Study on thermo-mechanical reliability of 3D stacked chip SiP based on cavity substrate

In this paper, a novel 3D stacked chip SiP structure based on cavity substrate is proposed. For the structure of cavity substrate is asymmetric, the thermo-mechanical reliability issues of the 3D SiP structure are very important and necessary to be studied. When molding compound is injected into the 3D SiP structure, it contacts with other parts of the structure. Because Young´s modulus of the molding compound varies with temperature during cooling process from molding temperature to room temperature and CTEs of different materials are mismatched, the effect of molding compound cooling process on the reliability of 3D SiP is necessary to be investigated. The thermo-mechanical reliability FEM simulation of the molding compound cooling process from molding temperature 125 °C to room temperature 25 °C is performed to study the warpage issue of the 3D package SiP. In order to conduct the molding compound cooling simulation correctly, Young´s modulus of molding compound dependent on time and temperature is tested by using DMA. The simulation result shows that the deformation won´t bring the warpage for the 3D SiP. Besides, the thermo-mechanical reliability FEM simulation of the 3D package module under thermal cycling (-40/125 °C) is evaluated to find out the stress and strain distribution of the 3D package module, the BGA and to predict the warpage, delamination, die cracking, solder joint cracking, excessive substrate deformation and cracking of the 3D package module. The simulation results indicate that the 3D package module has higher thermo-mechanical reliability.