Hermetic feedthrough assembly and associated methods

Abstract

A feedthrough assembly for an implantable medical device includes a ferrule, an inner conductor, and an insulating core. The ferrule has a lumen. The inner conductor extends through the lumen of the ferrule. The inner conductor has a first material composition. The insulating core is disposed within the lumen of the ferrule and separates the inner conductor from the ferrule. The insulating core has a second material composition that is different from the first material composition of the inner conductor. A coefficient of thermal expansion (CTE) of the inner conductor is no less than the CTE of the insulating core. The inner conductor is bonded to the insulating core to form a glass-to-metal seal between the inner conductor and the insulating core.

What is claimed is: 
     
         1 . A feedthrough assembly for an implantable medical device, the feedthrough assembly comprising:
 a ferrule having a lumen;   an inner conductor extending through the lumen of the ferrule, the inner conductor having a first material composition; and   an insulating core disposed within the lumen of the ferrule and separating the inner conductor from the ferrule, the insulating core having a second material composition that is different from the first material composition of the inner conductor,   wherein a coefficient of thermal expansion (CTE) of the inner conductor is no less than the CTE of the insulating core, and   wherein the inner conductor is bonded to the insulating core to form a glass-to-metal seal between the inner conductor and the insulating core.   
     
     
         2 . The feedthrough assembly of  claim 1 , further comprising a case having a feedthrough port and containing a battery within the case, wherein the ferrule is disposed in the feedthrough port of the case and the inner conductor is electrically connected to the battery within the case. 
     
     
         3 . The feedthrough assembly of  claim 1 , wherein the second material composition of the insulating core comprises a glass. 
     
     
         4 . The feedthrough assembly of  claim 1 , wherein the first material composition of the inner conductor comprises one or both of titanium or niobium. 
     
     
         5 . The feedthrough assembly of  claim 1 , wherein the CTE of the inner conductor is greater than the CTE of the insulating core. 
     
     
         6 . The feedthrough assembly of  claim 1 , wherein the glass-to-metal seal between the inner conductor and the insulating core is a hermetic seal. 
     
     
         7 . The feedthrough assembly of  claim 1 , wherein the ferrule has a third material composition, and the CTE of the ferrule is greater than the CTE of the insulating core. 
     
     
         8 . The feedthrough assembly of  claim 1 , wherein the first material composition of the inner conductor comprises titanium, and the second material composition of the insulating core comprises calcium-boro-aluminate-12 (CABAL-12) glass. 
     
     
         9 . The feedthrough assembly of  claim 1 , wherein the lumen of the ferrule is a first lumen, the inner conductor is a first inner conductor, and the insulating core is a first insulating core, wherein the ferrule defines a second lumen spaced apart from the first lumen, and the feedthrough assembly further comprises a second inner conductor and a second insulating core, the second inner conductor extending through the second lumen, the second insulating core disposed within the second lumen and separating the second inner conductor from the ferrule. 
     
     
         10 . The feedthrough assembly of  claim 9 , wherein the first inner conductor is electrically connected to a cathode assembly of a battery cell stack and the second inner conductor is electrically connected to an anode assembly of the battery cell stack. 
     
     
         11 . A method for forming an implantable medical device, the method comprising:
 forming a feedthrough assembly by:
 inserting an inner conductor to extend through a lumen of a ferrule, the inner conductor having a first material composition; 
 positioning an insulating core within the lumen of the ferrule such that the insulating core separates the inner conductor from the ferrule, the insulating core having a second material composition that is different from the first material composition of the inner conductor, wherein a coefficient of thermal expansion (CTE) of the insulating core is no greater than the CTE of the inner conductor; and 
 bonding the inner conductor to the insulating core to form a glass-to-metal seal between the inner conductor and the insulating core; and 
   inserting the feedthrough assembly into a feedthrough port of a case.   
     
     
         12 . The method of  claim 11 , wherein bonding the inner conductor to the insulating core comprises:
 heating the ferrule, the insulating core, and the inner conductor to a temperature sufficient to cause the insulating core to melt and flow into contact with an outer surface of the inner conductor and an inner surface of the ferrule along the lumen; and   thereafter cooling the ferrule, the insulating core, and the inner conductor to re-solidify the insulating core.   
     
     
         13 . The method of  claim 11 , further comprising:
 loading a battery into the case; and   electrically connecting the inner conductor to the battery within the case.   
     
     
         14 . The method of  claim 11 , wherein the first material composition of the inner conductor comprises one or both of titanium or niobium, and the second material composition of the insulating core comprises a glass. 
     
     
         15 . The method of  claim 11 , wherein the CTE of the inner conductor is greater than the CTE of the insulating core. 
     
     
         16 . The method of  claim 11 , wherein the first material composition of the inner conductor comprises titanium, and the second material composition of the insulating core comprises calcium-boro-aluminate-12 (CABAL-12) glass. 
     
     
         17 . The method of  claim 11 , wherein the lumen of the ferrule is a first lumen, the inner conductor is a first inner conductor, and the insulating core is a first insulating core, wherein the ferrule defines a second lumen spaced apart from the first lumen, and forming the feedthrough assembly further comprises:
 inserting a second inner conductor to extend through the second lumen of the ferrule, the inner conductor having the first material composition;   positioning a second insulating core within the second lumen of the ferrule such that the second insulating core separates the second inner conductor from the ferrule, the second insulating core having the second material composition; and   bonding the second inner conductor to the second insulating core to form a glass-to-metal seal between the second inner conductor and the second insulating core.   
     
     
         18 . An implantable medical device comprising:
 a case including a feedthrough port;   a battery disposed within the case; and   a feedthrough assembly disposed in the feedthrough port of the case, the feedthrough assembly comprising:
 a ferrule having a lumen; 
 an inner conductor extending through the lumen of the ferrule, the inner conductor having a first material composition, the inner conductor electrically connected to the battery; and 
 an insulating core disposed within the lumen of the ferrule and separating the inner conductor from the ferrule, the insulating core having a second material composition that is different from the first material composition of the inner conductor, 
   wherein a coefficient of thermal expansion (CTE) of the inner conductor is no less than the CTE of the insulating core, and   wherein the inner conductor is bonded to the insulating core to form a glass-to-metal seal between the inner conductor and the insulating core.   
     
     
         19 . The implantable medical device of  claim 18 , wherein the first material composition of the inner conductor comprises one or both of titanium or niobium, and the second material composition of the insulating core comprises a glass. 
     
     
         20 . The implantable medical device of  claim 18 , further comprising:
 a memory disposed within the case, the memory configured to store program instructions; and   one or more processors disposed within the case and configured to execute the program instructions in connection with at least one of monitoring a biological signal or administering a therapy.