Fluororesin thin film diaphragm pressure sensor and method of fabricating the same

Abstract

A method of manufacturing a highly corrosion-resistant diaphragm pressure sensor capable of obviating the effects of temperature drift that arises when a pressure-travel coefficient changes with temperature of a fluid whose pressure is sensed. The diaphragm pressure sensor includes a pressure sensing element ( 10, 20 ) having a pressure receiving part with a deposition electrode formed on each of the opposing faces of sapphire or alumina ceramic diaphragms which are arranged in opposing relation, and a welding portion ( 10 A, 20 A) on a part of each of the surfaces of the diaphragms; and a fluororesin base ( 41, 61 ) for securing the pressure sensing element at the welding portion of the pressure sensing element. The pressure sensing element is coated with a fluororesin thin film having a cross-linked structure, and the pressure sensing element and the fluororesin base are welded together via the fluororesin thin film having a cross-linked structure.

1 . A method of fabricating a fluororesin thin film diaphragm pressure sensor for sensing a pressure of a fluid, comprising the steps of: 
 forming a pressure-sensing element having a pressure-receiving part with a deposition electrode formed on each of the opposing surfaces of sapphire or alumina ceramic diaphragms which are provided in opposing relation to each other, and a welding portion constituting a portion of the surface of each of the diaphragms;    forming a fluororesin thin film on said pressure-sensing element;    holding the fluororesin thin film formed on said pressure-sensing element at high temperatures and applying electron beam to the fluororesin thin film to thereby change the molecular structures of fluororesin of the fluororesin thin film to a crosslinked structure;    preparing a fluororesin base for securing said pressure-sensing element; and    securing said pressure-sensing element to said fluororesin base at the welding portion of said pressure-sensing element via said fluororesin thin film having a crosslinked structure formed on said pressure-sensing element.    
   
   
       2 . The method of fabricating a fluororesin thin film diaphragm pressure sensor as defined in  claim 1 , wherein said step of changing the molecular structures of fluororesin of the fluororesin thin film to a crosslinked structure further comprises a step of filling a closed vessel with an inactive gas such as an argon gas, nitrogen gas or the like, maintaining said fluororesin thin film at temperatures of 330° C.˜390° C. and heating the film until distribution of temperature becomes uniform throughout the film.  
   
   
       3 . The method of fabricating a fluororesin thin film diaphragm pressure sensor as defined in  claim 1 , wherein said step of forming a fluororesin thin film on said pressure-sensing element further comprises the steps of: 
 immersing said pressure-sensing element in a fluororesin solution to thereby coat said pressure-sensing element with a fluororesin thin film;    making uniform the fluororesin thin film formed on said pressure-sensing element; and    repeating said step of coating and said step of making the film uniform in order to attain a desired thickness of said fluororesin thin film.    
   
   
       4 . The method of fabricating a fluororesin thin film diaphragm pressure sensor as defined in  claim 1 , wherein said step of securing said pressure-sensing element to said fluororesin base comprises a step of securing said pressure-sensing element to said fluororesin base by using a fluororesin welding agent by means of high temperature welding.  
   
   
       5 . The method of fabricating a fluororesin thin film diaphragm pressure sensor as defined in  claim 1 , wherein said pressure-sensing element is formed as a strip-shaped element.  
   
   
       6 . The method of fabricating a fluororesin thin film diaphragm pressure sensor as defined in  claim 1 , wherein said pressure-sensing element is formed as a flat plate element.  
   
   
       7 . The method of fabricating a fluororesin thin film diaphragm pressure sensor as defined in  claim 1  further comprising a step of forming a fluororesin outer cylinder for guiding a fluid whose pressure is to be measured to the pressure-receiving part of said pressure-sensing element.