Thermo-mechanical design of a generic 0-level MEMS package using chip capping and Through Silicon Via's

Abstract

This paper describes the thermo-mechanical design of an advanced zero-level capping technology used for packaging of a MEMS die. The package approach uses Intermetallic Compound (IMC) bonding to seal the MEMS die with a cap, and uses Through Silicon Via's (TSV) to provide the electrical connections from the MEMS die to the second level substrate (LTCC or PCB). Advanced FEM based thermo-mechanical simulations are performed to estimate the impact of processing and temperature cycling on the mechanical stresses and deformations induced in the structure. Special focus goes to the rigid CuSn IMC bond, the copper TSV using a polymer dielectric and the cap deflection under a pressure of 1 bar (vacuum inside) and 90 bar (simulating overmoulding). Finally, the impact of assembling the MEMS package on an LTCC substrate and an FR4 printed circuit board with CuSn, respectively solder connections is investigated with respect to the package reliability, the cap deflection and the strain and anchor rotation at location of the MEMS.