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KeyTek
Application Note ESD Background Electrostatic Discharge (ESD) is the abrupt release of charge from one object (often a person) to another. Such a discharge can permanently damage or otherwise upset the function of sensitive electronic circuits. Electronic products are tested for ESD immunity to insure their continued reliable operation if subjected to realistic levels of ESD after being placed in service. The European Union's EMC Directive mandates ESD immunity testing for virtually all electrical and/or electronic products as a condition for obtaining the CE Mark before shipping to a member state of the European Union. Applicable Standards Generic Immunity Standards, Product Standards and Product Family Standards require that ESD tests be performed in accordance with specific Basic EMC Standards: IEC 801-2, IEC 61000-4-2, or EN 61000-4-2. KeyTek's Application Note, "EMC Standards Overview," provides an overview of European Standards for electromagnetic compatibility, describes how the Standards relate to one another, and lists sources for procuring copyrighted documents.Basic EMC Standard The Basic EMC Standards for ESD define methods of generating consistently reproducible electrical stresses for test purposes. They specify capacitances and resistances to model the human body's charge storing capability and discharge impedance, respectively. This model results in a current waveform, defined in the Standards. While the Basic EMC Standard also specifies how to perform ESD testing, the Generic, Product and Product Family Standards specify the test levels and pass/fail Performance Criteria. Test Levels
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Set-Up
Coupling Methods Indirect Coupling simulates an ESD event which causes a radiated field to be emitted in the vicinity of the victim equipment. This is accomplished using Vertical Coupling Planes (VCP's) and Horizontal Coupling Planes (HCP's). Current standards require discharges be made to the edge of the VCP and surface of an HCP. Waveforms Waveform Verification Recent work by the Working Group 14.0 of the ESD Association has found that some simulators produce waveforms that are in compliance with IEC 61000-4-2, but have considerable ringing and high frequency components that do not show up with 1GHz instrumentation. These simulators may cause failures in products which would not occur if tested with a KeyTek simulator. Working Group 14.0 is preparing a document to describe waveform verification methods to allow manufacturers to verify the ESD current from simulators using high bandwidth instrumentation. Number and Rate
of Discharges For the indirect tests, 10 discharges are required to the Vertical Coupling Plane at each of 4 equipment faces (40 discharges) and then 10 discharges are required to the Horizontal Coupling Plane at 4 sides of the EUT (40 discharges). EUT Performance Criteria For ESD tests, the Generic Immunity Standards and Household Appliances Product Family Standard require that products operate as intended after the test. No degradation or loss of function is allowed below a performance level specified by the manufacturer. During the test, degradation is allowed, but not a change in the actual operating state or stored data. Refer to the tables located in the Generic, Product and Product Family Standards for specific Performance Criteria. The product cannot become unsafe under any conditions. ESD Simulators
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