JP2864005B2 - Laser machining compensation system by detecting total pulse energy integration - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing apparatus using a pulsed laser beam, and more particularly to a laser processing method suitable for providing through holes, via holes, and grooves in a substrate body such as a printed wiring board (including a flexible printed wiring board). The present invention relates to a laser processing compensation system that detects an integrated amount of total pulse energy and compensates for a temporary decrease in pulse energy for an apparatus.

[0002]

2. Description of the Related Art Recently, there has been provided a laser processing apparatus for providing via holes and grooves in a printed wiring board, particularly a substrate body such as a high-density multilayer printed wiring board using a pulsed laser beam. As shown in FIG. 4, this type of laser processing apparatus guides a pulsed laser beam generated by a laser oscillator 31 via reflection mirrors 32, 33, and 34, and passes the pulsed laser light through a processing lens 35 also called an fθ lens.
6 is processed by irradiation.

FIG. 5 is an enlarged view of a part of a printed wiring board 36. A pulse laser is provided on the other surface of a substrate body 36-2 having a metal film 36-1 (usually a land portion of a conductor pattern) on one surface. By irradiating light, the substrate body 36-
2, a via hole 36-3 is formed. For example, when a hole is made in a substrate body made of an insulating resin such as polyimide or glass epoxy, a TEA-CO ₂ laser is used.
Since it is possible to make a 40-50 μm thick hole with a pulse,
If the thickness is 0.1 mm, drilling can be performed with a few pulses.

Some laser oscillators have a built-in power meter for stabilizing the output, and this will be described with reference to FIG. In FIG.
The laser oscillator 40 includes a laser oscillation unit 41, a power supply unit 42, a partially reflecting mirror 43, and a power meter 44. The power meter 44 determines the output by receiving a part of the pulse laser beam, and the determination result is sent to the power output monitor 50. The power output monitor 50 controls the power supply section 42 based on this determination result.

[0005] Explaining with an example, 3 (msec)
When one pulse is generated every time, those powers are monitored for all the pulses by the power meter 44 and finally 1 (se
Calculate the average power during c). The average power is fed back to the power supply section 42 through the power output monitor 50, so that the average power per 1 (sec) is controlled to be uniform.

[0006]

However, in a laser processing apparatus using a laser oscillator as described above, energy loss occurring in an optical path after emission from the laser oscillator cannot be detected, and the output of the laser oscillator cannot be detected. Not reflected in control.

In addition, since the average power is calculated and fed back every 1 (sec), one to two pulses are required for precise laser processing in which one operation is completed in a short time, for example, several pulses. When the pulse energy fluctuates, it cannot be covered completely, resulting in processing failure.

An object of the present invention is to provide a laser processing compensation system which can monitor pulse energy for each pulse laser beam and can compensate for a decrease in pulse energy when the pulse energy decreases. .

[0009]

SUMMARY OF THE INVENTION A laser processing compensation system according to the present invention is provided on an optical path for guiding a pulse laser beam from a laser oscillator. It is possible to set a threshold value related to energy determined by the number of pulses per one processing set according to the threshold value and the set threshold value and the pulse energy detected by the energy monitor per one processing. An energy comparison unit that compares the integrated value of the number of pulses with the integrated value and outputs a detection signal when the integrated value is lower,
A trigger pulse generator for outputting a trigger pulse to the laser oscillator when the detection signal is received from the energy comparator and generating an additional pulse laser beam from the laser oscillator.

The energy comparing section outputs the detection signal until the integrated value becomes equal to or larger than the threshold value, and the trigger pulse generating section outputs the trigger pulse until the detection signal disappears.

The energy monitor is configured to receive a part of the pulsed laser light through a partially transmitting bending mirror provided in an optical path closer to a workpiece in the optical path. I have.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 to 3, a case of a processing apparatus for making a hole in a printed wiring board will be described.
A preferred embodiment of the present invention will be described. In FIG. 1, a thick line indicates a path of an electric signal, and a thin line indicates a path of a laser beam. The pulse laser beam generated by the laser oscillator 11 reaches a partially transmitting bending mirror 13 via a reflection mirror 12, where about 99% is reflected and X-rays.
The light is irradiated onto a printed wiring board 17 mounted on an XY table 16 through a Y scanner 14 and a processing lens 15 formed by an fθ lens.

Referring to FIG. 2, the XY scanner 14 is
This is for oscillating the pulse laser beam, and is a reflection mirror 14-1 or 14-2 called two galvanometer mirrors.
Is called a galvano scanner. That is, by rotating the two reflection mirrors 14-1 and 14-2 independently based on the driving principle of the galvanometer, it is possible to irradiate an arbitrary position on the printed wiring board 17 with the pulse laser light.

Returning to FIG. 1, the built-in driving unit of the XY scanner 14 is controlled by a control signal from a control device 20. Control device 20 is generally realized by a personal computer. The positions of a plurality of holes provided in the printed wiring board 17 positioned and mounted on the XY table 16 are predetermined, and a control program for sequentially irradiating the positions of these holes with pulsed laser light is controlled in advance by the control device. It is set to 20. XY scanner 14
Irradiates a predetermined number of pulsed laser beams on the printed wiring board 17 in sequence according to a control signal from the control device 20.

The XY table 16 also has a built-in drive unit controlled by a control signal from the control device 20 to be driven in the X-axis direction-Y-axis direction.

On the other hand, about 1% of the laser light transmitted through the bending mirror 13 is introduced into an energy monitor 18 and pulse energy is detected for each pulse. The detected pulse energy is sent to the energy comparison circuit 19.

In the energy comparing circuit 19, the pulse energy from the energy monitor 18 is accumulated for the number of pulses per processing. When the material and processing thickness of the printed wiring board 17 are determined, the number of pulses required to make a hole in the printed wiring board 17 is also determined. Therefore, the number of pulses to be accumulated may be set. In the energy comparison circuit 19, a threshold value for comparison with the stored pulse energy is set. This threshold value can also be arbitrarily changed according to processing conditions, for example, the number of pulses per processing determined by the material and processing thickness of the printed wiring board 17.

The energy comparing circuit 19 compares the accumulated pulse energy with the threshold value, and if the accumulated pulse energy is equal to or larger than the threshold value, the drilling operation is normally performed on the control device 20. A processing completion signal indicating that the operation has been completed is output. When receiving the processing completion signal, the control device 20 sends a drive control signal to the XY scanner 14 to perform the next drilling processing.

On the other hand, when the stored pulse energy is lower, a detection signal indicating the lower is generated by the trigger pulse generator 2.
Output to 1. Upon receiving this detection signal, the trigger pulse generator 21 outputs a trigger pulse to the laser oscillator 11,
Only one additional pulsed laser beam is generated.

The above operation will be described with reference to FIG. 3 using specific numerical values. The number of pulsed laser beams per operation is determined by the processing conditions. For example, 0.4
The pulse laser beam having the pulse energy of (J) is used to irradiate six pulse laser beams for one drilling operation. Assuming that there is no energy loss in the optical path, the detected value of the normal pulse energy at the energy monitor 18 is 4 (mJ). In view of this, 4 × as threshold value V _SL 6 × 0.8 (80
%) = 19.2 (mJ). In the first drilling, the first to sixth pulsed laser light P
1~P6 Both normal accumulation value of the energy exceeds a threshold value V _SL, the printed wiring board 1
7, a via hole is normally formed.

In the second drilling, the fourth and fifth pulsed laser beams P1 caused by the laser oscillator 11
0, P11 are both pulse energy is low, when the accumulation value of the pulse energy of the pulsed laser beam P7~P12 is below the threshold value V _SL, holes formed in the printed wiring board 17 is not a via hole. Energy comparison circuit 19 detects and outputs a detection signal to the trigger pulse generator 21 to the pulse energy is below the threshold value V _SL. Upon receiving this detection signal, the trigger pulse generator 21 outputs a trigger pulse to the laser oscillator 11. Upon receiving this trigger pulse, the laser oscillator 11 outputs an additional pulse laser beam P13 at the same period as the normal pulse laser beam. As a result, the accumulation value of the pulse energy of the pulsed laser light P7~P13 exceeds the threshold value V _SL, the printed wiring board 1
7, a via hole is normally formed.

[0022] If the accumulated value of the pulse energy also additional pulsed laser beam P13 unless exceeds the threshold value V _SL, are generated more additional pulsed laser beam. This is continued until the accumulated value of the pulse energy exceeds the threshold value V _SL , during which the control device 20 stops sending the control signal to the XY scanner 14 for the next drilling operation. I have. In this way, via holes are normally formed in the printed wiring board 17.

The preferred embodiment of the present invention has been described above.
In consideration of the energy loss in the optical path of the pulsed laser beam, it is preferable to set the lowest position on the portion to be processed, that is, the printed wiring board 17 before the XY scanner 14. As the energy monitor 18, there is a so-called joule meter operable at about 1% of the pulse energy of the pulsed laser light. This is a photodiode type in which a part of the pulsed laser light is taken out and the light amount is measured. There is a voltage method in which ΔV is measured by extracting a part of the pulse laser light and performing polarization, and any of them can be used.

[0024]

As described above, according to the present invention, when the pulse energy of the pulse laser beam is temporarily reduced, this is detected and an additional pulse laser beam is generated, and the pulse energy in one laser processing is obtained. By increasing the number of laser beams, the occurrence of processing defects can be prevented, and the processing yield can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a laser processing apparatus to which the present invention is applied.

FIG. 2 is a schematic configuration diagram of the XY scanner shown in FIG.

FIG. 3 is a waveform chart for explaining an operation at the time of drilling by the apparatus of FIG. 1;

FIG. 4 is a block diagram illustrating a schematic configuration of a conventional laser processing apparatus.

FIG. 5 is a cross-sectional view for explaining drilling by the apparatus of FIG. 4;

FIG. 6 is a diagram for explaining a power monitoring method in a conventional laser oscillator.

[Explanation of symbols]

 12, 32, 33, 34 Reflecting mirror 13 Partially transmissive bending mirror 15, 35 Processing lens 17, 36 Printed wiring board

Claims (3)

(57) [Claims] 1. A laser processing apparatus for performing processing using pulsed laser light from a laser oscillator, comprising: an energy monitor provided on an optical path for guiding the pulsed laser light for detecting pulse energy per laser; It is possible to set a threshold value related to energy determined by the number of pulses per one processing set according to the threshold value and the set threshold value and the pulse energy detected by the energy monitor per one processing. An energy comparison unit that compares the integrated value for the number of pulses and outputs a detection signal when the integrated value is lower, and outputs a trigger pulse to the laser oscillator when receiving the detection signal from the energy comparison unit. A trigger pulse generator for generating additional pulsed laser light from the laser oscillator. A laser processing compensation system, characterized in that: 2. The energy comparison unit outputs the detection signal until the integrated value becomes equal to or more than the threshold value, and the trigger pulse generation unit outputs the trigger pulse until the detection signal disappears. The laser processing compensation system according to claim 1, wherein: 3. The energy monitor is configured to receive a part of the pulse laser beam through a partially transmitting bending mirror provided in an optical path closer to a workpiece in the optical path. The laser processing compensation system according to claim 1, wherein: