JP5818646B2 - Laser processing apparatus and laser processing method - Google Patents

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.

  There is known a technique for monitoring laser processing by photographing a processing position with a camera or measuring the intensity of reflected light of a laser beam incident on a processing object (for example, see Patent Document 1). Using these techniques, whether or not processing of the processing target portion is completed, for example, in the drilling process for forming a through hole in the insulating layer of the printed circuit board in which the insulating layer is laminated on the conductive layer, the through hole is formed in the insulating layer. It can be determined whether or not the conductive layer is exposed.

  In recent years, an insulating layer of a printed circuit board to be subjected to drilling has been mainly made of a mixture of resin and glass fiber. Due to the density of the glass fibers in the in-plane direction of the insulating layer, the optimum value of the energy density of the incident laser beam varies depending on the position on the printed circuit board (insulating layer).

  However, it is difficult to grasp the density of glass fibers before processing. In addition, depending on the shooting of the processing position by the camera and the measurement of the reflected light intensity of the laser beam incident on the printed circuit board, the density of the glass fiber in the insulating layer is judged during processing, and the necessary input to the processing position is made. It has been difficult to estimate the energy, to realize the reduction of the number of shots, and to determine the optimum conditions for laser irradiation. For this reason, for example, when performing drilling of an insulating layer by injecting multiple shots of laser pulses at the same position on a printed circuit board, the laser pulses to be incident on the basis of positions where glass fibers are densely contained Processing conditions such as the number of shots are determined. Therefore, there has been a problem that the number of shots of laser pulses to be irradiated and the processing time increase.

JP-A-11-342484

  An object of the present invention is to provide a laser processing apparatus and a laser processing method capable of performing processing in a short processing time.

  Moreover, it is providing the laser processing apparatus and laser processing method which can implement | achieve quality processing.

  According to one aspect of the present invention, a processing laser light source that emits a pulse laser beam, a first material that has a relatively high workability with respect to the pulse laser beam that emits the processing laser light source, and a workability are relatively A processing object containing a mixture of a low second material and a processing object having a different content ratio of the first material and the second material depending on the processing position of the processing object. According to the content ratio of the first material and the second material, a propagation optical system for propagating the pulse laser beam emitted from the processing laser light source to the object to be processed held by the stage, And a control device for controlling the total energy per unit area, which is input from the processing laser light source to the processing position of the processing object, and (i) a pulse laser emitted from the processing laser light source. A reference light source that emits reference light that passes through a fume that is generated when a beam is incident on a processing position of a workpiece held on the stage, and the reference light source is emitted, A detector that detects the reference light that has passed, and the control device throws the reference light detected by the detector into a processing position of the processing object based on the amount of absorption by the fume. A laser processing device that controls the total energy per unit area, or (ii) generated when a pulsed laser beam emitted from the processing laser light source is incident on a processing position of a processing object held on the stage And a detector for detecting light emitted from the fumes, wherein the control device emits light from the fumes and detects a predetermined wavelength of the light detected by the detectors. Based on kicking the light intensity, is put into the machining position of the workpiece, the laser processing apparatus is provided for controlling the total energy per unit area.

  According to another aspect of the present invention, (a) a first material having a relatively high workability with respect to a pulse laser beam emitted from a processing laser light source, and a second material having a relatively low workability. The processing laser light source is emitted to a processing object including a mixture of the first material and the second material depending on the processing position of the processing object. (B) a unit area that is input from the processing laser light source to a processing position of the processing object according to a content ratio of the first material and the second material. (I) In the step (a), a reference light is passed through a fume generated when a pulse laser beam is incident on the object to be processed, and the step (a) is performed. b) Smell , A laser processing method for controlling the total energy per unit area to be input to the processing position of the processing object based on the amount of absorption of the reference light by the fume, or (ii) in the step (a), Detecting light emitted from a fume generated when a pulsed laser beam is incident on the workpiece, and in the step (b), based on the light intensity at a predetermined wavelength of the light emitted from the fume, There is provided a laser processing method for controlling the total energy per unit area to be input to the processing position of the processing object.

  According to the present invention, it is possible to provide a laser processing apparatus and a laser processing method capable of performing processing in a short processing time.

  Further, it is possible to provide a laser processing apparatus and a laser processing method capable of realizing high-quality processing.

1A is a schematic view showing a laser processing apparatus according to the first embodiment, FIG. 1B is a schematic cross-sectional view of a printed circuit board 50, and FIG. 1C is a scanning range of a galvano scanner 13 and a reference laser. It is a schematic top view which shows the relationship with the passage range of the beam 15a. FIG. 2A is a schematic graph showing the wavelength dependence of the light absorption rate of the epoxy resin and the glass, and FIGS. 2B to 2D are schematic graphs showing the wavelength dependence of the light intensity of the reference laser beam 15a. It is. FIG. 3 is a flowchart showing a laser processing method according to the second embodiment. FIG. 4 is a flowchart showing a laser processing method according to the third embodiment. FIG. 5 is a flowchart showing a laser processing method according to the fourth embodiment. FIG. 6A is a schematic view showing a laser processing apparatus according to the fifth embodiment, and FIG. 6B is a schematic plan view showing the arrangement positions of the line sensor 17 and the spectrometer 18. FIG. 7 is a schematic graph showing the wavelength dependence of the emission intensity of fume. FIG. 8 is a flowchart showing a laser processing method according to the sixth embodiment. FIG. 9 is a flowchart showing a laser processing method according to the seventh embodiment. FIG. 10 is a flowchart showing a laser processing method according to the eighth embodiment.

  FIG. 1A is a schematic view showing a laser processing apparatus according to the first embodiment. The laser processing apparatus according to the first embodiment includes a processing laser light source 10, a beam shaper 11, a folding mirror 12, a galvano scanner 13, an fθ lens 14, a reference laser light source 15, a filter 16, a line sensor 17, and an XY stage 20. The control device 30 and the storage device 31 are included. On the XY stage 20, a printed circuit board 50 that is a processing target is placed. The XY stage 20 holds the printed circuit board 20 and can be moved in an XY plane (horizontal plane).

  The processing laser light source 10 includes, for example, a carbon dioxide laser oscillator, and emits a processing laser beam 10a that is a pulse laser beam. The processing laser beam 10 a is shaped by the beam shaper 11, shaped by the beam cross-section, reflected by the folding mirror 12, and then the print held on the XY stage 20 via the galvano scanner 13 and the fθ lens 14. Incident on the substrate 50. The galvano scanner 13 is a beam scanner that includes two oscillating mirrors and can move the incident position on the printed circuit board 50 by changing the emitting direction of the processing laser beam 10a. The processing laser beam 10a is incident on the printed board 50 vertically downward (Z-axis negative direction).

  FIG. 1B shows a schematic cross-sectional view of the printed circuit board 50. The printed circuit board 50 has a structure in which an insulating layer 52 is laminated on a conductive layer (metal layer) 51 made of, for example, copper, and a conductive layer (metal layer) 53 made of, for example, copper is further laminated thereon. Have The processing laser beam 10a is incident on the conductive layer 53 side of the printed circuit board 50 from vertically above. By irradiating a plurality of shots of the processing laser beam 10a, a through-hole penetrating the conductive layer 53 and the insulating layer 52 and having the surface of the conductive layer 51 as a bottom surface is formed. When the processing laser beam 10a is incident on the insulating layer 52 of the printed board 50, fumes (a gaseous product in which the insulating layer 52 is decomposed) are generated from the incident position.

  The insulating layer 52 is, for example, FR-4 (flame retardant type 4), and is a composite layer of epoxy resin and glass in which an epoxy resin and glass fiber are mixed and kneaded. Epoxy resin has a relatively high workability (removability) with respect to the processing laser beam 10a (easy to be processed), and glass fiber has a relatively low workability with respect to the processing laser beam 10a (not easily processed). Due to the density of the glass fibers in the in-plane direction of the insulating layer 52, the workability of the insulating layer 52 with respect to the processing laser beam 10a differs depending on the position on the printed board 50 (insulating layer 52). The positions where the glass fibers are densely contained are difficult to be processed, and the positions where the glass fibers are sparsely contained are easy to be processed.

  Reference is again made to FIG. 1A. The reference laser light source 15 emits a continuous-wave reference laser beam 15a in the wavelength region of visible light, for example. The traveling direction of the reference laser beam 15a is the X axis positive direction. The reference laser beam 15a is a rectangular two-dimensional line beam having a cross-sectional shape of a beam incident on a virtual plane perpendicular to the X axis, the Y axis direction being the major axis direction and the Z axis direction being the minor axis direction. The reference laser beam 15a is emitted from the reference laser light source 15 so as to pass above the printed circuit board 50 held by the XY stage 20 and through the fumes 60 generated when the processing laser beam 10a enters the insulating layer 52. Emitted. The reference laser beam 15a intersects the optical axis of the processing laser beam 10a, and is orthogonal in this example.

  The reference laser beam 15a is incident on a filter 16 that transmits only light in a specific wavelength range. The light that has passed through the filter 16 in the reference laser beam 15a is incident on the line sensor 17 that is a light receiving device. The line sensor 17 is a detector that has a configuration in which, for example, a large number of photodiodes (light receiving elements) are arranged along the Y-axis direction, and can detect the reference laser beam 15 a that has passed through the fume 60. Information regarding the reference laser beam 15 a detected by the line sensor 17 is transmitted to the control device 30.

  The control device 30 controls the emission of the laser beams 10 a and 15 a from the processing laser light source 10 and the reference laser light source 15. Further, the incident position of the processing laser beam 10a on the printed circuit board 50 is controlled by the galvano scanner 13. Further, the movement of the printed circuit board 50 by the XY stage 20 is controlled. For example, the storage device 31, which is a memory, stores the coordinates of the incident position (through hole forming position) of the processing laser beam 10 a on the printed circuit board 50. The control device 30 controls the operation of the galvano scanner 13 based on the stored contents of the storage device 31 so that the processing laser beam 10a enters the through-hole formation position on the printed circuit board 50 and forms the through-hole. .

  As will be described in detail later, the control device 30 adds the total per unit area to be input to each through hole forming position based on information on the reference laser beam 15a detected by the line sensor 17, for example, information on light intensity. Control energy.

  FIG. 1C is a schematic plan view showing the relationship between the scanning range of the galvano scanner 13 and the passing range of the reference laser beam 15a. In this figure, by changing the direction of the two oscillating mirrors of the galvano scanner 13, a range (scanning range) on the printed board that can be scanned with the processing laser beam 10 a is marked with 50. . The processing laser beam 10a is irradiated to the through hole formation position on the printed circuit board arranged in the scanning range 50 of the galvano scanner 13, and the conductive layer 53 and the insulating layer 52 are penetrated to the irradiation position to reach the conductive layer 51. A through hole is formed. The drilling of the printed board 50 is performed by, for example, cycle processing. When the drilling process for the through-hole formation position within the scanning range of the galvano scanner 13 is completed, the other processing range of the printed circuit board 50 is moved to the scanning range of the galvano scanner 13 by the operation of the XY stage 20. Drill holes.

  The scanning range of the galvano scanner 13 is a square area of 50 mm in each of the X-axis and Y-axis directions, for example. The reference laser light source 15 is disposed on the X axis negative direction side of the scanning range of the galvano scanner 13, and the filter 16 and the line sensor 17 are disposed on the X axis positive direction side of the scanning range of the galvano scanner 13. The reference laser beam 15 a is emitted from the reference laser light source 15 so as to cover the entire scanning range of the galvano scanner 13 in plan view, passes through the filter 16, and enters the line sensor 17.

  By passing the reference laser beam 15a, which is a two-dimensional line beam, over the entire scanning range 50 of the galvano scanner 13, the reference laser beam 15a is generated from all through-hole forming positions in the scanning range 50. Can enter the fume. The laser incident point may be monitored by moving the line sensor in the horizontal direction or changing the angle.

FIG. 2A is a schematic graph showing the wavelength dependence of the light absorption rate of epoxy resin and glass. The horizontal axis of the graph indicates the wavelength in the unit “nm”, and the vertical axis indicates the light absorption rate in the unit “%”. A curve a represents the wavelength dependency of the light absorption rate of the epoxy resin, and a curve b represents the wavelength dependency of the light absorption rate of the glass. The wavelength λ ₁ in the graph is a wavelength at which the light absorption rate of the epoxy resin is small and the light absorption rate of the glass is large. The wavelength λ ₁ is the wavelength of the reference laser beam 15 a emitted from the reference laser light source 15.

2B to 2D are schematic graphs showing the wavelength dependence of the light intensity of the reference laser beam 15a. The horizontal axis of the graph represents the wavelength in the unit “nm”, and the vertical axis represents the light intensity in the unit “W / cm ² ”.

FIG. 2B shows the relationship between the wavelength and the light intensity of the reference laser beam 15a before passing through the filter 16 when not processed (when no fume is generated). Light intensity of the reference laser beam 15a is strongest at a wavelength lambda _1.

FIG. 2C shows the relationship between the wavelength and the light intensity of the reference laser beam 15 a that passes through the filter 16 and enters the line sensor 17 when not processed (when no fume is generated). Light intensity of the reference laser beam 15a is strongest at a wavelength lambda _1, the value is F _1. The filter 16 is a band-pass filter that transmits light with wavelengths λ _{m to} λ _M , for example.

  FIG. 2D shows that when the insulating layer 52 is processed (when fumes are generated), the reference laser beam 15a passes through the fumes above the through-hole formation position, and then passes through the filter 16 to pass through the line sensor 17. Is the relationship between the wavelength and the light intensity of light incident on the light, that is, for example, light incident on a photodiode disposed at a position where the Y coordinate is equal to the hole being processed where fume is generated.

A part of the reference laser beam 15a is absorbed by the fumes generated when the insulating layer 52, which is a composite material layer containing epoxy resin and glass, is processed. As shown in FIG. 2A, an epoxy resin does not absorb much light with a wavelength lambda _1, the glass absorbs at high absorption. Therefore, in accordance with the glass content in the insulating layer 52, the reference laser beam 15a (with the wavelength λ ₁₎ incident on the photodiode disposed at the position where the Y coordinate is equal to the hole being processed where fume is generated. light intensity of the light) varies in the range of F ₁ smaller value. The light intensity when the glass content is relatively high is smaller than the light intensity when the glass content is relatively low. In the example shown in this figure, the intensity of light of wavelength λ ₁ is F ₂ .

Line sensor 17, for example, prior to processing, is transmitted through the filter 16 during fume nonoccurrence detects the reference laser beam 15a incident (wavelength lambda ₁ of the light) to the line sensor 17, grasp the light intensity F ₁ To do. The grasped light intensity F ₁ is transmitted to the control device 30 and stored in the storage device 31.

For example, in a state where the reference laser beam 15 a is emitted from the reference laser light source 15, the processing laser beam 10 a is irradiated on the insulating layer 52 of the printed circuit board 50, and drilling is performed. Processing laser beam 10a laser reference has passed through the fumes generated from the position incident beam 15a (wavelength lambda ₁ of the light) is detected by the line sensor 17, the light intensity, for example F ₂ is grasped. Information about the reference laser beam 15a detected by the line sensor 17, for example, the intensity of the reference laser beam 15a which the processing laser beam 10a passes through the fumes generated from the incident position (wavelength lambda ₁ of the light) is F ₂ Is transmitted to the control device 30.

The control device 30 performs processing from the processing laser light source 10 so that the processing laser beam 10 a is incident on a predetermined position on the printed circuit board 50 based on the coordinates of the through-hole formation position stored in the storage device 31. emission of use the laser beam 10a, and, because it controls the operation of the galvano scanner 13, the light intensity F ₂ obtained is, reference laser beam 15a passing through the fume generated from any hole in the formation (wavelength λ It is possible to grasp whether the light intensity is ₁ ). The detection by the line sensor 17 may be performed in synchronization with the emission of the processing laser beam 10a. From the light intensity F ₁ and the light intensity F ₂ , the control device 30 absorbs (F ₁ −F ₂ ) / F ₁ with an absorptance α (absorption rate α of the reference laser beam 15a (light with wavelength λ ₁ ) by fume). ) And is stored in the storage device 31 in association with the through-hole formation position. (F ₁ -F ₂ ) is a value corresponding to the amount of absorption by the fume of the reference laser beam 15a (light having the wavelength λ ₁ ).

  FIG. 3 is a flowchart showing a laser processing method according to the second embodiment. Hereinafter, the flowchart according to the embodiment shows a processing procedure at one through hole forming position. The laser processing method according to the embodiment is performed under the control of the control device 30. Further, the area of the incident region (beam spot) of the processing laser beam 10a incident on the printed circuit board 50 is equal between all shots.

In step S101, the first-shot laser pulse is incident on the through hole forming position. The pulse energy density is 40 J / cm ² , for example. By irradiating the printed board 50 (conductive layer 53) with the first shot laser pulse, a hole that penetrates the conductive layer 53 and exposes the surface of the insulating layer 52 is formed.

In step S102, a second-shot laser pulse is incident on the exposed insulating layer 52 surface. This is a first shot laser pulse incident on the insulating layer 52, and the pulse energy density is, for example, 30 J / cm ² . By this laser pulse irradiation, a hole having a depth halfway in the thickness direction of the insulating layer 52 is formed.

In step S103, it detects the intensity of the through hole forming positions reference laser beam 15a passing through the fume generated from (wavelength lambda ₁ of the light), is calculated absorptance alpha. In calculating the absorptance α, the light intensity F ₁ of the reference laser beam 15a (light having the wavelength λ ₁ ) shown in FIG. 2C is measured in advance.

In step S104, the absorption rate α is compared with predetermined threshold values S ₁ , S ₂ , and S ₃ . The threshold values S ₁ , S ₂ , and S ₃ are obtained by conducting experiments prior to processing, obtaining appropriate values, and storing them in the storage device 31. For example the threshold _{S 1} is 50%, _{S 2} is 30%, _{S 3} is 1%. The control device 30 compares the absorption rate α with the threshold values S ₁ , S ₂ , S ₃ .

When S ₁ <α, that is, the absorptance of the reference laser beam 15a (light of wavelength λ ₁ ) by the fumes generated from the through hole formation position (beam incident position) of the insulating layer 52 exceeds 50%, for example 80% If YES, go to step S105. When S ₁ <α, it is determined that the glass fiber content of the insulating layer 52 at the through hole formation position is relatively high (glass fibers are densely contained). That is, the insulating layer 52 at that position is relatively low in workability, and the hole formation depth is relatively shallow. For this reason, the input energy is increased and the next shot (third shot) is made incident. The pulse energy density of the next shot laser pulse is, for example, 40 J / cm ² .

  For example, the control device 30 increases the energy density of the laser pulse 10 a incident on the insulating layer 52 by increasing the pulse energy of the laser pulse 10 a emitted from the processing laser light source 10. Alternatively, in the example shown in FIG. 1A, the laser beam 10 a that is configured from the beam shaper 11 to the fθ lens 14 and is emitted from the processing laser light source 10 is propagated to the printed circuit board 50 held on the XY stage 20. The energy density of the laser pulse 10a incident on the insulating layer 52 may be increased by including an attenuator in the propagating optical system to reduce the attenuation rate. Alternatively, the energy density of the laser pulse 10 a incident on the insulating layer 52 can be increased by including an acousto-optic element in the propagation optical system and increasing the pulse width of the laser pulse 10 a incident on the insulating layer 52.

When S ₂ <α ≦ S ₁ , that is, when the absorption rate of the reference laser beam 15a by the fumes generated from the through hole formation position (beam incident position) of the insulating layer 52 exceeds 30% and is 50% or less, for example, 40%. If there is, the process proceeds to step S106. When S ₂ <α ≦ S _1, it is determined that the glass fiber content of the insulating layer 52 at the through hole formation position is average (glass fibers are included at an average density). That is, the workability of the insulating layer 52 at that position and the formation depth of the hole are relatively average. Therefore, the next shot (third shot) is made incident while maintaining the input energy (with the pulse energy density kept at, for example, 30 J / cm ² ).

When S ₃ <α ≦ S ₂ , that is, when the absorption rate of the reference laser beam 15a by the fumes generated from the through hole formation position (beam incident position) of the insulating layer 52 exceeds 1% and is 30% or less, for example, 20%. If there is, the process proceeds to step S107. When S ₃ <α ≦ S _2, it is determined that the glass fiber content of the insulating layer 52 at the through hole formation position is relatively low (glass fibers are included sparsely). That is, the insulating layer 52 at that position has a relatively high workability, and the hole formation depth is relatively deep. For this reason, the input energy is reduced and the next shot (third shot) is made incident. The pulse energy density of the next shot laser pulse is, for example, 20 J / cm ² .

  For example, the control device 30 reduces the energy density of the laser pulse 10 a incident on the insulating layer 52 by reducing the pulse energy of the laser pulse 10 a emitted from the processing laser light source 10. Alternatively, the energy density of the laser pulse 10a incident on the insulating layer 52 may be reduced by including an attenuator in the propagation optical system and increasing the attenuation rate. Alternatively, the energy density of the laser pulse 10 a incident on the insulating layer 52 can be reduced by including an acousto-optic element in the propagation optical system and reducing the pulse width of the laser pulse 10 a incident on the insulating layer 52.

When α ≦ S ₃ , that is, when the absorptance of the reference laser beam 15a (light having the wavelength λ ₁ ) by the fumes generated from the through hole forming position (beam incident position) of the insulating layer 52 is 1% or less, It is determined that a hole penetrating the insulating layer 52 has been formed, the process proceeds to step S108, and the processing for the through-hole formation position is terminated.

If the process proceeds to step S105 to step S107, then the process returns to step S103. That laser regard to fumes generated by irradiation of the pulse 10a, detects the intensity of the reference laser beam 15a passing through the fume (wavelength lambda ₁ of the light), the absorption rate of 3 shot (the second shot to the insulating layer 52) α is calculated and compared with threshold values S ₁ , S ₂ , and S ₃ in step S104. Then, based on the magnitude relationship between the absorption rate α and the thresholds S ₁ , S ₂ , S ₃ , the process proceeds to steps S 105 to S 108.

Finally, when α ≦ S ₃ , the processing for the through hole forming position is completed.

For example, when the absorptance α calculated from the intensity of the reference laser beam 15a (light having the wavelength λ ₁ ) that has passed through the fumes generated by the irradiation of the second shot laser pulse is S ₁ <α, 3 Since the shot laser pulse is incident on the insulating layer 52 at a pulse energy density of 40 J / cm ² , a hole penetrating the conductive layer 53 and the insulating layer 52 can be formed by the shot (three shots in total). Depending on the value of the absorption rate α, the input energy of the next shot is increased at the position where it is determined that the glass fiber is densely contained. A hole can be formed in three shots at the position where the through hole has been formed by irradiation. For this reason, the number of shots can be reduced and the processing time can be shortened.

Further, when the absorptance α is S ₂ <α ≦ S ₁ , even when the third shot laser pulse is incident at a pulse energy density of 30 J / cm ² , the shot (total 3 shots) A hole penetrating the conductive layer 53 and the insulating layer 52 is formed.

Further, when the absorptance α is S ₃ <α ≦ S ₂ , the third shot laser pulse is also incident on the insulating layer 52 at a pulse energy density of 20 J / cm ² , and the shot (total In three shots, a hole penetrating the conductive layer 53 and the insulating layer 52 is formed. Depending on the value of the absorption rate α, the energy of the next shot is reduced for the position where it is determined that the glass fiber is sparsely contained. cm ^2, at a position to form a charged to the through hole of the energy of the total 100 J / cm ^2, it is possible to form the hole in the introduction of energy in total 90 J / cm ^2. Since holes can be formed with less excess energy input, for example, high-quality drilling without overhang can be realized.

FIG. 4 is a flowchart showing a laser processing method according to the third embodiment. The third embodiment, in step S104, in terms of comparing the absorption rate α and a threshold S _3, differs from the second embodiment.

In the third embodiment, when S ₃ <α, in step S 106, the input energy is maintained, the pulse energy density remains at 30 J / cm ² , and the next shot (third shot) is incident on the insulating layer 52. Let When the alpha ≦ S _3, the process proceeds to step S108, and terminates the processing for the through hole forming positions. If the process proceeds to step S106, the process returns to step S103, and the subsequent processing is repeated.

The second embodiment is based on the value of the absorptivity α calculated from the intensity of the detected reference laser beam 15a (wavelength lambda ₁ of the light), depending on the amount of the glass fiber content, the next shot put Although the energy is increased or decreased, in the third embodiment, the input energy of the next shot is not changed.

Absorption rate of the reference laser beam 15a passing through the fumes generated by irradiation of the processing laser beam 10a detects the intensity of the (wavelength lambda ₁ of the light), the reference laser beam 15a by the fumes (wavelength lambda ₁ of light) alpha When α ≦ S ₃ , the processing for the through hole formation position is terminated, so that the glass fiber is contained in a sparsely large number of shots at the position where the glass fibers are densely contained. A hole can be formed at a relatively small number of shots. For this reason, it is possible to irradiate a laser pulse with a fixed number of shots regardless of the through-hole formation position, reduce the number of shots compared to the case of forming a through-hole, shorten the processing time, and realize high-quality processing. .

  FIG. 5 is a flowchart showing a laser processing method according to the fourth embodiment. In the fourth embodiment, the input energy after the next shot is maintained, and the number of shots from the next shot to the formation of the through hole is determined based on the absorption rate α. When the next shot is not incident, the number of shots after the next shot is zero.

For example, in step S104, the absorption rate α is compared with the threshold values S ₁ , S ₂ , and S _3, and when S ₁ <α, the process proceeds to step S109 and the laser pulse 10a having a pulse energy density of 30 J / cm ² is input. The number of shots is 2. In the case of cycle processing, two shots of the processing laser beam 10a are incident on the through hole forming position, the process proceeds to step S111, and the processing for the through hole forming position is completed.

When S ₂ <α ≦ S ₁ and when S ₃ <α ≦ S ₂ , that is, when S ₃ <α ≦ S ₁ , the process proceeds to step S110 until the end of processing for the through hole formation position. The number of shot shots is 1. The processing laser beam 10a having a pulse energy density of 30 J / cm ² is incident on that position for only one more shot, the process proceeds to step S111, and the processing ends.

When the alpha ≦ S _3, the process proceeds to step S111, and terminates the processing for the through hole forming positions.

  The laser processing method according to the fourth embodiment also changes the number of shots of the processing laser beam 10a irradiated to the through hole forming position according to the density of the glass fibers in the in-plane direction of the insulating layer 52. For this reason, the number of shots can be reduced, the processing time can be shortened, and high-quality processing can be realized.

The number of irradiation shots after the next shot is set to 2 when S ₁ <α, ₁ when S ₃ <α ≦ S ₁ , and 0 when α ≦ S ₃ . May compare only α with S ₁ and S ₃ .

In the laser processing methods according to the second to fourth embodiments, fumes generated from the insulating layer 52 at the through hole formation position based on information on the reference laser beam 15a detected by the line sensor 17, for example, information on light intensity. According to, determined absorptivity of the reference laser beam 15a (wavelength lambda ₁ of light) (the absorption amount corresponding value), high and low content of the glass fibers in the insulating layer 52 at that position, and are formed in that position This is a laser processing method for determining the depth of a hole and controlling the total energy per unit area, which is introduced into the through hole forming position.

In the first laser processing apparatus, a carbon dioxide laser (laser beam in the infrared wavelength region) is used as the processing laser beam 10a, and a laser beam in the visible wavelength region is used as the reference laser beam 15a. . Two laser beams 10a, the wavelength region of 15a are different, in the calculation of the absorption rate of the reference laser beam 15a by the fumes (wavelength lambda ₁ of the light) alpha, it is possible to reduce the error.

  FIG. 6A is a schematic view showing a laser processing apparatus according to the fifth embodiment. When compared with the laser processing apparatus according to the first embodiment, the laser processing apparatus according to the fifth embodiment includes a spectroscope 18 that does not include the reference laser light source 15 and separates (decomposes) the incident light. It is different in point. The spectroscope 18 is installed at the position where the filter 16 is disposed in the first embodiment. Instead of the spectroscope 18, for example, a filter 16 that is a band-pass filter can be used.

  FIG. 6B schematically shows the arrangement positions of the line sensor 17 and the spectroscope 18. The fumes generated when the processing laser beam 10a enters the insulating layer 52 of the printed circuit board 50 emits light itself. The line sensor 17 and the spectroscope 18 are wider than the right side of the scanning range 50 on the X axis positive direction side of the scanning range 50 of the galvano scanner 13 in the position where light emission from the fume can be received, in the example shown in this figure. Placed in range. The light emitted from the fume passes through the spectroscope 18 and is decomposed into a spectrum, and then enters the line sensor 17. The line sensor 17 is a detector capable of detecting the light intensity at a predetermined wavelength of light emitted from the fume and decomposed into a spectrum.

FIG. 7 is a schematic graph showing the wavelength dependence of the emission intensity of fume. The horizontal axis of the graph indicates the wavelength in the unit “nm”, and the vertical axis indicates the light intensity in the unit “W / cm ² ”. Curve a is when the processing laser beam 10a is incident on the through hole forming position where the epoxy resin content is relatively high and the glass fiber content is relatively low (glass fibers are sparsely contained). Represents the wavelength dependence of the light intensity with respect to the emission of fumes generated in. Curve b shows a case where the processing laser beam 10a is incident on a through hole forming position where the epoxy resin content is relatively low and the glass fiber content is relatively high (glass fibers are densely contained). Represents the wavelength dependence of the light intensity with respect to the emission of fumes generated in. A wavelength λ _E in the graph is a peak wavelength of light emission of the epoxy resin (a peak wavelength of light emitted from a fume generated when the processing laser beam 10a is incident on the epoxy resin), and a wavelength λ _{G in the} graph is The peak wavelength of light emission of the glass fiber (the peak wavelength of light emitted from the fumes generated when the processing laser beam 10a is incident on the glass fiber).

In the example shown in this figure, the light emitted from the fumes generated when the processing laser beam 10a is incident on the through hole forming position where the glass fibers are sparsely contained has a light intensity at the wavelength λ _E of F _3. And the light intensity at the wavelength λ _G is F ₄ . Further, the light emitted from the fumes generated when the processing laser beam 10a is incident on the through hole forming position where the glass fibers are densely contained has a light intensity at a wavelength λ _E of F ₅ and a wavelength of λ _G light intensity at is _{F 6.}

The ratio of the light intensity at the wavelength λ _{E to} the light intensity at the wavelength λ _G is F ₄ / F ₃ for light emission from the fumes generated by the decomposition of the insulating layer 52 at the positions where the glass fibers are sparsely contained. The light emission from the fumes generated by the decomposition of the insulating layer 52 at the position where the glass fibers are densely contained is F ₆ / F ₅ . F ₆ / F ₅ is larger than F ₄ / F ₃ .

In the laser processing apparatus according to the fifth embodiment, the light processing laser beam 10a is emitted from the fumes generated when incident on the insulating layer 52, and the light intensity F _G at wavelength lambda _G, light at a wavelength lambda _E Based on the strength F _E , for example, based on the ratio F _G / F _E , the density of the glass fibers at the through hole formation position and the depth of the hole formed at that position are determined, and the through hole formation position To control the total energy per unit area.

  FIG. 8 is a flowchart showing a laser processing method according to the sixth embodiment. The laser processing methods according to the sixth to eighth embodiments described below are performed using the laser processing apparatus according to the fifth embodiment. The laser processing method according to the sixth embodiment corresponds to the laser processing method according to the second embodiment performed using the laser processing apparatus according to the first embodiment.

In step S121, the first-shot laser pulse is incident on the through hole forming position. The pulse energy density is 40 J / cm ² , for example. By irradiating the printed board 50 (conductive layer 53) with the first shot laser pulse, a hole that penetrates the conductive layer 53 and exposes the surface of the insulating layer 52 is formed.

In step S122, a second-shot laser pulse is incident on the exposed insulating layer 52 surface. This is a first shot laser pulse incident on the insulating layer 52, and the pulse energy density is, for example, 30 J / cm ² . By this laser pulse irradiation, a hole having a depth halfway in the thickness direction of the insulating layer 52 is formed.

In step S123, the light emitted from the fumes generated from the through hole forming position is detected. For example the wavelength lambda light intensity at _{G F G,} and detects light intensity _{F E} at wavelength lambda _E, calculates the ratio β of _{(= F G / F E)} . Detection of light emitted by the fume is performed using the spectroscope 18 and the line sensor 17, and information on the detected light emission from the fume is transmitted from the line sensor 17 to the control device 30. The control device 30 calculates the value of the ratio β. Information relating to the light emitted by the fume, for example, the values of the light intensities F _G and F _E and the ratio β are stored in the storage device 31.

In step S124, the comparing light intensity _{F E} with a predetermined threshold value _{S 4.} Threshold S _4, prior to processing conducted experiments to obtain the appropriate value stored in the storage device 31.

When F _E ≦ S ₄ , that is, when the light intensity F _{E at the} wavelength λ _E is less than or equal to the threshold S ₄ among the light emitted by the fumes, it is determined that a hole penetrating the insulating layer 52 has been formed, and step S129 is performed. The process for the through hole forming position is finished.

When S _{4 <F E,} the holes passing through the insulating layer 52 is determined not to be formed, the process proceeds to step S125, the comparing the β and a threshold _S 5, _{S 6.} As for the threshold values S ₅ and S ₆ , an experiment is performed prior to processing, an appropriate value is obtained, and stored in the storage device 31.

In the step S124, the comparison between light intensity _{F G} and the threshold value _{S 4,} when _{F G} ≦ _{S 4,} the process proceeds to step S129, and terminates the processing for the through hole formation positions _of S 4 _{<F G} At this time, the process may proceed to step S125. In the threshold value S ₄ without, it is also possible to use other thresholds.

When the value of β is relatively small, the glass fiber is sparsely included in the through hole formation position, and when the value of β is relatively large, the glass fiber is densely included in the through hole formation position. It is. Therefore, in step S125, when S ₅ <β, it is determined that the glass fiber content of the insulating layer 52 at the through hole formation position is relatively high and the hole formation depth is relatively shallow, and step S126. Then, the input energy is increased and the next shot (third shot) is made incident on the insulating layer 52. The pulse energy density of the next shot laser pulse 10a is, for example, 40 J / cm ² . The method for increasing the pulse energy density is the same as in the laser processing method according to the second embodiment, for example.

When S ₆ <β ≦ S ₅ , it is determined that the glass fiber content of the insulating layer 52 at the through hole formation position is average, and the formation depth of the hole is also average, and the process proceeds to step S127. The processing laser beam 10a with the input energy maintained and the pulse energy density of 30 J / cm ² is made incident on the insulating layer 52 as the next shot (third shot).

When β ≦ S ₆ , it is determined that the glass fiber content of the insulating layer 52 at the through hole forming position is relatively low and the hole forming depth is relatively deep, and the process proceeds to step S128 to input energy. And the next shot (third shot) is made incident. The pulse energy density of the next shot laser pulse 10a is, for example, 20 J / cm ² . The method of reducing the pulse energy density is the same as that of the laser processing method according to the second embodiment, for example.

If the process proceeds to step S126 to step S128, the process returns to step S123. Namely even fumes generated by irradiation of the Me 3 shot laser pulses, the light intensity F _G in the light, for example, the wavelength lambda _G fumes _emitted, and detects light intensity F _E at wavelength lambda _E, calculates the ratio β . In step S124, it is determined whether or not the next shot is necessary. In the case of “necessary”, in step S125 and step S126 to step S128, the next shot is subjected to the pulse energy density reflecting the value of β, and the through hole formation position. Is incident on the insulating layer 52. In the case of “No”, the processing for the through hole forming position is completed.

  Also by the laser processing method according to the sixth embodiment, the processing time can be shortened by reducing the number of shots, and high-quality processing can be realized.

  FIG. 9 is a flowchart showing a laser processing method according to the seventh embodiment. Unlike the sixth embodiment, the seventh embodiment does not use the ratio β. The laser processing method according to the seventh embodiment corresponds to the laser processing method according to the third embodiment performed using the laser processing apparatus according to the first embodiment.

In the seventh embodiment, in step S123, for example, to detect the light intensity _{F E} at wavelength lambda _E, is stored in the storage device 31. Then, in step S124, the performed comparison of the light intensity _{F E} and the threshold value _{S 4,} when the _{F E} ≦ _{S 4} proceeds to step S129, and terminates the processing for the through hole forming positions. The process proceeds to step S127 when the S _{4 <F E,} to maintain the input energy is incident the next shot. If the process proceeds to step S127, then the process returns to step S123, and the subsequent processes are repeated until the hole machining at that position is completed in step S129.

Incidentally, detecting the light intensity _{F G} in step S123, in step S124, the relative comparison between light intensity _{F G} and the threshold value _{S 4,} when _{F G} ≦ _{S 4,} the process proceeds to step S129, the through hole forming positions Exit _processing, when S 4 _{<F G,} may proceed to step S127. In the threshold value S ₄ without, it is also possible to use other thresholds.

In the sixth embodiment, based on the light intensities F _G and F _E , for example, the ratio β thereof is calculated, and the input energy of the next shot is increased or decreased according to the amount of the glass fiber content. In this embodiment, the input energy of the next shot is not changed.

Detecting the emission of fumes themselves generated by irradiation of the processing laser beam 10a, for example by measuring the light intensity F _E at wavelength lambda _E, when it becomes F _E ≦ S _4, the processing for the through hole forming positions By ending, holes can be formed with a relatively large number of shots at positions where glass fibers are densely contained and with a relatively small number of shots at positions where glass fibers are contained sparsely. Therefore, it is possible to reduce the number of shots, shorten the processing time, and realize high-quality processing compared with the case of irradiating a laser pulse with a fixed number of shots regardless of the through-hole formation position and forming the through-hole. it can.

  FIG. 10 is a flowchart showing a laser processing method according to the eighth embodiment. The laser processing method according to the eighth embodiment corresponds to the laser processing method according to the fourth embodiment performed using the laser processing apparatus according to the first embodiment. In the eighth embodiment, the input energy after the next shot is maintained, and the number of shots from the next shot to the formation of the through hole is determined based on the ratio β. When the next shot is not incident, the number of shots after the next shot is zero.

Steps S121 to S125 are equivalent to the laser processing method according to the sixth embodiment. Further, when F _E ≦ S _4, the processing laser beam 10a is not further incident on the through hole forming position, and the processing is completed (step S132 in FIG. 10), which is also the same as in the sixth embodiment.

In the eighth embodiment, the ratio β is compared with the threshold values S ₅ and S ₆ in step S125, and if S ₅ <β, the process proceeds to step S130, and the laser pulse having a pulse energy density of 30 J / cm ² is obtained. Assume that the number of shots 10a is 2. In the case of cycle machining, two shots of the processing laser beam 10a are made incident on the through hole forming position, the process proceeds to step S132, and the machining for the through hole forming position is completed.

When S ₆ <β ≦ S ₅ and when β ≦ S ₆ , that is, when β ≦ S ₅ , the process proceeds to step S 131, and the number of shots to be shot until the end of processing for the through hole forming position is 1. To do. The processing laser beam 10a having a pulse energy density of 30 J / cm ² is made incident on that position for one more shot, the process proceeds to step S132, and the processing ends.

When S ₅ <β, the number of shots is set to 2 (step S130), and when β ≦ S ₅ the number of shots is set to 1 (step S131). Therefore, in step S125, β and the threshold S Only ₅ may be compared.

  The laser processing method according to the eighth embodiment also changes the number of shots of the processing laser beam 10a irradiated to the through-hole forming position according to the relative density of the glass fibers in the in-plane direction of the insulating layer 52. For this reason, the number of shots can be reduced, the processing time can be shortened, and high-quality processing can be realized.

Sixth through laser processing method according to the eighth embodiment, emitted from fume itself, information on the light detected by the line sensor 17 through the spectroscope 18, for example light intensity F _G at wavelength lambda _G, the wavelength lambda _E Of the glass fiber in the insulating layer 52 at the through-hole formation position, or at that position, based on the light intensity F _{E in} the light source and the ratio β of the light intensity (= F _G / F _E ) This is a laser processing method for determining the depth of a hole and controlling the total energy per unit area, which is introduced into the through hole forming position.

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

For example, in the first to fourth embodiments, the light absorptance of the epoxy resin is relatively small and the light absorptance of the wavelength λ ₁ is relatively large, but the epoxy resin is used. Alternatively, a light absorptance of light having a wavelength that is relatively large and a light absorptance of glass is relatively small may be used.

  In the first to fourth embodiments, the reference laser beam 15a is used. However, the reference beam may not be a laser beam and can be widely used as reference light.

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

  For example, the present invention can be used for laser processing in which a material constituting a processing target is decomposed and fumes are generated.

DESCRIPTION OF SYMBOLS 10 Processing laser light source 10a Processing laser beam 11 Beam shaper 12 Folding mirror 13 Galvano scanner 14 f (theta) lens 15 Reference laser light source 15a Reference laser beam 16 Filter 17 Line sensor 18 Spectrometer 20 XY stage 30 Control device 31 Storage device 50 Printed circuit board 51, 53 Conductive layer 52 Insulating layer 60 Fume

Claims (4)

A processing laser light source that emits a pulsed laser beam;
A processing object including a mixture of a first material having a relatively high workability with respect to a pulse laser beam emitted from the processing laser light source and a second material having a relatively low workability, A stage for holding a processing object having a different content ratio of the first material and the second material depending on a processing position of the processing object;
A propagation optical system for propagating a pulse laser beam emitted from the processing laser light source to an object to be processed held on the stage;
A control device for controlling the total energy per unit area, which is input from the processing laser light source to the processing position of the processing object according to the content ratio of the first material and the second material;
(I) a reference light source that emits reference light that passes through a fume that is generated when a pulse laser beam emitted from the processing laser light source is incident on a processing position of an object to be processed held by the stage; A detector that emits the reference light source and detects the reference light that has passed through the fume,
The control device is a laser processing device that controls the total energy per unit area, which is input to the processing position of the processing object, based on the amount of absorption by the fume of the reference light detected by the detector,
Or
(Ii) a detector that detects light emitted from a fume that is generated when a pulse laser beam emitted from the processing laser light source is incident on a processing position of an object to be processed held on the stage;
The control device is a laser that controls the total energy per unit area, which is emitted from the fume and is input to the processing position of the processing object based on the light intensity at a predetermined wavelength of the light detected by the detector. Processing equipment. In the laser processing apparatus of (ii),
The control device inputs the processing object to the processing position based on the ratio of the light intensity at the peak emission wavelength of the first material to the light intensity at the peak emission wavelength of the second material. The laser processing apparatus according to claim 1, wherein the total energy per unit area is controlled. (A) A processing object including a mixture of a first material having a relatively high workability with respect to a pulse laser beam emitted from a processing laser light source and a second material having a relatively low workability. A step of causing a pulse laser beam emitted from the processing laser light source to be incident on a processing target having a different content ratio of the first material and the second material depending on a processing position of the processing target;
(B) controlling the total energy per unit area, which is input from the processing laser light source to the processing position of the processing object in accordance with the content ratio of the first material and the second material. Have
(I) In the step (a), the reference light is passed through a fume generated when a pulse laser beam is incident on the workpiece, and in the step (b), the reference light is absorbed by the fume. Based on the laser processing method for controlling the total energy per unit area to be put into the processing position of the processing object,
Or
(Ii) The light emitted from the fumes generated when a pulse laser beam is incident on the workpiece in the step (a) is detected, and the light emitted from the fumes in the step (b) A laser processing method for controlling a total energy per unit area, which is input to a processing position of the processing object based on a light intensity at a predetermined wavelength. In the laser processing method of (ii),
In the step (b), based on the ratio between the light intensity at the emission peak wavelength of the first material and the light intensity at the emission peak wavelength of the second material, the processing position of the workpiece is determined. The laser processing method according to claim 3, wherein the total energy input per unit area is controlled.

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