| 摘要 |
A perforation of a multilayer board has a surface-profile precision of 8 mum or less, and the ratio of a diameter or the minimum distance between the opposing edges on the opening surface thereof to the axial length is preferably from about 1:1 to 1:15. The multilayer board is fabricated by a punching machine comprising a punch and a stripper such that a required number of plates are prepared, the first plate is perforated by the punch and is pulled up by closely attaching it to the stripper while leaving the punch in the first bore, the second plate is perforated by the punch and is pulled up together with the first plate while leaving the punch in the second bore, and subsequently, the following plates are perforated by the punch and the perforated plates are stacked along the punch serving as a stacking axis sequentially.
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