Patent ID: 6708404
Filing Date: 2004-03-23
Classification: B23K,H05K,Y10T

Abstract:
A method for producing a multi-layered printed wiring board having at least three copper foil layers, which comprises:a. providing a stacked assembly comprising: at least a front copper foil layer having a first thickness, a reverse copper foil layer having a first thickness, and an internal copper foil layer provided between said front copper foil layer and said reverse copper foil layer; at least two resin layers alternating between said copper foil layers, to produce said stacked assembly having a top surface and a bottom surface; b. providing an auxiliary material for making a hole on said top surface of said stacked assembly and providing a backup sheet comprising a metal sheet and a backup resin layer, on said bottom surface of said stacked assembly such that said backup resin layer is in communication with said bottom surface of said stacked assembly, to form an assembly having a top and a bottom surface; c. subjecting said top surface of said assembly to pulsed oscillation from a carbon dioxide gas laser to form at least one through-hole traversing said layers of said assembly, to produce a holed assembly; d. reducing said first thickness of said front copper foil layer and said first thickness of said reverse copper foil layer, comprising chemically dissolving an amount of copper from said front copper foil layer and from said reverse copper foil layer of said holed assembly, whereby said first thickness is reduced to provide a second thickness, and removing copper foil burrs in communication with said through-hole which burrs extend into or beyond said through-hole, by steps comprising chemically dissolving said copper foil burrs, to produce a cleaned assembly, wherein said steps of thickness reducing and burr removing, are performed simultaneously; and e. plating said cleaned assembly with copper, to produce said multi-layered printed wiring board.