Numerical analysis of microwave-assisted encapsulation processes for ball grid array packages

Microwave cure of thermosetting polymer encapsulant material is assessed using a multiphysics analysis approach. A dual section microwave oven system capable of heating individual components on a printed circuit board assembly is described and its integration into a microelectronics manufacturing line is briefly outlined. Due to the complexity of measuring key process parameters in situ, a numerical approach, described in this article, has been adopted to analyse and optimise the curing process. The numerical model comprises an unstructured finite volume thermophysical solver linked through an Eulerian-Lagrangian mapping process, to a conformal finite difference time domain electromagnetic solver. A sample analysis is presented that focuses on the curing of an encapsulant material in a simplified ball grid array package. Solutions are presented on the behavior of the package submitted to a range of temperatures and microwave power density, The resulting thermomechanical stress are modelled.