Warpage prediction of chip package using simplified model of PCB substrate

Abstract

Warpage of chip package causes poor product yield in the process of mass production of electronic products. However, the prediction of warpage is difficult due to the complex and diverse substrate structures and the long processes. In this study, thermo-mechanical properties of epoxy materials and electroplated copper were measured accurately, and simplified printed circuit board model was suggested that could respond to various printed circuit board structures to enhance the warpage predictability of chip packages. Especially, dielectric glass fiber reinforced polymers in printed circuit board (PCB) became thinner recently, which results in difference between flexural and tensile properties. Due to the various structures of the PCBs, the distances from the neutral plane of the composite are varied within the product and one property cannot represent warpage behavior of composites. To counter this, the composite was modelled as a tri-layer structure to represent heterogeneity along thickness direction. The effective modulus of each layer of tri-layer structure was calculated from accurately measured properties, and this modeling allowed us to predict the warpage behavior of the composite layers in various locations. From this study, we will provide direction to address the various structures in predicting the warpage of PCB and chip packages.