JP2000117475A - Method for laser beam machining - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for laser beam machining enabling positioning of galvanomirror in a short time and improving productivity. SOLUTION: While a difference between a target rotation angle of a galvanomirror 4 and an actual rotational moving angle is being detected by an angular difference detecting part, through feedback control based on the difference, the galvanomirror 4 is positioned at the target rotation angle and then laser beam is projected; at this time, a gain of the angular difference detecting part is set so that an overshoot may generate, and at the time of overshoot a target rotion angle is set so that the galvanomirror 4 may have an optimum rotation angle, and thus laser beam is projected at the time of overshoot. Thereby, the positioning of galvanomirror 4 is made in a short time and productivity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to general high-speed positioning control using a galvanometer. In particular, the present invention relates to a laser hole processing method that requires high-speed positioning of a galvanometer, and more particularly, to a method of processing a hole by irradiating a circuit board or the like with a laser through a mirror attached to the galvanometer.

[0002]

2. Description of the Related Art In a work for forming a hole such as a through hole in a circuit board having a high-density wiring, a laser hole processing technique using a galvanomirror is employed.

[0003] The laser drilling technique is a method of irradiating a workpiece with a laser beam and melting or evaporating the workpiece with the energy of the laser beam to form a hole. Suitable for processing into The number of holes per unit area in high-density wiring circuit boards, which represent recent electronic devices such as mobile phones, has been increasing due to the miniaturization of holes and the densification of boards. In order for the laser drilling technology to be widely used in the manufacture of substrates, it is essential to increase the speed of drilling.

As a specific example of a hole drilling technique using a galvanometer mirror in which a mirror is attached to a galvanometer,
As disclosed in Japanese Patent Application Laid-Open No. 8-174256 filed by the present applicant, a laser beam is reflected by a galvanomirror, collected by a condensing lens, and applied to a circuit board to be processed. The laser processing is performed by irradiation.

A galvanometer used for such a hole drilling technique has a high resolution of the order of μrad, a driving range of an optical angle of ± 20 ° and high-speed positioning characteristics, and a capacitance capable of detecting a minute angle. A sensor is provided as position detection means, and positioning is performed by analog feedback control of a servo system.

[0006] Specifically, when a command to move to the galvanometer is given from the control unit, as shown in FIG.
While controlling the actual rotation angle so that it does not exceed the target rotation angle, the galvanometer is controlled to rotate gradually so as to gradually approach the target rotation angle. To perform laser processing.

Here, Mv in FIG. 4 is a moving time during which the target rotation angle is varied as a movement command to the galvanometer mirror, Jd is a positioning time until the galvanometer mirror moves to the target rotation angle and is positioned thereafter,
Lon is the irradiation time of the laser beam, and Sd is the laser wave tail waiting time.

Since the capacitance sensor is output as a minute analog signal and cannot be used to determine the completion of target positioning due to the influence of noise or the like, the determination of completion of target positioning is actually made by a galvanometer in feedback control. A waiting time of a predetermined time is set as the positioning time Jd from the time when the movement of the movement command to the mirror ends (the end point of the moving time Mv), and when the positioning time Jd elapses, it is determined that positioning is completed, Laser beam irradiation has started.

[0009]

However, according to the above-mentioned conventional laser processing method, the galvanometer is controlled to rotate so as to gradually approach the target rotation angle, and is positioned after the target rotation angle is reached and stabilized. Therefore, the positioning of the galvanomirror takes a relatively long time, and there is a problem that the processing capacity is not increased and the productivity is not improved.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a laser processing method which can position a galvanomirror in a short time and improves productivity.

[0011]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a method for reflecting a laser beam on a galvanomirror,
This is a laser processing method that performs laser processing by condensing with a condenser lens and irradiating the object to be processed with a difference between a target rotation angle of a galvanometer mirror and an actual rotation movement angle detected by an angle difference detection unit. When performing the feedback control based on this difference and positioning the galvanomirror at the target rotation angle and irradiating the laser beam, the gain of the angle difference detection unit is set so that overshoot occurs, and at the time of overshoot. A target rotation angle is set so that the galvanomirror has an optimum rotation angle, and a laser beam is irradiated at the time of overshoot.

According to this method, the galvanomirror can be positioned in a short time, and the productivity is improved.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to claim 1 is a laser processing method for performing laser processing by reflecting a laser beam by a galvanometer mirror, condensing the laser beam by a condenser lens, and irradiating the laser beam on an object to be processed. Then, the difference between the target rotation angle of the galvanomirror and the actual rotational movement angle is detected by the angle difference detection unit, and based on this difference, feedback control is performed to position the galvanomirror at the target rotation angle and to position the laser beam. When irradiating, the gain of the angle difference detection unit is set so that an overshoot occurs, a target rotation angle is set such that the galvanomirror has an optimum rotation angle during the overshoot, and the laser beam is emitted during the overshoot. Irradiation.

According to this method, instead of waiting for the galvanomirror to reach the target rotation angle and stabilize as in the prior art, the laser beam is irradiated at the time of overshoot. The speed of the feedback control system composed of analog servos can be increased with higher accuracy than the optimal design.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, a case where the present invention is used for a laser processing apparatus for processing a hole such as a through hole in a circuit board having high-density wiring will be described.

As shown in FIG. 1, a laser processing apparatus comprises a laser oscillator 2 for emitting a laser beam 1 and a laser beam 1
Beam splitter 3 for branching the beam and galvanometer 4
a galvano mirror 4 having a mirror 4b attached to a
An Fθ lens 5 as a condensing lens for condensing the laser beam 1 on a plane, and an XY lens movably movable in the X-axis direction and the Y-axis direction, on which a circuit board as a workpiece 6 is placed.
It is basically constituted by a table 7.

The XY table 7 is positioned at the command position and the galvanomirror 4 is positioned at the command position in order to make a hole at an arbitrary position on the workpiece 6 placed on the XY table 7. After that, the laser beam 1 is irradiated from the laser oscillator 2 to perform the hole processing. By positioning the galvanomirror 4, 50
Holes can be drilled at any point in the
The table 7 moves in units of 50 mm, and
It is configured so that an arbitrary position on the workpiece 6 of mx 350 mm can be machined.

In the laser processing apparatus shown in FIG. 1, a laser beam is split by a beam splitter 3, and two pairs of galvanometer mirrors 4 and an Fθ lens 5 are arranged.
By placing two pairs of workpieces 6 on the table 7,
Simultaneous processing on a plurality of workpieces 6 is realized.

By the way, the circuit board of high-density wiring, which is representative of electronic equipment such as a cellular phone, has recently been manufactured with 1000 holes per 50 mm × 50 mm due to finer holes and higher density of circuit boards. The entire circuit board has more than 50,000 holes, and the positioning time of the galvanomirror 4 greatly affects the processing tact of one workpiece.

Therefore, in the present invention, the control system relating to the galvanometer mirror 4 is shown in FIG. 2, and as shown in the control method in FIG. 3, the gain of the galvano driver 8 for performing the analog feedback control is increased to cause overshoot. , To shorten the positioning arrival time. Regarding the position deviation of the overshoot relative to the target value, the moving distance, the amount of overshoot, and the peak time are measured and added to the command value while the output gain is increased in advance. The galvanomirror 4 is controlled by the host controller 10 as a control unit so that the target is positioned. In FIG. 3, Mv is a movement time during which the target rotation angle is varied as a movement command for the galvanometer mirror 4, Jd is a positioning time until the galvanometer mirror 4 moves to the target rotation angle and is positioned, Lon. Is the irradiation time of the laser beam, Sd
Is the laser wave tail waiting time.

That is, the difference between the actual rotation angle of the galvanometer mirror 4 detected by the capacitance sensor 9 as the position detection means and the target rotation angle of the galvanometer mirror 4 is determined by the galvanometer functioning as an angle difference detector. While calculating by the driver 8, feedback control is performed based on this difference to set the galvanomirror 4 to the target rotation angle and set the gain of the galvano driver 8 so that overshoot occurs when irradiating the laser beam. . Also, with the output gain increased, the galvanomirror 4
, The overshoot amount, and the overshoot peak time are measured in advance and stored. Further, at the time of overshoot, data is extracted so as to have an optimal rotation angle at which the galvanometer mirror 4 should be rotated, and a rotation angle corresponding to the extracted data is set as a target rotation angle. Then, in this way, a command considering the amount of overshoot is issued, control is performed so as to generate overshoot, and the laser beam is irradiated at the peak time of overshoot. Thus, the positioning time Jd can be reduced while ensuring the positioning accuracy of the galvanometer mirror 4.

By using the present invention in this laser processing apparatus, the processing time per hole can be reduced by about 100 μS.
With one 50,000-hole work, the time can be reduced by 5 seconds.

[0023]

As described above, according to the present invention, instead of waiting for the galvanomirror to reach the target rotation angle and stabilize as in the prior art, the laser beam is irradiated at the time of overshoot. It is possible to shorten the feedback control, and it is possible to expect a higher speed than the optimal design of the feedback control system constituted by the analog servo of the galvanometer, which has been difficult to improve, and to secure the positioning accuracy.

[Brief description of the drawings]

FIG. 1 is a perspective view of a laser processing apparatus that performs a laser processing method according to an embodiment of the present invention.

FIG. 2 is a diagram showing a galvanomirror control system of the laser processing apparatus.

FIG. 3 is a view conceptually showing the laser processing method.

FIG. 4 is a diagram conceptually showing a conventional laser processing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser beam 2 Laser oscillator 4 Galvanometer mirror 4a Galvanometer 4b Mirror 5 Fθ lens (condensing lens) 6 XY table 7 Workpiece 8 Galvano driver 9 Capacitance sensor (position detecting means) 10 Host controller (control unit)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 3/00 H05K 3/00 N

Claims (1)

[Claims] 1. A laser processing method for performing laser processing by reflecting a laser beam by a galvanomirror, condensing the laser beam by a condenser lens, and irradiating the laser beam to an object to be processed. A difference from the rotational movement angle is detected by an angle difference detection unit, and a feedback control is performed based on the difference to position the galvanomirror at a target rotation angle and irradiate a laser beam. A laser processing method in which overshoot is set, a target rotation angle is set such that the galvanomirror has an optimum rotation angle during overshoot, and a laser beam is irradiated during overshoot.