The Research On Failure Mechanism Of High-Power Plastic Packaging Devices

Plastic packaging devices were developed in 60's last century. Compared with ceramic and metal package, plastic packaging has the features of small size, low cost, light weight, portability and many other advantages. So, the application and research on plastic devices are widely carried out at home and abroad. However, some hidden troubles present in the plastic packaging devices, for example, its non-gastight material susceptible to moisture intrusion. Under the alternative temperature circumstances, since the materials have different thermal expansion coefficient, and internal stress mismatch arises, the internal chips break.The failure mechanism of plastic packaging devices is in-depth investigated in this thesis. There are frequently the "popcorn" effect, corrosion phenomena, layering hollow phenomena during high and low temperature cycle in the plastic devices. Therefore, 13005A plastic packaging power devices are chosen as the research objects, and a large number of alternating temperature tests, electrical aging tests, as heat and humid tests, salt spray tests are carried out. According to experimental results, most serious failure of the devices happens in the pressure cooker experiments. Seven different levels of chip failure arise in 22 groups of experiments. Based on the experimental results and combined with relevant literature, several measures for the plastic packaging devices reliability are improved. The high-power transistors, plastic 13005A, are simulated and analyzed with ANSYS finite element analysis software. The model construction, meshing and loading boundary conditions are in detail described. The stress distribution and temperature distribution are attained with the simulation under the work state and the high and low temperature cycle condition. The results show that there is large Mises stress located in the corner of contact face between the chip and the adhesive layer and the copper substrate, the high temperature region near the chip is close to the surface temperature of silicon chip. Finally, the experimental results are compared with the simulation results, the most important cause for the device failure is brought out, and some effective measures avoiding the device failure are proposed. The research results are the good reference for improving the plastic packaging process technology of high-power devices to enhance the plastic packaging devices reliability.