Micro-electromechanical pressure sensor having reduced thermally-induced stress
AssigneeContinential Automotive Systems, Inc.
InventorJoe Pin Wang
Life of this patent
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Abstract
Thermally-induced stress on a silicon micro-electromechanical pressure transducer (MEMS sensor) is reduced by attaching the MEMS sensor to a plastic filled with low CTE fillers that lowers the plastic's coefficient of thermal expansion (CTE) to be closer to that of silicon. The MEMS sensor is attached to the housing using an epoxy adhesive/silica filler mixture, which when cured has a CTE between about ten PPM/° C. and about thirty PPM/° C. in order to match the housing CTE. The adhesive also has a glass transition temperature (Tg) above the operating temperature range. This design provides good sealing of the sensor and stable sensor outputs.
Claims4
A pressure sensor comprising:
- a micro-electromechanical pressure transducer (MEMS sensor) formed from silicon and comprising a diaphragm, the MEMS sensor having a coefficient of thermal expansion (CTE) between about 1 part per million (PPM) per degree Celsius (/° C.) and about 5 PPM/° C.;
- a plastic housing formed from first amount of polyphenylene sulfide (PPS) and a second amount of a filler comprising glass and a mineral, the plastic housing having a weight, about forty-percent of which is PPS, about sixty-percent of which is the filler, the plastic housing comprising a mounting surface for the MEMS sensor and having a pressure port configured to permit fluid to apply pressure to the diaphragm, the amount of PPS and the amount of fillers being selected such that the plastic housing has a coefficient of thermal expansion between about ten (10) parts per million (PPM) per degree Celsius (/° C.) and about thirty (30) PPM/° C.;
- and
- an adhesive comprising a first amount of an organic epoxy mixed with a second amount of a mineral filler, about sixty-five percent of the adhesive weight being the mineral filler such that the adhesive has a CTE between about ten PPM/° C.) and about thirty PPM/° C., the adhesive being located between the mounting surface and the MEMS sensor thereby attaching the MEMS sensor to the mounting surface.
Dependencies are inferred from the claim text.