Boiling heat transfer from silicon chips with micro-pin-fins immersed in FC-72 (Combined effects of fin height and fin thickness)

Experiments were performed to study the combined effects of the height and thickness of micro-pin-fin on boiling heat transfer from silicon chips immersed in a pool of degassed or gas-dissolved FC-72. Six kinds of square micro-pin-fins with the dimensions of 30 × 60, 30 × 120, 30 × 200, 50 × 60, 50 × 200 and 50 × 270 μm2 (thickness t × height h) 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. The fin pitch was twice the fin thickness. The experiments were conducted at the liquid subcooling ΔTsub of 0, 3, 25 and 45 K under the atmospheric condition. The results were compared with previous results for a smooth chip and three chips with enhanced surfaces. The micro-pin-finned chips showed a considerable heat transfer enhancement in the nucleate boiling region and increase in the critical heat flux qCHF as compared to the smooth chip. The wall temperature at the CHF point was always less than the maximum allowable temperature for LSI chips (=85°C). For a fixed value of t, qCHF increased monotonically with increasing h. The increase was more significant for larger t. The qCHF increased almost linearly with increasing ΔTsub. The maximum value of allowable heat flux qmax(=84.5 W/ cm2), 4.2 times as large as that for the smooth chip, was obtained by the chip with h=270 μm and t =50 μm at ΔTsub=45 K.