A feedthrough assembly , which comprises: a) an insulator of electrically non-conductive material having a height defined by an insulator sidewall extending to a first insulator end and a second insulator end , wherein the insulator has at least one terminal pin bore extending from the first end to the second end thereof; b) a terminal pin received in the terminal pin bore , the terminal pin having a sidewall extending to opposed first and second ends disposed spaced from the respective first and second insulator ends ; and c) a ferrule of an electrically conductive material and comprising a ferrule opening defined by a surrounding sidewall extending to a first ferrule end and a second ferrule end, wherein the insulator is supported in the ferrule opening, characterized by d) the terminal pin comprising a terminal pin core of a first electrically conductive material and an external outer coating of a second electrically conductive material selectively applied to and directly supported on discrete portions of the terminal pin core , wherein one discrete portion lies within a terminal pin proximal end portion , positioned between the first insulator end and the first terminal pin end, or within a terminal pin distal end portion , positioned between the second insulator end and the second end of the terminal pin , wherein the external outer coating comprises multiple compositions for multiple discrete portions, respectively; and e) a first braze material contacting the coating of the second electrically conductive material on the terminal pin core thereby hermetically sealing the terminal pin to the insulator and a second braze material hermetically sealing the insulator to the ferrule. a) an insulator of electrically non-conductive material having a height defined by an insulator sidewall extending to a first insulator end and a second insulator end , wherein the insulator has at least one terminal pin bore extending from the first end to the second end thereof; b) a terminal pin received in the terminal pin bore , the terminal pin having a sidewall extending to opposed first and second ends disposed spaced from the respective first and second insulator ends ; and c) a ferrule of an electrically conductive material and comprising a ferrule opening defined by a surrounding sidewall extending to a first ferrule end and a second ferrule end, wherein the insulator is supported in the ferrule opening, characterized by d) the terminal pin comprising a terminal pin core of a first electrically conductive material and an external outer coating of a second electrically conductive material selectively applied to and directly supported on discrete portions of the terminal pin core , wherein one discrete portion lies within a terminal pin proximal end portion , positioned between the first insulator end and the first terminal pin end, or within a terminal pin distal end portion , positioned between the second insulator end and the second end of the terminal pin , wherein the external outer coating comprises multiple compositions for multiple discrete portions, respectively; and e) a first braze material contacting the coating of the second electrically conductive material on the terminal pin core thereby hermetically sealing the terminal pin to the insulator and a second braze material hermetically sealing the insulator to the ferrule. <EOS>