Anisotropic conductive film for flip-chip interconnection of a high I/O silicon based finger print sensor

Abstract

Anisotropic conductive film (ACF) has been used for flip chip interconnection of a silicon based MEMS finger print sensor to a signal processing ASIC. The assembled sensor device was subjected to a short term high temperature profile with peak temperature 260 C simulating subse-quent reflow soldering of the device, and to thermal shock cycling from -40 to +85 C. The reliability of interconnects during ageing was investigated by monitoring changes in electrical resistance of single interconnects and interconnect daisy chains. The electrical resistance increased after exposure to the high temperature soldering profile, but no failures were observed even after 10 repetitions. Thermal shock cycling showed an increase in electrical re-sistance and no failures. A relatively large resistance increase was found for some interconnection points.