Core Crack Mitigation in Semiconductor Substrates: A Multi-Scale Simulation Approach to Design Organic Core Material Properties

In advanced semiconductor package, organic core materials are widely used. It is essential for ensuring mechanical reliability, yet cracks can occur within the organic core under thermal loading. However, guidelines for designing core materials that suppress these cracks without increasing warpage of the semiconductor package have not yet been established. Here, we present a two-step multi-scale simulation approach to optimize the organic core material properties used in advanced semiconductor packages, focusing on mitigating core crack initiation without increasing package warpage. In the first step, the effective anisotropic properties of a composite core material —consisting of resin and glass cloth—are computed through homogenization methods to establish a macro-scale model of the flip chip ball grid array structure. In the second step, localized finite element simulations utilizing representative volume elements are performed to investigate the stress distribution in the microstructure, particularly at free edge regions prone to cracking. The simulation results demonstrate that controlling the resin’s through-thickness (out-of-plane) coefficient of thermal expansion (CTE) can reduce local tensile stresses responsible for crack initiation without notable increases in board warpage. In addition, thermal‑shock experiments confirmed the same trends obtained from the simulations and provided practical validation of our design guidelines. In summary, this integrated approach offers a practical route to engineer core materials that both prevent cracking and limit warpage in semiconductor packages.