Warpage analysis of the fingerprint module with a thin-core substrate

Abstract

Warpage measurement and control are critical for package design and optimization. In this paper, the warpage of a fingerprint module fabricated with the thin-core substrate (0.21+/−0.04 mm in thickness) was investigated. Shadow moire test was conducted to follow the warpage changes of the modules and bare thin-core substrates in a simulated reflow process. The average initial warpage of five modules was 40.8µm. With the temperature ramping up to about 250°C, the warpage of the module and the substrate reduced to the minimum. After the reflow, the warpage of the module increased a lot. This phenomenon is likely due to the plastic deformation of package materials in the process. As a comparison, the bare thin-core substrate did undergo some warpage changes while the temperature going up and down. Its final warpage was almost consistent with the warpage before the simulated process. Furthermore, we adopted the dual curvature model to calculate the warpage of the module. The calculated warpage was 47.5µm, with a deviation of 16% from the shadow moire result. The finite element simulation obtained a warpage of 46.7µm, which verified the numerical calculation result.