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 ΔT_sub 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 q_CHF 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, q_CHF increased monotonically with increasing h. The increase was more significant for larger t. The q_CHF increased almost linearly with increasing ΔT_sub. The maximum value of allowable heat flux q_max(=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 ΔT_sub=45 K.