Patent ID: 7128844

Claim:
A method for producing a metal/ceramic circuit board, said method comprising the steps of: forming a metal layer of aluminum or an aluminum alloy, which contains aluminum as a principal component, on at least one side of a ceramic substrate; forming a resist having a predetermined shape on said metal layer; and etching and removing an undesired portion of said metal layer with an etchant which consists essentially of ferric chloride and water and which has a Baum'e degree of higher than 44° Be′, to form a metal circuit plate on said at least one side of said ceramic substrate, wherein said metal circuit plate has a corrugated range of 200 μm or less on a peripheral edge of said metal circuit plate, said corrugated range being the maximum distance between straight lines parallel to a linear peripheral edge of said metal circuit plate to be formed, and said metal circuit plate has a skirt spreading length of 200 μm or less, or a ratio (Ls/d) of 0.5 or less, said ratio (Ls/d) being a skirt spreading length (Ls) to a thickness (d) of said metal circuit plate, and said skirt spreading length being a distance between a plane perpendicular to a principal plane of said metal circuit plate at one end of a bottom face of said metal circuit plate and a plane perpendicular to a principal plane of said metal circuit plate at one end of a top face of said metal circuit plate on the same side as said one end of said bottom face of said metal circuit plate assuming that said distance is positive when said bottom face has a greater area than that of said top face.