Analytical and finite element study on warpage and stress of 2.5D chip-package structures

New analytical methods are proposed to investigate the warpage of 2.5D system in package (SIP) fabricated through different temperature steps based on laminate theories. The solutions apply in both axisymmetric and rectangular configurations for packages with different multilayer sections. A multi-step finite element (FE) model is developed to verify the analytical results and to examine stress distributions in the chip-package structures with respect to the fabrication steps. The analytical and FE results are in good agreement to account for the warpage at the chip scale, whereas the FE model provides local stress analysis at the micro-bump and solder ball levels that can be further extended for failure analysis.