A method of making leak tight electrical connections through the wall of a ceramic package, for example a ceramic package used on an image intensifier tube. The method comprises a hole metallisation step (500) to obtain vias, the metallisation step comprising the deposition of a bond layer (510), a diffusion barrier (520) acting as a metallic base layer and a wetting agent (530). For each via, a filler metal preform made of indium or a eutectic chosen from among InSn, AuSn, AuGe, AgSn is deposited (540) on each orifice and is heated to a temperature higher than its melting temperature (550) such that the molten filler metal closes off the via to make it leak tight.