To keep pace with the recent progress in high-density packaging technology, a new printed wiring technology was investigated. The purpose of this technology was to form extremely fine-line patterns on a large-sized organic substrate. A new wiring pattern transfer method was proposed cc satisfy the following requirements: the conductor is made thick to minimize the wiring resistance, continuous production is a capability, and other kinds of substrates can he used. The processing steps of this new method are as follows. First, a photoresist pattern is formed en a copper foil and wiring conductors ate formed by electroplating. After the photoresist is removed, the copper foil with the wiring conductors is laminated with an organic substrate after an adhesion promoting treatment such as the brown oxide coating. After first making through-holes and then plating them, the starting copper foil is etched away. To automatically stop the copper etching, a metal, which is resistive to the copper etching solution, is used as the barrier layer. The barrier and conducting metals are deposited sequentially in that order by the pattern plating. The resolution of the pattern and the thickness of the wiring conductor are determined by the property of the photoresist. By using the photoresist employed in this study, the minimum conductor width of 20 μm was achieved. It was also possible to make the conductor thicker than 100 μm by selecting the proper photoresist. Flexible wiring boards, double-sided wiring boards and multilayer printed wiring boards, fabricated as test products, showed that the wiring pattern transfer method has a vast potential for the fine-line formation. [ABSTRACT FROM AUTHOR]