A novel plastic package for pressure sensors fabricated using the lithographic dam-ring approach

This study presents a novel plastic package for piezoresistive pressure sensors. A photoresist dam-ring patterned using the lithographic process is spin-coated on a piezoresistive pressure sensor to define a sensing channel in the pressure sensor package. Fluid epoxy molding encapsulates the pressure sensor and exposes the sensing channel during a high-temperature molding process at 165 °C. Experimental observations reveal that the silicon membrane of the pressure sensor is completely free of epoxy molding compound (EMC) contamination after the transfer molding process. The effectiveness of the dam-ring in shielding the silicon membrane of the pressure sensor during the molding process was confirmed. The packaged pressure sensor exerts a thermo-mechanical stress on the silicon membrane of the pressure sensor, resulting in an undesired output voltage drift. However, employing a package design with a large sensing channel opening can reduce the effect of package-induced stress. The proposed packaging scheme was a small package volume and surface-mount device (SMD) compatible features, making it suitable for portable commercial devices.