Thermal evaluation of partially molded 2.5D package with pin fin heat sink cooling

A 2.5D package is referred to as the packaging of multiple chips on an interposer made of silicon or glass featured with through-vias filled with copper as electrical interconnects. Thermal management remains a challenge due to the integration of dissimilar chips such as logic and memory chips on a common interposer in molded package format. In this paper, a partially molded 2.5D package (PM package) with exposed die is assembled and evaluated thermally. The 2.5D package consists of a high power die (thermal test die in this case) and a dummy die assembled on a silicon interposer, which is then assembled on an organic substrate. A mold compound is applied on the top of the 2.5D package and then mechanically grinded to expose the heat generating die. This is to bridge the thermal path from the die to the top heat sink directly without molding material in between. Both experiments and simulation are constructed to examine the thermal performance under pin fin heat sink cooling conditions. Vertical and horizontal orientations of the PCB are also investigated. It is found that the partially molded package have a better thermal performance than the molded package under the vertical configurations at medium power inputs. The affecting factors fin width and fin number are examined. The thermal enhancement over the full mold package is also verified.