While most recently electronic cooling studies have been focused on removing the heat from high-power-density devices, the present study also explores means of greatly decreasing the device operating temperature. This is achieved by incorporating a microchannel heat sink as an evaporator in an R134a refrigeration loop. This system is capable of maintaining device temperatures below while dissipating in excess of . It is shown that while higher heat transfer coefficients are possible with greater mass velocities, those conditions are typically associated with wet compression corresponding to evaporator exit quality below unity and liquid entrainment at the compressor inlet. Wet compression compromises compressor performance and reliability as well as refrigeration cycle efficiency and therefore must be minimized by maintaining only slightly superheated conditions at the compressor inlet, or using a wet-compression-tolerant compressor. A parametric study of the effects of channel geometry on heat sink performance points to channels with small width and high aspect ratio as yielding superior thermal performance corresponding to only a modest penalty in pressure drop.