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STATIC ELECTRICITY: Denoting or pertaining to electricity at rest. How simple and inadequate this definition is of a phenomenon that creates problems which cost industry millions of dollars per year. A clearer understanding can be gained by explaining lightning. Static electricity in the atmosphere remains at rest until the potential gradient, between clouds, reaches a level that causes the insulator between clouds, in this case air, to break down or fail, and lightning is created to equalize the potential gradient. For the brief instant the lightning flashes, the static electricity is no longer at rest.
Static electricity is a well known but little understood phenomenon that affects many industries and diverse environments. It can be something of a phantom - impossible to see, touch, or smell. However, the results of static charge buildup are quite noticeable. These results include potentially dangerous electrical shocks which can cause decreases in productivity, machinery jams, fires, and explosions. Static charges can also cause severe damage to sensitive electronic components, requiring costly rework and/or field service repair.
Static electricity is a little like a bomb waiting to explode. Its energy, therefore, must be managed. The relevant question is: How can a material respond to electrical energy as a shock absorber reacts to mechanical energy? Or, foam rubber to audio energy? Or, more specifically, how far should resistance to electron flow be lowered?
The topic of electrostatic discharge (ESD) with regard to plastic packaging of electrically sensitive devices is technically complex. A large amount of research has been performed in this area, and experts are still conducting research to further the understanding of the phenomena involved and to develop more reliable and useful testing methods. However, the basic tenets of ESD protection relating to plastic packaging have been well established and are currently being utilized by industry. There are 2 U.S.-based organizations that have published industry standards relating to the ESD requirements for packaging materials of electrically sensitive devices. A large industry has developed worldwide which is dedicated to providing ESD-safe packaging materials. Yet, with the body of scientific knowledge that exists, the availability of industry standards, and the existence of mature industries that produce and use ESD-protective materials, there is still some confusion in industry at large concerning terminology and appropriate test methods for particular applications. The reasons for this are unclear. Perhaps part of the reason is that the topic is technically complex. Another reason is that there are 2 similar, but unaligned, industry standards. And lastly, it is because the ESD-related industry standards do not dictate certain material properties for specific applications. Whatever the reason or reasons may be, there is definitely a need for more education about ESD material properties throughout the industry. The purpose of this document is to point out, and hopefully clarify, some of the more confusing ESD issues and to direct the reader to the ESD resources that are available. |
