According to the different ways of generating static electricity and the damage modes to the circuit, there are usually four test methods: Human-Body Model (HBM), Machine Model, Charge-Device Model (CDM), Field-Induced Model (FIM).

1. Human Body Model (HBM)
Of course, it is the friction of the human body that generates charges that suddenly touch the charges released by the chip, causing the chip to burn and break down. This is why people often get electric shocks when they touch others in autumn. The industry also has traces of the ESD standard for HBM (MIL-STD-883C method 3015.7, equivalent human body capacitance is 100pF, equivalent human body resistance is 1.5Kohm), or the international electronics industry standard (EIA/JESD22-A114-A) also has regulations. If it is MIL-STD-883C method 3015.7, it stipulates that less than <2kV is Class-1, 2kV~4kV is Class-2, and 4kV~16kV is Class-3.

2. Machine discharge mode (MM)
Of course, the static electricity generated by the movement of the machine (such as a robot) touches the chip and is released by the pin. The substandard is EIAJ-IC-121 method 20 (or standard EIA/JESD22-A115-A), the equivalent machine resistance is 0 (because of metal), and the capacitance is still 100pF. Since the machine is metal and the resistance is 0, the discharge time is very short, almost between ms or us. But the more important problem is that since the equivalent resistance is 0, the current is very large, so even a 200V MM discharge is more harmful than a 2kV HBM discharge. And since the machine itself has many wires that will couple with each other, the current will interfere with changes over time.

3. Charged-Device Model (CDM)
This discharge mode means that static electricity is accumulated inside the IC due to friction or other factors, but the IC is not damaged during the accumulation of static electricity. During the handling process of this IC with static electricity, when its pin touches the ground, the static electricity inside the IC will flow out from the inside of the IC through the pin, causing the discharge phenomenon. Charged-Device Mode static electricity discharge may occur. After the IC slides out of the IC tube, the charged IC pin contacts the ground and causes the discharge phenomenon.

4. Field-Induced Model (FIM)
The electrostatic discharge of this FIM model is caused by electric field induction. When the IC passes through an electric field due to a conveyor belt or other factors, its relative polarity charges may be discharged from some IC pins. After the IC passes through the electric field, the IC itself accumulates static charge, which will be discharged in a mode similar to CDM.