What is Electro-Static Discharge (ESD)?

Everyone has experienced ESD at one time or another. That joyous little jolt you get after walking across the carpet and touching the door knob or something else. Everyone learned in grammar school that opposites attract. The same is true with electric charges. When there is a build up of negative charge on one body and a positive charge exists on another, they want to be together and neutralize. The process of seeking out the opposite charge and neutralizing is the phenomenon we call ESD. On a larger scale we call this process lightning. ESD involves thousands of volts (10³), milli-joules (10^-3) of energy transferred in nano-seconds (10^-9) producing Mega-watts (10⁶) of power. In simple terms, a small amount of energy very fast produces a lot of power. This very fast event finds the weak points in electronics and damages them. Sometimes the damage just weakens the electronics thus shortening the life span. Other times ESD can destroy the functionality immediately.

ESD Handling

The ESD Association has developed standards for handling ESD sensitive devices. These procedures control individual component exposure to ESD threat or events as the parts arrive and are handled throughout the facility. They have developed the ANSI/ESD S20.20 Protection of Electrical and Electronic Parts, Assemblies and Equipment (Excluding Electrically Initiated Explosive Devices) standard along with many other standards that detail proper work stations, transport enclosures, device classification, monitoring equipment and many other aspects of component and equipment handling.

ESD Equipment Design/Testing

Design techniques to improve an electronic equipment’s immunity to ESD events include enclosure design, surge protection on input lines/pins, connector designs, etc. The European Community has developed qualification test procedures and limits for electronic equipment. These qualification test procedures and limits can be found in EN61000-4-2. They include Direct Injection techniques, Air Discharge techniques, and Radiated Field techniques.

ESD Component Design/Testing

The ESD Association has developed standards for component classification and testing based on various ESD source models. These models include Human Body Model, Machine Model, and Charged Body Model. The various models are based on activities that create ESD events found in normal every day handling of components.

CONCLUSION

ESD problems range from low yields in manufacturing, intermittent disturbances, to compliance with international standards. Practical Engineering, PC is ready to help.

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