Method for producing a pressure sensor for detecting small pressure differences and low pressures

• US 20050262946A1
• Filed: 12/15/2004
• Published: 12/01/2005
• Est. Priority Date: 12/22/1997
• Status: Active Grant

• Current Assignee: MKS Instruments Incorporated
• Original Assignee: MKS Instruments Incorporated
• Inventors: Jonsson, Staffan
• Granted Patent: US 7,284,439 B2
• Time in Patent Office: Days
• US Class Current: 73/723
• CPC Class Codes: G01L 13/025 using diaphragms
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass

Abstract

A process for producing a plate for a capacitive sensor element. In one embodiment of the present invention, a method includes forming a plate from a substantially pure aluminum oxide slurry, heating the plate a first time in an oven to sinter the plate, cooling the plate after the heating step, heating the plate a second time to smooth the plate, and cooling the plate after the second heating.

Claims

1. A process for producing a plate for a capacitive sensor element that comprises the following steps:

a. forming a plate from a substantially pure aluminum oxide slurry;

b. heating the plate a first time in an oven to sinter the plate;

c. cooling the plate following step b;

d. heating the plate a second time to smooth the plate; and

e. cooling the plate following step d.

2. A process according to claim 1 including the step of heating the plate a third time following step e for smoothing the plate.

3. A process according to claim 1 wherein the plate has a sintering temperature, and wherein the step of heating the plate a second time to smooth the plate is performed at a temperature that is sufficiently high to soften the plate but which does not exceed the sintering temperature.

4. A process according to claim 1 in which the plate rests between a first block and a second block during the second heating step, and is smoothed by pressing such as by weight loading.

5. A process according to claim 4 in which the plate is detached from the first and second blocks after the second heating step, redeposited in an offset position upon at least one of the first and second blocks, and subsequently heated a third time following step e for smoothing the plate.

6. A process according to claim 4 in which the first and second blocks comprise polished aluminum oxide.

7. A process according to claim 1 in which the plate shape is cast or pressed from the aluminum oxide slurry, from a thin strip of an aluminum oxide green body supported on a substrate, and which is subsequently pulled off the substrate.

8. The process recited by claim 1 including the further step of bonding the plate in the capacitive sensor element to enclose a reference vacuum.

9. A process according to claim 4 in which the plate is detached from the first and second blocks after the second heating step, redeposited in an upside down position upon one of the first and second blocks, and subsequently heated a third time following step e for smoothing the plate.

10. A process for producing a membrane for a capacitive vacuum measuring cell that comprises the following steps:

a. forming a membrane from a substantially pure Al₂O₃ slurry;

b. heating the membrane a first time in a furnace to sinter the membrane;

c. cooling the membrane following step b;

d. heating the membrane a second time to smooth the membrane; and

e. cooling the membrane following step d.

11. A process according to claim 10 including the step of heating the membrane a third time following step e. for smoothing the membrane.

12. A process according to claim 10 wherein the membrane has a sintering temperature, and wherein the step of heating the membrane a second time to smooth the membrane is performed at a temperature that is sufficiently high to soften the membrane but which does not exceed the sintering temperature.

13. A process according to claim 10 in which the membrane rests on a flat plate during the second heating step, and is smoothed.

14. A process according to claim 13 in which the membrane is detached from the flat plate after the second heating step, redeposited in an offset position upon said flat plate, and subsequently heated a third time following step e for smoothing the membrane.

15. A process according to claim 13 in which the flat plate is made of a material that has essentially the same temperature coefficient as the membrane material, and consists of Al₂O₃.

16. A process according to claim 10 in which the membrane shape is cast or pressed from the Al₂O₃ slurry.

17. The process recited by claim 10 including the further step of bonding the membrane in a capacitive vacuum measuring cell to enclose a reference vacuum.