The structural optimization of heterogeneous integration system in display based on thermal-mechanical behaviors

The display module plays an important role in the future terminal device. The trend of "more than display" means that the multi-function units and chips (e.g., display units, storage units, sensing units, communication units, even computing units) will be integrated into the display module. The heterogeneous integration system in display (HISID) is regarded as a promising candidate and potential architecture for higher density and higher performance products, and it is proposed with the advantages of intelligence, light-weight, high bandwidth, ultra-low latency, mobility. Nevertheless, the mismatches of coefficients of thermal expansion (CTE) and elastic modulus among functional components, solders, and substrate will result in the thermal reliability issues during the entire life cycle of devices. In this work, the hybrid analytical and FEM thermal shock simulation is applied to evaluate the thermal reliability of laminated HISID structures. Firstly, an effective analytical method is developed to investigate the thermal behavior of HISID models, where the inner stress along the thickness or the interfacial stress are calculated, and the warpage deformation is described with bending curvature. Then, the three-dimensional finite element HISID model is established to further investigate the thermal reliability design, where the inner stress and interfacial stress due to temperature change are obtained, and the warpage deformation from original plane are considered. Moreover, the optimal laminated HISID model is then obtained by adjusting the layer thickness and material properties. The glass-based substrate is investigated and considered as a crucial component to demonstrate the better thermal-mechanical behavior compared with traditional FR4-based substrate. The detail reduction of out-of-plane deformation (warpage) for glass-substrate is 42.18%, and the max mises stress reduction of solder bump is 32.30%. The stress distribution of solder is influenced by the thickness of silica gel layer and copper layer, the size and space of BGA-solders, and etc. The von Mises stress decreases with increasing of PCB-substrate thickness and decreasing of silica gel thickness; and the effect of BGA-solder radius on stress distribution is more obvious. Thus, the material and geometry modification of laminated HISID model is an effective way for the structural optimization based on the analytical method and finite element method.