IEC 61000-4-2 outlines the international immunity standard for electronic equipment ability to withstand ESD generated from a human body or metal objects with a built up static charge. The standard assumes that the source is an electrified human body discharge, and testing simulates the current waveform generated in those conditions.
|Level||Test Voltage (Contact Discharge)||Test Voltage (Air Discharge)|
Discharge Current Waveform
The ESD discharge simulator (ESD Gun) must meet the following specifications:
- Energy accumulation capacity: 150pF (typical)
- Discharge Resistance: 330Ω (typical)
- Charging Resistance: 50MΩ – 100MΩ
- Output Voltage: 8kV for contact discharge, 15kV for air discharge
- Tolerance: ±5%
- Polarity: Positive and Negative
- Hold time: >= 5 Sec.
Testing Your ESD Gun
The following characteristics in the table below must be verified to ensure proper test results.
|Level||Indicated Voltage||1st peak Current of discharge (±15%)||Rise Time (±25%)||Current at 30ns (±30%)||Current at 60ns (±30%)|
To check an ESD simulator’s output, you must measure the waveform of the resulting current across a low-impedance, high-frequency resistive shunt connected to ground. The target mounts in the center of a 1.2-m2 ground plane and must have VSWR of less than 1.22 and an insertion loss of less than 0.3 dB up to 4 GHz.
IEC 61000-4-2 also specifies that you place the measurement oscilloscope inside a Faraday cage to shield it from the radiated ESD pulse. You will also need good-quality low-loss cables between the target, attenuators, and the oscilloscope. To comply with the IEC standards you should keep the total cable length less than 1 m, and a double-shielded cable that prevents signal leakage from affecting your measurement is strongly recommended.
EUT Test Setup
The direct discharge test simulates the human body model of electrostatic discharge and must be set up to recreate similar conditions. It is important to make sure that you have the proper grounding system in place before you begin testing. When using a table top for testing, you want to have a horizontal coupling plane on top of the table but below an insulation sheet. This should be connected to a ground reference plane on the floor using a 2 x 470kΩ bleed resistor cable as shown:
If the EUT is too large for a table top, place the EUT on an insulation pallet that is at least 0.1m in height. For the indirect contact discharge part of the test, a vertical coupling plane should be set up 10cm from the EUT, and also connected to the ground reference plane using the bleed resistors. Once set up, a power supply should be connected to the EUT and ESD gun. It is important to make sure that the room where the test is conducted is at a temperature of 15°C to 35°C and relative humidity is between 30% and 60%.
The test procedure is rather simple. For direct discharge, place the ESD gun to the point of test on the EUT, and discharge at 1 second intervals. This should be performed at least 10 times at both positive and negative polarities, and results recorded. For an indirect discharge test, the same process is repeated except that the discharge goes to the vertical or horizontal coupling plane, rather than directly to the EUT. Multiple discharge points may be required for testing, depending on the EUT.
The results are classified in 4 ways:
- Normal operation within tolerance of specification
- Temporary degradation or loss in operation or function, which is able to be recovered by self-recovery function
- Temporary degradation or loss in operation or function, which needs to be recovered by user intervention or system reset.
- Damage of the system or software, and unrecoverable degradation and loss of function or data.
More on ESD Testing
|IEC 61000-4-2||150pF/330 Ohm|
|ISO 10605||150pF/2000 Ohm
|ANSI C63.16||150pF/330 Ohm
|JASO D001-87||150pF/500 Ohm|
|Chrysler PF9326/LP388||100pF/500 Ohm|
EMC Lioncel ESD Gun Specification
|Discharge voltage||Positive/negative/automatic change|
|Discharge capacitance||150pF±10%，(available for change)|
|Discharge resistance||330Ω±5%，（available for change）|
|Discharge current rise-up time||0.7~1ns|
|Test fuction||Single time, counting, 20pps, Air-discharge, Contact-discharge, IEC Level built in|
|Power supply||AC220V 50/60Hz|
|Ambient conditions||Operation: ＋15～35℃, 25～75％（non-condensing）, 86kPa~106kPa|