tyvek, teflon, dacron, or nylon that is less likely to shed than cloth; comfort and cost must not be the determining factor
7. The air shower must operate at a negative pressure. In other words, the pressure in the air shower must not exceed the pressure outside. The pressure must be less than the cleanroom side to prevent contaminates
8. Very importantly, personnel must act responsibly, i.e., when they stand off-center or crouch in a corner to avoid the air flow, they are defeatign the whole purpose of the air shower. The individual must center himself in the shower and execute several complete 360 degree turns during the 45 second duration of the air shower, with hands positioned over the head.
9. The individual must remain in the air shower for several moments as specified in the company’s protocol after it has stopped to allow enough “purge time” or “dwell time” so that the particles may drift downward throught the floor grate and are not drawn into the cleanroom by the movement of the individual as he leaves the air shower
10. Air showers, like cleanrooms, or for that matter any process equipment, must be properly maintained in order to function properly. Lack of proper maintance can become a major sorce of contamination.

__________________________________________________________

Production Automation is a proud distributor of Liberty Air Showers with many options to suit your particular needs and requirements. From stainless steel and High/Low Volume showers, to custom projects.

Beacuse of the many varients that go into pricing these air showers, please contact us if you are interested in purchasing a Liberty Air Shower and we will be more than happy to work with you to find the exact product you need at the best pricing.

We can be contacted via email at info@gotopac.com , or you can call us monday through friday at 888-903-0333, or a third option would be to follow the request quote link on the right hand side of our blog.

Production Automation Electronics Promotions

Production Automation has specials running on four different product lines. Some of them have been blogged about here already and some have not.

We wanted to recap all of the specials because some of them end March 31st, while others are running longer.

Hakko Soldering Products

Silver Lining ‘09

Hakko’s Silver Lining ‘09 is celebrating Hakko’s 25th year in the industry. From now until March 31st, Hakko is offering 25% off of 25 different Hakko products:

FM203-01 Dual Port Soldering Station

FM203-DP Dual Port Soldering Station

FX951-66 Compact Soldering Station

FX301B-03 Digital Soldering Pot

FX300-03 Analog Soldering Pot

FX780-01 Table Top Nitrogen Generator

FM2026-KIT Nitrogen Controller

FM204-01 Desoldering Station

FM204-CP Desoldering/Soldering Station

FM205-01 Shop Air Desoldering Station

FM2024-21 Desoldering Module

FM2022-05 Parallel Remover

FM2023-05 Mini Hot Tweezer

FR801-11 SMD Hot Air Rework Station

FR802-11 SMD Hot Air Rework Station

FR803B-11 SMD Hot Air Rework Station

FR820-02 Preheater

FR1012B-01 Preheater

FT700-05 Tip Cleaner

FG100-01 Celsius Thermometer

FG100-02 Fahrenheit Thermometer

FG101-10 Fahrenheit Tester

FG101-16 Celsius Tester

FT800-01 Thermal Wire Stripper

HJ3100 Fume Extraction System

Free Shipping on Hakko’s 936-12 Station

The 936 soldering station is an inexpensive, temperature adjustable station that you can stack to conserve valuable bench space. ESD safe by design.

Adjustable temperature control with lock/set screw

Temperature range 200°C – 480°C (392°F – 896°F)

Maintains idle temperature within 1°C (1.8°F)

Ceramic heating element and sensor ensures rapid heat-up temperature (30 seconds) and lightning-fast thermal recovery

Celsius or Fahrenheit temperature setting

Temperature adjusted by simply turning the dial

Slender iron handles are insulated and ergonomic-designed for ease and comfort

Accommodates large, medium, or small irons

Wide selection of tips available for soldering SMD and through-hole connections

Hakko sale pricing ends March 31st

Brady Printers & Labels

Brady is giving away free handheld label printers until March 31st.

HandiMark Handheld Color Printer

Simply place your order with a quantity of 12 or more cartridges and you will automatically receive a printer. That is a savings of $775!

HandiMark Version 3.0 Printer Gives You The Power To Create Custom Labels Anytime, Anywhere.
The latest release of the HandiMark® Portable Label Maker offers 30% faster printing speed, with additional upgrades that increase functionality and efficiency, such as auto recall, sleep mode and a clearer graphical display. The Brady HandiMark printer is ideal for creating highly visible labels in facilities like mechanical maintenance facilities, production and operations, warehouses and storerooms, and laboratories. This full-featured printer offers bold, easy to read text from 0.08″ to 1.7″, bar coding capabilities, 12 resident operating languages, alpha-numeric sequencing, and PC compatibility. HandiMark also incorporates a variety of stock industrial-grade label materials and specialty tapes.

TLS 2200 Handheld Thermal Printer

Simply place your order with a quantity of 15 or more cartridges and you will automatically receive a printer. That is a savings of $775!

The TLS 2200®is a light weight (2.75 lb/1.25 kg) portable printer packed with features to make identifying your structured cabling environment a snap. This thermal transfer printer delivers crisp, clear, non-smearing labels every time and its smart cell technology guaranties ease of use. Just drop the labels in and print. The TLS 2200® will automatically serialize, and can also print two copies of each serialized label – one for each end of the run. Features include memory for label storage, banner printing, and PC connectivity. More than 500 different labels are available to fit all your identification needs.

Brady Free Printer Specials end March 31st

ASG Hand Tools

ASG is a leading supplier of products for light assembly. They have an extensive product line, and 20 years experience in the industry. From now until June 1st they are offering you two great deals!

Free Power Supply with purchase of TL Driver

Choose from one of four TL drivers and automatically receive a PS-55 power supply FREE!

• TL-3000 Precision Torque DC Driver
• TL-6500 Precision Torque DC Driver
• TL-3000 ESD Precision Torque DC Driver
• TL-6500 ESD Precision Torque DC Driver

Save 20% on ASG Easy Order Kits

These kits save you time and money, bundling everything you need to get the job done! All Kits include: Tool Support Stand, Tool Positioner, and PS-55 Power Supply.

•  Kit One: CL-4000 DC Electric Medium Size – Inline
• Kit Two: CL-6500 DC Electric Standard Size Driver – Pistol Grip
• Kit Three: BL-5000 Brushless DC Electric Driver: Medium size – Inline

ASG Specials end June 1st

OC White Magnifiers & Microscopes

OC White products are manufactured with the highest degree of quality and dependability. From now until April 30th they are offering savings and a FREE Big Eye Magnifier.

Free Big Eye Magnifier with Purchase of a  Stero-Zoom Microscope

Purchase a TKSZ-LV2-BE  Prolite Stereo-Zoom 4.5 Package with LED Ring Light and receive a  free Big Eye Magnifier automatically.

This Prolite TKSZ-LV2-BE ESD-Safe stereo-zoom microscope provides clear, crisp images, excellent focal depth and 3 dimensional viewing with a quick turn of the zoom knob. The prolite Stereo Zoom 4.5 series is the ultimate combination of quality, performance, and value:

3.5-45x magnification range standard

Excellent large 22mm eyepieces (with Eyeguards)

.5 Aux. lens included standard for increased working distance

Metal body for ESD safety

High output ESD safe LED Ring Illuminator

Save 20% on a Large 7″ x 5.75″ Dual-Mag DMLC Series Magnifier

Prolite® DMLC Dual-Mag Magnifier; 3 (1.75X) Diopter; EZ Swivel Arm; 7.0″ x 5.75″ Viewing Area

3 Diopter (1.75x) Optical Quality Lens – 7.0″ x 5.75″ Viewing Area

FREE 10 Diopter “Swing-A-Way” Lens Included

NEW 13 Watt DUAL Glare Free “Full Spectrum” Bulbs

Independent Bulb control with Vented Bulb Shields

OC White specials end April 30th

 

If you have any questions about any of these specials or any of the products featured in this blog you can contact Production Automation anytime:

Web: www.gotopac.com

Email: info@gotopac.com

Hakko Soldering Products Now Available at PAC

Production Automation is excited to announce we are now full distributors of Hakko Brand soldering equipment!

We have just finished work on our new section of Hakko Soldering, and invite you to come take a look at all the excellent products we have available.

Before March, we only offered the Hakko 936-12 soldering station but we can now offer all of the Hakko Soldering Stations, Desoldering Stations, Rework/Hot Air Stations, Direct Plug Soldering Irons, Solder Pots, Fume Extraction, Tips, and all Hakko Accessories!

And, for a limited time only Hakko is offering their “Silver Lining ‘09″ special to celebrate their 25th year in the industry!

Buy three, get one FREE on 25 different Hakko Brand products

To view all 25 Hakko products eligible click here:

Silver Lining 09

The details are simple, Purchase three (3) products (products must be the same part number) and receive a 4th product directly from Hakko for FREE. That’s a 25% savings!

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Fundamentals of Electrostatic Discharge, Part 6

Part 6: ESD Standards

2001, ESD Association, Rome NY

The electronics industry is continually shifting. Device density and technology is more complex. Electronics manufacturing is more heavily reliant on out-sourcing. The ESD industry seems to have jumped into this swirling eddy headfirst. ESD control programs have mushroomed. Black has been replaced by green, blue, and gold. Shielding bags dominate the warehouse. Ionizers exist along side wrist straps, and ground cords. An early history of “smoke and mirrors”, magic and lofty claims of performance is rapidly and safely being relegated to the past.

Today, more than ever, meeting the complex challenge of reducing ESD losses requires more than reliance on faith alone. Users require a way to legitimately evaluate and compare competing brands and types of products. They need objective confirmation that their ESD control program provides effective solutions to their unique ESD problems. Contract manufacturers and OEM’s require mutually agreed-upon ESD control programs that reduce duplication of process controls.

That’s where standards come into play. They provide guidance in developing programs that effectively address ESD process control. They help define the sensitivity of the products manufactured and used. They help define the performance requirements for various ESD control materials, instruments and tools. Standards are playing an ever-increasing role in reducing marketplace confusion in the manufacture, evaluation, and selection of ESD control products and programs.

The Who and Why of Standards

Who uses ESD Standards? Manufacturers and users of ESD sensitive devices and products, manufacturers and distributors of ESD control products, certification registrars, and third party testers of ESD control products.

Why use ESD Standards? They help assure consistency of ESD sensitive products and consistency of ESD control products and services. They provide a means of objective evaluation and comparison among competitive ESD control products. They help in developing, implementing, auditing, and certifying ESD control programs. And, they help reduce confusion in the marketplace.

In the United States, the use of standards in voluntary, although their use can be written into contracts or purchasing agreements between buyer and seller. In most of the rest of the world, the use of standards, where they exist, is compulsory.

Key Standards and Organizations

Just 20 years ago, there were relatively few reliable ESD standards and few ESD standards development organizations. Today’s ESD standards landscape is not only witnessing an increase int he number of standards, but also increasing cooperation among the organizations that develop them.

Today’s standards fall into three main groups. First, there are those that provide ESD program guidance or requirements. These include documents such as ANSI ESD S20.20-1999–Standard of the Development of an ESD Control Program, ANSI/ESD S8.1-ESD Awareness Symbols, or ESD TR20.20 ESD Handbook.

A second group covers requirements for specific products or procedures such as packaging or grounding. Typical standards in this group are ANSI/ESD S6.1- Grounding or ESD S11.11 for Shielding Bags.

A third group of documents covers the standardized test methods used to evaluate products and materials. Historically, the electronics industry relied heavily on test methods established for other industries or even other materials (e.g., ASTM-257-DC Resistance or Conductance of Insulating Materials). Today, however, specific test method standards focus on ESD in the electronics environment, largely as a result of the ESDAssociation’s activity. These include standards such as ESD S5.1- Device Testing, Human Body Model and ANSI/ESD S7.1: Floor Materials — Resistive Characterization to cite just a few.

Who Develops Standards?

Standards development and usage is a cooperative effort among all organizations and individuals affected by standards. There are several key ESD standards development organizations.

Military Standards

Traditionally, the U.S. Military spearheaded the development of specific standards and specifications with regard to ESD control in the U.S. today, however, U.S. Military agencies are taking a less proactive approach, relying on commercially developed standards rather than developing standards themselves. For example, the ESD Association completed the assignment from the Department of Defense to convert MIL-STD-1686into a commerical standard.

ESD Association

The ESD Association has been a focal point for the development of ESD standards in recent years. An ANSI-accredited standards development organization, the Association is charged with the development of ESD standards and test methods. The Association also represents the US on the International Electrotechnical Commission Technical Committee 101-Electrostatics.

The ESD Association has published 26 standards documents  and 9 technical reports. These voluntary standards cover the areas of material requirements, electrostatic sensitivity, and test methodology for evaluating ESD control materials and products. In addition to standards documents, the Association also publishes a number of informational advisories.

ESD Association Standards Classifications and Definitions

There are four types of ESD Association standards documents with specific clarity of definition. The four document categories are consistent with other standards development organizations. These four  categories are defined below.

Standard: A precise statement of a set of requirements to be satisfied by a material, product, system or process that also specifies the procedures for determining whether each of the requirements is satisfied.

Standard Test Method: A definitive procedure for the identification, measurement, and evaluation of one or more qualities, characteristics or properties of a material, product, system or process that yields a reproducible test result.

Standard Practice: A procedure for performing one or more operations or functions that may or may not yield a test result. Note: If a test result is obtained, it may not be reproducible between labs.

Technical Report: A collection of technical data or test results published as an informational reference on a specific material, product, system, or process.

As new documents are approved and issued, they will be designated into one of these four new categories. Existing documents are being reviewed and will be reclassified as appropriate.

International Standards

The international  community, led by the European-based International Electrotechnical Commission, has also climbed on board the standards express. Europe’s CENELEC has issued a European electrostatic standard EN100015- Protection of Electrostatic Sensitive Devices that was adopted as a European Norm. Additional work by the IEC too will result in a comprehensive series of standards that may someday be the successor to EN100015.

Japan also has released its proposed version of a national electrostatic Standard, which also shares the many aspects of the European and U.S. documents.

Organizational Cooperation

Perhaps one of the more intriguing changes in the ESD standards has been the organizational cooperation developing between various groups. One cooperative effort was between the ESD Association and the U.S. Department of Defense, which resulted in the Association preparing ANSI/ESD S20.20 as a successor to MIL-STD-1686.

Internationally, European standards development organizations and the ESD Association have developed working relationships that result in an expanded review of proposed documents, greater imput, and closer harmonization of standards that impact the international electronics community.

For users of ESD Standards, this increased cooperation will have a significant impact. First, we should see fewer conflicts between different standards. Finally, we should see less duplication of effort.

Summary

For the electronics community, the rapid propagation of ESD standards and continuing change in the standards environment mean greater availability of the technical references that will help improve ESD control programs. There will be recommendations to help set up effective programs. There will be test methods and specifications to help users of ESD control materials evaluate and select products that are applicable to their specific needs. And there will be guidelines for vendors of ESD products and materials to help them develop products that meet the real needs of their customers.

Principle ESD Standards

U.S. Military/Department of Defense

 MIL-STD-1686C: Electrostatic Discharge Control Program for Protection of Electrical and Electronic Parts, Assemblies and Equipment (Excluding Electrically Initiated Explosive Devices)

This military standard establishes requirements for ESD Control Programs. It applies to U.S. military agencies, contractors, subcontractors, suppliers and vendors. It requires the establishment, implementation and documentation of ESDcontrol programs for static sensitive devices, but does NOT mandate or preclude the use of any specific ESD control materials, products, or procedures. It is being updated and converted to a commerical standard by the ESD Association. Although DOD has accepted the new ANSI/ESD S20.20 document as a successor, it has not yet taken action to cancel SRD-1686.

MIL-HBDK-263B: Electrostatic Discharge Control Handbook for Protection of Electrical and Electronic Parts, Assemblies and Equipment (Excluding Electrically Initiated Explosive Devices)

This Document provides guidance, but NOT mandatory requirements, for the establishment and implementation of an electrostatic discharge control program in accordance with the requirements of MIL-STD-1686

MIL-PRF 87893-Workstation, Electrostatic Discharge (ESD) Control

This document defines requirements for ESD protective workstations

MIL-B-81705- Barrier Materials, Flexible, Electrostatic Protective, Heat Sealable

This document defines the requirements for ESD protective flexible packaging materials

MIL-STD-129-Marking for Shipment and Storage

Covers procedures for marketing and labeling ESD sensitive items

International/European

EN100015: Protection of Electrostatic Sensitive Devices

Adopted in 1992 and 1993, this European Norm covers ESD handling practices for electronic devices.

ESD Association

Standards Documents

ESD S1.1-1998: Evaluation, Acceptance, and Functional Testing of Wrist Straps

A successor to EOS/ESD S1.0, this document establishes test methods for evaluating the electrical and mechanical characteristics of wrist straps. It includes improved test methods and performance limits for evaluation, acceptance, and functional testing of wrist straps.

ESD STM2.1-1997: Resistance Test Method for Electrostatic Discharge Protective Garments

This Standard Test Method provides test methods for measuring the electrical resistance of garments used to control electrostatic discharge. It covers procedures for measuring sleeve-to-sleeve and point-to-point resistance.

ESD STM3.1-2000: Ionization

Test methods and procedures for evaluating and selecting air ionization equipment and systems are covered in this standard. The document establishes measurement techniques to determine ion balance and charge neutralization time for ionizers.

ESD SP3.3-2000: Periodic Verification of Air Ionizers

This Standard Practice provides test methods and procedures for periodic verification of the performance of air ionization equipment and systems (ionizers).

ESD S4.1-1997 (Revised): Worksurfaces- Resistance Measurements

This Standard establishes test methods for measuring the electrical resistance of worksurface materials used at workstations for protection of ESD susceptible items. It includes methods for evaluating and selecting materials, and testing new worksurface installations and previously installed worksurfaces.

ESD STM4.2-1998: Worksurfaces- Charge Dissipation Characteristics

This Standard Test Method provides a test method to measure the electrostatic charge dissipation characteristics of worksurfaces used for ESD control. The procedure is designed for use in a laboratory environment for qualification, evaluation or acceptance of worksurfaces.

ESD STM5.1-1998 Revised: Electrostatic Discharge Sensitivity Testing– Human Body Model

This Standard Test Method updates and revises an existing Standard. It establishes a procedure for testing, evaluating, and classifying the ESD sensitivity of components to the defined Human Body Model (HBM).

ESD STM5.2-1999 (Revised): Electrostatic Discharge Sensitivity Testing– Machine Model

This Standard establishes a test procedure for evaluating the ESD sensitivity of components to a defined Machine Model (MM). It also provides a system of classifying the sensitivity of these components. The component damage caused by the Machine Model is often similar to that caused by the Human Body Model, but it occurs at a significantly lower voltage.

ESD STM5.3-1999: Electrostatic Discharge Sensitivity Testing- Charged Device Model–Non-Socketed Mode

This Standard Test Method establishes a test method for evaluating the ESD sensitivity of active and passive components to a defines Charged Device Model (CDM).

ESD S6.1-1999: Grounding– Recommended Practice

This Standard recommends the parameters, procedures, and types of materials needed to establish an ESD grounding system for the protection of electronic hardware from ESD damage. This system is used for personnel grounding devices, worksurfaces, chairs, carts, floors, and other related equipment.

ANSI ESD S7.1-1994: Floor Materials– Resistive Characterization of Materials

Measurement of the electrical resistance of various floor materials such as floor coverings, mats, and floor finishes is covered in this document. It provides test methods for qualifying floor materials before installation or application and for evaluating and monitoring materials after installation or application.

ANSI ESD S8.1-1993: ESD Awareness Symbols

Three types of ESD awareness symbols are established by this document. The first one is to be used on a device or assembly to indicate that it is susceptible to electrostatic charge. The second is to be used on items and materials intended to provide electrostatic protection. The third symbol indicates the common point ground.

ESD S9.1-1995: Resistive Characterization of Footwear

This Standard defines a test method for measuring the electrical resistance of shoes used for ESD control in the electronics environment.

ESD SP10.1-2000: Automated Handling Equipment

This Standard Practice provides procedures for evaluating the electrostatic environment associated with automated handling equipment.

ANSI ESD 11.11-1993: Surface Resistance Measurement of Static Dissipative Planar Materials

This Standard Test Method provides test methods for measuring the volume resistance of static dissipative planar materials used in the packaging of ESD sensitive devices and components.

ANSI ESD S11.31-1994: Evaluating the Performance of Electrostatic Discharge Shielding Bags

This Standard provides a method for testing and determining the shielding capabilities of electrostatic shielding bags.

ESD STM12.1-1997: Seating- Resistive Characterization

This Standard provides test methods for measuring the electrical resistance of seating used to control ESD. The test method can be used for qualification testing as well as for evaluating and monitoring seating after installation. It covers all types of seating, including chairs and stools.

ESD STM13.1-2000: Electrical Soldering/Desoldering Hand Tools

This Standard Test Method provides electric soldering/desoldering hand tool test methods for measuring the electrical leakage and tip to ground reference point resistance and provides parameters for EOS safe soldering operation.

ANSI ESD S20.20-1999: Standard for the Development of an ESD Control Program

This Standard provides administrative, technical requirements and guidance for establishing, implementing and maintaining an ESD Control Program.

ESD STM97.1-1999: Floor Materials and Footwear- Resistance in Combination with a Person.

This Standard Test Method provides for measuring the electrostatic voltage on a person in combination with floor materials and footwear, as a system.

Advisory Documents 

Advisory Documents and Technical Reports are not Standards, but provide general information for the industry or additional information to aid in better understanding of Association Standards.

ESD ADV1.0-1994: Glossary of Terms

Definitions and explanations of various terms used in Association Standards and documents are covered in this advisory. It also includes other terms commonly used in the ESD industry.

ESD ADV3.2-1995: Selection and Acceptance of Air Ionizers

This Advisory document provides end users with guidelines for creating a performance specification for selecting air ionization systems. It reviews four types of air ionizers and discusses applications, test method references, and general design, performance and safety requirements.

ESD ADV11.2-1995: Triboelectric Charge Accumulation Testing

The complex phenomenon of triboelectric charging is discussed in this Advisory. it covers the theory and effects of tribocharging. It reviews procedures and problems associated with various test methods that are often used to evaluate triboelectrification characteristics. The test methods reviewed indicate gross levels of charge and polarity, but are not necessarily repeatable in real world situations.

ESD ADV53.1-1995: Triboelectric Charge Accumulation Testing

This Advisory document defines the minimum requirements for a basic ESD protective workstation used in ESD sensitive areas. It provides a test method for evaluating and monitoring workstations. It defines workstations as having the following components: support structure, static dissipative worksurface, a means of grounding personnel, and any attached shelving or drawers.

ESD TR20.20: ESD Handbook

New handbook provides detailed guidance for implementing an ESD control program in accordance with ANSI/ESD S20.20.

Sources of Standards

ESD Association, 7900 Turin Road, Building 3, Rome, NY 13440. Phone: 315-339-6937 Fax: 315-339-6793 Web: www.esda.org

HIS Global Engineering Documents, 15 Inverness Way East, Englewood CO 80112. Phone: 800-854-7179 Fax: 303-397-2740 Web: http://global.ihs.com

International Electrotechnical Commission, 3, Rue de Varembe, Case postale 131, 1211 Geneva 20, Switzerland. Fax: 41-22-919-0300 Web: http://www/iec.ch/

Military Standards, Navel Publications and Forms Center, 5801 Tabor Avenue, Philadelphia, PA 19120.

 

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Fundamentals of Electrostatic Discharge, Part 5

Part 5: Device Sensitivity and Testing

ESD Association, Rome NY

 In Part Twoof this series, we indicated that a key element in a successful static control program was the identification of those items (components, assemblies, and finished products) that are sensitive to ESD and the level of their sensitivity. Damage to an ESDS device by the ESD event is determined by the device’s ability to dissipate the energy of the discharge or withstand the current levels involved. This is known as device “ESD sensitivity” or “ESD susceptibility”.

Some devices may be more readily damaged by discharges occurring within automated equipment, while others may be more prone to damage from handling by personnel. In this article we will cove rthe models and test procedures used to characterize, determine, and classify the sensitivity of components to ESD. These test procedures are based on the three primary models of ESD events: Human Body Model (HBM), Machine Model (MM), and Charged Device Model (CDM). The models used to perform component testing cannot replicate the full spectrum of all possible ESD events. Nevertheless, these models have been proven to be successful in reproducing over 95% of all ESD field failure signatures. With the use of standardized  test procedures, the industry can:

• Develop and measure suitable on-chip protection
• Enable comparisons to be made between devices

• Provide a system of ESD sensitivity classification to assist in the ESD design and monitoring requirements of the manufacturing and assembly environments

• Have documented test procedures to ensure reliable and repeatable results

Human Body Model

One of the most common causes of electrostatic damage is the direct transfer of electrostatic charge through a significant series resistor from the human body or from a charged material to the electrostatic discharge sensitive (ESDS) device. When one walks across a floor, an electrostatic charge accumulates on the body. Simple contact of a finger to the leads of an ESDS device or assembly allows the body to discharge, possibly causing device damage. The model used to simulate this event is the Human Body Model (HBM).

The Human Body Model is the oldest and most commonly used model for classifying device sensitivity to ESD. The HBM testing model represents the discharge from the fingertip of a standing individual delivered to the device. It is modeled by a 100 pF capacitor discharged through a switching component and a 1.5kΩ series resistor into the component. This model, which dates from the nineteenth century, was developed for investigating explosions of gas mixtures in mines. It was adopted by the military in MIL-STD-883 Method 3015, and is also used in ESD Association standard ESD STM5.1: Electrostatic Discharge Sensitivity Testing– Human Body Model. A typical Human Body Model circuit is presented in Figure 1.

Testing for HBM sensitivity is typically performed using automated test systems. The device is placed in the test system and contacted through a relay matrix. ESD zaps are applied and the post stress I-V current traces are reviewed to see if the devices fail. The ESD Association HBM test standard was recently revised to include several technical changes. First, the number of zaps has been reduced from one second to 300 milliseconds. The changes reduce the HBM qualification test time.

The second technical change is a revision in the HBM tester specifications. The maximum rise time of an HBM wave form measured through a 500 ohm load was relaxed from 20 to 25 nanoseconds. This will allow HBM test equipment manufacturers to build high pin count testers that typically have a higher parasitic test board capacitance that slows down the 500 ohm wave form.

Machine Model

A discharge similar to the HBM event also can occur from a charged conductive object, such as a metallic tool or fixture. Originating in Japan as the result of trying to create a worse-case HBM event, the model is known as the Machine Model. This ESD model consists of a 200 pF capacitor discharged directly into a component with no series resistor.

As a worst-case human body model, the Machine Model may be over severe. However, there are real-world situations that this model represents, for example the rapid discharge from a charged board assembly or from the charged cables of an automatic tester.

Testing of devices for MM sensitivity using ESD Association standard ESD STM5.2: Electrostatic Discharge Sensitivity Testing–Machine Model is similar to HBM testing. The test equipment is the same, but the test head is slightly different. The MM version does not have a 1,500 ohm resistor, but otherwise the test board and the socket are the same as for HBM testing. The series inductance, as shown in Figure 2, is the dominating parasitic element that shapes the oscillating machine model wave form. The series inductance is indirectly defined through the specification of various waveform parameters.

Charged Device Model Testing

The transfer of charge froman ESDS device is also called an ESD event. A device may become charged, for example, from sliding down the feeder in an automated assembler. If it then contacts the insertion head or another conductive surface, a rapid discharge may occur from the device to the metal object. This event is known as the Charged Device Model (CDM) event and can be more destructive than the HBM for some devices. Although the duration of the discharge is very short–often less than one nanosecond– the peak current can reach several tens of amperes.

Several test methods have been explored to duplicate the real-world CDM event and provide a suitable test method that duplicates the types of failure that have been observed in CDM caused field failures. Current work in the area is concentrating on two separate CDM test methods. Once is termed CDM and best replicates the real world charged device event. The other addresses devices that are inserted in a socket and then charged and discharged in the socket. It is termed the Socketed Discharge Model (SDM). The device testing standard for CDM (ESD STM5.3.1: Electrostatic Discharge Sensitivity Testing- Charged Device Model)was published in 1999. The test procedure involves placing the device on a field plate with its leads pointing up, then charging it and discharging the device. Figure 3 illustrates a typical CDM test circuit.

SDM testing is similar to testing for HBM and MM sensitivity. The device is placed in a socket, charged from a high voltage source and then discharged. This procedure is still a work in progress and has had to overcome a number of limitations including too great a dependency on the specific design of the SDM tester. A technical report, ESD TR08-00: Socket Device Model (SDM) Testeris also available from the ESD Association.

Device Sensitivity Classification

Each of the device testing methods includes a classification system for defining the component sensitivity to the specified model (See Tables 1, 2, and 3). These classification systems have a number of advantages. They allow easy grouping and comparing of components according to their ESD sensitivity and the classification gives you an indication of the level of ESD protection that is required for the component.

A fully characterized component should be classified using all three models: Human Body Model, Machine Model, and Charged Device Model. For example, a fully characterized component may have the following: Class 1B (500 volts to <1000 volts HBM), Class M1 (<100 volts MM), and Class C3 (500 volts to <1000 volts CDM). This would alert a potential user of the component to the need for a controlled environment, whether assembly and manufacturing operations are performed by human beings or machines.

A word of caution, however. These classification systems and component sensitivity test results function as guides, not necessarily as absolutes. The events defined by the test data produce narrowly restrictive data that must be carefully considered and judiciously used. The three ESD models represent discrete points used in an attempt to characterize ESD vulnerability. The data points are informative and useful, but to arbitrarily extrapolate the data into a real world scenario can be misleading. The true utility of the data is in comparing one device with another and to provide a starting point for developing your ESD control programs.

Summary

Device failure models and device test methods define the sensitivity of the electronic devices and assemblies to be protected from the effects of ESD. With this key information, you can design more effective ESD control programs.

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Fundamentals of Electrostatic Discharge, Part Four

Part Four: Training and Auditing

ESD Association, Rome NY

Your static control program is up and running. How to you determine whether it is effective? How do you make sure your employees follow it? In Part Three, we suggested that there were at least nine critical elements to successfully developing and implementing an effective ESD control program. In Part Four, we will focus on two more of these elements: training and auditing.

Personnel Training

The procedures are in place. The materials are in use. But, your ESD control program just does not seem to yield the expected results. Failures declined initially, but they have begun reversing direction. Or perhaps there was little improvement at all. The solutions might not be apparent in inspection reports or incoming ESD materials. Nor in the wrist strap log in sheets. In large companies or small, it is hard to underestimate the role of training in an ESD program. The new ANSI/ESD S20.20 ESD Control Program standard cites training as a basic administrative requirement of an ESD control program. There is significant evidence to support the contribution of training to the success of the program. We would not send employees to the factory floor without the proper soldering skill or the knowledge to operate the automated insertion equipment. We should provide them with the same skill level regarding ESD control procedures.

Elements of Effective Training Programs

Although individual requirements cause training programs to vary from company to company, there are several  common threads that run through the successful programs.

1: Successful Training Programs Cover All Affected Employees

Obviously we train the line employees who test their wrist straps or place finished products in static protective packaging. But we also include department heads, upper management, and executive personnel in the process. Typically they are responsible for the day-to-day supervision and administration of the program or they provide leadership and support. Even subcontractors and suppliers should be considered for inclusion in the training program.

Because ESD control programs cover such a variety of job disciplines and educational levels, it may be necessary to develop special training modules of each organizational entity. For example, the modules developed for management, engineering, technicians, and field service could differ significantly because their day-to-day concerns and responsibilities are much different.

2: Effective Training is Comprehensive and Consistent

Training not only covers specific procedures, but also the physics of the problem and the benefits of the program as well. Consistent content across various groups, plants, and even countries (adjusted for cultural differences, of course) reduces confusion and helps assure conformance. The training content should include topics such as the fundamentals of ESD, the details of the organization’s ESD Control Program plan, and each person’s role in the plan.

3: Use a Variety of Training Tools and Techniques

Choose the methods that will work best for your organization. Combine live instruction with training videos or interactive CD-ROM programs. You may have in-house instructors available, or you may need to go outside the company to find instructors of training materials You can also integrate industry symposia, tutorials, and workshops into your program.

Effective training involves employees in the process. Reinforce the message with demonstrations of ESD events and their impact. Bulletin boards, newsletters, and posters provide additional reminders and reinforcement.

Maintaining a central repository for educational ESD control materials will help your employees keep current or answer questions that may occur outside the formal training sessions. Materials in such a repository might include:

• Material from initial and recurring training sessions
• ESD bulletins or newsletters
• Videos or CDs
• Computer based training materials
• Technical papers, studies, standards and specifications
• ESD Control materials and equipment product sheets

In addition, a knowledgeable person in the organization should be available to answer trainee questions once they have begun working.

4: Test, Certify, and Retrain

Your training should assure material retention and emphasize the importance of the effort. If properly implemented, testing and certification motivates and builds employee pride. Retraining or refresher training is an ongoing precess that reinforces, reminds, and provides opportunities for implementing new or improved procedures. Establish a system to highlight when employees are dure for retraining, retesting, or re-certification.

5: Feedback, Auditing, and Measurement

Motivate and provide the mechanism for program improvement. Sharing field or productivity data with employees demonstrates the effectiveness of the program and of their efforts. Tracking these same numbers can indicate that it’s time for retraining or whether modifications are required in the training program.

Design and delivery of an effective ESD training program can be just as important as the procedures and materials used in your ESD control program. A training program that is built on identifiable and measurable performance goals helps assure employee understanding, implementation and success.

Auditing

Developing and implementing an ESD control program itself is obvious. What might not be so obvious is the need to continually review, audit, analyze, feedback and improve. You will be asked to continually identify the program’s return on investment and to justify the savings realized. Technological changes will dictate improvements and modifications. Feedback to employees and top management is essential. Management commitment will need reinforcement.

Like training, regular auditing becomes a key factor in the successful management of ESD control programs. The mere presence of the auditing process spurs compliance with program procedures. It helps strengthen managements’ commitment. Audit reports trigger corrective action and help foster continuous improvement.

The benefits to be gained form regular auditing of our ESD control procedures are numerous.

• They allow us to prevent problems before they occur rather than always fighting fires.
• They allow us to readily identify problems and take corrective action.
• They identify areas in which our programs may be weak and provides us with information required for continuous improvement.
• They allow us to leverage limited resources effectively.
• They help us determine when our employees need to be retrained.
• They help us improve yields, productivity, and capacity.
• They help us bind our ESD programs together into a successful effort.

An ESD audit measures performance to the defined standards and procedures of the ESD Control Program. Typically, we think of an ESD audit as a periodic review and inspection of the ESD work area covering the use of the correct packing materials, wearing of wrist straps, following defined procedures, and similar items. Auditing can range from informal surveys of the processes and facilities to the more formal third-party audits for ISO 9000 or ANSI/ESD S20.20 certification.

Requirements for Effective Auditing

Regardless of the structure, effective ESD auditing revolves around several factors. First, auditing implies the existence of written and well-defined standards and procedures. It is difficult to measure performance if you do not have anything to measure against. Yet, you quite frequently hear an auditor ask, “Some people say you should measure less than 500 volts in an ESD protected area, but others say you should measure less than 100 volts. What’s acceptable when I audit the factory floor?” Obviously, this question indicates a lack of standards and the audit will be relatively ineffective.

Second, most audits require the taking of some measurements-  typically resistance and the presence of charge or fields. Therefore, you will need specific instrumentation to conduct work area audits. As a minimum, you will need an electrostatic field meter, a wide range resistance meter, a ground/circuit tester, and appropriate electrodes and accessories. Although this equipment must be accurate, it need not be as sophisticated as laboratory instruments. The audit is intended to verify basic functions and not as a full qualification of ESD control equipment or materials. You want the right tool for the job. Remember, many of the instruments you might choose for auditing are good indicators, but not suitable for precise evaluation of materials. Be sure that you can correlate the values obtained with those in the laboratory.

Third, our audits need to include all areas in which ESD control is requiredto protect electrostatic discharge sensitive devices. Typically these areas would include receiving, inspection, stores and warehouses, assembly, test and inspection, research and development, packaging, field service repair, offices and labratories, and clean rooms. Similarly, we need to audit all of the various processes, materials, and procedures that are used in our ESD control programs- personnel, equipment, wrist straps, floors, clothing, worksurfaces, training, and grounding.

Fourth, we need to audit frequently and regularly. The actual frequency of audits depends upon your facility and the ESD problems that you have. Following initial audit, some experts recommend auditing each department once a month if possible and probably a minimum of six times per year. If this seems like a high frequency level, remember that these regular audits are based upon a sampling or work areas in each department, not necessarily every workstation. Once you have gotten your program underway, your frequency of audit will be based on your experience. If your audits regularly show acceptable levels of conformance and performance, you can reduce the frequency of auditing. If, on the other hand your audits regularly uncover continuing problems, you may need to increase the frequency.

Fifth, upon completion of the audit, it is essential to implement corrective actionif deficiencies are discovered. Trends need to be tracked and analyzed to help establish corrective action, which may include retraining of personnel, revision of requirement documents or processes, or modification of the existing facility.

Types of Audits

There are several types of ESD audits: program management audits, quality process checking, and work placeaudits. Each type is distinctively different and each is vitally importantly to the success of the ESD program.

Program managementaudits measure how well a program is managed and how strong management commitment is. The program management audit emphasizes factors such as the existence of an effective implementation plan, realistic program requirements, ESD training programs, regular audits, and other critical factors of program management. The program management audit typically is conducted by a survey specifically tailored to the factors being reviewed. Because it’s a survey, the audit can be conducted without actually visiting the site. The results of this audit indirectly measure work place compliance and are particularly effective as a means of self-assessment for small companies as well as large global corporations.

Quality processchecking applies classical statistical quality control procedures to the ESD process and is performed by operations personnel. This is not a periodic audit, but rather daily maintenance of the program. Visual and electrical checks of the procedures and materials, wrist strap testing for example, are used to monitor the quality of the ESD control process. Checking is done on a daily, weekly, or monthly basis.

Trend charts and detailed records trigger process adjustments and corrective action. They help assure that specified procedures are followed on a regular basis. The records are essential of quality control purposes, corrective action and compliance with ISO-9000.

Work placeaudits verify that program procedures are followed and that ESD control materials and equipment are within specification or are functioning properly. Audits are performed on a regular basis, often monthly, and utilize sampling techniques and statistical analysis of the results. The use of detailed checklists and a single auditor assures that all items are covered and that the audits are performed consistently over time.

Basic Auditing Instrumentation

Special instrumentation will be required to conduct work area audits. The specific instrumentation will depend on what you are trying to measure, the precision you require and the sophistication of your static control and material evaluation program. However, as a minimum, you will need an electrostatic field meter, a wide range resistance meter, a ground/circuit tester, and appropriate electrodes and accessories. Additional instrumentation might include a charge plate monitor, footwear and wrist strap testers, chart recorders and timing devices, discharge simulators, and ESD events detectors.

Although this equipment must be accurate, it need not be as sophisticated as laboratory instruments. The audit is intended to verify basic functions and not as a full qualification of ESD control equipment or materials. Remember, you want the right tool for the job. Just as you would not buy a hammer if you were planning to saw wood, you would not purchase an electrometer to measure static voltages on a production line. If you are making measurements according to specific standards, be sure the instrumentation meets the specifications of these standards.

With a hand held electrostatic field meter, you can measure the presence of electrostatic charge in your environment allowing you to identify problem areas and monitor your ESD control program. These instruments measure the electrostatic field associated with a charged object. Many field meters simply measure the gross level of the electrostatic field and should be used as general indicators of the presence of a charge and the approximate level of this charge. Others will provide more precise measurement for material evaluation and comparison.

For greater precision in facility measurements of for laboratory evaluation, a charge plate monitorcan be attached to some field meters or connected to a voltmeter in the laboratory. With these additional tools you can evaluate the performance of flooring materials or balance ionizing equipment, for example.

Because resistance is one of the key factors in evaluating ESD control materials, a wide range resistance meter becomes a crucial instrument. Most resistance measurements are made at 100 volt, and some at 10 volts. The equipment you choose should be capable of measuring resistance ranges of 10^5 to 10^11 ohms. With the proper electrodes and cables, you will be able to measure the resistance of flooring materials, worksurfaces, equipment, furniture, garments, and some packaging materials.

The final instrument is a ground/circuit tester. With this device you can measure the continuity of your ESD grounds and also check the impedance as well as neutral to ground shorts.

Areas, Processes, and Materials to be Audited

In our last column we stated that ESD protection was required “wherever ESDS devices are handled”. Obviously, our audits need to include these same areas. Table 1 indicates some of the physical areas that require ESD protection and auditing of the program.

Similarly, we need to conduct work area and program management audits of all the various processes, materials, and procedures that are used in our ESD control programs. Some of these are shown in table 2.

Check Lists

Check lists can be helpful tools for conducting work place and program audits. However, it is important that ESD control program requirements are well documented and accessible to avoid a tendency for check lists becoming de facto lists of requirements. Table 3 indicates the type of questions and information that might be included in an auditing check list. Your own check lists, of course, will be based on your specific needs and program requirements. They should conform to your actual ESD control procedures and specifications and they should be consistent with any ISO 9000 requirements you may have.

In addition to check lists, you will use various forms for recording the measurements you make: resistance, voltage generation, ect. Part of your audit will also include the daily logs on the factory floor such as those used for wrist strap checking.

Reporting and Corrective Action

Upon completion of the auditing process, Reports should be prepared and distributed in a timely manner. Details of the audits need to be fully documented for ISO-9000 or ANSI/ESD S20.20 certification. As with all audits, it is essential to implement corrective action if deficiencies are discovered. Trends need to be tracked and analyzed to help establish corrective action, which may include retraining of personnel, revision of requirement documents or processes, or modification of the existing facility.

Conclusion

Auditing and training are the key elements in maintaining an effective ESD control program. They help assure that procedures are properly implemented and can provide a management tool to gauge program effectiveness and make continuous improvement.

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Fundamentals of Electrostatic Discharge, Part 3

Part Three: Basic ESD Control Procedures and Materials

ESD Association, Rome NY

In Part Two, Principles of ESD Control we introduced four principles of static control and nine key elements of ESD program development and implementation. In Part Three, we will cover some of the primary specific static control procedures and materials that become part of your program. First, a quick review.

Basic Principles of Static Control

We suggested focused on just six basic principles in the development and implementation of effective ESD control programs.

Design in immunityby designing products and assemblies to be as immune as reasonable from the effects of ESD.

Define the level of control needed in your environment.

Identify and define the electrostatic protected areas (EPA), the areas in which you will be handling sensitive parts.

Eliminate and reduce generation by reducing and eliminating static generating processes, keeping processes and materials at the same electrostatic potential, and by providing appropriate ground paths to reduce charge generation and accumulation.

Dissipate and neutralize by grounding, ionization, and the use of conductive and dissipative static control materials.

Protect products from ESD with proper grounding or shunting and the use of static control packaging and materials handling products.

At the facility level our static control efforts concentrate on the last five principles. In this post we will concentrate on the primary materials and procedures that eliminate and reduce generation, dissipate and neutralize charges, or protect sensitive products from ESD.

Identifying the Problem Areas and the Level of Control

One of the first questions we need to answer is “How sensitive are the parts and assemblies we are manufacturing or handling?” This information will guide you in determining the various procedures and materials required to control ESD in your environment.

How do you determine the sensitivity of your parts and assemblies or where can you get information about their ESD sensitivity? A first source would be the manufacturer or supplier of the component itself. An additional source is ITT Research Institute/Reliability Analysis Center in Rome, New York, which publishes ESD susceptibility data for 22,000 devices, including microcircuits. You may find that you need to have your specific parts tested for ESD sensitivity. We will discuss device sensitivity testing in Part Five of this series.

The second question you need to answer is “Which areas of our facility need ESD protection?” This will allow you to define your specific electrostatic protected areas (EPAs), the areas in which you will be handling sensitive parts and the areas in which you will need to bond of electrically connect all conductive and dissipative materials, including personnel, to a know ground. Often you will find that there are more areas that require protection than you originally thought, usually wherever ESDS devices are handled. Typical areas requiring ESD protection are shown in table 1.

Grounding

Throughout our discussion, we will see how important grounding is to effective ESD control. Effective ESD grounds are of critical importance in any operation, and ESD grounding should be clearly defined and regularly evaluated.

A primary means of protecting of ESD susceptible (ESDS) items is to provide a ground path to bring ESD protective materials and personnel to the same electrical potential. All conductors in the environment, including personnel, must be bonded or electrically connected and attached to a known ground or contrived ground, creating an equipotential balance between all items and personnel. Electrostatic protection can be maintained at a potential above a “zero” voltage ground reference as long as all items in the system are at the same potential. It is important to note that non-conductors in an Electrostatic Protected Area (EPA) cannot lose their electrostatic charge by attachment to ground.

ESD Association Standard ANSI EOS/ESD 6.1- Grounding Recommends two-step procedure for grounding ESD protective equipment.

The first step is to ground all components of the work area (worksurfaces, people, equipment, ect.) to the same electrical ground point called the “common point ground”. This common point ground is defined as a “system or method for connecting two or more grounding conductors to the same electrical potential”

This ESD common point ground should be properly identified. ESD Association standard EOS/ESD S8.1-1993 recommends the use of the symbol in Figure 1 to identify the common point ground.

The second step is to connect the common point ground to the equipment ground or the third wire (green) electrical ground connection. This is the preferred ground connection because all electrical equipment at the workstation is already connected to this ground. Connecting the ESD control materials or  equipment to the equipment ground brings all components of the workstation to the same electrical potential. If a soldering iron used to repair an ESDS item were connected to the electrical ground and the surface containing the ESDS item were connected to an auxiliary ground, a difference in electrical potential could exist between the iron and the ESDS item. This difference in potential could cause damage to the item.

Any auxillary grounds (water pipe, building frame, ground stake) present and used at the workstation must be bonded to the equipment ground to minimize the differences in potential between the two grounds.

Detailed information on ESD grounding can be found in ESD Association standard ESD-S6.1, Grounding-Recommended Practices.

Controlling Static on Personnel and Moving Equipment

In many facilities, people are one of the prime generators of static electricity. The simple act of walking around or repairing a board can generate several thousand volts on the human body. If not properly controlled, this static charge can easily discharge into a static sensitive device- a human body model (HBM) discharge.

Even in highly automated assembly and test processes, people still handle static sensitive devices…in the warehouse, in repair, in the lab, in transport. For this reason, static control programs place considerable emphasis on controlling personnel generated electrostatic discharge. Similarly, the movement of carts and other wheeled equipment through the facility also can generate static charges that can transfer to the products being transported on this equipment.

Wrist Straps

Typically, wrist straps are the primary means of controlling static charge on personnel. When properly worn and connected to ground, a wrist strap keeps the person wearing it near ground potential. Because the person and other grounded objects in the work area are at or near the same potential, there can be no hazardous discharge between them. In addition, static charges are safely dissipated from the person to ground and do not accumulate.

Wrist straps have two major components, the cuff that goes around the person’s wrist and the ground cord that connects the cuff to the common point ground. Most wrist straps have a current limiting resistor molded into the ground cord head in the end that connects to the cuff. The resistor most commonly used is a one megaohm, 1/4 watt with a working voltage rating of 250 volts. Wrist straps should be tested on a regular basis. Daily testing or continuous monitoring is recommended.

Floors, Floor Mats, Floor Finishes

A second method of controlling electrostatic charge on personnel is with the use of ESD protective floors in conjunction with ESD control footwear or foot straps. This combination of floor materials and footwear provides a ground path for the dissipation of electrostatic charge, thus reducing the charge accumulation on personnel and other objects to safe levels. In addition to dissipating charge, some floor materials (and floor finishes) also reduce triboelectric charging. The use of floor materials is especially appropriate in those areas where increased personnel mobility is necessary. In addition, floor materials can minimize charge accumulation on chairs, carts, lift trucks and other objects that move across the floor. However, those items require dissipative or conductive casters or wheels to make electrical contact with the floor. When used as the primary personnel grounding system, the resistance to ground including the person, footwear and floor must be the same as specified for wrist straps (<35 x 10E6 ohms) of the voltage accumulation on a person must be less than 100 volts.

Shoes, Grounders, Casters

Used in combination with ESD protective floor materials, static control shoes, grounders, casters and wheels provide the necessary electrical contact between the person or object and the floor material. Insulative footwear, casters, or wheels prevent static charges from flowing from the body to the floor to ground.

Clothing

Clothing is a consideration in some ESD protective areas, especially in clean rooms and very dry environments. Clothes materials can generate electrostatic charges that may discharge into sensitive components or they may create electrostatic fields that may induce charges on the human body. Because clothing usually is electrically insulated or isolated from the body, charges on clothing fabrics are not necessarily dissipated to the skin then to ground. Grounded static control garments are intended to minimize the effects of electrostatic fields or charges that may be present on a person’s clothing.

Workstations and Worksurfaces

 An ESD Protective workstation refers to the work area of a single individual that is constructed and equipped with materials and equipment to limit damage to ESD sensitive items. It may be a stand-alone station in a stockroom, warehouse, or assembly area, or in a field location such as a computer bay  in a commercial aircraft.

A workstation also may be located in a controlled area such as a clean room. They key ESD control elements comprising most workstations are a static dissipative worksurface, a means of grounding personnel (usually a wrist strap), a common grounding connection, and appropriate signage and labeling. A typical workstation is shown in Figure Two.

The workstation provides a means for connecting all worksurfaces, fixtures, handling equipment, and grounding devices to a common point ground. In addition, there may be provision for connecting additional personal grounding devices, equipment, and accessories such as constant ground monitors and ionizers.

Static protective worksurfaces with a resistance to ground of 10^6 to 10^9 provide a surface hat is at the same electrical potential  as other ESD protective items in the workstation. They also provide an electrical path to ground for the controlled dissipation of any static potentials on materials that contact the surface. The worksurface also helps define a specific work area in which ESD sensitive devices may be safely handled. The worksurface is connected to the common point ground.

Production Equipment and Production Aids

Although personnel generated static is usually the primary ESD culprit in many environments, automated manufacturing and test equipment also can pose an ESD problem. For example, a device may become charged from sliding down a feeder. If the device then contacts the insertion head or another conductive surface, a rapid discharge occurs from the device to the metal object–a Charged Device Model (CDM) event. In addition, various production aids suh as hand tools, tapes, or solvents also become ESD concerns.

Grounding is the primary means of controlling static charge on equipment and many production aids. Much electrical equipment is required by the National Electrical Code to be connected to the equipment ground (the green wire) in order to carry fault currents. This ground connection also will function of ESD purposes. All electrical tools and equipment used to process ESD sensitive hardware require the 3 prong grounded type AC plug. Hand tools that are not electrically powered, i.e., pliers, wire cutters, and tweezers, are usually grounded through the ESD worksurface and the (grounded) person using the conductive tools. Holding fixtures should be made of conductive or static dissipative materials when possible. A separate ground wire may be required for conductive fixtures not sitting on an ESD worksurface or handled by a grounded person. For those items that are composed of insulative materials, the use of ionization or application of topical antistats may be required to control generation and accumulation of static charges.

Packaging and Handling

Direct protection of ESDS devices from electrostatic discharge is provided by packaging materials such as bags, corrugated, and rigid or semi-rigid packages. The primary use of these items is to protect the product when it leaves the facility, usually when shipped to the customer. In addition, materials handling products such as tote boxes and other containers primarily provide protection during inter or intra facility transport.

The main ESD function of these packaging and materials handling products is to limit the possible impact of ESD from triboelectric charge generation, direct discharge, and electrostatic fields. The initial consideration is to have low charging materials in contact with ESD sensitive items. For example, the low charging property would control triboelectric charge resulting from sliding a board or component into the package or container. A second requirement is the the material provides protection from direct electrostatic discharge as well as shield from electrostatic fields.

Many materials are available that provide all three benefits: low charging, discharge protection, and electric field suppression. The inside of these packing materials have a low charging layer, but also have an outer layer with a surface resistance generally in the dissipative range.

Resistance or resistivity measurements help define the material’s ability to provide electrostatic shielding or charge dissipation. Electrostatic shielding attenuates electrostatic fields on the surface of a package in order to prevent a difference in electrical potential fro existing inside the package. Electrostatic shielding is provided by materials that have a surface resistance equal to or less than 1.0 x 10^3 when tested according to EOS/ESD-S11.11 or a volume resistivity of equal to or less than 1.0 x 10^3 ohms-cm when tested according to the methods of EIA 541. In addition, shielding may be provided by packaging materials that provide an air gap between the package and the product. Dissipative materials provide charge dissipation characteristics. These materials have a surface resistance greater than 1.0 x 10^4 then less than or equal to 1.0 x 10^11 when tested according to EOS/ESD-S11.11 or a volume resistivity greater than 1.0 x 10^5 but less than or equal to 1.0 x 10^12 ohm-cm when tested according to the  methods of EIA 541.

Ionization

However, most static control programs also deal with isolated conductors that cannot be grounded, insulating materials (e.g., most common plastics). Topical antistats often are used to dissipate static charges from these items under some circumstances.

More frequently, however, air ionization can neutralize the static charge on insualted and isolated objects by charging the molecules of the gases of the surrounding air. Whatever static charge is present on objects in the work environment will be neutralized by attracting opposite polarity charges from the air. Because it uses only the air that is already present in the work environment, air ionization may be employed even in clean rooms where chemical sprays and some static dissipative materials are not usable.

Air ionization is one component of a complete static control program, not necessarily a substitute for grounding or other methods. Ionizers are used when it is not possible to properly ground everything and as backup to other static control methods. In clean rooms, air ionization may be one of the few methods of static control available.

Cleanrooms

while the basic methods of static control discussed here are applicable in most environments, cleanroom manufacturing processes require special considerations.

Many objects integral to the semiconductor manufacturing process (quartz, glass, plastic, and ceramic) are inherently charge generating. Because these materials are insulators, this charge cannot be removed easily by grounding. Many static control materials contain carbon particles or surfactant additives that sometimes restrict their use in clean rooms. The need for personnel mobility and the use of clean room garments often make the use of wrist straps difficult. In these circumstances, ionization and flooring/fottwear systems become key weapons against static charge.

Identification

A final element in our static control program is the use of appropriate symbols to identify static sensitive devices and assemblies, as well as products intended to control ESD. The two most widely accepted symbols for identifying  ESDS parts or ESD control materials are defined in the ESD Association Standard ANSI ESD S8.1-1993 – ESD Awareness Symbols.

The ESD Susceptibility Symbol (figure 3) consists of a triangle, a reaching hand, and a slash through the reaching hand. The triangle means “caution” and the slash through the hand means “don’t touch”. Because of its broad usage, the hand in the triangle has become associated with ESD and the symbol literally translates to “ESD sensitive stuff, don’t touch.”

The ESD Susceptibility Symbol is applied directly to integrated circuits, boards, and assemblies that are static sensitive. It indicated that handling or use of this item might result in damage from ESD if proper precautions are not taken. If desired, the sensitivity level of the item may be added to the label.

The ESD Protective Symbol (figure 4) consists of the reaching hand in the triangle. An arc around the triangle replaces the slash. This “umbrella” means protection. The symbol indicates ESD protective material. It is applied to mats, chairs, wrist straps, garments, packaging, and other items that provide ESD protection. It may also be used on equipment such as hand tools, conveyor belts, or automated handlers that is especially designed or modified to provide ESD control.

Neither symbol is applied on ESD test equipment, footwear checkers, wrist strap testers, resistance or resistivity meters or similar items that are used for ESD purposes, but which do not provide actual protection.

Summary

Effective static control programs require a variety of procedures and materials. In this column, we have provided a brief overview of the most commonly used elements of a program. Additional in-depth discussion of individual materials and procedures can be found in publications such as the ESD Handbook published by the ESD Association.

Your program is up and running. How do you determine whether it is effective? How do you make sure your employees follow it? In Part Four we will cover the topics of Auditing and Training.

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Fundamentals of Electrostatic Discharge, Part 2

Part Two: Principles of ESD Control

ESD Association, Rome NY

 

In Part One of this series, Introduction to Electrostatic Discharge, we discussed the basics of electrostatic charge, discharge, types of failures, ESD events, and device sensitivity. We concluded our discussion with the following summary:

 

1. Virtually all materials, even conductors, can be triboelectrically charged.

 

2. The   charge is affected by material type, speed of contact and separation, humidity, and several other factors.

 

3. Electrostatic fields are associated with charged objects.

 

4. Electrostatic discharge can damages devices so they fail immediately, or ESD may result in latent damage that may escape immediate attention, but cause the device to fail prematurely once in service.

 

5. Electrostatic discharge can occur throughout the manufacturing, test, shipping, handling, or operational processes.

 

6. Component damage can occur as the result of a discharge to the device, from the device, or from charge transfers resulting from electrostatic fields. Devices vary significantly in their sensitivity to ESD.

 

Understanding these key concepts is crucial to protecting your products from the effects of static damage. Armed with this information, you can then begin to develop an effective ESD control program. In Part Two we will focus on some basic concepts of ESD control.

 

Basic Principles of Static Control

Sometimes, controlling electrostatic discharge (ESD) in the electronics environment seems to be a formidable challenge. However, the task of designing and implementing ESD control programs becomes less complex if we focus on just basic principles of control. In doing so, we also need to keep in mind the ESD corollary to Murphy’s law, “No matter what we do, static charge will try to find a way to discharge.”

 

1. Design in Immunity

The first principle is to design products and assemblies to be as immune as reasonable from the effects of ESD. This involves such steps as using less static sensitive devices or providing appropriate input protection devices, assemblies, and equipment. For engineers and designers, the paradox is that advancing product technology requires smaller and more complex geometries that often are more susceptible to ESD.

 

2. Define the Level of Control Needed in Your Environment

What is the sensitivity level of the parts you are using and the products that you are manufacturing and shipping? ANSI/ESD 20.20 defines a control program for items that are sensitive to 100 volts Human Body Model (HBM). Your environment may be different.

 

3. Identify and Define the Electrostatic Protected Areas (EPA)

These are the areas in which you will be handling sensitive parts and the areas in which you will need to bond or electrically connect all conductive and dissipative materials, including personnel, to a known ground.

 

4. Eliminate and Reduce Generation

Obviously, product design isn’t the whole answer. The fourth Principle of control is to eliminate or reduce the generation and accumulation of electrostatic charge in the first place. It’s fairly basic: no charge = no discharge. We begin by reducing as many static generating processes or materials, such as the contact and separation of dissimilar materials and common plastics, as possible from the work environment. We keep other processes and materials at the same electrostatic potential. Electrostatic discharge does not occur between materials kept at the same potential or at zero potential. We provide ground paths, such as wrist straps, flooring and work surfaces, to reduce charge generation and accumulation.

 

5. Dissipate and Neutralize

Because we simply can’t eliminate all generation of static in the environment, our fifth Principle is to safely dissipate or neutralize those electrostatic charges that do occur. Proper grounding and the use of conductive or dissipative materials play major roles. For example, workers who “carry” a charge into the work environment can rid themselves of that charge when they attach a wrist strap or when they step on an ESD floor mat while wearing ESD control footwear. The charge goes to ground rather than being discharged into a sensitive part. To prevent damaging a charged device, the rate of discharge can be controlled with static dissipative materials.

 

For some objects, such as common plastics and other insulators, grounding does not remove an electrostatic charge because there is no conductive pathway. Typically, ionization is used to neutralize charges on these insulating materials. The ionization process generates negative and positive ions that are attracted to the surface of a charged object, thereby effectively neutralizing the charge.

 

6. Protect Products

Our final ESD control Principle is to prevent discharges that do occur from reaching susceptible parts and assemblies. One way is to provide our parts and assemblies with proper grounding or shunting that will “dissipate” any discharge away from the product. A second method is to package and transport susceptible devices in proper packaging and materials handling products. These materials may effectively shield the product from charge, as well as reduce the generation of charge by a movement of product within the container.

 

Elements of an Effective ESD Control Program

While these six principles may seem rather basic, they can guide us in the selection of appropriate materials and procedures to use in effectively controlling ESD. In most circumstances, effective programs will involve all of these principles. No single procedure or product will do the whole job; rather effective static control requires a full ESD control program. How do we develop and maintain a program that puts these basic principles into practice? How do we start? What is the process? What do we do first? Ask a dozen experts and you may get a dozen different answers. But, if you dig a little deeper, you will find that most of the answers center on similar key elements. You will also find that starting and maintaining an ESD control program is similar to many other business activities and projects. Although each company is unique in terms of its ESD control needs, there are at least six critical elements to successfully developing and implementing an effective ESD control program

 

1. Establish an ESD Coordinator and ESD Teams

As the problem-solving style of the decade, the team approach particularly applies to ESD because the problems and the solutions cross various functions, departments, divisions, and even suppliers in most companies. Team composition includes line employees as well as department heads or other management personnel. ESD teams or committees help assure a variety of viewpoints, the availability of the needed expertise, and commitment to success. An active ESD committee helps unify the effort and brings additional expertise to the project. Committee or team membership should include representation from areas such as engineering, manufacturing, field service, training, and quality.

 

Heading this team effort is an ESD Program Coordinator. Ideally this responsibility should be a full-time job. However, we seldom operate in an ideal environment and you may have to settle for the function to be a major responsibility of an individual. The ESD coordinator is responsible for developing, budgeting, and administering the program. The coordinator also serves as the company’s internal ESD consultant to all areas.

 

2. Assess Your Organization, Facility, Processes and Losses

Your next step is to gain a thorough understanding of your environment and its impact on ESD. Armed with your loss and sensitivity data, you can evaluate your facility, looking for areas and procedures that may be contributing to your defined ESD problems. Be on the lookout for things such as static generating materials and personnel handling procedures for ESD-sensitive items.

 

Document your processes. Observe the movement of people and materials through the areas. Note those areas that would appear to have the greatest potential for ESD problems. Remember, that ESD can occur in the warehouse just as it can in the assembly areas. Then conduct a thorough facility survey or audit. Measure personnel, equipment, and materials to identify the presence of electrostatic fields in your environment.

 

Before seeking solutions to your problems, you will need to determine the extent of your losses to ESD. These losses may be reflected in receiving reports, QA and QC records, customer returns, in-plant yields, failure analysis reports, and other data that you may already have or that you need to gather. This information not only identifies the magnitude of the problem, but also helps pinpoint and prioritize areas that need attention.

 

Document your actual and potential ESD losses in terms of DOA components, rework, customer returns, and failures during final test and inspection. Use data from outside sources or the results of your pilot program for additional support. Develop estimates of the savings to be realized from implementing an ESD control program.

 

You will also want to identify those items (components, assemblies, and finished products) that are sensitive to ESD and the level of their sensitivity. You can test these items yourself, use data from suppliers, or rely on published data for similar items.

 

3. Establish and Document Your ESD Control Program Plan

After completing your assessment, you can begin to develop and document your ESD control program plan. The plan should cover the scope of the program and include tasks, activities, and procedures necessary to protect the ESD sensitive items at or above the ESD sensitivity level chosen for the plan. Prepare and distribute written procedures and specifications so that everyone has a clear understanding of what is to be done. Fully documented procedures will help you meet administrative and technical elements of ANSI ESD S20.20, and help you with ISO 9000 as well.

 

4. Build Justification to Get the Management Support Top Management

To be successful, an ESD program requires the support of your top management, at the highest level possible. What level of commitment is required? To obtain commitment, you will need to build justification for the plan. You will need to emphasize quality and reliability, the cost of ESD damage, the impact of ESD on customer service and product performance. You may even need to conduct a pilot program if the experience of other companies is not sufficient to help prove your point.

 

Prepare a short corporate policy statement on ESD control. Have top management co-sign it with the ESD coordinator. Periodically, reaffirm the policy statement and management’s commitment to it.

 

5. Define a Training Plan

Train and retrain your personnel in ESD and your company’s ESD control program and procedures. Proper training for line personnel is especially important. They are often the ones who have to live with the procedures on a day-to-day basis. A sustained commitment and mindset among all the employees that ESD prevention is a valuable, on-going effort by everyone is one of the primary goals of training.

 

6. Develop and Implement a Compliance Verification Plan

Developing and implementing the program itself is obvious. What might nit be so obvious is the need to continually review, audit, analyze, feedback, and improve. Auditing is essential to ensure that the ESD control program is successful. You will be asked to continually identify the return on investment of the program and to justify the savings realized. Technological changes will dictate improvements and modifications. Feedback to employees and top management is essential. Management commitment will need reinforcement.

 

Include both reporting and feedback to management, the ESD team, and other employees as part of your plan. Management will want to know that their investment in time and money is yielding a return in terms of quality, reliability, and profits. Team members need a pat on the back for a job well done. Other employees will want to know that the procedures you have asked them to follow are indeed worthwhile.

 

Conduct periodic evaluations of your program and audits of your facility. You will find out if your program is successful and is giving the expected return. You will spot weaknesses in the program and shore them up. You will discover whether the procedures are being followed.

 

As you find areas that need work, be sure to make the necessary adjustments to keep the program on track.

 

Conclusion

Six principles of static control and six key elements to program development and implementation: your guide posts for effective ESD control programs. In Part Three, we’ll take a closer look at the specific and materials the become of part of your program.

 

 

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