The present invention relates to at least one hermetic electrical feedthrough in a substrate piece and a method for implementing it, said piece (P) comprising at least two substrate layers (10, 11) and a conductor layer (12), a component (13) fitted inside said piece and a conductor (1), the conductor (1) extending from the outer surface of said piece to the component for providing an electrical connection, and wherein the feedthrough is fitted between said substrate layers. The invention also relates to a method for implementing the hermetic electrical feedthrough in the substrate piece. The substrate layers (10, 11) and the conductor layer (12) are pressed together and joined with each other by means of at least one weld (3) formed between the component (13) and the periphery (21) of the substrate piece, wherein the at least one weld (3) is made with a focused laser beam, and wherein the at least one weld (3) encircles the component (13) at the height level of a common interface area (25) of said substrate layers and the conductor layer, each weld extends substantially from a first edge (1.1) of a conductor (1) to its second edge or to a second edge (1.2) of another conductor adjacent to it, wherein the opposite surfaces of the substrate layers (10, 11) facing the conductor (1) constrict against the conductor (1) due to thermal tensions caused by welding heat, wherein joints between the conductor (1) and said surfaces become hermetic.
