Sealed capacitive sensor

Abstract

A sealed capacitive sensor includes a substrate having a diaphragm forming a first plate of a capacitor; a second fixed plate of the capacitor spaced from the diaphragm and defining a predetermined dielectric gap and a sealing medium connecting together the substrate and fixed plate in an integrated structure and hermetically sealing the gap.

1 . A sealed capacitive sensor comprising: 
 a substrate having a diaphragm forming a first plate of a capacitor;    a second fixed plate of the capacitor spaced from said diaphragm ad defining a dielectric gap; and    a sealing medium connecting together said substrate and fixed plate in an integral structure and hermetically sealing said gap.    
   
   
       2 . The sealed capacitive sensor of  claim 1  in which said substrate includes ceramic.  
   
   
       3 . The sealed capacitive sensor of  claim 1  in which said substrate includes silicon.  
   
   
       4 . The sealed capacitive sensor of  claim 1  in which said fixed plate includes silicon.  
   
   
       5 . The sealed capacitive sensor of  claim 1  in which said sealing medium includes a frit.  
   
   
       6 . The sealed capacitive sensor of  claim 5  in which said frit includes a glass frit.  
   
   
       7 . The sealed capacitive sensor of  claim 1  in which at least one of said first and fixed plates includes a metal layer  
   
   
       8 . The sealed capacitive sensor of  claim 1  in which at least one of said first and fixed plates includes silicon.  
   
   
       9 . The sealed capacitive sensor of  claim 8  in which each of said silicon plates is doped.  
   
   
       10 . The sealed capacitive sensor of  claim 1  in which said fixed plate bears an active electronic circuit associated with said capacitive sensor.  
   
   
       11 . The sealed capacitive sensor of  claim 1  in which said fixed plate bears on a separate chip, an active electronic circuit associated with said capacitive sensor.  
   
   
       12 . The sealed capacitive sensor of  claim 1   1  in which there is an insulation layer between said active electronic circuit and said fixed plate.  
   
   
       13 . The sealed capacitive sensor of  claim 1  in which said fixed plate includes a recess which defines at least a part of the gap dimension.  
   
   
       14 . The sealed capacitive sensor of  claim 1  in which the sealing medium defines at least a part of the gap dimension.  
   
   
       15 . The sealed capacitive sensor of  claim 1  in which said fixed plate is electrically accessed through a wire bonding lead.  
   
   
       16 . The sealed capacitive sensor of  claim 1  in which said first plate is electrically accessed through a conductor buried in the substrate traversing said sealing medium.  
   
   
       17 . The sealed capacitive sensor of  claim 1  in which said fixed plate includes a second recess for housing an active electric circuit associated with said capacitive sensor.  
   
   
       18 . The sealed capacitive sensor of  claim 17  further including a cover and second sealing medium for connecting said cover to said fixed plate and hermetically sealing said second recess.  
   
   
       19 . The sealed capacitive sensor of  claim 18  in which said second sealing medium includes a frit.  
   
   
       20 . The sealed capacitive sensor of  claim 18  in which said second sealing medium includes a glass frit.  
   
   
       21 . The sealed capacitive sensor of  claim 1  further including an over mold covering said fixed plate and attached to said substrate.