Common causes of MOS tube failure

By Weidmüller

MOS tubes are widely used in computer motherboards, NB, computer adapters, LCD displays, network communications, industrial control, automotive electronics and power equipment, and have great market demand.

Although MOS tubes are widely used, they sometimes fail, resulting in malfunction. In general, failures in the development, production, and use of MOS tubes are difficult to avoid. As people's requirements for product quality continue to increase, fault analysis work becomes more and more important, through specific fault chips. Analysis can help circuit designers find problems in device design, process parameter mismatch, unreasonable peripheral circuit design, or misoperation.

Here are some common reasons why MOS tubes fail:

1, large current, such as severe overcurrent short circuit damage, pure overcurrent damage will generate a lot of heat in the source line area, will burn a large piece around the pressure line.

2, overvoltage damage, including gate overvoltage, drain overvoltage, overcurrent is often accompanied by overcurrent, if it is protected in a short period of time is simply overvoltage damage, it can be seen that the source is not playing There will be small black spots in the line area, and the color may not be very deep. If there is no protection after overvoltage and then enters overcurrent damage, the chip will appear black in large areas in the source non-wired area.

3, overheating damage, if the MOS tube does not flow too much pressure, just because the junction temperature is too high damage, if it is protected, the surface will not see obvious burns, if not protected, it will generate a lot of heat in the wire area , burn a large piece of black around the crimping site.

4. Body diode failure: In the topology of bridges, LLCs, etc., where the body diode is used for freewheeling, the failure due to the destruction of the body diode.

5. Resonance failure: In the process of parallel use, the parasitic parameters of the gate and the circuit cause the oscillation of the MOS tube caused by the oscillation.

6, the mechanism of MOS tube damage is ultimately thermal damage, local crystal package overheating or overall heat, such as overpressure, but also the low pressure of the crystal packet first breakdown heat damage slowly expanded.

The failure of the MOS tube can be analyzed accurately according to the specific circuit and the burn phenomenon. In the application of MOS tube, perhaps everyone has a deep understanding, the definition of various parameters of MOS tube is more ideal, and there will be a big difference between the actual application, the two are still related, how to use Good MOS tube, need to know more about MOS tube and application.