Question

blem 4 (20 pts) A square chip that is 12.7mm on a side has a maximum allowable chip operating temperature -75°C. To dissipate heat produced in the chip, a 4 x 4 array of copper (k-400 W/m.K) pin fins is proposed to be etallurgically joined to the outer surface of the chip. The convection coefficient is h-250 W/m'K and ambient air mperature isTo-20°C. The pin fin dimeter is D,-1.5mm and length is L,-16mm. Assuming steady-state uniform chip temperature Te-75°C and negligible any contact resistance. (a) (6 points) What is the efficiency of a Sideview Top view Pin fins, D single fin? Chip, le 0 0 0 Chip 石 Board, k W- 12.7 mm (b) (14 points) What is the overall efficiency? what is the total heat transfer rate that can be removed by convection what is the effectiveness ofthe fins? (You can assume ηf-0.8 ifyou cannot find it in part (a)). If the chip is place on a board of thickness Lb 5mm and thermal conductivity k-1 W/m.K, and the other surface of the board maintained at a constant temperature To-65°C, how much additional heat can be removed through conduction in t board?

Answer 1

→(a). Heat -hans ler through Dne fin Can v= 0.923 W 0-9 23 -0.89 = 2.09*) VM C Scanned with CamScanner

2 = 1.028 w at base e bod 16. S9 : 0.901s 90.15% (0.0127%s) = 7-984 Ans 7 S-65 Conc 0.322, W Ans C Scned with CamScanner