Effect of the size of micro-pin-fin on boiling heat transfer from silicon chips immersed in FC-72

Experiments were conducted to study the effect of the size of micro-pin-fin on the boiling heat transfer from a silicon chip immersed in a pool of degassed or gas-dissolved FC-72. Four kinds of micro-pin-fins with the dimensions of 10×10×60 to 50×50×60 μm³ (width×thickness×height) were fabricated on the surface of a square silicon chip with the dimensions of 10 × 10 × 0.5 mm³ by use of the dry etching technique. Experiments were conducted at the liquid subcoolings ΔT_sub of 0, 3, 25 and 45 K under the atmospheric condition. The results were compared with those for a smooth chip and previously developed enhanced surfaces. The micro-pin-finned chips showed a considerable heat transfer enhancement as compared to a smooth chip in the nucleate boiling region. The boiling curve showed a steep increase in the heat flux with increasing wall superheat. For the micro-pin-finned chips, the critical heat flux was 1.9 to 2.3 times as large as that for the smooth chip and the wall temperature at the critical-heat-flux point was less than the upper limit for the reliable operation of LSI chips (=85°C). While the wall superheat at boiling incipience was strongly dependent on the dissolved gas content, it was little affected by the liquid subcooling.