Directly integrated feedthrough for an implantable medical device housing using a gold alloy

Abstract

One aspect provides an implantable medical device with a titanium housing having a flange defining a recess about an opening through the housing. The opening is disposed within the recess. A feedthrough is disposed within the recess with a gap between an insulator of the feedthrough and the flange. A braze joint is between the insulator and the flange that occupies the gap and hermetically seals the insulator to the housing. The braze joint includes a biocompatible gold alloy having a melting point less than the β-transus temperature of the titanium of the housing.

What is claimed is: 
     
         1 . An implantable medical device comprising:
 a titanium housing with a flange defining a recess about an opening through the housing, the opening disposed within the recess;   a feedthrough disposed within the recess with a gap between an insulator of the feedthrough and the flange; and   a braze joint between the insulator and the flange that occupies the gap and hermetically seals the insulator to the housing, the braze joint comprising a biocompatible gold alloy having a melting point less than the β-transus temperature of the titanium of the housing;   wherein the gap has a distance in the range of 10-50 μm in order to optimize capillary action of the biocompatible gold alloy of the braze joint.   
     
     
         2 . The implantable medical device of  claim 1 , wherein a surface of the insulator to which the braze joint is bonded includes a metalized layer. 
     
     
         3 . The implantable medical device of  claim 1  characterized in that insulator of the feedthrough is coupled directly to the housing without an intervening ferrule or other structure. 
     
     
         4 . The implantable medical device of  claim 1 , wherein the gold alloy consists of gold and germanium. 
     
     
         5 . The implantable medical device of  claim 1 , wherein the gold alloy consists of gold and indium. 
     
     
         6 . The implantable medical device of  claim 1 , wherein the gold alloy consists of gold, silver, platinum, copper, and zinc. 
     
     
         7 . The implantable medical device of  claim 1 , wherein the melting point of the gold alloy does not exceed 870° C. 
     
     
         8 . The implantable medical device of  claim 1 , wherein the melting point of the gold alloy does not exceed 710° C. 
     
     
         9 . The implantable medical device of  claim 1 , wherein the melting point of the gold alloy does not exceed 487° C. 
     
     
         10 . The implantable medical device of  claim 1 , wherein the melting point of the gold alloy does not exceed 361° C. 
     
     
         11 . The implantable medical device of  claim 1 , wherein the titanium of the housing within 0.25 inches of the opening has a grain size not exceeding 100 μm. 
     
     
         12 . An implantable medical device comprising:
 a titanium housing with a flange defining a recess about an opening through the housing, the opening disposed within the recess;   a feedthrough disposed within the recess with a gap between an insulator of the feedthrough and the flange; and   a braze joint between the insulator and the flange that occupies the gap and hermetically seals the insulator to the housing, the braze joint comprising a biocompatible gold alloy having a melting point less than the β-transus temperature of the titanium of the housing.   
     
     
         13 . The implantable medical device of  claim 12 , wherein the gap has a distance in the range of 10-50 μm in order to optimize capillary action of the braze. 
     
     
         14 . The implantable medical device of  claim 12 , wherein a surface of the insulator to which the braze joint is bonded includes a metalized layer. 
     
     
         15 . The implantable medical device of  claim 12 , wherein the gold alloy consists of gold and germanium. 
     
     
         16 . The implantable medical device of  claim 12 , wherein the gold alloy consists of gold and indium. 
     
     
         17 . The implantable medical device of  claim 12 , wherein the gold alloy consists of gold, silver, platinum, copper, and zinc. 
     
     
         18 . The implantable medical device of  claim 12 , wherein the melting point of the gold alloy does not exceed 870° C. 
     
     
         19 . The implantable medical device of  claim 12 , wherein the melting point of the gold alloy does not exceed 361° C. 
     
     
         20 . The implantable medical device of  claim 12 , wherein the titanium of the housing within 0.25 inches of the opening has a grain size not exceeding 100 μm.