Process for producing a copper-clad laminate

Abstract

A process for producing a copper-clad laminate, which comprises a step (S2) of forming a copper foil of at least several micrometers on a planar conductive substrate by electrolysis, a step (S3) of roughening the surface of the copper foil, a step (S4) of laminating the copper foil together with the conductive substrate on an insulating substrate and tightly integrating the assembly by applying pressure and heat, and a step (S5) of separating only the conductive substrate. A metal film may exist between the conductive substrate and the copper foil. When the metal film has a thickness of 0.1 to 3 .mu.m, only the conductive substrate is separated with the metal film being firmly adhered to the copper foil surface and, when the metal film has a thickness of 70 to 250 .mu.m, it is separated together with the conductive substrate after the lamination. The copper foil formed by high-speed plating under the conditions of 6 to 12.0 m/sec in solution contact speed and 0.8 to 4.0 A/cm.sup.2 in current density has about the same flexibility as that of rolled and annealed copper. Thus, ultrathin copper-clad laminates with a copper foil of 10 .mu.m or less suited for flexible circuit boards can be produced in a short time using small equipment.