Abstract: A semi-conductor element module having a housing contains at least one semi-conductor junction having electrodes electrically connected to respective terminals by compression assembly, the semi-conductor junction and terminals forming elements of a stack contained in the housing and further comprising at least one strain buffer, at least one electrical isolation member, and at least one electrically insulating compression member. Compression forces are applied to the stack by at least one spring means, the height of said stack being less than 15 mm and the module being such that, in use with rated current, the junction temperature is no greater than 130.degree. C. and the housing temperature is no less than 80.degree. C. Furthermore the module has at least two external terminals, the distance between which is adjustable.