KR20130095680A - Laser processing apparatus and laser processing method - Google Patents

Abstract

PURPOSE: A laser processing device and a laser processing method are provided to form a desired shape hole by mitigating an influence of a telecentric error. CONSTITUTION: A laser processing device comprises a stage (12), a laser light source (20), a beam injector (25), a telecentric fθ lens (26), a focus side transport device (27), and a control device (30). The stage supports a processing object. The laser light source emits a pulse laser beam. The beam injector scans the pulse laser beam emitted from the laser light source. The telecentric fθ lens is arranged on a laser beam route between the stage and the beam injector. The focus side transport device diversifies a height of a focus side of the telecentric fθ lens. The control device controls the laser light source, the beam injector, and the focus side transport device.

Description

LASER PROCESSING APPARATUS AND LASER PROCESSING METHOD}

This application claims priority based on Japanese Patent Application No. 2012-033847 for which it applied on February 20, 2012. The entire contents of which are incorporated herein by reference.

TECHNICAL FIELD The present invention relates to a laser processing apparatus and a laser processing method for performing processing by injecting a laser beam scanned by a beam syringe into a processing object through a telecentric f? Lens.

A laser drill combining a galvano scanner and a telecentric f? Lens is used for drilling a printed board. Since the laser beam is incident vertically at any place within the scannable range, it is possible to form a hole with little variation in shape at the center and the periphery of the scan range.

Japanese Patent Laid-Open No. 2000-301374

Using a telecentric f? Lens, ideally, the laser beam is incident vertically anywhere in the scannable range. By the way, in the vicinity of the periphery of the scannable range, a telecentric error may occur, whereby the incident angle of the laser beam may shift slightly at 90 °. In the case where the hole to be formed is shallow, even if the incident angle of the laser beam is slightly displaced at 90 °, the problem is not surfaced. When the hole to be formed deepens, the center axis of the hole to be formed may be inclined with respect to the substrate surface under the influence of the deviation of the incident angle of the laser beam.

An object of the present invention is to provide a laser processing apparatus and a laser processing method which can reduce the influence of a telecentric error and form a hole having a desired shape.

According to one aspect of the present invention,

A stage supporting the object to be processed,

A laser light source for emitting a pulsed laser beam,

A beam syringe for scanning a pulsed laser beam emitted from the laser light source;

A telecentric fθ lens disposed on a path of a laser beam between the stage and the beam syringe,

A focus plane moving mechanism for changing a height of a focus plane of the telecentric fθ lens with respect to a surface of the object to be supported by the stage;

And a control device for controlling the laser light source, the beam syringe, and the focus surface moving mechanism,

The control device controls the beam syringe and the laser light source to inject a plurality of laser pulses into each of a plurality of processing points defined on the surface of the processing object,

The laser processing apparatus which controls the said focus surface moving mechanism for every shot of the laser pulse which injects into each of the said processing points, and changes the height of the said focus surface is provided.

According to another aspect of the present invention,

A step of injecting a pulsed laser beam into a processing point of the object to be processed via a beam syringe and a telecentric f? Lens to form a recess;

Forming the concave portion and then lowering the focal plane of the telecentric f? Lens;

After lowering the focus plane, a laser processing method is provided which has a step of deepening the concave portion by injecting a laser pulse into the concave portion via the beam syringe and the telecentric f? Lens.

By adjusting the height of the focus plane for each shot of the laser pulse, even when a telecentric error occurs, a hole substantially perpendicular to the surface of the object can be formed.

1 is a schematic view of a laser processing apparatus according to the first embodiment.
In FIG. 2, (2A) is a top view of a process target object, (2B) is sectional drawing of a process target object.
3 is a flowchart of the laser processing method according to the first embodiment.
In FIG. 4, (4A) is sectional drawing of the object to be processed by the method of Example 1, (4B) is sectional drawing of the hole formed by the laser processing method of Example 1. FIG.
5 is a cross-sectional view of the hole formed by the laser processing method according to the comparative example.
6 is a flowchart of the laser processing method according to the second embodiment.
7 is a sectional view of a hole formed by the laser processing method according to the third embodiment.

[Example 1]

1, the schematic of the laser processing apparatus by Example 1 is shown. The stage 12 is supported by the base 10 via the stage moving mechanism 11. On the support surface of the stage 12, a process object 13, such as a printed board, is supported. In general, the posture of the base 10 is determined so that the support surface of the stage 12 and the surface of the object to be processed 13 are horizontal. An xyz rectangular coordinate system is defined in which the two directions perpendicular to the support surface of the stage 12 are perpendicular to each other in the x direction and the y direction, and the normal direction of the support surface is in the z direction. The stage movement mechanism 11 moves the stage 12 and the object to be processed 13 in the x direction and the y direction.

The laser light source 20 emits a pulsed laser beam. As the laser light source 20, a carbon dioxide gas laser, a YAG laser, an excimer laser, etc. are used, for example. The pulsed laser beam emitted from the laser light source 20 passes through the beam expander 21, the mask 22, the lens 23, the bending mirror 24, the beam syringe 25, and the fθ lens 26. It enters into the process object 13.

The beam expander 21 enlarges the beam cross section of the laser beam. The mask 22 shapes the beam cross-sectional shape of the laser beam. The lens 23 collimates the laser beam transmitted through the mask 22. The bending mirror 24 directs the traveling direction of the laser beam downward. The beam syringe 25 scans the laser beam so that the incident point of the laser beam moves in the x direction and the y direction on the surface of the object to be processed 13. For example, a pair of galvano scanners are used for the beam syringe 25.

The fθ lens 26 is disposed on the path of the laser beam between the beam syringe 25 and the stage 12. The fθ lens 26 forms a beam cross-sectional shape at the position of the mask 22 on the surface of the object to be processed 13. The beam syringe 25 and the fθ lens 26 constitute an image telecentric optical system. That is, the chief ray of the laser beam scanned by the beam syringe 25 is perpendicularly incident on the object to be processed 13.

The focus plane moving mechanism 27 raises and lowers the fθ lens 26 with respect to the stage 12 (moves in the z direction). When the fθ lens 26 is moved in the z direction, the height of the focusing surface changes based on the surface of the object to be processed 13. Here, a focus plane means the surface in which the beam cross-sectional shape of the position of the mask 22 forms an image.

The control device 30 controls the laser light source 20, the beam syringe 25, the focus surface moving mechanism 27, and the stage moving mechanism 11.

2A, a plan view of the object to be processed 13 is shown. The surface of the object to be processed 13 is divided into a plurality of scan areas 14. One scan area 14 has a size and a shape that are equal to or within the range that can be scanned by the beam syringe 25 (hereinafter referred to as " scannable range "). On the surface of the object to be processed 13, the coordinates of the plurality of processing points 45 for which holes are to be formed are predetermined. The coordinates of the machining point 45 are registered in the control device 30. In addition, the control apparatus 30 registers the number of shots of the laser pulses incident on one machining point 45 and the pulse energy of the laser pulses corresponding to the respective shots.

2B is a cross-sectional view of the vicinity of one machining point 45 of the object to be processed 13. On the board | substrate 40, such as glass epoxy, the copper pattern 41 of an inner layer is formed. On the board | substrate 40 and the copper pattern 41, the resin film 42 is formed. On the resin film 42, the copper film 43 of a surface layer is formed. On the surface of the object 13, the position of the process point 45 which should form a hole is defined.

3, the flowchart of the laser processing method by Example 1 is shown. In the following description, reference is made to FIG. 1, FIG. 2 (A) and (2B), FIG. 4 (4A) and (4B) as needed. In step SA1, the control apparatus 30 (FIG. 1) controls the stage movement mechanism 11, and arrange | positions the raw scan area 14 (2A of FIG. 2) within a scannable range. In step SA2, the control apparatus 30 controls the focus surface moving mechanism 27 to adjust the height of the focus surface. For example, the focus surface is made to coincide with the surface of the object to be processed 13. The thickness of the object to be processed 13 is registered in advance in the control device 30. For this reason, the control apparatus 30 can calculate the height (position in a z direction) of the surface of the object to be processed 13.

In step SA3, the control apparatus 30 controls the beam syringe 25 and the laser light source 20, and in order to the processing point 45 (2A of FIG. 2) in the scan area 14 one by one. A laser pulse is incident by shot. The pulse width and output power of the laser pulses are registered in advance in the control device 30. However, you may arrange | position a pulse width adjuster on the path | route of the laser beam between the lens 23 and the beam syringe 25 as needed. The pulse width adjuster can be configured by, for example, an acoustooptical device and a beam damper.

4 (A), sectional drawing at the time of the 1st shot laser pulse LP1 injecting into the machining point 45 is shown. The focus surface FS1 coincides with the surface of the object to be processed 13. For this reason, the image 47 of the beam cross-sectional shape in the position of the mask 22 (FIG. 1) is formed in the surface of the object to be processed 13. 4A illustrates a case where a telecentric error has occurred. That is, the center ray of the laser pulse LP1 inclines with respect to the normal line direction of the surface of the to-be-processed object 13. The hole 46 is formed at the position where the laser pulse LP1 is incident.

In step SA4 of FIG. 3, it is determined whether the laser pulse of the number of shots required for a process has entered into each machining point 45 (2A of FIG. 2). Step SA2 and step SA3 are repeated until the number of shots entered reaches the number of shots required for processing.

In FIG. 4 (4B), sectional drawing when the laser pulses LP2-LP4 of 2nd-4th shot enters the process point 45 is shown. Before injecting a laser pulse, the height of each of the focus surfaces FS2 to FS4 of the second to fourth shot laser pulses LP2 to LP4 is determined in step SA2 (FIG. 3). It coincides with the bottom surface of the hole 46 formed by the incidence of the pulse.

The depth of the hole 46 can be calculated | required by performing evaluation experiment on the same laser irradiation conditions previously. The movement amount of the focus surface calculated from the depth of the hole 46 is registered in the control device 30. Each time the second to fourth shot laser pulses LP2 to LP4 are incident, the hole 46 is deepened as indicated by the broken line. For this reason, what is necessary is just to arrange the focus surface FS2-FS4 of the laser shot of a subsequent shot relatively deeper than the focus surface FS1-FS3 of the laser pulse of a previous shot relatively. The movement amount of the focus plane cannot be assumed to be the same between the shots. At the time when the fourth shot laser pulse LP4 is incident, the hole 46 reaches the copper pattern 41 of the inner layer.

Even if the hole 46 is deepened, the center ray of the laser pulses LP2 to LP4 of each shot is incident on the bottom surface of the hole 46 at the same position with respect to the xy plane. For this reason, the hole 46 is excavated in the substantially perpendicular direction with respect to the surface of the to-be-processed object 13.

When the hole 46 is deepened, vignetting of the laser pulses occurs by the copper film 43 on the surface layer. However, since the angle formed between the center ray of the laser pulse and the normal direction of the surface of the workpiece 13 is small, the influence of vignetting is negligible.

In step SA4 of FIG. 3, when it is determined that the laser pulses for the short number of times required for processing are incident, it is determined in step SA5 whether or not the processing of all the scan areas 14 is finished. When the raw scan area 14 remains, the process returns to step SA1 and the control device 30 controls the stage moving mechanism 11 to arrange the raw scan area 14 in the scannable range. When the machining of all the scan areas 14 is finished, the drilling is finished.

5, the cross section of the hole formed by the method by a comparative example is shown. In the method according to the comparative example, the position of the focus plane is fixed and the laser pulses of the first shot to the fourth shot are incident on the object to be processed 13. The center rays of the laser pulses of the first to fourth shots coincide with each other, and the image 47 of the beam cross-sectional shape at the position of the mask 22 is fixed to the surface of the object to be processed 13. For this reason, the hole 46 is dug along the center ray of a laser pulse. When the center ray is inclined from the normal direction of the surface of the object to be processed 13, the hole 46 formed also inclines with respect to the surface. According to the evaluation experiment of the inventor of this application, the inclination of the formed hole 46 was the degree which can be confirmed visually.

By using the laser processing apparatus by Example 1, the hole 46 can be excavated in the substantially perpendicular direction with respect to the surface of the to-be-processed object 13. For this reason, the inclination of the hole 46 can be prevented or reduced.

In Example 1, although the height of the focus surface FS2-FS4 was made into the position of the bottom surface of the hole 46 already formed, as shown to (4B) of FIG. 4, it is necessary to exactly match. There is no. As an example, the value obtained by dividing the depth (the depth from the surface of the copper film 43 in the surface layer to the top surface of the copper pattern 41 in the inner layer) of the hole 46 finally formed is equal to the number of shots required for processing. It is good also as a movement distance of a focus surface.

Moreover, in Example 1, although the example which injects four shot laser pulses into one machining point 45 ((4A) and (4B) of FIG. 4) was shown, it makes incident into one machining point 45. The number of shots is not limited to four shots. The number of shots required for processing depends on the material and thickness of the object to be processed 13. The above-described first embodiment for moving the focus plane is effective when a plurality of shot laser pulses are incident on one machining point 45.

[Example 2]

6, the flowchart of the laser processing method by Example 2 is shown. Hereinafter, the difference with Example 1 is demonstrated and description is abbreviate | omitted about the same structure and process. In Example 1, after the process of one scan area 14 was complete | finished, the scan area 14 which should be processed next was processed. In Example 2, the 1st shot laser pulse is made to enter into all the scanning areas 14. As shown in FIG. After the incident of the 1st shot laser pulse is complete with respect to all the scan areas 14, the incident of the next shot laser pulse is performed with respect to all the scan areas 14. As shown in FIG.

First, in step SB1, the short number is initially set. Specifically, the short number is "1". In step SB2, the height of the focus surface is adjusted. In the case of performing the first shot, as shown in Fig. 4A, the height of the focus surface FS1 coincides with the surface of the object to be processed.

In step SB3, the scan area 14 in which incidence of the first shot laser pulse is not placed is arranged in the scannable range. In step SB4, the 1st shot laser pulse is made to enter into the process point in the scan area 14 arrange | positioned in a scannable range in order. In step SB5, it is determined whether or not the incidence of the first shot laser pulses to all the scan areas 14 has ended. In the case where the non-completed scan area 14 remains, the process returns to step SB3 to perform the process of the non-completed scan area 14.

When the incident of the 1st shot laser pulse to all the scan areas 14 is complete | finished, it is determined in step SB6 whether the incidence of the required number of shots was complete | finished. When the number of incident shots is smaller than the required shot number, the shot number is updated in step SB7, and then the flow returns to step SB2. In the process from step SB2 to step SB5, the next one shot of laser pulses is incident on all the processing points 45 of all the scan areas 14. In step SB7, "1" is specifically added to the short number.

In step SB6, when it is determined that incidence of the required number of shots is finished, the laser processing is terminated.

Also in Example 2, the height of a focus surface is adjusted for every shot in step SB2. For this reason, similarly to Example 1, the hole which is substantially perpendicular to the surface of the to-be-processed object 13 can be formed.

[Example 3]

7 is a sectional view of a hole processed by the laser processing method according to the third embodiment. Hereinafter, the difference with Example 1 is demonstrated and description is abbreviate | omitted about the same structure and process. In Example 1, as shown in Fig. 4B, the focusing surface is lowered for each shot of the laser pulse, but it is not necessary to necessarily lower the focusing surface for each shot.

As shown in FIG. 7, in Example 3, when making the 1st shot and the 2nd shot laser pulse LP1, LP2 enter, the focus surface FS1 is made to match the surface of the process target object 13. As shown in FIG. When the third and fourth shots of the laser pulses LP3 and LP4 are incident, the focus surface FS3 is matched to the bottom surface of the hole 46 after the irradiation of the second shot laser pulse LP2.

The center rays of the second and fourth shot laser pulses LP2 and LP4 reach the bottom surface of the hole 46 at positions slightly shifted from the incidence positions of the center rays of the first shot laser pulse LP1. . However, the position where the center ray of the third shot laser pulse LP3 is incident on the bottom surface of the hole 46 coincides with the incident position of the center ray of the first shot laser pulse LP1. For this reason, the grade of the inclination of the hole 46 can be reduced compared with the case where the focus surface is fixed and processed on the surface of the object 13 to be processed.

More generally, by lowering the focus surface at least once between the first shot and the last shot, the degree of inclination of the hole can be reduced as compared with the case where the focus surface is fixed and processed.

Although the present invention has been described in accordance with the above embodiments, the present invention is not limited thereto. For example, it will be apparent to those skilled in the art that various changes, improvements, combinations, and the like are possible.

10 expectations
11 stage moving mechanism
12 stage
13 Objects to be processed
14 scan areas
20 laser light sources
21 beam expander
22 masks
23 lens
24 bending mirror
25 beam syringe
26 fθ lens
27 focal plane shifting mechanism
30 control unit
40 substrates
41 inner layer copper pattern
42 resin film
43 Surface Copper Film
45 processing points
46 holes
47 Image of beam cross-sectional shape at mask position

Claims (7)

A stage supporting the object to be processed,
A laser light source for emitting a pulsed laser beam,
A beam syringe for scanning a pulsed laser beam emitted from the laser light source;
A telecentric fθ lens disposed on a path of a laser beam between the stage and the beam syringe,
A focus plane moving mechanism for changing a height of a focus plane of the telecentric fθ lens with respect to a surface of the object to be supported by the stage;
And a control device for controlling the laser light source, the beam syringe, and the focus surface moving mechanism,
The control device controls the beam syringe and the laser light source to inject a plurality of laser pulses into each of a plurality of processing points defined on the surface of the processing object,
The laser processing apparatus which changes the height of the said focus surface by controlling the said focus surface moving mechanism at least once between the first shot and the last shot of the laser pulse which injects into each of the said processing points. The method according to claim 1,
And the control device controls the focus surface moving mechanism so that the focus surface is lowered for each of the processing points. The method according to claim 2,
The said control apparatus memorize | stores the movement amount of the said focus surface, The laser processing apparatus which makes the distance which moves the said focus surface between shots of the laser pulse which injects into each of the said processing points the same as the said moving amount stored. . The method according to any one of claims 1 to 3,
On the surface of the said process object, the several scanning area which has the magnitude | size which can be injected by the said beam syringe is defined,
The control device includes:
Placing one of the scan areas within the scanable range injectable with the beam syringe, and injecting a laser pulse into the plurality of processing points of the scan area disposed within the scanable range by one shot;
Thereafter, the focus surface is lowered,
And after lowering the focus plane, a laser pulse of a next shot is incident on the plurality of processing points in the scan area arranged in the scanable range. The method of claim 4,
The control device includes:
A process of injecting laser pulses into the plurality of processing points in the scan area one by one in sequence for the plurality of scan areas,
Thereafter, the focus surface is lowered,
The laser processing apparatus which performs the process which injects the next shot laser pulse one by one shot one by one to the said several processing points in the said scan area in order, after lowering the said focus surface. A step of injecting a pulsed laser beam into a processing point of the object to be processed via a beam syringe and a telecentric f? Lens to form a recess;
Forming the concave portion and then lowering the focal plane of the telecentric f? Lens;
And lowering the concave by injecting a laser pulse into the concave through the beam syringe and the telecentric f? Lens after the focusing surface is lowered. The method of claim 6,
In the step of lowering the focus surface, the focus surface is lowered so that the focus surface coincides with a bottom surface of the concave portion before the focus surface is lowered.

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