Isolation technique for pressure sensing structure

• US 6,550,337 B1
• Filed: 01/19/2000
• Issued: 04/22/2003
• Est. Priority Date: 01/19/2000
• Status: Expired due to Term

• Current Assignee: Silicon Valley Sensors Incorporated
• Original Assignee: Measurement Specialties Incorporated (TE Connectivity Limited)
• Inventors: Lopopolo, Gerald, Wagner, David E., Hoffman, James H.
• Primary Examiner(s): MCCALL, ERIC SCOTT
• Application Number:
  US09/489,560
• Time in Patent Office: 1,189 Days
• Field of Search: 737/15, 737/17, 737/56, 737/18, 737/20, 737/21, 737/23, 737/26, 737/25, 737/24, 361/283, 361/283.4
• US Class Current: 73/715
• CPC Class Codes: G01L 19/0069 from the sensor to its support
• CPC Class Codes: G01L 19/0645 using isolation membranes, specially adapted for protection
• CPC Class Codes: G01L 19/146 using flexible element between the transducer and the support
• CPC Class Codes: G01L 19/147 Details about the mounting of the sensor to support or covering means
• CPC Class Codes: G01L 9/0042 Constructional details associated with semiconductive diaphragm sensors, e.g. etching, or constructional details of non-semiconductive diaphragms details about the integration or bonding of piezoresistor in or on the diaphragm G01L9/0052 and G01L9/0057 respectively
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 2224/48465 the other connecting portion not on the bonding area being a wedge bond, i.e. ball-to-wedge, regular stitch
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/15151 the die mounting substrate comprising an aperture, e.g. for underfilling, outgassing, window type wire connections

Abstract

An electronic pressure-sensing device is isolated from corrosive, conductive gasses and fluids by a corrosion resistant metal diaphragm welded to a pressure port. The pressure-sensing device is attached to a support structure with a hole that provides a path from the diaphragm area to the pressure-sensing device. A fill fluid is sealed behind the diaphragm and fills the hole through the support structure to the electronic pressure-sensing device. In this design, any hostile chemical applied is completely isolated from the electronic sensor and associated adhesive seals by the metal diaphragm.

Claims

1. A pressure sensor comprising:

a pressure sensing die having a first surface and a second surface, a pressure sensitive electronic component being formed in or on said first surface;

a plate having a hole therein, said second surface of said pressure sensing die being affixed to said plate such that at least a portion of said second surface is in fluid communication with said hole, liquid being provided in said hole and pressing against said portion of said second surface, wherein said pressure sensing die provides a measure of the pressure with which said liquid presses against said die, and wherein said first surface is not in a liquid environment;

a reservoir containing said liquid, said reservoir being in fluid communication with said pressure sensing die through said hole in said plate; and

a diaphragm extending between said reservoir and a space, said diaphragm and said liquid applying pressure in said space to said pressure sensing die.

2. Pressure sensor of claim 1 wherein said die comprises a semiconductor material and said pressure-sensitive electronic component is a resistor formed in said first surface, said die comprising:

a frame portion; and

a diaphragm portion, said frame portion surrounding and being contiguous with said diaphragm portion, said resistor being formed in said diaphragm portion.

3. Pressure sensor of claim 1 wherein said die is affixed to a support structure and said support structure is affixed to said plate.

4. Pressure sensor of claim 3 wherein said support structure comprises glass, and said die is anodically bonded to said glass.

5. Pressure sensor of claim 3 wherein said support structure comprises glass, and said die is bonded to said support structure with a low temperature glass.

6. Pressure sensor of claim 5 wherein said low temperature glass has a melting point less than or equal to about 750°

C.

7. Pressure sensor of claim 1 further comprising a set of bonding wires affixed to said first side of said die and electrically coupled to said pressure-sensitive electronic component so that a resistance of said pressure-sensitive electronic component can be measured via said bonding wires, and wherein said bonding wires are not exposed to a liquid environment.

8. Pressure sensor of claim 1 wherein said plate comprises Hastalloy.

9. Pressure sensor of claim 3 wherein said plate is metallic, a hole extending through said plate, glass being formed in said hole, said support structure being affixed to said glass.

10. Pressure sensor of claim 9 wherein a tube extends through said glass, said reservoir being in fluid communication with said die via said tube.

11. Pressure sensor of claim 10 wherein a portion of said tube extends above the surface of said plate, and said support structure surrounds said portion of said tube.

12. Pressure sensor of claim 1 wherein a tube extends through said plate, said reservoir being in fluid communication with said die via said tube, said tube being bonded to said plate by brazing, welding or soldering.

13. Pressure sensor of claim 1 wherein portions of said plate are thinned to permit said plate to flex at said thinned portions, whereby said plate at least partially insulates said die from mechanical force applied to the periphery of said plate.

14. Pressure sensor of claim 1 wherein said plate comprises a fill hole for permitting said liquid to be introduced into said reservoir, said fill hole being sealed.

15. Pressure sensor of claim 1 further comprising a cap formed over said die such that there is a cavity between said die and said cap, said cavity containing a vacuum.

16. Pressure sensor of claim 15 wherein said pressure sensor contains a pressure sensitive capacitive element having at least a first plate and a second plate, wherein said first plate is formed on said cap, and said second plate is formed on said die.

18. Pressure sensor of claim 1 wherein pressure sensitive resistors are formed in or on said die.

17. A pressure sensor comprising:

a pressure sensing die having a first surface and a second surface, a pressure sensitive electronic component being formed in or on said pressure sensing die;

one or more bonding wires electrically connected to a first side of said pressure sensing die for electrically accessing said pressure sensitive electronic component;

a plate having a hole therein, said second surface of said pressure sensing die being affixed to said plate such that at least a portion of said second surface is in fluid communication with said hole, liquid being provided in said hole and pressing against said portion of said second surface, wherein said pressure sensing die provides a measure of the pressure with which said liquid presses against said die, and wherein said first surface is not in a liquid environment;

a reservoir containing said liquid, said reservoir being in fluid communication with said pressure sensing die through said hole in said plate; and

a diaphragm extending between said reservoir and a space, said diaphragm and said liquid applying pressure in said space to said pressure sensing die, said pressure sensing die measuring said pressure.

19. Pressure sensor of claim 17 wherein pressure sensitive resistors are formed in or on said die.

20. Pressure sensor of claim 17 wherein said die is affixed to a support structure and said support structure is affixed to said plate.

21. A pressure sensor comprising:

a pressure sensing die having a first surface and a second surface, a pressure sensitive electronic component being formed in or on said first surface;

a plate having a hole therein, said second surface of said pressure sensing die being affixed to said plate such that at least a portion of said second surface is in fluid communication with said hole, liquid being provided in said hole and pressing against said portion of said second surface, wherein said pressure sensing die provides a measure of the pressure with which said liquid presses against said die, and wherein said first surface is not in a liquid environment, and

a diaphragm extending between said liquid and a space, said diaphragm and said liquid applying pressure in said space to said pressure sensing die.

22. Pressure sensor of claim 21 wherein said die is affixed to a support structure and said support structure is affixed to said plate.

23. A pressure sensor comprising:

a pressure sensing die having a first surface and a second surface, a pressure sensitive electronic component being formed in or on said pressure sensing die;

one or more bonding wires electrically connected to a first side of said pressure sensing die for electrically accessing said pressure sensitive electronic component;

a plate having a hole therein, said second surface of said pressure sensing die being affixed to said plate such that at least a portion of said second surface is in fluid communication with said hole, liquid being provided in said hole and pressing against said portion of said second surface, wherein said pressure sensing die provides a measure of the pressure with which said liquid presses against said die, and wherein said first surface is not in a liquid environment; and

a diaphragm extending between said liquid and a space, said diaphragm and said liquid applying pressure in said space to said pressure sensing die.

24. Pressure sensor of claim 23 wherein said die is affixed to a support structure and said support structure is affixed to said plate.