From ESD With the economy steadily improving, many companies are looking for ways to increase profits and overall performance within their particular industry. The electronics industry is no exception. Many electronics companies are working towards improved quality and reliability at the same rate as improving the performance of the products they manufacture. In the latter part of 2005, the ESD Association released an “ESD Technology Road Map” in an effort to create awareness within the global electronics industry of some remarkable changes that are right around the corner.
The “Road Map” points out, in dramatic fashion, that numerous mainstream electronic parts and components will soon reach assembly factories without the same level of ESD protection installed just a few years ago. The manufacturing industry may have become a bit complacent in the past few years since many design schemes offered very good levels of ESD protection. However, the ever increasing demands for enhanced performance, speed, storage capacity, and bandwidth, along with a reduction in physical size has led to the necessary removal of on-chip protection.
Nowhere is this more evident than in the world of wireless communication devices and other portable electronic equipment. The features crammed into a pocket sized cell phone are truly amazing and many more are on the way. As consumers demand and are granted more features, manufacturers must adapt to handling increased ESD susceptibility in their parts.
The ESD Association Standards Committee is “charged” with keeping pace with the industry demands for increased performance, and is not too far away from offering the ability to determine process capability as it relates to ESD with all its peripheral ramifications. The existing Standards, Standardized Test Methods, Standard Practices and Technical Reports assist in the design and monitoring of the Electrostatic Protected Area (EPA). Most of the existing documents relate to controlling electrostatic charge on personnel and stationary work areas. However, with the ever increasing shift to automated handling, the need to evaluate and monitor what is going on inside of process equipment is growing daily. A shift is being made from Human Body Model device susceptibility as the major concern, to Charge Device Model considerations in the typical factory.
Table 1: Types of ESD Association Documents
While there has always been significant issue with machine processing, there have been very few tools available to give the ESD coordinator in the factory a methodology to conduct meaningful evaluations. Next year, this annual update should include Standards and other procedures that will allow a company to determine the level of ESD sensitivity that their process can handle reliably.
There is absolutely no question that the existing ESD Association Standards such as ANSI/ESD S20.20 (Program Development) and ANSI/ESD S541 (Packaging for Shipment) are important to industry. These documents are downloaded from www.esda.org in excess of 948 times per month. The new ESD Technology Road Map has had over 6400 downloads since it was released. The industry is paying attention. The factory Certification Registrars report strong interest in Certification to S20.20 and the world of consultants in this area report that inquiries for assistance are at an unprecedented level in recent months. Individual education also seems of interest once again with numerous individuals attempting to qualify as Certified ESD Control Program Managers.
A recently introduced educational opportunity is the ESD Device Design Professional Certification program (see Conformity, June 2005). Similar to the ESD Program Manager Certification in concept, candidates take a required number of tutorials related to electronic device and testing technologies, show work in the field and potentially write an exam (still in the planning phase). For details on this and the Program Manager Certification program, see the ESD Association web site.
A large percentage of the certification program requirements are based on Standards and the other related documents produced by the ESD Association Standards Committee. Recently released documents include a major revision of ANSI/ESD S6.1 Grounding. This important standard offers significant information related to setting up an ESD controlled environment, choosing an appropriate grounding system and advising what to do in the event a ground is not readily available.
New Standardized Test Methods include ANSI/ESD STM 11.13-2004 Two Point Resistance Measurement and ANSI/ESD STM 11.31-2001 Bags. A new Standard Practice document released this past year includes ANSI/ESD SP 15.1-2005 In-Use Resistance Testing of Gloves and Finger Cots. Recent guidance and informational Technical Reports are also available covering the following subjects: cleanrooms and air ionizers. An international version of S20.20 should be released for use by the International Electrotechnical Commission (IEC) during 2006.
Who uses standards and why? Who uses ESD standards? The list is quite broad: manufacturers, purchasers, 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? The reasons are numerous:
In the United States, the use of ESD standards continues to be voluntary. However, their use can be written into contracts or purchasing agreements between buyer and seller. In much of the rest of the world, the use of standards, where they exist, is compulsory.
General Types of Standards As recently as 1990, there were relatively few reliable ESD standards and many of them were developed for applications other than electronics. In this new century, the landscape has changed significantly with an increasing number of ESD standards developed specifically for the electronics industry.
ESD Association standards can be categorized into four main groups. First, there are those that provide ESD program guidance or requirements, such as ANSI/ESD S20.20-1999 Protection of Electrical and Electronic Parts, Assemblies and Equipment (Excluding Electrically Initiated Explosive Devices); ANSI/ESD S6.1-2005 Grounding—Recommended Practice; and ANSI/ESD S1.1-1998 Wrist Straps. These documents are classified as standards as they all have specific requirements that must be met.
A second group of documents is called standard test methods. These documents contain procedures that can be used to evaluate device sensitivity or ESD control products, materials, or processes. The procedures called out in a standard test method should provide similar test results when tested by two separate labs. Standard test methods include documents such as ESD STM5.1-2001 Device Testing—Human Body Model (HBM) Component Level and ESD STM11.3.2004 Two Point Resistance Measurement.
The third category of documents is called standard practices. A standard practice contains procedures similar to those found in a standard test method with one difference. The procedure is not sufficiently developed to ensure that two labs will get the same result when the procedure is followed. In many cases, a document is released as a Standard Practice so that industry can start to use it. The working group that issued the standard practice continues their efforts to make the test method repeatable and reproducible with the goal of eventually elevating the document to a standard test method.
Finally, the last category of standards documents includes advisories and technical reports. These types of documents are used to provide educational information to potential users. A good example is TR20.20. This document is a companion publication to ANSI/ESD S20.20-1999 and provides detailed, background information on the requirements of the standard as well as a wealth of information on ESD control issues.
Table 2: ESD Association Standards Documents
Who are the primary standards developers? Although there are a number of organizations such as IEST, IDEMA, and JEDEC involved in ESD standards development, the ESD Association has become the 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 United States on the International Electrotechnical Commission’s Technical Committee 101-Electrostatics. The ESD Association has published 27 standards documents and 16 technical reports covering material and program requirements, electrostatic sensitivity, and test methodology for evaluating ESD control materials and products.
ESD Association Advisory documents are not standards, but provide general information for the industry or additional information to aid in better understanding of association standards. ESD ADV1.0-2004 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 electronics industry. 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. ESD ADV53.1-1995 ESD Protective Workstations 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. ESD TR 20.20-2000 ESD Handbook Provides guidance that can be used for developing, implementing, and monitoring an electrostatic discharge control program in accordance with ANSI/ESD S20.20. It also includes Glossary of Terms (ESD ADV1.0-2003). This document was formerly ESD ADV2.0.
Table 3: ESD Association Advisory Documents
Traditionally, the U.S. military spearheaded the development of specific standards and specifications with regard to ESD control in the United States. Today, however, U.S. military agencies are taking a less proactive approach, relying on commercially developed standards rather than developing standards themselves.
The international community, led by the International Electrotechnical Commission (IEC), has also taken an active role in standards development. Europe’s CENELEC has issued a European electrostatic standard, EN 61340-5-1 Protection of Electronic Devices from Electrostatic Phenomena—General Requirements that was adopted as a European Norm.
Summary The ever changing and dynamic electronics world will face additional challenges as discussed in the “ESD Technology Road Map.” The technical and manufacturing communities will need to monitor processes to make sure they are capable of handling parts with greater ESD sensitivity than they have had to deal with in recent years. Keeping up with the changes in the electronics industry is a task that the ESD Association Standards Committee must face on nearly a daily basis - a daunting task for a volunteer organization. g
ESD standards are available from the following sources:
References 1. “ESD Control: A Profitable Opportunity in Tight Economic Times,” Stephen A. Halperin, Threshold, January/February 2003 (Rome, NY: ESD Association) 8-9.
The ESD Association is the largest industry group dedicated to advancing the theory and the practice of ESD avoidance, with more than 2000 members worldwide. Readers can learn more about the association and its work at www.esda.org. Special thanks to Dave Swenson for his assistance in preparing this article. © Copyright 2007 Conformity |