Category Archives: ESD Information

Remember the time when Steve Wozniak taught us about ESD?

In 1985 Apple produced a service video that explained the importance of ESD control when servicing an Apple II. Steve Wozniak, a co-founder of Apple computers, was featured in the 26 minute video explaining the handling of ESD susceptible devices.  Other than the fact that ESD components are smaller and more sensitive than ever (see the ESDA Electrostatic Discharge (ESD) Technology Roadmap – Revised May 2016), the same principles laid out in the 1985 video hold true today.  Take a step back in time:

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What is a Faraday Cage?

lightning-659917_960_720[1]A Faraday cage or Faraday shield is an enclosure formed by conducting material or by a mesh of such material. Such an enclosure blocks external static and non-static electric fields. Faraday cages are named after the English scientist Michael Faraday, who invented them in 1836. An impressive demonstration of the Faraday cage effect is that of an aircraft being struck by lightning. This happens frequently, but does not harm the plane or passengers. The metal body of the aircraft protects the interior. For the same reason, a car may be a safe place to be in a thunderstorm.

37150CircuitBoard

Protektive Pak Impregnated Corrugated Box with lid

ESD control products that provide a Faraday Cage or shielding include Statshield® Metal-In and Metal-Out Shielding Bags, Protektive Pak™ impregnated corrugated with shielding layer when using a lid, and Conductive Totes. Statshield® ESD Smocks creates a Faraday Cage effect around the torso and arms of the operator and shields charges from the operator’s clothing from damaging ESD sensitive devices. (Technically, suppressing the electrical field from clothing worn underneath).

 

 

There are standard tests measuring the energy penetration of electrostatic discharges to the interior. The Shielding test method per Packaging standard ANSI/ESD S541 is ANSI/ESD STM11.31 and the required limit is less than 50 nanoJoules of energy.

ESD shielding packaging is to be used particularly when transporting or storing ESD sensitive items outside an ESD Protected Area. Per Packaging standard ANSI/ESD S541 section 6.2 Outside an EPA “Transportation of sensitive products outside of an EPA shall require packaging that provides:

  1. Low charge generation.
  2. Dissipative or conductive materials for intimate contact.
  3. A structure that provides electrostatic discharge shielding.”

Definitions from the ESD Association Glossary ESD ADV1.0 include: Faraday cage “A conductive enclosure that attenuates a stationary electrostatic field.”

Electrostatic discharge (ESD) shield “A barrier or enclosure that limits the passage of current and attenuates an electromagnetic field resulting from an electrostatic discharge.”

Electrostatic shield “A barrier or enclosure that limits the penetration of an electrostatic field.”

Note: the ESD Association sells most documents, however, the Packaging standard ANSI/ESD S541 and the Glossary ESD ADV1.0 are free downloads from www.ESDA.org (click Standards and then Documents, scroll down to find documents that can be downloaded at no charge).

Pink Vs Black – Use the Right ESD Foam for Your Application

 You might have asked yourself, what is the big difference is between pink ESD foam and black ESD foam? The differences are significant, although one is not necessarily better than the other. Which one you choose depends on what your needs are.

 Pink Static Dissipative FoamPinkFoam_New

  • Static dissipative polyurethane <1011 ohms
  • Antistatic low charging – minimizing electrostatic charge generation
  • Provides protection from physical shock during handling, packaging, shipping, and storage of ESD sensitive devices
  • Ideal for short term use
  • Easy to adapt for custom uses by die-cutting, laminating, etc.PinkFoam_Yellowed_new
  • Non-contaminating, non-corrosive, and non-sloughing
  • Economical

 Usage Consideration

  • Not recommend for lead insertion applications
  • When exposed to the environment, the foam will discolor (turn yellow) over time
  • Will lose electrical properties over time

 

Black Conductive FoamBlackFoam

  • Conductive polyurethane 1 x 103 to < 1 x 105 ohms per ANSI/ESD STM11.11
  • Low density conductive polyurethane foam
  • Permanently conductive; will not lose electrical properties – can be used in applications where permanent ESD properties are required
  • Provides protection from physical shock during handling, packaging, shipping, and storage of ESD sensitive devices
  • Foam will not discolor over time

Usage Consideration

  • Better value for long term applications
  • Not recommended in applications where Static Dissipative properties are required

While each foam is made of the same material (polyurethane), they have very distinct differences. Which one you use will depend on the application of the foam, how long you intend to use the foam,  and even cost considerations.

Learn more about all Protektive Pak foam options. Click Here.

11 Steps to Establishing an ESD Control Plan

1. Define what you are trying to protect.

What is the Human-Body Model (HBM) withstand voltage of the most sensitive item? A prerequisite of ESD control is the accurate and consistent identification of ESD susceptible items. Some companies assume that all electronic components are ESD susceptible. However, others write their ESD control plan based on the device and item susceptibility or withstand voltage of the most sensitive components used in the facility.  A general rule is treat any device or component that is received in ESD packaging as an ESD susceptible item.

2. Become familiar with the industry standards for ESD control.

A complimentary .pdf of ANSI/ESD S20.20-2014 can be downloaded from the ESD Association web site at www.ESDA.org. Also consider purchasing the ESDA’s ESD Handbook ESD TR20.20-2008.

3. Select a grounding / equipotential bonding system.

The 3rd-wire AC electrical equipment ground is the preferred, recommended ground reference.

4. Determine the method of ground for operators (Personnel Grounding).

The two options for grounding an operator are a wrist strap or foot grounders.  Wrist straps must be worn if the operator is seated. If foot grounders are used, an ESD flooring system must be used.  In some cases both wrist strap and foot grounders will be used. The 3rd-wire AC electrical equipment ground is the preferred, recommended ground reference.

5. Establish & Identify EPA(s) – ESD Protected Area(s).

ESD Control Plans must evolve to keep pace with costs, device sensitivities, and the way devices are manufactured. Define the departments and areas to be considered part of the ESD Protected Area.  Consider if customers and/or subcontractors should be included. Implement access control devices, signs, and aisle marking tape to identify and control access to the ESD Protected Area(s).

6. Select ESD control items to be used in the EPA based on your manufacturing process.

Elements that should be considered include: worksurfaces, flooring, seating, ionization, shelving, mobile equipment (carts), and garments.

7. Develop Packaging (Materials Handling & Storage) Plan.

When moving ESD susceptible devices outside an ESD protected area, it is necessary for the product to be packaged in an enclosed ESD Shielding Packaging.

8.  Use proper markings for ESD susceptible items, system or packaging.

From ANSI/ESD S20.20-2014 section 8.5: “the Organization, in developing the ESD Control Program Plan, shall consider the need for marking.”

9. Implement a Compliance Verification Plan.

From ANSI/ESD S20.20-2014 section 7.4: “A Compliance Verification Plan shall be established to ensure the Organization’s fulfillment of the technical requ.rements of the ESD Control Program Plan”.

10. Develop Training Plan.

From ANSI/ESD S20.20-2014 section 7.2: “Initial and recurrent ESD awareness and prevention training shall be provided to all personnel who handle or otherwise come into contact with any ESDS items.”

11.  Make the ESD Control Plan part of your internal quality system requirements.

A written ESD Control Plan provides the “rules and regulations”, the technical requirements for your ESD Control Program. This should be a controlled document, approved by upper management initially and over time when revisions are made. The written plan should include following:

  • Qualified Products List (QPL)A list of EPA ESD control items is used in the ESD control Plan
  • Compliance Verification Plan- Includes periodic checking of EPA ESD control items, and calibration of test equipment per manufacturer and industry recommendations.
  • Training Plan- An ESD Program is only as good as the use of the products by personnel. When personnel understand the concepts of ESD, the importance to the company of the ESD control program, and the proper use of ESD products, they will implement a better ESD control program improving quality, productivity, and reliability.

Watch the Lenovo Service Video on ESD

Lenovo Service posted a video on their youtube site called “Understanding Electrostatic Discharge (ESD) for Technicians.” We encourage you to take a look.

The video is very informative and does a good job of covering the basics of ESD control when working with ESD susceptible devices or components. The basic practices of controlling ESD when handling ESD susceptible items are pretty straight forward.

  • Establish and control access to an ESD Protected Area. It can be one bench or a whole facility (or a field service kit that a Lenovo Service person might use)
  • Ground all conductors including operators.
  • Use a dissipative grounded surface for ESD susceptible products to be placed on if needed.
  • Remove all non-process essential insulators from the ESD Protected Area. Use ionization to control charges on process essential insulators.
  • If an ESD susceptible item needs to be removed from the ESD Protected Area, place it in a shielding bag or storage container that forms a faraday cage.

What is the Real Cost of ESD Damage?

 Article written by Terry Welsher, courtesy of InCompliance Magazine 4Cbw

What percentage of electronic failures are latent defects? What’s the cost to industry? According to the ESD Association “It is relatively easy with the proper equipment to confirm that a device has experienced catastrophic failure. Basic performance tests will substantiate device damage. However, latent defects are extremely difficult to prove or detect using current technology, especially after the device is assembled into a finished product.” So there is the view that, by definition, it is impossible to quantify the amount of latent damage. However, for most companies, the cost of customer returns and field service warranty expense greatly exceeds in-house scrap & re-work expense.

Per the ESD Association: “The age of electronics brought with it new problems associated with static electricity and electrostatic discharge. And, as electronic devices became faster and smaller, their sensitivity to ESD increased. Today, ESD impacts productivity and product reliability in virtually every aspect of today’s electronics environment. Industry experts have estimated average product losses due to static to range [up to] 33%. Others estimate the actual cost of ESD damage to the electronics industry as running into the billions of dollars annually.”

Some major companies report that 25% of all identified electronic part failure is due to ESD. As an ESD Control Program improves, a resulting decrease in unidentified field failures and ”no problem found” returns should occur. Reducing latent defect field failures is what allows companies to report return on investments of 10:1 from their ESD Control Programs.

To continue reading The “Real” Cost of ESD Damage Click Here.

Practical Advice for Implementing ESD Control Periodic Checks

ESD Control Program Periodic Verification
Fred Tenzer and Gene Felder, Desco Industries, Inc.

EPA Room

Want to accomplish something important? A familiar formula is write a plan, select the specifications, and then periodically test to verify that the plan is being implemented according to the test results. This is basically the requirements of an ESD control program, per the ESD Association standard, ANSI/ESD S20.20. This important standard, entitled Development of an Electrostatic Discharge Control Program, covers the requirements necessary to design, establish, implement, and maintain an ESD control program to protect electrical or electronic parts, assemblies and equipment susceptible to ESD damage.

S20.20 is a process document, and provides ESD control plan guidance; one of its requirements is having a “compliance verification plan” as a component of the ESD control plan. Per S20.20, paragraph 6.1.3., Compliance Verification Plan:

“A Compliance Verification Plan shall be established to ensure the organization’s compliance with the requirements of the Plan. Formal audits or certifications shall be conducted in accordance with a Compliance Verification Plan that identifies the requirements to be verified, and the frequency at which those verifications must occur. Test equipment shall be selected to make measurements of appropriate properties of the technical requirements that are incorporated into the ESD program plan.”

To view more information on ESD Control Program Periodic Verification CLICK HERE

Why Use ESD Shielding vs Non-Shielding Containers

ShieldingVsNonShieldingElectroStatic Discharge (ESD) is silent, quick and potentially lethal to electronic parts. When electronic parts are not properly handled during manufacturing, assembly, storage, or shipping, damage from ESD can reach into the millions of dollars each year.

For an ESD control container to be effective against ElectroStatic Discharge, it must possess certain electrical characteristics:

  • Surface resistance <1 x 1011 ohms per ANSI/ESD STM11.11
  • Energy penetration <50 nanoJoules per ANSI/ESD STM11.31

Non-shielding containers might be cheaper, but they are not less costly when it comes to handling ESD sensitive items. Anytime ESD sensitive parts and assemblies are handled, regular containers are not a sound option, even part of the time, as the risk of ESD damage is always lingering. As a result, costs will be incurred, either via ESD damage or as an additional investment in discharge shielding packaging and material handling containers.

The disadvantages of cross-using shielding and non-shielding containers include:

  • Increased cost
  • Risk from ESD damage
  • Handling inconvenience

The cost of a discharge shielding container is far less than the cost associated with damaged parts or extra handling that result with a “less expensive” non-shielding container.

ESD Control – Other Considerations

Application Photo of Surface Resistance Test Kit

OTHER CONSIDERATIONS
Discipline
A significant increase in the discipline of implementing the fundamentals of ESD control noted in ANSI/ESD S20.20 Foreword, calls for:

  • Ground all conductors in the EPA including people
  • Remove all insulators from the EPA or use ionizers for process necessary insulators
  • Package ESD sensitive items going outside the EPA in packaging that provides electrostatic discharge shielding

Insulators
We encourage developing a hatred for insulators. The alternatives are:

    Remove the insulative item from the EPA

  • Substitute the item with an ESD protective version (such as tape, document holders, material handling containers, plastic bottles, etc.)
  • Periodically treat insulative surface with a topical antistat
  • Neutralize electrostatic charges using ionization

Other ESD Control Items
Other EPA ESD control items to add to the ESD control program might include shelving, mobile equipment (carts), gloves, and/or seating.

Improve Compliance Verification Plan

  • Consider greater frequency of internal audits per ESD TR53
  • Use of computer data collection system for wrist straps and footwear testing, continuous monitors, and ionizers
  • Use of ground continuous monitors for worksurfaces and other ESD elements
  • Test ionizers more frequently, consider self monitoring ionizers, consider computer based data collection
  • Increased testing using static field meter to verify that automated processes (like auto insertion, tape and reel, etc) are not generating charges above acceptable limits.

Application Photo of Volt Meter and Software in Factory STM97.2 Testing Voltage Charge on Person (Photograph courtesy of TREK, INC.)

Improve Training

  • ESD awareness training for all in the EPA or who may come into the EPA including suppliers
  • Testing to verify comprehension and training adequacy
  • Training on the proper use of test equipment
  • Training on proper compliance verification test procedures

Application Photo CD-ROM ESD Training

Conclusion
Just to maintain a company’s current level of quality and reliability may require a substantial improvement in a company’s ESD control program. Now is the time for improvement as ESD sensitivity withstand voltages continue to get lower and companies may soon be handling class 0A HBM items. To combat HBM failures improved personnel grounding is required. For example, heel grounders should be replaced with full coverage foot grounders. However, most failures are CDM. To combat CDM failures, ionization should be added or improved, and conductive surfaces should be covered with dissipative material. In general, disciple should be enhanced implementing ESD control fundamentals, compliance verification testing should be increased, and training should be improved.

From published article “Now is the Time for ESD Control Programs to be Improved” by Fred Tenzer and Gene Felder. See full article at InCompliance Magazine- September 2012

Tips for Addressing Charged Device Model Failures


CHARGED DEVICE MODEL

It may seem to some that CDM has newly arrived as a problem for ESD control programs. However, the ESD Association first published ANSI/ESD STM5.3.1 in 1999 – ESD Association Standard for Electrostatic Discharge Sensitivity Testing – Charged Device Model (CDM) – Component Level. Basically, CDM testing has to do with “testing, evaluating and classifying the electrostatic discharge (ESD) sensitivity of components to the defined charged device model (CDM)” … “to allow for accurate comparisons of component CDM ESD sensitivity levels.”

JESD22-C101C Field-Induced Charged-Device Model Test Method for Electrostatic-Discharge-Withstand Thresholds of Microelectronic Components Table 3
Devices shall be classified as follows:
CLASS I <200 volts
CLASS II 200 to <500 volts
CLASS III 500 to 1000 volts
CLASS IV >1000 volts

The importance of CDM came about primarily because of the increased use of automated component handling systems. The Foreword of ANSI/ESD STM5.3.1 states “In the CDM a component itself becomes charged (e.g., by sliding on a surface (tribocharging) or by electric field induction) and is rapidly discharged (by an ESD event) as it closely approaches a conductive object.”

In November 2002, Roger Peirce published an article entitled “The Most Common Causes of ESD Damage”. There were actually 23 causes. As the founder and president of ESD Technical Services, Roger had investigated hundreds of companies for over eight years. All 23 causes were CDM failure modes. So CDM is really not so new, it has just received a lot of attention in the last few years.


TACKLING CDM

So, what are the things companies should look at to improve their ESD control program regarding CDM? It would seem to be easy: don’t slide ESDS devices and assemblies unless grounded at all times, keep insulators at least 12” away from ESDS, and don’t allow ESDS items to make contact with a conductive surface. Seems simple, but in actual application . . . not so easy.

If the ESD control program has not used ionization that should be considered. If the ESDS items becomes charged, ionization will help neutralize the charge. The primary function of ionizers with regard to ESDS items are:

  • To remove / neutralize charges from process necessary insulators, which can charge ESDS items, thus creating the potential for a damaging CDM event
  • Remember that the PCB substrate is a process necessary insulator and can become charged during automated handling processes
  • To remove / neutralize charges from a charged, isolated/floating conductor, which, when grounded can result in a potentially damaging CDM event
  • Remember that during automated handling processes, the ESDS devices on the PCB are isolated or floating conductors

Application Photo Overhead Ionizer

The ESD Standards Committee has a Working Group (WG-17) which is currently involved with developing a Standard for Process Assessment to help the electronics community assess their manufacturing and handling processes to determine what levels of devices their process can handle. Once one fully understands where their process is with regards to ESDS devices and assemblies, they will have a clearer picture on what actions need to be taken to further improve the ESD Control Program.

If ionizers are already in use, the company should consider reducing the ionizer offset voltage limit of ±50 volts (the required limit in ANSI/ESD S20.20) to ±25 volts and maybe less, depending on the application and device sensitivity. Discharge times are user defined and should be considered for reducing the time required to neutralize a ± 1,000 volt charge to ± 100 volts.

The required limit for worksurfaces per ANSI/ESD S20.20 is less than 1 x 10^9 ohms with no lower limit. Most companies handling electronics should be following the recommendation of Worksurface standard ANSI/ESD S4.1 that the lower limit be 1 x 10^6 ohms. To combat CDM failures, all surfaces that might come into contact with ESDS items should be dissipative at the 1 x 10^6 to less than 1 x 10^9 ohms range used for worksurfaces where possible. Items such as Static Shielding bags will have a higher resistance on the interior & exterior surfaces, but it still must be less than 1 x 10^11 ohms.

Application Photo Statfree Worksurface Mat

From published article “Now is the Time for ESD Control Programs to be Improved” by Fred Tenzer and Gene Felder. See full article at InCompliance Magazine- September 2012