Stress concentration: When the flatness of IGBT chips is poor, there may be unevenness on the surface of the chip. These uneven areas are prone to stress concentration when subjected to external forces or temperature changes. Especially at the connection between the bonding wire and the chip, due to the differences in material and size between the bonding wire and the chip, it is more susceptible to stress concentration.

Uneven stress on bonding wires: Poor flatness of the chip can also lead to uneven distribution of bonding wires on the surface of the chip. When subjected to external forces or temperature changes, the bonding wire may deform or break due to uneven force distribution. Especially at the connection point between the bonding wire and the chip, due to the influence of stress concentration, the bonding wire is more prone to detachment or breakage.

2、 The consequences of bond failure

Electrical connection interruption: Bond failure can cause electrical connection interruption, making IGBT modules unable to function properly. This may lead to malfunction or failure of the entire circuit system.

Performance degradation: Even if the bonding wire is not completely broken, poor or loose connections can still lead to a decrease in the performance of IGBT modules. For example, it may increase the on resistance, decrease the switching speed, etc.

Reduced reliability: Working in a stress concentrated environment for a long time will accelerate the aging and failure process of the bonding wire. This will reduce the reliability of IGBT modules and increase the risk of their failure.

3、 Response measures

Improving chip flatness: By improving chip manufacturing processes and quality control measures, the surface flatness of IGBT chips can be enhanced. This can reduce the occurrence of stress concentration and lower the risk of bond failure.

Optimize bond wire design: Adopt more reasonable bond wire design and material selection to improve its stress and fatigue resistance performance. For example, bonding wire materials with higher elastic modulus and better heat resistance can be chosen.

Strengthen packaging process control: Strictly control packaging process parameters and quality requirements during the packaging process. Ensure that the connection between the bonding wire and the chip is firm and reliable, reducing bonding failure issues caused by improper packaging processes.

In summary, poor flatness of IGBT chips is one of the important reasons for stress concentration and bonding failure at the connection between bonding wires and chips. In order to improve the reliability and performance stability of IGBT modules, it is necessary to strictly control chip flatness, optimize bonding wire design, and strengthen packaging process control.

IGBT package bonding flatness test case: (Color temperature chart represents 3D high and low information, table shows measured deformation)

4、 Introduction to Laser Frequency Comb 3D Optical Contour Measurement System

The laser optical frequency comb 3D contour measurement system utilizes the principle of laser frequency comb and adopts high-frequency laser pulse flight distance measurement method, which is not afraid of traditional optical obstruction problems and fully applicable to the measurement of various complex large structural components, solving the difficulties of traditional optical measurement such as deep holes and grooves. The laser frequency of 500kHz has brought technological innovation to the automation of detection.

Technical feature one: coaxial shooting, flight ranging scanning method, not afraid of traditional optical "obstruction" problems.

Actual case: Valve body oil circuit board with vertical and horizontal grooves

Technical feature 2: With an accuracy of ± 2um, it can achieve a maximum height/depth scanning imaging of 130mm

Technical feature three: It can be equipped with multiple lens combinations to achieve scanning with a large field of view of tens of meters.