ESD resistance of capacitors

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This article explains the ESD (Electrostatic Discharge) resistance of capacitors.

ESD resistance test method

When static electricity carried by the human body and equipment is discharged to the entire machine and electronic components, the impact of electromagnetic energy is increased, so the product must have a certain amount of ESD tolerance.

ESD tolerance test methods are divided into the following three types according to the model of static electricity generation: ①HBM, ②MM, ③CDM.

Among them, we will explain ①HBM, which is the most commonly used method for testing the ESD resistance of capacitors.

①HBM (Human Body Model): Test that assumes static electricity is discharged from the human body

②MM (Machine Model): Test assuming mechanical electrostatic discharge

③CDM (Charged Device Model): Test assuming electrostatic discharge from charged devices

HBM's ESD test specifications include AEC-Q200-002 and IEC61000-4-2. The HBM model specifications vary according to the specifications as shown in the following table.

The ESD test circuit and discharge current waveform of AEC-Q200-002HBM are shown in Figures 1 and 2.

(i) Switch 2 is open, switch 1 is closed, high voltage power is applied, and the charging capacitor (Cd) stores electricity.

(ii) Switch 1 is opened and switch 2 is closed, and the amount of electricity stored in Cd is applied to the capacitor (Cx) under test for testing.

※Cx: Test target capacitorCd: Charging capacitorRd: Discharging resistorRc: Protection resistor

Figure 1. HBM ESD test circuit

Figure 2. Discharge current waveform

According to AEC-Q200-002, the ESD test process of HBM is shown in Figure 3, and the level classification is shown in Table 1. According to the process of Figure 3, the test is performed, and the withstand voltage classification is classified as shown in Table 1.

Figure 3. HBM's ESD test process

Table 1. HBM's ESD test process

DC: Direct current contact discharge AD: Air discharge

Relationship between capacitor capacitance and ESD resistance

The capacitance of the capacitor under test affects the voltage generated across the capacitor.

Figure 4. HBM ESD test circuit

The relationship between the capacitance (Cx) of the capacitor under test and the voltage (Vx) generated across both ends is as follows.

When the power supply voltage (Vd) and the capacitance (Cd) of the charging capacitor are constant, the larger the capacitance (Cx) of the capacitor under test, the smaller the voltage (Vx) generated across the capacitor under test.

Therefore, the ESD resistance of a capacitor under test tends to increase as its electrostatic capacitance increases.

In reality, the performance range of withstand voltage varies depending on the design such as the type and thickness of the dielectric, and not all of them follow the trend described above.

(Reference data) ESD resistance of multilayer ceramic capacitors (GCM series)

Displays reference data on ESD resistance of multilayer ceramic capacitors (GCM series).

Figure 5. ESD test results of high dielectric constant capacitors (Vd = 25kV is the measurement range)

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