Effect of nonuniform temperature on thermal modeling and strain distribution in electronic packaging

This paper analyses the effects of nonuniform temperature on thermal modeling and stress/strain analysis of an electronic package. A 208 lead plastic quad flat pack (PQFP) manufactured by Texas Instruments is used to show surface temperatures and mechanical deformation resulting from power dissipation in the package. The package is tested experimentally and thermally modeled using finite element analysis. The results are used to show how thermal resistive and conduction finite element models would be effected by surface temperature variation. The package is also used to study the mechanical deformation caused by localized joule heating. The moire interferometry technique is used to acquire displacement contours of an active PQFP and the results are compared to a uniformly heated sample. The results revealed that isothermal surface assumptions might cause errors at high power dissipation levels and that the thermal loading due to internal power dissipation produces significantly different strains than a uniformly heated sample