Why do IGBT modules age and fail? How to deal with it?
Insulated gate bipolar transistor (IGBT) modules are widely used in high-voltage and high-power inverter systems such as wind power generation, flexible AC transmission, motor traction, and aviation. As one of the most prone components to failure in power electronic systems, IGBT failures can be divided into sudden failures and aging failures. If IGBT aging failures cannot be detected in advance, it will lead to system failures, causing the entire system to be paralyzed and resulting in unpredictable losses.
IGBT consists of a chip layer, a solder layer, a DBC (direct bonding copper) layer, and a copper substrate. The main failure locations of IGBT modules include the root of the bonding wire, the metallization layer of the chip, and the solder layer between materials. The packaging structure of IGBT module is shown in Figure 1.
The failure of IGBT is mainly related to the following factors:
1) Overheating. When the junction temperature of IGBT exceeds its maximum allowable temperature, it can cause device performance degradation and even burnout. Overheating is usually caused by excessive current, poor heat dissipation, or issues with the drive circuit.
2) Overcurrent. When the current flowing through an IGBT exceeds its rated current, a large amount of heat is generated, causing the device temperature to rise and potentially leading to failure. Overcurrent is usually caused by load short circuits, drive circuit faults, or improper circuit design.
3) Overvoltage. When the voltage borne by IGBT exceeds its rated voltage, it can cause device breakdown and damage. Overvoltage may be caused by transient overvoltage during switch operation, lightning strikes, etc.
4) Transient overcurrent. During operation, IGBT may experience transient overcurrent, such as reverse recovery current of freewheeling diodes, discharge current of buffer capacitors, etc. Although these transient overcurrent events have a short duration, if no measures are taken, they will increase the burden on IGBT and lead to device failure.
5) Drive circuit. The mismatch between the operating frequency of the driving circuit, the rising/falling edge rate of the output voltage, and the IGBT switching rate, or the insufficient average output power and peak power of the auxiliary power supply, may all cause IGBT to malfunction and fail.
6) Manufacturing process, materials, and usage environment. If there are process control issues or the use of substandard materials during the manufacturing process, it may lead to early failure of IGBT. Environmental factors such as temperature, humidity, and mechanical stress may also affect the performance and service life of IGBT, leading to failure.
1. Physical Failure Analysis
Physical failure refers to the deformation of materials caused by internal thermal stress during normal operation of IGBT, ultimately leading to its inability to function properly. Physical failures mainly include bond wire aging, metalization layer reconstruction, and welding layer degradation [11].
1) Aging of bonding wire
The aging of bonding wires mainly includes two situations: bonding wire detachment and bonding wire fracture, as shown in Figure 2. During normal operation, IGBT is affected by thermal stress generated by temperature changes, which can cause delamination of bonding wires and lead to faults, resulting in aging and failure of IGBT modules.
2) Metalization layer reconstruction
As the number of IGBT power cycles increases, the aluminum metal layer on the chip surface deteriorates, the grain size increases, and the aluminum layer is squeezed. The reconstruction of the metallization layer will cause an increase in layer resistance, leading to an increase in saturation voltage drop parameters and causing local hotspots or melting. The reconstruction of IGBT metallization layer is shown in Figure 3.
3) Degradation of welding layer
The connections between DBC and chip, DBC and substrate inside IGBT modules are mostly completed through welding, and long-term thermal cycling stress can cause embrittlement and cracking of the welding layer. The breakdown of IGBT solder layer is shown in Figure 4.
2 Electrical Failure Analysis
The electrical failure of IGBT refers to the failure of IGBT caused by the internal voltage and current of the component during its operation. The forms of electrical failure include electrical overstress failure, electrostatic discharge failure, and latch up effect failure [12].
1) Electrical overstress failure
IGBT electrical overstress failure refers to the failure caused by electrical stresses such as overvoltage and overcurrent exceeding the IGBT's bearing capacity. IGBT will generate collector emitter overvoltage spikes during the turn off process, causing the device to short circuit and fail to operate normally.
2) Failure of electrostatic discharge
Under normal operating conditions, the device accumulates charges, which may cause breakdown of the device material layer during charge discharge. At this time, when the gate or input terminal of the IGBT is impacted by static charges, it may cause damage to its internal circuits or components, leading to failure.
3) Latch effect failure
When the collector current increases to a certain extent, the parasitic thyristor is affected by the forward bias voltage and conducts, causing the gate to lose control and form a self-locking phenomenon. This leads to an increase in collector current, causing significant power loss and accelerating the occurrence of failure.
3 IGBT Failure Delay Methods
The methods for delaying IGBT failure can be approached from multiple aspects, including:
1) Thermal management. Overheating is one of the main factors causing IGBT failure, so heat management is crucial. More effective heat dissipation solutions can be adopted, such as optimizing heat sink design, increasing heat dissipation area, improving heat dissipation efficiency, etc., to reduce the operating temperature of IGBT and avoid overheating damage.
2) Current control. Reasonably control the current magnitude and rate of change of IGBT to avoid exceeding the rated current and current rate of change range of IGBT. Appropriate driving circuits and parameters can be used to ensure that IGBT operates within a safe range.
3) Voltage control. To avoid IGBT being subjected to overvoltage or surge voltage beyond its rated voltage, appropriate absorption circuits can be connected in parallel at both ends of the IGBT or appropriate protective measures can be taken to absorb overvoltage or surge voltage.
4) Reliability design. In terms of reliability design of IGBT, technologies such as redundancy design, fault diagnosis, and isolation can be adopted to improve the reliability and stability of IGBT.
5) Manufacturing process control. Strengthen quality control and process control in the manufacturing process to ensure the quality and performance of IGBT. Appropriate screening and testing methods can be used to eliminate IGBT devices that fail early.
6) Use environmental control. Ensure that IGBT is not affected by excessive temperature, humidity, pressure and other environmental factors in the usage environment, and avoid adverse effects of environmental factors on the performance and service life of IGBT.
Tag:
Related News
What are IGBT modules (IPM modules)
Copyright © 2025 Kyent Industrial Co., Ltd | Powered by: www.300.cn | Privacy Policy