Mitsubishi Gas Chemical Company, Inc.

Koichi Ishizuka

Morio Gaku

Hidenori Kinbara

Kenzi Ishii

Masakazu Motegi

A method for preparing a thin copper foil-clad substrate for the manufacture therefrom of circuit boards, which comprises subjecting a copper foil-clad circuit board substrate comprising an electrically insulating support having provided on one or both sides thereof a copper foil having an average thickness of 12 .mu.m or more to etching with an etching solution for copper, the etching being performed such that the whole surface of the copper foil is etched at a predetermined etching rate selected from the range of from 0.01 to 0.3 .mu.m/sec, thereby to reduce the thickness of the copper foil on at least one side of the insulating support to 10 to 80% of its original thickness, and the variation of the thickness of the copper foil remaining after the etching is within .+-.2.0 .mu.m on the basis of a desired thickness.

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Tokyo, Japan

Koichi Ishizuka