Methodology for Predicting BGA Warpage by Incorporating Metal Layer Design

Abstract

This paper presents a methodology to predict warpage of ball grid array packages (BGAs) that takes into account details of metal designs in the multi layered substrate. Composite theory along with local homogenization methods are used to resolve the distribution of material properties in each layer of the substrate that enables an efficient simulation model with moderate computational size. Associated procedures have been implemented and tested for finite element simulation tool. Verification examples were prepared to demonstrate the warpage predictions on BGA packages. Key substrate parameters including package mold compound shrinkage during post mold cure and the resultant impact on deformation behavior and mechanical reliability of BGA assemblies. A comparison of simplified homogenization methods and representative unit cell models of multi layered composite structures are discussed and show the significance of incorporating detailed metal layer design in simulation model for accurate warpage prediction.