Optimization of Thermal Design and Mold Flow Process for 3D SiP Structure

Abstract

Abstract With the advent of the 5G era, major package and testing plants have been taking frequent action recently. Obviously, with higher and higher performance requirements, SiP is a functional package integrated multiple functional chips, including processor, memory into one package. However, thermal design is an important issue to be addressed at this time. This paper mainly presents a 3D SiP structure based on the combination of two substrates, integrating 4 components in a single package, total power consumption is 30 Watt. To address thermal management difficulties of this 3D SiP, a method is designed to increase the thermal path between the two boards. The Effects of the structure, number of via, and changing location of components aspects of the thermal performance are studied. The thermal vias was designed in between the two boards provide are direct heat dissipation, connecting the metal studs above passive components to improve thermal performance. Thermal performance with 240 vias is improved by 0.4%, while the number of vias increases from 240 to 912, the temperature decreases only 1.0%, 0.6% respectively. The difference of thermal resistance (θJB) comparison is 1.9%, 1.5% and 1.0%. There are limits to the improvement of vias, the effect of increasing the number of via is not as good as expected. However, increasing the thermal conduction path may have an effect on the void of mold flow. s 3D mold flow modeling of the transfer molding process with molded underfill (MUF) using Moldex3D is applied to optimize design and process parameters that can reduce device defects. There is one important challenge that faced air voids entrapment in molding area. Generally, the experiments involve a lot of design of experiment (DOE) matrixes which spend a lot of time to solve air void issue. As above reasons, the mold flow simulation can be used to apply molding parameters to find out optimum solutions for air void risk free of SiP, which can reduce development cycle time before mass production. From the mold flow simulation results, when the number of plunger segments increases and the tail flow rate decreases, the void issues can be effectively improved.