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Now is the Time for ESD Control Programs to be Improved

Originally Published by InCompliance Magazine- September 2012
“By Fred Tenzer and Gene Felder”

ElectroStatic Discharge (ESD) is the hidden enemy within your factory. You cannot feel or see most ESD events but they can cause electronic components to fail or cause mysterious and annoying problems. There are two types of ESD damage: 1) Catastrophic failures, and 2) Latent defects. By definition, normal quality control inspections are able to identify catastrophic failures, but are not able to detect latent defects.

In general, the ESD susceptibility of modern electronics are more sensitive to ElectroStatic Discharge; that is the withstand voltages are lower. This is due to the drive for miniaturization particularly with electronic devices operating faster. Thus the semiconductor circuitry is getting smaller. For example Intel began selling its 32 nm processors in 2010 that would be 0.032 micrometer equal to 0.000032 millimeter or 0.00000128 inch.

For more information on ESD and the direction of electronics manufacturing, see the articles listed below.

Evaluation Engineering Magazine November 2001 article “ESD Control Program Development” “As the drive for miniaturization has reduced the width of electronic device structures to as small as 0.10 micrometer (equal to 0.0001 millimeter or 0.000004 inch), electronic components are being manufactured with increased ElectroStatic Discharge (ESD) susceptibility.”

www.ESDA.org, the ESD Association’s latest White Paper “Electrostatic Discharge (ESD) Technology Roadmap – Revised April 2010” forecasts increased ESD sensitivities continuing the recent “trend, the ICs became even more sensitive to ESD events in the years between 2005 and 2009. Therefore, the prevailing trend is circuit performance at the expense of ESD protection levels.” The White Paper’s conclusions are:

“With devices becoming more sensitive through 2010-2015 and beyond, it is imperative that companies begin to scrutinize the ESD capabilities of their handling processes. Factory ESD control is expected to play an ever-increasing critical role as the industry is flooded with even more HBM and CDM sensitive designs. For people handling ESD sensitive devices, personnel grounding systems must be designed to limit body voltages to less than 100 volts.

To protect against metal-to-device discharges, all conductive elements that contact ESD sensitive devices must be grounded.

To limit the possibilities of a field induced CDM ESD event, users of ESD sensitive devices should ensure that the maximum voltage induced on their devices is kept below 50 volts.

To limit CDM ESD events, device pins should be contacted with static-dissipative material instead of metal wherever possible.”

InCompliance Magazine May 2010 article by Dr. Terry L. Welsher The “Real” Cost of ESD Damage which includes “Recent data and experience reported by several companies and laboratories now suggest that many failures previously classified as EOS may instead be the result of ESD failures due to Charged Board Events (CBE). … Some companies have estimated that about 50% of failures originally designated as EOS were actually CBE or CDE.”

Charleswater

For additonal technical information Click Here

To read the rest of the article go to Now is the Time for ESD Control Programs to be Improved

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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

Use an Overhead Ionizer to neutralize charges at your workstation.

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.

Use a Statfree Dissipative Mat on your workstation.

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

Continuous Monitors: What’’s Better – Single-Wire Impedance or Dual-Wire Resistance Monitors?

Dual-Wire Continuous Monitor

Fred Tenzer on Continuous Monitor History and Preference

By Fred Tenzer

First off, both technologies work fine, but one needs to understand the technologies to understand the shortcomings of each. Let me start with the following basic historical information that will make my “preferences” more clear. If you choose to just know the answer, scroll to the bottom, but I believe this information will be very helpful to you in making your decision. All the technologies will also monitor the worksurface ground circuit and while there are some differences, the worksurface part of the monitoring system is NOT discussed below.

History

When people realized that Operator Grounding was the foundation of an ESD Control Program, wristbands and coil cords came into big time use. The first ESD Association Standards meeting was in 1982 and the first standard written produced by the ESD Association was for wrist straps. The weakest part of the system was the coil cord and testing was developed for bending or flex life testing. The minimum flex life was established at 16,000 flex cycles and in the mid-1980’s that was tough to achieve.

Thus, monitoring technology was initially developed to detect initial flex fatigue while it was still in the “intermittent” stage, which is prior to a permanent open being created. Touch testing would almost never detect this “intermittent” failure mode. In addition, if a wrist strap system was touch-tested twice a day and an operator passed at 1:00 PM on Monday and failed at 8:00 AM on Tuesday, all the work that had peen performed at that station after 1:00 PM on Monday would now be suspect and would be a cause for more detailed quality inspections by many companies. Therefore, while discovering an operator grounding problem was good, it was also costly due to increased Quality Control. Thus, monitoring of the “operator ground system” grew in customer desirability and has resulted in technology improvements by some of the manufacturers and inventors of monitoring technology.

Single-Wire Monitoring Technology

Originally, simple “AC capacitance” single-wire monitors were developed. There were many shortcomings of this technology, all stemming from mostly “false negatives” (unit indicating the operator was grounded when he was not) and “false positives” (alarms going off when they shouldn’t). This technology is still around today and is purchased by some because of its low cost, around £25-£35 per operator and a lack of knowledge by the End User. A big plus is being able to use any standard single-wire wrist strap.

Wave Distortion Single Wire Continuous Monitor

The next level in single-wire evolution was “impedance” technology. However, since the capacitance and therefore the impedance of the circuit will also vary with such things as the person’s size, clothing, shoe soles, conductance of the floor, chair, table mat etc. these monitors often have to be adjusted or tuned to a specific installation and operator. Again, there were resulting “false positives” and “false negatives” though this was an improvement over the simple “capacitance” technology. This technology is also still around; the driver is low cost, £30 -£45 per operator.

The top of single-wire monitoring technology is called “Wave Distortion”. What this technology looks at is not the impedance level, but at the waveform generated by the circuit. Current will leak voltage at various points due to the combinations of resistance and capacitive reactance. There is a negligible amount of inductive reactance from the coil cord. By monitoring these “distortions” or phase shifts the Wave Distortion Monitor will determine if the circuit is complete i.e.; the wearer is in the circuit and the total equivalent DC resistance is within specifications given a range of installations. This technology is very reliable, (virtually no “false positives” or “false negatives”) and response time is very fast (<50 ms). In addition, the wrist strap open circuit test voltage is very low at 1.2 volts peak-to-peak @ 1-2 Micro Amps. Thus, a very low voltage is applied to the operator. The cost for this technology is £75 – £90 per operator.

To continue reading Click Here

Charleswater Statfree Euro T2™ Mats Outlast the Competition

The authors of a recent article in InCompliance Magazine titled Early Life Failure of Dissipative Workstation Mats, have confirmed that Desco’s Statfree® T2 was the top performing worksurface mat (Mat ID#4 in the article) in their study. Charleswater is part of Desco Industries, Inc. and Statfree Euro T2™ – Dissipative Dual Layer Rubber has a similar product composition.

Part of any good ESD Control Programme is periodic verification of the specs of products being used for the ESD Control Plan. The most obvious example of periodic testing is when operators test their foot grounders or wrist straps before entering an ESD Protected Area. The IEC 61340-5 series describes the test methods and instrumentation that can be used to periodically verify the performance of ESD protective equipment and materials. Plexus Manufacturing Solutions in Neenah, Wisconsin, USA noticed during periodic verification of their working surface mats, that the mats were drifting out of spec and Plexus wanted to determine what was causing the mats to fail. Through their in house tests, they concluded that:

  • A solid ESD control programme including compliance verification periodic testing with data collection provides valuable and useful information.
  • Factory fluorescent lighting, likely from ultraviolet (UV) radiation, can have a measurable effect on the electrical properties of ESD dissipative mats over time.
  • Different mats tolerate or resist the effects of factory fluorescent lighting.
  • Since this experiment did not take into account lot to lot variation at the supplier for each mat P/N, future mats purchased will require lot traceability information to be stamped on the bottom of the roll, every 3 feet minimum.
  • One should consider adding ultraviolet light resistance as a property to consider in the working surface selection process.

Statfree Euro T2™ – Dissipative Dual Layer Rubber mats include Ultraviolet (UV) stabilizer additives in the mat formula to stabilize color retention, ensure ESD performance over time and eliminate surface layer deterioration resulting in cracking when the product is flexed. Additionally, we mark lot traceability information on the bottom of the roll every 3 feet to provide tracking information for lifespan of the product and to ensure quality control.

Enhancing Profits with Effective ESD Control

Our thanks to Conformity Magazine Published in December 2004 issue

Accurate process evaluation provides real answers

Provided by the ESD Association
by Stephen Halperin, in collaboration with Ron Gibson

“We need to spend HOW MUCH?”
Recently, a company experienced several large losses due to electrostatic discharge (ESD) and had a very unhappy customer on their hands. The manufacturing vice president now faced a substantial expenditure for new ESD loss prevention equipment. The company’s first step had been to hire an ESD consultant who recommended the purchase of several thousands of dollars in ionization equipment and monitoring instruments for several of the company’s facilities.

The troubled VP read the report several times looking for justification of the expense. However, the report did not define how the recommended equipment would meet the VP’s specific needs. Other than describing how ionization reduced electrostatic charge after it is generated and that the instruments could confirm that a discharge occurred, the report did not identify the actual cause of the process problem. No ESD measurements were described. There were no details related to cause of product loss, device sensitivity concerns, value issues, process and handling details, examination and description of existing controls, or rationale for how the recommended tools would solve the problem in question. The report was clearly based on the consultant observing the process of a single manufacturing environment. In effect, the report made a purchasing recommendation based on a “blanket” opinion, not on facts specific to the needs of the company or their customer. Such an approach typically makes a bad situation worse. While the recommended tools may have been very useful for investigating a process or for solving defined problems, they are expensive Band Aids“ when used in undefined problem situations.

Today’s electronic manufacturing environment demands that minimal ESD controls be in place to provide fundamental protection for electrostatic discharge sensitive (ESDS) devices. When basic ESD controls are employed and losses still occur, manufacturing and quality managers face more difficult problems., In assessing the problem, companies struggle with a variety of major questions concerning a specialized technology, while having minimal information and available skills. To avoid the risk of making the wrong investment decision without solving the initial problem, management needs a way to select and implement the most effective ESD controls that fit their financial situation, solve their specific problems, and provide a respectable return on their investment.

To continue reading Enhancing Profits with Effective ESD Control Click Here

ESD Control Programs Should be Improved

ElectroStatic Discharge (ESD) is the hidden enemy within your factory. You cannot feel or see most ESD events but they can cause electronic components to fail or cause mysterious and annoying problems. There are two types of ESD damage: 1) Catastrophic failures, and 2) Latent defects. By definition, normal quality control inspections are able to identify catastrophic failures, but are not able to detect latent defects.

In general, the ESD susceptibility of modern electronics are more sensitive to ElectroStatic Discharge; that is the withstand voltages are lower. This is due to the drive for miniaturization particularly with electronic devices operating faster. Thus the semiconductor circuitry is getting smaller.

See November 2001 Evaluation Engineering Magazine article “ESD Control Program Development” “As the drive for miniaturization has reduced the width of electronic device structures to as small as 0.10 micrometer (equal to 0.0001 millimeter or 0.000004 inch), electronic components are being manufactured with increased ElectroStatic Discharge (ESD) susceptibility.”

What’s happening currently? Intel began selling its 32 nm processors in 2010 that would be 0.032 micrometer equal to 0.000032 millimeter or 0.00000128 inch.

See www.ESDA.org, the ESD Association’s latest White Paper “Electrostatic Discharge (ESD) Technology Roadmap – Revised April 2010” forecasts increased ESD sensitivities continuing the recent “trend, the ICs became even more sensitive to ESD events in the years between 2005 and 2009. Therefore, the prevailing trend is circuit performance at the expense of ESD protection levels.” The White Paper’s conclusions are:

“With devices becoming more sensitive through 2010-2015 and beyond, it is imperative that companies begin to scrutinize the ESD capabilities of their handling processes. Factory ESD control is expected to play an ever-increasing critical role as the industry is flooded with even more HBM and CDM sensitive designs. For people handling ESD sensitive devices, personnel grounding systems must be designed to limit body voltages to less than 100 volts.

To protect against metal-to-device discharges, all conductive elements that contact ESD sensitive devices must be grounded.

To limit the possibilities of a field induced CDM ESD event, users of ESD sensitive devices should ensure that the maximum voltage induced on their devices is kept below 50 volts.

To limit CDM ESD events, device pins should be contacted with static-dissipative material instead of metal wherever possible.”

See InCompliance Magazine May 2010 article by Dr. Terry L. Welsher The “Real” Cost of ESD Damage which includes “Recent data and experience reported by several companies and laboratories now suggest that many failures previously classified as EOS may instead be the result of ESD failures due to Charged Board Events (CBE). … Some companies have estimated that about 50% of failures originally designated as EOS were actually CBE or CDE.”

Charleswater

For additonal ESD information Click Here

ESD Control Program Considerations when Dealing with Class Zero Items

ANSI/ESD S20.20 Foreword states:

  • “This standard covers … electrical or electronic parts, assemblies and equipment susceptible to damage by electrostatic discharges greater than or equal to 100 volts Human Body Model (HBM).”
  • “When handling devices susceptible to less than 100 volts HBM, more stringent ESD Control
    Program Technical Requirements may be required, including adjustment of program Technical
    Element Recommended Ranges.”

HMB Classification Class 0 is:
Per ESD-STM5.1 Human Body Model (HBM) Table 1 Class 0 has ESD Voltage Range < 250 Volts
Basically, to control the environment to decrease the probability of ESD damage in “Class Zero”
situations, involves increasing ESD protective redundancies and periodic verifications to those ESD
Control technical elements.

Improved Grounding

  • Personnel: Decrease Wrist Strap and ESD Footwear upper limit permitted (The ESD Association has test data showing charge on a person is less as the path-to-ground resistance is less) The use of continuous monitors, smocks, use / increased use of ESD flooring, sole or full coverage foot grounders (HBM & CDM)
  • Worksurfaces: Dissipative (CDM) i.e. change < 10^9 to a requirement of 10^6 to 10^8 ohms
  • Bonded grounds – Carts, shelves, equipment
  • Conductors: Minimizing isolated conductors like devices on PC Boards (CDM)

To see examples of Wrist Straps capable of dealing with class zero environments Click Here

To see examples of Grounding Cords capable of dealing with class zero environments Click Here

Minimize Charge Generation
The best form of control is to minimize charge generation. Grounding and ionization eliminate charges once generated. Shielding protects from generated charges.

  • Personnel – Low Charging floor finish
  • Surfaces – Use of low charging (anti-static) topical treatments

Insulators

  • Eliminate as best as possible all non-process necessary insulators
  • Topically treat where ever possible insulators that cannot be removed
  • Consider use of ESD Chairs or treat to reduce charge generation
  • Shield charges on clothing by using ESD Smocks

To continue reading ESD Control Program Considerations when Dealing with
Class Zero Items Click Here

Reducing Floor Maintenance Costs while Improving ESD Performance


by Rick Cardinale, Bird Electronic


Bird Electronic, founded in 1942 by J. Raymond Bird, soon became a leader in radio frequency instrumentation. Today, Bird also has moved into digital instrumentation test equipment.


With the development of digital instrumentation came the increased need for controls to prevent ESD events. Improving ESD protection has been an ongoing process since the late 1980s. In 1997, the company determined that an automated PCB production line would be installed and that the entire manufacturing area should be protected against ESD.


This decision led to an evaluation of ESD protective flooring. In 1998, 20,000 square feet of conductive floor tile were installed in the main production area. To help brighten the area, white tile was selected. The floor resistance measured less than 1.0 × 10^6 ohms.


High-Cost Maintenance


A bright, high-gloss appearance was part of the selection criterion for the floor. While the electrical properties were unchanging, by 1999, the floor was starting to dull. It was being maintained like a regular tile floor. No waxes or finishes were used; however, the tile manufacturer did recommend using buffing pads.


After consulting with the tile manufacturer and the installer, maintenance was increased to sweeping clean and damp mopping two times per week and buffing once per month. Monthly floor maintenance was $1,700 per month, a $20,400 annual expenditure.


In late 1999, the maintenance schedule was modified to add more buffing since this was the only way to keep the floor shiny. The floor now was swept and damp mopped weekly and buffed twice per month. The floor was clean and shiny, but the cost went up 41% to $2,400 per month, a $28,800 annual expenditure.

Click Here to continue reading Reducing Floor Maintenance Costs while Improving ESD Performance

Use ESD Control Products Correctly Or You Can Do More Harm Than Good

A Comprehensive Program Is Required For Effective ESD Control

With most companies pressured by global competition, effective ESD control can be a key to improving productivity, quality, and customer satisfaction. It is a pity that many companies buy ESD protective products or equipment and then misuse them, often causing more harm than good.

Electronic components that are electrostatic discharge sensitive (ESDS) must be protected throughout the entire manufacturing cycle. According to ANSI/ESD S20.20, the ESD Association’s standard for the development of an Electrostatic Discharge Control Program, safeguards are required during activities that “manufacture, process, assemble, install, package, label, service, test, inspect or otherwise handle electrical or electronic parts, assemblies and equipment susceptible to damage by electrostatic discharges.”

If ESD latent defects occur during this manufacturing and product cycle, it can be most frustrating and costly. Latent defects in components by definition will not be detected so products will pass normal inspections. ESD damage is the hidden enemy; electrostatic charges cannot be seen, typically discharges less than 3,000 volts cannot be felt, and latent defects cannot be detected through normal quality control procedures.

Manufacturing facilities should be as diligent with their ESD control program as hospital operating rooms are in implementing sterilization procedures. Damage caused by invisible and undetectable events occurs in medicine where people can experience infection or even death from viruses or bacteria. In hospitals, the defense against this invisible threat is extensive contamination control procedures including sterilization.

To learn more about correct ESD product usage Click Here

ESD Control Programme Periodic Verification

by Fred Tenzer and Gene Felder, Desco Industries, Inc.

Some practical advice for implementing
ESD control periodic checks
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