| 摘要 |
PURPOSE:To increase a wiring area by connecting circuits of intermediate conductor layers by a large through hole insulated therein, insulating and providing a small-diameter through hole in the hole of the large hole, and employing it as the circuit connection between front and rear conductor layers or from front and rear conductor layers to the intermediate conductor layer. CONSTITUTION:First and second intermediate conductor layers 3 are connected therebetween in a large through hole 6 in which the interior of the hole at the layers 3 is insulated, and an outer surface conductor layer 2 and fourth intermediate conductor layer 3 are connected therebetween in a small through hole 6 in which an insulator is inserted. In this case, the layer 2 of the outer layer of the outermost connecting conductor layer of the hole 6 of the conductor layer not connected to the holes 5, 6 can be used for wirings without providing an escape hole at the same position, and the diameter of the escaping hole is reduced that much at the layer 3 not connected for passing the hole 6. Thus, a wiring area can be increased. |
