Liquid cooling performance for a 3-D multichip module and miniature heat sink

Measured thermal performance is presented for a single phase liquid-cooled module. Tape automated bonded (TAB) thermal test chips and their associated substrates are stacked in a compact, 3-D liquid-tight module. A dielectric liquid, polyalphaolefin (PAO), is forced to flow past the active and inactive sides of TAB chips. At a volumetric flowrate of 0.05 gallons per minute (gpm) and an estimated pressure loss less than 0.5 psi, the measured junction-to-liquid thermal resistance is 2.0 C/W for a 0.50 in.×0.50 in.×0.015 in. thermal test chip. The thermal resistance was also measured for an indirect liquid-cooling approach. PAO was used to cool a miniature sink mounted directly to a 0.50 in.×0.50 in. heat source. The heat source was used to simulate the thermal characteristics of a chip carrier package. The overall dimension of the liquid heat sink is 1.0 in.×1.0 in.×0.28 in. The measured junction-to-liquid thermal resistance is 0.52 C/W for a flowrate of 0.05 gpm, and for an estimated pressure loss less than 1.0 psi. Numerical computational techniques yielded results which were comparable to the measured thermal resistances for both the 3-D module and the miniature heat sink. Enhanced thermal performance gained by introducing micro-encapsulated phase change material (microPCM) to the PAO is estimated for both the 3-D module and the miniature heat sink