Testing and measurment techniques---Electrostatic discharge immunity test
- Taipest
1 Electrostatic discharge immunity test range:
This standard stipulates that electrical and electronic equipment is subject to immunity requirements and test methods directly from the operator and electrostatic discharge to adjacent objects. It also specifies the range and test procedures for the test levels under different environmental and installation conditions.
2 Electrostatic discharge immunity test reference standard:
GB/T4365-1995 Electromagnetic compatibility terminology IEC 68-1:1998 Environmental testing Part 1: General rules and guidelines
3 Overview of Electrostatic Discharge Immunity Test
This standard refers to the device in the electrostatic discharge environment and installation conditions. system. Subsystems and external devices. For example, low relative humidity, using low conductivity (rayon) carpet. Vinyl clothing, etc.
4 Electrostatic discharge immunity test definition:
4.1 Reduce degradation (of performance)
Undesired deviation of performance and normal performance of the device or system
4.2 Electromagnetic compatibility (EMC) electromagnetic compatibility
The ability of a device or system to function properly in its electromagnetic environment without posing unacceptable electromagnetic disturbances to anything in the environment
4.3 antistatic material
A material that produces the least amount of charge when rubbed or separated from the same material or similar materials
4.4 energy storage capacitor
A capacitor in an electrostatic discharge generator that represents the capacitance of a human body when charged to a test voltage value. It can be a discrete component or a distributed capacitor.
4.5 ESD electrostatic discharge
Electrostatic discharge
4.6 EUT equipment under test
Test equipment
4.7 Ground Reference Plane (GRP) ground reference plane
a conductive plane whose potential is used as a common reference potential
4.8 coupling plate coupling plane
a piece of metal or metal plate that is discharged to simulate electrostatic discharge of an object in the vicinity of the device under test
HCP: horizontal coupling plate; VCP: vertical coupling plate
4.9 hold time holding time
Before the discharge, the test voltage drops by no more than 10% due to leakage
4.10 electrostatic discharge; ESD
Charge transfer caused by objects with different electrostatic potentials being close to each other or in direct contact
4.11 immunity (of disturbance)
The ability of the device or system to face electromagnetic disturbances without degrading operational performance
4.12 Contact discharge method contact discharge method
A test method in which the electrode of the test generator is kept in contact with the device under test and is excited by a discharge switch in the generator.
4.13 air discharge method
A test method for bringing the charging electrode of the test generator close to the device under test and exciting and discharging the device under test by the spark
4.14 direct discharge direct application
Directly discharge the device under test
4.15 indirect discharge indirect application
Discharge the coupling plate near the device under test to simulate the discharge of personnel to objects near the device under test
5 Electrostatic discharge immunity test level:
Contact discharge is the preferred test method. Air discharge is used when contact discharge cannot be used. The voltage of each test method is listed in Table 1. The voltages shown in each method are different due to the difference in test methods. The severity of the two test methods does not indicate equal 1a contact discharge 1b air discharge level test voltage KV level test voltage KV1 2 1 22 4 2 43 6 3 84 8 4 15* special * special
6 Electrostatic discharge immunity test generator:
The test generator mainly comprises: a charging resistor R; a storage capacitor Cs; a distributed capacitor Cd; a discharge resistor Rd;
Voltage indicator; beginning of discharge; replaceable discharge electrode tip; discharge loop cable; power supply unit
6.1 Characteristics of Electrostatic Discharge Generator
specification:
-------- Storage Capacitor (Cs+Cd) 150pF±10%--------Discharge Resistance (Rd) 330ohm; ±10%-------Charging Resistor (Rc) 50Mohm; and 100Mohm; ------- output voltage contact discharge 8KV; air discharge 15KV------- output voltage indication tolerance ± 5% ------- indirect voltage Polarity positive and negative ------- hold time at least 5S------- discharge, operation mode Single discharge test generator cable in the discharge circuit is generally 2m long, its composition should make the generator meet Waveform requirements, it should have sufficient insulation to prevent static discharge current from flowing through its port to the person or conductive surface
6.2 Verification of electrostatic discharge generator characteristics
Waveform parameters:
Level 1 2 3 4 indicates the first peak current of the voltage KV 2 4 6 8 discharge (±10%) A 7.5 15 22.5 30 The rise time at the beginning of the discharge operation tr ns 0.7~1 0.7~1 0.7~1 0.7~1 Current at 30ns (±10%) A 4 8 12 16 at 60ns (±30%) A 2 4 6 8
7 Electrostatic discharge immunity test configuration
A) discharge to the conductive surface and to the coupling plane; B) air discharge on the insulating surface.
7.1 Configuration of laboratory tests
The ground of the laboratory shall be provided with a ground reference plane, which shall be a thin metal sheet of copper or aluminum with a minimum thickness of 0.25 mm. Other metals may be used but they have a thickness of at least 0.65 mm.
The minimum size of the ground reference plane is 1*1m. The actual size depends on the size of the equipment under test, and each side should extend at least 0.5m beyond the equipment under test or the coupling board and connect it to the protective earthing system.
The coupling plate should be of the same metal and thickness as the ground reference plane, and a 470 Ω resistor cable at each end should be connected to the ground reference plane. These resistors should withstand the discharge voltage when the cable is placed on the ground reference plane. And has good insulation to avoid short circuit to the ground reference plane.
7.1.1 Desktop equipment
The test configuration consisted of a 0.8m high wooden table placed on a grounded reference plane
Place the horizontal coupling plate (HCP) area of ​​1.6m*0.8m, and isolate the test equipment and cable from the coupling plate with a 0.5mm thick insulating gasket.
If the EUT is too large to maintain a minimum distance of 0.1 m from each side of the horizontal coupling plate, another identical horizontal coupling plate should be used with a distance of 0.3 m from the short side of the first block. However, the table must be enlarged at this time. Or use two tables, these horizontal coupling plates must be welded together, and connected to the ground reference plane via another resistance cable
7.1.2 Floor-standing equipment
The test equipment and the cable are separated from the ground reference plane by an insulating bracket with a thickness of about 0.1 m.
8 Electrostatic discharge immunity test procedure
8.1 Climate conditions:
------- Ambient temperature: 15 ° C ~ 35 ° C ------- Relative humidity: 30% ~ 60% ------- Atmospheric pressure: 86Kpa ~ 106Kpa
8.2 Examination of the equipment under test
8.3 Implementation of the test
8.3.1 Discharge directly applied to the device under test
Electrostatic discharge is only applied to the points and surfaces that may be touched by the operator when the test equipment is normally used.
In order to determine the critical value of the fault, the test voltage should be gradually increased from the minimum value to the selected test voltage value, and the final test value should not exceed the specification value of the product to avoid damage to the equipment.
The test shall be carried out in a single discharge. At least 10 single discharges (most sensitive polarity) shall be applied at the preselected point.
The time interval between consecutive single discharges is recommended to be at least 1 s, but a longer interval may be required to determine if the system will fail.
The electrostatic discharge generator should be kept perpendicular to the surface on which the discharge is applied to improve the repeatability of the test results.
When discharging is performed, the distance between the discharge circuit cable of the generator and the device under test is at least 0.2m.
In the case of contact discharge, the top of the discharge electrode should be in contact with the device under test before the start of the operational discharge.
For surface painting, the following procedures should be used:
If the equipment manufacturer does not indicate that the paint film is an insulating layer, the electrode tip of the generator should be inserted into the paint film to make contact with the conductive layer. If the manufacturer specifies that the paint film is an insulating layer, only air discharge should be performed. Contact discharge test should be carried out.
In the case of air discharge, the circular discharge head of the discharge electrode should be as close as possible and re-touch the device under test. After each discharge, the discharge electrode of the ESD generator should be removed from the device under test and then triggered again. The generator, for a new single discharge, this procedure should be repeated until the discharge is completed. In the case of the air discharge test, the beginning of the discharge used as the contact discharge should be closed.
8.3.2 Indirect applied discharge
8.3.2.1 Horizontal coupling plate under the device under test
Applying at least 10 single discharges to the horizontal coupling plate at some point on each side of the device under test
In the case where the discharge electrode touches the coupling plate, the electrostatic discharge generator should be placed vertically at 0.1 m from the device under test.
8.3.2.2 Vertical coupling plate
Apply at least ten single discharges to the center of one vertical side of the coupling plate. The coupling plate with a size of 0.5 m*0.5 m should be placed parallel to the test equipment and kept at a distance of 0.1 m.
The discharge should be applied to the coupling plate. By adjusting the position of the coupling plate, the test equipment is subjected to the discharge test at different positions on all four sides.
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