JPS6473695A - Substrate for printed-circuit board - Google Patents

Abstract

PURPOSE:To satisfy a high-frequency characteristic and to enhance usability to a surface-mounting operation by a method wherein at least one face of a metal sheet whose coefficient of linear expansion is 6X10<-6>mm/mm deg.C or less is covered with an insulating layer composed of an aramid fiber cloth with a specified thickness range which has been impregnated with a specified weight % range of a heat-resistant thermoplastic resin at a specified range. CONSTITUTION:A coefficient of linear expansion of a metal sheet 1 is 6X10<-6>mm/mm deg.C or less; concretely, an Fe-Ni alloy or an Fe-Ni alloy whose surface is covered with copper 11 metallurgically can be used suitably. Then, an aramid fiber cloth 4 must be impregnated with a heat-resistant thermoplastic resin 3 to be used as an insulating layer 2 covering the metal sheet: if the cloth is heated, it is contracted at about 0.2X10<-5>mm/mm deg.C; if the cloth is used with a specific rate of matrix with the heat- resistant thermoplastic resin, a substrate of a low coefficient of expansion is obtained. It is required to limit an amount of the resin to be impregnated into the aramid fiber cloth 4 to a range of 20-70wt.% with reference to a total amount. It is required to cover the insulating layer 2 with a layer thickness in a range of 30-300mum; if the thickness is less than 30mum, sufficient insulation performance cannot be secured; if the thickness exceeds 300mum, the low coefficient of linear expansion is hardly displayed.