JP2005144456A - Laser machining method and laser machining apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser machining method and a laser machining apparatus in which laser machining of high accuracy can be realized even when positional deviation attributable to a lift or the like of a surface of a work occurs. <P>SOLUTION: The laser machining apparatus comprises a laser beam oscillator 10, a mask 12 to shape laser beams emitted from the oscillator 10 to a predetermined beam diameter, a mirror 14 to deflect laser beams shaped by the mask 12, an aperture 16 to narrow down the diameter of the laser beams deflected by the mirror 14 to a predetermined value, and a processing lens 18 consisting of a convex lens to focus the laser beams passing through the aperture 16 on the surface of a work 20. The aperture 16 to narrow down the beam diameter of the laser beams shaped by the mask12 to the desired value is disposed before the processing lens 18. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laser processing method and apparatus, and more particularly to a laser processing method and apparatus capable of realizing high-quality processing even when the surface position of a workpiece varies with respect to an optical system.

  Generally, laser processing is performed in which a workpiece (hereinafter also referred to as a workpiece) such as a printed wiring board used for wiring of an electronic device or the like is irradiated with a laser beam to make a hole (for example, a patent) Reference 1).

  For example, when a so-called via hole for connecting wirings deposited on both sides of a substrate made of polyimide resin or the like is laser processed, it is processed into a desired shape with high accuracy. For this purpose, it is effective to make the laser beam form a top flat image on the workpiece surface.

JP-A-9-253877

  However, the laser beam focused on the workpiece surface in a flat top is usually displaced by about 0.2 mm from the imaging point, and the imaging state of the top flat is lost. In the case of deviation, there is a problem that the processing quality may be adversely affected.

  The present invention has been made to solve the above-mentioned conventional problems, and laser processing capable of performing processing such as drilling with high accuracy even when there is a positional shift caused by lifting or the like on the surface of the workpiece. It is an object to provide a method and an apparatus.

  The present invention relates to a laser processing method for condensing and processing a laser beam on the surface of a workpiece through an imaging optical system, and squeezing the laser beam in the middle of the imaging optical system, The problem is solved by enlarging the imaging depth on the surface.

  In the present invention, the laser beam is focused before a processing lens included in the imaging optical system.

In the present invention, when the necessary imaging depth is ΔF [μm], the aperture diameter of the laser beam: D [mm] is expressed by the following formula: D = 2f (R / ΔF)
(Where f is the focal length [mm] of the processing lens, and R is an allowable imaging shift [μm]).

  In the present invention, when the laser beam is shaped with a mask before the imaging optical system and formed on the surface of the workpiece, the shaped laser beam is at least first-order diffracted light from the mask. It is made to narrow down to the diameter which passes through.

At that time, the aperture diameter of the laser beam: D [mm] is expressed by the following formula: d + 2.23λL / d ≦ D
(Where d is the mask diameter [mm], λ is the wavelength of the laser to be used [mm], and L is the distance from the mask to the aperture [mm]). .

  The present invention also provides a diaphragm means for condensing laser light in the middle of the imaging optical system in a laser processing apparatus for condensing and processing the laser light on the surface of the workpiece via the imaging optical system. And the said subject is solved similarly by enlarging the imaging depth in the surface of the said to-be-processed object.

  In the present invention, the diaphragm means is installed in front of a processing lens included in the imaging optical system.

In the present invention, when the necessary imaging depth is ΔF [μm], the diameter of the diaphragm means for constricting the laser beam: D [mm] is expressed by the following equation: D = 2f (R / ΔF)
(Where f is the focal length [mm] of the processing lens, and R is an allowable imaging shift [μm]).

  In the present invention, when the laser beam is shaped with a mask before the imaging optical system and is imaged on the surface of the workpiece, the shaped laser beam is separated from the mask by the aperture means. The diameter is limited to at least the diameter through which the first-order diffracted light passes.

In this case, the diameter of the diaphragm means D (mm) for narrowing the laser beam is expressed by the following equation: d + 2.23λL / d ≦ D
(Where d is the mask diameter [mm], λ is the wavelength of the laser to be used [mm], and L is the distance from the mask to the aperture [mm]). .

  According to the present invention, when the laser beam is focused on the surface of the workpiece and processed, the beam diameter is reduced in the imaging optical system, so that the imaging depth can be expanded (increased). Become. Thus, by applying the camera aperture principle to the processing optical system, the imaging depth can be drastically improved, so that the range in which the laser beam can reach the top flat state can be expanded, High precision machining can be realized for workpieces.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In FIG. 1, the outline | summary of the laser processing apparatus of one Embodiment which concerns on this invention is shown.

  The laser processing apparatus of this embodiment includes a laser oscillator 10, a mask 12 that shapes laser light oscillated from the oscillator 10 into a predetermined beam diameter, and a mirror 14 that deflects the laser light shaped by the mask 12. And an aperture (aperture means) 16 that narrows the laser light deflected by the mirror 14 to a predetermined diameter, and a convex lens that forms an image of the laser light that has passed through the aperture 16 on the surface of the workpiece (workpiece) 20. The image forming optical system includes the mirror 14 and the processing lens 18.

  In the present embodiment, since the aperture 16 is disposed in front of the processing lens 18 (in the middle of the imaging optical system), the beam diameter of the laser light shaped by the mask 12 can be reduced to a desired size. . By arranging the aperture 16 in this way, the light energy on the surface (worked surface) of the workpiece 20 is slightly lowered, but the imaging depth can be increased.

  That is, as shown in FIG. 2, a convex lens (image forming) that is focused as shown in FIG. 2 (B) as compared to the optical system shown in FIG. When an aperture (aperture) is inserted in front of the lens), the imaging depth indicated by the arrow range on the image-side focal plane in the figure increases.

  Therefore, according to the present embodiment, since the imaging depth can be dramatically improved, when a laser beam is imaged on the surface of the workpiece 20 in the top flat mode, a double-pointed arrow with respect to the focus position is shown in FIG. As shown by the top flat range, compared with the conventional method in which the aperture 16 is not disposed, the range in which no damage occurs can be greatly expanded.

  As a result, when processing thin workpieces such as flexible wiring boards, even if the focus position shifts due to workpiece warpage, lifting, thickness variation, etc., the effect of the shift can be minimized. Therefore, it is possible to prevent the processing quality from being lowered.

  Therefore, as shown schematically in FIG. 4, an enlarged partial cross-section of the work 20 made of a flexible wiring board in which predetermined shapes of wiring 20B and 20C made of copper foil are formed on both front and back surfaces of the resin film 20A is shown. In addition, it is possible to effectively prevent the occurrence of damage 20D such as disconnection that is likely to occur in the thin bottom surface wiring 20C when the beam mode is sharp, and the via hole can be processed with high accuracy.

  In the present embodiment, the diameter of the aperture 16 inserted in front of the processing lens 18 is set as follows in relation to the mask 12.

  Now, as schematically shown in FIG. 5, when the focal length of the processing lens 18 is f [mm], the diameter of the aperture 16 is D [mm], and the allowable imaging deviation is R [μm], If the required resolution depth is ΔF [μm], the required aperture diameter can be obtained by the following equation. Here, R is a value determined by the resolution of the optical system, and is generally the minimum spot diameter of the processing lens.

    D = 2f (R / ΔF) (1)

  That is, when the imaging depth is doubled without changing the processing lens 18, the aperture diameter may be halved.

In other words, the smaller the aperture diameter D, the larger the imaging depth ΔF,
When the image from the mask 12 is transferred and formed on the processing surface, higher-order diffracted light from the mask 12 can be blocked accordingly.

  However, in this case, it is necessary to capture at least the first-order diffracted light so that light energy can be ensured as much as possible. For that purpose, it is necessary to set so as to satisfy the following expressions simultaneously.

    d + 2.23λL / d ≦ D (2)

  Here, L is the distance [mm] from the mask 12 to the aperture 16, d is the mask diameter [mm], and λ is the wavelength of the laser used [mm].

  Needless to say, the present invention is not limited to the above-described drilling of a wiring board, and can be applied to any laser processing technique using an imaging optical system.

  As described above, according to the present invention, laser processing such as drilling can be performed on the workpiece with high accuracy even when a positional deviation caused by lifting or the like occurs on the surface of the workpiece. Can do.

The block diagram which shows the outline | summary of the laser processing apparatus of one Embodiment which concerns on this invention Schematic diagram showing the principle of applying an aperture to the imaging optical system of a laser processing device Schematic diagram illustrating the operation of the present invention compared to the conventional example Enlarged partial sectional view of a work showing the effect of the present invention Schematic diagram showing the relationship between aperture diameter and mask diameter

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Laser oscillator 12 ... Mask 14 ... Mirror 16 ... Aperture (stop means)
18 ... Processing lens 20 ... Workpiece (workpiece)

Claims (10)

In a laser processing method for condensing and processing laser light on the surface of a workpiece via an imaging optical system,
A laser processing method, characterized in that laser light is throttled in the middle of the imaging optical system to increase the imaging depth on the surface of the workpiece.   The laser processing method according to claim 1, wherein the laser beam is focused before a processing lens included in the imaging optical system. When the required imaging depth is ΔF [μm], the aperture diameter of the laser beam: D [mm] is expressed by the following formula: D = 2f (R / ΔF)
(Where f is the focal length of the processing lens [mm], and R is an allowable imaging deviation [μm])
The laser processing method according to claim 1, wherein the laser processing method is set by:   When laser light is shaped by a mask before the imaging optical system and imaged on the surface of the workpiece, the shaped laser light is narrowed to a diameter through which at least the first-order diffracted light from the mask passes. The laser processing method according to claim 1, 2, or 3. The aperture diameter of the laser beam: D [mm] is expressed by the following formula: d + 2.23λL / d ≦ D
(Where d is the mask diameter [mm], λ is the wavelength of the laser used [mm], and L is the distance from the mask to the aperture [mm])
The laser processing method according to claim 4, wherein the laser processing method is set so as to satisfy the relationship. In a laser processing apparatus that focuses and processes laser light on the surface of a workpiece via an imaging optical system,
A laser processing apparatus characterized in that a diaphragm means for condensing laser light in the middle of the imaging optical system is installed to expand the imaging depth on the surface of the workpiece.   The laser processing apparatus according to claim 6, wherein the aperture means is installed in front of a processing lens included in the imaging optical system. When the required imaging depth is ΔF [μm], the diameter of the diaphragm means D for narrowing the laser beam: D [mm] is expressed by the following formula: D = 2f (R / ΔF)
(Where f is the focal length of the processing lens [mm], and R is an allowable imaging deviation [μm])
The laser processing apparatus according to claim 6, wherein the laser processing apparatus is set by:   When laser light is shaped by a mask before the imaging optical system and imaged on the surface of the workpiece, at least first-order diffracted light from the mask passes through the shaped laser light by the aperture means. The laser processing apparatus according to claim 6, wherein the laser processing apparatus is narrowed down to a diameter to be processed. The diameter of the diaphragm means for narrowing the laser beam: D [mm] is expressed by the following formula: d + 2.23λL / d ≦ D
(Where d is the mask diameter [mm], λ is the wavelength of the laser used [mm], and L is the distance from the mask to the aperture [mm])
The laser processing apparatus according to claim 9, wherein the laser processing apparatus is set so as to satisfy the relationship.

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