JP6869623B2 - Laser processing equipment - Google Patents

Description

The present invention relates to a laser processing apparatus.

In a laser processing apparatus for drilling holes in a printed wiring board, a technique of detecting reflected light from an object to be processed to determine a processing state is known. For example, a laser processing apparatus that controls a laser beam from the reflected light intensity of the reflected light emitted from a laser oscillator and reflected by a multilayer substrate to be processed is known (Patent Document 1).

Japanese Unexamined Patent Publication No. 2000-126880

In order to improve the laser processing efficiency, a laser processing apparatus is used in which a laser beam output from a laser oscillator is branched into two and laser processing (two-axis processing) is performed with the two laser beams. When performing biaxial machining, the reflected light must be measured for each of the two laser beams in order to determine the machining state.

An object of the present invention is to provide a laser processing apparatus capable of processing with two laser beams and measuring the intensity of reflected light for each of the two laser beams.

According to one aspect of the invention
A branching / merging optical system that branches and merges a laser beam, in which a laser beam incident on the branching / merging optical system along an incident path to the branching / merging optical system is subjected to a first processing path and a polarization direction according to the polarization direction. The first reflected light and the second reflected light, which are branched into the second processing path and are incident on the branching and merging optical system along the first processing path and the second processing path, respectively, are transferred to the incident path. The branch merging optical system that merging into a measurement path different from that of
A branching element that branches the first reflected light and the second reflected light merged into the measurement path into different paths.
A first photodetector that measures the intensity of the first reflected light branched by the branching element, and
A laser processing apparatus including a second photodetector for measuring the intensity of the second reflected light branched by the branching element is provided.

Machining can be performed with two laser beams, a first machining path and a second machining path. It is possible to measure the intensity of reflected light for each of the two laser beams.

FIG. 1 is a schematic view of a laser processing apparatus according to an embodiment. 2A, 2B, and 2C are cross-sectional views of one work point of the object to be processed before, during, and after processing, respectively. FIG. 3A is a schematic plan view of a part of the object to be processed 50, and FIG. 3B shows the incident of the pulsed laser beam on the object to be processed and the first beam scanner and the second beam scanner (FIG. 1). ) Is a timing chart showing the driving period. FIG. 4 is a flowchart showing a procedure for drilling using the laser machining apparatus according to the embodiment. FIG. 5 is a timing chart showing the incident of the pulsed laser beam on the object to be machined in the laser machining apparatus according to another embodiment, and the driving period of the first beam scanner and the second beam scanner. FIG. 6 is a flowchart showing a procedure for drilling using a laser machining apparatus according to another embodiment.

The laser processing apparatus according to the embodiment will be described with reference to FIGS. 1 to 4.
FIG. 1 is a schematic view of a laser processing apparatus according to an embodiment. The laser light source 10 outputs a pulsed laser beam for processing. For the laser light source 10, for example, a carbon dioxide laser is used.

The pulsed laser beam output from the laser light source 10 is incident on the branching and merging optical system 11 along the incident path Pi. The branching and merging optical system 11 branches the laser beam incident along the incident path Pi into the first processing path P1 and the second processing path P2 toward the object to be processed 50 according to the polarization direction. Further, the first reflected light and the second reflected light that are reflected by the object to be processed 50 and travel in the opposite directions on the first processing path P1 and the second processing path P2 are measured differently from the incident path Pi. Join the path Pm.

The branching and merging optical system 11 includes, for example, a first polarization beam splitter 12, a first polarization optical element 13A, and a second polarization optical element 13B. The first polarization beam splitter 12 transmits the P polarization component of the laser beam incident along the incident path Pi and reflects the S polarization component. The polarization direction of the incident laser beam is adjusted so that the powers of the P-polarized light component and the S-polarized light component are equal. The P polarization component transmitted through the first polarization beam splitter 12 propagates along the first processing path P1, and the S polarization component reflected by the first polarization beam splitter 12 propagates along the second processing path P2. Propagate.

The first polarizing optical element 13A is arranged in the first processing path P1. The laser beam that passes through the first processing path P1 twice in the outward path and the return path rotates its polarization direction by 90 °. As a result, the first reflected light returning from the first processing path P1 is reflected by the first polarizing beam splitter 12. The second polarizing optical element 13B is arranged in the second processing path P2. The laser beam that passes through the second processing path P2 twice in the outward path and the return path rotates its polarization direction by 90 °. As a result, the second reflected light returning from the second processing path P2 passes through the first polarizing beam splitter 12. For the first polarizing optical element 13A and the second polarizing optical element 13B, for example, a 1/4 wave plate can be used.

The first beam scanner 20A and the first condensing lens 22A are arranged in the first processing path P1 between the branching and merging optical system 11 and the processing object 50. Similarly, the second beam scanner 20B and the second condenser lens 22B are arranged in the second processing path P2. A first beam damper 21A and a second beam damper 21B are arranged beside the first processing path P1 and the second processing path P2, respectively.

The object to be processed 50 is held on the stage 45. The stage 45 has a function of moving the object to be processed 50 in two-dimensional directions (x direction and y direction) parallel to the surface (surface to be processed). The object to be processed 50 is, for example, a printed circuit board, and drilling is performed by a laser beam.

The first beam scanner 20A scans the laser beam in the two-dimensional direction. As the first beam scanner 20A, for example, a galvano scanner having a pair of movable mirrors can be used. The scanned laser beam is focused on the surface to be processed of the object to be processed 50 by the first focusing lens 22A. As the first condenser lens 22A, for example, an fθ lens is used. The first beam scanner 20A has a function of deflecting the laser beam toward the first beam damper 21A. When the laser beam is deflected toward the first beam damper 21A, the laser beam does not enter the workpiece 50.

The second beam scanner 20B arranged in the second processing path P2, the second condenser lens 22B, and the second beam damper 21B arranged beside the second processing path P2 are each the first. It has the same functions as the beam scanner 20A, the first condenser lens 22A, and the first beam damper 21A.

The first reflected light propagating in the first processing path P1 in the opposite direction and reflected by the first polarizing beam splitter 12, and propagating in the second processing path P2 in the opposite direction to the first polarizing beam splitter. The second reflected light transmitted through 12 merges with the measurement path Pm. The first reflected light and the second reflected light that have merged with the measurement path Pm are incident on the second polarization beam splitter 30. The second polarization beam splitter 30 has a function as a branching element that branches the first reflected light and the second reflected light into different paths. The first photodetector 31A and the second photodetector 31B are arranged in the two paths after being branched by the second polarization beam splitter 30, respectively. The first reflected light and the second reflected light are incident on the first photodetector 31A and the second photodetector 31B, respectively.

The first photodetector 31A and the second photodetector 31B measure the intensities of the first reflected light and the second reflected light, respectively. The measurement result is input to the control device 40.

The control device 40 controls the output timing and output power of the pulsed laser beam output from the laser light source 10. Further, by controlling the first beam scanner 20A and the second beam scanner 20B, the laser beam propagating in the first processing path P1 and the second processing path P2 is scanned. Further, by controlling the stage 45, the workpiece 50 is moved to a target position.

The storage device 41 stores information required for processing, for example, position information of a plurality of work points on the processing object 50, information for instructing the processing order, laser irradiation conditions, and the like. The laser irradiation conditions include the pulse width, the output power, the number of shots incident on each of the work points, and the like. The control device 40 associates the detection result of the intensity of the reflected light measured by the first photodetector 31A and the second photodetector 31B during the laser processing with each of the processing points in the storage device 41. It has a function to memorize.

The control device 40 determines the laser beam irradiation conditions for each work point according to the intensity of the reflected light for each work point detected by the first photodetector 31A and the second photodetector 31B, respectively. Has the function of The irradiation conditions of the laser beam that propagates through the first processing path P1 and is incident on the processing object 50 and the irradiation conditions of the laser beam that propagates through the second processing path P2 and is incident on the processing object 50 are separate. It is possible to adjust to.

Next, with reference to FIGS. 2A to 2C, the structure of the object to be machined 50 before machining, the structure in the middle of machining, and the structure after machining will be described.

FIG. 2A is a cross-sectional view of a portion of the workpiece 50 before machining near one machining point. The inner layer conductor film 52 is arranged on the inner layer of the dielectric substrate 51 such as glass epoxy. The front surface conductor film 53 is arranged on the surface to be processed of the dielectric substrate 51, and the back surface conductor film 54 is arranged on the back surface.

FIG. 2B is a partial cross-sectional view of the object to be processed 50 after one shot of a pulsed laser beam for processing is incident. The incident of one shot of the pulsed laser beam forms a recess 55 penetrating the surface conductor film 53. A part of the dielectric substrate 51 under the surface conductor film 53 is also removed by laser irradiation, and the recess 55 reaches a position slightly shallower than the upper surface of the inner layer conductor film 52.

FIG. 2C is a partial cross-sectional view of the processed object 50 after processing. A pulsed laser beam having a smaller pulse energy density than that shown in FIG. 2B is incident on one shot or a plurality of shots. As a result, the recess 55 reaches the upper surface of the inner layer conductor film 52, and the inner layer conductor film 52 is exposed.

Depth of the recess 55 formed in one shot due to variations in pulse energy density during processing shown in FIG. 2B, variations in the density of glass fibers in the dielectric substrate 51, variations in the thickness of the surface conductor film 53, and the like. Also varies. The recess 55 may reach the inner layer conductor film 52, exposing a part of the inner layer conductor film 52. When the inner layer conductor film 52 is exposed, the intensity of the reflected light increases. One shot shown in FIG. 2B by measuring the intensity of the first reflected light and the intensity of the second reflected light with the first photodetector 31A and the second photodetector 31B (FIG. 1), respectively. It is possible to obtain information on the processing status such as the depth and size of the recess 55 processed in.

If the inner layer conductor film 52 is already exposed in the first shot processing and the second and subsequent shots are processed under the specified irradiation conditions, the damage to the inner layer conductor film 52 becomes large. In this case, it is preferable to reduce the pulse energy density of the pulsed laser beam after the second shot or reduce the number of shots.

Next, with reference to FIGS. 3A and 3B, the incident of the pulsed laser beam and the procedure for moving the incident position will be described.

FIG. 3A is a schematic plan view of a part of the object to be processed 50. A plurality of scanning regions 61 are defined on the surface to be processed of the object to be processed 50. One scanning area 61 has a size that can be scanned by the first beam scanner 20A and the second beam scanner 20B (FIG. 1). One scanning region 61 is processed by a laser beam propagating in the first processing path P1, and the other scanning region 61 is processed by a laser beam propagating in the second processing path P2.

A plurality of work points 62 are defined inside each of the scanning regions 61. Drilling is performed by injecting a pulsed laser beam into a plurality of work points 62 in order. In this embodiment, first, recesses 55 penetrating the surface conductor film 53 shown in FIG. 2B are formed at all the processed points 62 in one scanning region 61. After that, the laser pulses from the second shot onward are incident on each work point 62 in the same scanning region 61, and the recess 55 is dug as shown in FIG. 2C. The laser pulses from the second shot onward are continuously incident on one work point 62. As described above, the method of making the first shot incident on all the work points 62 and then performing the processing of the second and subsequent shots is called cycle processing.

FIG. 3B is a timing chart showing the incident of the pulsed laser beam on the object to be processed 50 and the driving period of the first beam scanner 20A and the second beam scanner 20B (FIG. 1). During the period T1, the surface conductor film 53 shown in FIG. 2B is processed. In the period T1, the output of the laser pulse LP1 to each of the plurality of work points 62 and the driving of the first beam scanner 20A and the second beam scanner 20B are alternately repeated. The laser pulse LP1 is output after the laser beam incident positions scanned by the first beam scanner 20A and the second beam scanner 20B are set at the work point 62.

During the period T2 and the period T3, the dielectric substrate 51 shown in FIG. 2C is processed. In the period T2, the laser pulse LP2 is incident on each of the plurality of work points 62 one by one. Similarly, during the period T3, the laser pulse LP3 is incident on each of the plurality of work points 62 one by one. FIG. 3B shows an example in which two laser pulses LP2 and LP3 are incident on one work point 62 in the process shown in FIG. 2C. The number of shots incident on one processing point 62 is set to an optimum number depending on the pulse energy density of the pulsed laser beam to be irradiated, the depth to the inner conductor film 52, the material of the dielectric substrate 51, and the like. When only one laser pulse is incident in the process shown in FIG. 2C, the processing of the period T3 shown in FIG. 3B is unnecessary.

Next, a procedure for drilling a hole using the laser machining apparatus according to the present embodiment will be described with reference to FIG.

FIG. 4 is a flowchart showing a procedure for drilling using the laser machining apparatus according to the present embodiment. First, the control device 40 (FIG. 1) controls the first beam scanner 20A and the second beam scanner 20B to determine the incident positions of the laser beams of the first processing path P1 and the second processing path P2. , Settle at the position of the work point 62 (FIG. 3A) to be machined first (step S1). The position of the work point 62 is stored in the storage device 41. When the first beam scanner 20A and the second beam scanner 20B are set, the control device 40 controls the laser light source 10 to output a one-shot pulsed laser beam (step S2). As a result, the recess 55 shown in FIG. 2B is formed.

The intensities of the first reflected light and the second reflected light propagating in the opposite directions in the first processing path P1 and the second processing path P2 are the first photodetector 31A and the second photodetector 31B ( Measured in FIG. 1). The control device 40 (FIG. 1) acquires the detection results of the intensities of the first reflected light and the second reflected light measured by the first photodetector 31A and the second photodetector 31B, and is processed. The measurement results of the intensities of the first reflected light and the second reflected light are stored in the storage device 41 at each point 62 (step S3).

When the incident of the laser beam of the first shot to all the processing points 62 in the scanning region 61 (FIG. 1) is completed, the incident of the laser beam of the first processing path P1 and the second processing path P2 is completed. The positions are set at the positions of the first work points 62 (step S5). If an unprocessed work point 62 remains in the scanning region 61 (FIG. 1), the incident positions of the laser beams in the first processing path P1 and the second processing path P2 should be processed next. The position of the work point 62 is set (step S4), and steps S2 and S3 are repeatedly executed.

After step S5, for each of the first processing path P1 and the second processing path P2, the laser beam is based on the intensity of the reflected light corresponding to the processed point 62 (FIG. 3A) stored in the storage device 41. Irradiation conditions of (step S6) are determined.

Hereinafter, a method for determining irradiation conditions will be described. For example, when the intensity of the reflected light is higher than the standard value, it is considered that a part of the inner layer conductor film 52 (FIG. 2B) is already exposed by the processing of the first shot. It is considered that the higher the intensity of the reflected light, the larger the exposed area of the inner layer conductor film 52. When the inner layer conductor film 52 is exposed, it is preferable to reduce the amount of energy input by irradiating the pulsed laser beam from the second shot onward to a value lower than the standard value in order to suppress damage to the inner layer conductor film 52. For example, it is preferable that the higher the intensity of the reflected light, the smaller the amount of energy input. The amount of energy input can be adjusted by the energy density per pulse (pulse energy density) or the number of shots to be irradiated. To adjust the pulse energy density, at least one of the pulse width and the intensity of the laser pulse may be adjusted.

The relationship between the intensity of the reflected light and the irradiation conditions of the pulsed laser beam after the second shot may be determined in advance by conducting various evaluation experiments and stored in the storage device 41. The control device 40 determines the irradiation conditions for the second and subsequent shots with reference to this relationship stored in the storage device 41.

After determining the irradiation conditions, the control device 40 performs laser irradiation on the work point 62 under the irradiation conditions determined in step S6 (step S7). By this irradiation, the recess 55 shown in FIG. 2C is formed, and the inner layer conductor film 52 is exposed on the bottom surface of the recess 55.

When the incident of the laser beam from the second shot onward to all the processing points 62 in the scanning area 61 (FIG. 1) is completed, the processing of the scanning area 61 currently being processed is completed. If the unprocessed scanning region 61 remains, the stage 45 is driven and then the process shown in FIG. 4 is executed again.

When the processed point 62 in which the laser beam from the second shot onward is not incident remains in the scanning region 61 (FIG. 1), the first processing path P1 and the second processing path P2 The incident position of the laser beam is set to the position of the work point 62 to be processed next (step S8). After that, steps S6 and S7 are executed.

Next, a specific example of the method of performing laser irradiation under the irradiation conditions determined in step S6 (step S7) will be described.

When the irradiation condition of the first processing path P1 and the irradiation condition of the second processing path P2 are the same, the control device 40 determines the pulse width of the pulsed laser beam output from the laser light source 10 as the determined irradiation condition. Adjust so that In addition, the number of shots of the pulsed laser beam output from the laser light source 10 may be adjusted.

When the irradiation conditions of the first processing path P1 and the irradiation conditions of the second processing path P2 are different, for example, the irradiation conditions are adjusted for each processing path by any specific method described below.

In the first specific example, the number of shots is made different between the first processing path P1 and the second processing path P2. The control device 40 controls the laser light source 10 based on which of the first processing path P1 and the second processing path P2 requires a larger number of shots. In the machining path where the number of shots required is smaller, the control device 40 controls the first beam scanner 20A or the second beam scanner 20B to send an extra laser pulse to the first beam damper 21A or the second beam damper 21A or the second beam scanner 20B. It is incident on the beam damper 21B.

In the second specific example, the intensity of the laser beam propagating in the first processing path P1 and the laser propagating in the second processing path P2 are performed by adjusting the branching ratio of the laser beam by the first polarizing beam splitter 12. Different from the beam intensity. The branching ratio of the first polarization beam splitter 12 can be adjusted by arranging an optical element for finely adjusting the polarization direction of the laser beam in front of the first polarization beam splitter 12 and finely adjusting the polarization direction. it can.

Next, the excellent effect of the laser processing apparatus according to this embodiment will be described.
In this embodiment, the processing quality can be improved by determining the irradiation conditions for the second and subsequent shots according to the intensity of the reflected light generated during the processing of the first shot. For example, damage to the inner layer conductor film 52 (FIG. 2C) can be suppressed.

Further, in this embodiment, the first reflected light returning from the first processing path P1 and the second reflected light returning from the second processing path P2 are merged into the common measurement path Pm (FIG. 1). After that, the intensity of the first reflected light and the intensity of the second reflected light are measured separately by branching. Therefore, the number of optical elements can be reduced as compared with the configuration in which the reflected light is branched from the processing path of the incident laser beam for each processing path.

Further, in this embodiment, even if the irradiation conditions for the second and subsequent shots are different between the two processing paths, the irradiation conditions can be adjusted separately for each processing path. As a result, it is possible to improve the processing quality of both the two work points 62 processed in the two processing paths.

Next, the laser processing apparatus according to another embodiment will be described with reference to FIGS. 5 and 6. Hereinafter, the description of the configuration common to the examples shown in FIGS. 1 to 4 will be omitted.

FIG. 5 shows the timing at which the pulsed laser beam is incident on the object 50 to be machined in the laser machining apparatus according to the present embodiment, and the driving periods of the first beam scanner 20A and the second beam scanner 20B (FIG. 1) are shown. It is a chart. In the embodiment shown in FIG. 3B, the laser pulse LP1 of the first shot was incident on one work point 62, and then the laser pulse LP1 of the first shot was incident on the next work point 62. In this embodiment, the laser pulse LP1 of the first shot is incident on one work point 62, and then the laser pulse LP2 of the second and subsequent shots is incident on the same work point 62. When the processing of one work point 62 is completed, the next processing of the work point 62 is performed. Such a processing method is called burst processing.

FIG. 6 is a flowchart showing a procedure for drilling using the laser machining apparatus according to the present embodiment. FIG. 4 shows a process of setting the incident positions of the laser beams of the two processing paths to the positions of the processing points 62 (step S11) and a process of outputting a one-shot pulsed laser beam (step S12). It is the same as the processing of step S1 and step S2 of the embodiment.

After outputting the laser pulse of one shot, the control device 40 (FIG. 1) determines the intensity of the first reflected light and the second reflected light measured by the first photodetector 31A and the second photodetector 31B. The measurement result of the intensity of the reflected light is acquired (step S13). For each of the two processing paths, the irradiation conditions of the laser beam from the second shot onward are determined based on the measurement result of the intensity of the reflected light acquired in step S13 (step S14).

After determining the irradiation conditions, the control device 40 irradiates the work point 62 with the laser under the irradiation conditions determined in step S14 (step S15). By this irradiation, the recess 55 shown in FIG. 2C is formed, and the inner layer conductor film 52 is exposed on the bottom surface of the recess 55.

When an unprocessed work point 62 remains in the scanning region 61 (FIG. 3A), the incident positions of the laser beams of the two processing paths are set to the positions of the next work points 62, respectively ( Step S16). After that, the processes from step S12 to step S15 are repeated. When the processing of all the work points 62 in the scanning area 61 is completed, the processing for the scanning area 61 currently being processed is completed.

Also in this example, the same effect as that of the examples shown in FIGS. 1 to 4 can be obtained. Further, in this embodiment, since the processing of the first shot and the processing of the second and subsequent shots with respect to one work point 62 are continuously performed, the measurement result of the intensity of the reflected light is stored in the storage device 41. Immediately after measuring the intensity of the reflected light, the irradiation conditions for the second and subsequent shots are determined.

It goes without saying that each of the above embodiments is exemplary and the configurations shown in different examples can be partially replaced or combined. Similar effects and effects due to the same configuration of a plurality of examples will not be mentioned sequentially for each example. Furthermore, the present invention is not limited to the above-mentioned examples. For example, it will be obvious to those skilled in the art that various changes, improvements, combinations, etc. are possible.

10 Laser light source 11 Branch merging optical system 12 First polarization beam splitter 13A First polarization optical element 13B Second polarization optical element 20A First beam scanner 20B Second beam scanner 21A First beam damper 21B First 2 Beam Damper 22A 1st Condensing Lens 22B 2nd Condensing Lens 30 2nd Polarized Beam Splitter 31A 1st Photodetector 31B 2nd Photodetector 40 Control Device 41 Storage Device 45 Stage 50 Processing Object 51 Dielectric substrate 52 Inner layer conductor film 53 Front surface conductor film 54 Back surface conductor film 55 Recession 61 Scanning area 62 Processing point

Claims (5)

A branching / merging optical system that branches and merges a laser beam, in which a laser beam incident on the branching / merging optical system along an incident path to the branching / merging optical system is subjected to a first processing path and a polarization direction according to the polarization direction. The first reflected light and the second reflected light, which are branched into the second processing path and are incident on the branching and merging optical system along the first processing path and the second processing path, respectively, are transferred to the incident path. The branch merging optical system that merging into a measurement path different from that of
A branching element that branches the first reflected light and the second reflected light merged into the measurement path into different paths.
A first photodetector that measures the intensity of the first reflected light branched by the branching element, and
A laser processing apparatus including a second photodetector for measuring the intensity of the second reflected light branched by the branching element. The branch merging optical system is
A first polarization that transmits a part of a component of a laser beam incident along the incident path and propagates it to the first processing path, and reflects a part of the component and propagates it to the second processing path. Beam splitter and
A first polarized optical element that rotates the polarization direction of the laser beam propagating in the first processing path so that the first reflected light is reflected by the first polarizing beam splitter.
The first aspect of claim 1 includes a second polarized optical element that rotates the polarization direction of the laser beam propagating in the second processing path so that the second reflected light passes through the first polarizing beam splitter. Laser processing equipment. The first processing path and the first processing path according to the intensity of the first reflected light and the intensity of the second reflected light detected by the first photodetector and the second photodetector, respectively. The laser processing apparatus according to claim 1 or 2, further comprising a control device for adjusting irradiation conditions of a laser beam propagating through the processing path of 2 and incident on the object to be processed. The control device includes irradiation conditions of a laser beam propagating through the first machining path and incident on the machining object, and irradiation conditions of a laser beam propagating through the second machining path and incident on the machining object. The laser processing apparatus according to claim 3, which has a function of separately adjusting the above. further,
A first beam scanner that scans a laser beam propagating in the first processing path, and
A second beam scanner that scans the laser beam propagating in the second processing path, and
It has a storage device that stores the positions of a plurality of work points on the object to be machined.
The control device stores the detection results detected by the first photodetector and the second photodetector in the storage device in association with each of the plurality of work points.
The laser processing apparatus according to claim 3 or 4, wherein the irradiation conditions of the laser beams incident on the plurality of processing points are determined based on the measurement results stored in the storage device in association with the processing points. ..

Images