Thermal studies on finned LSI packages using forced convection

The authors describe extensive computer-based analytical and experimental studies on finned LSI packages, utilizing a cavity-down-type QFP348pin (quad flat pack 348pin) package, in order to develop a simulation method for a high-thermal-performance package and its heat sink. The numerical analysis was accomplished for a conjugate problem, which encompassed flow and heat transfer in the cooling air stream and heat conduction in the package and the heat sink. Experiments were conducted to measure the temperature rise at the junction, the package surface, and the fin, using several kinds of omnidirectional heat sink fins in a wind tunnel. The applicability of the model used for the simulation and the computational scheme were verified by comparing the experimental results with those obtained on the basis of the model. These comparisons lead to the conclusion that the proposed numerical method of predicting the thermal resistance of finned LSI packages will be satisfactory for thermal designers