A member for use in an electronic circuit has a thermally conductive layer mounted
on a heat sink. The thermally conductive layer comprises an insulating substrate,
a first joint member joining the insulating substrate to the heat sink and containing
an active element, a second joint member disposed on the insulating substrate,
and an electrode disposed on the second joint member. The insulating substrate
comprises an AlN layer or an Si3N4 layer. Each of the first
and second joint members is made of a hard brazing material containing an active
element. The heat sink is made of an SiC/Cu composite material or a C/Cu composite material.
