Introduction to electrostatic discharge immunity test
Electrostatic Discharge Immunity Test – Taipest
**1. Scope of Electrostatic Discharge Immunity Test**
This standard outlines the immunity requirements and testing procedures for electrical and electronic equipment exposed to electrostatic discharge, either directly from an operator or from nearby objects. It also defines the test levels and procedures under various environmental and installation conditions.
**2. Reference Standards**
- GB/T 4365-1995: Electromagnetic Compatibility Terminology
- IEC 68-1:1998: Environmental Testing – Part 1: General Rules and Guidelines
**3. Overview of the Test**
The test simulates real-world conditions where devices may be affected by electrostatic discharges. For example, low humidity environments combined with low-conductivity materials like rayon carpets or vinyl clothing can increase the likelihood of static buildup.
**4. Definitions**
- **Degradation (of performance):** Any deviation from normal device performance due to ESD.
- **Electromagnetic Compatibility (EMC):** The ability of a device to function properly in its electromagnetic environment without causing interference.
- **Antistatic Material:** A material that minimizes charge generation when rubbed against similar materials.
- **Energy Storage Capacitor:** Represents the human body’s capacitance during ESD testing, either as a discrete component or distributed.
- **ESD (Electrostatic Discharge):** The transfer of electric charge between objects with different potentials.
- **EUT (Equipment Under Test):** The device being tested.
- **Ground Reference Plane (GRP):** A conductive surface used as a reference for grounding.
- **Coupling Plate:** A metal plate used to simulate ESD from nearby objects.
- **Hold Time:** The time the test voltage remains stable before discharge.
- **Contact Discharge Method:** Direct contact between the discharge electrode and the EUT.
- **Air Discharge Method:** Discharge occurs through a spark near the EUT.
- **Direct Discharge:** Applying ESD directly to the EUT.
- **Indirect Discharge:** Simulating ESD on a coupling plate near the EUT.
**5. Test Levels**
- Contact discharge is preferred; air discharge is used when contact is not possible.
- Test voltages vary depending on the method, with different severity levels.
**6. Electrostatic Discharge Generator**
The generator includes components such as a charging resistor, storage capacitor, discharge resistor, voltage indicator, and discharge cable. Key characteristics include:
- Storage Capacitor: 150 pF ±10%
- Discharge Resistance: 330 Ω ±10%
- Charging Resistor: 50 MΩ or 100 MΩ
- Output Voltage: 8 kV (contact), 15 kV (air)
- Waveform Requirements: Rise time of 0.7–1 ns, peak current up to 30 A.
**7. Test Configuration**
- Discharge to conductive surfaces and coupling plates.
- Air discharge on insulating surfaces.
**7.1 Laboratory Setup**
- Ground Reference Plane: Copper or aluminum sheet at least 0.25 mm thick.
- Coupling Plate: Same material as GRP, connected via 470 Ω resistors.
- Desktop Equipment: 0.8 m high wooden table with HCP (1.6 m x 0.8 m).
- Floor-standing Equipment: Insulated bracket to isolate from the ground.
**8. Test Procedure**
- **Environmental Conditions:** Temperature 15–35°C, Humidity 30–60%, Pressure 86–106 kPa.
- **Preparation:** Check EUT for any damage before testing.
- **Discharge Application:**
- Direct Discharge: Apply to touchable areas, using single discharges at least 10 times.
- Indirect Discharge: Apply to horizontal or vertical coupling plates.
- **Safety Measures:** Keep cables at least 0.2 m away from EUT. Ensure proper grounding.
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