Importance

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Abstract

The range of selection of the material for a primary substrate and the material for a resin mask in a secondary substrate can be broadened, and short circuiting of a circuit can be reliably prevented. The shape of a primary substrate (1) is such that a circuit forming face (11) is in a convex form and a circuit non-forming face (12) is in a concave form, the difference in level between the circuit forming face (11) and the circuit non-forming face (12) is 0.05 mm, and the angle of side walls (13, 14) connecting the circuit forming face to the circuit non-forming face is 90.degree.. In order to apply a catalyst, a palladium catalyst solution was immersed in a bath having a water depth of 500 mm at a liquid temperature of 40.degree. C. for 5 min. Thereafter, a resin mask (3) is dissolved and removed, followed by electroless plating. As a result, the catalyst solution penetrates up to a part in which the creeping distance could have been increased, that is, up to both side walls (13, 14). That is, the catalyst penetration can be prevented, and short circuiting between conductive layers (50), that is, between circuits, can be prevented.

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First Claim