Patent ID: 7057133

Claim:
A differential diameter hole drilling method by which a through-hole having improved wall surface uniformity and a predetermined diameter is formed in a target material including opposed first and second major surfaces and having a thickness, comprising: generating a first laser output having sufficient energy density over a first spatial spot size to remove target material within a first spot area; directing the first laser output to impinge the target material on the first major surface and thereby form a pilot hole having a pilot hole diameter that corresponds to the diameter of the first spot area and that is less than the predetermined diameter of the through-hole; generating a second laser output having sufficient energy density over a second spatial spot size to remove target material within a second spot area; and directing the second laser output to impinge the target material on the second major surface and thereby form a through-hole that extends through the thickness of the target material and that has a through-hole diameter corresponding to the diameter of the second spot area and to the predetermined diameter, the formation of the through-hole involving the addition of thermal energy that escapes through the pilot hole and thereby limits thermal distortion of the through-hole wall and enhances its surface uniformity.