Laser processing device

Abstract

Provided is a laser processing device capable of reducing variations in the size of an inclination angle in a scanning region and the amount of processing position errors, which are caused by a shift between the center position of the scanning region and a vertical incidence position. The table drive unit and the galvanometer drive unit are controlled on the basis of the machining position coordinates corrected on the basis of the offset between the center position of the scanning region and the vertical incidence position of the laser light, so that the scanning region is positioned at a position at which the laser light vertically enters the center position of the scanning region. The galvanometer mirror is positioned such that the laser beam is incident on the corrected machining position coordinates.

Description

Technical Field

[0001] The present invention relates to a laser processing device for drilling holes in a printed substrate, and in particular to a laser processing device for drilling holes by deflecting laser light in two-dimensional directions and irradiating the printed substrate with the laser light via an Fθ lens. Background Art

[0002] In a laser processing device for drilling holes in a printed substrate, for example, as disclosed in Patent Documents 1 and 2, a galvanometer scanner is used to deflect the laser light emitted from a laser oscillator in a two-dimensional direction and irradiate the laser light onto the printed substrate as a workpiece placed on a worktable through an Fθ lens. Figure 1 This is a schematic block diagram of a conventional laser processing device. Figure 1 A conventional laser processing apparatus will be described.

[0003] Conventional laser processing devices include: a laser oscillator 1, which emits laser light; an acousto-optic modulator (AOM) 2, which splits the laser light into two directions, the machining direction and the non-machining direction; a damper 3, which absorbs the laser light split into the non-machining direction by the AOM 2; a galvanometer scanner 4, which deflects the laser light split into the machining direction by the AOM 2 in two dimensions; an Fθ lens 5, which focuses the laser light deflected by the galvanometer scanner 4 onto a printed circuit board 6; a stage 7, which supports the printed circuit board 6; and a stage drive 8, which moves the stage 7 in the X and Y directions. The galvanometer scanner 4 includes a first galvanometer mirror 41, which is positioned about the rotation axis by a first galvanometer motor 43, and a second galvanometer mirror 42, which is positioned about the rotation axis by a second galvanometer motor 44. The galvanometer scanner 4 and the Fθ lens 5 are held by a machining head (not shown). By moving the machining head in the Z-axis direction, the height focus position of the Fθ lens 5 can be adjusted.

[0004] The galvanometer scanner 4 divides the processing area of ​​the printed circuit board 6 into a plurality of scanning areas 9 for deflecting the laser beam, and drilling is performed sequentially in each scanning area.

[0005] Reference numeral 10 denotes a laser oscillation control unit that instructs the oscillation and attenuation of the laser light in the laser oscillator 1. Reference numeral 11 denotes an AOM control unit that controls the operation of the AOM 2. Reference numeral 12 denotes a galvanometer control unit that controls the operation of the galvanometer scanner 4. Reference numeral 13 denotes a stage control unit that controls the drive of the stage drive unit 8. Reference numeral 14 denotes an overall control unit that controls the various components of the laser processing apparatus and the overall operation of the apparatus. This unit is implemented, for example, by a program-controlled processing device and includes a memory unit that internally stores various types of information. The overall control unit 14 has control functions other than those described above and is also connected to blocks not shown.

[0006] Based on the processing position coordinates pre-input as a processing program, the overall control unit 14 generates and stores table data for controlling the table drive unit 8, galvanometer data for controlling the galvanometer scanner 4, laser data for controlling the laser oscillator 1, and AOM data for controlling the AOM 2. The overall control unit 14 then generates and stores these data. Based on the stored data, the overall control unit 14 issues operation command signals to each control unit, thereby performing processing.

[0007] More specifically, the overall control unit 14 performs control based on the above-mentioned data, so that the laser processing device operates as follows. First, the workbench 7 on which the printed substrate 6 is mounted is moved and positioned in such a manner that the center position of the scanning area 9 to be processed is consistent with the center axis of the Fθ lens 5. Next, within the scanning area 9, the galvanometer mirrors 41 and 42 are rotated and positioned in such a manner that the laser is incident on the processing position coordinates. In addition, the laser light is emitted from the laser oscillator 1, branched in the processing direction in the AOM2, and focused onto the printed substrate 6 through the Fθ lens 5 for processing. When the processing of one scanning area 9 is completed, the center position of the next scanning area is positioned in such a manner that it is consistent with the center axis of the Fθ lens 5, and processing is performed in sequence.

[0008] In such laser processing devices, as the incident position of the laser light deflected by the galvanometer scanner 4 on the Fθ lens moves away from the center of the lens, the laser light passing through the lens and incident on the substrate is tilted relative to the lens's central axis. Furthermore, as described in Patent Document 2, for example, if the surface of a printed circuit board has minute irregularities, the tilt of the laser light incident on the substrate can cause two-dimensional positional errors in the processing position. It should be noted that, in addition to the irregularities of the substrate itself, if the surface of the worktable 7 has minute irregularities, the printed circuit board 6 mounted thereon can bend in accordance with the worktable 7, sometimes resulting in processing positional errors.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-71153

[0012] Patent Document 2: Japanese Patent Application Laid-Open No. 2020-49531 Summary of the Invention

[0013] [Problems to be solved by the invention]

[0014] In the laser processing device described above, the laser optical axis at the galvanometer origin, which serves as the center of the galvanometer mirror's swing angle, is designed to coincide with the central axis of the Fθ lens 5, resulting in vertical incidence of the laser light at the center of the scanning area. Therefore, when the processing device is assembled according to this design, the laser light is vertically incident at the center of the scanning area and tilts as it moves away from the center. In other words, if the substrate surface has irregularities, the potential for processing position error increases as the area moves away from the center.

[0015] However, it's difficult to assemble the system so that the laser's optical axis at the galvanometer's origin is perfectly aligned with the center axis of the Fθ lens. Specifically, it's difficult to assemble the system so that the laser beam is perpendicularly incident at the center of the scanning area. Furthermore, the offset between the center of the scanning area and the point where the laser beam is perpendicularly incident (hereinafter referred to as the perpendicular incident position) presents the following problems.

[0016] Figure 2 This graph shows the tilt angle of the laser within the scanning area when the center position of the scanning area is offset from the perpendicular incident position. The absolute value of the tilt angle in the X direction is used, but the same applies to the Y direction. As shown in the figure, when the center position C of the scanning area is offset from the perpendicular incident position V, the tilt angle becomes excessive at one end A of the scanning area, potentially causing a processing position error on the substrate surface exceeding the allowable value.

[0017] In this case, in order to keep the position error within the allowable value, that is, to keep the tilt angle within the allowable value, it is conceivable to simply set the scanning area 9 smaller so as not to use the range exceeding the allowable value on the side of the end A. However, if the scanning area 9 is set smaller, the number of scanning areas 9 in the entire substrate 6 will increase accordingly. However, if the number of scanning areas increases, the number of stage movements increases, which leads to problems such as an increase in the processing time required for one substrate, which is not appropriate.

[0018] Therefore, the purpose of the present invention is to solve the problems in the above-mentioned prior art and to provide a laser processing device that can reduce the deviation in the size of the inclination angle within the scanning area caused by the offset between the center position of the scanning area and the vertical incident position, that is, the deviation in the amount of processing position error that may be generated, and can improve the accuracy of the processing hole position without reducing the scanning area.

[0019] [Methods used to solve the problem]

[0020] In order to solve the above-mentioned problems, the present invention is a laser processing device, which comprises: a laser oscillator that oscillates laser light; a galvanometer mirror that deflects the laser light in a two-dimensional direction; an Fθ lens that focuses the laser light deflected by the galvanometer mirror onto a workpiece; a worktable that carries the workpiece and is movable in a horizontal direction; a galvanometer drive unit that rotationally drives the galvanometer mirror; a galvanometer control unit that controls the galvanometer drive unit; a worktable drive unit that drives the worktable; and a worktable control unit that controls the worktable drive unit. The laser processing device performs processing based on processing position coordinates of a pre-stored program, and is characterized in that the worktable drive unit and the galvanometer drive unit are controlled based on the processing position coordinates corrected based on the offset between the center position of the scanning area and the vertical incident position of the laser, so that the scanning area is positioned at a position where the laser light is vertically incident on the center position of the scanning area, and the galvanometer mirror is positioned so that the laser light is incident on the corrected processing position coordinates.

[0021] [Effects of the Invention]

[0022] According to the present invention, the position accuracy of machined holes can be improved by reducing the variation in the tilt angle within the scanning area caused by the deviation between the center position of the scanning area and the vertical incidence position, that is, the variation in the amount of machining position error that may occur. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic block diagram of a conventional laser processing device.

[0024] Figure 2 This is a graph showing the tilt angle of the laser light in the scanning area when the center position of the scanning area is offset from the vertical incident position.

[0025] Figure 3 This is a schematic block diagram of a laser processing apparatus in one embodiment of the present invention.

[0026] Figure 4 This is a graph for explaining a method for measuring the center deviation amount in one embodiment of the present invention.

[0027] Figure 5Schematic diagram showing the positional relationship of a scanning area before and after correction when the Fθ lens is used as a reference in one embodiment of the present invention. DETAILED DESCRIPTION

[0028] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. It should be noted that descriptions of the same parts as those described as the prior art will be omitted.

[0029] Figure 3 This is a schematic block diagram of a laser processing apparatus according to one embodiment of the present invention. The overall control unit 14 includes an offset storage unit 15. The offset storage unit 15 stores the offsets in the X and Y directions (hereinafter also referred to as "center offsets") between the center position of the scanning area 9 and the vertical incidence position in the XY coordinates.

[0030] Next, the operation of the laser processing apparatus in one embodiment of the present invention will be described. Before using the processing apparatus, the center offset is calculated in advance and stored in the offset storage unit 15. The center offset is calculated, for example, as follows.

[0031] First, a flat plate (acrylic plate) for test processing is placed on the workbench 7. As the flat plate for test processing, for example, an acrylic plate can be used that has no micro-concavities on its surface, does not follow the undulations of the workbench, and has a flat surface when placed on the workbench. Next, the distance between the Fθ lens 5 and the surface of the acrylic plate is adjusted so that the focal position is aligned with a position at an arbitrary distance from the surface of the acrylic plate in the height direction. In addition, within the scanning area, test processing is performed based on a test processing program in which a plurality of processing position coordinates are arranged at predetermined intervals on a straight line parallel to the X-axis and containing the center position coordinates of the scanning area, and the error amount of each processing position coordinate compared to the actual processing position is measured. It should be noted that the flat plate for test processing can also be made of materials other than acrylic, such as a glass plate, as long as it has no micro-concavities on its surface and does not follow the micro-undulations of the workbench. This makes it possible to calculate the center offset amount in the scanning area regardless of the micro-undulations on the workbench surface.

[0032] Figure 4 This is a diagram for explaining the method of measuring the center offset in one embodiment of the present invention, showing the processing position error in the X direction after the test processing. As shown in the figure, in the straight line (or approximate straight line) N obtained by connecting the error amounts of each position, the position where the position error is 0 can be used as the vertical incident position V. In addition, the offset ΔX between the determined vertical incident position V and the center position C of the scanning area can be set as the offset in the X coordinate. In addition, by Figure 4While the method for calculating the offset in the X direction has been described, the same method can be used for the Y direction. It should be noted that by setting the focal position away from the surface rather than on the acrylic plate surface, the tilt angle relative to the lens's central axis is more easily expressed as an error in the position of the machined hole on the acrylic plate surface, making it easier to measure the vertical incidence position.

[0033] Next, the machining operation of the laser machining device of the present invention will be described. The overall control unit 14 generates and stores table data, galvanometer data, and other data based on the corrected machining position coordinates obtained by adding the center offset stored in the offset storage unit to the machining position coordinates previously input as a program. The overall control unit 14 then controls the various control units based on the data based on the corrected machining position coordinates.

[0034] More specifically, the overall control unit 14 controls the laser processing apparatus based on the aforementioned stage data, etc., generated based on the corrected position coordinates, so that the laser processing apparatus operates as follows. First, the stage 7, on which the printed substrate 6 is mounted, is moved so that the pre-corrected center position of the scanning area 9 to be processed coincides with a position offset from the center axis of the Fθ lens by an amount equal to the center offset. In other words, the scanning area 9 is positioned so that the pre-corrected center position is at a perpendicular incident position. It should be noted that, in order to position the scanning area to be processed, coordinates serving as a positioning reference are set within the scanning area. However, by moving the stage so that these reference coordinates are offset by an amount equal to the center offset, the center position of the scanning area 9 is positioned at a perpendicular incident position.

[0035] Next, within this scanning area 9, the galvanometer mirrors 41 and 42 are rotated and positioned so that the laser beam is incident on a position coordinate that is offset from the pre-calibration processing position coordinate by an amount equal to the center offset. Furthermore, laser beams are oscillated from the laser oscillator 1, branched in the processing direction by the AOM 2, and focused on the surface of the printed circuit board 6 via the Fθ lens 5 to perform processing. When processing of one scanning area 9 is completed, the process moves to the next scanning area in a similar manner and continues processing in sequence.

[0036] Figure 5 This is a schematic diagram showing the positional relationship of the scanning area before and after correction based on the Fθ lens in one embodiment of the present invention. The white circle represents the processing position coordinates before correction, and the black circle represents the processing position coordinates after correction. In addition, the white × mark represents the center position of the scanning area before correction, and the black × mark represents the same position after correction. Furthermore, the dotted line box represents the scanning area before correction, and the solid line box represents the scanning area after correction. Figure 5As shown, according to the present invention, the entire scanning area can be offset so that its center is aligned with the vertical incidence position. This reduces the deviation in the tilt angle within the scanning area, that is, the deviation in the processing position error. This allows the processing position error that may occur due to minute irregularities on the substrate surface to be brought within an acceptable range without reducing the scanning area.

[0037] In addition, according to the present invention, even when the position error at the end of the scanning area is within the allowable range, the center position of the scanning area and the coordinates of each processing position can be corrected to match the position of the laser vertical incidence. Therefore, the position error that may occur between the two ends of the scanning area can be made equal, and the processing quality can be further improved.

[0038] Description of Reference Numerals

[0039] 1: Laser oscillator, 2: Acousto-optic device (AOM), 3: Damper, 4: Galvanometer scanner, 41: First galvanometer mirror (Y direction), 42: Second galvanometer mirror (X direction), 43: First galvanometer motor (Y direction), 44: Second galvanometer motor (X direction), 5: Fθ lens, 6: Printed substrate (workpiece), 7: Worktable, 8: Worktable drive unit, 9: Scanning area, 10: Laser oscillation control unit, 11: AOM control unit, 12: Galvanometer control unit, 13: Worktable control unit, 14: Overall control unit, 15: Offset storage unit

Claims

1. A laser processing device comprising: a laser oscillator that oscillates laser light; a galvanometer mirror that deflects the laser light in two dimensions; An Fθ lens that focuses the laser light deflected by the galvanometer mirror onto a workpiece; a worktable on which the workpiece is placed and which is movable in a horizontal direction; a galvanometer driving unit that rotationally drives the galvanometer mirror; a galvanometer control unit that controls the galvanometer drive unit; a workbench driving unit, which drives the workbench; as well as a workbench control unit, which controls the workbench drive unit, The laser processing device performs processing based on the processing position coordinates of a pre-stored program, and is characterized in that: The table drive unit and the galvanometer drive unit are controlled based on the processing position coordinates corrected based on the offset between the center position of the scanning area and the vertical incident position of the laser. The scanning area is thereby positioned at a position where the laser is incident perpendicularly to the center of the scanning area. The galvanometer mirror is positioned in such a way that the laser is incident on the corrected processing position coordinates.

2. The laser processing device according to claim 1, wherein The test process is performed by moving the focal position of the Fθ lens away from the surface of the test plate by an arbitrary distance in the height direction, thereby obtaining the offset amount. The flat plate is made of a material having no surface irregularities when placed on the table.

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