JP2008168297A - Apparatus and method for laser beam machining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for laser beam machining by irradiating a workpiece with a laser beam, by which apparatus and method, high machining quality can be achieved. <P>SOLUTION: The apparatus for laser beam machining comprises a laser source for radiating a pulse laser beam based on a trigger signal to be given from outside, a stage for holding the workpiece, a dividing means which divides the pulse laser beam radiated from the laser source into a plurality of variable number pulse laser beams for irradiating the workpiece held by the stage based on a dividing command signal to be given from outside, and a control unit which outputs the dividing command signal to the dividing means so that a plurality of machining points on the workpiece held by the stage is irradiated with the divided pulse laser beams respectively, and also outputs the trigger signal so that the workpiece held by the stage is irradiated with the laser pulses having the number of shots based on the number of the division commanded to the laser source by the dividing command signal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser processing apparatus and a laser processing method for performing processing by irradiating a workpiece with a laser beam.

  Two types of methods are mainly used for multi-point machining performed by irradiating a workpiece with a laser beam.

  One is a method of performing processing by scanning a laser beam or a processing object while causing one or several laser beams to enter the processing object. For the scanning, for example, a galvano scanner or a moving stage is used. Since a long time is required for scanning and the accompanying positioning, there is a disadvantage that the processing time becomes long.

  The other is that a laser beam is incident on a mask having a large number of light-transmitting areas of a predetermined shape, and a large number of laser beams shaped by passing through the light-transmitting area are irradiated onto the workpiece at a time. This is a method of batch processing. In this method, most of the laser beam is blocked by the mask and energy is lost. For this reason, only a very small amount of output energy of the laser oscillator is used for processing, and the energy efficiency is poor.

  By using a hologram as a mask and diffracting without interrupting the laser beam, a multi-point batch processing method using almost all beam energy has been realized (see, for example, Patent Document 1).

  Further, an invention of a laser transfer processing apparatus provided with a digital phase hologram is disclosed (for example, see Patent Document 2).

  If a digital phase hologram is used, the shaped beam irradiation pattern can be temporally changed. A large machining area can be machined by dividing the machining area on the workpiece into a plurality of small areas and processing each divided small area. Since the irradiation pattern can be changed with time, it is not necessary to replace the mask (digital phase hologram) even when a different irradiation pattern is required in each small area. For this reason, it is possible to reduce processing time and cost.

  However, in different small regions, the number of points to be processed is often different, and the ratio may be several times. For this reason, when the output energy of the laser oscillator is constant, the energy irradiated to the point to be processed is different for each small region, and high quality processing becomes difficult. In a small area where the number of workpieces is large, the energy irradiated per machining point becomes small, and machining defects due to insufficient energy may occur. For example, in the process of forming a through hole in the resin layer, a hole is formed only halfway through the resin layer. Further, in a small region where the number of points to be processed is small, the energy irradiated per point to be processed increases, and a processing failure occurs due to excessive energy. For example, in substrate drilling, the hole diameter may increase or substrate cracking may occur.

JP-A-51-73698 Japanese Patent No. 2723798

  An object of the present invention is to provide a laser processing apparatus capable of performing processing with high processing quality.

  Another object of the present invention is to provide a laser processing method capable of performing processing with high processing quality.

  According to one aspect of the present invention, a laser light source that emits a pulsed laser beam based on a trigger signal given from outside, a stage that holds a workpiece, and a pulsed laser beam emitted from the laser light source Based on a branch command signal given from the above, a branching unit having a variable number of branches for branching into a plurality of pulse laser beams incident on the workpiece held on the stage, and a workpiece on the workpiece held on the stage The branch command signal is sent to the branch means so that the branched pulse laser beam is incident on a plurality of workpiece points, and the number of branches commanded by the branch command signal is sent to the laser light source. A control device for transmitting the trigger signal so that a laser pulse having a number of shots based on the laser beam is incident on a workpiece held on the stage; The laser processing apparatus is provided with.

  According to another aspect of the present invention, a laser light source that emits a pulsed laser beam based on a trigger signal given from outside, and a pulsed laser beam emitted from the laser light source as a branch command signal given from outside Based on this, the branching unit with variable number of branches for branching into a plurality of pulse laser beams, the stage for holding the workpiece at the position where the pulse laser beam branched by the branching unit is incident, and the branching unit So that the branched pulse laser beam is incident on the light shielding member arranged at the position where the pulse laser beam is incident, the plurality of processing points on the workpiece held on the stage, and the light shielding member, respectively. There is provided a laser processing apparatus having a control device for sending the branch command signal.

  Further, according to another aspect of the present invention, the original pulse is applied so that the branched pulse laser beam is incident on each of the processing points in the first region of the processing target in which a plurality of processing points are defined. A step of splitting the laser beam and causing the pulse laser beam having the number of shots determined based on the number of branches to enter the workpiece, and a processing point different from the number of processing points in the first region The original pulse laser beam is branched so that the branched pulse laser beam is incident on the workpiece point in the second region including the number of shots, and the number of shot laser beams determined based on the number of branches is changed. There is provided a laser processing method including a step of causing the object to enter the processing object.

  According to another aspect of the present invention, the branched pulse laser beam is incident on the processing point and the light shielding member in the first region of the processing target in which a plurality of processing points are defined. Branching the original pulse laser beam and making the branched pulse laser beam incident on the object to be processed and the light shielding member, and processing points different from the number of processing points in the first region. The light of the pulse laser beam incident on the processing point in the second region and the light shielding member so that the branched pulse laser beam is incident on the processing point in the second region. The original pulse laser beam is branched so that the intensity is equal to the light intensity of the pulse laser beam incident on the processing point in the first region, and the pulsed laser beam after branching is split into the object to be processed and the light shielding member. Enter Laser processing method having a step of is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the laser processing apparatus which can process with high processing quality can be provided.

  In addition, it is possible to provide a laser processing method capable of performing processing with high processing quality.

  1A and 1B are schematic views showing a laser processing apparatus according to the first embodiment.

  Reference is made to FIG.

  The laser processing apparatus according to the first embodiment shapes a laser light source 10 that continuously emits a pulse laser beam having equal pulse energy, a folding mirror 11, and a beam irradiation pattern, and can be changed in time. It is configured to include a control device 15 for sending a command signal to the hologram 12 and the digital phase hologram 12 and controlling a change in beam irradiation pattern and the like, and a moving stage 13.

  The processed substrate 14 is processed using the laser processing apparatus according to the first embodiment. On the processed substrate 14, a first processed region 14a and a second processed region 14b, which are small regions to be processed, are adjacently defined. For example, in the second processed region 14b, there are twice as many processed points (beam irradiation positions) as the first processed region 14a.

  The processed substrate 14 is, for example, a printed circuit board in which a resin layer having the same thickness is formed on a metal layer, and a process for forming a hole penetrating the resin layer at a processing point is performed.

  The processed substrate 14 is mounted on the mounting surface of the moving stage 13 which is, for example, an XY stage. The moving stage 13 can move the processed substrate 14 in the in-plane direction of the mounting surface.

  A pulsed laser beam is emitted from the laser light source 10 in response to a trigger signal sent from the control device 15. The laser light source 10 includes, for example, a low pulse energy, high repetition frequency type laser oscillator.

  The pulse laser beam emitted from the laser light source 10 is reflected by the folding mirror 11 and enters the digital phase hologram 12. The digital phase hologram 12 is a branching unit with variable number of branches that branches the pulse laser beam emitted from the laser light source 10 into a plurality of pulsed laser beams based on a branch command signal given from the control device 15. The one-shot pulse laser beam incident on the digital phase hologram 12 is energetically divided and applied to each resin layer of the processing points in the first processing region 14 a defined on the processing substrate 14. Incident as a one-shot pulsed laser beam. The light intensity of each pulse laser beam incident on each of the processing points in the first processing region 14a is equal.

  When it is assumed that m processing points exist in the first processing region 14a and no energy loss occurs, one processing point in the first processing region 14a includes a digital phase hologram 12. A laser beam having a pulse energy of 1 / m of the pulse energy of the incident one-shot pulse laser beam is incident.

  Note that the laser beam immediately after passing through the digital phase hologram 12 has an overall and non-uniform light intensity distribution, and the laser beam is applied to a large number of workpiece points when the phase just increases or decreases on the processing substrate 14. A beam is irradiated.

  The control device 15 sends a branch command signal to the digital phase hologram 12 so that the branched pulse laser beams are incident on a plurality of processing points on the processing substrate 14 held by the moving stage 13, respectively. A trigger signal is sent to the laser light source 10 so that a laser pulse having the number of shots based on the number of branches commanded by the branch command signal is incident on the processed substrate 14.

  A k-shot pulse laser beam emitted from the laser light source 10 (k is an integer of 2 or more, for example), and all the processing points in the first processing region 14a are irradiated with the k-shot pulse laser beam, Through-holes are formed in the resin layers at all points to be processed.

  Reference is made to FIG.

  The control device 15 drives the moving stage 13 and emits the digital phase hologram 12 when a predetermined k shot is irradiated to the first processed region 14a and through holes are formed in the resin layers of all processed points. The processed substrate 14 is moved such that the processed laser beam is irradiated to the processing point in the second processing region 14b. At the same time, the beam irradiation pattern of the digital phase hologram 12 is changed so as to correspond to the position of the processing point in the second processing region 14b.

  In response to a control signal from the control device 15, a pulse laser beam emitted from the laser light source 10 is applied to the resin layer at the processing point in the second processing region 14 b through the digital phase hologram 12. There are a different number of processing points in the second processing region 14b than in the first processing region 14a. As an example, there is shown a case where there are twice as many processing points as the first processing region 14a in the second processing region 14b, that is, 2 * m processing points. Since the pulse energy of the pulse laser beam incident on the digital phase hologram 12 is constant, the pulse energy of the one-shot pulse laser beam incident on one processing point in the second processing region 14b is the first target energy. It becomes 1/2 of that of the processing region 14a. For this reason, the control device 15 performs control so that a 2 * k shot pulse laser beam is incident on all the processing points in the second processing region 14b, and all the processing in the second processing region 14b. A through hole is formed in the resin layer at the point.

  As described above, when the laser processing apparatus according to the first embodiment is used, processing can be performed by adjusting the number of times of laser irradiation according to the number of processing points included in each divided small region (processing region). it can.

  In a small region (working region) with many processing points, that is, a small region (working region) with small energy per shot irradiated to each processing point, the number of times of laser beam irradiation is increased and the processing is performed. In a small area (processed area) with few points, the number of times of laser beam irradiation is reduced. For example, the product of the incident energy per shot and the number of shots (number of times of laser beam irradiation) at a processing point in all the small regions (processing regions) is constant (a target included in a certain small region (processing region)). Control is performed so that the ratio between the number of processing points and the number of times of irradiation with the laser beam applied to the small area (processed area) is constant throughout all the small areas (processed areas).

  By performing processing in this way, it is possible to realize processing with high processing quality at each processing point.

  Note that the product of the incident energy per shot at the processing point and the number of shots may not be constant. The number of shots can be determined so that the sum of the energy densities of the pulsed laser beam incident on the processing point in all shots is equal to or higher than the minimum energy density that can realize desired processing (for example, through-hole forming processing). In this case, in order to avoid excessive beam irradiation, for example, the total number of shots of the energy density of the pulse laser beam incident on the processing point is the minimum number of shots that is equal to or higher than the minimum energy density that can achieve the desired processing. It would be appropriate to determine the number of shots within a range of 1.2 times or less.

  2A and 2B are schematic views showing a laser processing apparatus according to the second embodiment.

  The laser processing apparatus according to the second embodiment differs from the laser processing apparatus according to the first embodiment in that it includes a beam block 16. The beam block 16 is disposed at a height between the processing substrate 14 and the digital phase hologram 12 so as not to interfere with processing. Of the laser beam that has passed through the digital phase hologram 12, a laser beam that is not used for processing (not incident on the processing substrate 14) is incident on the beam block 16.

  Reference is made to FIG.

  The pulse laser beam emitted from the laser light source 10 is reflected by the folding mirror 11 and enters the digital phase hologram 12. The pulse laser beam incident on the digital phase hologram 12 is divided in terms of energy and emitted. The light intensities of the pulse laser beams incident on the resin layers at the points to be processed in the first region to be processed 14a defined on the processing substrate 14 are equal. In the digital phase hologram 12, a laser beam having an energy of 1 / n (n is an integer of 2 * m or more) of the energy of the incident laser beam is generated by the branch command signal given from the control device 15 as the first workpiece. A beam irradiation pattern is formed so that all (m) workpiece points in the region 14 a are irradiated and a beam having the remaining energy is incident on the beam block 16.

  A pulsed laser beam of s (s is an integer of 2 * k or more) shot from the laser light source 10 passes through the digital phase hologram 12, and each shot is converted to 1 / n energy to be in the first processed region 14a. Each of the processing points is irradiated, and a hole penetrating the resin layer is formed at all the processing points.

  Reference is made to FIG.

  The control device 15 drives the moving stage 13 and emits the digital phase hologram 12 when a predetermined s shot is irradiated to the first processed region 14a and through holes are formed in the resin layers of all processed points. The processed substrate 14 is moved such that the processed laser beam is irradiated to the processing point in the second processing region 14b. At the same time, the beam irradiation pattern of the digital phase hologram 12 is changed so as to correspond to the position of the processing point in the second processing region 14b.

  The digital phase hologram 12 is irradiated with a laser beam having an energy 1 / n of the energy of the incident laser beam to all (2 * m) processing points in the second processing region 14b, A beam irradiation pattern is formed so that a beam having energy enters the beam block 16.

  The pulse energy and light intensity of one-shot pulse laser beam incident on one processing point in the second processing region 14b are equal to those in the first processing region 14a. Therefore, as in the case of the first processing region 14a, the control device 15 performs control to make the s-shot pulse laser beam enter all processing points in the second processing region 14b. Through holes are formed in the resin layer of all the processing points in the processing region 14b.

  As described above, the laser processing apparatus according to the second embodiment performs processing by irradiating each small region (processed region) with a pulse laser beam having the same number of shots (s shots). In addition, the energy incident on one processing point in one shot through all the small regions (processing regions) is equal.

  Even with the laser machining apparatus according to the second embodiment, machining with high machining quality can be realized at each machining point.

  In the second embodiment, excess energy is incident on the beam block. However, for example, a dummy region may be defined on the processing substrate and energy not used for processing may be incident.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto.

  For example, in the embodiment, drilling processing by light collection has been described. However, for example, the shape of the through-hole of the mask is imaged on the processing substrate so that the shape and size of the hole formed varies depending on the processing position. Irradiation patterns can also be formed.

  In this case, corresponding to the first embodiment, the light intensity per unit area of the laser beam irradiated to the processing position is made equal for each divided small region (processing region). In a small region (working region) with a large processing area, the number of times of laser beam irradiation is increased, and in a small region (processing region) with a small processing area, the number of laser beam irradiations is decreased.

  For example, control is performed so that the product of the pulse energy density and the number of shots (number of times of laser beam irradiation) is constant at the processing positions in all the small regions (processing regions).

  Corresponding to the second embodiment, the pulse energy density to be incident on the machining position is made equal throughout all the small areas (processed areas), and the remaining energy is incident on the beam block, for example. Processing is performed by irradiating each small area (processed area) with a pulse laser beam of the same number of shots.

  It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like can be made.

(A) And (B) is the schematic which shows the laser processing apparatus by a 1st Example. (A) And (B) is the schematic which shows the laser processing apparatus by 2nd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Laser light source 11 Folding mirror 12 Digital phase hologram 13 Moving stage 14 Processing board 14a 1st process area 14b 2nd process area 15 Control apparatus 16 Beam block

Claims (7)

A laser light source that emits a pulsed laser beam based on an externally applied trigger signal;
A stage for holding the workpiece,
A branching unit with variable number of branches for branching the pulsed laser beam emitted from the laser light source into a plurality of pulsed laser beams incident on the object to be processed held on the stage based on a branching command signal given from the outside. When,
The branch command signal is sent to the branching means so that the pulse laser beam after branching is incident on a plurality of processing points on the workpiece held on the stage, respectively, and to the laser light source, A laser processing apparatus comprising: a control device that transmits the trigger signal so that a laser pulse having a number of shots based on the number of branches commanded by the branch command signal is incident on an object to be processed held on the stage.   The branching unit branches the pulse laser beam emitted from the laser light source so that the light intensities of the plurality of pulse laser beams incident on the workpiece held on the stage are equal. The laser processing apparatus as described in.   The control device causes the laser light source to trigger the trigger so that the sum of the energy density of the pulsed laser beam incident on the processing point in all shots is equal to or greater than the minimum energy density capable of realizing desired processing. The laser processing apparatus according to claim 2, which transmits a signal. A laser light source that emits a pulsed laser beam based on an externally applied trigger signal;
Branch means with variable number of branches for branching the pulse laser beam emitted from the laser light source into a plurality of pulse laser beams based on a branch command signal given from outside,
A stage for holding the workpiece at a position where the pulse laser beam branched by the branching unit is incident;
A light shielding member disposed at a position where the pulse laser beam branched by the branching unit is incident;
A laser processing apparatus comprising: a plurality of processing points on a processing object held on the stage; and a control device that sends the branch command signal so that a branched pulse laser beam is incident on the light shielding member.   The control device sends the branch command signal so that the light intensity of each pulse laser beam incident on a plurality of workpiece points on the workpiece held on the stage is constant regardless of the number of branches. The laser processing apparatus according to claim 4. Based on the number of branches, the original pulse laser beam is branched so that the branched pulse laser beam is incident on the workpiece point in the first region of the workpiece in which a plurality of workpiece points are defined. A step of causing a pulsed laser beam of the number of shots determined in step to enter the workpiece;
The original pulse laser beam is branched such that the branched pulse laser beam is incident on each of the processing points in the second region including processing points different from the number of processing points in the first region. And a step of causing a pulse laser beam having the number of shots determined based on the number of branches to enter the object to be processed. The original pulse laser beam is branched and branched so that the branched pulse laser beam is incident on the workpiece point and the light shielding member in the first region of the workpiece in which a plurality of workpiece points are defined. A step of causing a later pulse laser beam to enter the workpiece and the light shielding member;
The branched pulse laser beam is incident on each of the processing points in the second region including processing points different from the number of processing points in the first region and the light shielding member. In addition, the original pulse laser beam so that the light intensity of the pulse laser beam incident on the processing point in the second region becomes equal to the light intensity of the pulse laser beam incident on the processing point in the first region. And a step of causing the pulse laser beam after branching to enter the object to be processed and the light shielding member.

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