METHOD OF FORMING THROUGH HOLE
A method of forming a through hole, wherein a spot of a laser light scans along a predetermined path and forms a through hole includes a first process in which the spot of the laser light circulates along an inner path from a predetermined first point on the inner path and reaches a predetermined second point. The inner path is positioned at an inner side relative to an outer path. The predetermined second point is positioned before the spot of the laser light returns to the predetermined first point. The method includes a second process in which the spot of the laser light moves along a transition path and reaches a predetermined third point on the outer path. The method includes a third process in which the spot of the laser light circulates along the outer path from the predetermined third point and returns to the predetermined third point.
1 . A method of forming a through hole, wherein a spot of a laser light scans along a predetermined path of a surface of a plate material and forms a through hole on the plate material, the method comprising:
a first process in which the spot of the laser light circulates along an inner path from a predetermined first point on the inner path and reaches a predetermined second point, the inner path being positioned at an inner side by a predetermined distance relative to an outer path corresponding to an inner peripheral edge of the through hole, the predetermined second point being positioned before the spot of the laser light returns to the predetermined first point;
a second process in which the spot of the laser light moves along a transition path extended from the predetermined second point towards the outer path and reaches a predetermined third point on the outer path; and
a third process in which the spot of the laser light circulates along the outer path from the predetermined third point and returns to the predetermined third point.
2 . The method of forming a through hole according to claim 1 , wherein the predetermined distance is smaller than a plate thickness of the plate material.
3 . The method of forming a through hole according to claim 1 , wherein a crossing angle of an end portion of the transition path and an end portion of the outer path is equal to or larger than 90 degrees.
4 . The method of forming a through hole according to claim 1 , wherein a circulation direction of the spot of the laser light in the first process and a circulation direction of the spot of the laser light in the third process are same as each other.
5 . The method of forming a through hole according to claim 1 , wherein the predetermined distance between the inner path and the outer path is set to be a half of a plate thickness of the plate material.
6 . The method of forming a through hole according to claim 1 , wherein the transition path is provided to extend from the predetermined second point towards a side opposite to a moving direction on the inner path and towards an outer side of the inner path.
7 . The method of forming a through hole according to claim 1 , wherein an angle between the transition path and a tangent line at the predetermined third point of the outer path is larger than 90 degrees.