JP4570182B2 - Laser processing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to laser processing for processing a workpiece by laser light, and more particularly to a laser processing apparatus for processing a workpiece by forming an image of laser light output from a laser oscillator.
[0002]
[Prior art]
Conventionally, as a method of processing a workpiece by forming an image of laser light output from a laser oscillator, a laser beam having a predetermined cross-sectional shape is formed by a pattern forming mechanism, and then the formed laser beam is processed. A method is known in which an image is formed on an object and an arbitrarily formed image pattern (laser processing spot) is formed on the workpiece.
[0003]
[Problems to be solved by the invention]
However, in the above-described conventional laser processing method, diffraction occurs in the laser transmission window when the laser beam passes through the laser transmission window of the pattern forming mechanism, so that interference is caused at the imaging position of the laser beam and the object is covered. An intensity distribution is generated in the imaging pattern on the workpiece. Note that this intensity distribution appears as periodic interference fringes whose pitch changes according to the wavelength of the laser beam and the size of the laser transmission window when the imaging lenses are the same, and the laser beam is reflected on the workpiece. The energy density of light will periodically rise and fall.
[0004]
For this reason, in the conventional laser processing method described above, processing is sufficiently performed at a portion where the intensity distribution of the imaging pattern is high on the workpiece, but processing is insufficient or not performed at all at a portion where the intensity distribution is low. It is difficult to find the proper processing conditions that satisfy the uniformity of laser processing on the workpiece, especially the type of workpiece or optical system. There is a problem that appropriate processing conditions cannot be found at all.
[0005]
In the conventional laser processing method described above, the size of the laser transmission window of the pattern forming mechanism needs to be as large as possible compared with the size of the cross-sectional shape of the laser beam in order to efficiently guide the laser beam to the workpiece. There is. Considering the case where a fine imaging pattern is formed on the workpiece while keeping the size of the laser transmission window large in this way, the imaging lens needs to be short-focused because the imaging magnification needs to be reduced. It is necessary to increase the distance between the pattern forming mechanism and the imaging lens.
[0006]
For this reason, in the conventional laser processing method described above, the focal length of the laser beam at the imaging position becomes extremely shallow by setting the imaging lens to a short focal point, and the workpiece is accurately placed at the imaging position. There is a problem that the processing reliability is lowered. Also, by making the imaging lens a short focal point and increasing the distance between the pattern forming mechanism and the imaging lens, the required aperture of the imaging lens is increased and the optical components such as the imaging lens are complicated. There is a problem that the size of the apparatus is increased and the cost is increased.
[0007]
The present invention has been made in consideration of such points, and can perform laser processing uniformly on a workpiece, improve processing reliability, and reduce the size and cost of the apparatus. An object of the present invention is to provide a laser processing apparatus capable of easily realizing the above.
[0008]
[Means for Solving the Problems]
The solution according to the present invention includes: a laser oscillator that outputs laser light; a pattern forming mechanism that forms a laser beam having a predetermined cross-sectional shape by forming the laser light output from the laser oscillator; and the pattern forming mechanism that forms the laser beam. An image forming lens for forming an image of the laser beam formed on the workpiece and forming a laser processing spot having a shape corresponding to the cross-sectional shape of the laser beam on the workpiece, and the pattern forming mechanism. A high-order diffracted light removing mechanism that removes a part of high-order diffracted light from the diffracted light contained in the laser beam, and a laser beam that is arranged between the laser oscillator and the pattern forming mechanism and output from the laser oscillator and a condenser lens for condensing, characterized in that the higher-order diffracted light removal mechanism is disposed between the imaging lens and the pattern forming mechanism A laser processing apparatus for.
[0009]
In the above-described solution , the pattern forming mechanism includes a shielding member that shields the laser beam output from the laser oscillator, and the shielding member has a laser transmission window that transmits only a part of the laser beam. preferable. Further, the high-order diffracted light removing mechanism includes a shielding member that shields the laser beam shaped by the pattern shaping mechanism, and this shielding member is a laser that transmits only low-order diffracted light out of the diffracted light contained in the laser beam. It is preferable to have a transmission window. Here, it is preferable that the pattern forming mechanism and the high-order diffracted light removing mechanism have a transmission window variable mechanism that changes the shape and size of the laser transmission window of the shielding member. The shielding member may be a holder that holds the imaging lens.
According to the above-described solution, since the high-order diffracted light among the diffracted light contained in the laser beam formed by the pattern forming mechanism is shielded and only the low-order diffracted light is transmitted, the laser beam The influence of interference at the image forming position can be suppressed, and the occurrence of non-uniform intensity distribution inside the image forming pattern can be effectively prevented. In addition, since the diffraction spread angle of the low-order diffracted light contained in the laser beam shaped by the pattern shaping mechanism can be increased, the laser transmission window of the high-order diffracted light removal mechanism can be increased and adjacent to each other. Adjustment of the dimension of the laser transmission window for separating the diffracted light of the order can be easily and easily performed.
[0010]
In addition, by condensing the laser light output from the laser oscillator by the condenser lens, the transmittance of the laser light in the pattern forming mechanism can be improved, and the loss of the laser light by the pattern forming mechanism is suppressed. The processing efficiency of the workpiece can be improved.
[0011]
Furthermore, by focusing the laser beam output from the laser oscillator with a condenser lens, it is possible to increase the imaging magnification even when forming a minute imaging pattern on the workpiece. There is no need to make the lens a short focal point or to increase the distance between the pattern forming mechanism and the imaging lens. For this reason, the depth of focus at the imaging position of the laser beam is increased to improve processing reliability, while preventing an increase in the required aperture of the imaging lens and complication of optical components such as the imaging lens. Therefore, it is possible to easily realize downsizing and cost reduction of the apparatus.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0013]
FIG. 1 is a diagram showing a configuration of an embodiment of a laser processing apparatus according to the present invention. As shown in FIG. 1, the laser processing apparatus includes a laser oscillator 1 that outputs a laser beam L, and a pattern forming that forms the laser beam L1 having a predetermined cross-sectional shape by shaping the laser beam L output from the laser oscillator 1. The mechanism 2 and an imaging pattern (with a shape similar to the cross-sectional shape of the laser beam L1 formed on the workpiece 6 by forming an image of the laser beam L1 formed by the pattern forming mechanism 2 on the workpiece 6. High-order diffraction among the diffracted light included in the laser beam L1 that is disposed between the imaging lens 3 that forms a laser processing spot) and the pattern forming mechanism 2 and is formed by the pattern forming mechanism 2. And a high-order diffracted light removing mechanism 4 for removing light.
[0014]
Here, the pattern forming mechanism 2 is formed of a shielding member that shields the laser beam output from the laser oscillator 1, and has a laser transmission window 2a that transmits only a part of the laser beam. The high-order diffracted light removing mechanism 4 is a shielding member that shields the laser beam L1 formed by the pattern forming mechanism 2, and transmits laser light that transmits only low-order diffracted light out of the diffracted light contained in the laser beam L1. A window 4a is provided.
[0015]
A condensing lens 5 that condenses the laser light L output from the laser oscillator 1 is provided between the laser oscillator 1 and the pattern forming mechanism 2.
[0016]
Next, the operation of the present embodiment having such a configuration will be described by taking as an example the case of forming a square imaging pattern on the workpiece 6. Here, in order to simplify the description, it is assumed that the optical components such as the imaging lens 3 and the condenser lens 5 are ideal optical systems having no aberration and the thickness in the direction of the optical axis La can be ignored. .
In this case, the pattern forming mechanism 2 is provided with a shielding member having a square laser transmission window 2a which is similar to the shape of the imaging pattern formed on the workpiece 6, and the center of the laser transmission window 2a is It arrange | positions so that it may come to the focus position of the condensing lens 5 on the optical axis La.
[0017]
Here, for example, a case is assumed where the beam diameter of the laser beam L is 3 mm, the spread angle is 1 mrad, the wavelength is 0.5 μm, and one side of the imaging pattern (square) on the workpiece 6 is 100 μm. In this case, if the laser transmission window 2a of the pattern forming mechanism 2 is a square having a side of 100 μm, the laser light L output from the laser oscillator 1 is condensed by the condenser lens 5 and then the pattern forming mechanism. The laser beam L is diffracted by the laser transmission window 2 a of the pattern forming mechanism 2. At this time, assuming that the focal length of the condenser lens 5 is 150 mm, the spot diameter in the laser transmission window 2a of the pattern forming mechanism 2 is about 150 μm, which is substantially equal to the diameter circumscribed by the laser transmission window 2a. .
[0018]
Such diffraction can be formulated using the Fraunhofer approximation as follows. That is, when the length of one side of the shape (square) of the laser transmission window 2a of the pattern forming mechanism 2 is a and the wavelength of the laser light L is λ, the zero-value width d of the diffraction spread angle of the zero-order light is d = 2. Xλ / a (rad), and the pitch of the dark lines of the interference fringes is changed in proportion to the value of λ / a. In the above example, since λ = 0.5 μm and a = 100 μm, the diffraction spread angle of the zero-order light is 10 mrad at the zero value width, and the intensity of the diffracted light included in the laser beam L1 is from the optical axis La. It becomes maximum at the position of the angle of 12.3 mrad (primary), 17.35 mrad (secondary), 22.4 mrad (third order),.
[0019]
2A and 2B are diagrams schematically showing a pattern of diffracted light included in the laser beam L1 formed by the pattern forming mechanism 2. FIG. Among these, FIG. 2A shows a pattern of diffracted light when the size of the laser transmission window 2a is large. In this case, the diffraction spread angle of the zero-order light becomes narrow, and the diffracted light of each order. Is also narrowed (see FIG. 2A). On the other hand, FIG. 2B shows a diffracted light pattern when the size of the laser transmission window 2a is small. In this case, the diffraction spread angle of the zero-order light is sufficiently large, The pitch of the diffracted light of the order is also sufficiently large (see FIG. 2B). When the laser transmission window 2a is a square having a side of 100 μm as in the above-described example, a pattern as shown in FIG. It is possible to reliably separate the diffracted light of the second order.
[0020]
The laser beam L shaped by the pattern shaping mechanism 2 is guided to the high-order diffracted light removing mechanism 4 where the high-order diffracted light contained in the laser beam L1 is shielded and low-order diffracted light (zero-order diffracted light is converted). Only) is transmitted through the laser transmission window 4a. Further, the laser beam L1 from which the higher-order diffracted light is removed by the higher-order diffracted light removing mechanism 4 is guided to the imaging lens 3 and forms a shape similar to the cross-sectional shape of the laser beam L1 on the workpiece 6. An image pattern is imaged.
[0021]
Note that the order of the diffracted light removed by the high-order diffracted light removing mechanism 4 can be adjusted to, for example, 3 to 3 by appropriately adjusting the distance from the pattern forming mechanism 2 of the high-order diffracted light removing mechanism 4 and the dimensions of the laser transmission window 4a. It can be arbitrarily selected within the range of the fourth order or higher.
Specifically, for example, in the case where an image is formed on the workpiece 6 by transmitting up to the second-order diffracted light among the diffracted light included in the laser beam L1, the pattern forming mechanism 2 is separated from the pattern forming mechanism 2 by 100 mm. The high-order diffracted light removing mechanism 4 having a square laser transmission window 4a having a side of 2 mm may be disposed, and the imaging lens 3 having a focal length of 50 mm may be disposed immediately after that. As a result, an equal-magnification imaging optical system that forms an image of the laser beam L1 including up to the second-order diffracted light on the workpiece 6 is obtained, and has a side of 100 μm at a position subsequent to the imaging lens 3 by 100 mm. A square imaging pattern can be obtained.
[0022]
FIGS. 3A, 3B and 3C are diagrams schematically showing the surface pattern of the workpiece.
Among these, FIG. 3A shows the surface pattern of the workpiece processed by the laser processing apparatus shown in FIG. 1, and in this case, a substantially uniform intensity distribution is obtained inside the imaging pattern. It was. On the other hand, FIGS. 3B and 3C show comparative examples when the high-order diffracted light removing mechanism 4 is not used. Among these, FIG. 3B shows a case where the size of the laser transmission window 2a of the pattern generation mechanism 2 is large. In this case, a fine strength pattern appears inside the imaging pattern. FIG. 3C shows a case where the size of the laser transmission window 2a of the pattern generating mechanism 2 is small. In this case, the density of the strong and weak patterns inside the imaging pattern is compared with FIG. 3B. However, a coarser and weaker pattern appeared as compared with FIG.
[0023]
As described above, according to the present embodiment, the high-order diffracted light removing mechanism 4 is arranged at a position separated from the pattern forming mechanism 2 by a predetermined distance, and the diffracted light contained in the laser beam L1 formed by the pattern forming mechanism 2 is Among them, since the higher-order diffracted light is shielded and only the lower-order diffracted light is transmitted, the influence of the interference at the imaging position of the laser beam L1 can be suppressed, and the work piece 6 is It is possible to effectively prevent a non-uniform intensity distribution from being generated inside the imaging pattern to be imaged.
[0024]
In addition, according to the present embodiment, the condenser lens 5 is disposed in front of the pattern forming mechanism 2, and the spot diameter of the laser light L output from the laser oscillator 1 is circumscribed to the laser transmission window 2 a of the pattern forming mechanism 2. Since the light is condensed to about the diameter, the transmittance of the laser light L in the pattern forming mechanism 2 can be improved, and even when the laser transmission window 2a of the pattern forming mechanism 2 has a small size. The processing efficiency of the workpiece 6 can be improved while suppressing the loss of the laser beam L due to the pattern forming mechanism 2. At this time, the laser beam L output from the laser oscillator 1 is condensed by the condenser lens 5, so that the diffraction spread angle of the low-order diffracted light included in the laser beam L 1 formed by the pattern forming mechanism 2 is reduced. Since it can be made large, the laser transmission window 4a of the high-order diffracted light removing mechanism 4 can also be made large, and the adjustment of the dimensions of the laser transmission window 4a for separating adjacent orders of diffracted light is easy and simple. It can be carried out.
[0025]
Furthermore, according to the present embodiment, by condensing the laser light L output from the laser oscillator 1 by the condenser lens 5, the size of the laser transmission window 2a of the pattern forming mechanism 2 can be reduced. Even when a fine imaging pattern is formed on the workpiece 6, the imaging magnification can be increased, the imaging lens 3 can be made into a short focal point, or between the pattern forming mechanism 2 and the imaging lens 3. There is no need to increase the distance. For this reason, the depth of focus at the imaging position of the laser beam L1 is increased to improve processing reliability, the required aperture of the imaging lens 3 is increased, and the optical components such as the imaging lens 3 are complicated. Therefore, it is possible to easily realize downsizing and cost reduction of the apparatus.
[0026]
In the above-described embodiment, the shapes and dimensions of the laser transmission windows 2a and 4a of the pattern forming mechanism 2 and the high-order diffracted light removing mechanism 4 are fixed, but a mechanism such as a variable slit or a variable aperture (transmission window variable). The shape and size of the laser transmission window may be changed by a mechanism).
[0027]
In the above-described embodiment, the shapes of the laser transmission windows 2a and 4a of the pattern forming mechanism 2 and the high-order diffracted light removing mechanism 4 are square, but the present invention is not limited to this, and any shape can be adopted. . Further, the shape of the laser transmission window 4a of the high-order diffracted light removing mechanism 4 does not have to be the same as the shape of the laser transmission window 2a of the pattern forming mechanism 2, and as long as high-order diffracted light contained in the laser beam L1 can be removed. Any shape can be adopted.
[0028]
Furthermore, in the above-described embodiment, the high-order diffracted light removing mechanism 4 is disposed between the pattern forming mechanism 2 and the imaging lens 3. However, the present invention is not limited thereto, and the imaging lens 3 and the workpiece 6 are not limited thereto. It is also possible to arrange between them.
[0029]
Furthermore, in the above-described embodiment, the high-order diffracted light removal mechanism 4 is a member independent of the imaging lens 3, but a holder (not shown) that holds the imaging lens 3 is a high-order diffracted light removal mechanism. 4 may be used. Further, when the cross-sectional shape of the imaging lens 3 has a size (aperture) suitable for receiving only low-order diffracted light among the diffracted light generated by the pattern forming mechanism 2, the imaging lens 3 It is also possible to fulfill the function of the high-order diffracted light removing mechanism 4 by utilizing the incidence and non-incidence of the laser beam L1 to the.
[0030]
In the above-described embodiment, the shapes and dimensions of the laser transmission windows 2a and 4a of the pattern forming mechanism 2 and the high-order diffracted light removing mechanism 4, the distance between the optical components, the focal length of the imaging lens 3, and the like. Although specific numerical values have been described above, these are merely examples, and it is naturally possible to appropriately select the laser oscillator 1 according to the characteristics, imaging magnification, processing content, and the like. is there. In addition, the number of optical components and the like are only given as an example. For example, a plurality of pattern forming mechanisms 2 and high-order diffracted light removing mechanisms 4 may be provided, or a plurality of imaging lenses 3 may be provided. .
[0031]
In the above-described embodiment, the condensing lens 5 condenses the spot diameter of the laser light L output from the laser oscillator 1 to a diameter that circumscribes the laser transmission window 2a of the pattern forming mechanism 2. However, the size of the spot diameter may be increased or decreased depending on the degree of uniformity of the intensity distribution inside the imaging pattern on the workpiece 6.
[0032]
【The invention's effect】
As described above, according to the present invention, laser processing can be uniformly performed on a workpiece, processing reliability is improved, and apparatus downsizing and cost reduction are easily realized. be able to.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an embodiment of a laser processing apparatus according to the present invention.
FIG. 2 is a diagram showing a pattern of diffracted light included in a laser beam formed by a pattern forming mechanism.
FIG. 3 is a diagram showing a surface pattern of a workpiece.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser oscillator 2 Pattern shaping mechanism 2a Laser transmission window 3 Imaging lens 4 Higher order diffracted light removal mechanism 4a Laser transmission window 5 Condensing lens 6 Workpiece

Claims (7)

A laser oscillator that outputs laser light;
A pattern forming mechanism for forming a laser beam having a predetermined cross-sectional shape by shaping the laser beam output from the laser oscillator;
An imaging lens that forms an image of a laser processing spot having a shape corresponding to a cross-sectional shape of the laser beam on the workpiece by imaging the laser beam formed by the pattern forming mechanism on the workpiece;
A high-order diffracted light removing mechanism for removing a part of the high-order diffracted light from the diffracted light contained in the laser beam formed by the pattern forming mechanism;
A condenser lens that is arranged between the laser oscillator and the pattern forming mechanism and condenses the laser light output from the laser oscillator, and
The pattern forming mechanism is arranged at a position where the laser beam is converged by the condenser lens,
The laser processing apparatus, wherein the high-order diffracted light removing mechanism is disposed between the pattern forming mechanism and the imaging lens and close to the imaging lens away from the pattern forming mechanism .   2. The pattern forming mechanism includes a shielding member that shields laser light output from the laser oscillator, and the shielding member has a laser transmission window that transmits only a part of the laser light. Laser processing equipment.   The laser processing apparatus according to claim 2, wherein the pattern forming mechanism includes a transmission window variable mechanism that changes a shape and a size of the laser transmission window of the shielding member.   The high-order diffracted light removing mechanism includes a shielding member that shields the laser beam formed by the pattern forming mechanism, and the shielding member transmits only a low-order diffracted light out of the diffracted light contained in the laser beam. The laser processing apparatus according to claim 1, comprising:   The laser processing apparatus according to claim 4, wherein the high-order diffracted light removing mechanism includes a transmission window variable mechanism that changes a shape and a size of the laser transmission window of the shielding member.   The laser processing apparatus according to claim 4, wherein the shielding member is a holder that holds the imaging lens.   A workpiece processed by the laser processing apparatus according to claim 1.

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