Pressure sensor assembly with direct backside sensing

Abstract

An improved, low-cost, back-side sensing pressure sensor assembly having a high integrity seal between the sensor element and the pressure port. The pressure port has a stud portion at an inboard end for attachment to a pressure vessel wall, and a cup portion at an outboard end for housing the sensor and interface circuitry. A central well extends inward from an inboard face of the cup portion, and a central axial bore in the stud portion opens into the well. A planar carrier disc carrying the sensor element closes the outboard end of the well. The sensor element comprises a silicon diaphragm formed on the outboard end of a glass pedestal that passes through a complementary opening formed in the carrier disc, and the inboard end of the pedestal includes an integral radially extending rim or shoulder that seats on the inboard face of the carrier disc about the opening. A suitable adhesive is used to bond the pedestal rim to the disc, and in operation, the fluid pressure in the vessel places the adhesive joint in compression to provide a long term, high integrity, seal between the well and the remainder of the cup portion. In a first embodiment, the interface circuitry and conductor traces and pads that interconnect the sensor terminals are formed on the outboard face of the carrier disc, whereas in a second embodiment, the circuitry and conductor traces and pads are formed on a flexible circuit glued to the outboard face of the carrier disc.