JPH06344227A - Method and device for drilling hole of small diameter - Google Patents

Abstract

PURPOSE:To efficiently and surely remove the clogging of chips in drilling a hole of small diameter, smooth the surface of the inner wall of the hole, and remove burrs by arranging a rotary electrode for the plasma discharge on each side of the material to be drilled. CONSTITUTION:A material 1 to be drilled is carried into a discharge processing device 4 of small diameter by a roller conveyor 5. The plasma discharge is generated between electrodes 2, 3 when holes of small diameter of the material to be drilled within this discharge processing device 4 are arranged opposite to eadch other across this conveyor 5. The shock wave and the thermal energy generated in this operation discharge the chips within the hole of small diameter of the material 1 to be drilled, and the inner wall of the holes of small diameter is smoothed and burrs are removed. The discharge between the tip parts of the electrodes 2, 3 is generated at the position of the holes of small diameter over the full length of the electrodes 2, 3 following this rotation.

Description

Detailed Description of the Invention

[0001]

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

[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, 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.

[0003]

Therefore, according to the present invention,
It is intended to provide a method and a device therefor capable of surely processing chips in a small diameter hole, smoothing an inner wall surface, removing burrs, etc. in a short time.

[0004]

Means for Solving the Problems As a result of intensive studies, the present inventor has solved the above-mentioned problems by causing a plasma discharge between rotating electrodes opposed to each other through a small-diameter hole of a material and generating a shock wave and thermal energy at that time. The inventors have found that it can be solved and have reached the present invention.

That is, according to the present invention, rotating electrodes are arranged on both sides of a material to be processed, and a voltage is applied to the electrodes to perform plasma discharge treatment under an atmospheric pressure of 10 to 2 × 10 ³ Torr to form a small hole in the material to be processed. A small-diameter hole drilling method for a material, which is characterized by working.

The present invention also relates to a material conveying device for a material to be processed, and a small diameter hole forming device for a material comprising rotating electrodes arranged on both sides of the conveying device for plasma electric discharge machining the small diameter hole of the material. Is.

FIG. 1 is a schematic view of a small diameter hole drilling apparatus of the present invention. The left side of FIG. 1 is a plan view and the right side is a side view. In Figure 1,
Reference numeral 1 is a material to be processed, 2 and 3 are rotary electrodes arranged to face each other across a conveyor, 4 is a small-hole discharge processing device, 5 is a roller conveyor, 6 is a holding roller, 7 is a voltage distribution device,
Reference numeral 8 represents a high voltage transformer, and 9 represents an input voltage.

The material 1 to be processed is carried into the small-diameter hole discharge processing device 4 by the roller conveyor 5. When the small-diameter hole of the material 1 to be processed is located between the rotating electrodes 2 and 3 which face each other across the conveyor in the electric discharge processing apparatus, plasma discharge is generated between the electrodes. The small diameter hole is processed by the shock wave energy and the like at that time. It is preferable that a plurality of counter electrodes be installed in the discharge treatment apparatus. After the electric discharge treatment, the material to be processed is carried out by the conveyor.

The electrodes used in the present invention are arranged so as to face each other across the material to be processed on the carrier as described above, and the tips of these electrodes are brought close to each other through a small diameter hole in the material to be processed. At that time, plasma discharge is generated between the electrodes, and shock waves and thermal energy at that time produce effects such as discharging chips in the holes, smoothing the inner wall, and removing burrs. In particular, in the present invention, since the electrodes are of a rotary type, it is possible to generate a discharge between the tip portions between the electrodes at the positions of the small diameter holes by the rotation, so that the small diameter holes of the material to be processed are Even if it is distributed over the entire length of the electrode, the small number of holes can be processed surely quickly and surely by increasing the rotation speed of the electrode and disposing a plurality of opposing electrodes.

Further, in the present invention, the rotary electrode can be divided into two or more parts by the insulating material, and the discharge voltage to each divided electrode can be supplied through the distributor. In this case,
It is possible to reliably generate discharge at a plurality of locations at the same time. The energy generated during discharge such as a shock wave gradually weakens after the start of discharge. Therefore, by dividing the electrodes, strong discharge energy can be simultaneously generated at a plurality of positions. Similarly, even if the electrodes are not divided, it is more effective that the discharges occur intermittently rather than continuously. This is because in the case of continuous discharge, the energy gradually decreases. Whether the discharge generated between the rotating electrodes is continuous or intermittent depends on the structure of the electrodes.

The electrode used in the present invention includes a conductive metal,
A conventionally known material such as carbon or a conductive organic material can be used. In addition, the tip of the electrode is platinum or cermet,
Those coated with a metal carbide such as tungsten carbide and titanium carbide can also be preferably used.

Next, the geometrical structure of the rotary electrode used in the present invention will be described. The electrodes used in the present invention are of a rotary type, and they are cylindrical and are arranged so as to face each other with a transport device interposed therebetween. The surface has convex portions of various shapes, and plasma discharge is generated between the tip portions. The discharge state depends on the electrode spacing, atmospheric pressure, atmosphere, and applied voltage, but is also affected by the shape of the rotating electrode.

2 to 23 exemplify preferable shapes of the rotary electrode used in the present invention. (In the figure, only one of the opposing electrodes is shown).

In FIG. 2, small projections are arranged on the entire surface of the electrode. The rotating electrode with such a shape
For example, it can be formed by the following method. For example, a method of applying an insulative coating on the surface of the electrode in spots and then electrolytically corroding the same, or depositing a corrosion-resistant material such as titanium in spots and treating it with a corrosive agent. The characteristic of this electrode is that the electric field strength at the protrusions is high and discharge occurs between the protrusions of the rotating electrode. However, as the protrusions move along with the rotation, the discharge also moves along the electrode surface and tends to become a continuous discharge. Of course, if the shape of the protrusion is sharpened, intermittent discharge is likely to occur. The one shown in FIG. 3 is a wire brush type, the electric field strength at the tip is remarkably high, and discharge occurs between the tip of the needle on the electrode surface and the tip of the counter electrode. It moves intermittently to the tip of the other needle, resulting in intermittent discharge. Therefore, when this type of rotating electrode is used, the initial discharge voltage is high and the shock wave generated at that time is also large. What is shown in FIG. 4 is a screw-shaped electrode provided with spiral irregularities, and continuous discharge occurs depending on the rotation direction, and the discharge point moves in one direction of the electrode longitudinal direction with rotation.

The rotating electrode shown in FIG. 5 is provided with crossed spiral irregularities, and its characteristic is that the discharge is continuously generated in any rotation direction, and the discharge is generated in any of the left and right directions of the electrode longitudinal direction with the rotation. Also moves. In FIG. 6, teeth having a rectangular cross section are provided at an angle with respect to the horizontal, and by rotating the counter rotating electrode in the same direction or in the opposite direction,
Discharge is generated continuously or intermittently. In FIG. 7, the teeth of FIG. 6 are provided in a continuous spiral shape, and the rotation intermittently displaces the discharge to move left and right in the longitudinal direction of the electrode. What is shown in FIG. 8 is a spirally wound wire, which is further formed into a cylindrical shape. Depending on the degree of contact between the wires, it will be continuous discharge or intermittent discharge. The wire brush type shown in FIG. 3 is provided spirally in FIG. 9, and the discharge is intermittent and moves to the left and right. 10 and 1
1 shows a rotary electrode of the type shown in FIG. 8 inserted into a tube having a rectangular or star-shaped opening with an acute angle,
An arc-shaped wire is projected from the opening. These can be intermittent discharges. Especially Figure 1
In the case of the No. 1 type, the electric field strength at the tip of the wire electrode protruding from the acute angle portion of the opening becomes high, and intermittent discharge with a short discharge interval can be realized. Further, FIGS. 12 and 13 show a modification of the rotating electrode, in which electric discharge is generated between the leading ends of the conductive rubber-like sheet having innumerable electrodes.
In FIG. 12, the rotation of the screw-shaped electrode causes the conductive sheet to make a wavy motion and the discharge point moves. Further, in FIG. 13, the roller is moved on the conductive rubber-like sheet to change the gap between the electrodes to move the discharge. The conductive rubber is not particularly limited, but it is particularly preferable to use conductive carbon black or fine powder of a metal such as Al, Ni, Ag mixed and dispersed in silicone rubber. A sheet in which a conductive rubber is molded to form a convex portion on the surface is used.

14 to 23 show the rotary electrodes of FIGS. 1 to 11 divided by an insulating material. A discharge voltage can be supplied to each of the divided electrodes from the distributor, or can be intermittently supplied by turning the power on and off by an electric pulse signal.

The processing atmosphere used in the present invention is any of air, non-oxidizing gas, reaction gas and steam.

For example, in the case of a substrate made of a material having good heat resistance and corrosion resistance such as an alumina substrate or a silicon substrate as a material to be processed, for example, in addition to hydrogen fluoride gas which is generally used for etching ceramics, sodium hydroxide or The potassium hydroxide water is warmed to 50-60 ° C. and made into 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. It has also been found that a substrate such as a flammable paper product may be subjected to plasma discharge treatment in an Ar and N ₂ gas atmosphere.

In addition to this, the processing atmosphere is air, for example, A
r, He, N ₂ and other non-oxidizing gases such as CH ₄ , CC
A reactive gas such as l ₄ and C ₂ H ₂ , for example, vapor such as NaOH steam is appropriately selected and applied.

In the present invention, control of atmospheric pressure is important and is 10T.
If it is less than orr, creeping discharge occurs in addition to the small-diameter hole of the substrate material, and glow discharge occurs, which not only deteriorates the plasma discharge treatment efficiency of the target hole, but also treats unnecessary points of plasma discharge treatment. Is coming. Also 2x
When it exceeds 10 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 electrode condition is also important, and first, the distance between the two electrodes is preferably in the range of 0.01 to 50 mm. If the thickness is less than 0.01 mm, the thickness of the VLSI substrate is 0.005 mm, which is currently the thinnest substrate.
The electrode interval is 0.01, and the electrode interval is 50.
If it exceeds 10 mm, the peak voltage between the electrodes needs to be 50,000 V or more, and when the small holes in the substrate material are spaced by 10 mm, the discharge is distributed not only to the small holes close to the electrodes but also to the small holes far from the electrode, so the plasma discharge treatment effect is halved. To do. 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. When τ _ON of the voltage waveform is less than 5 μs, it becomes difficult for discharge to occur. Further, if it exceeds 20 s, any substrate material causes a partial scorching phenomenon, and the purpose is not achieved. 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 present invention can be applied to a material having a small diameter hole, but is particularly suitable for various substrate materials.

[0022]

EXAMPLE A type shown in FIG. 15 was adopted as a rotary electrode, and this was divided into eight equal parts with an insulating material. This electrode is shown in Figure 1.
A three-stage type device as shown in FIG.

Thickness 1.6 mm, length 33 cm, width 40 cm
Each of the copper-clad glass fiber-containing resin substrates has a hole with a diameter of 0.2 mm.
Drilled at intervals. The number of holes is 4,500,
During the step processing, from the position of 430 holes, the clogging of chips became remarkable, the inner wall of the hole became rough, and the burrs increased.

The substrate was placed on a roller conveyor and conveyed at a moving speed of 2 cm / sec. The discharge conditions are as follows: atmosphere is air, 760 Torr, 2 poles is 8 m apart.
m, τ _ON is 10 ms, peak voltage is 12000V
At, plasma discharge treatment was performed. As a result, there was almost no cutting chips inside the hole, and the inner wall surface of the hole was smoothed due to melt oxidation such as glass fiber and resin protruding due to plasma discharge, resin protruding, etc., and there was almost no burr.

[0025]

According to the method of the present invention, since the rotating electrode is used, the discharge point can be generated at the position of the small diameter hole over the entire length of the electrode. The wall surface can be smoothed and burrs can be removed efficiently and reliably.

[Brief description of drawings]

FIG. 1 is a schematic view of a small diameter hole drilling device of the present invention.

FIG. 2 is an explanatory diagram showing an example of a rotating electrode used in the present invention.

[FIG. 3] Same as above

[Fig. 4] Same as above

[FIG. 5] Same as above

[FIG. 6] Same as above

[FIG. 7] Same as above

[FIG. 8] Same as above

[FIG. 9] Same as above

FIG. 10 Same as above

[FIG. 11] Same as above

FIG. 12 Same as above

[FIG. 13] Same as above

FIG. 14 is an explanatory diagram showing an example of divided rotary electrodes used in the present invention.

FIG. 15 Same as above

FIG. 16 Same as above

FIG. 17 Same as above

FIG. 18 Same as above

FIG. 19 Same as above

FIG. 20 Same as above

FIG. 21 Same as above

FIG. 22 Same as above

FIG. 23 Same as above

[Explanation of symbols]

 1 Material to be added 2, 3 Rotating electrode 4 Small-diameter hole discharge treatment device 5 Roller conveyor

 ─────────────────────────────────────────────────── ─── 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 (4)

[Claims] 1. A rotary electrode is arranged on both sides of a material to be processed,
A voltage is applied to this electrode and the atmospheric pressure is 10 to 2 × 10 ³ To
A small-diameter hole drilling method for a material, which is characterized in that a small-diameter hole is drilled in a material to be processed by plasma discharge treatment under rr. 2. A small hole drilling device for a material comprising a work material carrying device and rotary electrodes arranged on both sides of the carrying device for plasma electric discharge machining a small hole of the material. 3. The method of drilling a small diameter hole in a material according to claim 1, wherein the rotary electrode is divided by an insulating material. 4. The small diameter hole drilling device for material according to claim 2, wherein the rotary electrode is divided by an insulating material.