Micro-electromechanical pressure sensor having reduced thermally-induced stress

• US 8,796,866 B2
• Filed: 10/16/2012
• Issued: 08/05/2014
• Est. Priority Date: 10/16/2012
• Status: Active Grant

• Current Assignee: Vitesco Technologies USA, LLC (Continental AG)
• Original Assignee: Continenal Automotive Systems, Inc.
• Inventors: Wang, Joe Pin
• Primary Examiner(s): Reames, Matthew
• Assistant Examiner(s): NGUYEN, DILINH P
• Application Number:
  US13/652,739
• Publication Number:
  US 20140103468A1
• Time in Patent Office: 658 Days
• Field of Search: 257/782, 257/783, 257/786, 257/419, 257/787, 257/731, 257/747
• US Class Current: 257/783
• CPC Class Codes: B81B 2201/0264 Pressure sensors
• CPC Class Codes: B81B 7/0048 between the MEMS die and the substrate
• CPC Class Codes: B81C 2203/032 Gluing
• CPC Class Codes: G01L 19/04 Means for compensating for effects of changes of temperature , i.e. other than electric compensation
• CPC Class Codes: G01L 9/0054 integral with a semiconducting diaphragm

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 C_TE fillers that lowers the plastic'"'"'s coefficient of thermal expansion (C_TE) 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 C_TE between about ten PPM/° C. and about thirty PPM/° C. in order to match the housing C_TE. 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.

Claims

1. 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 (C_TE) 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 C_TE 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.

2. The pressure sensor of claim 1, wherein the adhesive comprises an organic epoxy having a C_TE between about nineteen PPM/°

C. and about twenty-four PPM/°

C. and further having a glass transition temperature (T_g) of at least one hundred seventy degrees Celsius (170°

C.), and wherein the mineral filler comprises a predetermined amount of silica, the organic epoxy being mixed with the predetermined amount of the silica filler to form a mixture of epoxy and silica filler.

3. The pressure sensor of claim 2, wherein the predetermined amount of silica filler is between about fifty percent and about eighty percent of the weight of the mixture.

4. The pressure sensor of claim 2, wherein the predetermined amount of silica filler is about sixty-five percent of the weight of the mixture of adhesive and filler.