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50 Conformity September 2008
As 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:
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)
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).
customers, and meet the specific requirements of individual
manufacturers.
(As an aside, in addition to simulators being developed for
testing finished products for the effects of ESD, manufacturers
of semiconductor devices were developing their own range of
standards to deal with ESD in the manufacturing, distribution
and assembly processes. This activity, of course, drove the
development of early manual and automated testers3 for chips
and is the subject for a later article.)
The European Union – Briefly
In the early 1950s, Germany, France, Italy, the Netherlands,
Belgium and Luxembourg formed the basis of today’s
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