Thermal characteristics of single and multilayer high performance PQFP packages

The thermal performance of previously introduced single-layer and multilayer plastic quad flat pack (PQFP) packages based on the work of D. Mallik, et al. (1989) is discussed. Using experimental and computational techniques, it is shown that significant reduction in the package thermal resistance can be achieved by using a multilayer lead frame structure for PQFP packages with medium and high lead counts. The measurement and analysis techniques are discussed. It is shown that in addition to enhancing the electrical performance, use of a multilayer lead frame design can provide a significant improvement in the thermal performance of PQFP packages. Thermal resistance in 132-lead PQFP is reduced by 38 and 43% with copper and Alloy 43 lead frames, respectively, under natural convection. A three-dimensional finite-element thermal model was constructed and correlated with the experimental data. Using this model, it is demonstrated that the contribution of the low thermal conductivity insulating adhesive tape to the overall thermal resistance is about 1°C/W