Direct liquid cooling of a stacked MCM

In this paper, the experimental and numerical results for a direct single-phase liquid cooling scheme are presented and discussed for the stacked Multichip Module (MCM). The stacked MCM consists of one substrate, three carriers which are stacked on top of each other and three thermal test chips which are mounted on the carriers by the flip chip attachment method. FC-72 was used as the coolant. Studies were carried out for a single chip being powered in turn and for all three chips powered. The pressure drops between the inlet and outlet were obtained for different flow rates, and the temperature differences in the chips are determined and discussed. A three-dimensional numerical simulation was also conducted to investigate the flow and the conjugate convection-conduction heat transfer in the cooling structure. The maximum limit on the package power currently tested (4 W) is however quite limited because of the high flow bypass and relatively low flow rate. Further analysis indicates that by reducing the bypass, increasing the flow rate and using better coolants, a maximum power of 40 W is achievable for single phase liquid cooling.