1、 The generation of mechanical stress
When the flatness of the bonding surface between the bottom of the IGBT package and the heat sink is poor, perfect contact may not be formed between the package and the heat sink. During IGBT operation, thermal expansion occurs between the package and the heat sink due to chip heating. Due to poor flatness of the bonding surface, thermal expansion may cause uneven contact between the package and the heat sink, resulting in uneven mechanical stress.
2、 The Effect of Mechanical Stress on IGBT
Chip damage: Uneven mechanical stress may cause changes in the microstructure inside IGBT chips, such as lattice distortion, cracks, etc. These changes may reduce the performance of the chip and even lead to chip damage.
Packaging failure: Mechanical stress may also cause deformation, delamination, or fracture of the packaging material. These packaging failure issues will further affect the heat dissipation performance and electrical connection reliability of IGBT.
Reduced reliability: Long term exposure to uneven mechanical stress can accelerate the aging process of IGBT, reducing its service life and reliability.
3、 Solution
Improve the flatness of the bonding surface: By improving the processing technology and quality control measures, the flatness of the bonding surface between the bottom of the IGBT package and the heat sink can be improved. This can reduce the gap between the package and the heat sink, lower the contact thermal resistance, and minimize the generation of mechanical stress.
Optimize packaging structure: Adopt more advanced packaging technologies and materials, such as double-sided heat dissipation structure, pressure bonding packaging, etc., to improve the reliability and stability of packaging. These technologies can better disperse and alleviate mechanical stress, reducing the impact on IGBT chips.
Strengthen heat dissipation design: Optimize the design and selection of heat sinks to improve heat dissipation efficiency. By increasing the heat dissipation area and using more efficient heat dissipation materials, the operating temperature of IGBT chips can be reduced, thereby reducing the generation of thermal expansion and mechanical stress.
In summary, the poor flatness of the bonding surface between the bottom of the IGBT package and the heat sink can indeed cause uneven mechanical stress on the IGBT chip. This mechanical stress may have adverse effects on the performance and reliability of IGBT. Therefore, in the packaging and heat dissipation design of IGBT, it is necessary to comprehensively consider these factors and adopt corresponding solutions to ensure the stable operation and long life of IGBT.
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.
