Isolation technique for pressure sensing structure

• US 20030150275A1
• Filed: 02/20/2003
• Published: 08/14/2003
• Est. Priority Date: 01/19/2000
• Status: Active Grant

• Current Assignee: David E. Wagner, Gerald Lopopolo, James H. Hoffman
• Original Assignee: David E. Wagner, Gerald Lopopolo, James H. Hoffman
• Inventors: Lopopolo, Gerald, Wagner, David E., Hoffman, James H.
• Granted Patent: US 6,938,490 B2
• Time in Patent Office: Days
• 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, pressure-sensitive electronic components 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.

2. Pressure sensor of claim 1 further comprising:

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

a diaphragm extending between said reservoir and a space, whereby said diaphragm and said liquid are used to communicate pressure in said space to said pressure sensing die.

3. Pressure sensor of claim 1 wherein said die comprises a semiconductor material and said pressure-sensitive electronic components are resistors formed in said first surface, said die comprising:

a frame portion; and

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

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

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

6. Pressure sensor of claim 4 wherein said support structure comprises glass, and said die is bonded to said support structure with a low temperature glass.

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

C.

8. 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 components so that the resistance of said pressure-sensitive electronic components can be measured via said bonding wires, and wherein said bonding wires are not exposed to a liquid environment.

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

10. Pressure sensor of claim 1 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.

11. Pressure sensor of claim 10 further comprising a reservoir containing said liquid, wherein a tube extends through said glass, said reservoir being in fluid communication with said die via said tube.

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

13. Pressure sensor of claim 1 further comprising a reservoir containing said liquid, 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 header by brazing, welding or soldering.

14. 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.

15. Pressure sensor of claim 1 further comprising a reservoir for containing said liquid, said plate comprising a fill hole for permitting said liquid to be introduced into said reservoir, said fill hole being sealed.

16. 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.

17. Pressure sensor of claim 16 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. A pressure sensor comprising:

a plate having an outer periphery, said plate being mounted at its outer periphery to a second structure that holds said plate;

a pressure sensing die mounted to a centrally located portion of said plate, portions of said plate surrounding said pressure sensing die being thinned to reduce the amount of mechanical stress, if any, communicated from the outer periphery of said plate to said die.

19. Pressure sensor of claim 18 wherein said plate has a hole extending therethrough and said die is mounted over said hole, a liquid in said hole applying pressure to said die, said die providing a measure of said pressure.

20. Pressure sensor of claim 18 further comprising a support structure mounted on said plate, said die being mounted on said support structure.

21. A pressure sensor comprising:

a plate formed from a first material characterized by having a first coefficient of thermal expansion, said plate having an opening therein;

second material within said opening, said second material characterized by having a second coefficient of thermal expansion;

a pressure sensing die mounted on said second material, wherein said coefficient of thermal expansion of said die is closer to the second coefficient of thermal expansion than said first coefficient of thermal expansion.

22. Sensor of claim 21 wherein a support structure is mounted on said second material, and said die is mounted on said support structure.

23. Sensor of claim 21 wherein a tube extends through said second material, said tube containing a liquid, said liquid applying pressure to said die, said die providing a measure of the pressure applied by said liquid to said die.

24. Sensor of claim 21 further comprising an opening extending through said second material for introducing a liquid into said pressure sensor, said opening being sealed.

25. A pressure sensor comprising:

a Hastalloy plate;

a stainless steel diaphragm welded to said Hastalloy plate, the space between said stainless steel diaphragm and said plate forming a cavity for containing a liquid;

a stainless steel port welded to said Hastalloy plate, said port communicating a fluid under pressure to said stainless steel diaphragm; and

a pressure sensing diaphragm coupled to said plate, said plate having an opening for communicating said liquid to said diaphragm, said diaphragm sensing the pressure of said liquid.

26. A pressure sensor comprising:

a plate formed of a first material, said plate comprising an opening formed therein;

a second material in said opening;

a tube extending through said second material, a top surface of said tube extending beyond the surface of said second material;

a support structure mounted on said second material, said support structure comprising an opening surrounding the portion of said tube extending beyond the top surface of said second material; and

a pressure sensing die mounted on said support structure.

27. A pressure sensor comprising:

a plate;

a tube extending through said plate and above the surface of said plate;

a pressure sensing die;

a support structure bonded to said pressure sensing die, said support structure having an opening therein, said tube extending into said opening, the portion of said tube extending into said opening being bonded to said support structure, said tube communicating fluid to said pressure sensing die, whereby said pressure sensing die provides a measure of the pressure of said fluid.