JPH07241732A - Board material small diameter hole machining method - Google Patents

Abstract

PURPOSE:To eliminate chip clogging and burrs and smooth the inner wall surface of a hole positively in a short time in the small diameter hole machining of board material. CONSTITUTION:Electrodes are located on both sides of board material to be machined. Voltage of such waveform that positive voltage applying time tauon and negative voltage applying time --tauon are alternately repeated, or voltage of waveform with d.c. voltage superposed thereon is applied to the electrodes, and plasma electric discharge treatment is applied under on air pressure of 10 to 2X10<3> Torr to machine the small diameter hole of the board material to be machined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for surely carrying out a chip clogging process for small-diameter holes in a substrate and a removal of inner wall roughness at a high speed.

[0002]

2. Description of the Related Art Conventionally, a glass fiber-containing epoxy resin substrate with a double-sided copper coating, which is a substrate material for electronic devices, is often drilled with a hole having a diameter of 0.3 mm or more. It was common to remove it by washing or the like. However, recently, the wiring has been made into a fine pattern,
The density is increasing and the number of layers is increasing, and the diameter of through holes is also small, from 0.25 mm to 0.1 mm.
Due to problems such as wear and breakage of the drill blade, there are many cases in which chips are clogged, the inner wall is roughened, and burrs are generated, and it is becoming impossible to remove chips, roughen the inner wall and remove burrs by the ultrasonic cleaning method.

Further, as a conventional substrate dirt cleaning method using plasma discharge, a method is used in which a substrate is placed at the center in a vacuum container, a large number of linear electrodes are installed on both sides, and a DC voltage is alternately applied to it. There was a method of applying a voltage. In the case of a DC voltage, it is several thousand volts, and in the case of an alternating voltage, several hundred cycles to several megacycles are included. However, in these cases, the degree of vacuum was 1 Torr or less because the purpose is to generate stable plasma discharge. The problem with this method is that the discharge is quiet, and the chips and stains on the substrate can be chemically treated by the ionized reactive groups generated by the plasma discharge of the corrosive gas (fluoride, chloride, etc.) contained in the container. It takes a considerable amount of time to remove by reactive reaction, and chips and the like remain electrostatically attached in the container and are not removed, which is an extremely insufficient method for cleaning the substrate. Furthermore,
The present applicants have found a method of processing a small-diameter hole of a substrate material to be processed by plasma discharge processing under 10 to 2 × 10 ³ Torr without using a low degree of vacuum such as usual plasma discharge. An application has already been filed as Kaihei 5-285895.

According to this, for example, in the case of a substrate using a material having good heat resistance and corrosion resistance such as an alumina substrate or a silicon substrate, sodium hydroxide is used in addition to the hydrogen fluoride gas which is generally used for ceramics etching. And potassium hydroxide water is heated to 50 to 60 ° C. to be alkali vapor. It was found that when the plasma discharge treatment is performed on the substrate hole in the atmosphere of 760 Torr, only the wall surface of the fine hole can be etched three to four times more efficiently than the conventional fluorine acid etching. The voltage waveform used there was such that only positive voltage addition τ _on was repeatedly applied. This machining method using plasma discharge is far superior to the conventional method, but there is room for improvement to remove 100% of clogging of chips, smoothing of the inner wall surface of holes, and removal of burrs in a shorter time. there were.

[0005]

Therefore, according to the present invention,
The purpose of the present invention is to provide a method capable of almost completely completing cutting of small diameter holes, smoothing of inner wall surface, removal of burrs and the like.

[0006]

Means for Solving the Problems As a result of intensive studies by the present inventors, the above-mentioned problems are solved by performing plasma discharge treatment with a voltage of a specific waveform without using a low degree of vacuum as in ordinary plasma discharge. The inventors have found that these problems can be solved and have reached the present invention. That is, the present invention is the following (1) to (3). (1) Electrodes are arranged on both sides of a substrate material to be processed, and a DC voltage is superposed on a voltage of a waveform in which a positive voltage application time τ _on and a negative voltage application time −τ _on are alternately repeated or a voltage of the waveform. Waveform voltage is applied and atmospheric pressure is 10 to 2 × 10 ³ To
A method for processing a small-diameter hole in a substrate material, which comprises processing a small-diameter hole in a substrate material to be processed by plasma discharge treatment under rr.

(2) Electrodes are arranged on both sides of the substrate material to be processed with a distance between the two electrodes of 0.01 to 50 mm, and an atmospheric pressure of 10 to 2
Under × 10 ³ Torr, the voltage of the waveform in which the positive voltage application time τ _on and the negative voltage application time −τ _on are alternately repeated or the voltage of the waveform in which the DC voltage is superimposed on the voltage of the waveform is τ _on and −τ _on.
Is a type selected from alternating sine wave, isosceles triangular wave, square wave, trapezoidal wave, sawtooth wave, general triangular wave, rectangular shock wave, and waveform in which DC voltage is superimposed on these, and the peak voltage is in the interval between two poles. A small-diameter hole drilling method for a base material, characterized in that plasma discharge treatment is performed while changing the total to 10 V to 50,000 V to machine a small-diameter hole in a workpiece. (3) The processing atmosphere is air, non-oxidizing gas, reactive gas,
The method for processing a small-diameter hole in a substrate material according to the above (1) or (2), which is either steam.

As described in (1) to (3) above, the present invention is
When processing small-diameter holes in substrate materials, plasma discharge processing that applies a voltage with a specific waveform under a specific pressure is a chip treatment,
It is found that the smoothness of the inner surface of the hole and the removal of burrs are significantly effective, and the intended purpose is achieved by selectively setting the atmosphere, pressure and peak voltage. In the present invention, control of atmospheric pressure is important and 10 Tor
If it is less than r, creeping discharge occurs in addition to small-diameter holes in the substrate material, causing glow discharge, which not only deteriorates the plasma discharge treatment efficiency of the target hole, but also causes the plasma discharge treatment to be performed to unnecessary points. Is coming. Also, 2 × 1
When it exceeds 0 ³ Torr, there is a problem in increasing the pressure of the plasma discharge treatment apparatus and it becomes difficult for discharge to occur.

The voltage waveform applied in the present invention is
As in the invention described in JP-A-5-285895, the positive voltage application time τ _on is not repeatedly applied every certain time, but the positive voltage application time τ _on and the negative voltage application time −τ. _It is a waveform in which _on is alternately repeated or a waveform in which a direct current voltage is superimposed on the voltage of the waveform, and has the greatest feature of the invention in this respect. Specific examples of these waveforms are a sine wave, an isosceles triangle, a square wave, a trapezoidal wave, a sawtooth wave, a general triangular wave, and a rectangular shock wave, in which a positive voltage application time τ _on and a negative voltage application time −τ _on alternate. is there. These waveforms are shown in FIG. In FIG. 1, τ _on is a positive voltage application time, −τ _on is a negative voltage application time, V _p is a positive peak voltage,
-V _p indicates a negative peak voltage.

FIG. 1 (a) shows a sine wave, (b) an isosceles triangular wave, (c) a square wave, (d) a trapezoidal wave, (e) a sawtooth wave, (f) a general triangular wave, (G) is a typical example of a rectangular shock wave. The present invention includes the case of applying a voltage having a waveform in which the DC voltage V is superimposed on a waveform in which the positive voltage application time τ _on and the negative voltage application time −τ _on are alternately repeated. These waveforms are shown in FIG. Each symbol has the same meaning as in FIG. FIG. 2A shows a DC voltage V having an absolute value larger than a positive voltage application time τ _on and a negative voltage application time −τ _on or a peak voltage V _{p of} a waveform which is alternately repeated.
Shows a waveform in which is superimposed. In this case, negative voltage application time-τ _on
Does not appear, and the positive voltage application time τ _on becomes infinite.
(B) and (c) are when a positive DC voltage is superimposed, that is,
In the case of ┃ + V ₁ ┃> ┃-V ₂ ┃, in the case of (b) it is ┃ + τ _on ┃> ┃-τ _on ┃, and in the case of (c) it is ┃
+ Τ _on ┃ = ┃ − τ _on ┃. (D), (e), when superimposing a negative DC voltage, _{i.e., ┃ + V 1 ┃ <┃} -V 2 ┃
In the case of (d), ┃ ＋ τ _on ┃ <┃−
It is a τ _on ┃, a ┃τ _on ┃ = ┃τ _on ┃ in the case of (e). The waveform on which the DC voltage is superimposed is not limited to these, and includes those in which a positive or negative DC voltage is superimposed on FIGS. 1B, 1D to 1G. However, when the DC voltage is superimposed, τ _on and τ _off are simply repeated,
So-called pulse waveforms are not included.

In the present invention, the electrode conditions are also important,
First, the distance between the two poles is preferably in the range of 0.01 to 50 mm.
If it is less than 0.01 mm, it is currently the thinnest substrate as a VLSI
Since the thickness of the substrate is about 0.005 mm, the electrode interval is 0.01, and when the electrode interval exceeds 50 mm, the peak voltage between the electrodes needs to be 50,000 V or more, and the small hole of the substrate material has an interval of 10 mm. In this case, the discharge is dispersed not only in the small-diameter holes close to the electrodes but also in the small-diameter holes distant from the electrodes, so that the plasma discharge treatment effect is halved. Since the voltage fluctuation rate is ± 2%, 49000V is the limit. Rather, at present, the distance between the small diameter holes is 10 mm or less, so the electrode distance is determined from the maximum peak voltage, and 50 mm is the maximum distance. If the positive voltage application time τ _on of the voltage waveform is less than 0.01 μs, the discharge is unlikely to occur. Also, it is preferably less than 20 s. When the peak voltage is less than 10 V, plasma discharge is unlikely to occur, and even if it occurs, it is a single discharge, which is extremely unstable and the treatment efficiency is low. If it exceeds 50,000 V, it will be dispersed in a large number of small-diameter holes and the efficiency will be reduced, as well as a problem will occur in the safety of the device.

The processing atmosphere is air such as Ar, He,
Non-oxidizing gas such as N ₂ such as CH ₄ , CCl ₄ , C ₂ H ₂
Reactive gas such as, for example, vapor such as NaOH steam is appropriately selected and applied. Particularly, for a substrate such as a paper product which is easily burned, it is preferable to perform plasma discharge treatment in an Ar, N ₂ gas atmosphere. Although the mechanism of the plasma discharge treatment according to the present invention has not been sufficiently clarified, at the same time as the plasma discharge treatment, corona discharge occurs on the inner surface or the surface of the small-diameter hole of the substrate material, and the discharge is a surface corona discharge of many filaments. As a result, a large shock wave is generated, pressure is also generated by the shock wave, chips and the like are blown off, and the dirt on the inner surface of the hole is sufficiently removed by the ions and electrons activated by the discharge.

In this respect, not only is it fundamentally different from the conventional quiet plasma discharge treatment under a high vacuum, but also the discharge is positive compared with the prior art in which the discharge by the present inventors is limited to one direction. The discharge treatment effect is remarkably improved by repeatedly performing the discharge in the opposite direction or by repeating the strength even in one direction.

[0014]

EXAMPLES The present invention will be described in detail below with reference to examples. A resin substrate having a thickness of 0.8 mm, a length of 20 cm, and a width of 30 cm is 0.25 mm in diameter, 0.2 mm in diameter, and 0.2 mm in diameter.
Each hole of 0.15mm is 5m on the whole surface by NC drilling machine.
Drilled at m intervals. The number of holes was 2,300, but during the step processing, 139 was used for the 0.25 mm small diameter drill.
From the 0th hole, the clogging of chips became remarkable. With the 0.2 mm thin drill, from the 680 hole position, 0.15 mm was further increased, and from the 430 hole with the small diameter drill, the chip clogging became remarkable, the inner wall of the hole was roughened, and burrs were frequently generated.

Example 1 Using the above substrate, for a substrate having a hole of 0.25 mm, the atmosphere is air, 760 Torr, the distance between the two electrodes is 10 mm, the positive voltage application time τ _on is 10 ms, and the negative voltage application time −τ _on is Use a sine wave of 10 ms, positive peak voltage is 1
Plasma discharge treatment was performed at 1000V. The treatment time was 2300 holes for 2 minutes, and the NC movement treatment was performed. As a result, the inside of the hole was completely free of chips, and the inner wall surface of the hole was smoothed due to melting and oxidation of the glass fibers and resin protruding due to plasma discharge, and the protrusion was smooth, and there was almost no burr. Also for substrates with holes of 0.2 mm and 0.15 mm, the electrode interval is 8 mm and the positive peak voltage is 9000 V when 0.2 mm, and the electrode interval is 6 mm and the positive peak voltage is 6000 V when 0.15 mm. Processing was performed with a sine wave in the same manner as above, except that the condition was set.

Comparative Example 1 For comparison, the same discharge treatment as in Example 1 was performed except that a voltage having a pulse waveform with a positive voltage application time τ _on of only 10 ms was applied. As a result, at each hole diameter, although it was effective in removing chips inside the hole, the state of the inner wall surface of the hole, and removing burrs, none of them were as good as those in Example 1. FIG. 3 is a diagram in which a CdS photodetector is used to obtain an output voltage according to the amount of light transmitted through a substrate hole, and a state of removing chips in the hole is examined. The vertical axis represents the voltage of the photovoltaic power, which is the voltage of the photovoltaic power proportional to the average light transmission amount of 2300 pieces. 0.25 mm
In the case of, if the drilling is 100% and good, the output voltage is 5
Although it becomes mV, in the plasma discharge treatment method of the present invention, it is 5.
The light transmittance is 100% at 0 mV. The conventional method of ultrasonic treatment was 28% at 1.4 mV, and the plasma discharge treatment method of Comparative Example 1 using only τ _on was 4.9 mV and the light transmittance was 98%. It was found that when the hole diameter was 0.15 mm, the light transmittance was 98% in the plasma discharge treatment of the present invention, whereas it was only 11% in the plasma discharge treatment of Comparative Example 1.

Example 2 Using the above substrate having a hole diameter of 0.15 mm, as in Example 1, the positive voltage application time τ _on and the negative voltage application time τ _on of the sine wave were calculated.
It was varied _on. In the first embodiment, τ _on is 10 ms, −τ
_on for 10 ms, electrode spacing 6 mm, positive peak voltage 600
It was 98% at 0 V, but τ _on was 1 ms and −τ _on was 1 m.
s, the peak voltage was 8000 V, and the electrode interval was 5 mm, the amount of light transmission increased and the transmittance reached 99%.
Furthermore, as a result of setting τ _on to 10 μs and −τ _on to 10 μ, 1
It turned out that it reached 00%. As described above, the plasma discharge treatment is performed by changing the positive voltage application time τ _{on, the} negative voltage application time −τ _on , the peak voltage and the electrode interval according to the material of the object and the hole diameter, and the plasma treatment is performed _on the substrate under the optimum conditions. By doing so, almost 100% of the inner wall of the fine holes could be processed at high speed and reliably.

Example 3 Positive voltage application time τ _on is 10 ms, negative voltage application time −τ _on
Is an isosceles triangular wave, a square wave, a trapezoidal wave, a sawtooth wave, or a general triangular wave of 10 ms, τ _on is 5 ms, no voltage application time τ _off is 5 ms, −τ _on is 5 ms, and τ _off is 5 m again.
Example 1 was repeated using a rectangular shock wave of s. In any of the waveforms, the chips and the like were almost completely removed when the light transmission amount was 98% or more. Example 4 Positive peak voltage is 16000V, negative peak voltage is -60
Plasma treatment was performed under the same conditions as in Example 1 except that a sine wave of 00V was used. As a result, with 100% light transmission,
The chips etc. were completely removed.

[0019]

According to the method of the present invention, chip clogging, smoothing of the inner wall surface of holes, and removal of burrs can be reliably performed in the processing of small-diameter holes in substrates.

[Brief description of drawings]

FIG. 1 is a graph showing the results of testing the effect of the present invention in comparison with the conventional example in terms of the hole diameter and the average light transmission amount with respect to the voltage of the photovoltaic power.

FIG. 2 is a diagram showing various waveforms used in the plasma discharge of the present invention.

FIG. 3 is a diagram showing various waveforms used in the plasma discharge of the present invention.

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[Procedure amendment]

[Submission date] June 30, 1994

[Procedure Amendment 1]

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[Correction method] Change

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The voltage waveform applied in the present invention is
As in the invention described in JP-A-5-285895, the positive voltage application time τ _on is not repeatedly applied every certain time, but the positive voltage application time τ _on and the negative voltage application time −τ. _It is a waveform in which _on is alternately repeated or a waveform in which a direct current voltage is superimposed on the voltage of the waveform, and has the greatest feature of the invention in this respect. Specific examples of these waveforms are a sine wave, an isosceles triangle, a square wave, a trapezoidal wave, a sawtooth wave, a general triangular wave, and a rectangular shock wave, in which a positive voltage application time τ _on and a negative voltage application time −τ _on alternate. is there. These waveforms are shown in Figure 1-7. 1 to 7 , τ _on represents a positive voltage application time, −τ _on represents a negative voltage application time, V _p represents a positive peak voltage, and −V _p represents a negative peak voltage.

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FIG. 1 shows a sine wave, FIG. 2 shows an isosceles triangular wave, FIG. 3 shows a square wave, FIG. 4 shows a trapezoidal wave, and FIG. 5 shows a sawtooth wave .
6 is a general triangular wave, and FIG. 7 is a typical example of a rectangular shock wave. The present invention includes the case of applying a voltage having a waveform in which the DC voltage V is superimposed on a waveform in which the positive voltage application time τ _on and the negative voltage application time −τ _on are alternately repeated.
These waveforms are shown in Figure 8-12. Each symbol has the same meaning as in FIGS. FIG. 8 shows a waveform in which the positive voltage application time τ _on and the negative voltage application time −τ _on are superimposed with the DC voltage V having an absolute value larger than the peak voltage V _{p of the} waveform which is alternately repeated. In this case, the negative voltage application time −τ _on does not appear, and the positive voltage application time τ _on becomes infinite. 9 and 10
Is a positive DC voltage superimposed, that is, ┃ ＋ V ₁ ┃> ┃
In the case of −V ₂ ┃, in the case of FIG. 9 , ┃ + τ _on ┃
> ┃−τ _on ┃, and in the case of FIG. 10 , ┃ + τ _on ┃ = ┃−
τ _on ┃. 11 and 12 show an example in which a negative DC voltage is superimposed, that is, ┃ + V ₁ ┃ <┃−V ₂ ┃. In the case of FIG. 11 , ┃ + τ _on ┃ <┃−τ _on ┃,
In the case of FIG. 12 , ┃τ _on ┃ = ┃−τ _on ┃. The waveform obtained by superimposing a DC voltage is not limited to, positive or FIG 2,4～7 are included those obtained by superimposing a negative DC voltage. However,
By superimposing the DC voltage, simply τ _on and τ _off
Does not include a so-called pulse waveform that is repeated.

[Procedure 3]

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Comparative Example 1 For comparison, the same discharge treatment as in Example 1 was performed except that a voltage having a pulse waveform with a positive voltage application time τ _on of only 10 ms was applied. As a result, at each hole diameter, although it was effective in removing chips inside the hole, the state of the inner wall surface of the hole, and removing burrs, none of them were as good as those in Example 1. Figure 13
FIG. 3 is a diagram in which an output voltage depending on the amount of light transmitted through a substrate hole is obtained by using a CdS photodetector to examine the degree of removal of chips in the hole. The vertical axis represents the voltage of the photovoltaic power, which is the voltage of the photovoltaic power proportional to the average light transmission amount of 2300 pieces. 0.25m
In the case of m, if the perforation is 100% and is good, the output voltage is 5 mV, but in the plasma discharge treatment method of the present invention, the light transmittance is 100% at 5.0 mV. The conventional method of ultrasonic treatment was 28% at 1.4 mV, and the plasma discharge treatment method of Comparative Example 1 using only τ _on was 4.9 mV and the light transmittance was 98%. When the hole diameter is 0.15 mm, the light transmittance is 98% in the plasma discharge treatment of the present invention, whereas it is 11% in the plasma discharge treatment of Comparative Example 1.
I knew it was nothing more than.

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[Brief description of drawings]

FIG. 1 is a diagram showing a waveform used for plasma power generation of the present invention.

FIG. 2 is a diagram showing waveforms used in plasma discharge of the present invention.

FIG. 3 is a diagram showing waveforms used for plasma discharge of the present invention.

FIG. 4 is a diagram showing waveforms used for plasma discharge of the present invention.

FIG. 5 is a diagram showing waveforms used for plasma discharge of the present invention.

FIG. 6 is a diagram showing waveforms used for plasma discharge of the present invention.

FIG. 7 is a diagram showing waveforms used for plasma discharge of the present invention.

FIG. 8 is a diagram showing waveforms used in the plasma discharge of the present invention.

FIG. 9 is a diagram showing waveforms used for plasma discharge of the present invention.

FIG. 10 is a diagram showing waveforms used for plasma discharge of the present invention.

FIG. 11 is a diagram showing waveforms used in the plasma discharge of the present invention.

FIG. 12 is a diagram showing waveforms used for plasma discharge of the present invention.

FIG. 13 is a graph showing the results of testing the effect of the present invention in comparison with the conventional example in terms of the hole diameter and the average light transmission amount with respect to the voltage of the photovoltaic power.

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[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

[Figure 5]

[Figure 6]

[Figure 7]

[Figure 8]

[Figure 9]

[Figure 10]

FIG. 11

[Fig. 12]

[Fig. 13]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Oba 4-chome 2-3, Matsuba-cho, Higashimatsuyama-shi, Saitama (72) Inventor Yoshinori Shima 768, Ozenji, Aso-ku, Kawasaki-shi, Kanagawa 15 (72) Inventor Oba Chapter 3-1289 Miyato, Asaka City, Saitama Prefecture

Claims (3)

[Claims] 1. An electrode is arranged on both sides of a substrate material to be processed,
Positive voltage application time τ _on and negative voltage application time −τ _on
Are alternately repeated or a voltage of a waveform in which a DC voltage is superimposed on the voltage of the waveform is applied, and the atmospheric pressure is 10 to 2 × 1.
A method for processing a small-diameter hole in a substrate material, which comprises processing a small-diameter hole in a substrate material to be processed by plasma discharge treatment under 0 ³ Torr. 2. A gap between two poles of 0.
The electrodes are arranged at 01 to 50 mm and the atmospheric pressure is 10 to 2 × 1.
Under 0 ³ Torr, the voltage of the waveform in which the positive voltage application time τ _on and the negative voltage application time −τ _on are alternately repeated or the voltage of the waveform in which the DC voltage is superimposed on the voltage of the waveform is τ _on and −τ _on. Alternating sine wave, isosceles triangle wave, square wave, trapezoidal wave,
It is a kind selected from a sawtooth wave, a general triangular wave, a rectangular shock wave, and a waveform in which a DC voltage is superimposed on these, and the positive peak voltage is changed to 10V to 50000V according to the interval between the two poles, and plasma discharge processing is performed. A method for forming a small-diameter hole in a base material, which comprises forming a small-diameter hole in a workpiece. 3. The method for processing a small diameter hole in a substrate material according to claim 1, wherein the processing atmosphere is any one of air, a non-oxidizing gas, a reactive gas, and steam.