Fluid Cooling of High Power Density Semiconductor Devices.

Dielectric coolant fluids operating in an evaporation-condensation cooling cycle were investigated to determine how much they could reduce the surface temperature of high power density semiconductor devices. A brief description of the process reveals that the air-side thermal resistance of the condenser and the critical heat flux density of the fluid at the semiconductor surface are problem areas. Ther thermal resistance and time constant of several TRAPATT diodes and microwave transistors were measured. The heat flux density at the surface of the TRAPATT diodes was too high to be compatible with conventional fluids. The junction temperature of microwave transistors was consistently reduced 10 C, and the process has a potential application in this area. (Author)