JP2003048088A - Laser beam machining method and laser beam machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate damage to an insulation layer and an inner layer conductor and to realize high-quality laser drilling and the machine, in the machining of a via hole, through hole, etc., by a beam scanning machining in which a laser beam with a high energy and a reduced beam diameter is used. SOLUTION: In the machining method in which a material laminated with a conducting layer and an insulating layer is irradiated by a laser beam in a desired locus to remove both layers, the laser irradiation is commenced, with the irradiation timing delayed for a prescribed time from the starting time of the locus movement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing machine and a processing method for irradiating a laser beam to form via holes and through holes necessary for a printed wiring board.

[0002]

2. Description of the Related Art A printed wiring board is a substrate having conductor layers 102 on both sides of an insulating layer 101 as shown in FIG. 16 or a wiring board in which the insulating layers 101 and 102 shown in FIG. 17 are laminated in multiple layers. Show.

Insulating layer 1 in these printed wiring boards
01 for electrically connecting between the conductor layers 102 on both sides, and for electrically connecting the conductor layer 102 in the outer layer portion of the printed wiring board and the conductor layer 102 in the inner layer portion of the printed wiring board. Conventionally, processing for forming the blind hole (via hole) using a laser beam such as a carbon dioxide gas laser has been performed. When processing with a laser beam,
The laser beam is well absorbed by the insulating layer 101, but is almost reflected by the conductor layer 102. Therefore, the conductor layer 102 on the beam incident side is subjected to a chemical treatment such as blackening treatment, so that the beam absorption rate to the conductor layer 102 is high. By raising the height, through-hole processing or via processing is performed.

When the above-mentioned conductor layer 2 on the beam incident side is subjected to a chemical treatment such as a blackening treatment, the blackening treatment step by the chemical treatment is added, so that the manufacturing cost is increased. Therefore, by performing wavelength conversion on the conductor layer 102 having a high absorptivity, for example, a fundamental wavelength of 1.06 μm, and processing with a UV-YAG laser beam having a wavelength in the ultraviolet region, the conductor layer 102 is formed. It has been developed to process the insulating layer 101 only with a laser beam.

When the conductor layer 102 and the insulating layer 101 are simultaneously processed by a laser beam, it is necessary to increase the laser energy density, and at this time, the laser beam diameter is narrowed down. Here, when the diameter of the hole to be formed is larger than the diameter of the laser beam, so-called beam scanning processing is performed in which the laser beam 103 is scanned in a desired locus to perform via hole processing on the substrate 104 as shown in FIG. Has been done.

FIG. 19 shows the shape of the through hole 105. a is a view from the upper surface of the processed hole, and b is a sectional view of the processed hole. As a through-hole processing method by beam scanning processing, a laser beam is spirally irradiated by a galvanoscan mirror from a processing trajectory center portion 106 shown in a beam scanning trajectory diagram of FIG. Through-hole processing is performed by setting the scan speed, laser beam output, etc., depending on the thickness, the material of the insulating layer, and the difference in thickness. It should be noted that the laser beam turns on at the same time as the operation of the galvanoscan mirror starts from the machined hole shape central portion 106 shown in FIG. 20, and turns off at the end of operation at the galvanoscan mirror operation end point 107 at the same time.

Next, FIG. 21 shows the shape of the via hole.
When processing the via hole, two-step processing is performed. First, in the processing a (processing the conductor layer 2 portion) of the first step, the processing of the conductor layer 102 is performed by beam scanning as in the through-hole processing. To do. At this time, the insulating layer 101 is set by setting the scan speed, the output of the laser beam 103, etc. so that the inner conductor layer portion 102 does not melt or penetrate when the processing of the first step is completed. Processing is performed halfway. In the second-stage processing b (processing of the insulating layer 101 portion), the laser beam 103a whose output is lowered until damage to the inner layer conductor portion is reduced as shown in FIG.
Thus, similar to the first-step processing, the insulating layer portion is processed by beam scanning processing to form a via hole.

[0008]

In the case of through hole or via hole processing by beam scanning processing,
Since the beam is scanned from the center, if it is made of a resin such as polyimide or epoxy,
As shown in FIG. 2, heat by the beam is accumulated in the insulating layer portion 101, and swelling occurs. In particular, in the case of the composite material as shown in FIG. 23, in which the glass cloth 108 and the epoxy resin insulating layer 101 are mixed, the resin portion 1 is used for processing at high output.
And the difference in the melting point and evaporation point of 108 parts of glass cloth,
This tendency becomes remarkable. Also, in the via hole processing by beam scanning processing, if the insulating layer portion is very thin, the beam does not stop in the middle of the insulating layer in the processing of the first step of processing the surface conductor layer, and the beam reaches the inner layer copper foil, In some cases, the central portion 106 of the inner conductor layer (the bottom surface of the via hole) and the lap portion 107 of the outer peripheral portion shown in FIG. In these cases, variations in the plating thickness occur in the plating process after processing through-holes or via-holes, cause defects such as wire breakage, and are problems in processing quality, and it is a problem to be solved.

It is an object of the present invention to realize high quality laser drilling by eliminating damage to the insulating layer portion and the inner layer conductor portion in the processing of via holes and through holes by beam scanning processing. .

[0010]

A laser processing method according to the present invention is a method for removing a conductor layer and an insulating layer by irradiating a laminated material in which a conductor layer and an insulating layer are laminated with a laser beam in a desired trajectory. The laser irradiation is started with a delay of a predetermined time from the start of movement of the locus.

Regarding the laser irradiation, it is started after the scan mirror for irradiating a laser beam on a desired locus reaches a constant speed.

Regarding the laser irradiation, it is started when the scan mirror reaches a preset number of rotations.

When the laser beam is turned off, the energy of the applied laser beam is gradually reduced.

When the laser beam irradiation is started, the energy of the applied laser beam is gradually increased.

Further, when irradiating with a desired locus, only the outermost peripheral portion is processed with a predetermined laser energy.

Further, for the purpose of processing only the insulating layer portion, the expanded laser beam having a low energy density is irradiated as the second stage processing.

A laser drilling machine for performing beam scanning processing according to the present invention scans a laser oscillator and laser light emitted from the laser oscillator,
An optical unit for irradiating the workpiece and a timing control unit for controlling the laser oscillation timing with respect to the laser oscillator are provided, and the timing control unit is provided when the scanning speed by the optical unit becomes constant. To oscillate the laser.

Also, an adjustment circuit for gradually adjusting the energy of the laser beam emitted from the laser oscillator is provided.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. FIG. 1 is a structural conceptual diagram showing the structure of a UV-YAG laser drilling apparatus according to this embodiment. In the figure, 1 is a laser oscillator, 2 is a laser beam emitted from the laser oscillator 1, 3 is a galvanoscan mirror X for performing X-direction scanning, 4 is a galvanoscan mirror Y for performing Y-direction scanning, and 5 is an fθ lens. , 6 are objects to be processed.

The principle of galvano scanning processing is as follows. The laser beam 2 emitted from the oscillator 1 is scanned by the galvano scan mirrors 3 and 4,
The fθ lens 5 focuses the light on a small spot diameter, and the focused laser beam is applied to an arbitrary position on the workpiece 6. At this time, the galvanoscan mirror irradiates the laser beam on the object to be processed in a desired locus, and operates continuously.

FIG. 2 is a block diagram showing a control mode of the galvano scanning process. The operation of the galvano scanning mirror and the ON / OFF of the pulse output of the laser beam from the oscillator 1 are controlled by the NC device 7 to the DSP board 8
It is performed by a command via. Calculation based on data set in advance in the NC device 7, such as the scanning method of the galvanometer mirror, for example, how many rotations should be performed, the amount of increment from the center which is the starting point per rotation, the scanning speed, etc. The processed value is transferred to the galvano driver device 9 via the DSP board 8.

FIG. 3 shows a galvano speed command from the NC device 7 to the galvano driver device 9 and the oscillator 1 and the beam O.
7 is a timing chart of N and OFF commands. The galvano scan mirror is based on the command value S1 from the NC device 7 for starting scanning, and the center portion P of the machined hole shape shown in FIG.
Scanning starts from 1. After the galvanoscan mirror that has started to operate in an arbitrary increment in a spiral manner from the central portion reaches a constant speed, or when the rotation speed preset in the NC device 7 is reached, that is, P in FIG.
2 from the NC device 7 through the DSP board 8 to the oscillator 1
A beam ON command S2 is issued to the side, the laser beam is pulsed from the oscillator 1, and machining is started. After that, the galvano scan mirror operates for the set number of rotations, and at the same time the operation stop command S3 is received, the beam OFF command is NC.
The data is sent from the device 7 to the oscillator 1 side through the DSP board 8 and the via processing is completed.

In this embodiment, the NC device 7 is connected to the DSP.
Beam ON is started to the oscillator 1 side via the board 8 (S2
Output), and the timing of beam ON can be set arbitrarily. Therefore, the amount of heat accumulated inside the via can be controlled, and swelling to the insulating layer portion at the time of processing the through hole and the via hole can be suppressed. In the via processing, since the spiral-shaped increment for scanning is determined in advance, the rotation speed at which the beam is turned on may be set out of the total spiral rotation speed. Further, in processing a via hole, the timing of turning on the laser beam output can be delayed so that the beam is irradiated when the galvano reaches a constant speed, so the ratio of the beam irradiation amount per single area is constant ( It is possible to control the amount of accumulated heat), and it is possible to suppress damage to the center of the inner conductor layer portion of the processed hole. Further, in the conventional processing method in which the galvano scanning is started from the center and the beam is turned on at the same time, the laser beam is pulsed at a constant frequency from the oscillator. There was a problem that the ratio of the beam irradiation amount per single area increased at the rising part and the central part melted and penetrated, but the laser beam output is turned on so that the beam is irradiated when the galvano reaches a constant speed. Since the timing can be delayed, the ratio of the beam irradiation amount per single area becomes constant (the amount of heat accumulated inside the via can be controlled), and damage to the central portion can be suppressed.

Embodiment 2. In the case of via hole processing, when the insulating layer becomes thin, the timing chart is controlled as in the processing method shown in FIG. 3 to start the beam ON and irradiate the beam when the galvanoscan operation reaches a constant speed. A central portion P1 of the inner conductor layer of the processed hole shown
Damage is prevented, but in the beam wrap portion P3 of the outer peripheral portion of the inner conductor layer in the processed hole, the portion where the surface conductor layer has been processed once is passed through a beam having the same energy output again, so that the outer peripheral portion is processed. Beam wrap portion P3
Melts or penetrates. Therefore, in the present embodiment,
As shown in FIG. 5, the signal from the DSP board 8 is temporarily taken into the output adjusting device 10, and the laser beam output is gradually decreased from P4 immediately before the beam wrap portion P3 shown in FIG. This is to prevent damage such as melting and penetration to the beam lap portion P3 to be formed.

When a beam OFF command is input to the output adjusting device 10, a timer circuit 11 in the output adjusting device 10 is provided.
And the slope circuit 12 performs the processing. Timer circuit 1
In 1, the beam ON extension time T1 shown in FIG. 6 after the beam OFF command from the DSP board 8 is determined, and in the slope circuit 12, the ratio (gradient) of how much the output is reduced within the beam ON extension time T1. Is determined and the oscillator 1 is commanded.

FIG. 6 is a timing chart of the galvano speed command, the command from the DSP board 8 and the beam ON / OFF command. Output adjustment device 10 from DSP board 8
When a beam OFF command is sent to the output adjustment device 10
The beam ON extension time T1 from the above, and the laser beam output is gradually reduced and turned off according to the conditions preset in the output adjustment device 10 for the inclination of the output reduction. Note that when the laser output is reduced, only the peak value of the one-pulse waveform is reduced, and the one-pulse energy is gradually reduced while the pulse width is constant.

According to the present embodiment, the laser output is reduced from the position of P4, and the laser output is stopped at the position of P3 which passes again. Therefore, in addition to the effect of the first embodiment, the processed hole inner layer conductor portion is obtained. It is possible to suppress damage such as melting and penetration to the beam lap portion P3 at the outer peripheral portion of the. Further, in the case of the conventional scanning process, in order to pass the beam of the same energy output again to the part where the surface conductor layer has been processed once, it is melted in the lap part of the outer peripheral part of the inner conductor layer,
Damage such as penetration occurred, and as a result, plating failure occurred in the plating process.However, according to the present embodiment, even when the laser beam output is such that only the insulating layer can be processed when passing through the part that has been processed once. Since it is lowered, damage to the inner conductor layer can be suppressed and a high-quality via hole can be formed, so that the problem of defective plating can be improved.

Embodiment 3. In the case of via hole processing on a substrate where the insulating layer is very thin, the area near the surface of the inner layer conductor may be processed by one scanning operation. Beam wrap portion P3 on the outer periphery of the layer conductor
It becomes difficult to suppress damage such as melting and penetration to the. Therefore, in the present embodiment, in order to perform the beam ON with a predetermined intensity from the position where the galvanoscan operation shown in FIG. 4 reaches the outermost circumference, that is, the beam lap portion P3, the laser beam output by the output adjusting device 13 shown in FIG. Is gradually increased to the processing output, and the beam lap part P
3, the outermost periphery is processed with a predetermined strength, and when the power reaches P4, the output adjustment device 10 gradually reduces the laser beam output to perform the OFF control, thereby damaging the beam lap portion P3 such as melting or penetration. It suppresses.

FIG. 8 is a timing chart of the galvano speed command, the command from the DSP board 8 and the beam ON / OFF command. Galvano scan mirror is NC device 7
Based on the scanning start command value S1 from, scanning is started from the central portion P1 of the machined hole shape shown in FIG. After the galvano-scan mirror which has started to operate in an arbitrary increment in a spiral manner from the central portion reaches a constant speed, or when the rotational speed preset in the NC device 7 is reached, that is, P2 in FIG. Then, when the beam ON command S4 is sent from the DSP board 8 to the output adjusting device 13,
According to the arrival time T2 to the processing output and the slope of the output increase set in advance in the output adjusting device 13, the laser beam output is gradually increased to perform the processing. In the timer circuit 14, the arrival time T2 shown in FIG. 8 after the beam ON command from the DSP board 8 is determined, and the slope circuit 1
In 5, the ratio (gradient) of how much the output is increased within the arrival time T2 is determined and the oscillator 1 is instructed. Here, when the laser output rises, only the peak value of the one-pulse waveform rises, and the one-pulse energy gradually rises with the pulse width kept constant.

Thereafter, when the beam off command is sent from the DSP board 8 to the output adjusting device 10 from the time when the galvano scan operation reaches the portion P4 immediately before the lap in FIG.
According to the beam ON extension time T1 and the slope condition of the output reduction set in advance in the output adjusting device 10, the laser beam output gradually decreases and turns off. When the laser output is reduced, only the peak value of the 1-pulse waveform is reduced, and the 1-pulse energy is gradually reduced while the pulse width is constant, and the via hole processing is completed.

According to the present embodiment, for a substrate having an extremely thin insulating layer, the beam O is output so that a predetermined output is obtained when the galvanoscan operation reaches the outermost circumference of the locus.
At N, the processing output is gradually increased to suppress the processing of the insulating layer portion in the initial stage of turning on the beam, so that in addition to the effect of the second embodiment, the beam wrap portion P3 of the outer peripheral portion of the inner conductor layer portion for processing is further provided. It is possible to suppress damage such as melting and penetration to the.

Fourth Embodiment According to the first to third embodiments,
After the completion of the first-step processing shown in FIG. 9, in the second-step processing of processing the insulating layer portion by the via-hole processing, as shown in FIG. The insulating layer portion is processed by irradiating the laser beam 16 having an energy density such that the inner conductor portion is not damaged. As shown in FIG. 11, a part 17 of the conductor portion remaining during the first step processing is removed when the insulating portion absorbs the laser beam and evaporates, so that there is no damage to the inner layer conductor portion and a high-quality via hole. Can be processed.

Example FIG. 12 shows a conductor layer of 9 μm and insulating layers of 50, 100 and 15
It is an experimental result which evaluated the swelling degree of the insulating layer part at the time of performing through-hole processing by galvano scanning with respect to the sample of 0,200 micrometers. The diameter of the target via hole is φ75 μm, the number of rotations of the galvanoscan mirror is 4 rotations, and the beam ON timing is at the center (beam ON at the same time when the scanning operation starts).
Implementation) When starting from the 1st, 2nd, and 3rd rotations, plating is performed in the plating process, and a good continuity test is marked with a ○. There is. From the experimental results, it was confirmed that a better result was obtained by delaying the beam ON timing and reducing the total energy accumulated inside the via.

In FIG. 13, the conductor layer is 9 μm, the insulating layer is 25,
It is an experimental result which evaluated the damage to the inner layer conductor part at the time of performing a via hole process with respect to three types of samples of 50 and 75 micrometers. The target diameter of the via hole is φ75 μm, the number of rotations of the galvano scan mirror in the spiral direction is 4 rotations, and the beam ON timing is the central part (beam ON is performed at the same time when the scanning operation starts) with or without output control. When starting from the second and third rotations, x is given to the one in which the inner layer conductor portion is melted or penetrated, and o is given to the good one with no damage. According to the experimental results, when the beam ON timing is delayed and the laser beam output is gradually turned OFF while being turned OFF, it is possible to prevent melting and penetration of the outer peripheral wrap portion even for a substrate having an extremely thin insulating layer portion of 25 μm. It was confirmed that it could be processed.

FIG. 14 shows a conductor layer thickness of 9 μm and an insulating layer thickness of 18 μm.
Using the sample of m, the galvano scanning is operated from the center, and the beam is turned on at P5 which reaches the outermost circumference.
FIG. 16 is a state diagram showing a state in which the processing is finished at P6 immediately before wrapping with P5. At that time, output control is beam ON, O
FIG. 15 shows a processing comparison in the insulating layer depth direction when the FF is effective (Embodiment 3) and only when the beam is OFF (Embodiment 2). When processing is performed with the output control enabled when the beam is turned on, the removal of the insulating layer can be stopped at a shallower position of the insulating layer than when output is not controlled when the beam is turned on. It is possible to suppress melting and penetration when wrapping.

[0036]

According to the present invention, in the trajectory processing by scanning using a laser beam having a high energy and a narrowed beam diameter, the laser beam O during the scanning operation is used.
By controlling the N timing, the amount of heat accumulated inside the via hole can be controlled, and high-quality laser beam processing can be realized.

Further, when the beam is turned off, the output of the laser beam is gradually decreased to cause the laser beam to be wrapped, whereby high-quality laser beam processing in which the inner conductor layer does not melt or penetrate can be realized.

Further, even for a substrate having a very thin insulating layer, the laser beam output is gradually increased when the beam is turned on, and the laser beam output is gradually decreased when the beam is turned off so as to lap the inner layer conductor. It becomes possible to realize high-quality laser beam processing in which the layers do not melt or penetrate, and the problem of defective plating can be improved.

[Brief description of drawings]

FIG. 1 is a structural conceptual diagram showing a structure of a UV-YAG laser drilling device.

FIG. 2 is a block diagram showing a control mode of galvano scanning processing.

FIG. 3 is a timing chart of a galvano speed command and a beam ON / OFF command from the NC device to the galvano driver device and the oscillator 1.

FIG. 4 is an explanatory diagram of a scanning operation.

FIG. 5 is a block diagram showing a control mode of galvano scanning processing.

FIG. 6 is a timing chart of a galvanometer speed command, a command from the DSP board, and a beam ON / OFF command.

FIG. 7 is a block diagram showing a control mode of galvano scanning processing.

FIG. 8 is a timing chart of a galvanometer speed command, a command from the DSP board 8, and a beam ON / OFF command.

FIG. 9 is a diagram showing a scanning processed via hole shape.

FIG. 10 is a diagram showing a processing method of the second stage of a via hole.

FIG. 11 is a processing state diagram of a second stage of a via hole.

FIG. 12 is a diagram showing a result of a through hole processing experiment.

FIG. 13 is a diagram showing a result of a via hole processing experiment.

FIG. 14 is a diagram showing a scanning processing shape.

FIG. 15 is a diagram showing comparison of presence / absence of output control at beam ON.

FIG. 16 is a diagram showing a wiring board having conductor layers on both sides of an insulating layer.

FIG. 17 is a diagram showing a wiring board in which insulating layers and conductor layers are laminated in multiple layers.

FIG. 18 is a diagram showing a beam scanning process.

FIG. 19 is a diagram showing a shape of a through hole.

FIG. 20 is a diagram showing a beam scanning locus diagram.

FIG. 21 is a diagram showing the shape of a via hole.

FIG. 22 is a cross-sectional view of a through-hole shape in a poorly processed state.

FIG. 23 is a cross-sectional view of a through hole shape in a poorly processed state.

FIG. 24 is a diagram showing melting positions of inner layer conductor portions.

[Explanation of symbols]

1 laser oscillator, 2 laser light, 3 galvano scan mirror X, 4 galvano scan mirror Y, 5 fθ
Lens, 6 processing object, 7 NC device, 8 DSP board, 9 galvano driver device, 10 output adjusting device (output DOWN), 11 timer circuit, 12 slope circuit, 13 output adjusting device (output UP), 14 timer circuit, 15 Slope circuit.

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Claims (9)

[Claims] 1. A processing method for removing a conductor layer and an insulating layer by irradiating a laminated material in which a conductor layer and an insulating layer are laminated with a laser beam in a desired locus so that the laser irradiation is performed at a predetermined time from the start of movement of the locus. A laser processing method characterized by starting after a time delay. 2. The laser processing method according to claim 1, wherein the laser irradiation is started after the scan mirror for irradiating a desired locus of the laser beam reaches a constant speed. 3. The laser processing method according to claim 1, wherein the laser irradiation is started when the scan mirror reaches a preset rotational speed. 4. The laser processing method according to claim 1, wherein the energy of the laser beam applied is gradually reduced when the laser beam is turned off. 5. The laser processing method according to claim 1, wherein the energy of the laser beam to be irradiated is gradually increased when the laser beam irradiation is started. 6. The laser processing method according to claim 5, wherein only the outermost peripheral portion is processed with a predetermined laser energy when the irradiation is performed on a desired locus. 7. The laser processing method according to claim 1, wherein an expanded laser beam having a low energy density is irradiated as the second step processing. 8. A laser oscillator, an optical unit for scanning a laser beam emitted from the laser oscillator and irradiating a workpiece, and a timing control unit for controlling a laser oscillation timing with respect to the laser oscillator. And
A laser drill machine for performing beam scanning, wherein the timing controller causes laser oscillation when the scanning speed of the optical unit becomes constant. 9. The laser drill machine according to claim 8, further comprising an adjusting circuit for gradually adjusting the energy of the laser beam emitted from the laser oscillator.