The full application of ANSI/ESD S20.201 or IEC61340-5-12 coupled with a complete understanding of the content of the standards, will lead to a state-of-the-art ESD control program. The standards have evolved over the last several decades based on the experiences of not only the contributing authors but also of those that have used the standards. The standards do not provide a “cookbook” or “set of recipes”, but rather expect the implementor to have a thorough understanding of both their own manufacturing process as well as the electrostatic phenomena that impact product yields. Finally, they include an understanding of where in the process ESD damage is most likely to occur as well as mitigation techniques that are required prior to designing an ESD safe manufacturing environment. This is a significant task and does require the appropriate expertise to do this successfully.
An excellent source of training for ESD control program development and management is through the ESD Association (ESDA) education and certification processes. The ESDA ESD Certified Professional Program Manager curriculum provides much of the information an ESD control program implementor needs to identify, install, maintain, verify, and adjust regarding electrostatic considerations in a facility. In addition to the curriculum, an ESD program manager needs relevant experience. It is wise for the new program implementor to lean heavily on the experiences of the Program Manager instructors as they all have considerable field expertise in their subject areas.
The analysis of electrostatic issues in a facility requires the use of a variety of instruments and equipment. All the phenomena related to electrostatics can be measured and for the most part can be quantified. However, developing an understanding of the values obtained in any given measurement takes time and experience. The standards and test methods can only provide general guidelines based on the experiences of the authors. The limits provided in the ANSI/ESD S20.20 document are generally applicable for most ESD control programs. However, if the devices being handled in a facility are more sensitive than those referenced in the S20.20 standard, adjustments may need to be done to protect these products. An understanding of where in the process ESD threats can occur and what influences those threats can have is important. This understanding is needed to ensure the proper use of electrostatic mitigation techniques and the proper installation of equipment. It is very easy to implement ESD control items, materials, and equipment to address a perceived electrostatic problem. However, without an understanding of root cause of ESD damage, these implementations may do little to actually mitigate ESD problems.
Most electronic production facilities today are automated so there is very little human interaction with the ESD sensitive devices. Thus, the ESD risk has shifted from personnel handling of devices to machines posing the larger threat. Fortunately, the tool manufacturers (surface mount assembly, automated handler manufacturers for example) have learned a lot about the interaction of their tools with ESD sensitive devices. Measurement of electrostatic charging between process steps, called “transitional analysis” by some practitioners3, will help locate areas that may need attention. The careful measurement and control of electrostatic fields, electrostatic surface potentials, discharge events, and point-to-point resistance within equipment will go a long way towards establishing the process capability of a production line. It remains an important requirement that personnel are properly grounded when they handle unprotected ESD sensitive parts so they are not a source of ESD. One of the most important test procedures today involving personnel is the walking voltage test defined in ANSI/ESD STM97.24. This test method and variations have been used successfully to evaluate personnel voltage in activities such as walking when they cannot be grounded by any another method. Furthermore, it verifies that the ESD footwear and floor can effectively ground personnel while they are moving about the facility. The procedure has also been used to measure the voltage level on moving equipment such as carts and trolleys, mobile shelving, hospital beds and many other items used in electrostatic protected areas.
What is involved in the “state-of-the-art ESD control” today? Education, training and experience for the ESD control practitioner are the most important elements. Learning to use the available analytical instruments and tools, and developing an understanding of the measurement results, are all required to implement the practical aspects of the important ESD control program standards.
Endnotes
- ESD Association Standard – For the Development of an Electrostatic Discharge Control Program for – Protection of Electrical and Electronic Parts, Assemblies and Equipment (Excluding Electrically Initiated Explosive Devices),
http://www.esda.org. - IEC International Standard – Part 5-1 – Protection of electronic devices from electrostatic phenomena – General requirements, http://www.iec.ch.
- “Process Capability & Transitional Analysis,” Stephen Halperin, SH&A Ltd., Ronald Gibson, Celestica Inc., John Kinnear, Jr. IBM, Proceedings 2008 EOS/ESD Symposium, page 148.
- ESD Association Standard Test Method – for the Protection of Electrostatic Discharge Susceptible Items – Floor and Materials and Footwear – Voltage Measurement in Combination with a Person, http://www.esda.org.
David E. Swenson retired in 2003 after 35 years of service from 3M. While at 3M he had responsibility for new packaging material development and application, training of 3M personnel worldwide and providing application assistance to users of static control products globally with particular emphasis on Asia Pacific and Japan. Dave and his wife Geri established a new company, Affinity Static Control Consulting, LLC in 2003. Dave has been a member of the ESD Association since 1984 and has served in many capacities including 1997 Symposium General Chair and president of the Association in 1998 and 1999 and again in 2008 and 2009. He was re-elected to the Board of Directors for a 5th term from 2014 to 2016 and is currently appointed to the Board to assist with technical inquiries. Dave was presented with the highest award of the ESD Association, the “Outstanding Contributions Award” in 2002, the Standards Committee “Joel P. Weidendorf Memorial Award” in 2004 and the Association “Edward G. Weggeland” Memorial Award in 2014. He is a member of the Standards Committee serving several Working Groups and the ANSI/ESD S20.20 Standard Task Team. Dave also serves as Treasurer and Information Liaison of the Texas Chapter of the ESD Association; he is a member of the Electrostatic Society of America, IMAPS, the UK Institute of Physics and is a US Expert to IEC TC101, Electrostatics. In addition, he is the convener of Joint Working Group 13 between TC101 and TC40 (Capacitors and Resistors).
Founded in 1982, EOS/ESD Association, Inc. is a not for profit, professional organization, dedicated to education and furthering the technology Electrostatic Discharge (ESD) control and prevention. EOS/ESD Association, Inc. sponsors educational programs, develops ESD control and measurement standards, holds international technical symposiums, workshops, tutorials, and foster the exchange of technical information among its members and others.
