METHOD FOR PERFORATING MULTILAYERED PRINTED CIRCUIT BOARD

PROBLEM TO BE SOLVED: To improve connecting reliability by providing a conductor layer removing part in a conductor layer of an outermost layer of a printed circuit board, and emitting a laser via the removing part for removal of an insulating layer. SOLUTION: A circular conductor layer removing part 12a, having a diameter larger than the diameter of a laser beam 30 to be emitted in a next step, is formed at a conductor layer 11a of an outermost layer of a multilayered printed circuit board 10 (Fig. A), having a plurality of conductor layers 11 and insulating layers 12 provided between the layers 11. The layers 12 of a lower layer are partly formed as an exposed layer 12a. Then, the beam 30 having a smaller diameter than the diameter of the part 20 is emitted to the exposed part 12a of the layer 12 from above the part 12 to remove the layer 12 existing under it, and a hole 40 is perforated. Moreover, since the diameter of the hole 40 is normally about 30 to 300 μm, the diameter of the part 20 is normally preferably larger by about 50 to 200% the diameter of the hole 40. Then, it is copper plated to connect an upper layer circuit to a lower layer circuit by copper plating 50.