Capacitive pressure sensor or capacitive differential pressure sensor

• US 6,374,680 B1
• Filed: 02/21/2000
• Issued: 04/23/2002
• Est. Priority Date: 03/24/1999
• Status: Expired due to Fees

• Current Assignee: Endress+Hauser GmbH+Co (ENDRESS)
• Original Assignee: Endress+Hauser GmbH+Co (ENDRESS)
• Inventors: Hegner, Frank, Rossberg, Andreas, Drewes, Ulfert, Schmidt, Elke, Velten, Thomas
• Primary Examiner(s): Fuller, Benjamin R.
• Assistant Examiner(s): AW MUSSE, ABDULLAHI H
• Application Number:
  US09/511,723
• Time in Patent Office: 792 Days
• Field of Search: 737/24, 737/18, 737/15, 737/23, 737/17, 361/283.4, 361/283
• US Class Current: 73/718
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass

Abstract

The electrodes of these pressure or differential pressure sensors are formed using a technique other than silk-screen printing or sputtering: The pressure sensor (10) has a substrate (1) and a first major surface (11), a second major surface (12) and a circumferential surface (13. A plate-shaped electrode (14) of electrically conductive material is secured in a recess (15) in the major surface (11) in a high-pressure-resistant and high-vacuum-tight manner by a joining material (16). A through connection (17) is provided from the electrode (14) through the substrate (1) to the major surface (12) or the circumferential surface (13). A diaphragm (2) of ceramic, glass, or single-crystal material is attached to the substrate (1) outside the recess (15) along a joint (18) by a joining material (26), and forms itself a further electrode or is covered, on a surface facing the electrode (14), with a further electrode (24) which is contacted through the joint (18). Substrate and diaphragm consist of a ceramic, glass, or single-crystal material. Respective differential pressure sensors have either a common central diaphragm and two substrates or a common substrate and two diaphragms.

Claims

1. A capacitive pressure sensor comprising:

a substrate including at least one of a ceramic, glass, or single-crystal material, the substrate having a generally planar first major surface formed to include a recess, a second major surface, and a circumferential surface;

a plate-shaped first electrode of electrically conductive material

which is secured in the recess in the first major surface in a high-pressure-resistant and high-vacuum-tight manner by a first joining material,

the first electrode including a generally planar outer surface and occupying the recess so that the generally planar outer surface is coplanar with the first major surface of the substrate;

a through connection from the first electrode through the substrate to one of the second major surface and the circumferential surface;

a diaphragm including at least one of a ceramic, glass, or single-crystal material,

the diaphragm being attached to the substrate outside the recess along a joint in spaced relation to the first electrode by a second joining material; and

a second electrode which is positioned adjacent the first electrode by the diaphragm.

2. The pressure sensor as claimed in claim 1 wherein the plate-shaped electrode is made of a metal whose coefficient of thermal expansion is matched to that of the ceramic, glass, or single-crystal material.

3. The pressure sensor as claimed in claim 1 wherein the plate-shaped electrode is made of an electrically conductive ceramic or an electrically conductive glass.

4. The pressure sensor as claimed in claim 3 wherein the electrically conductive ceramic is a cermet.

5. The pressure sensor as claimed in claim 3 wherein the electrically conductive ceramic is a dispersive ceramic.

6. The pressure sensor as claimed in claim 3 wherein the plate-shaped electrode is made of a material selected from the group consisting of silicon carbide, titanium carbide, titanium nitride, titanium diboride, molybdenum disilicide, tungsten carbide, and zirconium carbide.

7. The pressure sensor as claimed in claim 3 wherein the plate-shaped electrodes is sintered without the first joining material.

8. The pressure sensor as claimed in claim 4 wherein the plate-shaped electrodes is sintered without the first joining material.

9. The pressure sensor as claimed in claim 5 wherein the plate-shaped electrodes is sintered without the first joining material.

10. The pressure sensor as claimed in claim 6 wherein the plate-shaped electrodes is sintered without the first joining material.

13. The differential pressure sensor as claimed in claim 2 wherein the plate-shaped electrodes are made of a metal whose coefficient of thermal expansion is matched to that of the ceramic, glass, or single-crystal material.

14. The differential pressure sensor as claimed in claim 2 wherein the plate-shaped electrodes are made of an electrically conductive ceramic or an electrically conductive glass.

15. The differential pressure sensor as claimed in claim 14 wherein the electrically conductive ceramic is a cermet.

16. The differential pressure sensor as claimed in claim 14 wherein the electrically conductive ceramic is a dispersive ceramic.

17. The differential pressure sensor as claimed in claim 14 wherein the plate-shaped electrode is made of a material selected from the group consisting of silicon carbide, titanium carbide, titanium nitride, titanium diboride, molybdenum disilicide, tungsten carbide, and zirconium carbide.

18. The pressure sensor as claimed in claim 14 wherein the plate-shaped electrodes is sintered without the first joining material.

19. The pressure sensor as claimed in claim 15 wherein the plate-shaped electrodes is sintered without the first joining material.

20. The pressure sensor as claimed in claim 16 wherein the plate-shaped electrodes is sintered without the first joining material.

21. The pressure sensor as claimed in claim 17 wherein the plate-shaped electrodes is sintered without the first joining material.

22. The differential pressure sensor as claimed in claim 3 wherein the plate-shaped electrodes are made of a metal whose coefficient of thermal expansion is matched to that of the ceramic, glass, or single-crystal material.

23. The differential pressure sensor as claimed in claim 3 wherein the plate-shaped electrodes are made of an electrically conductive ceramic or an electrically conductive glass.

31. The capacitive pressure sensor of claim 1, wherein the diaphragm forms the second electrode.

35. The pressure sensor as claimed in claim 1, wherein the diaphragm is the second electrode.

36. The pressure sensor as claimed in claim 1, wherein the diaphragm is at least partially covered by the second electrode.

11. A capacitive differential pressure sensor comprising:

a first substrate including at least one of a ceramic, glass, or single-crystal material, the first substrate having a generally planar first major surface formed to include a first recess, a second major surface, and a circumferential surface;

a plate-shaped first electrode of electrically conductive material

which is secured in the first recess in the first major surface of the first substrate in a high-pressure-resistant and high-vacuum-tight manner by a first joining material;

the first electrode including a first generally planar outer surface and occupying the first recess so that the first generally planar outer surface is coplanar with the first major surface of the first substrate;

a first through connection from the first electrode through the first substrate to one of the second major surface and the circumferential surface of the first substrate;

a second substrate including at least one of a ceramic, glass, or single-crystal material, the second substrate having a first major surface formed to include a second recess, a second major surface and a circumferential surface;

a plate-shaped second electrode of electrically conductive material

which is secured in the second recess in the first major surface of the second substrate in a high-pressure-resistant and high-vacuum-tight manner by the first joining material;

the second electrode including a second generally planar outer surface and occupying the second recess so that the second generally planar outer surface is coplanar with the first major surface of the second substrate;

a second through connection from the second electrode through the second substrate to one of the second major surface and the circumferential surface of the second substrate;

a diaphragm including at least one of a ceramic, glass, or single-crystal material which

is attached to the first substrate outside the first recess along a first joint in spaced relation to the first electrode by a second joining material and

is attached to the second substrate outside the second recess along a second joint in spaced relation to the second electrode by the second joining material;

a third electrode on the diaphragm, the third electrode facing the first electrode; and

a fourth electrode on the diaphragm, the fourth electrode facing the second electrode.

32. The capacitive differential pressure sensor of claim 11, wherein the diaphragm forms the third electrode.

37. The pressure sensor as claimed in claim 11, wherein the diaphragm is at least one of the third electrode and the fourth electrode.

38. The pressure sensor as claimed in claim 11, wherein the diaphragm is the third electrode and the fourth electrode.

39. The pressure sensor as claimed in claim 11, wherein the diaphragm is at least partially covered by at least one of the third electrode and the fourth electrode.

40. The pressure sensor as claimed in claim 11, wherein the diaphragm is at least partially covered by the third electrode and the diaphragm is at least partially covered by the fourth electrode.

12. A capacitive differential pressure sensor comprising:

a substrate including at least one of a ceramic, glass, or single-crystal material, the substrate having a generally planar first major surface formed to include a first recess, a second major surface formed to include a second recess, and a circumferential surface;

a plate-shaped first electrode of electrically conductive material

which is secured in the first recess in the first major surface in a high-pressure-resistant and high-vacuum-tight manner by a first joining material,

the first electrode including a first generally planar outer surface and occupying the first recess so that the first generally planar outer surface is coplanar with the first major surface of the substrate;

a plate-shaped second electrode of electrically conductive material

which is secured in the second recess in the second major surface in a high-pressure-resistant and high-vacuum-tight manner by the first joining material,

the second electrode including a second generally planar outer surface and occupying the second recess so that the second generally planar outer surface is coplanar with the second major surface of the substrate;

a first through connection from the first electrode through the substrate to the circumferential surface;

a second through connection from the second electrode through the substrate to the circumferential surface, the second through connection being separate from the first through connection;

a first diaphragm including at least one of a ceramic, glass, or single-crystal material,

the first diaphragm being attached to the substrate outside the first recess along a first joint in spaced relation to the first electrode by a second joining material;

a third electrode which is positioned adjacent the first electrode by the first diaphragm;

a second diaphragm including at least one of a ceramic, glass, or single-crystal material,

the second diaphragm being attached to the substrate outside the second recess along a second joint in spaced relation to the second electrode by the second joining material; and

a fourth electrode which is positioned adjacent the second electrode by the second diaphragm.

33. The capacitive differential pressure sensor of claim 12, wherein the first diaphragm forms the third electrode.

34. The capacitive differential pressure sensor of claim 12, wherein the second diaphragm forms the fourth electrode.

41. The pressure sensor as claimed in claim 12, wherein the first diaphragm is the third electrode.

42. The pressure sensor as claimed in claim 12, wherein the first diaphragm is at least partially covered by the third electrode.

43. The pressure sensor as claimed in claim 12, wherein the second diaphragm is the fourth electrode.

44. The pressure sensor as claimed in claim 12, wherein the second diaphragm is at least partially covered by the fourth electrode.

24. A pressure sensor apparatus comprising:

a substrate including a generally planar first surface formed to include a recess;

an electrically conductive first electrode coupled to the substrate and located within the recess, the first electrode including a generally planar outer surface and occupying the recess so that the generally planar surface is coplanar with the generally planar first surface of the substrate;

a diaphragm adjacent to the first electrode;

an electrically conductive second electrode which is positioned adjacent the first electrode by the diaphragm; and

a joining material configured to couple the diaphragm to the substrate so that the diaphragm extends over the recess and is spaced apart from the generally planar first surface of the substrate and from the generally planar outer surface of the first electrode by a predetermined distance, thereby providing a spacing of the predetermined distance between the first and second electrodes.

25. The apparatus of claim 24, wherein the substrate has a first coefficient of thermal expansion, the diaphragm has a second coefficient of thermal expansion, and the first electrode has a third coefficient of thermal expansion, the third coefficient of thermal expansion being matched to at least one of the first coefficient of thermal expansion and the second coefficient of thermal expansion.

26. The apparatus of claim 24, wherein the first electrode includes at least one of an electrically conductive ceramic material and an electrically conductive glass material.

27. The apparatus of claim 24, wherein the first electrode is formed from a cermet material.

28. The apparatus of claim 26, wherein the first electrode is formed from a dispersive ceramic material.

29. The apparatus of claim 26, wherein the first electrode includes a material selected from the group consisting of silicon carbide, titanium carbide, titanium nitride, titanium diboride, molybdenum disilicide, tungsten carbide, and zirconium carbide.

30. The apparatus of claim 24, wherein the first electrode is sintered to the substrate.

45. The pressure sensor as claimed in claim 24, wherein the diaphragm is the second electrode.

46. The pressure sensor as claimed in claim 24, wherein the diaphragm is at least partially covered by the second electrode.