Electrical capacitance-type diaphragm pressure sensor and a method of fabricating the same

• US 6,860,155 B2
• Filed: 09/29/2003
• Issued: 03/01/2005
• Est. Priority Date: 12/04/2002
• Status: Expired due to Fees

• Current Assignee: Tem-Tech Lab., Co., Ltd.
• Original Assignee: Tem-Tech Lab., Co., Ltd.
• Inventors: Aizawa, Mitsuyoshi
• Primary Examiner(s): OEN, WILLIAM L
• Application Number:
  US10/671,624
• Publication Number:
  US 20040118211A1
• Time in Patent Office: 519 Days
• Field of Search: 29/254.1, 29/254.2, 737/18, 737/24, 737/06, 361/283.4
• US Class Current: 73/724
• CPC Class Codes: G01L 9/0072 using variations in capacitance

Abstract

A compact and highly accurate pressure sensor, and a method of fabricating the same are provided by improving functioning of a diaphragm which acts as a means for sensing a fluid pressure. An electrical capacitance-type diaphragm pressure sensor for sensing a fluid pressure is fabricated by providing non-metallic strip diaphragms in opposing relation to each other; forming deposited electrodes on the opposing surfaces of the diaphragms to form a pressure receiving part (10a) of a pressure-sensing member (10); depositing a metal on the diaphragms except for an end part of the pressure-sensing member where an electrode output terminal is formed; mounting a soluble flange along an approximate border between the end part and pressure receiving part of the pressure-sensing member; applying a nickel plating (22) as a protective layer to the pressure receiving part and the periphery of the flange; removing the flange except the nickel-plated protective layer; and mounting supporting members (31, 32) in the region where the flange was removed.

Claims

1. An electrical capacitance-type diaphragm pressure sensor comprising:

a pressure-sensing member having a pressure receiving part formed from non-metallic strip diaphragms provided in opposing relation to each other, with deposited electrodes being formed on the opposing surfaces of the diaphragms, and depositing a metal on the diaphragms; and

a nickel protective layer directly provided on said pressure-sensing member,

wherby a fluid pressure to be sensed is transferred to said pressure receiving part via said nickel protective layer and variations in an amount of a gap between the deposited electrodes formed on the opposing faces of the opposing diaphragms cause changes in capacitance.

2. The diaphragm pressure sensor as defined in claim 1, wherein said pressure-sensing member is provided with a supporting member for installation.

3. The diaphragm pressure sensor as defined in claim 1, wherein the metal deposited on said diaphragm is any metal having a high ionization tendency, and selected from tin, copper, silver and gold.

4. A method of fabricating an electrical capacitance-type diaphragm pressure sensor for sensing a fluid pressure comprising the steps of:

providing non-metallic strip diaphragms in opposing relation and forming deposited electrodes on the opposing faces of said diaphragms, to thereby form a pressure-receiving part of a pressure-sensing member;

depositing a metal on said diaphragms in said pressure-sensing member except for an end part where an electrode output terminal is formed;

installing a soluble flange along the approximate border between said end part and pressure receiving part of said pressure-sensing member;

applying a nickel plating as a protective layer to said pressure receiving part and the periphery of said flange of said pressure-sensing member;

removing said flange except for said nickel-plated protective layer in said pressure-sensing member; and

mounting a supporting member for installation in a region where said flange was removed except for said nickel-plated protective layer.

5. The method as defined in claim 4 further comprising, before the step of applying said nickel plating, the step of covering the end part of the pressure-sensing member where said electrode output terminal is formed with a protective coat, so that a nickel plating solution does not affect the end part.

6. The method as defined in claim 4 further comprising the step of immersing said nickel-plated protective layer in concentrated nitric acid, to thereby form over the nickel a passive state coat resistant to a strong acid solution.

7. The method as defined in claim 5 further comprising the step of immersing said nickel-plated protective layer in concentrated nitric acid, to thereby form over the nickel a passive state coat resistant to a strong acid solution.