| 摘要 |
PROBLEM TO BE SOLVED: To improve mechanical strength by setting the radio of the thickness of a metal plating on a wiring pattern to that of the pattern to be in a specific range, thereby forming a dense wiring pattern. SOLUTION: A copper foil 2 is adhered onto a board 1 by using an adhesive material, and a thickness (h) of the foil 2 is set to about half of a thickness H of a wiring pattern after metal plating, so that a ratio of a thickness of the plating to that of the pattern falls within a range of 3:1 to 1:3. Then, the foil 2 is coated with a photoresist 4, dried, and the photoresist 4 is exposed, developed by using a photomask corresponding to shapes of wiring patterns 2a, 2b to form a pattern of the photoresist 4 corresponding to the shape of the patterns 2a, 2b. Thus, the pattern of a dense pitch can be formed, and cracks or disconnections can be suppressed with respect thermal stresses or a mechanical bendings.
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