Investigation on the Numerical Modeling of Continuous Welding Stress Evolution Behavior in SiP

As an important packaging form of high density integration of electronic products, SiP ceramic envelope is widely used in the aerospace, navigation and communication and other fields. Due to the difference in thermal deformation between the ceramic substrate and the metal enclosure, obvious residual stress is generated in the welding area, and the superimposed stress in the subsequent process will aggravate the cracking failure risk of SiP ceramic envelope. However, the cumulative evolution behavior of stress in SiP ceramic envelope under continuous welding conditions has not been clarified. In this paper, a thermo-elastic-plastic numerical model of welding stress of SiP ceramic envelope is established to study the cumulative evolution behavior of welding stress of SiP ceramic envelope under brazing, surface mounting, seam welding and temperature cycle conditions. Based on the stress state regulation, low stress welding technology of SiP ceramic envelope is obtained. The results show that: (1) the stress caused by the thermal mismatch between the ceramic substrate and the metal enclosure is concentrated in the four corners of the sealing frame, and when the parallel seam welding of the cover plate increases the structural stiffness of the metal enclosure, the thermal mismatch between the metal enclosure and the ceramic substrate will be aggravated. With the decrease of temperature, the stress level continues to increase. Although the stress level decreases in the high temperature due to the plastic flow and thermal mismatch relief, the stress level increases significantly when the temperature is lowered. (2) Through the use of AuSn solder and MoCu composite frame design can significantly reduce the stress level of SiP ceramic envelope, improve packaging reliability, and the stress relief by the composite frame design is better.