Thermal and Mechanical Lid Design for a Multi-Chip Modular Flip-Chip Package

Abstract

The multi-chip modular packages are common in mobility applications, quite larger in size due to having different core components on the same substate. Its large size and mismatch in the coefficient of thermal expansion (CTE) between the die and substrate can lead to warpage of the package which in turn presents a huge reliability concern for modular packages. There are several warpage mitigation solutions available which tries to solve the warpage problem: namely, lidded package, stiffeners, core substrate etc. Due to lower space availability in modular packages, lidded package seems to be the preferrable solution for warpage mitigation in mobile applications.This study explores several lidded solutions with different lid materials and thickness for warpage mitigation and compare the mechanical performance with other warpage mitigation techniques. The lidded packages considered for warpage mitigation are also evaluated for thermal performance during the transient workloads in a passive clamshell form factor. This study compares the thermal performance of lidded package and bare die flip chip modular package and addresses the role of interface resistance and lid material and thickness. With lidded design, the warpage can be controlled at room and elevated temperature, however, the thermal performance of the lidded package can be superior or inferior depending on the interface resistance and lid design compared to a bare die package.