JP5197271B2 - Laser processing apparatus and laser processing method - Google Patents

Description

  The present invention relates to a laser processing apparatus that performs processing by irradiating a workpiece with a laser beam, and a laser processing method.

  In laser drilling, a predetermined number of shots of laser pulses are incident on the resin layer of the printed circuit board to form through holes that reach the inner wiring layer. When one through hole is formed, the incident position of the laser pulse is changed using a galvano scanner to form holes at different positions on the printed circuit board. When the processing within the laser beam scanning range of the galvano scanner is finished, the stage is driven to move the printed circuit board, the laser pulse is scanned by the galvano scanner in a new processing area, and the substrate is continuously drilled.

For example, a carbon dioxide laser oscillator (CO ₂ laser oscillator) is used for laser drilling. The CO ₂ laser oscillator receives an excitation pulse (trigger pulse) and emits a laser pulse having a pulse width corresponding to the pulse width of the trigger pulse. The pulse energy of the emitted laser pulse depends on the frequency (period) of the trigger pulse and the pulse width.

In the CO ₂ laser oscillator, when the trigger pulse input is stopped and the laser pulse oscillation is stopped, the pulse energy of the laser pulse emitted immediately after the oscillation is resumed becomes unstable. For this reason, during the stage drive time, the same trigger pulse as that during processing is input to the laser oscillator to stabilize the pulse energy.

  There has also been an invention that stabilizes the pulse energy of a laser pulse by devising the laser oscillator itself (see, for example, Patent Document 1).

JP 2005-103625 A

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

  Moreover, it is providing the laser processing method which can implement | achieve a high-quality laser processing.

  According to one aspect of the present invention, when a trigger pulse is input, a laser light source that emits a laser pulse having a pulse width corresponding to the pulse width of the trigger pulse, and a laser pulse emitted from the laser light source are processed. A beam distribution unit that switches between a state that propagates along the path and a state that does not propagate along the processing path, a holder that holds a workpiece, and a laser pulse that propagates along the processing path, A beam scanner that changes a traveling direction of a laser pulse so as to be incident on a target position on an object to be processed held by the holder, and the laser light source, the beam distributor, and the beam scanner are controlled. A laser beam for processing emitted from the laser light source at a plurality of irradiated points on the object to be processed held by the holder. The laser beam is sequentially incident and laser processing is performed, and the incident position of the laser pulse for processing is moved from one irradiated point on the workpiece held by the holder to the next irradiated point. During the movement period, a non-machining laser pulse having a pulse width shorter than the pulse width of the machining laser pulse is emitted from the laser light source with a pulse width and a repetition frequency corresponding to the length of the movement period. In addition, there is provided a laser processing apparatus for controlling the laser light source, the beam distributor, and the beam scanner so that the non-processing laser pulse does not propagate along the processing path.

  According to another aspect of the present invention, a laser processing is performed by sequentially injecting laser pulses for processing to a plurality of irradiation points on a processing target while oscillating a laser oscillator, and the processing target A non-machining laser having a pulse width shorter than the pulse width of the machining laser pulse during a movement period for moving the incident position of the machining laser pulse from one irradiated point on the object to the next irradiated point There is provided a laser processing method including a step of emitting a pulse from the laser oscillator with a pulse width and a repetition frequency corresponding to the length of the moving period, and not allowing the non-processing laser pulse to enter the processing object. The

  According to the present invention, it is possible to provide a laser processing apparatus capable of realizing high-quality laser processing.

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

  FIG. 1 is a schematic diagram illustrating a laser processing apparatus according to an embodiment.

A laser light source 10, for example, a CO ₂ laser oscillator, receives an excitation pulse (trigger pulse) from the control device 17 and emits a laser pulse having a pulse width corresponding to the pulse width of the trigger pulse.

Laser pulses acousto progressing the optical path _{C a (Acoust-Optic Deflector:} AOD) incident on 11.

The AOD 11 is an optical deflector using an acousto-optic effect, and receives a control signal sent from the control device 17 and emits it by changing the traveling direction of the incident laser pulse. Laser pulses deflected by AOD11 proceeds the optical path _{C b.} If AOD11 the control signal is not applied, the laser pulses incident on AOD11 proceeds the optical path C _c and straight, enters the damper 12, is absorbed.

Laser pulses are deflected travels the optical path C _b is reflected by a folding mirror 13, after being shaped sectional shape in the mask 14 having through holes and enters the galvano scanner 15. The galvano scanner 15 includes two oscillating mirrors, and scans and emits incident laser pulses in a two-dimensional direction.

  On the XY stage 18, for example, a printed circuit board 20 in which an inner wiring layer is embedded in a resin layer is held. The laser pulse emitted from the galvano scanner 15 passes through the fθ lens 16 and enters the resin layer of the printed circuit board 20 held on the XY stage 18. The fθ lens 16 causes the laser pulse to enter the printed board 20 perpendicularly.

  A hole is formed in the resin layer of the printed circuit board 20 by irradiation with the laser pulse. For example, by making a three-shot laser pulse incident on the same position, a through-hole penetrating the resin layer and reaching the inner wiring layer is formed. The pulse width of the laser pulse used for forming the through hole is, for example, 20 to 100 μs.

  After a through hole is formed at a certain target position, the galvano scanner 15 is driven to cause a laser pulse to enter the next target position, and a new through hole is formed at that position.

  When processing within the laser pulse scanning range of the galvano scanner 15 is finished, the XY stage 18 is driven to move the printed circuit board 20, and scanning of the laser pulse is performed by the galvano scanner 15 in a new processing area. Opening is performed. The drilling process is performed by sequentially irradiating a plurality of processing points defined on the printed circuit board 20 with laser pulses.

  The control device 17 controls driving of the galvano scanner 15 and the XY stage 18 so that a through hole is formed at the target position.

  With reference to the timing charts shown in FIGS. 2A to 2F, the laser processing method according to the embodiment will be described. 2A to 2F all represent time.

  2A and 2D show on and off timings of positioning signals (signals for instructing positioning of laser pulse incident positions on the printed circuit board 20) transmitted from the control device 17 to the galvano scanner 15. FIG. Show. 2B and 2E show the input timing of the excitation pulse (trigger pulse) input to the laser light source 10. Further, FIGS. 2C and 2F show application timings of control signals applied to the AOD 11.

  2A to 2C represent control in a time zone in which the timing charts shown in FIG. In addition, the timing charts shown in FIGS. 2D to 2F are a set and represent control in other time zones.

  Reference is made to FIG. As described above, for example, after forming a hole by injecting a 3-shot laser beam for processing into a resin layer at a certain position of the printed circuit board 20, when forming a hole at another position of the printed circuit board 20, the galvano scanner 15 is driven to position the incident position of a new machining laser pulse.

A positioning signal is transmitted from the control device 17 to the galvano scanner 15 during a period indicated by “ON” in FIG. In response to the positioning signal, the galvano scanner 15 starts positioning of a position where a processing laser pulse is newly incident. The positioning of the galvano scanner 15 is completed after the galvano settling waiting time t ₁ after the positioning signal becomes “OFF”.

  Reference is made to FIG. In the laser processing method according to the embodiment, after irradiating a certain position of the printed circuit board 20 to perform drilling, a three-shot processing laser pulse is emitted, and then irradiated to another position of the printed circuit board 20 to form the next hole. The laser light source 10 emits a plurality of irradiating laser pulses during a period until the three-shot machining laser pulse for machining is emitted. For this reason, for example, while the galvano scanner 15 is being driven (during the positioning period), a plurality of throwing laser pulses are emitted from the laser light source 10.

  The throwing laser pulse has a shorter pulse width than the processing laser pulse. As shown in the figure, the emission laser pulse is emitted by inputting an excitation pulse (trigger pulse) for generating the emission laser pulse from the controller 17 to the laser light source 10.

In this figure, the time from the fall of the laser pulses for one discarded out until rises laser pulses for the next discarded out, shown as a laser pulse duty guarantee time t ₂ for out discarded.

Processing laser pulses previously (galvano settling waiting time after t ₁ from the positioning signal becomes "OFF") positioning completion of the galvano scanner 15 is not emitted. The positioning after completion of the galvanometer scanner 15, the laser-pulse among discarded is not emitted, after a time t ₂ from the falling time of the last discarded out laser pulses, the processing laser pulse is emitted.

Reference is made to FIG. A control signal is applied to the AOD 11 after the emission laser pulse is emitted and before the processing laser pulse is emitted. Thus, after entering the discard out laser pulses AOD11, but proceed to the optical path C _c is absorbed by the damper 12, the processing laser pulse is deflected at AOD11, the printed circuit board 20 by traveling the optical path C _b Incident and form a hole in the resin layer.

  Reference is made to FIG. This figure shows a case where the driving time (positioning time) of the galvano scanner 15 is different from that in FIG.

Reference is made to FIG. Discard of which laser pulses are emitted laser pulse duty guarantee time for out discarded as t _3. As in the case shown in FIG. 2B, the processing laser pulse is not emitted before the positioning of the galvano scanner 15 is completed. The positioning after completion of the galvanometer scanner 15, the laser-pulse among discarded is not emitted, after a time t ₃ from the falling time of the last discarded out laser pulses, the processing laser pulse is emitted.

After the three-shot machining laser pulse is emitted, driving of the galvano scanner 15 (positioning of the laser pulse incident position) is started so that the next emitted machining laser pulse is incident on a new target position. . The discarding laser pulse is emitted after the processing laser pulse duty guarantee time t _{4 has} elapsed from the falling edge of the third shot processing laser pulse.

Reference is made to FIG. The control signal to the AOD 11 is turned on while the processing laser pulse is incident on the AOD 11, and is turned off when the disposal laser pulse is incident on the AOD 11. For this reason, the processing laser pulse is deflected by the AOD 11, travels along the optical path C _b and enters the printed circuit board 20 to form a hole in the resin layer, but the throwing laser pulse enters the AOD 11 and then enters the optical path C. _{The c} travels and is absorbed by the damper 12.

  The laser processing method according to the embodiment is not limited to simply emitting a laser beam for throwing between a hole at a certain position and a hole at the next position. Depending on the time from when the first shot laser pulse for forming a hole at a certain position is emitted until the first shot laser pulse for forming a hole at the next position is emitted) Thus, the present invention is characterized in that the pulse width and repetition frequency of the throwing laser pulse are changed. The time between drilling corresponds to the driving time of the galvano scanner 15 (positioning time of the laser pulse incident position).

  The driving time of the galvano scanner 15 (positioning time of the laser pulse incident position) depends on, for example, the distance between the laser pulse incident position of the current machining and the laser pulse incident position of the next machining, and the driving speed of the galvano scanner 15. If the distance between the current processing and the next processing laser pulse incident position is long, the driving time of the galvano scanner 15 (positioning time of the laser pulse incident position) becomes long. For this reason, “change the pulse width and repetition frequency of the laser pulse for throwing shot according to the time between drilling” means “for throwing shot according to the distance between the laser pulse incident position of the current machining and the next machining. The content of “changing the pulse width and repetition frequency of the laser pulse” is included.

  In the case where the discarding laser pulse is not emitted, the pulse energy of the machining laser pulse emitted immediately after the end of the positioning period is larger than that of the machining laser pulse emitted continuously. In addition, when the laser beam for throwing is not emitted, there is a correlation between the length of the positioning time and the magnitude of the pulse energy of the machining laser pulse immediately after the end of the positioning period, and the pulse energy increases as the positioning time increases. Will grow.

The inventor of the present application determines that the pulse energy Z of the processing laser pulse emitted first after the end of the positioning period depends on the pulse width and repetition frequency of the laser pulse for throwing off,
Z = α−β · X + γ · Y (1)
It was found that

  Here, X is the pulse width of the throwing laser pulse, and Y is the repetition frequency of the throwing laser pulse. Α, β, and γ are constants of 0 or more that are determined according to the time between drilling operations, and take different values depending on the time between drilling operations.

  Here, α, β, and γ are obtained by the following procedure, for example. First, the pulse width of a processing laser pulse necessary for drilling is determined. The pulse width is 100 μs, for example. Next, a hole drilling experiment is performed by changing the drive time of the galvano scanner 15 (positioning time of the laser pulse incident position), the pulse width of the throwing laser pulse, and the repetition frequency, and the pulse energy Z of the laser pulse for machining is changed. Measure. At this time, the driving time of the galvano scanner 15 (positioning time of the laser pulse incident position) can be approximated by the time between drilling.

  For example, 2 ms, 1 ms, 0.67 ms, 0.5 ms, 0.4 ms as the time between drilling, 2 μs, 5 μs, 8 μs as the pulse width of the throwing laser pulse, and the repetition frequency of the laser pulse for the throwing shot 10 kHz, 12.5 kHz, and 15 kHz are employed, and the conditions are combined.

  Finally, multiple regression analysis is performed using the pulse energy Z obtained in the drilling experiment to obtain α, β, and γ.

  After determining α, β, and γ as described above, the pulse width X and the repetition frequency Y of the laser beam for throwing away in actual drilling are determined according to the time between drilling using the above formula (1). For example, the pulse energy Z of the processing laser pulse is determined so as to be a constant value suitable for performing the drilling process on the printed circuit board 20.

  For example, the pulse width X and the repetition frequency Y of the laser beam for disposal are determined so that the pulse energy Z of the processing laser pulse becomes 0.135 J / pulse on the printed circuit board 20. For example, when the pulse width of the machining laser pulse is 100 μs, the repetition frequency Y is set to 10 kHz, and the values of α, β, and γ calculated by the inventor for each time between drilling operations are substituted into equation (1). Thus, if the time between drilling is 2 ms, 1 ms, 0.67 ms, and 0.5 ms, the pulse width X of the laser beam for throwing is set to 7 μs, 8 μs, 7 μs, and 2 μs, respectively. The pulse energy Z can be 0.135 J / pulse on the printed circuit board 20.

  When the pulse width of the throwing laser pulse is increased, the guaranteed laser pulse duty guarantee time must be increased. For this reason, the time from the end of driving the galvano scanner 15 (positioning of the laser pulse incident position) to the emission of the processing laser pulse also becomes longer. As a result, when the pulse width of the throwing laser pulse is too long, there is a demerit that a long time is required for processing.

  The pulse width X and repetition frequency Y of the throwing laser pulse are set in advance so that, for example, the pulse energy Z of the laser pulse for machining becomes a constant value suitable for drilling according to the time between drilling. It is determined and stored in the storage area of the control device 17 in association with the time between drilling. That is, the control device 17 is provided with a conversion table in which the pulse width X and the repetition frequency Y of the laser beam for discarding are referenced based on the time between drilling. This conversion table refers to X and Y based on the driving period of the galvano scanner 15 (positioning period of the laser pulse incident position) and the distance between the laser pulse incident position of the current process and the next process. Also good. The control device 17 inputs an excitation pulse (trigger pulse) to the laser light source 10 based on the conversion table.

  The laser processing method according to the embodiment can stabilize the pulse energy of the processing laser pulse regardless of the drive time of the galvano scanner 15 (positioning time of the laser pulse incident position). For this reason, high-quality laser processing can be realized.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

  It can be suitably used for laser processing in general, for example, drilling performed by irradiating a laser beam.

It is the schematic which shows the laser processing apparatus by an Example. (A)-(F) are timing charts for demonstrating the laser processing method by an Example.

Explanation of symbols

10 Laser light source 11 AOD
12 Damper 13 Folding Mirror 14 Mask 15 Galvano Scanner 16 fθ Lens 17 Control Device 18 XY Stage 20 Printed Circuit Board

Claims (5)

When a trigger pulse is input, a laser light source that emits a laser pulse having a pulse width corresponding to the pulse width of the trigger pulse;
A beam splitter for switching between a state in which the laser pulse emitted from the laser light source is propagated along the processing path and a state in which the laser pulse is not propagated along the processing path;
A cage for holding a workpiece;
A beam scanner that changes the traveling direction of the laser pulse so that the laser pulse propagating along the processing path is incident on a target position on the workpiece held by the holder;
A control device for controlling the laser light source, the beam distributor, and the beam scanner;
The control device performs laser processing by sequentially applying a processing laser pulse emitted from the laser light source to a plurality of irradiated points on a processing object held by the cage, and Shorter than the pulse width of the machining laser pulse during the movement period for moving the incident position of the machining laser pulse from one irradiated point on the workpiece held by the cage to the next irradiated point. A non-processing laser pulse having a pulse width is emitted from the laser light source at a pulse width and a repetition frequency corresponding to the length of the moving period, and the non-processing laser pulse propagates along the processing path. A laser processing apparatus for controlling the laser light source, the beam distributor, and the beam scanner.   The control device refers to a conversion table in which a pulse width and a repetition frequency of the non-processing laser pulse are referred to based on a distance between the one irradiated point and the next irradiated point or the moving period. The laser processing apparatus according to claim 1, comprising: A step of performing laser processing by sequentially injecting laser pulses for processing to a plurality of irradiated points on a processing target while oscillating a laser oscillator; and
In a moving period for moving the incident position of the processing laser pulse from one irradiated point on the processing object to the next irradiated point, a non-width having a pulse width shorter than the pulse width of the processing laser pulse. A laser processing method including a step of emitting a processing laser pulse from the laser oscillator at a pulse width and a repetition frequency corresponding to the length of the moving period, and not allowing the non-processing laser pulse to enter the processing target . The laser processing method according to claim 3 , wherein the laser oscillator is a laser oscillator that emits a laser pulse having a pulse width corresponding to a pulse width of the trigger pulse when a trigger pulse is input. 5. The pulse width and repetition frequency of the non-machining laser pulse are set such that the pulse energy of the machining laser pulse that is first emitted after the moving period ends has a constant value. Laser processing method.

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