What is ESD?

ESD (Electrostatic Discharge Immunity Test) is an ESD (Electrostatic Discharge Immunity Test) that simulates the discharge generated when an operator or object comes into contact with the equipment and the discharge from a person or object relative to adjacent objects, to detect the anti-interference ability of the tested equipment against electrostatic discharge.

The following content is quoted from the regulations and norms of GB/T 7626.2-2018

The requirements for electrostatic discharge immunity test are indirect discharge and direct discharge. Direct discharge includes (contact discharge/air discharge).

Indirect discharge

The discharge of objects around the test equipment is simulated by using an electrostatic discharge generator to simulate the contact discharge mode of the coupling plate for objects placed or installed near the test equipment.

1. The horizontal coupling plate under the test equipment

Discharge to the horizontal coupling plate should be applied to its edge in the horizontal direction.

At least 10 single discharges (with the most sensitive polarity) shall be applied to the edge of the horizontal plate at a distance of 0.1m opposite the center point of each unit of the test equipment (if applicable). During discharge, the long axis of the discharge electrode should be in the same plane as the horizontal coupling plate and be perpendicular to the edge of the horizontal coupling plate.

Before the discharge switch is closed, the discharge electrode should be in contact with the edge of the horizontal coupling plate. Some product standards may require that discharge tests be applied to all surfaces of the tested equipment.

2. Vertical coupling plate

At least 10 single discharges (with the most sensitive polarity) should be applied to the center of one vertical side of the coupling plate. The coupling plate with dimensions of 0.5m x 0.5m should be placed parallel to the test equipment and kept at a distance of 0.1m from it.

Discharge should be applied to the coupling plate. By adjusting the position of the coupling plate, different positions on all four sides of the tested equipment can be subjected to discharge tests. The placement of the vertical coupling plate is considered to cover the 0.5m x 0.5m surface of the test equipment.

Direct discharge：

Selection of direct discharge points

Discharge point (contact/air) discharge type selection：

Erection requirements：

1.A non-conductive table placed at a height of (0.8±0.08)m on the grounding reference plane is required.

2. The size of the horizontal coupling plate (HCP) to be placed on the table is (1.6 ± 0.02)m ×(0.80.02)m. The test equipment and cables should be isolated from the coupling plate by an insulating support with a thickness of (0.5±0.05)mm.

Note: This installation diagram shows the grounding equipment installation diagram

Requirements for the installation of ungrounded equipment

The test layout described in this article is applicable to the installation specifications or design of equipment or equipment components that are not connected to any grounding system. Equipment or equipment components, including portable battery-powered devices (internal and external) with or without chargers (power cords not grounded) and double-insulated devices (Class I devices).

Basic principle: Ungrounded equipment or ungrounded components of equipment cannot discharge by themselves like Class I power supply equipment. If the charge is not eliminated before the application of the next electrostatic discharge pulse, the accumulated charge on the test equipment or its components may cause the voltage to be twice the expected test voltage. Therefore, after several electrostatic discharges, the insulator capacitance of the double-insulated equipment may be charged to an abnormally high level and then discharged at the insulation breakdown voltage with high energy.

(Air discharge or contact discharge) Before applying each electrostatic discharge pulse, the charge on the test equipment should be eliminated.

Note: This installation diagram shows the installation of ungrounded equipment

Test requirements:

Check the environmental temperature and humidity before the test.

Ambient temperature: 15 to 35 degrees

Environmental humidity: 30% - 60%

Atmospheric pressure: 860-1060mbar

1.The test should be conducted in the form of a single discharge. At least 10 single discharges should be applied at the preselected point, and the most sensitive polarity should be applied. If there are any doubts about the test results, the number of discharges should be increased. The time interval between two separate discharges should be at least 1 second. If the system response time is long, an even longer time may be required. The electrostatic discharge generator should be kept perpendicular to the surface where discharge is carried out. During discharge, the distance between the discharge circuit cable and the tested equipment should be at least 0.2m, and the operator must not hold the discharge circuit cable.

2. In the case of contact discharge, the tip of the discharge electrode should touch the test equipment before operating the discharge switch, and the discharge head should be 90° perpendicular to the discharge point. If the equipment manufacturer does not specify that the paint film is an insulating layer, the electrode heads of the generator should be inserted into the paint film to make contact with the conductive layer. If the manufacturer indicates that the paint film is an insulating layer, only air discharge should be conducted, and contact discharge tests should not be carried out on such surfaces.

3. In the case of air discharge, the discharge head should approach and touch the test equipment as quickly as possible (without causing mechanical damage). After each discharge, the discharge electrode should be removed from the test equipment, and then the electrostatic discharge generator should be retriggered for a new single discharge. This process should be repeated until the entire test is completed.

Note: For ungrounded equipment: (air discharge or contact discharge), the charge on the tested equipment should be eliminated before applying each electrostatic discharge pulse, and then the next discharge should be carried out.

Electrostatic discharge requirements: The test levels of electrostatic discharge tests are contact discharge at 2kV, 4kV, 6kV, and 8kV. Air discharge: 2kV, 4kV, 8kV, 15kV. For general consumer electronic devices, Internet of Things devices and other products, a contact discharge test of ±4KV can pass Grade B, and an air discharge test of 8KV can pass Grade B. For details, please refer to GB/T 9254.2-2021

The test results should be classified based on the phenomenon of functional loss or performance degradation of the tested equipment during the test. The relevant performance levels shall be determined by the equipment manufacturer or the user, or agreed upon through consultation between the product manufacturer and the purchaser. It is recommended to classify according to the following requirements:

a) The performance is normal within the limits stipulated by the manufacturer, the consignor or the purchaser;

b) Temporary loss or reduction of function or performance, but self-recovery after the harassment stops, without the need for operator intervention:

c) Temporary loss or reduction of function or performance, but requires operator intervention to restore;

d) Irreversible functional loss or performance degradation caused by damage to the hardware or software of the equipment, or data loss:

The technical specifications proposed by the manufacturer can stipulate that certain influences on the tested equipment are unimportant and thus acceptable test influences.

This classification can be used by the professional standardization technical committees responsible for the general standards, product standards and product category standards of the relevant products as guidelines for clearly expressing functional guidelines. When there are no appropriate general, product or product class standards, it can serve as a framework for performance specifications negotiated between manufacturers and purchasers.

Source: Official WeChat account of Shenzhen Qianhong Electrical Testing Co., LTD