Method and apparatus for laser drilling holes with gaussian pulses
AssigneeElectro Scientific Industries, Inc.
InventorsJeff Howerton, David Childers, Brian Johansen, Mehmet Emin Alpay
Life of this patent
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Abstract
An improved method and apparatus for drilling tapered holes in workpieces with laser pulses is presented which uses defocused laser pulses to machine the holes with specified taper and surface finish while maintaining specified exit diameters and improved system throughput. A system is described which can also drill holes with the desired taper and surface finish without requiring defocused laser pulses.
Claims17
An improved method for forming a through hole in a workpiece, including the steps of producing a laser pulse with a laser, modifying said laser pulse with optics, and directing said laser pulse to impinge upon said workpiece, said through hole having a taper, a surface finish and an exit diameter, said workpiece including substantially homogeneous metallic material and having a top surface and an ablation threshold, said laser pulse having a spot size, a pulse duration and a peak power, the improvement comprising the further steps of:
- producing with said laser said laser pulse, having said peak power at least about 20% greater than said ablation threshold of said workpiece and said pulse duration greater than 10 nanoseconds, and;
- modifying, with said optics, said laser pulse to have said spot size having a 1/e2 diameter at said top surface of said workpiece greater than about two times said exit diameter of said through hole, and;
- directing said at least one modified laser pulse to remove material from an intended volume of said workpiece thereby creating said through hole with said exit diameter, said surface finish and said taper.
An improved system for forming through holes in a workpiece with at least one laser pulse, said system including a controller, a laser and optics, said through hole having a taper, a surface finish and an exit diameter, said workpiece including substantially homogeneous metallic material and having a top surface and an ablation threshold, and said laser pulse having a spot size, pulse duration and peak power, the improvement comprising:
- a controller operatively connected to said laser and said optics to produce at least one laser pulse with said peak power about 20% greater than said ablation threshold of the workpiece, said spot size having a 1/e2 diameter at said top surface of said workpiece greater than about two times the exit diameter of said through hole and said pulse duration greater than about 10 nanoseconds and direct it to said workpiece thereby producing said through hole with said taper, said surface finish and said exit diameter.
An improved through hole for transmitting light through a workpiece having a top diameter, an exit diameter, a taper and a surface finish, the improvements comprising:
- a substantially circular exit diameter which is between 20 microns and 200 microns in diameter;
- a top diameter which is at least 1.5 times the exit diameter;
- a taper equal to or greater than 1.5 and which is continuous and smooth from exit diameter to top diameter and;
- a surface finish which is substantially smooth and substantially free of material initially ejected from the hole volume and redeposited on the surface.
Dependencies are inferred from the claim text.