ESD testing is conducted to check the quality of the operation of an Equipment Under Test (EUT) when subjected to an electrostatic discharge. This testing is used to check the performance of the EUT for personnel static charges as well as indirect charges i.e. static charge from personnel to EUT through some other object in its proximity. Personnel handling the devices carry static charges of some amount which is capable to damage most types of semiconductors. 

Static charges can have a magnitude high enough to fire up sensitive circuits causing to malfunction or even damage to the system. Hence a device with proper ESD shielding is always more reliable for accurate results.

Which EMC Standard is used for ESD Immunity Testing?

The IEC 61000-4-2 is used for ESD Immunity testing. It is an electromagnetic standard that specifies the limits, requirements, and test methods for electrical and electronic equipment subjected to static electricity discharges, from operators directly, and from personnel to adjacent objects. All people carry static electromagnetic discharge that gives rise to transient currents and electromagnetic fields that can interfere with electrical and electronic equipment. Hence, this standard for established to ensure that the equipment will work reliably and efficiently despite the static interferences in their work environment.

The standard has defined four levels of ESD protection, using two different testing methods. The first is the contact discharge and the second is air discharge. The contact discharge involves sending an ESD pulse directly from the ESD test gun that is touching the equipment under test (EUT). Air discharge is used for cases where contact discharge testing is not possible. In the air discharge test, the ESD test gun is brought close to the EUT until a discharge occurs.

What Equipment is used for the ESD Immunity Testing?

The following is the equipment required for ESD Immunity Testing:

• EUT
• ESD Gun
• Ground Reference Plane (GRP)

What is the Test Method used for ESD Immunity Testing?

An ESD gun is used to conduct air discharges and contact discharges. Each test voltage is applied to the EUT with a minimum interval of one second between every two consecutive test discharges. At least 10 discharges should be applied for each polarity. For each test point, each test discharge should be started from the lowest test voltage (±2 kV) and increased to the maximum test discharge. All four sides of the EUT must be tested.  The EUT is to run on the normal mode with its loads to check for degradation in the functioning during the testing. 

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