Ph sensor and manufacturing method

Abstract

Disclosed is a pH sensor comprising a carrier ( 10 ) comprising a plurality of conductive tracks and an exposed conductive area ( 40 ) defining a reference electrode connected to one of said conductive tracks; a sensing device ( 30 ) mounted on the carrier and connected at least one other of said conductive tracks; an encapsulation ( 20 ) covering the carrier, said encapsulation comprising a first cavity ( 22 ) exposing a surface ( 32 ) of the sensing device and a second cavity ( 24 ) exposing the exposed conductive area, said second cavity comprising a reference electrode material ( 42 ) and an ion reservoir material ( 44 ) sharing at least one ion type with said reference electrode material, the reference electrode material being sandwiched between the exposed conductive area and the ion reservoir material. A method of manufacturing such a pH sensor is also disclosed.

1 . A pH sensor comprising:
 a carrier ( 10 ) comprising a plurality of conductive tracks and an exposed conductive area ( 40 ) defining a reference electrode connected to one of said conductive tracks;   a sensing device ( 30 ) mounted on the carrier and connected at least one other of said conductive tracks;   an encapsulation ( 20 ) covering the carrier, said encapsulation comprising a first cavity ( 22 ) exposing a surface ( 32 ) of the sensing device and a second cavity ( 24 ) exposing the exposed conductive area, said second cavity comprising a reference electrode material ( 42 ) and an ion reservoir material ( 44 ) sharing at least one ion type with said reference electrode material, the reference electrode material being sandwiched between the exposed conductive area and the ion reservoir material.   
     
     
         2 . The pH sensor of  claim 1 , further comprising a layer ( 46 ,  48 ) impermeable to the ion type in the ion reservoir material ( 44 ) over the second cavity. 
     
     
         3 . The pH sensor of  claim 1 , further comprising:
 a first contact pad ( 16 ) connected to the sensing device ( 30 ) via one of said other of said conductive tracks ( 12 ); and   a second contact pad connected to the exposed conductive area ( 40 ) via said one of said conductive tracks.   
     
     
         4 . The pH sensor of  claim 1 , wherein the sensing device ( 30 ) comprises a transceiver, the pH sensor further comprising an antenna ( 50 ) on the carrier ( 10 ) connected to the at least one other of said conductive tracks ( 12 ). 
     
     
         5 . The pH sensor of  claim 4 , wherein the exposed conductive area ( 40 ) is connected to the sensing device ( 30 ) via said one of said conductive tracks ( 12 ′). 
     
     
         6 . The pH sensor of  claim 1 , wherein said encapsulation ( 20 ) further comprises a fluid channel ( 26 ) laterally extending from an edge of said encapsulation to the second cavity ( 24 ). 
     
     
         7 . The pH sensor of  claim 6 , wherein said encapsulation ( 20 ) further comprises a further fluid channel ( 28 ) laterally extending from said edge to the first cavity ( 22 ). 
     
     
         8 . The pH sensor of  claim 1 , wherein the carrier ( 10 ) is a printed circuit board. 
     
     
         9 . The pH sensor of  claim 1 , wherein the sensing device ( 30 ) comprises an ion sensitive field effect transistor having its gate ( 32 ) exposed in the first cavity ( 22 ). 
     
     
         10 . The pH sensor of  claim 1 , further comprising a sharp tip ( 21 ) for inserting the pH sensor into a substance. 
     
     
         11 . The pH sensor of  claim 1 , wherein the exposed conductive area ( 40 ) comprises a gold-plated copper layer. 
     
     
         12 . The pH sensor of  claim 1 , wherein the reference electrode material comprises Ag and AgCl and the ion reservoir material comprises chloride ions. 
     
     
         13 . The pH sensor of  claim 12 , further comprising an ion-selective membrane ( 46 ,  48 ) impermeable to the ion type in the ion reservoir material ( 44 ) over the second cavity. 
     
     
         14 . A method of manufacturing a pH sensor according to  claim 1 , comprising:
 providing a carrier having on its surface a plurality of conductive tracks, an exposed conductive area connected to one of said conductive tracks and a further exposed conductive area   fixating an integrated circuit die to the further exposed conductive area, said integrated circuit die comprising an exposed pH-sensitive surface;   encapsulating the resultant structure in a protective resin;   forming first and second cavities in said protective resin, the first cavity exposing the pH-sensitive surface and the second cavity exposing the exposed conductive area;   depositing a reference electrode material over the exposed conductive area; and   depositing an ion reservoir material ( 44 ) sharing at least one ion type with said reference electrode material over said reference electrode material.   
     
     
         15 . The method of  claim 14 , wherein said encapsulating step and said cavities forming step are performed simultaneously.