KR20200074851A - Gas laser apparatus and method for laser oscillation - Google Patents

Abstract

The present invention provides a gas laser apparatus capable of increasing the positioning accuracy of a beam spot to suppress a decrease in efficiency. Discharge is generated in a discharge region of a part of a circulation path through which laser gas circulates to output a laser beam. A heat exchanger cools the laser gas circulating in the circulation path. A temperature sensor measures the temperature of the laser gas directed from the heat exchanger to the discharge region. A control device controls the cooling capacity of the heat exchanger so that a measured value of the temperature sensor becomes a target temperature of 30°C or less, based on the measured value of the temperature by the temperature sensor.

Description

Gas laser device and laser oscillation method {GAS LASER APPARATUS AND METHOD FOR LASER OSCILLATION}

This application claims priority based on Japanese Patent Application No. 2018-235276 filed on December 17, 2018. The entire contents of the application are incorporated herein by reference.

The present invention relates to a gas laser device and a laser oscillation method.

A gas laser device that constantly controls the temperature of a laser gas is known (for example, Patent Document 1 below). In the gas laser device described in Patent Document 1, the laser gas whose temperature has been increased by discharge is cooled by a heat exchanger. In addition, the temperature of the laser gas is measured, and the temperature of the cooling water flowing to the heat exchanger is controlled so that the temperature of the laser gas is constant. By controlling the temperature of the laser gas constantly, the stability of the laser output can be increased.

Patent Document 1: Japanese Patent Application Publication No. 61-154188

When laser processing is performed by controlling the position of the beam spot of the laser beam with high precision, it has been found that it is difficult to secure sufficient positional accuracy with a conventional method. In addition, it has been found that the efficiency of the laser oscillator may be lowered by the conventional method.

An object of the present invention is to provide a gas laser device and a laser oscillation method capable of increasing the positional accuracy of a beam spot and suppressing a decrease in efficiency.

According to one aspect of the invention,

A gas laser device that generates a discharge in a discharge region of a part of a circuit through which laser gas circulates and outputs a laser beam,

A heat exchanger for cooling the laser gas circulating in the circulation path,

And a temperature sensor for measuring the temperature of the laser gas from the heat exchanger to the discharge region,

A gas laser device is provided having a control device for controlling the cooling capacity of the heat exchanger so that the measured value of the temperature sensor is a target temperature of 30°C or less based on the measured value of the temperature by the temperature sensor.

According to another aspect of the invention,

While circulating the laser gas through the discharge region, generating the discharge in the discharge region and adjusting the temperature of the laser gas so that the temperature of the laser gas flowing into the discharge region is 30° C. or less while generating the laser. A laser oscillation method is provided.

By controlling the temperature of the laser gas within a range of 30° C. or less, a decrease in efficiency can be suppressed and a deviation in the position of the beam spot can be reduced.

1 is a cross-sectional view including an optical axis of a gas laser device according to an embodiment.
2 is a cross-sectional view perpendicular to the optical axis of the gas laser device according to the present embodiment.
3 is a graph showing measurement results of the relationship between the temperature before the discharge of the laser gas, the discharge current, and the efficiency.
4 is a graph showing the relationship between the temperature before the discharge of the laser gas and the deviation of the beam spot position.
5 is a graph showing the relationship between the temperature before the discharge of the laser gas and the displacement amount of the beam spot average position.
6 is a schematic block diagram of a laser processing apparatus according to another embodiment.
7 is a flow chart showing a procedure for performing laser processing by operating the laser processing factory of the embodiment.

The gas laser device according to the embodiment will be described with reference to FIGS. 1 and 2.

1 is a cross-sectional view including an optical axis of a gas laser device according to an embodiment. The laser gas is accommodated in the chamber 10. The interior space of the chamber 10 is divided into an optical chamber 11 positioned relatively upward and a blower chamber 12 positioned relatively lower. The optical chamber 11 and the blower chamber 12 are divided into upper and lower partition plates 13. However, the upper and lower partition plates 13 are provided with openings through which laser gas flows between the optical chamber 11 and the blower chamber 12. The bottom plate 14 of the optical chamber 11 extends from the side wall of the blower chamber 12 in the optical axis direction, and the length of the optical chamber 11 in the optical axis direction is longer than the length of the blower chamber 12 in the optical axis direction. . The chamber 10 is supported on the optical base by the chamber support member 16 on the bottom plate 14 of the optical chamber 11.

In the optical chamber 11, a pair of discharge electrodes 21 and a pair of resonator mirrors 25 are arranged. The pair of discharge electrodes 21 are supported on the bottom plate 14 through discharge electrode support members 22 and 23, respectively. The pair of discharge electrodes 21 are arranged at intervals in the vertical direction, and the discharge region 24 is defined between them. The discharge electrode 21 excites the laser gas by generating discharge in the discharge region 24. As described later with reference to FIG. 2, the laser gas flows in the direction perpendicular to the ground surface of FIG. 1 in the discharge region 24.

The pair of resonator mirrors 25 are fixed to one common support member 26 disposed in the optical chamber 11. The common support member 26 is supported by the bottom plate 14 through a pair of light resonator support members 27. The resonator mirror 25 constitutes an optical resonator having an optical axis passing through the discharge region 24. A light transmitting window 28 for transmitting a laser beam is mounted at an intersection between the extension line extending the optical axis of the optical resonator in one direction (left direction in FIG. 1) and the wall surface of the optical chamber 11. The laser beam excited in the optical resonator passes through the light transmitting window 28 and is radiated to the outside.

The blower 30 is disposed in the blower chamber 12. The blower 30 circulates the laser gas between the optical chamber 11 and the blower chamber 12.

2 is a cross-sectional view perpendicular to the optical axis of the gas laser device according to the present embodiment. The inner space of the chamber 10 is divided into an upper optical chamber 11 and a lower blower chamber 12 by the upper and lower partition plates 13. In the optical chamber 11, a pair of discharge electrodes 21 and a common support member 26 for supporting the optical resonator are disposed. A discharge region 24 is defined between the discharge electrodes 21.

A partition plate 15 is disposed in the optical chamber 11. The partition plate 15 is a first gas flow path 51 from the opening 13A provided in the upper and lower partition plates 13 to the discharge region 24, and the other provided in the upper and lower partition plates 13 from the discharge region 24. The second gas flow path 52 up to the opening 13B is defined. The laser gas flows through the discharge region 24 in a direction orthogonal to the optical axis. The discharge direction is orthogonal to both the direction in which the laser gas flows and the optical axis. A circulation path through which laser gas circulates is formed by the blower chamber 12, the first gas flow path 51, the discharge region 24, and the second gas flow path 52. The blower 30 generates a flow of laser gas so that the laser gas circulates through the circulation path.

The heat exchanger 56 is accommodated in the circulation path in the blower chamber 12. Cooling medium such as cooling water is supplied from the cooler 57 to the heat exchanger 56, and the cooling medium is recovered from the heat exchanger 56 to the cooler 57. The laser gas heated in the discharge region 24 is cooled by passing through the heat exchanger 56, and the cooled laser gas is supplied again to the discharge region 24.

The upper and lower partition plates 13 are provided with outlet holes 58 for flowing laser gas from the blower chamber 12 to the optical chamber 11. Part of the laser gas included in the flow of the laser gas directed to the first gas flow path 51 by the blower 30 passes through the outlet hole 58 and flows out to the optical chamber 11. In the outlet hole 58, a filter 59 for removing particles is provided. For example, the filter 59 blocks the outlet hole 58, and the laser gas flowing out from the blower chamber 12 to the optical chamber 11 is filtered by passing through the filter 59.

A temperature sensor 55 is disposed in the first gas flow passage 51. The temperature sensor 55 measures the temperature of the laser gas from the heat exchanger 56 to the discharge region 24. As the temperature sensor 55, for example, a resistance thermometer can be used. The measurement result of the temperature sensor 55 is input to the control device 40. The control device 40 controls the cooling ability of the heat exchanger 56 so that the measured value by the temperature sensor 55 becomes the target temperature. For example, the control device 40 changes the temperature of the cooling medium supplied from the cooler 57 to the heat exchanger 56. Thus, the temperature of the laser gas flowing into the discharge region 24 can be maintained at the target temperature.

Next, with reference to FIGS. 3 to 5, the preferred temperature of the laser gas will be described. The output and the clearance ratio (CR value) of the gas laser device were made constant, and the temperature of the laser gas was changed and an evaluation experiment was conducted.

3 is a graph showing measurement results of the relationship between the temperature before the discharge of the laser gas, the discharge current, and the efficiency. The horizontal axis represents the temperature before the discharge of the laser gas in units of "°C", the vertical axis on the left represents efficiency in units "J/A", and the vertical axis on the right represents the discharge current in units "A". The circle symbol in the graph of FIG. 3 represents the measured value of the discharge current, and the triangle symbol represents efficiency. The temperature before discharge of the laser gas is equivalent to the measured value of the temperature sensor 55 (FIG. 2).

As the gas laser device, a carbon dioxide gas ray storage value was used, and the laser power was adjusted to be 240 W. More specifically, the pulse frequency was set to 3 kHz, and the energy per pulse was set to 80 mJ. The CR value of the laser gas was set to about 1.7. The CR value is defined by the following equation.

CR=v/(W×f)

Here, v represents the flow rate of the laser gas, W represents the discharge width in the gas flow direction, and f represents the repetition frequency of the pulse.

As the temperature before the discharge of the laser gas increases, the discharge current increases. In particular, in a range in which the temperature before the discharge of the laser gas is higher than 30°C, the ratio of the increase in the discharge current to the increase in the temperature before the discharge of the laser gas is increased compared to the range below 30°C. Moreover, in the range in which the temperature before the discharge of the laser gas is 30° C. or less, the variation in efficiency is small, but in the range higher than 30° C., the efficiency decreases as the temperature before the discharge of the laser gas increases.

In order to suppress the decrease in efficiency, it is preferable to control the temperature of the laser gas before discharge to be 30°C or less.

4 is a graph showing the relationship between the temperature before the discharge of the laser gas and the beam spot position. The horizontal axis represents the temperature before the discharge of the laser gas as a unit "°C", and the vertical axis represents 6σ as the unit "mm" as an index of the deviation of the beam spot position. The position of the beam spot was measured at a position where the optical path length from the gas laser device was 5 m. A concave mirror was placed in the optical path from the gas laser device to the location of the beam spot. The diameter of the beam spot in the plane for measuring the position of the beam spot was about 7 mm. The circular and triangular symbols in the graph of FIG. 4 indicate variations in the positions of the beam spots in the x and y directions, which are orthogonal to each other. The output of the gas laser device and the CR value are the same as in the case of the evaluation experiment shown in FIG. 3.

When the temperature before the discharge of the laser gas is higher than 30°C, it can be seen that the deviation of the beam spot position is large compared to the range below 30°C. In order to reduce the deviation of the beam spot position, it is preferable to control the temperature of the laser gas before discharge to be 30°C or less.

5 is a graph showing the relationship between the temperature before the discharge of the laser gas obtained in the evaluation experiment and the displacement amount of the beam spot average position. The horizontal axis represents the temperature before the discharge of the laser gas as a unit "°C", and the vertical axis represents the displacement amount of the beam spot average position in the unit "mm". The average position of the beam spot when the temperature before the discharge of the laser gas was 22.5°C was used as a reference for the position. The circular symbols and the triangular symbols in the graph of FIG. 5 indicate the displacement amounts of the average positions of the beam spots in the x and y directions orthogonal to each other. The output of the gas laser device and the CR values are the same as those of the evaluation experiment shown in FIG. 3.

From the results of the evaluation experiment shown in Fig. 5, it can be seen that the displacement amount in the y-direction position was the largest in the range in which the temperature before the discharge of the laser gas was 26°C to 30°C. In the range where the displacement amount in the y-direction position is the largest, when the gas temperature changes by about 4°C, the position of the beam spot changes by about 0.3 mm. For example, it can be seen that when the gas ray storage value is used for punching the printed substrate, empirically, it is desirable to make the displacement amount of the beam spot at the location where the beam spot position is measured in the evaluation experiment 0.2 mm or less. In the results of the evaluation experiment shown in Fig. 5, even if the displacement amount of the average position of the beam spot with respect to the change in gas temperature is the largest, if the variation width of the gas temperature is ±1°C or less, the displacement amount of the average position of the beam spot is about It is 0.15mm. At this time, the target that the displacement amount is 0.2 mm or less is satisfied. Therefore, in order to make the amount of displacement of the beam spot 0.2 mm or less, it is preferable to put the temperature before the discharge of the laser gas in the range of ±1°C or less, centering on the target temperature.

Moreover, in the range where the temperature of the laser gas is 26° C. or less, the slope of the graph shown in FIG. 5 is gentle. This means that even if the temperature change of the laser gas occurs, the displacement amount at the average position of the beam spot is small. Therefore, in order to stabilize the average position of the beam spot, it is more preferable to control the temperature of the laser gas to 26°C or less.

Next, the excellent effect of the above embodiment will be described.

In the above embodiment, temperature control is performed so that the temperature before discharge of the laser gas is 30°C or less. As a result, the gas ray storage value can be operated with high efficiency (see FIG. 3). Moreover, the deviation of the beam spot position can be suppressed (see Fig. 4). Further, in the above embodiment, temperature control is performed so that the temperature before discharge of the laser gas falls within a range of ±1°C centering on the target temperature. As a result, the displacement amount of the average position of the beam spot can be put within a certain allowable range.

Next, a laser processing apparatus according to another embodiment will be described with reference to FIGS. 6 and 7. The laser processing factory according to the present embodiment is used, for example, for punching a printed substrate.

6 is a schematic block diagram of a laser processing apparatus according to the present embodiment. The pulsed laser beam output from the laser oscillator 70 enters the object 75 to be processed, such as a printed substrate, via the beam shaping scanning optical system 71. The object to be processed 75 is held by a stage 72 such as an XY stage. The beam-shaped scanning optical system 71 scans the laser beam in a two-dimensional direction while adjusting the shape and size of the beam cross-section. The stage 72 moves the object 75 to be processed in two directions parallel to the surface to be processed.

The control device 40 and the laser oscillator 70 correspond to the gas laser device according to the embodiment shown in FIGS. 1 and 2. The control device 40 controls the laser oscillator 70 based on the set oscillation condition. Further, the control device 40 performs temperature control of the laser gas of the laser oscillator 70 based on the set target temperature.

The input/output device 41 has a function of displaying an image and a function of inputting a command from an operator, and also serves as an input device and an output device. For example, as the input/output device 41, a touch panel or the like is used. In addition, a display may be used as an output device, and a pointing device or a keyboard may be used as an input device.

Next, a method of setting the oscillation condition and temperature control condition will be described.

The control device 40 displays an input screen for inputting the oscillation condition and the temperature control condition to the input/output device 41 to the operator. The oscillation conditions include, for example, the repetition frequency of the pulse, the pulse width, and the like. Temperature control conditions include a target temperature, a feedback cycle, and a feedback gain. Further, the control device 40 displays the current temperature of the laser gas on the input/output device 41.

The feedback cycle and the feedback gain of the temperature control are set to appropriate values in advance so that the temperature of the laser gas falls within the range of ±1°C centering on the target temperature. The value of the feedback period and the feedback gain cannot be modified by a normal operator, and can only be modified by a user with administrator authority. The frequency, pulse width, and target temperature are input by the operator, for example, by selecting from a pull-down menu.

7 is a flowchart showing a procedure of laser processing by operating the laser processing factory in this embodiment.

The operator operates the input/output device 41 to input the target temperature (step S1). Next, the frequency and pulse width are input (step S2). The control device 40 performs an adjustment operation of the laser oscillator 70 based on the input condition (step S3). At this time, the pulsed laser beam output from the laser oscillator 70 is incident on the beam damper or the like, and is not incident on the object 75 to be processed. During the adjustment operation, the control device 40 displays the measured value of the temperature of the laser gas on the input/output device 41 as the current temperature.

The adjustment operation is performed until the current temperature of the laser gas falls within the allowable range (step S4). The operator may perform the determination as to whether or not the current temperature of the laser gas is within an allowable range based on the current temperature of the laser gas displayed on the input/output device 41. When the current temperature of the laser gas falls within the allowable range, laser processing is actually performed (step S5).

When the work of laser processing is finished, the operator operates the laser processing apparatus based on the end procedure (step S6). If the operation continues or the oscillation condition is not changed, the laser processing in step S5 is performed again (N in step S7). When the operation continues by changing the oscillation condition, the process of inputting the frequency and pulse width in step S2 is executed again (Y in step S7).

Next, the effect that this embodiment is excellent will be described.

In this embodiment, the operator can input the appropriate target temperature of the laser gas, so that the laser oscillator 70 can be operated under the condition that the deviation of the beam spot position is small and the efficiency is high.

As shown in Fig. 5, in order to stabilize the average position of the beam spot, it is desirable to lower the temperature of the laser gas. However, if the temperature of the laser gas is excessively lowered, dew condensation tends to occur. In order to prevent condensation, it is preferable that the target temperature of the laser gas is equal to or higher than the dew point of the environment in which the laser oscillator 70 is installed. The operator may obtain the dew point from the humidity of the environment and set the desired target temperature within a range in which no condensation occurs.

In general, the recommended environment of the laser processing device is often 50% humidity and 25°C temperature. Under this recommended environment, the dew point is about 14°C. For this reason, it is preferable to set the target temperature of the laser gas to 14°C or higher.

In addition, in this embodiment, the values of the feedback period and the feedback gain, which require skill in order to set the desired value, are set in advance, and the general operator does not need to input these values. For this reason, even if the operator is a low-skilled operator, it is possible to perform laser processing under preferred conditions by operating the present laser factory value.

Each of the above-described embodiments is an example, and it goes without saying that partial substitution or combination of configurations shown in other embodiments is possible. The same action and effect by the same configuration as the plurality of embodiments are not mentioned separately for each embodiment. In addition, the present invention is not limited to the above-described embodiment. For example, it will be apparent to those skilled in the art that various changes, improvements, combinations, and the like are possible.

10 chamber
11 Optical room
12 Blower Room
13 Upper and lower partition plates
13A, 13B opening
14 bottom plate
15 compartments
16 chamber support member
21 discharge electrode
22, 23 discharge electrode support member
24 discharge area
25 resonator mirror
26 Common support member
27 Optical resonator support member
28 Light transmission window
30 blowers
40 Control
41 I/O device
51 1st gas flow path
52 2nd gas flow path
55 Temperature sensor
56 heat exchanger
57 cooler
58 Outflow hole
59 Filter
70 laser oscillator
71 Beam Scanning Optical System
72 stages
75 Object to be processed

Claims (5)

A gas laser device that generates a discharge in a discharge region of a part of a circuit through which laser gas circulates and outputs a laser beam,
A heat exchanger for cooling the laser gas circulating in the circulation path,
And a temperature sensor for measuring the temperature of the laser gas from the heat exchanger to the discharge region,
A gas laser device having a control device for controlling the cooling capacity of the heat exchanger so that the measured value of the temperature sensor is a target temperature of 30°C or less based on the measured value of the temperature by the temperature sensor. According to claim 1,
A gas laser device having the target temperature of 14°C or higher. The method according to claim 1 or 2,
The control device is a gas laser device that controls the cooling capacity of the heat exchanger so that the measured value of the temperature sensor is within a range of ±1°C centering on the target temperature. The method according to claim 1 or 2,
Further having an input device for inputting the value of the target temperature,
The control device is a gas laser device that controls the cooling capacity of the heat exchanger based on the value of the target temperature input to the input device. While circulating the laser gas through the discharge region, generating the discharge in the discharge region and adjusting the temperature of the laser gas so that the temperature of the laser gas flowing into the discharge region is 30° C. or less while generating the laser. Laser emission method.

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