JP3605722B2 - Laser drilling method and processing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser drilling method and a processing apparatus that perform drilling by irradiating a workpiece such as a printed wiring board or a ceramic substrate with laser light from a laser oscillator.
[0002]
[Prior art]
With the downsizing and high-density mounting of electronic devices, printed wiring boards are required to have high density. For example, what is called an interposer is known as a printed wiring board for mounting and packaging an LSI chip. For such connection between the LSI chip and the interposer, the wire bonding method has heretofore been the mainstream, but a method called flip chip mounting tends to increase, and the number of pins of the package is also increasing.
[0003]
Along with such a tendency, the interposer is required to drill a large number of via holes with a small diameter and a small pitch.
[0004]
For such drilling, mechanical processing using a mechanical fine drill or exposure (photo via) method has been mainstream, but recently, laser light has begun to be used. The drilling apparatus using laser light is superior in that it can cope with the processing speed and the miniaturization of the hole diameter, compared to the machining using a fine drill. As laser light, CO2 is low because of its low price and running cost. ₂ Lasers and harmonic solid-state lasers are generally used.
[0005]
[Problems to be solved by the invention]
In a conventional laser drilling apparatus, a laser beam from a laser oscillator is guided to a scanning optical system including a biaxial galvanometer mirror called an XY scanner or a galvanometer scanner via an optical path including a reflection mirror. Drilling is performed by irradiating a printed wiring board through a processing lens by oscillating a laser beam with this scanning optical system (see, for example, JP-A-10-58178). That is, since the positions of the holes to be drilled in the printed wiring board are determined in advance, the holes are formed one by one by controlling the scanning optical system based on the positional information of these holes.
[0006]
However, in the drilling process one by one using the scanning optical system by the XY scanner or the galvano scanner, the processing time becomes longer in proportion to the increase in the number of holes in the printed wiring board. Incidentally, since the response of the galvano scanner is about 500 pps, it is difficult to drill more than 500 holes per second. For example, if holes with a diameter of 50 μm are arranged at a pitch of 0.2 mm on a square package substrate having a side of 10 mm, there are 2500 holes. In this case, even if 500 holes are drilled per second, a processing time of 2500/500 = 5 sec is required.
[0007]
Then, the subject of this invention is providing the laser drilling method which can perform many drilling in a short time compared with the laser drilling method until now.
[0008]
Another object of the present invention is to provide a laser drilling method capable of arbitrarily selecting a machining pattern for a workpiece.
[0009]
Still another object of the present invention is to provide a laser drilling apparatus suitable for the above processing method.
[0010]
[Means for Solving the Problems]
According to the present invention, in a laser drilling method in which a laser beam from a laser oscillator is irradiated to a workpiece through a mask having a predetermined mask pattern, the laser beam has a linear cross-sectional shape. Converted into light, the irradiation position of the linear laser light is fixed, By arranging an imaging lens between the mask and the workpiece, the projection ratio of the mask pattern to the workpiece can be set. The mask and the member to be processed are arranged so that the mask passes through the irradiation position of the laser beam. In opposite directions The mask is scanned with the linear laser light by moving in synchronism and making the moving direction a direction perpendicular to the extending direction of the linear laser light. There is provided a laser drilling method characterized in that a hole defined by the mask pattern is formed in a workpiece.
[0012]
In the laser drilling method, the movement amount of the mask or the workpiece may be detected, and the oscillation operation of the laser oscillator may be controlled according to the detected movement amount.
[0016]
According to the present invention, furthermore, in a laser drilling apparatus for performing drilling by irradiating a workpiece with a laser beam from a laser oscillator through a mask having a predetermined mask pattern, the laser beam has a linear cross-sectional shape. An optical system for converting into laser light, and a drive mechanism for moving the mask and the workpiece to be synchronized, the irradiation position of the linear laser light from the optical system is fixed; An imaging lens is disposed between the mask and the workpiece, and the projection ratio of the mask pattern to the workpiece can be set by the imaging lens. The drive mechanism moves the mask and the member to be processed so that the mask passes through the irradiation position of the laser beam. Synchronized in opposite directions The mask is scanned with the linear laser beam by moving the moving direction to a direction perpendicular to the extending direction of the linear laser beam, and as a result, the workpiece A laser drilling apparatus characterized in that the drilling defined by the mask pattern is performed.
[0017]
The laser drilling apparatus further includes a position detector that detects the amount of movement of the workpiece, and a controller that controls the oscillation operation of the laser oscillator based on the amount of movement detected by the position detector. You may make it prepare.
[0018]
In this laser drilling apparatus, a position detector for detecting the movement amount of the mask is provided instead of the position detector for detecting the movement amount of the workpiece, and based on the movement amount detected by the position detector. And a controller for controlling the oscillation operation of the laser oscillator.
[0021]
The optical system can be realized by a homogenizer.
[0022]
The optical system also includes a uniform optical system that uniformizes an energy density related to a cross section of the laser light from the laser oscillator, and a cylindrical lens that converts the cross sectional shape of the laser light from the uniform optical system into a linear shape. But it ’s okay.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of a laser drilling apparatus according to the present invention will be described with reference to FIG. Here, a laser drilling apparatus that performs drilling by irradiating a printed wiring board (member to be processed) 12 with a pulsed laser beam from the laser oscillator 10 through a mask 11 having a predetermined mask pattern will be described.
[0025]
The laser beam from the laser oscillator 10 is made uniform in energy density with respect to its cross section by the uniform optical system 13. Here, the energy density related to the cross section is as follows. The laser light from the laser oscillator 10 usually has a circular cross-sectional shape. In this case, the energy density distribution regarding the cross section is close to the Gaussian distribution, with the energy density being higher at the center. The uniform optical system 13 is for making the laser beam having such an energy density distribution have the same energy density in any part of the cross section.
[0026]
To give a simple example of the uniform optical system 13, by enlarging the cross-sectional shape of the laser light from the laser oscillator 10 with an optical lens and passing it through a mask, only the portion where the energy density is high and the energy density is flat is obtained. What is taken out is known. Another example is a bundle fiber consisting of a combination of multiple optical fibers. The cross-sectional shape of the laser light from the laser oscillator 10 is enlarged by an optical lens and then incident on the bundle fiber. Then, the bundle fiber emits laser light having a uniform energy density distribution. As another example, a kaleidoscope called a kaleidoscope is known which uses the principle of so-called kaleidoscope.
[0027]
In any case, the laser beam converted so as to have a uniform energy density distribution by the uniform optical system 13 enters the cylindrical lens 15 via the reflection mirror 14. The cylindrical lens 15 is for converting the cross-sectional shape of the laser light from the uniform optical system 13 into a linear cross-sectional shape.
[0028]
Referring to FIG. 2, the laser beam from uniform optical system 13 has a circular cross section, and has a beam profile as shown in FIG. The beam profile is a waveform in which a constant energy value is sustained when the laser beam is observed with respect to its cross-sectional shape. Here, the beam profile is trapezoidal. By using the cylindrical lens 15, a laser beam having a circular cross section having a trapezoidal beam profile can be shaped into a laser beam having a linear cross sectional shape as shown in FIG. The cylindrical lens 15 includes a width cylindrical lens 15-1 that defines the width of the laser beam having a cross-sectional line shape, and a length cylindrical lens 15-2 that defines the length of the laser beam having a cross-section line shape. According to such a cylindrical lens 15, it is possible to obtain a laser beam having a cross-sectional line shape having a width of 1/10 (mm) to several (mm) and a length of several (cm).
[0029]
The laser oscillator 10, the uniform optical system 13, and the cylindrical lens 15 are placed in a fixed state. In other words, the irradiation position of the laser beam having a cross-sectional line shape from the cylindrical lens 15 is fixed.
[0030]
FIG. 3A shows a cross-sectional shape of a laser beam shaped into a linear shape. The size in the longitudinal direction of the cross section of the laser beam is set to be slightly larger than the size in the width direction of the mask 11 shown in FIG. The mask 11 has a mask pattern composed of a large number of holes that define a processing pattern for the printed wiring board 12. This mask pattern is not limited to a pattern in which a large number of holes 11a are formed in an N × N matrix, and a pattern in which a large number of holes 11a are randomly formed as shown in FIG. . This means that various drilling patterns can be selected.
[0031]
The imaging lens 16 is for setting the projection ratio (reduction ratio) of the mask pattern with respect to the printed wiring board 12. FIG. 1 shows a case where the projection ratio is 1: 1. On the other hand, the printed wiring board 12 is mounted on a work stage 17 that is movable with respect to the X axis and the Y axis. In particular, the present embodiment is characterized in that a mask stage (not shown) that can be moved by mounting a mask and the work stage 17 can be driven synchronously. The work stage 17 can be moved in the X-axis direction and the Y-axis direction within the same horizontal plane by the work stage drive mechanism 25. In this embodiment, the mask stage can be moved in the X-axis direction by the mask stage driving mechanism 26.
[0032]
At the time of drilling, the mask stage drive mechanism 26 and the work stage drive mechanism 25 are synchronously controlled by a control device (not shown). Specifically, the movement of the mask 11 by the mask stage driving mechanism 26 and the movement of the printed wiring board 12 by the work stage driving mechanism 25 are controlled so as to move synchronously in the opposite directions. In particular, the mask 11 passes through the irradiation position of the laser light from the cylindrical lens 15, and the movement direction of the mask 11 is set to be a direction perpendicular to the extending direction of the laser light having a cross-sectional line shape. This means that the laser beam having a linear cross section scans the entire surface of the mask 11. Laser light that has passed through each hole of the mask pattern of the mask 11 by such scanning is irradiated onto the printed wiring board 12 through the imaging lens 16. Since the movement of the mask 11 and the movement of the printed wiring board 12 are synchronized in the opposite direction, a large number of holes defined by the mask pattern of the mask 11 are continuously formed in the printed wiring board 12. become.
[0033]
When the projection ratio by the imaging lens 16 is 1: 1, the moving speed of the irradiation pattern of the laser light irradiated to the printed wiring board 12 when the mask 11 is moved is the same as the moving speed of the mask 11. In other words, the moving speed of the laser light irradiation pattern is the same as the scanning speed of the laser light with respect to the mask 11. However, for example, when the mask pattern is reduced and projected onto the printed wiring board 12 at a reduction ratio of 3 to 1, the irradiation pattern of the laser light applied to the printed wiring board 12 with respect to the scanning speed with respect to the mask 11 is reduced. The moving speed is tripled. The control device synchronously controls the mask stage driving mechanism 26 and the work stage driving mechanism 25 in consideration of such a difference in moving speed.
[0034]
Here, depending on the thickness of the resin layer of the printed wiring board 12, predetermined drilling may not be completed by one-time irradiation with pulsed laser light. In this case, for example, when three shots of pulsed laser light are irradiated, the irradiation is performed so that the peak regions as shown in FIG. This may be achieved by slowing the moving speed of the stage so that a plurality of shots of pulsed laser light having a cross-sectional line shape hit one hole. In this case, it is preferable that the holes 11a formed of a plurality of rows forming the mask pattern have the same pitch in each row, and masking is performed as necessary. Masking will be described later.
[0035]
In addition, the range of a large number of holes formed in the printed wiring board 12 by the above operation may be limited depending on the projection ratio of the imaging lens 16. In such a case, this range is a square area with a side of about several centimeters. On the other hand, as shown in FIG. 4, the drilling process according to the present embodiment is usually performed for each processing area on the multi-sided printed wiring board 12 in which a plurality of processing areas 12-1 are partitioned. Although drilling is performed on one processing region 12-1 by the above-described operation, processing for the next processing region cannot be performed unless the printed wiring board 12 is moved. For this reason, the printed wiring board 12 is driven by the work stage 17 and moved to the next processing area. That is, the work stage 17 moves the next processing area directly below the imaging lens 16 when the drilling process for one processing area 12-1 of the printed wiring board 12 is completed. Of course, the drive of the work stage 17 in this case is performed independently of the drive of the mask 11.
[0036]
By the way, it takes a certain time to move the machining area as described above. On the other hand, even if the laser oscillator 10 generates either continuous laser light or pulsed laser light, it is necessary to prevent the laser light from entering the mask 11 during the above movement. . This is achieved by stopping the oscillation of the laser oscillator 10 during the above movement. As another method, means for bypassing the laser beam may be provided in the optical path upstream of the cylindrical lens 15. Such a bypass means can be realized by making the reflecting mirror 14 rotatable. That is, during the above movement, the reflection mirror 14 is rotated to irradiate the laser beam to another position that is out of the cylindrical lens 15. In this case, it is preferable to arrange the target member at the irradiation position of the laser beam when the reflecting mirror is rotated. The target member is for absorbing the energy of the laser beam. In any case, this operation is called masking, and the same applies to the masking described above.
[0037]
The following explanation regarding the moving speed of the irradiation pattern of the laser beam described above is also applied to the second embodiment described below.
[0038]
A second embodiment of the present invention will be described with reference to FIG. In this embodiment, a homogenizer 20 is disposed between the laser oscillator 10 and the reflection mirror 14 in place of the uniform optical system 13 and the cylindrical lens 15 in the first embodiment shown in FIG. . Other components are the same as those of the embodiment of FIG. The homogenizer 20 has both the functions of the uniform optical system 13 and the cylindrical lens 15 described in the first embodiment. This is also well known, but can be simply described with reference to FIGS. explain.
[0039]
The homogenizer 20 includes, for example, two array lens sets 21 and 22 and a lens system 23 including four focusing lenses. As shown in FIG. 6, the array lens set 21 includes a plurality of cylindrical lenses 21A and 21B that are combined so as to extend in parallel with each other so that the convex surfaces thereof face each other. Arranged. Similarly, as shown in FIG. 7, the array lens set 22 has a plurality of cylindrical lenses 22A and 22B combined so as to extend in parallel with each other so that the convex surfaces thereof face each other. It is arranged and placed. FIG. 7 shows the state shown in FIG. 6 in a state where it is rotated 90 degrees with respect to the axial direction. Therefore, the extending direction of the cylindrical lenses of the array lens set 21 and the extending direction of the cylindrical lenses of the array lens set 22 are combined in a form that intersects at right angles.
[0040]
In any case, the homogenizer 20 has the function of uniformizing the energy density distribution with respect to the cross section by the two array lens sets 21 and 22 having the above-described configuration and the lens system 23 including four focusing lenses. In addition, it can have a function of converting a laser beam having a circular cross section into a laser beam having a cross sectional line shape.
[0041]
Since the operations related to drilling are exactly the same as those in the first embodiment, description thereof is omitted.
[0042]
Next, a third embodiment of the present invention will be described with reference to FIG. This embodiment is different from the first embodiment in the following points. In the first embodiment, the oscillation operation of the laser oscillator 10 is continuous. On the other hand, in the third embodiment, the oscillation operation of the laser oscillator 10 is controlled in accordance with the amount of movement of the printed wiring board 12, that is, the position. Specifically, the printed wiring board 12 is moved at a constant speed. The controller 30 outputs an oscillation trigger signal to the laser oscillator 10 when the printed wiring board 12 reaches a predetermined position based on the detection signal of the position detector 31. When receiving the oscillation trigger signal, the laser oscillator 10 is activated to generate laser light. This means that the laser oscillator 10 oscillates in synchronization with the movement of the printed wiring board 12 (work stage 17).
[0043]
For this reason, in this embodiment, as a means for detecting the amount of movement of the printed wiring board 12, that is, the position, a position detector 31 for detecting the amount of movement of the work stage 17 and the amount of movement detected by the position detector 31 are used. A controller 30 that controls the oscillation operation of the laser oscillator 10 is provided. Other configurations and operations are the same as those in the first embodiment.
[0044]
The position detector 31 can be realized, for example, in combination with a linear encoder that directly detects the movement of the work stage 17. This is because this kind of work stage drive mechanism 25 is often realized by a linear drive mechanism using the principle of a linear motor, and in this case, a linear encoder is often installed for position control. is there. The linear encoder outputs a pulse each time the work stage 17 moves by a minute unit distance (for example, 1 μm). The position detector 31 counts this pulse and outputs the count value to the controller 30.
[0045]
On the other hand, the work stage drive mechanism 25 may be realized by a mechanism that converts the rotary motion of the servo motor into a linear motion. In this case, the position detector 31 is realized by a rotary encoder that detects the rotation amount of the servo motor. The rotary encoder also outputs a pulse each time the servo motor rotates by a minute unit angle. The position detector 31 counts this pulse and outputs the count value to the controller 30.
[0046]
The position detector 31 as described above is an example, and it goes without saying that another well-known position detector that does not depend on a combination with a linear encoder or a rotary encoder may be used.
[0047]
The controller 30 determines the amount of movement of the work stage 17 from the count value from the position detector 31, that is, the current position of the work stage 17. In this embodiment, the controller 30 is shown as a control unit different from the control device for synchronously controlling the mask stage driving mechanism 26 and the work stage driving mechanism 25 described above, but these are one control. Needless to say, this can be realized by an apparatus.
[0048]
Since the mask imaging method is adopted in this embodiment as well as the first embodiment, the mask stage and the work stage 17 are the same when the projection ratio (reduction ratio) is 1: 1 as described above. Advance by distance. For example, if the ratio of the mask dimension to the workpiece (printed wiring board 12) dimension is 2: 1, the mask stage travels twice as long as the work stage.
[0049]
The mask 11 moves in the opposite direction in synchronization with the movement of the printed wiring board 12. This is because the mask pattern of the mask 11 is reversed on the printed wiring board 12 by the imaging lens 16 as described above.
[0050]
When the work stage 17 starts to move, pulses are output from the linear encoder or rotary encoder at regular intervals (for example, every 1 μm) and counted up by the position detector 31.
[0051]
For example, when holes are made in the printed wiring board 12 at a pitch of 1 mm, the controller 30 outputs an oscillation trigger signal to the laser oscillator 10 when the count value reaches 1000 pieces (1000 μm). The hole pitch is input in advance from the parameter setting unit 32 as a processing parameter before processing.
[0052]
The work stage 17 does not repeat the step operation, that is, the operation of moving and stopping at a constant distance (distance corresponding to the pitch), but moving at a constant speed. Then, when the portion of the printed wiring board 12 to be punched reaches a predetermined position, the laser beam is irradiated.
[0053]
Since the operation as the laser drilling apparatus is the same as that of the first embodiment, description thereof is omitted.
[0054]
Next, a fourth embodiment of the present invention will be described with reference to FIG. This embodiment is different from the third embodiment in the following points. In this embodiment, the oscillation operation of the laser oscillator 10 is controlled in accordance with the amount of movement of the mask 11, that is, the position. Specifically, the mask 11 is moved at a constant speed in synchronization with the movement of the printed wiring board 12. The controller 30 outputs an oscillation trigger signal to the laser oscillator 10 when the mask 11 reaches a predetermined position based on the detection signal of the position detector 35. When receiving the oscillation trigger signal, the laser oscillator 10 is activated to generate laser light. This means that the laser oscillator 10 oscillates in synchronization with the movement of the mask 11 (mask stage).
[0055]
For this reason, in this embodiment, as a means for detecting the movement amount of the mask 11, that is, the position, a position detector 35 for detecting the movement amount of the mask stage and a laser based on the movement amount detected by the position detector 35 A controller 30 that controls the oscillation operation of the oscillator 10 is provided. The configuration and operation other than the position detector 35 are the same as those of the third embodiment, but the same position detector 35 as the position detector 31 can be used.
[0056]
That is, the only difference between the third embodiment and the fourth embodiment is whether the object to synchronize the oscillation of the laser oscillator 10 is the work stage 17 or the mask stage. As described above, when the projection ratio (reduction ratio) is 1: 1, the mask stage and the work stage 17 advance by the same distance. Further, for example, if the ratio of the mask dimension to the dimension of the processing area 12-1 is 2: 1, the mask stage travels twice as long as the work stage. Therefore, the controller 30 in the present embodiment outputs the oscillation trigger signal to the laser oscillator 10 in consideration of the above projection ratio.
[0057]
Since the operation as the laser drilling apparatus is the same as that of the third embodiment, description thereof is omitted.
[0058]
In both the third and fourth embodiments, the laser oscillator 10 receives the oscillation trigger signal and oscillates to generate laser light. However, a time delay from the reception of the oscillation trigger signal to the oscillation is obtained. Exists. This time delay is, for example, 1 μsec. It is assumed that the oscillation frequency of the laser oscillator 10 is 150 Hz and the work stage 17 is moving at a constant speed of 150 mm / sec. In this case, the time delay of 1 μsec causes a positional shift of 0.15 μm at the laser light irradiation position. However, since this value is very small, there is no problem. When the positional deviation becomes a problem, the positional deviation can be corrected by giving an offset to the machining parameter set by the parameter setting unit 32.
[0059]
The machining parameters set by the parameter setting unit 32 are not limited to the pitch of holes to be machined, and the positions of the holes, that is, the coordinate positions on the two-dimensional plane based on the X axis and Y axis may be input.
[0060]
The hole pitch is preferably a constant value. This is because if the hole pitch is constant, the oscillation frequency of the laser oscillator 10 is constant, and the intensity variation of the laser output is reduced. However, even if the pitch of the holes is not constant, the present invention exhibits its effect sufficiently.
[0061]
Depending on the material of the printed wiring board 12, there may be a case where the laser beam irradiation has to be performed a plurality of times. In this case, the scan by moving the mask 11 and the printed wiring board 12 may be repeated for a plurality of shots.
[0062]
In any of the third and fourth embodiments, the homogenizer 20 described in the second embodiment may be used in place of the uniform optical system 13 and the cylindrical lens 15.
[0063]
In addition, when the dimension of the mask 11 is small with respect to the dimension of the process area | region 12-1 of the printed wiring board 12, it carries out like FIG. In FIG. 11, it is assumed that the dimension L1 of the mask 11 in the scanning direction is the same as the dimension L2 in the scanning direction of the processing region 12-1. Further, it is assumed that the dimension L3 of the mask 11 perpendicular to the scanning direction is ½ of the dimension L4 in the direction perpendicular to the scanning direction of the processing region 12-1. In this case, when the half-drilling process of the machining area 12-1 is completed, the machining area 12-1 is shifted by a predetermined distance in a direction perpendicular to the scanning direction, and the drilling process is performed. In this case, the scanning direction at the time of processing in FIG. 11D is opposite to the scanning direction at the time of processing in FIG. Of course, the pattern of the processed holes is the same.
[0064]
A fifth embodiment of the present invention will be described with reference to FIG. This embodiment is a modification of the third embodiment, and the mask 11 'is fixed. Therefore, a mask stage driving mechanism is not necessary. For this reason, unlike the mask 11 in the above-described embodiment, the mask 11 ′ has a processed hole pattern for one row as shown in FIG. The laser oscillator 10 is oscillated in synchronization with the movement of the printed wiring board 12 (work stage 17). Since the functions of the position detector 31, the controller 30, and the parameter setting unit 32 are the same as those described in the third embodiment, description thereof will be omitted.
[0065]
When the work stage 17 starts to move, pulses are output from the linear encoder or rotary encoder at regular intervals (for example, every 1 μm) and counted up by the position detector 31.
[0066]
For example, when holes are made in the printed wiring board 12 at a pitch of 1 mm, the controller 30 outputs an oscillation trigger signal to the laser oscillator 10 when the count value reaches 1000 pieces (1000 μm). The hole pitch is input in advance from the parameter setting unit 32 as a processing parameter before processing.
[0067]
The work stage 17 moves at a constant speed instead of repeating a step operation, that is, an operation of moving a certain distance and stopping. Then, when the portion of the printed wiring board 12 to be punched reaches a predetermined position, the laser beam is irradiated.
[0068]
When the width dimension of the mask 11 ′ is smaller than the width dimension of the processing region 12-1 of the printed wiring board 12, it is as shown in FIG. In FIG. 13, it is assumed that the width dimension L10 of the mask 11 ′ is the same as the width dimension L20 of the processing region 12-1. In this case, when the half-drilling process of the machining area 12-1 is completed, the machining area 12-1 is shifted by a predetermined distance in a direction perpendicular to the scanning direction, and the drilling process is performed. In this case, the scanning direction at the time of processing in FIG. 13D is opposite to the scanning direction at the time of processing in FIG. Of course, the pattern of the processed holes is the same.
[0069]
Also in this embodiment, the homogenizer 20 described in the second embodiment may be used instead of the uniform optical system 13 and the cylindrical lens 15.
[0070]
Incidentally, the adverse effect of fixing the mask 11 'is that the processed hole becomes an ellipse having a long axis in the scanning direction. However, this problem can be ignored if a pulse laser oscillator with a short pulse width is employed. For example, when the moving speed of the work stage 17 is 150 mm / sec and a laser oscillator having a pulse width of 0.2 μsec is employed, the work stage 17 moves only 0.03 μm within the oscillation time. In this case, if the hole diameter is 50 μm, 0.03 μm can be ignored, and the hole shape is regarded as a perfect circle.
[0071]
In any of the embodiments, the laser oscillator 10 includes CO 2. ₂ Laser oscillators, YAG and YLF laser oscillators, the second harmonic (2ω), the third harmonic (3ω), the fourth harmonic (4ω), or an excimer laser oscillator can be used. Further, the member to be processed is not limited to a resin layer such as a printed wiring board, and a hole can be drilled in a material such as a ceramic thin plate used as an insulating material for electrical components such as capacitors and piezoelectric elements. Furthermore, the present invention can also be applied to a case in which drilling is performed by a so-called contact mask method in a state where a mask having a predetermined mask pattern is in contact with a workpiece such as a printed wiring board. In this case, the imaging lens is omitted.
[0072]
【The invention's effect】
As described above, according to the present invention, it is possible to perform a large number of drilling operations in a shorter time than a laser drilling device using a conventional galvano scanner. Moreover, since the mask pattern of the movable mask used in the present invention can arbitrarily set an array of a plurality of holes, flexible drilling can be realized.
[0073]
In addition, according to the drilling apparatus according to the third to fifth embodiments, it is possible to accurately perform drilling at a position to be processed, and the work stage is continuously moved instead of the step moving type. This is a highly productive system.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a laser drilling apparatus according to a first embodiment of the present invention, FIG. 1 (a) is an overall configuration, and FIG. 1 (b) is a diagram of FIG. 1 (a). It is the figure which looked at the structure of the principal part from different angles.
2 is a diagram for explaining the action of converting the cross-sectional shape of the laser light into a linear shape by the uniform optical system and the cylindrical lens shown in FIG. 1, and FIG. 2 (a) is energy related to the cross-section of the laser light; FIG. 2B is a diagram showing a cross-sectional shape of the laser beam converted into a linear shape.
FIG. 3 is a diagram showing a cross-sectional shape (FIG. 3a) of laser light converted into a linear shape and an example of the mask shown in FIG.
FIG. 4 is a view showing an example of a multi-sided printed wiring board which is a processing target of the processing apparatus according to the present invention.
FIGS. 5A and 5B are diagrams showing a configuration of a laser drilling apparatus according to a second embodiment of the present invention, in which FIG. 5A shows the overall configuration and FIG. 5B shows the configuration of FIG. It is the figure which looked at the structure of the principal part from different angles.
6 is a diagram for explaining the configuration of the homogenizer shown in FIG. 5. FIG. 6 (a) shows the configuration of the homogenizer, and FIG. 6 (b) shows one of the configurations shown in FIG. 6 (a). It is the figure which showed the structure of the array lens set.
7 is a diagram showing the configuration of the homogenizer shown in FIG. 6 in a state rotated by 90 degrees with respect to the central axis, FIG. 7 (a) shows the configuration of the homogenizer, and FIG. It is the figure which showed the structure of the other array lens set shown by 7 (a).
8 is a perspective view three-dimensionally showing the configuration of the homogenizer shown in FIG.
FIGS. 9A and 9B are diagrams showing the configuration of a laser drilling apparatus according to a third embodiment of the present invention, FIG. 9A shows the overall configuration, and FIG. 9B shows the configuration of FIG. It is the figure which looked at the structure of the principal part from different angles.
10A and 10B are diagrams showing a configuration of a laser drilling apparatus according to a fourth embodiment of the present invention. FIG. 10A shows the entire configuration, and FIG. 10B shows the configuration of FIG. It is the figure which looked at the structure of the principal part from different angles.
FIG. 11 is a diagram illustrating a relationship among a cross-sectional shape of a laser beam, a mask, and a processing pattern according to a third embodiment.
FIGS. 12A and 12B are diagrams showing the configuration of a laser drilling apparatus according to a fifth embodiment of the present invention, FIG. 12A shows the overall configuration, and FIG. 12B shows the configuration of FIG. It is the figure which looked at the structure of the principal part from different angles.
FIG. 13 is a diagram showing a relationship between a cross-sectional shape (FIG. 13a) of a laser beam, a mask (FIG. 13b), and a processing pattern (FIGS. 13c and d) in the fifth embodiment.
[Explanation of symbols]
11, 11 'mask
12 Printed circuit board
13 Uniform optical system
14 Reflection mirror
15 Cylindrical lens
16 Imaging lens
17 Work stage
20 Homogenizer
25 Work stage drive mechanism
26 Mask stage drive mechanism

Claims (7)

In a laser drilling method for performing drilling by irradiating a workpiece with a laser beam from a laser oscillator through a mask having a predetermined mask pattern,
Converting the laser beam into a laser beam having a linear cross-sectional shape;
The irradiation position of the linear laser beam is fixed,
By arranging an imaging lens between the mask and the workpiece, the projection ratio of the mask pattern to the workpiece can be set ,
The mask and the workpiece are moved in synchronization with each other in opposite directions so that the mask passes through the irradiation position of the laser beam, and the moving direction is perpendicular to the extending direction of the linear laser beam. In this case, the mask is scanned with the linear laser beam, and as a result, a hole defined by the mask pattern is formed in the workpiece. Laser drilling method. 2. The laser drilling method according to claim 1, wherein a movement amount of the mask or the workpiece is detected, and an oscillation operation of the laser oscillator is controlled in accordance with the detected movement amount. Laser drilling method. In a laser drilling apparatus that performs drilling by irradiating a workpiece with a laser beam from a laser oscillator through a mask having a predetermined mask pattern,
An optical system for converting the laser light into laser light having a linear cross-sectional shape;
A drive mechanism for moving the mask and the workpiece in synchronization,
The irradiation position of the linear laser beam from the optical system is fixed,
An imaging lens is disposed between the mask and the workpiece, and the projection ratio of the mask pattern to the workpiece can be set by the imaging lens.
The drive mechanism moves the mask and the workpiece in synchronization with each other in opposite directions so that the mask passes through the irradiation position of the laser light, and moves the movement direction of the linear laser light. By making the direction perpendicular to the extending direction, the mask is scanned with the linear laser beam, and as a result, the hole defined by the mask pattern is formed in the workpiece. Laser drilling apparatus characterized by that. 4. The laser drilling apparatus according to claim 3, wherein the optical system is a homogenizer. 5. The laser drilling apparatus according to claim 3, wherein the optical system includes a uniform optical system that uniformizes an energy density related to a cross section of the laser light from the laser oscillator, and a cross-sectional shape of the laser light from the uniform optical system. And a cylindrical lens for converting the laser beam into a linear shape. 6. The laser drilling apparatus according to claim 3, further comprising a position detector for detecting a movement amount of the workpiece, and the laser oscillator based on the movement amount detected by the position detector. And a controller for controlling the oscillation operation of the laser drilling apparatus. 6. The laser drilling apparatus according to claim 3, further comprising: a position detector that detects a movement amount of the mask; and an oscillation of the laser oscillator based on the movement amount detected by the position detector. A laser drilling apparatus comprising a controller for controlling operation.

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