JP7579735B2 - Laser Processing Equipment - Google Patents

Description

The present invention relates to a laser processing device for drilling holes using a laser, for example, in a printed circuit board.

In laser processing equipment, as described in, for example, Patent Documents 1, 2, and 3, it is necessary to measure the power of the laser beam emitted from the laser oscillator in order to check whether the power is at a target value and to adjust it. Here, power means the average energy of the laser beam per unit time. Power is measured by irradiating a power sensor with laser light. A thermoelectric power sensor (thermal sensor) is often used as the power sensor used for the measurement.

A thermoelectric power sensor irradiates a laser onto the light receiving part of the sensor and measures the power based on the temperature change of the light receiving part. More specifically, the laser light is converted into heat in the light receiving part, and the temperature rise is converted into a voltage to measure the power.

JP 2020-006438 A JP 2003-124552 A JP 2019-038000 A

It is known that with thermoelectric power sensors, it takes time for the sensor output to stabilize even when the laser to be measured is irradiated. This is because it takes time for the light receiving part of the power sensor to reach thermal equilibrium. As a result, in order to obtain an accurate measurement value, it is necessary to wait for several tens of seconds until the output stabilizes.

In recent years, the increasing sophistication of printed circuit boards has led to increased demands for more advanced and stable processing precision, making it necessary to measure power frequently. Although the waiting time for each measurement is not particularly long, an increase in the number of measurements increases the waiting time for the entire processing process, creating problems in terms of production efficiency.

Therefore, the present invention aims to improve production efficiency by shortening the time it takes to measure laser power.

Among the inventions disclosed in this application, a representative laser processing apparatus is as follows: A laser processing apparatus that causes a laser beam emitted from a laser oscillator to be incident on a workpiece for processing, comprising a thermoelectric power sensor that measures the power of the laser beam emitted from the laser oscillator, and a heating unit that heats the light receiving unit of the thermoelectric power sensor, and is characterized in that the heating unit heats the light receiving unit of the thermoelectric power sensor to a temperature corresponding to a target value of laser power when the thermoelectric power sensor is not measuring the power of the laser beam.

According to the present invention, it is possible to shorten the time required for each laser measurement, thereby improving the production efficiency of the entire laser processing process.

1 is a block diagram of a laser processing apparatus according to an embodiment of the present invention. FIG. 2 is a diagram for explaining a heating unit of the laser processing apparatus according to the embodiment of the present invention, in which the heater is in a position when the laser power is not being measured. FIG. 2 is a diagram for explaining a heating unit of the laser processing apparatus according to the embodiment of the present invention, in which the heater is in a position for measuring laser power. FIG. 4 is a diagram showing heating timing in an embodiment of the present invention.

A representative embodiment of the present invention will be described with reference to the drawings. Figure 1 is a block diagram of a laser processing device according to an embodiment of the present invention.

In FIG. 1, 1 is a printed circuit board, which is the workpiece, and 2 is a thermal sensor that measures laser power. A light-absorbing member 21 is disposed on top of the thermal sensor 2, which functions as a light-receiving unit that receives the incident laser light to be measured and converts it into heat. The thermal sensor 2 converts the laser power into heat using the light-absorbing member 21, measures the power by converting the temperature rise into a voltage, and outputs a signal according to the measured value.

31 is a heater for heating the thermal sensor, 32 is a heater holder that holds the heater 31 on its underside, and 33 is a heater drive device that drives and supports the heater 31 and the heater holder 32. 3 is a heating unit that includes the heater 31, heater holder 32, and heater drive device 33, and 4 is a table on which the printed circuit board 1, thermal sensor 2, and heating unit 3 are placed.

5 is a laser oscillator that emits laser pulse L1, 6 is an AOM that splits the laser pulse L1 into two directions, the processing direction and the non-processing direction, and modulates the laser pulse L1 to the beam power required for processing. 7 is a damper that absorbs the laser pulse L3 split in the non-processing direction in the AOM 6, and 8 is a galvano scanner that scans the laser pulse L2 split in the processing direction in the AOM 6 and sequentially irradiates the hole drilling position on the printed circuit board 1. This galvano scanner 8 rotates to scan the laser pulse L2. 9 is a condenser lens that irradiates the laser pulse L4 from the galvano scanner 8 to the hole drilling position on the printed circuit board 1. 10 is a laser irradiation unit in which the AOM 6, damper 7, galvano scanner 8, and condenser lens 9 are mounted.

11 is an overall control unit that controls the operation of the entire device, and is realized by, for example, a program-controlled processing device. The overall control unit 11 includes a laser oscillation control unit 12 that outputs a laser oscillation command signal S that instructs the laser oscillator 5 to oscillate a laser pulse L1, an AOM control unit 13 that outputs an AOM drive signal D that controls the branching and modulation operations of the AOM 6, a galvanometer control unit 14 that outputs a galvanometer operation control signal G that instructs the operation of the galvanometer scanner 8, and a control unit 15 that outputs a heating unit control signal H that instructs the operation of the heating unit 3. Some of these functional elements included in the overall control unit 11 may be provided separately from the overall control unit 11. The laser drilling device has various elements and connecting lines other than those described here, but they are omitted here. The measured value from the thermal sensor 2 is input to the overall control unit 11, and if there is a difference from the target value of the laser power, the power is adjusted by the AOM 6 to match the target value.

The galvanometer operation control signal G stops the galvanometer scanner 8 during the off period and rotates the galvanometer scanner 8 during the on period. When the galvanometer scanner 8 is stationary, one hole is drilled, and when the galvanometer scanner 8 rotates, the laser pulse L2 is irradiated to the next hole position. When the laser oscillation command signal S is on, it causes the laser oscillator 5 to oscillate, and when it is off, it stops the oscillation. The laser oscillation command signal S turns on in synchronization with the off of the galvanometer operation control signal G, and the galvanometer operation control signal G turns on with a certain delay from the on of the laser oscillation command signal S, rotating the galvanometer scanner to the next hole position. The AOM drive signal D branches the laser pulse L1 input to the AOM 6 in the processing direction to become the laser pulse L2 only during the on period, and branches it in the direction of the damper 7 as the laser pulse L3 in the non-processing direction during the other off periods.

The table 4 is moved left and right (hereafter referred to as the X direction) and vertical (hereafter referred to as the Y direction) relative to the plane of the drawing by a table drive unit (not shown), thereby moving the printed circuit board 1 and the laser irradiation unit 10 relative to each other, and the galvano scanner 8 deflects the laser pulse in the X and Y directions, allowing it to be irradiated at the required drilling positions on the printed circuit board 1. Similarly, the laser pulse can be irradiated to the thermal sensor 2 by performing a similar relative movement. Each of the table drive unit and the galvano scanner 8 is provided with both a system for moving (deflecting) in the X direction and a system for moving (deflecting) in the Y direction.

Next, the heating unit 3 will be described in more detail. FIG. 2 is a diagram illustrating the heating unit 3. As shown in FIG. 2, the heater driving device 33 has a cylinder 34 inside. The cylinder 34 has a rod 35 that expands and contracts in the left-right direction in the drawing, and a heater holder 32 and a heater 31 are attached to the tip of the rod 35. The heater holder 32 and the heater 31 move in the left-right direction in the drawing in response to the expansion and contraction movement of the cylinder 34. The heater 31 is controlled by the heating unit control unit 15 and generates heat at a desired temperature.

When the laser power is not measured, as shown in FIG. 2, the rod 35 extends, and the heater 31 heats the light absorbing member 21 so as to cover the entire surface of the light absorbing member 21. In this embodiment, the heater 31 is heated to the temperature of the light absorbing member 21 when the laser of the target power is irradiated (hereinafter referred to as the corresponding temperature), and the light absorbing member 21 is heated to a temperature close to the corresponding temperature. Note that the relationship between the laser power and the corresponding temperature is measured in advance for each processing condition, tabulated, and stored in the memory in the heating unit control unit 15, and the light absorbing member 21 can be heated at a temperature according to the processing condition. Here, "for each processing condition" mainly refers to the laser processing condition, and means the laser frequency, pulse width, etc. When the laser power is measured, as shown in FIG. 3, the rod 35 is contracted so that the heater 31 and heater holder 32 do not cover the upper part of the light absorbing member 21, and the light absorbing member 21 is irradiated with the laser.

By doing this, the light absorbing member 21 is at a temperature close to the corresponding temperature when the laser power is measured, and the time it takes for the light absorbing member 21 to reach equilibrium after the laser is incident is shortened. In other words, the time it takes to obtain an accurate measurement value can be shortened. Note that the laser power is measured at any time, such as before processing begins, after a certain amount of time has passed since processing began, or after a certain number of workpieces have been processed.

In this embodiment, the light absorbing member 21 is heated when the laser power is not being measured, but it is sufficient that the light absorbing member 21 is heated to near the corresponding temperature at the timing when the laser power is measured, and it is not necessary to heat it all the time when not being measured. Therefore, for example, as shown in FIG. 4, when measuring the laser power at predetermined times t1, t2, and t3, and it takes tp from the start of heating to reaching the corresponding temperature, it is possible to heat only from t1-tp to t1, from t2-tp to t2, and from t3-tp to t3, and not heat at other times. In this way, heating more than necessary can be avoided.

In this embodiment, the heater expands and contracts so as not to block the area above the light receiving unit during power measurement, but the heater may be fixed and the thermal sensor moved.

In addition, in this embodiment, the laser power is measured at one location near the processing point. However, this is not limited to this, and the measurement may be performed at any number of locations between the laser output of the laser oscillator and the point where the laser is irradiated onto the workpiece.

1: Printed circuit board
2: Thermal sensor 21: Suction member 3: Heating unit 31: Heater 32: Heater holder 33: Heater driving device 34: Cylinder 35: Rod 4: Table
5: Laser oscillator
6: AOM
7: Damper
8: Galvano scanner
9: Condenser lens
10: Laser irradiation unit 11: Overall control unit 12: Laser oscillation control unit
13: AOM control section
14: Galvano control unit
15: Heating unit control section

Claims (1)

A laser processing device that applies a laser beam emitted from a laser oscillator to a workpiece to process the workpiece,
a thermoelectric power sensor for measuring the power of a laser beam emitted from a laser oscillator;
a heating unit that heats the laser receiving unit of the thermoelectric power sensor,
the heating unit heats the laser receiving unit of the thermoelectric power sensor at a temperature corresponding to a target value of laser power when the thermoelectric power sensor is not measuring the power of the laser beam.
A laser processing device characterized by the above.

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