JP2020006438A - Laser processing device and laser processing method - Google Patents

Abstract

To provide a laser processing device, which even if energy of laser pulse outputted from a laser oscillator varies at a step of creating control information for ADO, can be suppressed from being affected by the variation of the energy to secure hole quality.SOLUTION: A laser processing device comprises a light deflection part that can change a deflection direction of laser pulse made incident and energy to be emitted, by changing frequencies and amplitude of a driving signal to be transmitted, and a control part for transmitting a driving signal with amplitude corresponding to each frequency, and guides laser pulse emitted from the light deflection part to a work-piece and irradiates the pulse to the work-piece to process the work-piece. The control part sets amplitude, which comes close to a lowest ratio among ratios of emitted energy to energy of the laser pulse made incident in amplitude at which the emitted energy of the light deflection part becomes maximum, to amplitude corresponding to each frequency.SELECTED DRAWING: Figure 1

Description

The present invention relates to a laser processing apparatus and a laser processing method for making a hole in a printed circuit board using a laser, for example.

2. Description of the Related Art There is known a laser processing apparatus using a laser oscillator that changes a laser irradiation position by using an acousto-optical element (hereinafter abbreviated as AOD) having a high operation speed. The AOD is controlled by an RF signal provided from an AOD control unit. The deflection angle is determined by the frequency of the RF signal, and the emission energy is determined by the amplitude of the RF signal.
Since the AOD has a property that the emission energy changes depending on the deflection angle, for example, Patent Document 1 discloses control information for setting the amplitude corresponding to the frequency of the RF signal in order to keep the emission energy constant even when the deflection angle changes. A technique is disclosed in which a control table in which is registered in advance is created, and the AOD is controlled based on the control table.

An example of a conventional method of creating the control table and its use are as follows.
A laser pulse from the laser oscillator is applied to the AOD to be deflected, and the emission energy at that time is detected. This operation is repeated for each frequency of the RF signal for determining the deflection angle, and the minimum level of the emitted energy in the RF signal is detected. Next, for each frequency of the RF signal for determining the deflection angle, a control table for registering control information for determining the amplitude of the RF signal so as to output the minimum level of output energy is created, and a processing operation is performed. Is registered in a memory in the overall control unit that controls
When actually drilling a work such as a printed circuit board, data for determining an amplitude corresponding to a frequency is read from the control table, and the deflection angle and output energy of the AOD are controlled.

The conventional method of creating a control table as described above is based on the premise that the energy of a laser pulse output from a laser oscillator is constant. At the stage of creating the control table, when an RF signal of a certain frequency is given, even if the energy of the laser pulse output from the laser oscillator happens to increase or decrease, the control table is created based on that. Become.
As a result, the AOD is controlled by an incorrect control table, and there is a problem that the hole quality is deteriorated, for example, the diameter of the hole to be machined is small or the hole does not penetrate.

Patent No. 5122773

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to suppress the influence of a change in the energy of a laser pulse output from a laser oscillator at the stage of creating control information for an AOD, thereby ensuring hole quality. And

In order to solve the above-mentioned problem, a typical laser processing apparatus disclosed in the present application is an optical deflecting unit that can change the deflection direction and emission energy of an incident laser pulse by changing the frequency and amplitude of a drive signal to be given. And a control unit for providing a drive signal having an amplitude corresponding to each frequency, and the laser pulse emitted from the optical deflection unit is guided to the workpiece and irradiated, thereby processing the workpiece. In the laser processing apparatus, the control unit sets the amplitude at which the emission energy of the light deflecting unit is close to a minimum ratio among the ratio of the emission energy to the energy of the incident laser pulse at the amplitude at which the emission energy is maximum. The amplitude corresponds to each frequency.

ADVANTAGE OF THE INVENTION According to this invention, even if the energy of the laser pulse output from a laser oscillator changes at the production | generation stage of the control information for AOD, it can suppress that it is influenced by it and can ensure a hole quality. it can.

4 is a schematic flowchart illustrating an operation of a table creation unit in the laser processing apparatus according to the first embodiment of the present invention. FIG. 1 is a configuration block diagram of a laser processing apparatus according to a first embodiment of the present invention. FIG. 3 is a diagram for explaining a role of a galvano deflecting unit and an AOD deflecting unit in the laser processing apparatus of FIG. 2. FIG. 3 is a diagram illustrating an example of an RF signal in the laser processing apparatus in FIG. 2. FIG. 3 is a diagram showing the contents of one work table in the laser processing apparatus of FIG. 2. FIG. 3 is a diagram showing the contents of another work table in the laser processing apparatus of FIG. 2. FIG. 3 is a diagram showing the contents of a control table in the laser processing apparatus of FIG. 2. FIG. 9 is a diagram for explaining a second embodiment of the present invention. FIG. 9 is a diagram for explaining a third embodiment of the present invention. FIG. 9 is a diagram for explaining a fourth embodiment of the present invention. FIG. 14 is a diagram for explaining a fifth embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Example 1
FIG. 2 is a block diagram of the laser processing apparatus according to the first embodiment of the present invention. The components and connection lines are shown mainly for the purpose of describing the present embodiment, and do not necessarily indicate all components necessary for the laser processing apparatus.

The laser processing apparatus here is for making a hole in a printed circuit board. However, the present invention is not limited to this, and laser processing for processing light at a plurality of locations on a workpiece by splitting the light into reflection and transmission by a beam splitter or the like. It may be a device.
In FIG. 2, 2 is a table on which a printed circuit board to be processed is placed, 3 is a laser oscillator that oscillates a laser pulse L1, and 4 is a beam splitter that splits the laser pulse L1 emitted from the laser oscillator 3 into reflection and transmission. , 6 is an AOD deflecting unit that deflects the laser pulse L1 reflected by the beam splitter in a two-dimensional direction using AOD, 7 is a damper that absorbs the laser pulse L3 transmitted in the AOD deflecting unit 6 without being deflected in the processing direction, Reference numeral 8 denotes a galvano deflecting unit that deflects the laser pulse L2 deflected in the processing direction by the AOD deflecting unit 6 in a two-dimensional direction using a galvanomirror. This is a condensing lens.
The AOD deflecting unit 6 includes an AOD for deflecting the incident light in the X direction and an AOD for deflecting the outgoing light of the AOD in the Y direction. The galvano deflecting unit 8 has the same configuration. .

In this laser processing apparatus, the scanning region of the galvano deflecting unit 8 is sequentially moved by moving the table 2, but the galvano deflecting unit 8 positions the laser pulse at a specific position in the scanning region. The AOD deflecting unit 6 is used for quickly positioning a peripheral position around the specific position. FIG. 3 shows the relationship between the specific position and the peripheral position. In FIG. 3, reference numeral 20 denotes a specific position, and reference numeral 21 denotes an area serving as a peripheral position.
For example, by irradiating the laser at a specific position 20 and then irradiating the laser at a peripheral position, trepanning processing can be realized.

  Referring back to FIG. 2, reference numeral 10 denotes an overall control unit for controlling the operation of the entire apparatus, which is configured, for example, with a processing apparatus under program control at the center. Shall be included. Some of the components may be provided separately from the components. It is assumed that the overall control unit 10 has control functions other than those described here, and is also connected to blocks not shown.

A laser oscillation controller 11 that outputs a laser oscillation command signal S for commanding oscillation and attenuation of the laser pulse L1 in the laser oscillator 3 and control information for controlling the AOD are registered in the overall controller 10. A control table 12, an AOD control unit 13 for outputting an AOD drive signal D for controlling the AOD according to the contents of the control table 12, and a galvano control unit 14 for outputting a galvano control signal G for controlling the galvano deflection unit. Is provided.
The AOD control unit 13 and the galvano control unit 14 control two X-system and Y-system AOD deflecting units 6 and 8, respectively. Although only one control table 12 is shown, two control tables 12 are provided for X-system and Y-system.

The AOD drive signal D output from the AOD control unit 13 is composed of an RF signal, the deflection angle of the AOD deflection unit 6 is changed by the frequency of the RF signal, and the emission energy is changed by the amplitude level of the RF signal.
FIG. 4 shows an example of the AOD drive signal D. In the AOD drive signals Da and Db, the frequencies are fa and fb, and the amplitudes are Aa and Ab, respectively. The frequency fb is higher than fa, and the amplitude Ab is higher than Aa.
When the AOD drive signal Db is applied, the deflection angle and emission energy at the AOD deflection unit 6 are larger than when the AOD drive signal Da is applied.
As will be described later, the control table 12 stores, in a memory, data for determining the amplitude to be given at each frequency of the RF signal given to the AOD.

In order to create the control table 12 based on the present invention, the laser processing apparatus here has the average power of the laser pulse transmitted through the beam splitter 4 as shown in FIG. A thermal sensor 16 that outputs a corresponding detection signal and a thermal sensor 17 that outputs a detection signal corresponding to the average power of the laser pulse L4 emitted from the condenser lens 9 are attached. The thermal sensors 16 and 17 are for detecting the average power of the laser pulse as heat, and these detection signals are input to the table creation unit 18.

Here, a method of detecting the average power using a thermal sensor is used to detect the energy of the laser pulse, but the energy may be detected by another method.
Further, here, the energy of the laser pulse L1 emitted from the laser oscillator 3 is detected via the beam splitter 4, but the energy of the laser pulse L1 may be detected by another method.

Hereinafter, a method of creating the control table 12 by the table creating unit 18 will be described.
When the X-system control table 12 is created, the frequency of the RF signal applied to the Y-system AOD is fixed, and the frequency of the RF signal applied to the X-system is sequentially switched by the AOD control unit 13. On the other hand, when the Y-system control table 12 is created, the frequency of the RF signal applied to the X-system AOD is fixed, and the frequency of the RF signal applied to the Y-system is switched by the AOD control unit 13 in order. deep.

When the X-system control table 12 is created, the frequency of the RF signal given to the X-system AOD is fixed, and the amplitude of the RF signal can be sequentially switched. On the other hand, when creating the Y-system control table 12, the frequency of the RF signal applied to the Y-system AOD is fixed, and the amplitude of the RF signal can be sequentially switched.

The galvano deflecting unit 8 positions the laser pulse L2 from the AOD deflecting unit 6 near the center of its scanning area, that is, near the center of the condenser lens 9. In this way, it is possible to avoid an adverse effect due to a change in transmittance due to the incident position on the condenser lens 9.
By sequentially switching the frequency of the RF signal applied to the X system, the laser irradiation position moves in the X direction in FIG. 3, and by sequentially switching the frequency of the RF signal applied to the Y system, the laser irradiation position becomes Y in FIG. Move in the direction.

FIG. 1 is a schematic flowchart showing the operation of the table creation unit 18.
Although the case where the X-system control table 12 is created will be described, the same applies to the case where the Y-system control table 12 is created.
When the frequencies of the respective RF signals given to the X-system AOD at the positions x1, x2, x3... In the X direction in FIG. 3 are f1, f2, f3. Are sequentially switched to f1, f2, f3..., And the detection signals of the thermal sensors 16 and 17 in each case are sent to the table creation unit 18.

In this embodiment, the average power of the laser pulse L1 transmitted through the beam splitter 4 and detected by the thermal sensor 16 is related to the transmittance of the beam splitter 4 when the average power of the laser pulse L1 is directly detected. It shall be 1/100 in comparison.
Therefore, the table creation unit 18 obtains the average power α of the laser pulse L1 by multiplying the detection value by the thermal sensor 16 by 100, and obtains the power ratio γ (β) with the average power β of the laser pulse L4 detected by the thermal sensor 17. / α) is calculated and registered in the work table W1 (step S1 in FIG. 1). FIG. 5 shows the contents of the work table W1.

  When the operation of step S1 is performed, it is assumed that the amplitude of the RF signal applied to the AOD is when the emission energy is at a maximum. For this, the relationship between the frequency and amplitude of the RF signal and the maximum emission energy may be determined in advance, and the amplitude given to the AOD may be determined based on the relationship.

In the work table W1 of FIG. 5, u-α1, u-α2, u-α3... Are the average powers α at the frequencies f1, f2, f3. are the average powers β at the frequencies f1, f2, f3,... of the RF signal, and u-γ1, u-γ2, u-γ3,... are the frequencies f1, f2, Power ratio γ at f3 ...

  The contents of the work table W1 here are for explaining the logical relationship between the data. For example, for each of the RF signal frequencies f1, f2, f3. Data indicating x2, x3... is not always registered. The same applies to a work table and a control table described below.

Next, the lowest power ratio (hereinafter referred to as the lowest power ratio) is extracted from the power ratios u-γ1, u-γ2, u-γ3,... In the work table W1 (step in FIG. 1). S2). This is u-γn at the frequency fn when the position is set at the position xn in the X direction.
Next, the frequency of the RF signal is fixed to the frequency f1 when the RF signal is positioned at the position x1 in the X direction, and the amplitude of the RF signal is divided into controllable ranges and sequentially switched to a1, a2, a3,. Then, the average power α, the average power β, and the power ratio γ (β / α) of both cases are registered in the work table W2 (step S3 in FIG. 1). FIG. 6 shows the contents of the work table W2.

In the work table W2 of FIG. 6, v-α1, v-α2, v-α3... Indicate the average power α at the RF signal amplitudes a1, a2, a3. , V-β3... Each have an average power β at the RF signal amplitude a1, a2, a3..., And v-γ1, v-γ2, v-γ3. , A2, a3,...

Next, among the power ratios v-γ1, v-γ2, v-γ3,... In the work table W2, the power ratio closest to the minimum power ratio u-γn is extracted. This is the power ratio v-γm when the amplitude of the RF signal is am here. Then, am is registered in the control table 12 as the amplitude when the frequency f1 of the RF signal is given in order to position the position x1 in the X direction (step S4 in FIG. 1).

Next, steps 3 to 5 are performed by creating a work table W2 for each of the frequencies f2, f3,... For positioning at other positions x2, x3,. Are registered in the control table 12 (step S5 in FIG. 1). FIG. 7 shows the contents of the control table 12 completed in this way.

The control table 12 created as described above is used as follows. The case where the X-type control table 12 is used will be described, but the same applies to the case where the Y-type control table 12 is used.
In FIG. 2, when data for positioning at the position x1 in the X direction is given to the AOD control unit 13, the AOD control unit 13 reads out the frequency f1 and the amplitude am of the RF signal given to the AOD from the control table 12, and performs AOD deflection. Give to Part 6.
As a result, in the AOD deflecting unit 6, a laser pulse L2 having a deflection angle and an average power corresponding to the frequency f1 and the amplitude am of the RF signal is emitted to the galvano deflecting unit 8. The same applies to the case of positioning at other positions x2, x3... In the X direction.

According to the above embodiment, the control table 12 is created based on the power ratio between the average power α of the laser pulse L1 emitted from the laser oscillator 3 and the average power β of the laser pulse emitted from the condenser lens 9. Therefore, even if the energy of the laser pulse emitted from the laser oscillator 3 happens to increase or decrease, the effect can be eliminated and the hole quality can be ensured.

Example 2
In the first embodiment, when the work table W1 is created, each of the frequencies f1, f2, f3... Corresponding to each position x1, x2, x3. And the power ratio is determined for each.
However, as the frequency of the RF signal applied to the AOD, the center frequency of each frequency band when the frequency fluctuation range is divided at regular intervals, and the power ratio (hereinafter, referred to as the center power ratio) is obtained for each. The work table W1 may be created.

FIG. 8 is a diagram for explaining the above method. 8, T1 and T2 are adjacent frequency bands, ft1 and ft2 are the center frequencies of the frequency bands T1 and T2, and U1 and U2 are the center power ratios at the center frequencies ft1 and ft2.
In this method, the power ratio for each of the frequencies f1, f2, f3... Corresponding to the respective positions x1, x2, x3.

For example, the power ratio U100 at the frequency f100 corresponding to the position x100 in the X direction is approximated as changing in a direct proportional relationship with the frequency, and using the data of f100, ft1, ft2, U1, and U2, (f100−ft1 ) × (U2-U1) / (ft2-ft1) + U1.
The minimum power ratio in the fluctuation range of the frequencies f1, f2, f3... Corresponding to the respective positions x1, x2, x3... In the X direction is extracted from the power ratios obtained as described above. I just need.

According to the second embodiment, it is not necessary to determine the power ratio for each of the frequencies f1, f2, f3,... Corresponding to the positions x1, x2, x3,. The number of entries to be registered can be reduced.
The same applies to the Y direction if the center power ratio is determined at each of the center frequencies for each frequency band when the frequency fluctuation range is divided at regular intervals as in the X direction.

Example 3
In the first embodiment, when the work table W2 is created, the power ratio is determined for each of the amplitudes a1, a2, a3,.
However, in the same manner as in the case of creating the work table W1 in the second embodiment, the amplitude of the RF signal applied to the AOD is set to the center amplitude for each amplitude band when the amplitude variation range is divided at regular intervals. The work table W2 may be created by calculating the power ratio (hereinafter, referred to as the amplitude center power ratio).
The power ratio for each of the RF signal amplitudes a1, a2, a3,... Can be approximately determined in the same manner as in the second embodiment based on the center power ratio determined in each frequency band. .

FIG. 9 is a diagram for explaining the above method. In FIG. 9, S1 and S2 are adjacent amplitude bands, ms1 and ms2 are the center amplitudes of the amplitude bands S1 and S2, and V-1 and V-2 are the amplitude center power ratios at the center amplitudes ms1 and ms2.
In this method, the power ratio for each of the amplitudes a1, a2, a3,... Can be approximately obtained. For example, the power ratio v200 at the amplitude m200 is approximated as changing in a direct proportional relationship with the amplitude, and using the data of m200, ms1, ms2, V1 and V2, (m200−ms1) × (v2−v1) / It can be calculated by the formula of (ms2−ms1) + v1.

The amplitude having the power ratio closest to the minimum power ratio may be extracted based on the power ratio obtained in this manner.
According to the above method, the number of entries registered in the work table W2 can be reduced, as in the case of the work table W1.

Example 4
In the third embodiment, when the work table W2 is created, the amplitude of the RF signal applied to the AOD is set to the center amplitude for each amplitude band when the amplitude fluctuation range is divided at regular intervals. As the frequency of the signal, each of the frequencies f1, f2, f3... For positioning at the positions x1, x2, x3. Alternatively, a center frequency for each frequency band may be given.

FIG. 10 is a diagram for explaining the above method. In FIG. 10, ft11 and ft12 are the respective center frequencies in adjacent frequency bands, U11 and U12 are power ratios detected at the respective center frequencies ft11 and ft12 when the amplitude of the RF signal applied to the AOD is the center amplitude mS10, U21 and U22 are power ratios detected at the respective center frequencies ft11 and ft12 when the amplitude of the RF signal applied to the AOD is the center amplitude mS20.

The amplitude having the power ratio closest to the minimum power ratio can be approximately obtained as follows. For example, the amplitude m300 at which the power ratio at the frequency f300 is closest to the previously determined minimum power ratio γmin is the power ratio U11, U12, U21 at the center amplitude mS10 and mS20 in the frequency band above and below the frequency f300. , U22, m300 = mS20 + (mS10−mS20) ÷ (J−K) × γmin. Here, J = U11 + (U12−U11) ÷ (ft12−ft11) × f300, and K = U21 + (U22−U21) ÷ (ft12−ft11) × f300.

Example 5
In the above embodiments, the control table 12 of the AOD deflecting unit 6 is created in a state where the control table 12 is incorporated in the laser processing apparatus.
On the other hand, an AOD deflecting unit 23 having the same characteristics as the AOD deflecting unit 6 with respect to the relationship among the frequency, amplitude, and emission energy, and a control table 24 having the same contents as the control table 12 created as in the above embodiment are shown in FIG. By incorporating the set AOD deflection unit 25 as a part as a component instead of the AOD deflection unit 6 and the control table 12 in the laser processing apparatus in FIG. 2, another laser processing apparatus may be manufactured. Good.
With this configuration, in another laser processing apparatus, there is no need to create a control table again, and the thermal sensors 16 and 17 and the table creating unit 18 are not required.

2: Table 3: Laser oscillator 4: Beam splitter 6, 23: AOD deflecting unit 7: Damper 8: Galvano deflecting unit 9: Condensing lens 10: Overall control unit,
11: laser oscillation controller 12, 24: control table 13: AOD controller
14: Galvano control unit 16, 17: Thermal sensor 18: Table creation unit 25: AOD deflection unit D: AOM drive signal G: Galvano control signal, L1 to L3: laser pulse
S: Laser oscillation command signal

Claims (7)

It has an optical deflecting unit that can change the deflection direction and emission energy of the incident laser pulse by changing the frequency and amplitude of the applied drive signal, and a control unit that provides a drive signal with an amplitude corresponding to each frequency. In the laser processing apparatus configured to process the workpiece by guiding and irradiating the workpiece with the laser pulse emitted from the light deflection unit, the control unit may control the emission energy of the light deflection unit to be a maximum. A laser processing apparatus, wherein an amplitude that approaches a minimum ratio of a ratio of the output energy to the energy of the incident laser pulse at an amplitude is set as an amplitude corresponding to each of the frequencies. The laser processing apparatus according to claim 1, further comprising a first detection unit that detects the incident side energy and a second detection unit that detects the emission energy, wherein the ratio is equal to the first detection unit and the second detection unit. A laser processing apparatus characterized by being obtained from a detection result from the second detection unit. 3. The laser processing apparatus according to claim 2, wherein the control unit is configured to detect the energy detected by the second detection unit for the output energy at an amplitude at which the output energy is maximum for each frequency. 4. A first step of obtaining a ratio with respect to the energy detected in step 2, a second step of obtaining a lowest ratio among the ratios, and an amplitude corresponding to the frequency at which the ratio approaches the lowest ratio for each frequency. Performing a third step of determining an amplitude to be performed, thereby providing a drive signal having an amplitude corresponding to each of the frequencies.   4. The laser processing apparatus according to claim 2, wherein the second detection unit detects energy of a laser pulse actually applied to the workpiece. 5.   The laser processing apparatus according to claim 1, further comprising a second light deflecting unit that further deflects a laser pulse emitted from the light deflecting unit. 6. The laser processing apparatus according to claim 1, wherein the control unit includes a control table for registering an amplitude corresponding to each frequency in advance. A drive signal having an amplitude corresponding to each frequency is given to an optical deflecting unit that can change the deflection direction and emission energy of an incident laser pulse by changing the frequency and amplitude of the drive signal to be applied, and emitted from the optical deflecting unit. In a laser processing method for processing a workpiece by guiding and irradiating a laser pulse to the workpiece, a ratio of the output energy to the incident side energy at an amplitude at which the output energy of the light deflecting unit is maximized. A laser processing method wherein an amplitude approaching the lowest ratio among them is given as an amplitude corresponding to each of the frequencies.