SEMICONDUCTOR STRAIN GAGE PRESSURE TRANSDUCER

• US 3,697,917 A
• Filed: 08/02/1971
• Issued: 10/10/1972
• Est. Priority Date: 08/02/1971
• Status: Expired due to Term

• Current Assignee: Babcock & Wilcox Construction Company Incorporated (Babcock International Group PLC)
• Original Assignee: Alexander J. Yerman, Edward D. Orth
• Inventors: Orth, Edward D., Yerman, Alexander J.
• Primary Examiner(s): Albritton, C. L.
• Application Number:
  US05/168,278
• Time in Patent Office: 435 Days
• Field of Search: 338/2,3,4,42 73/88.5SD,398AR 317/235M
• US Class Current: 338/2
• CPC Class Codes: G01L 19/0084 to the outside of the housing other details about the housing see G01L19/14
• CPC Class Codes: G01L 19/143 Two part housings

Abstract

In a pressure transducer of the type utilizing a silicon strain gage diaphragm as a pressure sensor, the diaphragm is bonded to a tubular glass support by an anodic bonding process. Thermally induced stresses and resulting measurement errors are avoided by matching the expansion coefficients of the silicon diaphragm and the glass support. To withstand high operating pressures, the glass diaphragm support is mounted and sealed in the transducer housing so that it is subjected only to compressive forces under operating conditions.

Claims

1. A pressure transducer comprising:

a. a housing having walls forming a chamber adapted to be connected to a source of pressure to be measured;

b. a diaphragm formed of monocrystalline silicon having disposed on one side of an active area thereof a pattern of piezoresistive strain gages;

c. a cylindrical support member for the diaphragm formed of glass with an axial bore, the diaphragm having a restrained edge portion integrally bonded to one end of the glass support member so that the active diaphragm area overlies the axial bore;

d. means mounting the support member on the housing in sealed relation therewith so that the end carrying the diaphragm and adjacent side portions of the support project into the chamber in spaced relation to the housing walls and with the axial bore at the opposite end of the support opening outside the housing whereby the diaphragm is isolated from mechanical mounting strains and the glass supporting member is stressed in compression when the chamber is pressurized; and

e. electrical conductors connected to the strain gage and passing outwardly from the housing.

2. The pressure transducer of claim 1 wherein the diaphragm support member is formed of a borosilicate glass having a temperature coefficient of expansion approximately equal to that of the silicon diaphragm to reduce diaphragm strains caused by temperature changes.

3. The pressure transducer of claim 1 wherein the electrical conductors comprise spaced strips of conducting material carried on a strip of insulating substrate extending through the bore.

4. A pressure transducer comprising:

a. a housing having interior walls forming a pressure chamber; and

b. a diaphragm assembly mounted on the housing so as to project into the pressure chamber, the diaphragm assembly comprising;

i. an elongated glass support having an axial bore; and

ii, a strain-sensitive silicon diaphragm mounted on one end of the support so as to overlie the bore, the diaphragm having a restrained outer edge portion integrally bonded to the support by an anodic bonding process.

5. The pressure transducer of claim 4 including electrical conductors fastened the underside of the diaphragm and extending through the bore outside of the housing.

6. The pressure transducer of claim 5 including an insulating strip supporting the conductors, said strip being dimensioned to be received in the bore.