Importance

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Abstract

A circuit board capable of accomplishing an increase in current capacity and therefore a reduction in resistance of a through-hole conductive section each formed by filling a conductive paste in each of through-holes formed in a paper base insulating substrate by punching. A punching pin is thrust into the paper base insulating substrate provided on front and rear surfaces thereof with copper foil lands from a side of the front surface, resulting in the through-holes being formed. A drawing pin is inserted into each of the through-holes from a side of the rear surface of the insulating substrate through a rear opening of the through-hole, to thereby curve an inner peripheral portion of the rear copper foil land toward an interior of the through-hole and cut off any swell in the through-hole. The through-holes each are filled with the conductive paste, followed by curing the paste, so that the through-hole conductive section is formed for electrically connecting copper foil lands to each other.

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First Claim