| 摘要 |
A multilayer printed wiring board includes a plurality of internal conductor layers located at different levels and separated from each other by an interlayer insulator layer, and each of the internal conductor layers has a clearance hole at a position different from that of the other internal conductor layers. The multilayer printed wiring board is perforated at an expected position of the clearance hole of a selected internal conductor layer with a rotating drill bit, while continuously measuring a torque of a motor driving the rotating drill bit and an axial displacement of the rotating drill bit. A position of the internal conductor layers along a sample hole perforated in the multilayer printed wiring board is determined on the basis of the measured torque of the rotating drill bit and the axial displacement of the rotating drill bit. Thus, a mistake of the order stacking the internal conductor layers, and a positional deviation of each internal conductor layer in comparison with the other internal conductor layers, can be found at an early stage of a manufacturing of the multilayer printed wiring board.
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