Prediction of Packaging Induced-Warpage for a 3D Stacked Package with a Cure-dependent Viscoelastic Model for EMC

Electronic devices today are continuously evolving towards higher density and enhanced functionality, placing greater demands on electronic packaging technology. As a commonly used encapsulation material, EMC has a significant impact on package warpage. Due to its nature as a thermosetting resin, considering the viscoelastic behavior of EMC during simulation using ANSYS can provide more accurate results compared to using elastic materials. In this article, the research object is the three-dimensional stacked packaging structure. In its curing process, the generalized Maxwell model is used as the constitutive model to describe the thermo-mechanical properties of the encapsulating material, and the Prony series is used to represent its transient part. Due to the change in the storage modulus and Tg point of the EMC after high- temperature storage, which affects the warpage of the package, DMA equipment is used to measure the viscoelastic parameters of the epoxy molding compound before and after high- temperature storage and process the data. Simulation software is used to investigate the effect of changes in EMC viscoelastic parameters under high-temperature storage on package reliability, and the impact of stress relaxation of the epoxy molding compound on warpage is studied using ANSYS Mechanical finite element software. The boundary conditions material parameters and temperature curves, and a single-factor method are used to consider the effect of EMC thickness, curing time, and temperature on the stress distribution of the chip and the warpage of the package. The response surface method is used to process the warpage values and obtain the optimal parameter combination. The results show that the change in EMC material properties after high-temperature storage has a significant impact on the stress of the package, and appropriate process temperature curves and structural parameter combinations can reduce the warpage of the chip.