Simulation of Hygro Swelling Induced Stresses in Flip Chip Interconnects in a Stress-Sensitive Chip-on-Board Configuration

M. Fretz
Optics & Packaging, CSEM SA, Central Switzerland Center, Alpnach, Switzerland

Flip chip interconnections are used for the direct electrical connection of face-down electronic components like MEMS pressure sensors. The investigated bonding technologies are gold stud bumping in combination with anisotropic conductive adhesives (ACA) and solder ball bumping in combination with underfill in a chip-on-board configuration.

The modeled chip is an absolute pressure sensor based on silicon diaphragm technology. We present simulations with a special focus on sensor membrane stress effects due to hygro swelling of the ACA and the underfill.

The results are compared with simulations on thermally induced stresses in the membrane due to CTE mismatch of board, sensor, and ACA or underfill.