DIELECTRIC SUBSTRATE

PURPOSE:To enhance bonding strength between a dielectric base material and an aluminum sheet by a method wherein a face facing at least the dielectric base material out of surfaces of the aluminum sheet is Alumite-treated. CONSTITUTION:Two dielectric base materials composed of a glass cloth 1 and cross-linked polyethylene layers 2 which have been impregnated into the cloth 1 and cover its surfaces are piled up; copper foil 4 and an aluminum sheet 5 are bonded to both faces of these piled-up base materials via cross-linked UHPE layers 3. An Alumite-treated layer 6 installed on the surface facing the dielectric base material at the aluminum sheet 5 and a cross-linked polyethylene sheet 7 used to reinforce a bonding force between the dielectric base materials are formed. The Alumite-treated layer 6 is used to enhance bonding strength between the aluminum sheet 5 and the dielectric base material, and its thickness is preferably less than 10mum.