Conformity Magazine - September 2008 - (Page 50)

s early as the 1400s, it was recognized that static could be a problem where black gunpowder was stored in dry environments. By the mid 1800s, paper mills were using steam and other methods to eliminate static from the paper going through the drying process. Although the earliest example of an electrostatic generator that we could find was one invented by Otto von Guericke (1602-1686), the device was more of an interesting experiment than a useful tool. It wasn’t until the era of solid state electronics that the need for an electrostatic generator for product testing became apparent. Early ESD Standards and Simulators By the 1970s, everyone had their own idea about how ESD testing should be done. There were no dominant international or industry standards for ESD testing and, as a result, individual companies developed their own. Most everyone agreed that a tester should consist of a charged capacitor to model the human body capacitance, plus a discharge resistor to represent a person’s skin resistance, but there was little agreement about what values should be used. Capacitor values ranged from about 100pF to 1000pF, with resistors from less than 100 ohms to several thousand ohms. Further, the subtleties of building generators to produce very fast, high voltage pulses weren’t clearly understood by equipment manufacturers, and the scopes and measurement equipment of the day weren’t capable of accurately showing what these early generators were producing. The result was that, even when the same values for capacitance and resistance were used, test repeatability and reproducibility were extremely poor. By the late 1970s and early 1980s, some degree of standardization came about in the computer industry in two basic ways: A • First, a commercially available simulator became available that was adopted by many large computer manufacturers1; and • Second, these computer manufacturers began forcing ESD testing requirements on their suppliers These two events resulted in a broad base of companies using a common model for ESD testing of electronic products, but there were still problems with reproducibility and repeatability of tests. In addition, there were lingering questions of just how realistic these tests were. Did they actually represent real world ESD events? And, if not, what changes should be made? In addition to the de facto standard based on an available simulator that was being used by mainframe computer manufacturers, industry, national and international groups such as NEMA (National Electrical Manufacturers Association), ANSI (American National Standards Institute), and the IEC (International Electrotechnical Commission) began working to develop industry-wide standards groups to consolidate testing in their respective arenas. What was to become the most widely recognized of these was an IEC standard, IEC 801-2, first published in 1984 as part of a series of standards to address EMC (Electromagnetic Compatibility) for Industrial-Process Measurement and Control Equipment. During this period of dozens of ESD standards and test methods being used, a revolutionary kind of ESD simulator was developed that would allow a user to have multiple discharge “networks,” each consisting of different capacitorresistor combinations to meet individual industry standards2. This innovation addressed the growing problem of having to do different kinds of ESD testing for different customers. A manufacturer of power supplies might have to do ESD testing to IEC standards for the international market, TIA standards for the telecom industry, TUV standards for German Figure 1: An early ESD simulator (photo from Testwave LLC help@testwave.com) 50 Conformity September 2008 Figure 2: An ESD simulator with multiple discharge networks designed in the 1980s to meet the various test standards of the time (photo courtesy of Thermo Fisher Scientific).

Table of Contents Feed for the Digital Edition of Conformity Magazine - September 2008

Conformity Magazine - September 2008 Contents Editor’s Note Commission Adopts Regulations for Internet-Based TRS Services Another Company Fined for Non-Compliance with HAC Requirements FCC Extends “Do-Not-Call” Registry Compliance Requirements Marketing Company Gets $1.4 Million Fine for Junk Faxes EU Commission Codifies Directive on TTE Market Competition EU Commission Releases Updated Standards List for the R&TTE Directive Updated Standards List for the “New” Low Voltage Directive Released New Standards List Released for the EU’s Machinery Directive The ESD Association: Voluntary Standards in Action ESD Open Forum Medical EMC Standards: Towards the 4th Edition of IEC 60601-1-2 iNARTE Informer Pre-Pulse Voltage in the HBM ESD Model Digital Interfaces and EMC Performance ESD Design Buyer’s Guide Product News Commission Publishes Updated Standards List for the EU’s Personal Protective Equipment Directive FDA Links “Human Factors” to Adverse Events with Medical Devices CPSC Actions in the News IEC Standards Update UL Standards Update Product Reviews Telcordia Standards Update From Our “You Can’t Make This Stuff Up” Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity Magazine - September 2008

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