JP2004358550A - Laser beam machining method and laser beam machining apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining method for enhancing the machining positional accuracy. <P>SOLUTION: The laser beam machining method comprises a step of forming a hole in a surface of a first work by allowing laser beams to be incident on the surface thereof while weaving the laser beam advancing direction by a scanning optical system based on a table storing information to determine a plurality of machining positions to form the hole in the surface of the first work, a step of calculating the deviation between the position of the hole formed in the surface of the first work and the position of the machining point, a step of calculating the correction quantity of the weaving quantity of the laser beam advancing direction by the scanning optical system based on the deviation, and a step of forming a hole in a second work by allowing laser beams to be incident on the surface of the second work while weaving the laser beam advancing direction by the scanning optical system based on the position information which is obtained by correcting the information stored in the table by the correction quantity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser processing method and a laser processing apparatus, and more particularly to a laser processing method and a laser processing apparatus that can correct a position in a processing surface irradiated with a laser beam.
[0002]
[Prior art]
In drilling using a laser beam, a laser processing apparatus including a galvano scanner and an fθ lens is widely used. Each of the galvano scanner and the fθ lens has an optical distortion characteristic (distortion). Due to the distortion of the laser processing apparatus, there is a problem that even if the laser beam is irradiated aiming at a desired position on the processing surface, the laser beam is irradiated to a position deviating from the desired position.
[0003]
Therefore, distortion is corrected (calibration). For example, in Patent Document 1, a region of a processing surface that can be irradiated with a laser by changing the traveling direction of a laser beam with a galvano scanner is cut into a grid-like mesh that is appropriately set for calibration, and is positioned at each grid point. Test processing is performed to form holes by irradiating a laser beam. The position of the hole formed by the test processing deviates from the lattice point which is an ideal processing position because of distortion in a galvano scanner or the like. Next, for each hole, a deviation amount between an ideal machining position when there is no distortion and an actual machining position is calculated. Based on the amount of deviation, the correction amount of the laser irradiation position on the processing surface targeted by the galvano scanner is obtained for each lattice point.
[0004]
[Patent Document 1] Japanese Patent Application Laid-Open No. 10-301052
[Problems to be solved by the invention]
In the technique disclosed in Patent Document 1, since a correction amount is obtained for each lattice point, the lattice point is punched at an accurate position. However, the correction amount for a certain position other than the lattice point needs to be interpolated by using the correction amounts for a plurality of lattice points that are the vertices of the lattice including the position.
[0006]
When the product is processed, since the processing point does not exist on the calibration grid, an error in the processing position that cannot be corrected remains. The accuracy of the processing position cannot be sufficiently increased.
[0007]
An object of the present invention is to provide a laser processing method and a laser processing apparatus with improved processing position accuracy.
[0008]
[Means for Solving the Problems]
According to one aspect of the present invention, (a) a laser is scanned by a scanning optical system based on a table that stores information for determining the positions of a plurality of workpiece points on which holes on the surface of the first workpiece are to be formed. A step of forming a hole in the surface by causing a laser beam to enter the surface of the first workpiece while swinging the beam traveling direction; and (b) formed on the surface of the first workpiece. A step of calculating a deviation amount between the position of the hole and the position of the processing point; and (c) a correction amount of an amount by which the scanning optical system swings the traveling direction of the laser beam based on the deviation amount. And (d) based on the positional information obtained by correcting the information stored in the table with the correction amount obtained in the step (c), while changing the traveling direction of the laser beam by the scanning optical system, A laser beam is incident on the surface of the workpiece 2 A laser processing method comprising a step of forming a hole in the surface of the workpiece the second is provided.
[0009]
According to another aspect of the present invention, the progression of the laser beam emitted from the laser light source based on a holding mechanism that holds the workpiece, a laser light source that emits a laser beam, and a control signal input from the outside. A scanning optical system that forms a hole in the surface by turning a direction and causing a laser beam to enter the surface of the object to be processed held by the holding mechanism, and a hole in the surface of the object to be processed held by the holding mechanism And a control signal based on the first table is sent to the scanning optical system to send a laser beam to the scanning optical system. The amount of deviation between the position of the hole formed on the surface of the workpiece and the position of the workpiece is calculated by the laser beam whose direction of movement is swung based on the control signal, The scanning optical system is A correction amount for the amount of movement of the beam traveling direction is calculated based on the shift amount, and a control signal based on position information obtained by correcting the information stored in the first table with the correction amount is sent to the scanning optical system. Thus, there is provided a laser processing apparatus having a processing control apparatus for causing the scanning optical system to move the traveling direction of the laser beam.
[0010]
By correcting the position in the processing surface irradiated with the laser beam based on the arrangement shape of the processing points where the holes are to be formed, the processing position accuracy can be improved. A laser processing method and a laser processing apparatus with improved processing position accuracy are provided.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic view of a laser processing apparatus according to an embodiment of the present invention. The laser light source 1 emits a pulse laser beam. As the laser light source 1, for example, a harmonic solid-state laser having a wavelength in the ultraviolet region (for example, an Nd: YAG laser that oscillates the third to fifth harmonics) or a carbon dioxide laser having a wavelength in the infrared region can be used.
[0012]
The laser beam emitted from the laser light source 1 is reflected by the folding mirror 2 and enters the galvano scanner 3. The galvano scanner 3 swings the traveling direction of the laser beam in a two-dimensional direction. The laser beam emitted from the galvano scanner 3 is converged by the fθ lens 4 and focused on the surface of the resin substrate 5 that is the object to be processed. A plurality of points to be drilled are defined on the surface of the resin substrate 5. A laser beam is focused on the work point to form a hole.
[0013]
The resin substrate 5 is, for example, a resin layer such as a polyimide film or acrylic in a test process for calibration described in detail later. In this processing performed after calibration, for example, a package substrate formed of an epoxy resin including a glass cloth for BGA (Ball Grid Array) or CSP (Chip Size Package). The size and shape of the resin substrate 5 is, for example, a 10 mm to 50 mm square.
[0014]
The panel 6 is used for holding a plurality of resin substrates 5. The size and shape of a region on the panel 6 (hereinafter referred to as a scanning region) that can be irradiated with the laser beam by changing the traveling direction of the laser beam by the galvano scanner 3 is set to a square of 50 mm square, for example. The figure shows a case where one resin substrate 5 is sized to be included in the scanning region.
[0015]
The panel 6 is placed on the XY stage 7. With the XY stage 7 stopped, the galvano scanner 3 can be operated to irradiate all the processing points with a laser on a certain resin substrate 5 existing in the scanning region, thereby completing the drilling. When the drilling of a certain resin substrate 5 is completed, the XY stage 7 is moved to move the other resin substrate 5 into the scanning region, so that the other resin substrate 5 can be punched.
[0016]
The camera 8 is used for taking an image of the processing surface of the resin substrate 5. The camera 8 includes, for example, a CCD type solid-state imaging device. Image data of the processing surface imaged by the camera 8 is sent to the processing control device 9.
[0017]
The processing control device 9 includes a personal computer, for example. A laser irradiation position information table 9b is secured in the memory 9a of the processing control device 9. The processing control device 9 transmits a control signal based on the laser irradiation position information table 9b to the galvano scanner 3, and controls the galvano scanner 3 so that the traveling direction of the laser beam is swung based on the laser irradiation position information table 9b. To do.
[0018]
The laser irradiation position information table 9b stores information on a position in the processing surface (hereinafter referred to as a laser irradiation position) targeted by the galvano scanner 3 when the processing surface is irradiated with laser. As will be described in detail later, when performing test processing for calibration, the laser irradiation position information table 9b stores information on the position of the processing point (position in the processing surface where the hole is to be formed). Is done. When performing this processing, the laser irradiation position information table 9b stores, for example, information on the position of the processing point and the correction value obtained by calibration.
[0019]
As will be described in detail later, the processing control device 9 calculates the correction amount of the laser irradiation position based on the image data of the processing surface photographed by the camera 8 and the position information of the processing point. The processing control device 9 also controls the amount of movement of the XY stage 7.
[0020]
In general, the galvano scanner and the fθ lens each have optical distortion characteristics (distortion). FIG. 5A schematically shows a pincushion type distortion that a galvano scanner normally has. Even if the laser beam incident on the galvano scanner is emitted so that a point on the side of the square 20a is irradiated, the sides of the pincushion-shaped figure 21a in which a pair of parallel sides of the square 20a are distorted due to distortion The top spot will be illuminated.
[0021]
FIG. 5B schematically shows a barrel-shaped distortion that an fθ lens normally has. A square 20b shows a certain square image formed by an ideal fθ lens having no distortion. However, this square image by the fθ lens having distortion is distorted into a barrel shape like the figure 21b.
[0022]
Therefore, the optical system including the galvano scanner 3 and the fθ lens 4 included in the laser processing apparatus shown in FIG. 1 has a distortion characteristic in which the distortions of the galvano scanner 3 and the fθ lens 4 are combined. Even if the galvano scanner 3 moves the laser beam aiming at a desired position in the processing surface, there is a problem that the laser beam emitted from the fθ lens 4 is irradiated to a position deviating from the desired position. The accuracy of the processing position cannot be increased, leading to product quality degradation.
[0023]
Therefore, it is necessary to perform distortion correction (calibration) prior to the main processing for processing the product. In the present embodiment, test processing is performed and calibration is performed before the main processing.
[0024]
With reference to FIGS. 2A and 2B, a calibration method will be described. 2A is a plan view of the resin substrate 5 held on the panel 6 as seen from the fθ lens 4 side shown in FIG.
[0025]
The scanning region 17 indicates a region on the surface of the panel 6 where the laser beam can be irradiated by changing the traveling direction of the laser beam with a galvano scanner. An XY coordinate system is set in the scanning area 17.
[0026]
The resin substrate 5 having a plurality of processing points 15 defined on the surface is aligned with a predetermined position in the scanning region 17. For example, when processing a rectangular resin substrate, the center of the resin substrate (intersection of diagonal lines) is positioned on the central axis of the fθ lens, and a side of the resin substrate is parallel to the X axis. The other side orthogonal to a certain side is made parallel to the Y axis.
[0027]
The position of each processing point 15 can be indicated using XY coordinates set in the scanning region 17. In the laser irradiation position information table used for test processing for calibration, XY coordinate values indicating the position of each processing point 15 are stored. That is, in the test processing, the resin substrate 5 is irradiated with a pulsed laser beam while moving the traveling direction of the laser beam aiming at the position of each processing point 15 with a galvano scanner. Holes 16 are formed for all the processing points 15 on the resin substrate 5.
[0028]
As shown in the drawing, the position of each hole 16 formed by the test processing is shifted from the position of each processing point 15 where a hole is to be formed due to distortion of the galvano scanner and the fθ lens. The figure schematically shows how the holes 16 are displaced. The direction and distance of the deviation are considered to vary depending on the arrangement shape of the processing points, the galvano scanner used for processing, and the fθ lens.
[0029]
Next, the processing surface is imaged by the camera 8 shown in FIG. 1, and image data of the processing surface is transmitted to the processing control device 9. The processing control device 9 calculates the XY coordinates of each hole 16 based on this image data, and calculates the amount of deviation between the XY coordinates of each hole 16 and the XY coordinates of each processing point 15 corresponding to each hole 16. .
[0030]
Further, the processing control device 9 calculates a correction amount of the laser irradiation position based on the deviation amount. The correction amount is obtained for each machining point 15 as a correction value ΔX related to the X coordinate and a correction value ΔY related to the Y coordinate. Based on the correction value of the laser irradiation position, the processing control device 9 creates a laser irradiation position information table used for the main processing.
[0031]
The corrected coordinates of the laser irradiation position are expressed as (X + ΔX, Y + ΔY). By irradiating the laser at the corrected laser irradiation position (X + ΔX, Y + ΔY), the laser can be irradiated at a desired position (X, Y).
[0032]
FIG. 2B shows an example of a format of a laser irradiation position information table used for the main processing. Each row corresponds to one workpiece point. The case where the number of points to be processed is N is illustrated. The first column is the X coordinate value of the position where the hole is to be formed, and the second column is the Y coordinate value of the position where the hole is to be formed. The third column is a correction value related to the X coordinate, and the fourth column is a correction value related to the Y coordinate. In addition, illustration of the 4th to N-1th lines is omitted.
[0033]
As described above, by performing calibration according to the arrangement shape of the workpiece points to be actually processed, correction is performed so that the corrected processing position becomes a desired position where the hole is to be formed. Can be improved. The processing position error of about 10 μm remains in the conventional method, but according to the method of this embodiment, it can be reduced to 5 μm or less.
[0034]
Note that the laser irradiation position information table used for the main processing does not have to have a format for storing the position of the processing point and the correction value. The corrected laser irradiation position coordinates (X + ΔX, Y + ΔY) after adding the coordinates of the workpiece point and the correction value may be stored.
[0035]
The laser irradiation position may be expressed using other than XY coordinates. For example, the galvano scanner may be represented by an angle at which the traveling direction of the laser beam is shaken.
[0036]
Next, the main processing steps will be described with reference to FIG. In this processing, holes are made in a plurality of resin substrates on the panel.
[0037]
A plurality of resin substrates 5 are arranged in a matrix on the surface of the panel 6. Every resin substrate 5 has the same size and shape as the resin substrate 5 used for the test processing. Moreover, a hole is formed in any resin substrate 5 with the same arrangement shape as the arrangement shape of the to-be-processed point of the resin substrate 5 which performed the test process. For the sake of explanation, the suffixes a and b are attached to the two resin substrates 5. The resin substrate 5a is aligned at the same position as in the test processing.
[0038]
Based on the post-calibration laser irradiation position information table, each processing point 15a is irradiated with the laser beam while changing the traveling direction of the laser beam with a galvano scanner, and holes are formed in all the processing points of the resin substrate 5a. . Since laser irradiation is performed aiming at the laser irradiation position after calibration, drilling is performed at a desired position on the resin substrate 5a.
[0039]
After the processing of the resin substrate 5a is completed, the XY stage is moved, the resin substrate 5b is moved into the scanning region 17, and is aligned at the same position as when the resin substrate 5a is processed. Based on the laser irradiation position information table after calibration, the laser beam is irradiated to each processing point 15b while changing the traveling direction of the laser beam with a galvano scanner, and holes are formed in all the processing points of the resin substrate 5b. . Drilling is performed at a desired position on the resin substrate 5b.
[0040]
The same process is performed for the other resin substrates 5, and all the resin substrates are drilled at desired positions.
[0041]
In this manner, all the resin substrates processed by this processing can be punched with high positional accuracy. Since all the resin substrates are punched with the same laser irradiation conditions, it is possible to suppress the quality variation of each product.
[0042]
In the test process and the main process, the size and shape of each resin substrate may not be the same. The arrangement shape of the points to be processed may be the same for each resin substrate. Test processing and main processing may be performed so that the processing points are arranged at the same position in the scanning region.
[0043]
Although the case where each resin substrate is entirely accommodated in the scanning region has been described, even if the entire resin substrate does not fit, it is sufficient that the region where the processing point exists is within the scanning region.
[0044]
In the test processing and the main processing, the case where one resin substrate is accommodated in the scanning region has been described. However, if a plurality of resin substrates are accommodated in the scanning region (for example, when the resin substrate is small), the plurality of resin substrates are accommodated. The entire processing points of the resin substrate may be collectively (that is, regarded as a single arrangement shape), and the test processing and the main processing may be performed. For example, if the main processing can be performed by placing four resin substrates in the scanning region, it is expected that productivity is improved as compared with the case of processing one by one.
[0045]
Even when one resin substrate does not fit in the scanning region (for example, when the resin substrate is large), by dividing the single resin substrate into a plurality of regions having a size that enters the scanning region, Calibration can be performed effectively.
[0046]
For example, let us consider a case where one resin substrate is divided into four, and each divided area fits in the scanning area. Here, numbers 1 to 4 are assigned to the divided areas. Test processing is performed for each of the first to fourth regions, and a laser irradiation position information table for each of the first to fourth regions is created. In this processing, the M-th laser irradiation position information table can be used when processing the M-th region for any resin substrate (M is 1 to 4). In this way, it is possible to perform drilling with high processing position accuracy by aligning the laser irradiation conditions for a plurality of resin substrates.
[0047]
By the way, a package substrate may be formed with a large number of holes at high density. As an example, in a BGA package substrate, in a square area of 13 mm square on the chip mounting surface in a square grid array (square grid pitch is 0.23 mm) extending over 56 rows and 56 columns, 3136 (= 56 × 56) An example of forming holes is given.
[0048]
As the number of points to be processed increases, the time required for calibration by performing test processing increases. It is preferable if there is a method that can suppress an increase in test processing time while maintaining high processing position accuracy.
[0049]
When the points to be processed exist at a high density, it is conceivable that some of the points to be processed are not subjected to the test processing (the test processing is performed by thinning out the processing points). The correction amount of the laser irradiation position of the thinned processing points is obtained by interpolation from the correction amount of the processing points subjected to the test processing. If the processing points exist at a high density and the processing points to be test processed exist near the thinned processing points, the interpolation can be performed with high accuracy.
[0050]
The time required for calibration can be shortened by thinning out the points to be processed and performing test processing. However, if the number of processing points to be thinned out is increased too much, high processing position accuracy is impaired. It is necessary to stop the number of workpieces to be thinned to such an extent that the machining position accuracy can be maintained high.
[0051]
FIG. 4 shows an example of a method for performing test machining by thinning out the machining points when drilling the machining points arranged in a matrix as shown in FIG.
[0052]
The processing points v11 to v35 are defined on the resin substrate 5 in a matrix (in a square lattice pattern). The distance between the processing points closest to each other (the pitch of the square lattice) is, for example, 0.23 mm. Test processing is performed on every other processing point in each row. A processing point where test processing is performed is indicated by a solid line, and a processing point where test processing is not performed is indicated by a broken line.
[0053]
For a test point that has been subjected to test processing, the correction amount of the laser irradiation position is obtained from the deviation between the position of the hole and the position of the process point. The machining point that has not been subjected to the test machining is obtained by interpolating from the correction amount of the machining point that is closest to the machining point and has undergone the test machining. For example, the correction amount of the processing point v12 is obtained by interpolating from the correction amounts of the processing points v11 and v13.
[0054]
In addition, it is possible to simultaneously perform drilling on the processing points having the same arrangement shape on each axis of the multi-axis laser processing apparatus. Calibration may be performed for the galvano scanner and fθ lens unit of each axis.
[0055]
In the embodiment, the case of calibrating a laser processing apparatus including a galvano scanner and an fθ lens has been described. However, a laser processing apparatus having another configuration, for example, a galvano scanner and a collector installed on the laser light source side from the galvano scanner are described. Even a laser processing apparatus having a configuration including an optical lens can be calibrated in the same way as in the embodiment. That is, if a test process for irradiating a workpiece with laser according to the hole shape to be formed is performed, and the correction amount of the laser irradiation position is obtained from the deviation between the position of the hole formed by the test process and the desired hole position Good. By performing the main processing based on the correction amount, it is possible to correct the distortion of the optical system composed of a galvano scanner or the like and perform drilling with high positional accuracy.
[0056]
Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.
[0057]
【The invention's effect】
By correcting the position in the processing surface irradiated with the laser beam based on the arrangement shape of the processing points where the holes are to be formed, the processing position accuracy can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic view of a laser processing apparatus according to an embodiment of the present invention.
FIG. 2A is a plan view of a resin substrate, and FIG. 2B is an example of a format of a laser irradiation position information table.
FIG. 3 is a plan view of a plurality of resin substrates arranged on a panel.
FIG. 4 is a plan view of a resin substrate for explaining a test processing method according to a modification.
FIG. 5A is a diagram schematically showing distortion of a galvano scanner, and FIG. 5B is a diagram schematically showing distortion of an fθ lens.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser light source 2 Folding mirror 3 Galvano scanner 4 f (theta) lens 5 Resin board 6 Panel 7 XY stage 8 Camera 9 Processing control apparatus 9a Memory 9b Laser irradiation position information table 15 Processing point 16 Hole 17 Scanning area

Claims (4)

(A) Based on a table storing information for determining the positions of a plurality of points to be processed in which holes on the surface of the first workpiece are to be formed, the scanning optical system changes the traveling direction of the laser beam while A step of making a laser beam incident on the surface of the first workpiece and forming a hole in the surface;
(B) calculating a deviation amount between the position of the hole formed on the surface of the first workpiece and the position of the workpiece;
(C) calculating a correction amount of an amount by which the scanning optical system swings the traveling direction of the laser beam based on the shift amount;
(D) Based on the positional information obtained by correcting the information stored in the table with the correction amount obtained in the step (c), the second processing is performed while changing the traveling direction of the laser beam by the scanning optical system. A step of causing a laser beam to enter the surface of the object and forming a hole in the surface of the second object to be processed. After step (d)
Based on the position information obtained by correcting the information stored in the table with the correction amount obtained in the step (c), a laser is applied to the surface of the workpiece while the traveling direction of the laser beam is swung by the scanning optical system. The laser processing method according to claim 1, wherein the step of making the beam incident and forming the hole in the surface of the workpiece is repeated once or a plurality of times. A holding mechanism for holding the workpiece;
A laser light source for emitting a laser beam;
Based on a control signal input from the outside, the traveling direction of the laser beam emitted from the laser light source is swung, the laser beam is incident on the surface of the workpiece held by the holding mechanism, and a hole is formed in the surface. A scanning optical system to be formed;
A first table storing information for determining positions of a plurality of processing points to be formed with holes on the surface of the workpiece held by the holding mechanism; and a control signal based on the first table Sending to the scanning optical system, causing the scanning optical system to swing the traveling direction of the laser beam, and the position of the hole formed on the surface of the workpiece by the laser beam whose traveling direction is swung based on the control signal The amount of deviation from the position of the workpiece point is calculated, the correction amount of the amount by which the scanning optical system swings the laser beam traveling direction is calculated based on the amount of deviation, and the information stored in the first table is calculated. A laser processing apparatus, comprising: a processing control device that sends a control signal based on the position information corrected by the correction amount to the scanning optical system and causes the scanning optical system to swing a traveling direction of a laser beam. The processing control device has a second table storing position information obtained by correcting the information stored in the first table with the correction amount, and a control signal based on the second table is transmitted to the scanning optical system. The laser processing apparatus according to claim 3, wherein the laser beam is transmitted to the scanning optical system to cause the scanning optical system to swing a traveling direction of the laser beam.

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