JP2002273589A - Laser drilling apparatus and method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] In a laser drilling machine that performs drilling by transferring an image of a circular aperture mask, fluctuation of a spot diameter of a laser beam caused by astigmatism is suppressed.
A change in the shape of a drilled hole is made small to improve the machining latitude of a laser drilling machine. SOLUTION: The astigmatism of a laser beam 2 emitted from a laser oscillator 1 is corrected, the corrected laser beam 2 is irradiated on a circular opening mask 4, and the laser beam 2 transmitted through the opening mask 4 is irradiated. An image is formed on the processing object 8 to perform a hole processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling apparatus and method for drilling holes using a laser, and more particularly to drilling holes by transferring a mask pattern to a printed circuit board material.

[0002]

2. Description of the Related Art FIG. 4 shows an optical system configuration of a conventional laser drilling apparatus. Laser beam 2 emitted from laser oscillator 1
Is applied to the circular aperture mask 4 via the reflection mirror 5. The laser beam 2 transmitted through the circular aperture mask 4
Is imaged by the galvanometer 6 and the fθ lens 7 at an arbitrary position in a scanable area of the galvanometer 6 on the workpiece 8. The imaging spot at this time is 9. At this position, pulsed laser irradiation
The drilling is performed one or more times, and the workpiece 8 is moved by the XY table 10 to process an arbitrary position of the workpiece 8.

[0003]

However, in this conventional laser drilling apparatus, when the distance between the material 8 to be processed and the fθ lens 7 for forming an image fluctuates, the image forming position and the material 8 to be processed are changed. And the spot shape where the laser is focused begins to blur, resulting in deformation of the hole diameter. The distance between the fθ lens 7 and the workpiece 8 may vary from several tens to several hundreds μm depending on the thickness of the workpiece 8 itself and the manner in which the workpiece 8 is held.

When the divergence angle of the laser beam 2 emitted from the laser oscillator 1 is different due to the difference in the structure of the laser oscillator 1, astigmatism may occur. As shown in FIG. 5, astigmatism also occurs when an external optical system such as the wavelength separation optical system 3 is inserted on the optical path. When this astigmatism occurs, as shown in FIG. 6, the spot shape 91 at the image forming position becomes a perfect circle according to the shape of the circular aperture mask, but as the distance from the image forming position increases, the spot shape 91 becomes larger. Spot shapes 92, 93, 94,
95 is an ellipse. Therefore, in an actual hole drilling machine, a change in the roundness of the spot shape 9 (short diameter of the drilled hole の 長 longer diameter of the drilled hole) due to a change in the distance between the fθ lens 7 and the material 8 to be processed is large. The degree is 0.9 or more, and the tolerance of the distance usable for processing is only about ± 100 μm.

[0005]

SUMMARY OF THE INVENTION To solve this problem, the present invention corrects astigmatism of a laser beam emitted from a laser oscillator, irradiates the corrected laser beam to a circular aperture mask, The laser beam transmitted through the aperture mask is imaged on the object to be processed, and a hole is formed.

[0006]

FIG. 1 is a schematic view of a laser drilling apparatus according to a first embodiment of the present invention.

In FIG. 1, a laser beam 2 emitted from an oscillator 1 having astigmatism is spread by a cylindrical collimator 11 composed of a pair of cylindrical lenses with respect to one direction having a different spread angle of the laser beam 2. Adjustments are being made. At this time, the interval between the cylindrical collimators 11 is adjusted so that the light condensing positions of the fθ lens 7 in the direction in which the adjustment is performed and the direction in which the adjustment is not performed are at the same distance from the lens. In an actual device, the reflection mirrors 5 are arranged for the delivery of the laser beam 2, and the arrangement and the number are not limited to those shown in FIG. The laser beam 2 that has passed through the cylindrical collimator 11 is applied to a circular aperture mask 4, and the laser beam that has passed through the mask is positioned at an arbitrary position on the workpiece 8 by a galvanometer 6. At this time, the shape of the imaging spot 9 on the workpiece 8 is
Shown in Since the astigmatism is corrected, the roundness of the spot shape when the distance to the image forming position changes is almost the same as the spot shape 91 at the image forming point.

In an actual processing machine, a laser beam 2 is split by a beam splitter on an optical path behind a circular aperture mask, and a plurality of laser beam scanning units each of which is a combination of a galvanometer and an fθ lens are prepared and processed simultaneously. It is carried out.

FIG. 2 is a schematic view of a laser drilling apparatus according to a second embodiment of the present invention.
In the case of the laser drilling apparatus according to the invention described in JP-A-198168, since the wavelength separation optical system 3 includes a prism and a diffraction grating, astigmatism is generated. In this case, astigmatism is corrected by inserting a cylindrical collimator 11 between the wavelength separation optical system 3 and the circular aperture mask 4. by this,
As in the first embodiment, a change in the spot shape 9 as shown in FIG. 3 occurs, and a change in the roundness of the machined hole shape can be slightly suppressed.

[0010]

As described above, according to the present invention, the astigmatism of a laser beam emitted from a laser oscillator is corrected, the corrected laser beam is irradiated on a circular aperture mask, and transmitted through the aperture mask. The astigmatism can be corrected by imaging the laser beam that has been formed on the object to be processed and performing hole processing, and the variation in the roundness of the processing hole shape when it deviates from the imaging position is moderate. can do. This makes it possible to increase the latitude of the distance that can be used for processing.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a laser drilling apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a laser drilling apparatus according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram showing a spot shape of a laser beam near an imaging position according to the embodiment of the present invention;

FIG. 4 is a schematic view of a conventional laser drilling apparatus.

FIG. 5 is a schematic view of a conventional laser drilling apparatus.

FIG. 6 is a schematic view showing a conventional spot shape of a laser beam near an imaging position.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser oscillator 3 Wavelength separation optical system 4 Circular aperture mask 8 Work material 11 Cylindrical collimator

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Claims (4)

[Claims] 1. A laser oscillator, a cylindrical collimator that corrects astigmatism by entering a laser beam emitted from the laser oscillator, a circular aperture mask that irradiates the laser beam emitted from the cylindrical collimator, and the aperture mask And a condenser lens for forming a laser beam transmitted through the laser beam on the object to be processed. 2. A laser oscillator according to claim 1, wherein said laser oscillator emits laser beams in a plurality of wavelength bands, and wavelength separating means for selecting a wavelength band of said laser beam is disposed between said laser oscillator and said cylindrical collimator. Item 4. The laser drilling device according to Item 1. 3. The laser drilling device according to claim 1, wherein the cylindrical collimator includes a pair of cylindrical lenses. 4. A step of correcting astigmatism of a laser beam emitted from a laser oscillator, a step of irradiating the corrected laser beam to a circular aperture mask, and processing a laser beam transmitted through the aperture mask. Forming an image on an object and performing hole processing.