A Development of Finite Element Analysis Model of 3DIC TSV Package Warpage Considering Cure Dependent Viscoelasticity with Heat Generation

Abstract

In this study, a numerical methodology to predict package warpage considering viscoelasticity with cure-kinetics during thermal process was proposed. When a package undergoes thermal condition, residual stress between layers occurs. The residual stress is caused by different coefficient of thermal expansion (CTE) and chemical reaction of materials. And it causes package warpage. Because package warpage can affect driven performance, reliability and alignment issues, it is important to predict and control package warpage for designing process and improving a performance of package. For a prediction of package warpage, a finite element method (FEM) is commonly used. With FEM it is able to calculate the warpage caused by different CTE between layers. However, because properties of materials, which have curing characteristic, evolves with curing, if cure-kinetics are not considered, it is difficult to predict package warpage properly. So a numerical approach for considering cure-kinetics of materials was developed to predict package warpage during thermal process. Using user subroutine function in ABAQUS commercial FEM software, we build generalized Maxwell material model which can represent viscoelastic material response. And we calculated degree of curing with Kamal-Sourour cure kinetic equation for each time increment. Then we made parameters for the Maxwell material model as function of degree of curing. As a result, the developed analysis model explains heat generation during curing process and change of material properties depending on degree of curing. With our analysis model, it is expected that more accurate prediction of warpage can be conducted and it leads to improvement of package performance.