Capacitive pressure transducer

Abstract

A capacitive pressure transducer is disclosed in which a preformed metallic component is embedded in a nonconductive base substrate and acts as a first capacitor electrode. A silicon diaphragm acts as a second pressure sensing capacitor electrode whose spacing from the first electrode is determined by sensed pressure. The preformed metallic component forming the first capacitor electrode has an integral projecting portion which extends through the base substrate and provides an externally accessible electrical connection to the first electrode. A top external surface of the first electrode is ground flat so that it is coplanar with surrounding coplanar portions of a top surface of the base substrate. An additional preformed metallic conductor means is embedded in the base substrate and provides an externally accessible bottom side connection to the silicon diaphragm which is bonded to the base top surface. In some embodiments, the integral projecting portion of the first electrode has a through path opening therein to provide external access to an internal cavity formed by the silicon diaphragm, the external top surface of the base electrode and coplanar portions of the top surface of the base which surround the first electrode top external surface. Pressure transducers constructed in accordance with the present invention are more reliable and less costly because of elimination of prior techniques used to provide the base substrate electrode and the electrical feedthrough connections through the base substrate. In addition, repeatability of pressure transducers constructed in accordance with the present invention is enhanced.