A feedthrough assembly, which comprises: a) an insulator of electrically non-conductive material having a height defined by an insulator sidewall extending to spaced apart first and second ends, 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, wherein the terminal pin comprises a first metal, which is a refractory metal; c) a ferrule of an electrically conductive material and comprising a ferrule opening defined by a surrounding sidewall extending to a ferrule first end and a ferrule second end, wherein the insulator is supported in the ferrule opening; d) a first braze material hermetically sealing the terminal pin to the insulator and a second braze material hermetically sealing the insulator to the ferrule; e) a protective cap, being composed of a polymeric material, having a height defined by a protective cap sidewall extending from a protective cap first end to a protective cap second end, wherein the terminal pin extends through a protective cap throughbore extending from the protective cap first end to the protective cap second end; and f) a terminal block, comprising a second metal, dissimilar to the first metal, positioned within a slot residing within a topside surface of the protective cap second end such that the terminal pin extends through the protective cap throughbore and a terminal block throughbore, wherein a laser weld having a curved shape joins a portion of the first end of the terminal pin to the terminal block, the laser weld formed at a top surface of the terminal block and first end of the terminal pin, and covers a full perimeter of the terminal pin. a) an insulator of electrically non-conductive material having a height defined by an insulator sidewall extending to spaced apart first and second ends, 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, wherein the terminal pin comprises a first metal, which is a refractory metal; c) a ferrule of an electrically conductive material and comprising a ferrule opening defined by a surrounding sidewall extending to a ferrule first end and a ferrule second end, wherein the insulator is supported in the ferrule opening; d) a first braze material hermetically sealing the terminal pin to the insulator and a second braze material hermetically sealing the insulator to the ferrule; e) a protective cap, being composed of a polymeric material, having a height defined by a protective cap sidewall extending from a protective cap first end to a protective cap second end, wherein the terminal pin extends through a protective cap throughbore extending from the protective cap first end to the protective cap second end; and f) a terminal block, comprising a second metal, dissimilar to the first metal, positioned within a slot residing within a topside surface of the protective cap second end such that the terminal pin extends through the protective cap throughbore and a terminal block throughbore, wherein a laser weld having a curved shape joins a portion of the first end of the terminal pin to the terminal block, the laser weld formed at a top surface of the terminal block and first end of the terminal pin, and covers a full perimeter of the terminal pin.