Effects of fin geometry on boiling heat transfer from silicon chips with micro-pin-fins immersed in FC-72

Experiments were performed to study the effects of the height and thickness of square micro-pin-fin on boiling heat transfer from silicon chips immersed in a pool of degassed or gas-dissolved FC-72. Six kinds of micro-pin-fins with the dimensions of 30 × 60, 30 × 120, 30 × 200, 50 × 60, 50 × 200 and 50 × 270 (mu)m^2 (thickness, t × height, h) were fabricated on the surface of a square silicon chip with the dimensions of 10 × 10 × 0.5 mm^3 by using the dry etching technique. The fin pitch was twice the fin thickness. The experiments were conducted at the liquid subcooling, (delta)T(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 heat transfer 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 (delta)T(sub). The maximum value of allowable heat flux (=84.5 W/cm^2), 4.2 times as large as that for the smooth chip, was obtained by the chip with h=270 (mu)m and t=50 (mu)m at (delta)Tsub=45 K.