Re-entrant cavity surface enhancements for immersion cooling of silicon multichip packages

The authors describe the performance of silicon re-entrant cavity structures for enhanced heat removal from substrates used in silicon multichip systems. The heat sink surface consisted of a large array of pyramidal cavities etched into the silicon using standard microelectronic fabrication techniques. Two different re-entrant cavity shapes, simple and complex, were studied. A thin-film resistive heater fabricated on a silicon substrate served as the heat source. Experiments were conducted in a pool of the dielectric liquid, refrigerant-113, which has near zero contact angles with most materials used in electronics fabrication. Tests were run for both saturated and subcooled conditions. The saturated pool boiling heat transfer characteristics of the cavity enhanced surfaces were superior to those of a plain surface, resulting in a substantial decrease in both the temperature overshoot and the incipient boiling heat flux. For the enhanced surfaces, subcooling generally resulted in an increase in incipient boiling heat flux when compared with the saturated conditions. Overall, this heat sink surface shows potential for use in the next generation of silicon multichip packaging for integrated microelectronics