Since electronic equipment was first developed, static electricity has been a source of problems for users and designers. In the last few years, however, electrostatic discharge (ESD) has become a source of major problems. This has occurred because newer electronic devices, such as integrated circuits, are much more susceptible to ESD problems than previous devices, such as vacuum tubes. Another trend compounding this ESD susceptibility problem is the spread of sophisticated equipment into home and office environments where ESD is quite common. Unfortunately, this increase in the occurrence of ESD problems has not been accompanied by a corresponding increase in knowledge about ESD. Today, in the electronics industry, there is probably no other area which is so poorly understood as ESD. Most engineers view the subject of ESD as black magic, and design for prevention of ESD problems as a black art. As a result, a typical engineer takes few conscious design steps to prevent ESD problems. When problems do occur, solutions are randomly applied until the symptoms go away. In many, if not most, cases, the designer doesn't really understand why some solutions fail and others work. Even worse, designers are often not sure whether the problem has really been solved, because they don't understand how to perform accurate verification tests. Part of this confusion occurs because many engineers attempt to treat ESD as just another form of electromagnetic interference (EMI). While it is true that ESD generates EMI, ESD is not merely EMI. In addition to generating EMI, ESD also directly injects charge into the victim equipment. This direct charge injection results in several special problems that do not occur with normal EMI. In some situations, normal EMI solutions may actually aggravate ESD problems.
This book was written to take the mystery out of ESD. It explains how ESD is generated, and how it affects electronic equipment. This explanation brings ESD out of the realm of black magic and into the sphere of science. Even more important, this book explains how to design equipment to prevent ESD problems. This discussion of ESD design solutions not only includes design guidelines, but explains why they work. It also exposes myths that have developed about ESD and why they are incorrect. Finally, this book discusses the methods of testing for ESD problems. This discussion covers not only the test hardware, but also test procedures and methods that ensure meaningful results. The information contained in the following pages should help the reader prevent many (if not most) ESD problems.
