TWI796963B - Laser processing method of printed circuit board and laser processing device of printed circuit board - Google Patents

Abstract

Provided are a laser processing method of a printed circuit board and a laser processing device of a printed circuit board, which effectively use a laser oscillator to optimize processing efficiency and quality. The laser processing method of the printed circuit board uses a laser oscillator for laser processing, and the laser oscillator oscillates the laser by applying RF pulses. During the laser output period after the application of the RF pulse is completed, the laser oscillation is continued by applying the RF pulse again, and the laser of the desired time is taken out from the continuously oscillating laser to laser the printed circuit board. shot processing.

Description

Laser processing method of printed circuit board and laser processing device of printed circuit board

The present invention relates to a processing method and a processing device of a circuit board, in particular to a laser processing method of a printed circuit board and a laser processing device of a printed circuit board, which are suitable for forming on an insulating layer during the manufacturing process of a packaging substrate. Blind hole (not perforated. Hereinafter, just called hole or BH), the insulating layer is composed of ABF material combined on the copper layer or ABF with PET.

In the conventional combined printed circuit board, on the copper layer, the insulating layer (hereinafter, simply referred to as "insulating layer") and the copper layer formed by resin containing glass fibers or fillers are made as an integral body sandwiching the insulating layer. Objects, and a 40-120 μm hole for interlayer connection is processed by laser, and the hole is plated to connect the surface copper layer and the lower layer copper layer.

First, the configuration of a conventional laser processing apparatus will be described.

FIG. 9 is a structural diagram of a conventional double-headed laser processing device.

A carbon dioxide laser oscillator 1 (hereinafter referred to as a laser oscillator 1 ) outputs a pulsed linearly polarized laser 2 . The light beam arranged between the laser oscillator 1 and the beam splitter 4 The diameter adjusting device 3 is a device for adjusting the energy density of the laser 2 , and the energy density of the laser 2 is adjusted by changing the outer diameter of the laser 2 output from the laser oscillator 1 . That is, the energy of the laser 2 before and after the beam diameter adjusting device 3 does not change. Therefore, since the laser 2 emitted from the beam diameter adjustment device 3 can be regarded as the laser 2 output from the laser oscillator 1, the laser oscillator 1 and the beam diameter adjustment device 3 are collectively referred to as a laser output device hereinafter. 1A. In addition, there are cases where the beam diameter adjusting device 3 is not used.

The beam splitter 4 is disposed between the beam diameter adjusting device 3 and the polarization converting device 5A. The beam splitter 4 divides the laser 2 into the laser 2A and the laser 2B in two directions at right angles. The laser 2A is supplied to the first processing head not shown in the figure; and the laser 2B is supplied to the second processing head not shown in the figure. Here, since the first processing head and the second processing head have the same structure, the following objects with the same structure (symbol 5~symbol 12) are appended with additional words A and B to show the difference, that is, symbols 5A, 6A, and 7A , 8A, 9A, 10Aa, 10Ab, 11A, 12A are applied to the structure of the first processing head, symbols 5B, 6B, 7B, 8B, 9B, 10Ba, 10Bb, 11B, 12B are applied to the first processing head The structure of the two processing heads, and the objects corresponding to the symbols have the same structure. Hereinafter, only the case of the first processing head will be used as an illustration.

The polarization conversion device 5A converts the linearly polarized laser 2A into a circularly polarized laser 6A. In addition, the polarization conversion device 5A is provided with a reflected light blocking mechanism (details are omitted) for blocking the laser beam 6A reflected by the processed part during processing and preventing the laser beam 6A from being reflected by the processed part. The work of damage caused by the laser oscillator 1 able. The flat plate 7A disposed between the polarization conversion device 5A and the galvanometer mirror 10Aa is made of a material (such as copper) that does not allow the laser 6A to pass through, and is optionally formed with a plurality of apertures 8A ( window, in this case a circular through-hole). The plate 7A is driven by a driving device not shown in the figure, and the axis of the selected aperture 8A is coaxially positioned with the axis of the laser 6A. The galvanometer device 9A is composed of a pair of galvanometer reflectors 10Aa, 10Ab, which are freely rotatable around the rotation axis as shown by the arrows in the figure, and the reflective surface can be positioned at any angle. The fθ lens (condenser lens) 11A is provided on the first processing head not shown in the figure. The optical axis positioning device is formed by the galvanometer mirrors 10Aa, 10Ab and the fθ lens 11A. The optical axis positioning device positions the optical axis of the laser 6A at the desired position 12A in the printed circuit board, and is reflected by the galvanometer. The scanning area (that is, the processing area) 12A defined by the rotation angle of the mirrors 10Aa and 10Ab and the diameter of the fθ lens 11A has a size of approximately 50 mm×50 mm. The printed circuit board 13 , which is a workpiece and is composed of a copper layer and an insulating layer, is fixed on the X-Y stage 14 . Moreover, the first processing head and the second processing head can process the printed circuit board 13 of the same pattern, or can process the printed circuit board 13 of different patterns. The control device 20 controls the laser oscillator 1, the beam diameter adjustment device 3, the driving device of the flat panel 7A, 7B, the galvanometer mirror 10Aa, 10Ab, 10Ba, 10Bb, and the X-Y stage 14 (depending on the situation) according to the input control program. It can also be that the first processing head and the second processing head respectively correspond to one X-Y table).

Then, when performing hole processing, move the X-Y table 14 so that the designated processing areas 12A, 12B face respectively behind the fθ lenses 11A, 11B. After all the copper layers in the processing regions 12A and 12B are irradiated once with a beam (that is, one pulse irradiation) to process holes, the insulating layer is processed by one or multiple pulses of irradiation to complete the holes in the processing regions 12A and 12B.

Referring to FIG. 9 and FIG. 10 , FIG. 10 is a graph showing the setting time of the galvanometer mirror and the laser irradiation time, and the horizontal axis in the graph is time.

Among the galvanometer mirror 10Aa and the galvanometer mirror 10Ab of the first processing head, the time during which the positioning time becomes longer in a certain processing location is called the galvanometric time GA of the first processing head (indicated as GA in FIG. 9 GA1, GA2). Among the galvanometer mirror 10Ba and the galvanometer mirror 10Bb of the second processing head, the time during which the positioning time becomes longer in a certain processing location is called the galvano time GB of the second processing head (indicated as GB1, GB2). L1 is one laser irradiation time.

As shown in Figure 10(a), when the printed circuit board 13 processed by the first processing head and the second processing head (or the first processing head and the second processing head respectively correspond to a printed circuit board) processing content In the case of the same and the same current detection time, the laser 2 can be supplied to the two processing heads at the same time. However, as shown in Figure 10(a) and (b), when the processing contents of the first processing head and the second processing head are different, or the detection time GA and GB are different, at this time, in order to The processing head and the second processing head supply the laser 2 at the same time, which requires a long detection time. That is, when GA1<GB1, GA2>GB2, a waiting time of (GB1-GA1) will be generated in the first processing head, and a waiting time of (GA2-GB2) will be generated in the second processing head. Therefore, the overall processing efficiency will decrease.

Problems to be solved by the invention: In recent years, along with the progress of thinning substrates, holes are processed on insulating layers without copper layers on the surface to be used as substrates for packaging. In this case, when the diameter of the hole to be processed is 60 μm or less, the output required for processing is about 20W. Next, an actual processing example will be described.

FIG. 11 illustrates an example of laser irradiation, and the vertical axis is the oscillating laser output; the horizontal axis is time. Also, the upper stage shows a switch for exciting the RF pulse (hereinafter, simply referred to as RF) of the oscillation medium of the laser oscillator 1 .

For example, when processing a 60 μm hole on an insulating layer, according to the output curve A1 with the output adjusted to 20 W, irradiate the laser with an RF time of 20 μs for processing, and then continue to irradiate the laser with the same pulse period once again. That is, the processing time at this time is that the pulse period of the first pulse irradiated after the galvanometer mirror is positioned is 100 μs, and the laser within the second pulse period 100 μs after the first pulse is added The subsequent 80 μs (including the 60 μs time from the RF stop to the laser extinction) becomes 180 μs. Here, unlike the situation of processing a copper layer with a high processing threshold or processing an insulating layer with a thickness exceeding 60 μm after processing the copper layer, it is processing an insulating layer with a low processing threshold and a thickness of only about 30 μm. The heat in the processing part is small, so it is possible to irradiate laser twice in a row.

In addition, as shown in FIG. 11 , the output curve A1 has the first peak output immediately after RF application (the duration of the output is short). This 1st peak output is the standard About 1/2 of the second peak output during the quasi-RF application time (20 μs in this case). In addition, after the RF application is stopped, the energy accumulated in the oscillation medium in the laser oscillator is output as laser. In the situation shown in the figure, the duration of the laser emitted by the oscillating medium in the laser oscillator is about 60 μs.

However, the above processing has the following disadvantages.

(1) Due to the influence of the first peak output, the diameter of the entrance of the processed hole may be increased by 2 to 3 μm.

(2) Due to the fluctuation of the output of the laser, the diameter of the processed hole is uneven.

Here, the output variation of the above-mentioned laser is described using figures.

FIG. 12 is a graph showing the output variation of the second peak output. FIG. 12( a ) shows the situation where the pulse frequency is 1~5KHz, and FIG. 12( b ) shows the situation where the pulse frequency is 1~10KHz. For example, when the intervals of the processed holes are substantially the same, there is almost no change in the second peak output. However, since the intervals of the processed holes are determined by the intervals of the components mounted on the printed circuit board or the positions of the holes connected to the underlying copper layer, they will not be uniform. In this way, because the laser excitation interval (that is, the duty cycle) changes, the gain accumulated in the excitation medium will change, and as shown in Figure 12(a), when the frequency is 1~5KHz The output has a variation of about ±3%, and as shown in Figure 12(b), the output has a variation of about ±5% when the frequency is about 1~10KHz. Therefore, the diameter of the processed hole will vary.

(3) During the RF stop period after the RF application time of 20μs, the accumulated laser The energy in the medium is irradiated to the processing part for about 60 μs from the stop of RF, causing the temperature of the processing part to rise. Even if the temperature rise of the processed part is lower than the processing threshold of the insulating layer, if this period lasts for more than 10 μs, the insulating layer at the bottom of the hole and the wall of the hole will be easily carbonized, and the processing quality of the hole will be reduced.

As described above, it is desired in the industry to make the diameter of the processed holes uniform so as to prevent the quality of the insulating layer from degrading.

An object of the present invention is to provide a laser processing method for a printed circuit board and a laser processing device for a printed circuit board that are excellent in processing efficiency and quality by effectively utilizing a laser oscillator.

The object of the present invention is to provide a laser processing method of a printed circuit board and a laser processing device of a printed circuit board, which effectively use a laser oscillator to optimize processing efficiency and quality.

In order to solve the above-mentioned problems, the first means of the present invention is: a laser processing method of a printed circuit board, which uses a carbon dioxide laser oscillator for laser processing, and the carbon dioxide laser oscillator oscillates by applying an RF pulse. The laser is characterized in that: during the laser output period after the application of the RF pulse is completed, the laser oscillation is continued by applying the RF pulse again, and the desired output is extracted from the continuously oscillating laser. The time of laser for laser processing of printed circuit boards.

The second means of the present invention is the laser processing method of a printed circuit board as described in Claim 1, wherein a sawtooth pulse is generated by controlling the application time of the RF pulse and the stop time of the RF pulse, and Machining takes place by means of the generated sawtooth pulses.

A third means of the present invention is the laser processing method of a printed circuit board according to claim 2, wherein the sum of the application time of the RF pulse and the stop time of the RF pulse, or the application time of the RF pulse is controlled. At least one of the ratios to the rest time of the RF pulse.

The fourth means of the present invention is: a laser processing device for printed circuit boards, using a carbon dioxide laser oscillator for laser processing, the carbon dioxide laser oscillator oscillates the laser by applying an RF pulse, the laser The shot processing device includes a control device.

The control device performs the following control: During the laser output period after the application of the RF pulse is completed, the laser oscillation is continued by applying the RF pulse again, and the laser is taken out for a desired time from the continuously oscillating laser. shot to supply to a processing department.

The fifth means of the present invention is the laser processing device for printed circuit boards as described in claim 4, further comprising a plurality of processing heads, which constitute a framework for distributing laser light from the carbon dioxide laser oscillator to each of the processing heads, any When the positioning of one of the processing heads is completed, the control device supplies lightning to the other processing heads regardless of the positioning state of the other processing heads. shoot.

The effect of the present invention is that: with the above method and device, not only the diameter of the processed hole but also the quality of the wall surface of the hole can be improved. Furthermore, processing efficiency can be improved. In addition, due to the continuous oscillation of the stable laser, when supplying lasers to multiple processing heads, the necessary laser can be supplied to any processing head regardless of other processing heads, so the processing efficiency of the laser processing device can be improved. . In this way, the diameter of the processed hole can be made uniform, and the quality of the wall surface of the hole can be improved, and the processing efficiency can be improved. In addition, since the stable laser can be continuously oscillated, and when the laser is supplied to a plurality of processing heads, the necessary laser can be supplied without affecting other processing heads, so the processing efficiency of the laser processing machine can be improved.

1:Laser oscillator

1A: Laser output device

1e: Energy distribution of the first pulse

2: Laser

2A, 2B: Laser

2A0,2B0:0 sub-light laser

2A1K, 2B1K: 1 optical laser

2e: Energy distribution of the second pulse

3: Beam diameter adjustment device

31~34: Mirror

4: beam splitter

5A, 5B: Polarization conversion device

7A, 7B: Tablet

8A, 8B: Aperture

10Aa, 10Ab, 10Ba, 10Bb: Galvanometer mirrors

11A, 11B: f theta lens

12A, 12B: processing area

13: Printed circuit board

14: X-Y stage

20: Control device

50A, 50B: AOM

61A, 61B: drive parts

A: The opening of AOM is 100%

C: output curve

Ds: Spot diameter of the processed part

DR: target aperture

DR1, DR': Aperture diameter smaller than DR

DB, DB': hole bottom diameter

ep: energy distribution when outputting Wp

ev: energy distribution when outputting Wv

eav: Energy distribution when outputting Wavr on average

GA1, GA2: current detection time of the first processing head

GB1, GB2: current detection time of the second processing head

k: processing threshold of insulating layer

L1: one laser exposure time

Lv0: position of energy level 0

Lv1: The surface position of the insulating layer

Lv2: The position of the bottom surface of the insulating layer

mA: AOM opening m%

P1, P3: output rising part

P2, P4: output switching part

P5: Continue to the next output rising part

Q1~Q6: points

s: distance

T0, T1, T2, Td: time

t0, t1, t2, t4, t8, t9, td1: time

ta: AOM startup time

tg: the time when AOM is closed

TH: 1 sawtooth n rectangular pulse

Tj: 1st peak output moment

tm: pulse period

trf1: RF application time

trf0: RF application stop time

Wj, Ws, Wc, Wd, Wr, Wf: output response

Wav: average output

Wp: upper limit output

Wv: lower limit output

Wpf: The upper limit output that can be processed for filling

Wpr: the upper limit output that can be processed on the insulation layer

Wavh: The average output of the output rising part high

X, Y: direction

△w: Output when RF starts to be applied

△z: cumulative residual output

Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, wherein: Fig. 1 is a diagram illustrating the essentials of the sawtooth wave of the present invention; Fig. 2 is an example of output waveform; Fig. 3 is A diagram illustrating the generation steps of the sawtooth wave of the present invention; FIG. 4 is a diagram illustrating the energy when opening a hole; FIG. 5 is a diagram illustrating the spatial distribution of output energy; FIG. An embodiment of the injection processing device (two-headed laser processing device); Figure 7 is a diagram showing the setting time of the galvanometer mirror and the laser irradiation time; Figure 8 is a diagram illustrating the rectangular pulse when processing an insulating layer containing a filler (filler) Figure 9 is a structural diagram of a conventional two-head laser processing device; Figure 10 is a diagram showing the setting time of the galvanometer mirror and the laser irradiation time; Figure 11 is a diagram illustrating an example of laser irradiation Formula; and FIG. 12 is a graph showing the output change of the second peak output.

FIG. 1 is a diagram illustrating the constituent elements of a sawtooth wave according to the present invention.

In addition, the output curve C (fundamental wave pulse waveform) in Figure 1 is 60% of the rated duty cycle (that is, RF application time/pulse cycle. Hereinafter, "Dty" represents the "rated duty cycle"), frequency 10KHz, and maximum output 250W output curve.

First, the output curve C will be described. When RF is started at time T0, the laser will be output explosively at time T1. After reaching the first peak output at time Tj, it will weaken until time Td, and then turn to increase again. After 60 μs of RF application time from time T0 The second peak output of 250W is reached at the later time T2. Here, during the RF application period, the output shown by the solid line is the output of _N2 gas that is excited by RF and transferred to _CO2 gas via the excitation medium (time T2. Here, the output shown by the dotted line around 60 μs) , and the sum of the output of CO ₂ gas directly excited by RF (that is, the output shown by the dotted line and the output shown by the solid line). Here, if the application of RF is stopped, the output of CO ₂ gas directly excited by RF becomes 0, and after time T2, the energy output of the energy accumulated in the excitation medium in the laser oscillator, that is, N ₂ gas becomes 0. . In addition, the energy accumulated in the excitation medium is output about 60 μs after time T2.

The inventor first confirmed the following requirements through experiments and simulations:

1. Element 1

For example, when oscillating by applying Dty 60% (pulse width 60μs) and 10KHz RF, as shown in the output curve C, the oscillating laser output gradually increases and becomes the maximum at the pulse width 60μs. Also, after the RF application is stopped, the output attenuates. Also, when oscillating within the range of Dty (RF application time/RF period) of the laser oscillator, even if the RF application time changes, the output will still rise along the same output curve (output curve C in Fig. 1). That is, when oscillating at Dty 40% (pulse width 40μs) and 10KHz, the output rises along the output curve C, and becomes maximum at the pulse width 40μs, and attenuates similarly to the above case. In addition, when oscillating under the conditions of Dty 20% (pulse width 20μs) and 10KHz, it rises along the output curve C, reaches the maximum at the pulse width of 20μs, and attenuates similarly to the above situation. Wherein, the place marked P1 in FIG. 1 is the output rising part, and the place marked P2 is the output switching part.

2. Element 2

In the case of using a carbon dioxide laser, RF application is started at time T0, and laser oscillation starts at time T1 due to the excitation output accumulated in the excitation medium, and the output rapidly increases to reach the first peak output Wj at time Tj. After one decay (time Td), the output increases again, and becomes the second peak output when the RF application is stopped.

At this time, time Td is between 0.4 and 0.5 μs from time T0. Even if Dty and pulse width vary, it can be seen that the output response (output change per unit time) Ws at time Td is approximately constant.

3. Element 3

In addition, after stopping the RF application, the laser output was switched from 250W to the output based on the residual energy accumulated in the laser medium. The switching time is 0.4~0.5μs, the output first drops, then rises a little, and then decays. Hereinafter, when the output is switched, the output response when the output falls is called output response Wc, and the output response when the output rises slightly is called output response Wd. This output response Wc is a value that hardly changes even if Dty and the pulse width change. Also, although the output directions of the output response Wc and the above-mentioned output response Ws are different from each other, the magnitudes of the output components are almost the same.

4. Element 4

Figure 2 is an example of the output waveform, that is, the output waveform when the energy accumulated in the waveform excitation medium starts to apply RF again at the end of the pulse period. As shown in Figure 2, if there is a cumulative residual output in the excitation medium at the beginning of the RF application (that is, the oblique line in Figure 2 △z shown at , while the output is △w when RF starts to be applied. Here, △w>0), then when the next (second) pulse period starts to be excited, the excited output will overlap with the residual output as shown in the oblique line, and the output will respond to Ws after 0.4~0.5μs output will increase. In this case, however, the first peak output Wj does not occur. In addition, what is described here is the situation between the first pulse period and the second pulse period, but if it repeats to the nth pulse period, the output intensity of the output response Ws will gradually increase, and relatively cause the second pulse period. Peak output gradually decreases, but stabilizes after about 1 second.

Here, in the situation of FIG. 11 mentioned above, since the surplus energy accumulated in the excitation medium before the start of the second pulse cycle becomes 0, the output curve of the second pulse cycle is the same as the output curve of the first pulse cycle.

Referring to Figure 1, here, the value of dividing the output integral value (that is, the total energy output in the pulse period 0~100μs) of the output curve C continuously oscillating at Dty 60% by the pulse period 100μs is called the average output Wav . In addition, when Dty is fixed and the pulse period is in the range of 20~200KHz, the average output Wav shown in Figure 1 is almost unchanged. On the other hand, when the pulse period is fixed, the average output Wav increases in proportion to Dty. In addition, the output response Wr (see FIG. 3 ) and the output response Wf (see FIG. 3 ) in the tangential direction of the output curve C are values inherent to the preset average output.

Also, sawtooth waves of 100 KHz and 200 KHz are recorded in FIG. 1 , wherein the position marked P3 in FIG. 1 is the output rising part, the position marked P4 is the output switching part, and the position marked P5 is the next output rising part. The details thereof will be described with reference to FIG. 3 .

FIG. 3 is a diagram illustrating the steps of generating a sawtooth wave in the present invention.

After setting Dty=trf1/tm (tm is the pulse period, and is composed of the RF application period trf1 and the RF application stop period trf0) in the output curve C (see Figure 1), the average output Wav is determined. Even if the pulse period tm is shortened, if the ratio of the RF application time trf1 to the RF application stop time trf0 is the same, Dty will be the same, and the average output Wav will not change. Here, the sawtooth wave of the present invention is generated based on the fundamental wave pulse waveform (the above-mentioned output curve C) and the above-mentioned requirements 1-4.

The way the sawtooth wave is generated is described below. The sawtooth pulse of the present invention is generated in the following steps based on the fundamental wave pulse waveform (the above-mentioned output curve C).

Step 1: Take the vertical axis as the output axis, and set Dty, pulse period tm, average output Wav, and upper limit output Wp. Here, the upper limit output Wp is an output (J/s) obtained enough for the irradiation pulse to obtain the target aperture, and is set as a numerical value corresponding to the material threshold. Also, the lower limit output Wv is an output larger than the processing threshold value Wm of the insulating layer.

Step 2: Take the horizontal axis as the time axis, set the point on the lower limit output Wv at time t0 as Q1, and set the point on the lower limit output Wv at time t2 of the pulse cycle as Q6. Then, mark the output response Ws with the point Q1 as the starting point, and set the end point of the output response Ws as the point Q2.

Step 3: Connect the point Q2 with the point Q3 on the upper limit output Wp at time t1 with the output response Wr. Also, time t1 is the end point of trf1 (start point of trf0).

Step 4: Take point Q3 as the starting point and mark the output response Wc, and set The end of the response Wc is output as a point Q4.

Step 5: Mark a small output response Wd on the extension line connecting point Q1 and point Q4, and set the end point as point Q5.

Step 6: Connect the point Q5 and point Q6 with the output line segment Wf. That is, the point Q5 is an intersection point of the extension line connecting the points Q1 and Q4 and the output response Wf starting from the point Q6.

Through the above steps, the sawtooth wave applied to the lower limit output Wv is completed.

Hereinafter, the sawtooth-shaped pulses superimposed on the lower limit output Wv of the polygon formed by the above steps are referred to as "sawtooth pulses".

Also, as described in paragraphs [0067] to [0070] (when the pulse period tm is changed under a fixed Dty... called "sawtooth n rectangular pulse"), the output of the laser oscillator will become In the steady state, as long as the laser oscillator remains in the operating state, the variation range between the average output Wav and the upper limit output Wp is about ±1%.

Figure 1 shows a 100KHz sawtooth pulse and a 200KHz sawtooth pulse generated by the above steps.

Again, as shown in Figure 3, point Q1 and point Q4 are connected with dotted line, then the output surrounded by quadrangular Q1Q2Q3Q4 is as paragraph [0037] to [0039] (Fig. As described in the diagram...the energy accumulated in the excitation medium is output about 60 μs after time T2), it is equivalent to the output of CO ₂ gas directly excited by RF.

Also, when the pulse period tm is changed at a fixed Dty, the output responses Ws and Wc do not change. On the other hand, although the output responses Wr, Wd, Wf will change according to the pulse period tm, the average output will not change.

Also, when Dty is changed at a fixed pulse period tm, the output responses Ws, Wc hardly change, and the output responses Wr, Wd, Wf change relatively little. Also, although the average output varies depending on Dty, each is fixed as a fixed value.

Therefore, by setting the pulse period tm, the RF application time trf1, and the RF application stop time trf0 within the range of Dty, the waveform and output of the sawtooth pulse can be controlled.

In actual processing, the aforementioned waveform generation steps are performed continuously to generate n sawtooth pulses (n is an integer greater than 1, hereinafter referred to as “sawtooth n rectangular pulses”).

Fig. 4 is a graph illustrating energy at the time of hole opening, in which output is shown on the vertical axis and time is shown on the horizontal axis.

Here, assuming that the hole to be processed is the same as the hole described in Figure 11 above, the conventional technology is to process with two pulses at a pulse frequency of 10KHz. There are two laser irradiation times of 20μs, and the processing time is the first pulse The total of the pulse period of 100 μs, the RF application time of the second pulse of 20 μs and the non-excitation time of 60 μs is 180 μs. On the other hand, under the situation of the present invention, as shown in Figure 4, processing with two rectangular pulses of sawtooth 2 with a pulse frequency of 100KHZ can obtain the same pulse energy as the conventional one, and is not affected by the pulse period. , the interval between two rectangular pulses can be set arbitrarily, even if the interval between two sawtooth rectangular pulses is set to 60μs (the known pulse interval is 20μs), the processing time is 100μs. Therefore, according to the present invention, the processing time of 80 μs can be shortened compared with the conventional one.

Next, the present case and the conventional technology will be described with reference to the shape of the machined hole.

Fig. 5 is a diagram illustrating the spatial distribution of output energy, Fig. 5(a) is the case of the present case, and Fig. 5(b) is the case of the conventional technology. The vertical axis represents the standardized energy level and processing depth, and the horizontal axis represents the radial direction of the hole. Among them, Ds represents the spot diameter of the processed part, DR represents the target aperture, DR1, DR' represents the diameter of the hole smaller than DR, and DB, DB' represents the bottom diameter of the hole. Also, Lv0 represents the position of energy level 0, Lv1 represents the surface position of the insulating layer, Lv2 represents the bottom surface position of the insulating layer, and k represents the processing threshold of the insulating layer. Also, ep represents the energy distribution when outputting Wp, ev represents the energy distribution when outputting Wv, eav represents the energy distribution when outputting Wav on average, 1e represents the energy distribution of the first pulse, and 2e represents the energy distribution of the second pulse. In addition, the output Wp, Wv and the average output Wav are as shown in FIG. 3 .

Referring to FIG. 3 and FIG. 5 , the processing steps of this case will be described below corresponding to the radial direction of the processing hole. Also, the energy distribution when the machining diameter increases during the RF application period trf1 is called the diameter increase energy distribution, and the energy distribution when the machining diameter decreases during the RF application stop period trf0 is called the diameter decrease energy distribution. Processing starts with the output response Ws, which is superimposed on the output Wv at the same time as the RF application, with an output rise of about 0.4 μs. Then, processing is performed by increasing the energy distribution according to the processing diameter of the output response Wr. After time trf1, the entrance diameter of the target hole is formed. When the RF application is stopped, the output of the energy distribution is reduced according to the processing diameter Processing is performed in response to Wc, the output response Wd of the slight increase in the processing diameter, and the output response Wf of the energy distribution of the reduction in the processing diameter.

In the above processing steps, processing is performed alternately with spot diameters DR and DB, and DR' and DB'. The output rise at the beginning of processing is steeper than conventional pulses and the irradiation time is shorter. In addition, since the energy distribution diameter after RF application stops becomes smaller and away from the hole entrance and the hole side wall, the heat conduction between the hole entrance and the hole side wall during the insulating layer processing is reduced, so the thermal influence of the insulating layer on the hole wall surface will be reduced, making the hole Quality improvement. Also, since the sawtooth pulse processing is continuously performed, laser irradiation which is not related to processing in the conventional technology is not performed. Therefore, the quality of the hole entrance and the wall of the aperture will be lowered. In addition, since it is not affected by the first peak output, the diameter of the entrance of the hole does not expand.

FIG. 6 is a structural diagram of an embodiment (two-headed laser processing device) of a laser processing device for printed circuit boards of the present invention. The same objects or objects with the same functions as those in FIG. 9 are marked with the same symbols, and detailed description is omitted.

By setting the application time and stop time of the high frequency RF that drives the laser oscillation, a laser oscillator 1 outputs a laser 2 with a continuous linearly polarized sawtooth shape with a frequency above 50KHz. A beam diameter adjustment device 3 disposed between the laser oscillator 1 and a beam splitter 4 is a device for adjusting the energy density of the laser 2 by changing the output from the laser oscillator 1 The outer diameter of the laser 2 is used to adjust the energy density of the laser 2 . That is, the energy of the laser 2 before and after the beam diameter adjusting device 3 does not change. Therefore, since the laser 2 emitted from the beam diameter adjustment device 3 can be regarded as being output from the laser oscillator 1 Therefore, the combination of the laser oscillator 1 and the beam diameter adjustment device 3 is called a laser output device 1A. In addition, there are cases where the beam diameter adjusting device 3 is not used.

An AOM 50A driven by a driver 61A is disposed between the beam splitter 4 and a polarization conversion device 5A. The AOM50A divides a laser 2A into a 1st order laser 2A1K and a 0th order laser 2A0, and adjusts the output of the laser 2A1K for processing by changing the distribution ratio (opening degree). The laser 2A0 that is not used in processing is not diffused to the periphery as much as possible and discarded in a buffer not shown in the figure.

The laser processing device is configured such that a second processing head can be positioned in the X direction relative to a fixed first processing head by a second processing head moving device not shown in the figure. The laser processing device is also configured such that the position of the second processing head can be extended by a maximum distance s relative to the first processing head. The first mirror 31 and the first mirror 34 are fixed at predetermined positions, and the second mirrors 32 and 33 are supported by a first mirror moving device not shown in the figure, and can be freely positioned in the X direction. In addition, the mirrors 31 to 34 are arranged such that the axis of a diaphragm 8B coincides with the center of a galvanometer mirror 10Ba no matter where the mirrors 32 and 33 are located in the X direction. A control device 20 controls the laser oscillator 1, the beam diameter adjusting device 3, the driving parts 61A, 61B of the AOMs, the driving devices of the plurality of flat plates 7A, 7B, and the galvanometer mirrors 10Aa, 10Ab, 10Ba , 10Bb, and an X-Y stage 14 (it can also be that the first processing head and the second processing head respectively correspond to an X-Y stage as the case may be); a moving device and a mirror moving device of a second processing head not shown in the figure.

The processing steps are explained below. Moreover, although the processing content differs for each processing head, since the operation|movement is substantially the same, it demonstrates using the case of this 1st processing head.

After instructing the processing to start, the control device 20 drives the moving device of the second processing head, and moves the second processing head to the specified position. Next, control the X-Y stage 14 to position the first processing head at the processing position, and position the galvanometer mirrors 10Aa, 10Ab at the initial processing position and stand by. In addition, the moving device of the second processing head not shown in the figure is activated to move the second processing head relative to the first processing head by a distance s. Next, the mirror moving device (not shown) is operated to move the position of the mirror 32 by a distance s/2 in the moving direction of the second processing head. In this way, since the distance between the diaphragm 8B and the galvanometer mirror 10Ba becomes constant, the size of the image of the diaphragm 8B can be kept constant regardless of the position of the second processing head.

Then, firstly, the laser oscillator 1 is activated, and after a predetermined waiting time, the processing program is activated to start processing. Here, the reason for setting the waiting time is that the output of the laser oscillator 1 is unstable until the thermal equilibrium is reached, and the waiting time is about 1 to 2 seconds.

Then, after a waiting time, the control device 20 outputs the laser 2 shaped into a sawtooth shape (hereinafter, simply referred to as the laser 2 ) from the laser oscillator 1 according to the pre-input processing formula. The laser 2 is changed in diameter by the beam diameter adjusting device 3, and is split into the laser 2A by the beam splitter 4, and is incident on the AOM 50A. The AOM50A The laser 2A is discarded in the buffer until an operation command is received from the control device 20 . After the control device 20 receives a positioning completion signal of the galvanometer mirror 10Aa, 10Ab which is positioned later among the galvanometer mirrors 10Aa and 10Ab, it actuates the AOM 50A through the driver 61A to drive the laser The 2A output is a rectangular pulse 2A1K composed of n sawtooth pulses attenuated to a predetermined output. The rectangular pulse 2A1K is positioned by the galvanometer mirrors 10Aa, 10Ab, and is incident on a designated position of the printed circuit board 13 to form a hole in the printed circuit board 13 . Hereinafter, as in the conventional case, the above-mentioned opening operation is repeated until the specified processing is completed. In addition, in the above-mentioned processing, the laser oscillator 1 continuously outputs the laser 2 from the start to the end of the processing by turning RF on and off at a predetermined cycle and pulse cycle.

Fig. 7 is a diagram showing the setting time and laser irradiation time of the galvanometer mirror in the present invention, Fig. 7(a) shows the situation of using the first processing head, and Fig. 7(b) shows using the first processing head The situation of two processing heads, and the horizontal axis in Fig. 7 is time. As shown in Figure 7, the lasers 2A and 2B composed of sawtooth pulses are normally output during processing. In the case of the first processing head, after the current detection time GA1 and GA2 are completed, the AOM50A , the rectangular pulse 2A1K composed of necessary n sawtooth pulses is irradiated on the processed portion to form a hole. At this time, the first processing head can continue to work without considering the current detection time GB1, GB2 of the second processing head. Similarly, the second processing head can continue to operate regardless of the current inspection time GA1 and GA2 of the first processing head. Industry. In this way, since each processing head does not need waiting time, compared with the conventional technology, the processing efficiency can be increased by 20-30%. In addition, according to the control clock signal of the device omitted in the figure, after the positioning of the galvanometer mirror is completed, the AOM50A is controlled to match the output with the RF application start time of the first sawtooth pulse, so that the rectangular shape of the sawtooth n supplied to the processing part Pulses are free from defects or omissions.

Next, the configuration of the sawtooth of the present invention will be described in detail.

FIG. 8 is an explanatory diagram for explaining a rectangular pulse when processing an insulating layer containing a filler (reinforcing material), the horizontal axis represents time, and t represents the time based on t0.

In Fig. 8, the upper part shows the operation of the AOM, A is the opening degree of the AOM 100%, and mA is the opening degree of the AOM m%. The middle section shows whether RF is on or off, tm is the pulse period, trf1 is the on time of RF, and trf0 is the off time of RF. The output is shown in the lower row, Wpf is the upper limit output that can be processed for the filler (filler) of the insulating layer, and Wpr is the upper limit output that can be processed for the resin of the insulating layer.

In Fig. 8(a), the laser light path is expanded during RF start-up, mainly to process the filling, and the laser light path is narrowed during RF off-time, so as to quickly remove the gas or processing chips generated by processing from the processing part, so it can be Improve the processing quality of the wall and bottom of the hole. In addition, Fig. 8(b) and Fig. 8(d) are also the same as Fig. 8(a), and the gas or processing chips generated by processing can be quickly removed from the processing part, so the processing of the hole wall surface and the bottom of the hole can be improved. quality.

In addition, FIG. 8(c) is a modification example of the portion surrounded by a dotted line in FIG. 8(a), An example of waveform control in FIG. 8( a ) during the rising of the output from the RF activation period (the AOM is activated only at time ta from time td1 in the figure). In this way, processing with the average output Wavh of the high output riser can make the hole entrance step and the hole wall uniform, and improve the quality of the hole. In addition, tg is the time when the AOM is turned off.

Also, for example, Fig. 8(d) is used when the hole is to be inclined in the depth direction.

Next, a processing example will be described.

Utilize the rectangular pulse of sawtooth n in Fig. 8 (a), (b), (c), or the conventional pulse in Fig. 11, for the insulating layer (ABF material produced by Ajinomoto Co., Ltd., thickness About 30 μm) The results of processing the same hole diameter of 60 μm are as follows. In addition, FIG. 8 shows the shape of a sawtooth pulse instead of a rectangular pulse showing a sawtooth n for machining.

In the situation of Figure 8(a), processing is carried out under the conditions of 2 sawtooth 3 rectangular pulses with a frequency of 100KHz, Dty 60% (trf1=6μs, trf0=4μs), and AOM opening of 100%. The diameter of the hole entrance is about 62μm, the hole (bottom diameter/entrance diameter) ratio is about 80%.

In the situation of Fig. 8(b), processing is carried out under the conditions of 2 sawtooth 3 rectangular pulses with a frequency of 100KHz, Dty 60% (trf1=6μs, trf0=4μs), and AOM opening 0%. The diameter of the hole entrance is about 60μm, the hole (bottom diameter/entrance diameter) ratio is about 80%.

In the situation of Figure 8(c), process with 2 sawtooth 3 rectangular pulses with a frequency of 100KHz, Dty 60%, td1=6μs, and process at AOM opening of 0%, or ta=4μs, at AOM opening 100% conditions for processing, the diameter of the hole entrance is about 60μm, the hole (bottom diameter/entrance diameter) ratio is about 81%.

And in the situation of Fig. 8 (a), (b), (c), almost no carbonization of the resin was found on the surface of the copper layer at the bottom of the hole.

In addition, in the case of the conventional pulse shown in Fig. 11, if the pulse width is 20μs, the pulse frequency is 10kHz, and the number of pulses is 4, the hole entrance diameter is about 65μm, and the hole (bottom diameter/entrance diameter) ratio is about It is 77%. In addition, carbonization of the resin was found on the copper surface at the bottom of the hole. In addition, when the first peak output Wj of the pulse is higher than the second peak output Wp, since the output during processing is increased, ring-shaped damage occurs around the entrance of the hole due to the refracted light of the higher first peak output Wj. .

Also, please refer to Fig. 3, the optimal output response values of Ws, Wc, Wr, Wd, Wf will vary according to the material of the workpiece. Therefore, by setting the values of the output responses Ws, Wc, Wr, Wd, and Wf to the most appropriate values corresponding to the material of the workpiece, the processing quality and processing speed can be improved.

Incidentally, in actual processing, the values of output levels Wp, Wv and output responses Ws, Wc, Wr, Wd, Wf corresponding to each workpiece can be known in advance. In addition, when determining the rated duty cycle and the pulse cycle, the maximum output of the laser oscillator can also be known in advance. Furthermore, the appropriate aperture diameter corresponding to the machining aperture is also known.

Here, if the material is processed for the first time, for example, refer to the previous data first, tentatively determine the value of the energy level Wp, Wv, and compare the hole diameter processed by the experiment with the hole diameter to be achieved, and increase or decrease the output energy level test. Wp to determine the value. Next, with Sawtooth pulse n is used for processing, and the value of n is determined according to the depth of the processed hole. At this time, if n increases, the quality will deteriorate due to the heat of the insulating layer. Therefore, if the value of n is large, the method of dividing n into a plurality of sawtooth m rectangular pulses should be used, and between each rectangular pulse Set the cooling time for the processing part.

In addition, as shown in FIG. 6, if the output of the laser oscillator 1 is 250W, the average output is 125W. Therefore, it is divided by the beam splitter 4, and an output of 62.5W is supplied to each processing head. . Therefore, as described in paragraphs [0092] to [0098] (continuing to describe the processing example...making annular damage around the entrance of the hole), when Wpf=20W, both the first processing head and the second processing head can be used for processing. However, for example, when processing a resin with a PET carrier film (PET carrier film), Wpf=70W is required. Here, if Wpf=70W is required, the output of the oscillator 1 in FIG. 6 needs to be, for example, 500W.

In addition, the laser oscillator described in the example above has an output characteristic such that immediately after RF application, the first peak output is smaller than the second peak output when RF application stops (output curve C, Fig. 11 output curve A1), but it can also be applied to a laser oscillator whose output characteristic is to output a fundamental wave pulse waveform whose first peak output immediately after RF application is larger than the second peak output when RF application stops.

In summary, the laser processing method for printed circuit boards and the laser processing device for printed circuit boards of the present invention can indeed achieve the purpose of the present invention.

But what is described above is only an embodiment of the present invention, and should not be used as The scope of implementation of the present invention is limited, and all simple equivalent changes and modifications made according to the patent scope of the present invention and the content of the patent specification are still within the scope covered by the patent of the present invention.

C: output curve

P1, P3: output rising part

P2, P4: output switching part

P5: Continue to the next output rising part

Q1~Q6: points

T0, T1, T2, Td: time

Tj: 1st peak output moment

Wav: average output

Wj, Ws, Wc, Wd: output response

Claims (5)

A laser processing method for printed circuit boards, using a carbon dioxide laser oscillator for laser processing, the carbon dioxide laser oscillator oscillates the laser by applying an RF pulse, characterized in that: when the RF pulse is applied During the laser output period after the end, the laser oscillation is continued by applying the RF pulse again. After the start of each pulse cycle, the predetermined pulse is continuously applied during the period determined by the rated duty cycle of the carbon dioxide laser oscillator. Frequency of the RF pulse, and the output value of the laser output in each pulse period as an average output, the average output is in any pulse period when the carbon dioxide laser oscillator oscillates continuously at the rated duty cycle Divide the output integral value by the value of the pulse period, and take the pulse of the laser output as the unit to obtain the necessary laser output for processing to carry out the laser processing of the printed circuit board. The laser processing method for printed circuit boards as described in Claim 1, wherein a sawtooth pulse is generated by controlling the application time of the RF pulse and the stop time of the RF pulse, and the sawtooth pulse is in a single pulse period The pulse output of the device presents a sawtooth change, and is processed by the generated sawtooth pulse. The laser processing method for printed circuit boards as described in Claim 2, wherein the sum of the application time of the RF pulse and the stop time of the RF pulse, or the sum of the application time of the RF pulse and the stop time of the RF pulse is controlled at least one of the ratios. A laser processing device for a printed circuit board uses a carbon dioxide laser oscillator for laser processing, and the carbon dioxide laser oscillator is obtained by Applying an RF pulse to oscillate the laser, the laser processing device includes: a control device that performs the following control: during the laser output period after the application of the RF pulse is completed, the laser is continued by applying the RF pulse again Oscillation, after the start of each pulse period, continuously apply the RF pulse of a predetermined frequency during the period determined by the rated duty cycle of the carbon dioxide laser oscillator, and output the laser output in each pulse period Value as an average output, the average output is when the carbon dioxide laser oscillator oscillates continuously at the rated duty cycle, the output integral value in any pulse cycle is divided by the value of the pulse cycle, and the pulse of the laser output is taken as the unit The laser output necessary for processing is taken out to be supplied to a processing part. The laser processing device for printed circuit boards as described in Claim 4, further comprising a plurality of processing heads, forming a framework for distributing laser light from the carbon dioxide laser oscillator to each of the processing heads, when the positioning of any one of the processing heads is completed , the control device supplies laser light to the other processing heads regardless of the positioning state of the other processing heads.

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