| 摘要 |
In the present invention, a reference conductive layer and a first surface conductive layer are respectively provided on a surface and a back face of a first base film. The first base film includes a first via hole penetrating the first surface conductive layer. After a first electroless plating layer and a first conductive material are sequentially grown on a surface of the first base film, a first coating conductive layer composed of the first electroless plating layer, the first conductive material and the first surface conductive layer, is etched to have a reduced thickness. Then, the first coating conductive layer is patterned to form a first wiring layer. In this manner, a desired pattern width can be obtained even in the case where the first coating conductive layer is patterned by isotropic etching such as wet etching.
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