ESD Control Program Development

Ryne C. Allen & Gene Felder

Desco Industries Inc. (DII), Employee Owned

November 2001

Reproduced with Permission, EE-Evaluation Engineering, November, 2001

Abstract

This paper helps guide a company that manufactures electronic components or devices in developing or re-evaluating their ESD Control Program Plan. The ESD Association is the primary standards organization that is applied in the Plans development. Key questions and technical requirements are listed to help the ESD Coordinator or Quality Manager in their writing of their Plan.

 

I - INTODUCTION

ESD Control – Increasingly More Important

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. With increased processing power and lower costs, these electronic components are increasingly being used in more and different products particularly to differentiate products and provide value-added features.

Any relative contact and physical separation of materials [or flow of solids, liquids, or particle-laden gases] can generate electrostatic charges. Common sources of electrostatic charges include personnel, items made from common polymeric materials, and processing equipment. ESD can damage parts by direct contact with a charged source or by electric fields emanating from charged objects that induce a charge on grounded sensitive items.

Although having a very short duration even less than a nanosecond but with peak current reaching several amperes, a discharge of static electricity is literally a miniature lightning bolt, producing heat that can easily burn through microelectronic structures. A human being cannot feel ESD voltage until it reaches approximately 3,000 volts, while many item’s ESD susceptibility or "Withstand Voltage" rating can even be lower than 50 volts.

As manufacturers using electronic components try to improve their quality, productivity, and customer satisfaction, optimizing their ESD Control Program is a key focus of leading companies. Protecting these electronic components from ESD only most of the time is not acceptable. ESD protective products and procedures must provide continuous ESD protection from component suppliers through all manufacturing steps including inspection, test, storage, shipment, installation, use, maintenance, replacement and repair functions.

ESD is the invisible enemy and may cause as much as 30 to 50% of unidentified quality problems. Even more likely is that ESD events are the cause of maddening, difficult to duplicate, and intermittent quality problems. These are the ones that consume lots of time, annoy all involved, and often never get resolved. Combating the invisible enemy with an effective ESD Control Program can produce very beneficial results. Reducing catastrophic failures produce financial benefits, but the greatest savings come from reducing latent defects, which are extremely difficult to detect, especially after the component is assembled into a finished product. Effective ESD Control can minimize frustrating, mysterious quality and product problems.

 

Fundamental ESD Control Principles

The fundamental ESD control principles are:

  • ESD susceptible components and products be known and clearly identified
  • All conductors, including personnel, be grounded in an ESD protected area
  • As insulators cannot be grounded, non-essential insulators be removed from ESD protected areas and essential insulators have charges neutralized via ionization
  • ESD susceptible items transported or stored outside an ESD protected area be enclosed in static shielding packaging

 

ANSI/ESD S20.20

The ESD Association has a new ESD Control Program standard: ANSI/ESD S20.20[1] for the Development of an Electrostatic Discharge Control Program for – Protection of Electrical and Electronic Parts, Assemblies and Equipment (Excluding Electrically Initiated Explosive Devices).

The ESD Association[1] states, "This standard covers the requirements necessary to design, establish, implement, and maintain an Electrostatic Discharge (ESD) Control Program for 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 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.

This standard is becoming increasingly more important to manufacturers using electronic components. If a business’ success is not currently subject to passing customer, ISO, or other ESD audits, that day is likely to be coming. In conjunction with the standard, the ESD Association has begun a S20.20 certification program in which it appoints ISO 9000 Registrars to be approved to conduct audits according to the ANSI/ESD S20.20 ESD Control Program Standard. If a company handles ESD susceptible products, within some period of time, it is likely that a prerequisite for doing business will be to become certified to the ANSI/ESD S20.20 standard.

In addition to staying in business, the benefits of optimizing an ESD Control Program can be huge as with improved quality, productivity and customer satisfaction, companies can convert ESD Control from a prerequisite to a competitive advantage. A properly designed and successfully deployed ESD Control program is a proven money saver with an ROI of up to 1,000% per year [2].

 

Management Support Essential

Caution, don’t try to enact an effective ESD Control Program at work without management support or that effort will likely be frustrating. Well, maybe one should try, but an effective ESD Control Plan requires the support of top management and all the other departments. A key should be to have regularly scheduled ESD committee meetings where all appropriate departments are represented. A successful ESD Control Program is one that is encompassed by all employees, empowering the actual line worker to carry out the plan from ground level to clearly defining the plans importance to management so the whole team is involved.

 

Prerequisite

A written ESD control plan should be based on the device and item withstand voltage of the most susceptible components used in the facility or cell. Examples of ESDS parts are microcircuits, discrete semiconductors, thick and thin film resistors, hybrid devices and piezoelectric crystals. Typically, the easiest way to establish the ESD susceptibility of ESDS items in your facility is to refer to the Reliability Analysis Center "V-ZAP" data book that contains ESD susceptibility data for 22,000 devices, including microcircuits, discrete semiconductors and resistors [3]..

 

II - ESD Control Program Written Plan

First, one needs to write an ESD Control Program Plan [4] as ANSI/ESD S20.20 paragraph 6.0.1. states "ESD Control Program Requirements, The Program shall include both Administrative and Technical Requirements. The Organization shall establish, document, implement, maintain and verify the compliance of the Program."

Included in the ESD Control Program written plan will be how those involved will be trained, how it will be verified that the plan is being followed, and a list of the technical requirements and ESD protective products approved to be used in the Program. S20.20 paragraph 6.1.1.1. states "The Plan is the principal document for implementing and verifying the Program. The goal is a fully implemented and integrated Program that conforms to internal quality system requirements." And "Efforts to identify and eliminate defects, and prevent their introduction, shall be a component of the Plan to reduce the cost and risk associated with ESD damage." So Design Engineering must identify ESD susceptible components and know their withstand voltage. The ESD Control Program written document is not one to be written and filed away, but to be used along with other quality efforts, to improve product performance and eliminate waste.

 

Personnel Safety Paramount

Before we get to the key questions of ESD Control, it is important to note that personnel safety is paramount, and more important than ESD Control is. We don’t want grounded personnel to be like walking out in a storm holding a car antenna. In the factory, the grounding of personnel around electrical line voltage is the possible hazard. Personal grounding should not be used when working around voltages over 250 VAC. Although personal grounding items are to include a 1 Megohm resistor to limit current to less than 0.5mA, ground fault circuit interrupters (GFCI) should be used. The ESD Control Program can in no way replace or supersede any requirements for personnel safety.

 

Key Questions

So key questions are:

  • Do you have a written ESD control plan?
  • Is it based upon and do you know the ESD sensitivity of the items you handle?
  • Are your employees trained in ESD control? Per ANSI/ESD S20.20 paragraph 6.1.2.1 Training Plan Requirement "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 which.shall include an objective evaluation technique to ensure trainee comprehension and training adequacy."
  • Do you have a plan for verifying compliance? Do you have scheduled audits to verify that your scheduled checklists are being performed and that records are saved? Are the tools available and calibrated to make accurate measurements?
  • Are ESD protected areas clearly identified? Does the company and all suppliers clearly identify ESD susceptible items?
  • In ESD protected areas are all conductors, including personnel, required to be electrically connected and attached to a known ground? Does this include supervisors, engineers, and visitors? If all charges are kept at the same level [zero is nice but not essential] balance is achieved and there will be no discharge events.
  • In ESD protected areas, are non-essential insulators removed? Insulators are non-conductors and, by definition, cannot be grounded.
  • Do you require the use of ionizers in ESD protected areas to neutralize charges on essential insulators? Is sufficient control exercised so ionizers are not turned off and that ionizers with heaters are not used as foot warmers?
  • Do you require all transportation and storage of ESD susceptible items outside ESD protected area be completely enclosed in static shielding packaging? Packaging should create a Faraday Cage, which will isolate the contents from electrostatic charges and their fields.
  • Does the ESD Control Plan entail implementation of Program requirements during design, production, inspection, test, storage, shipment, installation, use, maintenance, replacement and repair functions?
  • Does the Plan require an approved product list [APL] of the specific type of ESD protective materials and equipment used in the Program?
  • Do Verifications include routine checks of the Technical Requirements in the Plan?
  • Since a propensity for charge generation and accumulation increases with a reduction in humidity, is humidity controlled?
  • Do you use S20.20 Table 1 as your Technical Requirements or have you determined and documented others?

 

ESD Control Program Written Plans

Typical ESD Control Program written plans will include:

  • ESD protected areas should be clearly identified; personnel should never enter an ESD protected area without taking the proper precautions
  • ESDS items to be opened or removed from protective containers only within an ESD protective workstation or area
  • Personnel should be at ground potential when handling ESD susceptible [ESDS] items. When seated have wrist strap snugly on skin and plugged into common point ground. If ESD protected flooring is used, two foot grounders are to be worn in ESD protected area
  • ESD protected work surface to be clean and clear of unnecessary materials, particularly common plastics or any other electrostatic generating material [no regular high charging packaging, etc. to be permitted in ESD protected area]
  • ESD mats and conductive/dissipative surfaces to be regularly cleaned and only with ESD cleaners that do not leave an insulative residue
  • Work and storage surfaces in ESD protected areas or environments should be covered with static dissipative material, such as matting or high-pressure laminate, and be grounded [however, daisy-chaining is not permitted]
  • All ESDS items should be properly identified with ESD susceptibility symbol & enclosed within ESD shielding bags or other sealed conductive or shielding container during storage or transportation outside an ESD Protected Area
  • Insulative material or other static generating items necessary in the production process should be neutralized with an ionizer [Ionizers to be tested periodically ensuring balance and charge decay]
  • Personnel and work surface grounding devices to be tested periodically and records of test kept on file
  • Personnel training and testing described to verify that they understand the principles of ESD control and how to effectively use ESD protective equipment
  • Regular intervals for routine auditing and inspection of ESD protected work areas specified
  • Test equipment specified
  • ESD protective products [such as wrist straps, mats, flooring, footwear, packaging, garments, ionizers] specified

 

Technical Requirements

ESD Control Program written plan technical requirements will typically adopt the recommended range listed in Table 1 of S20.20 [1], including:

  • ESD Protective Work Surface: < 1.0 X 10^9 ohms tested per ESD S4.1, with lower limit of 1.0 X 10^6 as recommended in ESD-ADV53.1
  • ESD Protective Flooring or Floor Mats < 1.0 X 10^9 ohms tested per ESD S7.1 [When the Flooring – Footwear system is the primary grounding method, a S20.20 recommended range is < 3.5 X 10^7 ohms tested per ESD STM 97.1 where the resistance measurement is in combination with the person or charge generation is less than 100 volts]
  • Wrist Strap System < 3.5 X 10^7 ohms per S1.1 that will provide a continuous electrical path from the user directly to ground
  • ESD Protective Footwear (heel straps, toe straps or conductive shoes) that will provide a continuous electrical path from the user directly to the ESD protective flooring or mat < 1.0 X 10^9 ohms [shoes tested per ESD S 9.1]
  • Electrostatic Generating Sources - Nonessential and personal items shall not be placed on ESD protective work surfaces. Essential materials under normal use shall not cause or generate static voltages of greater than +/- 2,000 volts within 12 inches of unprotected ESDS devices
  • ESD Protective Garments 1 X 10^5 to 1 X 10^11 ohms tested per ESD STM 2.1 [ESD smocks may be used to shield ESDS from charges on insulative clothing. When worn, they should cover all personal garments above the wrist except at the neck area, and make intimate contact with the skin; otherwise, the ESD smock becomes an isolated ungrounded conductor.]
  • Ionizers ,+/- 50 Volts Voltage Offset tested per ESD S 3.1

 

Tailoring

A company’s ESD Control Program written plan should suit it and optimize cost effectiveness. ANSI/ESD S20.20 may not apply to all situations. Additional precautions may be necessary if the Withstand Voltage of components handled is less than 100 volts [Human Body Model (HBM)]. The Charge Device Model (CDM) should be considered when tailoring your plan in addition to the HBM. Requirements can be relaxed as appropriate. Per S20.20 paragraph 6.0.3, "Tailoring is accomplished by evaluating the applicability of each requirement for the specific application. Upon completion of the evaluation, requirements may be added, modified or deleted. Tailoring decisions, including rationale, shall be documented in the ESD Control Program Plan".

 

 

 

III - CONCLUSION

ESD Control Program Must Be Comprehensive

If you have a medical operation, to avoid infection, proper sterilization procedures must be strictly followed by all involved. It does little good if all personnel and all equipment except the scalpel were properly sterilized. Likewise, for an effective ESD Control Program to be effective, it must be comprehensive. ESD susceptible components must be protected at every step along its manufacturing-test-storage cycle. ESD control knowledge and appreciation, and a functioning ESD Committee with representation from all departments with top management support is imperative. Doing such leading companies turn their ESD Control Programs into a competitive advantage strategic tool focused on quality, productivity, and customer satisfaction improvement.

An ESD Control Program is documented into a protection Plan that encompasses the processes, personnel and ESDS devices. This Plan is catered to each company based on their specific needs, but should follow basic industrial guidelines as set forth by ANSI/ESD S20.20. Management support, personnel training and consequential follow up Audits [5] are all part of an effective ESD Control Program.

 

IV - REFERENCES

  1. ANSI/ESD S20.20, ESD Association, 7900 Turin Road, Bldg. 3, Suite 2, Rome, NY 13440-2069, 1999, http://www.eosesd.org
  2. ESD Control and ROI, Allen, Ryne, EE Evaluation Engineering, , November 1999 http://www.evaluationengineering.com/archive/articles/1199cope.htm
  3. VZAP-95, Electrostatic Discharge Susceptibility Data Book, Reliability Analysis Center, Rome, NY, Web: http://rac.iitri.org/cgi-rac/iPC/iPC?VZAP-95
  4. How to Set Up an ESD Control Program, Allen, Ryne, EE Evaluation Engineering, February, 1999, web: http://www.evaluationengineering.com/archive/articles/0299esd.htm
  5. Audits Essential to Successful ESD Control Programs, Allen, Ryne, EE Evaluation Engineering, December, 1999, http://www.evaluationengineering.com/archive/articles/1299cope.htm

 

About the Authors

Ryne C. Allen is the technical manager at ESD Systems.com, a division of Desco Industries, Inc. (DII). Previously, he was chief engineer and lab manager at the Plasma Science and Microelectronics Research Laboratory at Northeastern University. Mr. Allen is a NARTE-certified ESD control engineer and the author of 31 published papers and articles. He is an active member of the ESD Association on several standards working groups and secretary and webmaster of the local Northeast Chapter of the ESD Association. He graduated from Northeastern University with B.S.E.E, M.S.E.E., and MBA degrees. ESD Systems, 19 Brigham St., Unit 9, Marlboro, MA 01752-3170, (909) 627-8178, e-mail: ryne.allen@esdsystems.com, URL: http://www.esdsystems.com.

Gene Felder is the Corporate Product Manager of Desco Industries, Inc. (DII). Previously, he was General Manager of BW/IP International SR Engineering. Mr. Felder graduated from California State University with a B.A. in Business Administration and earned an MBA degree from the Anderson School of Management at the University of California at Los Angeles. He is a member of the ESD Association and is APICS Certified in Integrated Resource Management [CIRM]. Desco Industries Inc., 3651 Walnut Avenue, Chino CA 91710, (909) 627-8178, e-mail: gene.felder@desco.com, http://www.descoindustries.com.