Cutting drill and method for manufacturing printed wiring board

Abstract

A cutting drill includes a shank having a hole and formed to be gripped in a tool holder, and a drill body having a rod shape and locked into the hole of the shank. The shank has an axis around which the drill body rotates. The drill body has a cutting-edge portion forming a tip portion of the drill body and a neck portion having a diameter smaller than a diameter of the cutting-edge portion. The cutting-edge portion has a first cutting-edge portion and a second cutting-edge portion formed between the first cutting-edge portion and the neck portion. The first cutting-edge portion is contiguous to the second cutting-edge portion by a step portion such that the second cutting-edge portion has a diameter which is smaller than a diameter of the first cutting-edge portion.

What is claimed is: 
     
         1 . A method for manufacturing a printed wiring board, comprising:
 forming a penetrating hole in a base material for a printed wiring board, using a cutting drill comprising a shank gripped in a tool holder and a drill body having a rod shape and locked into the hole of the shank, the shank having an axis around which the drill body rotates, the drill body having a cutting-edge portion forming a tip portion of the drill body and a neck portion having a diameter smaller than a diameter of the cutting-edge portion, the cutting-edge portion having a first cutting-edge portion and a second cutting-edge portion formed between the first cutting-edge portion and the neck portion, and the first cutting-edge portion being contiguous to the second cutting-edge portion by a step portion such that the second cutting-edge portion has a diameter which is smaller than a diameter of the first cutting-edge portion;   forming a conductive layer in the penetrating hole such that the conductive layer extends between upper and lower surfaces of the base material for electrical connection; and   forming a conductive circuit on at least one of the surfaces of the base material.   
     
     
         2 . The method for manufacturing a printed wiring board according to  claim 1 , further comprising removing the first cutting-edge portion of the drill body. 
     
     
         3 . A method for forming a penetrating hole for a printed wiring board, comprising:
 providing a cutting drill comprising a shank gripped in a tool holder and a drill body having a rod shape and locked into the hole of the shank, the shank having an axis around which the drill body rotates, the drill body having a cutting-edge portion forming a tip portion of the drill body and a neck portion having a diameter smaller than a diameter of the cutting-edge portion, the cutting-edge portion having a first cutting-edge portion and a second cutting-edge portion formed between the first cutting-edge portion and the neck portion, and the first cutting-edge portion being contiguous to the second cutting-edge portion by a step portion such that the second cutting-edge portion has a diameter which is smaller than a diameter of the first cutting-edge portion;   forming a penetrating hole in a base material for a printed wiring board with the cutting drill;   forming a conductive layer in the penetrating hole such that the conductive layer extends between upper and lower surfaces of the base material for electrical connection; and   forming a conductive circuit on at least one of the surfaces of the base material.   
     
     
         4 . The method for forming a penetrating hole for a printed wiring board according to  claim 3 , further comprising removing the first cutting-edge portion of the drill body.