1. Overview of Electrostatic Discharge (ESD) Immunity Testing

The national standard for Electrostatic Discharge (ESD) Immunity Testing is GB/T 17626.2 (equivalent to the international standard IEC 61000-4-2). Electrostatic discharge (ESD) is a natural phenomenon. Experience shows that when a person walks on a synthetic fiber carpet, the friction between shoes and the carpet can cause the human body to accumulate a charge of more than 10^-6 coulombs within a few steps (depending on the resistance between the shoes and the carpet). In such a "system" (person/carpet/earth), the average capacitance is about tens to hundreds of pF, and the resulting voltage can reach up to 15 kV. Studies on ESD generated by different individuals show various current pulses, with rise times ranging from 100 ps to 30 ns. Electronics engineers have found that ESD often occurs when the human body comes into contact with semiconductor devices, potentially causing breakdown of multiple semiconductor layers and irreversible damage. ESD and the subsequent electromagnetic field changes can also disrupt the normal operation of electronic equipment.

2. Scope of ESD Immunity Testing:

This standard specifies the immunity requirements and test methods for electrical and electronic equipment subjected to electrostatic discharges from operators and nearby objects. It also defines the range of test levels and test procedures under different environmental and installation conditions.

3. Reference Standards for ESD Immunity Testing:

GB/T 4365-1995 Electromagnetic Compatibility Terminology

IEC 68-1:1998 Environmental Testing - Part 1: General and Guidance

4. ESD Immunity Test Levels:

Contact discharge is the preferred test method, while air discharge is used when contact discharge cannot be applied. The test voltages for each method are listed in Table 1. Due to differences in test methods, the voltages indicated for each method are different. The severity of the two test methods is not equivalent.

1a Contact Discharge        1b Air Discharge

Level   Test Voltage (kV)   Level   Test Voltage (kV)

1          2                          1          2

2          4                          2          4

3          6                          3          8

4          8                          4         15

*        Special                 *        Special

5. Comments on ESD Testing Standards

① The standard prioritizes contact discharge as the primary method because it involves fewer uncertainties.

② Contact discharge has an extremely steep rise time, so the discharge current waveform contains extremely rich harmonic components. Even at relatively low test voltages, it can yield more stringent results than air discharge at higher voltage levels within the same grade.