The heat dissipation effects of elevated pressure and cold gas temperature on vertically configured module mounted and free hanging chips were examined. It was found that with both types of chips, the thermal resistance (temperature rise x area/power) varies linearly with pressure in a log-log plot. A free hanging chip exhibits a (-1/3) power dependency on pressure while the module mounted chip exhibits a (-1/5) power dependency on pressure. The thermal resistance of the module mounted chip also appears to exhibit a dependency on gas temperature, but not on the difference in temperature between the chip and cold gas. The thermal resistance of the module mounted chip is some 5x lower than that of the free hanging chip, demonstrating that the module acts to a degree as a thermal expander. The efficiency is less than 20% based on the fact that the module area is some 30x greater than the chip area. For the module mounted chip, and a combination of a liquid nitrogen gas temperature and 1500 psi ambient atmosphere pressure, > 30 W/chip (0.180 in. × 0.180 in.) (0.46 cm × 0.46 cm), can be dissipated with a temperature rise to 85°C. This translates to a heat dissipation capability of more than 900 W/in2. © 1982 AIME.