Chip scale packaging of piezoresistive pressure sensors using dry-film shielding

In this study, a chip scale packaging (CSP) of piezoresistive pressure sensors using a dry-film shielding approach is demonstrated. A sensing-channel just above the silicon membrane of the pressure sensor has to be reserved in the package body. To prevent the silicon membrane of the pressure sensors from the metal-deposition contaminations, a dry-film with a redistribution pattern is used to shield the sensing-channel opening during seed layer sputter process of the trace redistribution. Experimental results reveal that the silicon membrane of the pressure sensor is free of metal-deposition contamination and functional operation. The packaged pressure sensor has a linearity error of 0.2 psi at 25degC and sensitivity repeatability of 3.5times10^-4mVV^-1psi^-1 at pressure range of 0~100psi (3sigma). The proposed pressure sensor package holds advantages on both low cost and tiny packaging size, making it suitable for portable consumer products.