Effects of curing condition and solder mask on substrate warpage: an experimental and simulation study

The warpage of the package substrate mainly originates from the material property and size variations of individual components, especially when multiple components are involved. To maintain the substrate warpage within acceptable limits, it’s crucial to fine-tune component parameters carefully, choosing appropriate materials and processing conditions. The current study investigates the factors influencing substrate warpage and explores the methods to mitigate it with the assistance of finite element analysis. Glass fiber reinforced epoxy-based substrates were prepared under different curing temperatures, and characterized by thermo-mechanical analysis and mechanical testing. A finite element simulation model of the bare carrier board was developed using ABAQUS software. The results show that the curing temperature impacts the coefficient of thermal expansion (CTE), strength and modulus of the substrate. The differences in CTE and dimensional parameters among the component materials strongly influence substrate warpage. While the curing conditions affect bare carrier board warpage to some extent, the type and thickness of solder mask have more significant effects and warpage can be mitigated by properly choosing and applying solder masks.