Pressure sensor assembly

• US 4,703,658 A
• Filed: 06/18/1986
• Issued: 11/03/1987
• Est. Priority Date: 06/18/1986
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Greenstein, Bernard, Mrozack, James Jr.
• Primary Examiner(s): Woodiel, Donald O.
• Application Number:
  US06/876,067
• Time in Patent Office: 503 Days
• Field of Search: 73/724, 73/718, 73/DIG. 4, 361/283
• US Class Current: 73/724
• CPC Class Codes: G01L 19/0061 Electrical connection means
• CPC Class Codes: G01L 19/141 Monolithic housings, e.g. molded or one-piece housings
• CPC Class Codes: G01L 19/148 Details about the circuit board integration, e.g. integrated with the diaphragm surface or encapsulation
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm
• CPC Class Codes: Y10S 73/04 Piezoelectric

Abstract

A pressure sensor assembly includes a pressure transducer having a pressure displaceable diaphragm bonded to a base. Displacement of the diaphragm results in varying of electrical characterisitcs of the transducer in response to sensed pressure. Electrical output connections (wires) of the transducer extend from a central portion of a top surface of the base, which faces the diaphragm, to a central portion of a base bottom surface and peripheral portions of the diaphragm and base top surface are hermetically bonded together. The transducer is mounted on a carrier plate and integral extensions of the electrical output connections pass through holes in the carrier plate. A housing for the sensor assembly has an opening therein to provide access to the diaphragm by ambient atmosphere/fluid surrouding the housing. A first inner seal bonds at least the peripheral portions of the base bottom surface to the carrier plate, and a second outer seal is positioned between the carrier plate top surface and walls of the housing. The housing walls, carrier plate and first and second seals form an effective seal against ambient atmosphere/fluid which contacts the diaphragm and, therefore, seal and protect the electrical output connections of the transducer. The housing walls form an internal cavity which is isolated from the sensed ambient atmosphere/fluid. Within the internal cavity components are connected to the extensions of the clectrical output connections which pass through the carrier plate holes.

Claims

1. A pressure sensor assembly comprising:

a base having top and bottom external surfaces each having central and surrounding peripheral portions;

a diaphragm with a peripheral portion thereof hermetically bonded to said base top surface peripheral portion and forming a reference pressure cavity between said diaphragm and said base top surface;

said base and diaphragm together comprising a pressure transducer having electrical characteristics which vary in response to sensed pressure altering the position of said diaphragm with respect to said base; and

electrical output connections for said transducer including at least conductive portions embedded in and passing through said base from said central portion of said base top surface and emerging on said central portion of said base bottom surface;

the improvement comprising;

a carrier plate having a top surface to which said transducer is mounted and having holes therein for passage of effective extensions of said electrical output connections;

housing means for providing mechanical protection for pressure sensor assembly components while providing substantial access to said diaphragm by ambient atmosphere/fluid external to said housing means by way of an opening in said housing means;

first inner seal means for bonding at least the peripheral portions of said base bottom surface to said carrier plate to effectively seal said central area of said base bottom surface, from which said electrical output connections emerge, and said holes from ambient atmosphere/fluid surrounding said diaphragm; and

second outer seal means positioned between said carrier top surface and said housing means and positioned about said opening in said housing means such that said housing means, said first and second seal means and said carrier form an effective seal against ambient atmosphere/fluid surrounding and external to said diaphragm.

2. A pressure sensor assembly according to claim 1 wherein said first inner seal means comprises an inert nonmetallic material.

3. A pressure sensor assembly according to claim 2 wherein said inert nonmetallic material comprises a glass composition which has been heated so as to bond said base to said carrier plate.

4. A pressure sensor assembly according to claim 3 wherein said first inner seal means comprises, at least prior to said heating, first and second layers of glass material, said first layer positioned between said base bottom surface and said second layer and said second layer positioned between said first layer and said carrier top surface.

5. A pressure sensor assembly according to claim 4 wherein said first and second layers have different temperature coefficients of expansion, the temperature coefficient of expansion of said first layer being between but more closely matching the temperature coefficient of expansion of said base than said carrier plate while the temperature coefficient of said second layer being between but more closely matching the temperature coefficient of expansion of said carrier plate than said base.

6. A pressure sensor assembly according to claim 5 wherein said first inner seal means comprises screen printed layers of effectively different glass frits.

7. A pressure sensor assembly according to claim 5 wherein said first inner seal means comprises at least one glass preform positioned between said base and said carrier plate.

8. A pressure sensor assembly according to claim 3 wherein said first inner seal means comprises at least one layer of glass material which extends at least over substantially all of said base bottom surface.

9. A pressure sensor assembly according to claim 3 wherein said first inner seal means comprises an annular ring of glass material.

10. A pressure sensor assembly according to claim 3 wherein said embedded portions and effective extensions of said electrical output connections comprise wire with portions embedded in the base and integral extensions of said wires comprising said effective extensions.

11. A pressure sensor assembly according to claim 10 wherein said carrier plate comprises a ceramic plate.

12. A pressure sensor assembly according to claim 11 wherein said ceramic carrier plate is manufactured from aluminum oxide material.

13. A pressure sensor assembly according to claim 1 wherein said diaphragm is constructed from silicon material.

14. A pressure sensor assembly according to claim 13 wherein said base has a glass composition.

15. A pressure sensor assembly according to claim 14 wherein said silicon diaphragm and glass base are anodically bonded together.

16. A pressure sensor assembly according to claim 15 wherein said transducer comprises a capacitive pressure transducer and wherein said silicon diaphragm comprises one electrode of a pressure sensing capacitor and wherein a metal component/metallization is positioned on said base top surface as another electrode of said pressure sensing capacitor.

17. A pressure sensor assembly according to claim 16 wherein said first inner seal means comprises an inert nonmetallic material and wherein said inert nonmetallic material comprises a glass composition which has been heated so as to bond said base to said carrier plate.

18. A pressure sensor assembly according to claim 17 wherein said carrier plate comprises a ceramic plate.

19. A pressure sensor assembly according to claim 18 wherein said first inner seal means comprises, at least prior to said heating, first and second layers of glass material, said first layer positioned between said base bottom surface and said second layer and said second layer positioned between said first layer and said carrier top surface, and wherein said first and second layers have different temperature coefficients of expansion, the temperature coefficient of expansion of said first layer being between but more closely matching the temperature coefficient of expansion of said base than said carrier plate while the temperature coefficient of said second layer being between but more closely matching the temperature coefficient of expansion of said carrier plate than said base.

20. A pressure sensor assembly according to claim 1 wherein said housing means, said first and second seal means and said carrier plate effectively form an internal cavity isolated from the sensed ambient atmosphere/fluid, and wherein electrical components, electrically connected to said pressure transducer via said effective extensions of said electrical output connections, are positioned within said internal cavity.

21. A sensor assembly comprising:

a base having top and bottom external surfaces each having central and surrounding peripheral portions;

said base comprising at least part of a transducer having electrical characteristics which vary in response to a sensed parameter of an ambient atmosphere/fluid; and

electrical output connections for said transducer including at least conductive portions embedded in and passing through said base from said central portion of said base top surface and emerging on said central portion of said base bottom surface;

the improvement comprising;

a carrier plate having a top surface to which said transducer is mounted and having holes therein for passage of effective extensions of said electrical output connections;

housing means for providing mechanical protection for pressure sensor assembly components while providing substantial access to said transducer by ambient atmosphere/fluid external to said housing means by way of an opening in said housing means;

first inner seal means for bonding at least the peripheral portions of said base bottom surface to said carrier plate to effectively seal said central area of said base bottom surface, from which said electrical output connections emerge, and said holes from ambient atmosphere/fluid surrounding said transducer; and

second outer seal means positioned between said carrier top surface and said housing means and positioned about said opening in said housing means such that said housing means, said first and second seal means and said carrier form an effective seal against ambient atmosphere/fluid surrounding and external to said transducer.

22. A pressure sensor assembly according to claim 21 wherein said first inner seal means comprises an inert nonmetallic material.

23. A pressure sensor assembly according to claim 22 wherein said inert nonmetallic material comprises a glass composition which has been heated so as to bond said base to said carrier plate.

24. A pressure sensor assembly according to claim 23 wherein said first inner seal means comprises, at least prior to said heating, first and second layers of glass material, said first layer positioned between said base bottom surface and said second layer and said second layer positioned between said first layer and said carrier top surface.

25. A pressure sensor assembly according to claim 24 wherein said first and second layers have different temperature coefficients of expansion, the temperature coefficient of expansion of said first layer being between but more closely matching the temperature coefficient of expansion of said base than said carrier plate while the temperature coefficient of said second layer being between but more closely matching the temperature coefficient of expansion of said carrier plate than said base.

26. A pressure sensor assembly according to claim 25 wherein said first inner seal means comprises screen printed layers of effectively different glass frits.

27. A pressure sensor assembly according to claim 25 wherein said first inner seal means comprises at least one glass preform positioned between said base and said carrier plate.

28. A pressure sensor assembly according to claim 23 wherein said first inner seal means comprises at least one layer of glass material which extends at least over substantially all of said base bottom surface.

29. A pressure sensor assembly according to claim 23 wherein said first inner seal means comprises an annular ring of glass material

30. A pressure sensor assembly according to claim 23 wherein said embedded portions and effective extensions of said electrical output connections comprise wire with portions embedded in the base and integral extensions of said wires comprising said effective extensions.