Capacitive pressure sensor cells or differential pressure sensor cells and methods for manufacturing the same

• US 6,267,009 B1
• Filed: 02/16/2000
• Issued: 07/31/2001
• Est. Priority Date: 12/14/1998
• 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:
  US09/505,489
• Time in Patent Office: 531 Days
• Field of Search: 737/18, 737/24, 737/15, 737/16, 737/17, 361/283.4, 361/283, 29/254.1
• US Class Current: 73/718
• CPC Class Codes: G01L 9/0044 Constructional details of non-semiconductive diaphragms
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass

Abstract

These capacitive pressure sensor cells have joints between substrates and diaphragms being both pressure and/or tension-proof and high-vacuum-tight and long-term-stable. The sensor cell comprises a ceramic substrate (1) having a cylindrical surface (11), a major surfaces (12, 13). The major surface (12) includes a concave central area (121) merging, in the direction of and up to said cylindrical surface (11), into a convex surface (124) having a vertex line (125) and forming a planar ring surface (126) in its area. An electrode (122) is located in the concave area (121). An electrical connection (123) extends from electrode (122) through the substrate (1) to surface (13). A ceramic diaphragm (5) has a planar inner surface (51) on which an electrode (52) is located and which rests on the ring surface (126) of the substrate (1). The diaphragm (5) is joined to the substrate by an active brazing solder forming a circumferential wedge zone (91) in the area of the substrate between the ring surface (126) and the cylindrical surface (11). An electrical connection to the electrode (52) is made through the wedge zone (91). Respective differential pressure sensors can comprise a central substrate (2) and two outer diaphragms (61, 71) or a central diaphragm (8) and two outer substrates (3, 4).

Claims

1. A capacitive pressure sensor cell comprising:

a ceramic substrate having

a cylindrical surface,

a first major surface and

a second major surface,

said second major surface being opposite said first major surface,

said first major surface including a concave central area which, as the concave central area extends toward said cylindrical surface, merges into a convex surface having a vertex line,

said convex surface forming a planar ring surface proximate to said vertex line,

a first electrode located in said concave central area of said first major surface, and

an electrical connection extending from said first electrode through said substrate to said second major surface; and

a ceramic diaphragm having a planar inner surface,

a second electrode located on said planar inner surface of said diaphragm,

said planar inner surface of said diaphragm resting on said planar ring surface of said first major surface of said substrate,

said diaphragm being joined to said substrate by an active brazing solder

which is located in a circumferential wedge zone formed between said diaphragm and said substrate and between said planar ring surface and said cylindrical surface, the circumferential wedge zone being configured to inhibit the active brazing solder from entering the concave central area,

a high-vacuum-tight sensing chamber being formed between said planar inner surface of said diaphragm and said first major surface of said substrate, and

electrical connection to said second electrode being made through said circumferential wedge zone.

2. The pressure sensor cell as claimed in claim 1 wherein the substrate and the diaphragm are made of alumina ceramic, and the active brazing solder is a Zr—

Fe—

Ti—

Be alloy or a Zr—

Ni—

Ti alloy.

3. The pressure sensor cell as claimed in claim 1 wherein at lease the electrode of the diaphragm is covered, at least in a respective edge region, with a solder resist layer.

4. A capacitive differential pressure sensor cell comprising:

a ceramic substrate having

a cylindrical surface and,

at a first major surface, a concave first central area which

is provided with a first electrode,

has a first electrical connection from the first electrode through the substrate to a second major surface, and,

as the concave first central area extends toward the cylindrical surface, merges into a convex first surface having a first vertex line,

said convex first surface forming a first planar ring surface proximate to the first vertex line,

which substrate further has, at a second major surface opposite the first major surface, a concave second central area which

is provided with a second electrode,

has a second electrical connection from the second electrode through the substrate to the cylindrical surface, and,

as the concave second central area extends toward the cylindrical surface, merges into a convex second surface having a second vertex line,

said convex second surface forming a second planar ring surface proximate to the second vertex line,

said substrate further having a connecting channel between the first central area and the second central area;

a first ceramic diaphragm

which rests on the first ling surface of the substrate, and

which is joined to the substrate on the first ring surface and between the cylindrical surface and the first ring surface by means of active brazing solder located in a first circumferential wedge zone, to form a first high-vacuum-tight sensing chamber, the circumferential wedge zone being configured to inhibit the active brazing solder from entering the concave central area,

with a third electrode being provided on a planar inner surface of the first diaphragm facing the substrate,

to which third electrode contact is made through the first wedge zone; and

a second ceramic diaphragm

which rests on the second ring surface of the substrate, and

which is joined to the substrate on the second ring surface and between the cylindrical surface and the second ring surface by means of active brazing solder forming a second high-vacuum-tight sensing chamber,

with a fourth electrode being provided on a planar inner surface of the second diaphragm facing the substrate,

to which fourth electrode contact is made through the second wedge zone.

5. The differential pressure sensor cell as claimed in claim 4 wherein the substrate and the diaphragms are made of alumina ceramic, and the active brazing solder is a Zr—

Fe—

Ti—

Be alloy or a Zr—

Ni—

Ti alloy.

6. The differential pressure sensor cell as claimed in claim 4 wherein at least the electrodes of the diaphragms are covered, at least in a respective edge region, with a solder resist layer.

7. A capacitive differential pressure sensor cell comprising;

a first ceramic substrate having

first cylindrical surface and,

at a first major surface, a concave first central area which

is provided with a first electrode,

has an electrical connection from the first electrode through the first ceramic substrate to a second major surface opposite the first major surface, and

as the concave first central area extends toward the cylindrical surface, merges into a convex first surface having a first vertex line,

said convex first surface forming a first planar ring surface proximate to the first vertex line;

a second ceramic substrate having

second cylindrical surface and,

at a first major surface, a concave second central area which

is provided with a second electrode,

has a second electrical connection from the second electrode through the second ceramic substrate to a second major surface opposite the first major surface, and,

as the concave second central area extends toward the second cylindrical surface, merges into a convex second surface having a second vertex line,

said convex second surface forming a second planar ring surface proximate to the second vertex line; and

a ceramic diaphragm which

rests with a first surface on the first ring surface of the first substrate,

is joined to the first substrate on the first ring surface and between the first cylindrical surface and the first ring surface of the first substrate by means of active brazing solder located in a first circumferential wedge zone, to form a first high-vacuum-tight sensing chamber, the first circumferential wedge zone being configured to inhibit the active brazing solder from entering the concave first central area,

rests with a second surface on the second ring surface of the second substrate,

is joined to the second substrate on the second ring surface and between the second cylindrical surface and the second ring surface of the second substrate by means of active brazing solder located in a second circumferential wedge zone, to form a second high-vacuum-tight sensing chamber, the circumferential wedge zone being configured to inhibit the active brazing solder from entering the concave second central area,

the first surface of the diaphragm being provided with a third electrode

to which contact is made through the first wedge zone, and

the second surface being provided with a fourth electrode

to which contact is made through the second wedge zone.

8. The differential pressure sensor cell as claimed in claim 7 wherein the substrates and the diaphragm are made of alumina ceramic, and the active brazing solder is a Zr—

Fe—

Ti—

Be alloy or a Zr—

Ni—

Ti alloy.

9. The differential pressure sensor cell as claimed in claim 7 at least the electrodes of the diaphragm are covered, at least in a respective edge region, with a solder resist layer.

10. A method for manufacturing a capacitive pressure sensor cell comprising the steps of:

providing a ceramic substrate having

a cylindrical surface,

a first major surface and

a second major surface,

said second major surface being opposite said first major surface,

said first major surface including a concave central area which, as the concave central area extends toward said cylindrical surface, merges into a convex surface having a vertex line,

said convex surface being formed into a planar ring surface proximate to said vertex line;

depositing a first electrode on said concave central area;

forming an electrical connection from said first electrode through said substrate to said second major surface;

providing a ceramic diaphragm having a planar inner surface;

depositing a second electrode on the central portion of said planar inner surface of said diaphragm such that, when said diaphragm is placed on said substrate, said second electrode extends up to said planar ring surface of said substrate;

applying an active brazing solder to said convex portion of said substrate between said cylindrical surface and said planar ring surface which convex portion is configured to inhibit the active brazing solder from entering the concave central area;

placing said diaphragm on said planar ring surface of said substrate such that said second electrode of said diaphragm extends up to said planar ring surface, and said second electrode faces said first electrode;

heating said substrate and said diaphragm in a vacuum or inert-gas atmosphere until the active brazing solder has melted; and

allowing said substrate and said diaphragm to cool down.

11. The method as claimed in claim 10 wherein at least the electrode of the diaphragm is covered, at least in a respective edge region, with a solder resist layer.

12. A method for manufacturing a capacitive differential pressure sensor cell comprising the steps of;

providing a ceramic substrate, at the first major surface thereof, with a concave first central area

which, as the concave first central area extends toward a cylindrical surface, merges into a convex first surface having a first vertex line,

said convex first surface being formed as a first planar ring surface in the area of the first vertex line;

depositing a first electrode on the first central area and providing an electrical connection from the first electrode through the substrate to the cylindrical surface of the substrate;

providing the substrate, at a second major surface opposite the first major surface, with a concave second central area

which, as the concave second central area extends toward the cylindrical surface of the substrate, merges into a convex second surface having a second vertex line,

said convex second surface being formed as a second planar ring surface proximate to the second vertex line;

depositing a second electrode on the second central area and providing an electrical connection from the second electrode through the substrate to the cylindrical surface of the substrate;

providing a first ceramic diaphragm congruent with the first major surface of the substrate, on a planar inner surface thereof, with a third electrode dimensioned so

that, after the first diaphragm has been placed on the first ring surface of the substrate, the third electrode extends up to said first ring surface;

providing a second ceramic diaphragm congruent with the second major surface of the substrate, on a planar inner surface thereof, with a fourth electrode dimensioned so

that, after the second diaphragm has been placed on the second ring surface of the substrate, said fourth electrode extends up to said second ring surface;

applying respective quantities of active brazing solder sufficient to braze the first and second diaphragms to the substrate to portions of the convex first surface of the substrate located between the first ring surface and the cylindrical surface and to portions of the convex second surface of the substrate located between the second ring surface and the cylindrical surface to inhibit the active brazing solder from entering the concave first central area and the concave second central area;

placing the surface of the first diaphragm provided with the third electrode on the first ring surface of the substrate;

placing the surface of the second diaphragm provided with the fourth electrode on the second ring surface of the substrate; and

heating the substrate and the diaphragm in a vacuum or inert-gas atmosphere until the active brazing solder has melted, and then allowing them to cool down.

13. The method as claimed in claim 12 wherein at least the electrodes of the diaphragms are covered, at least in a respective edge region, with a solder resist layer.

14. A method for manufacturing a capacitive differential pressure sensor cell comprising the steps of:

providing a first ceramic substrate, at a first major surface thereof, with a concave first central area

which, as the concave first central area extends toward a first cylindrical surface, merges into a convex first surface having a first vertex line, said convex first surface being formed as a first planar ring surface proximate to the first vertex line;

depositing a first electrode on the first central area and providing an electrical connection from the first electrode through the first substrate to a second major surface of the substrate opposite the first major surface;

providing a second ceramic substrate, at a first major surface thereof, with a concave second central area

which, as the concave second central area extends toward the second cylindrical surface of the second substrate, merges into a convex second surface having a second vertex line,

said convex second surface being formed as a second planar ring surface proximate to the second vertex line;

depositing a second electrode on the second central area and providing an electrical connection from the second electrode through the second substrate to a second major surface of the second substrate opposite the first major surface;

providing a ceramic diaphragm congruent with the first major surface of the first substrate, on a planar first surface thereof, with a third electrode dimensioned so

that, after the diaphragm has been placed on the first ring surface of the first substrate, said third electrode extends up to said first ring surface;

providing a planar second surface of the diaphragm opposite the first surface with a fourth electrode dimensioned so

that, after the diaphragm has been placed on the second ring surface of the second substrate, said fourth electrode extends up to said second ring surface;

applying respective quantities of active brazing solder sufficient to braze the first and second diaphragms to the substrate to portions of the convex first surface of the substrate located between the first ring surface and the cylindrical surface and to portions of the convex second surface of the substrate located between the second ring surface and the cylindrical surface to inhibit the active brazing solder from entering the concave first central area and the concave second central area;

placing the first surface of the diaphragm, provided with the third electrode, on the first ring surface of the substrate;

placing the second surface of the diaphragm, provided with the fourth electrode, on the second ring surface of the substrate; and

heating the substrate and diaphragm in a vacuum or inert-gas atmosphere until the active brazing solder has melted, and then allowing them to cool down.

15. The method as claimed in claim 14 wherein at least the electrodes of the diaphragm are covered, at least in a respective edge region, with a solder resist layer.

16. A pressure sensor apparatus, comprising:

a substrate having a generally concave surface configured to define a sensing chamber in the substrate, a mounting surface surrounding the sensing chamber, and a sealing surface located outside the sensing chamber and configured to extend away from the mounting surface in the same direction as the generally concave surface;

a first electrode located in the sensing chamber;

a first electrical connection coupled to the first electrode;

a diaphragm having an inner surface abutting the mounting surface of the substrate and extending over the sensing chamber, the diaphragm including a second electrode located adjacent the first electrode;

a second electrical connection coupled to the second electrode; and

a sealing material located outside of the sensing chamber between the sealing surface of the substrate and the diaphragm to couple the diaphragm to the substrate, whereby the sealing material is inhibited from entering the sensing chamber.

17. The apparatus of claim 16, wherein the sealing material includes an active brazing solder.

18. The apparatus of claim 17, wherein the substrate and the diaphragm include alumina ceramic and the active brazing solder includes at least one of a Zr—

Fe—

Ti—

Be alloy and a Zr—

Ni—

Ti alloy.

19. The apparatus of claim 18, wherein the second electrode is covered, at least in part, by a solder resistant layer.

20. The apparatus of claim 16, wherein the substrate includes a convex surface having a first convex portion located adjacent the concave surface defining the sensing chamber and a second convex portion located outside the sensing chamber, the second convex portion being configured to form the sealing surface, and the mounting surface of the substrate being located between the first and second convex portions.

21. The apparatus of claim 20, wherein the sealing material includes an active brazing solder.

22. The apparatus of claim 21, wherein the substrate and the diaphragm include alumina ceramic and the active brazing solder includes at least one of a Zr—

Fe—

Ti—

Be alloy and a Zr—

Ni—

Ti alloy.

23. The apparatus of claim 22, wherein the second electrode is covered, at least in part, by a solder resistant layer.