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The fan-out wafer level package (FOWLP) integrates diverse materials, notably moisture-absorbent polymers like dielectrics and molding materials. Elevated temperatures induce moisture transformation to water vapor, causing significant stress and delamination between the chip and redistribution layers (RDLs) in case of mismatched coefficient of thermal expansion (CTE). This delamination, common at signal transmission interconnects, can impede smooth signal flow and lead to fractures. To tackle these challenges, this study devises a process-reliability coupling simulation method for analyzing stress and warpage in heterogeneous integrated packaging structures under hygro-thermal coupling. Simulations on polymer-bonded materials reveal strain differences at bonding interfaces due to mismatched CTE, impacting FOWLP reliability. The study further explores the relationship between thermal and wet expansion, deriving equivalent CTE for simulation analysis. By confirming FOWLP architecture and implementing nonlinear finite element analysis for structures with multi-layer RDLs, the study ensures simulation accuracy, validated with warpage measurements. Additionally, the study addresses the influence of viscoelastic properties and curing shrinkage, particularly in using epoxy molding compound (EMC), and constructs an equivalent wet-heat environment to replicate moisture diffusion effects. Analysis of Variance (ANOVA) based on three-dimensional finite element simulations examines stress distribution and warpage between different dielectric materials or interfaces. Proposals for optimized structural design aim to ensure FOWLP compliance with JEDEC standards and reliable operation.
Huang et al. (2024) studied this question.