| 摘要 |
PROBLEM TO BE SOLVED: To obtain a low-cost double-layer flexible board by forming a dry plating film on an insulating film as a first layer, and an ultra-thin copper conductive film whose thickness is around 5-18μm on it, on which no defect of wiring is caused by pin holes. SOLUTION: A metallic substrate whose thickness is 50-200Åis formed on one side or both sides of an insulating film, without adhesive agent by a dry plating method using at least one of nickel, chrome and chrome oxide. The board with the metallic substrate is treated with a solution containing hydrazine whose strength is 0.5-4mol/l and ethylene diamin whose strength is 0.5-2mol/l, and an electroless copper plating is formed with a thickness of 0.01μm or more on the surface of the board. A copper conductive layer which is 5-18μm thick is further formed on the electroless copper plating film.
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