PROCESS FOR PRODUCING MULTILAYER PRINTED WIRING BOARD

摘要

PROBLEM TO BE SOLVED: To provide a process for producing a high density multilayer printed wiring board having a through hole exhibiting excellent workability, economy and reliability. SOLUTION: A copper clad multilayer substrate is made by aligning a multilayer board including electronic circuit conductors at high density in an inner layer and the copper foil is irradiated directly with a UV laser beam from above to open a through hole where the difference of diameter is 20% or less between the surface and rear and the hole diameter is preferably in the range of 20-100μm on the incoming side. Copper plating is carried out on the entire surface including the inside of the through hole by electroless plating and/or electroplating and then the central part of the hole is closed by a plating deposition layer projected from the opposite hole walls by electroplating. Subsequently, upper and lower spaces remaining in the through hole are filled by 90% or more with copper or a copper alloy deposited by performing electroplating using a reverse pulse power supply. At the same time, pattern plating is performed on the electronic circuit conductors and electronic circuits are formed on the opposite outer sides thus producing a multilayer printed wiring board. Thickness of the printed wiring board is preferably set in the range of 0.1-0.5 mm. COPYRIGHT: (C)2005,JPO&NCIPI