Numerical thermal analysis for leaded surface mounted plastic package

The numerical detailed model and compact model were created for plastic quad flat package (PQFP), and the accuracy of two models was verified by the measurement values. The steady thermal performance of PQFP was studied under harsh environment, and factors effecting on the inner and outer thermal resistances were analyzed. Results show that using the multi-layer structure is a perfect way to improve the thermal performance, and forced air velocity around the PQFP should be lower than 5 m/s. The transient thermal performance of PQFP was discussed for two cases: pulse heat loads and the ambient air temperature varying with time. Thermal responses of the die were got, which could be used to study the thermal stress, disability, and signal fuzzy, and be a basis for improving package's thermal design.