Membrane for capacitive vacuum measuring cell

• US 20030118802A1
• Filed: 02/07/2003
• Published: 06/26/2003
• Est. Priority Date: 12/23/1997
• Status: Active Grant

• Current Assignee: INFICON GmbH (Inficon Holding AG)
• Original Assignee: INFICON GmbH (Inficon Holding AG)
• Inventors: Bjoerkman, Per
• Granted Patent: US 7,107,855 B2
• Time in Patent Office: Days
• US Class Current: 428/220
• 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

A ceramic membrane for a capacitive vacuum measuring cell includes a thin ceramic membrane with a thickness of <250 μm, in particular less than 120 μm. The membrane is produced from a ribbon-shaped green body of Al₂O₃, and is given high planarity by smoothing the membrane after sintering. The green body is sintered at a sintering temperature that is higher than the smoothing temperature applied following sintering.

Claims

1. A membrane for a capacitive vacuum measuring cell, said membrane being made of a membrane material consisting of Al₂O₃ and having a thickness within the range of 1 μ

m to 250 μ

m.

2. The membrane recited by claim 1 wherein said membrane has a thickness within the range of 10 μ

m to 120 μ

m.

3. A membrane according to claim 1 wherein the membrane material has a mean grain size of ≦

20 μ

m.

4. The membrane recited by claim 3 wherein the membrane material has a mean grain size of ≦

10 μ

m.

5. The membrane recited by claim 4 wherein the membrane material has a mean grain size of ≦

5 μ

m.

6. A membrane according to claim 1 wherein the membrane has a thickness cross-section, and wherein at least two grains of membrane material are present in the thickness cross-section of the membrane.

7. The membrane recited by claim 6 wherein at least five grains of membrane material are present in the thickness cross-section of the membrane.

8. A membrane according to claim 1 wherein the membrane has a surface, and wherein any unevenness of the membrane surface across the entire surface thereof is not greater than 10 μ

m

9. The membrane recited by claim 8 wherein any unevenness of the membrane surface across the entire surface thereof is not greater than 5 μ

m.

10. A membrane according to claim 1 in which the purity of the Al₂O₃ from which the membrane is made is at least 94%.

11. The membrane recited by claim 10 wherein the purity of the Al₂O₃ from which the membrane is made is at least 99%.

12. A membrane according to claim 1 wherein the membrane has a generally-circular shape characterized by a diameter, and wherein the diameter of the membrane is within the range of 5 to 80 mm.

13. The membrane recited by claim 12 wherein the diameter of the membrane is within the range of 5 to 40 mm.

14. A membrane according to claim 1 wherein said membrane has at least one generally planar surface, and in which said at least one surface includes an electrically conductive coating.

15. A membrane for a capacitive vacuum measuring cell, said membrane being produced by the process of:

a. forming the membrane from an Al₂O₃ slurry;

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

c. cooling the membrane following heating step b;

d. heating the membrane a second time in a furnace at a second temperature to smooth the membrane, the second temperature being lower than the first temperature; and

e. cooling the membrane following heating step d.