JP2003053577A - Top flat beam generation method and apparatus, and laser processing method and apparatus using the same - Google Patents

Abstract

[PROBLEMS] To generate a top flat beam with a simple structure and an inexpensive lens. A beam 1 having a Gaussian intensity distribution
2 is a spherical lens 3 having no condensing function in the central part (32A, 34A) and having a condensing function in the peripheral part (32B, 34B).
2 and 34, a top flat beam having a flat intensity distribution at the center is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for producing a top flat beam, and a laser processing method and apparatus using the same, and more particularly to improving the processing quality of laser processing using a laser drilling machine or the like. The present invention relates to a top flat beam generating method and device, a top flat beam generating spherical lens, and a laser processing method and device using the same.

[0002]

2. Description of the Related Art In processing a through hole or a via hole of a printed wiring board by a laser drilling machine, a laser beam 12 generated by a laser oscillator 10 is focused by a condenser lens 14 as shown in FIG. Processing point 22 on 22
Hole 16A having a diameter similar to that of A and having a diameter of about 0.2 to 1.5 mm
After passing through the mask 16 on which the mask is formed, the circular cross-section beam formed on the mask surface is collimated by the collimator lens 18 and then focused again by the condenser lens 20 of the imaging optical system to be processed 22 Is applied to the processing point 22A. Therefore, the intensity distribution of the laser light on the mask surface is transferred to the processed surface.

[0003]

However, in this method, the intensity distribution on the mask surface cannot be controlled arbitrarily, and depends on the beam mode of the main body of the laser oscillator 10. Therefore, the intensity distribution of a laser beam having a general single mode, rather than the multimode in which the central portion is relatively flat, is a Gaussian distribution in which the central portion is strong and the peripheral portion is weak, as shown in FIG. Therefore, processing point 22
A has the same intensity distribution in A as well, and the work piece (substrate)
The via hole 23 generated in 22 has a low aperture ratio and a strong central portion of the beam as shown in FIG. 2B with respect to the target shape as shown in FIG. Foil 2
4 had a problem that it was easily damaged.

In order to make the intensity distribution on the mask surface flat, the hole 16A may be made small so that only the flat central portion of the laser beam 12 passes through, but the energy efficiency is lowered. It is also conceivable to use an aspherical lens (defractive optics) instead of the spherical lens as the condenser lens 16, but the aspherical lens is very expensive because it is difficult to design and manufacture. I have a problem.

The present invention has been made to solve the above conventional problems, and a first object thereof is to generate a top flat beam at a low cost with a simple structure.

A second object of the present invention is to provide an inexpensive lens capable of producing a top flat beam.

A third object of the present invention is to realize laser processing using a top flat beam at low cost.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a beam having a Gaussian intensity distribution is not focused in the central portion,
By passing it through a spherical lens that has a light condensing function on the periphery,
The first problem is solved by generating a top flat beam having a flat intensity distribution in the central portion.

Further, the spherical lens is a convex lens having a flat central portion.

Alternatively, the spherical lens is a convex lens having a hole in the center.

The present invention also provides a top flat beam generator for generating a top flat beam having a flat central intensity distribution from a beam having a Gaussian intensity distribution. The first problem is solved by providing a spherical lens having no action and having a condensing action in the peripheral portion.

The present invention also has no light condensing function in the central portion,
The second problem is solved by a spherical lens for generating a top flat beam having a condensing function in the peripheral portion.

The present invention also provides a Gaussian distribution-like intensity distribution incident on the mask in a laser processing method in which the cross-sectional shape of the processing beam is defined by a mask to irradiate the workpiece. The third problem is solved by passing a laser beam through the spherical lens to form a top flat beam having a flat central intensity distribution.

The present invention also provides a laser processing apparatus,
A mask for defining the cross-sectional shape of the processing beam, and the spherical surface for making a laser beam having a Gaussian distribution-like intensity distribution incident on the mask into a top flat beam having a flat central intensity distribution. The third problem is solved by including the lens.

Further, by further comprising a condenser lens for controlling the intensity distribution of the top flat beam incident on the mask through the spherical lens, the top flat beam can be obtained at an arbitrary point. .

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

The first embodiment of the present invention uses a mask 1 in a laser processing apparatus similar to the conventional example as shown in FIG.
A condenser lens 14 for condensing the laser beam 12 on
Instead of the above, as shown in FIG. 3 (side view) and FIG. 4 (front view), the convex lens apex 30A of the spherical convex lens 30 is ground into a flat surface to use a spherical lens 32 as a flat surface portion 32A. . In the figure, 32B is a spherical surface portion.

The area to be cut is the hole 16A of the mask 16.
Can be made slightly larger than the size of, for example, a diameter of 1 to 3 mm.

When the laser beam 12 having a Gaussian distribution is incident on the spherical lens 32, the laser light passing through the lens flat surface portion 32A remains as it is and the laser light passing through the lens spherical surface portion 32B is collected as shown in FIG. As a result of being illuminated,
As shown in FIG. 6, the intensity distribution of the laser light at the point P on the output side is such that light passing through the flat surface portion 32A (non-condensing portion) and light passing through the spherical surface portion 32B (condensing portion) are superposed. It will be a match.

Therefore, by cutting the apex of the spherical convex lens 30 into a flat surface, it is possible to easily generate a top flat beam.

As the spherical lens having no light condensing function at the central portion and having the light condensing function at the peripheral portion, in addition to the lens in which the apex of the spherical convex lens is cut into a plane as in the first embodiment, As shown in FIG. 7, it is also possible to use a spherical convex lens 34 having a hole 34A in the center.

Further, as in the third embodiment shown in FIG. 8, the spherical lens 32 or 34 of the first or second embodiment and the condenser lens 36 are combined, and the position of the condenser lens 36 is indicated by an arrow A. As described above, by moving the laser beam 12 in the optical axis direction to adjust the mask transmittance, a top flat beam can be obtained at an arbitrary point P, and energy can be used more effectively.

By thus flattening the laser light intensity distribution on the mask surface, the energy distribution on the processed surface is simply flattened like the mask surface. Therefore, it is possible to improve the aperture ratio of the via hole and the like, prevent damage to the inner layer copper foil, and improve the processing quality.

According to the first and second embodiments, it is possible to manufacture the spherical convex lens which is an off-the-shelf product at a low cost by only additionally machining.

Although the present invention is applied to the laser drilling machine in the above-mentioned embodiment, the application target of the present invention is not limited to this, and is similarly applied to other laser processing devices such as a cutting machine. Applicable. In the case of a cutting machine, a beautiful cut surface can be obtained.

[0026]

According to the present invention, a top flat beam can be easily generated by using an inexpensive lens having a simple structure. Therefore, it is possible to improve the processing quality of laser processing with an inexpensive device.

[Brief description of drawings]

FIG. 1 is an optical path diagram showing a basic configuration of a laser processing apparatus.

FIG. 2 is a cross-sectional view for explaining a conventional problem

FIG. 3 is a side view showing a processing method of the first embodiment of the spherical lens for generating a top flat beam according to the present invention.

[Figure 4] Similarly, a front view

FIG. 5 is a side view showing the operation of the first embodiment.

FIG. 6 is a schematic diagram of the same

FIG. 7 is a side view showing a configuration of a second embodiment of a spherical lens for generating a top flat beam according to the present invention.

FIG. 8 is a side view showing an arrangement of main parts of a third embodiment according to the present invention.

[Explanation of symbols]

10 ... Laser oscillator 12 ... Laser beam 16 ... Mask 22 ... Workpiece 22A ... Processing point 30, 32, 34 ... Spherical lens 32A ... Flat part (non-light-collecting part) 32B, 34B ... Spherical part (light collecting part) 34A: Perforated part (non-condensing part) 36 ... Condensing lens

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Claims (8)

[Claims] 1. A beam having a Gaussian intensity distribution,
A method of producing a top flat beam, characterized by producing a top flat beam having a flat intensity distribution in the central part through a spherical lens having no condensing effect in the central part and having a condensing effect in the peripheral part. 2. The method for producing a top flat beam according to claim 1, wherein the spherical lens is a convex lens having a flat central portion. 3. The method for producing a top flat beam according to claim 1, wherein the spherical lens is a convex lens having a hole in the center thereof. 4. A top flat beam generator for generating a top flat beam having a flat central intensity distribution from a beam having a Gaussian intensity distribution, wherein the central portion has no focusing effect, An apparatus for producing a top flat beam, comprising a spherical lens having a light condensing function in the peripheral portion. 5. A spherical lens for producing a top flat beam, which has no light condensing function in the central part and has a light condensing function in the peripheral part. 6. A laser processing method in which a cross-sectional shape of a processing beam is defined by a mask to irradiate an object to be processed, wherein a laser beam having a Gaussian distribution-like intensity distribution is incident on the mask. A laser processing method, characterized in that a top flat beam having a flat intensity distribution in the central portion is passed through the spherical lens according to claim 5. 7. A mask for defining the cross-sectional shape of a processing beam, a laser beam incident on the mask having a Gaussian distribution-like intensity distribution, and a top flat beam having a flat central intensity distribution. A laser processing apparatus, comprising: the spherical lens according to claim 5 for: 8. The laser processing apparatus according to claim 7, further comprising a condenser lens for controlling the intensity distribution of the top flat beam incident on the mask through the spherical lens.