JP2572201B2 - Method and apparatus for processing small diameter holes in substrate material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently removing chips clogging which occurs when a substrate is subjected to through-hole processing, removing rough surfaces such as smears and deburring, and an apparatus used therefor.

[0002]

2. Description of the Related Art As a material for a printed circuit board widely used in electric equipment, electronic equipment, etc., a thermosetting resin sheet having a copper foil stretched on its surface or a multilayer printed circuit board laminated with the same, especially an epoxy resin containing glass cloth. The thickness of the laminate is 1.
Those having about 6 to several mm are used. Also, a ceramic substrate using a ceramic material such as alumina and having a conductive layer and an insulating layer alternately provided on the surface thereof has been used. In order to provide a desired circuit pattern on these printed circuit boards, in the case of a copper-clad laminate, a through hole called a through hole is provided by micro-drilling using a micro drill, and the upper and lower circuit patterns are plated by plating the inside of the through hole. The continuity between them is measured. Generally, a large number of through holes are provided for one substrate by various drilling machines. The hole diameter is usually 0.5 mm, but a hole having a diameter other than this is used, or a combination of several kinds of diameters is used.

For example, when a through hole is drilled with a micro drill in a multilayer printed circuit board made of an epoxy resin containing glass cloth, the inner surface of the hole becomes rough due to clogging of chips or a drill blade, or the epoxy resin softened by processing heat called smear on the inner surface of the hole. Was developed on the copper foil cutting surface, and burrs were generated on the copper foil. FIG. 1 is a schematic diagram of a cross section of a through hole where a smear is seen. A smear 2 is attached to the inner surface of the through hole 1. In general, if the feed of the drill is too large, the inner surface of the hole becomes rough, and if it is too small, epoxy smear tends to occur. If smearing occurs, the plating solution is difficult to enter, and the inner surface of the through hole cannot be uniformly plated with a sufficient thickness, resulting in poor conduction between the upper and lower circuit patterns. For this reason, it has been considered to remove the adhered smear by a physical treatment such as a chemical treatment or ultrasonic cleaning, but it is not sufficient. In any case, clogging of chips, adhesion of smear, generation of burrs, and the like in the through hole are fatal problems for the printed circuit board.

[0004] Therefore, the present inventors have provided an apparatus and a method capable of more reliably and in a short time, removing chips in a small-diameter hole, removing smear on an inner wall surface, and removing burrs in order to address such problems. As a helix, we found that it is effective to discharge between a needle-shaped electrode close to the through hole of the material or an electrode facing through the through hole, and to treat the through hole by the shock wave and heat energy generated at that time. Has already applied for a patent (Japanese Patent Application No. 4-15203).
No. 5, 5-135463, 5-186364, 5-
No. 207728).

The gist of the invention of drilling a small-diameter hole in these substrate materials is as follows. (1) A continuous dry process coating method and apparatus, wherein electrodes are arranged on both sides of a substrate material, surface treatment of fine holes is performed by plasma discharge processing, and then ECR plasma coating processing is performed. (2) A method and an apparatus for processing a small-diameter hole in a material, wherein rotary electrodes are arranged on both sides of a material to be processed, a voltage is applied to the electrode, and plasma discharge processing is performed to process a small-diameter hole in the material to be processed. .

(3) A device for transporting a material to be processed, electrodes disposed on both sides of the device for plasma discharge machining of a small-diameter hole in the material, and a discharge point between the electrodes are moved. An apparatus for machining a small-diameter hole in a material to be processed, comprising a discharge point control means for causing electric discharge substantially in the entire area of the small-diameter hole in the material to be processed, and a method of using the same. (4) An electrode pair consisting of a positive electrode and a negative electrode is arranged on the material to be processed at a small interval, and a voltage is applied to this electrode;
An etching method and apparatus, wherein a material to be processed is etched by generating a corona discharge under a pressure of 10 to 2 × 10 ³ Torr.

[0007] In order to effectively carry out small-diameter drilling of these substrate materials, it is necessary to inspect whether or not the through holes are complete in the printed circuit board after the drilling process. In addition, the large size and the sometimes different diameter make the inspection difficult. The inspection is performed by selecting a printed circuit board to be a sample and cutting it along a plane passing through the diameter of the through-hole, so as to enlarge the cut surface that has appeared. According to the inspection based on such cutting, even if smear is attached to the through hole, the smear is removed at the time of cutting and may be judged as a non-defective product, which is an inspection lacking reliability. In addition, it is troublesome to inspect many and many types of through holes, and there is a drawback that it is a destructive inspection. Therefore, it has been desired to develop a method of automatically inspecting all the through holes of all the printed circuit boards in a non-destructive manner and passing the inspections to the next small-diameter hole processing step.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and a processing apparatus for processing a through hole in a substrate, and to make it possible to automate the processing of a small diameter hole.

[0009]

Means for Solving the Problems As a result of intensive studies, the present inventors have previously recorded the position and hole size of each through hole, and changed the discharge conditions based on this to change the hole diameter. It completely treats all through holes, large and small, and guides small hole drilling to full automation. That is, the first aspect of the present invention is the method of plasma discharge machining through holes bored in printed <br/> board, a first step of recording the location and the hole size of each through hole on the printed circuit board and, A second step of adjusting an electrode interval and / or a voltage of the plasma discharge based on the data obtained in the first step.
This is a method for processing small-diameter holes in printed circuit board materials.

A second invention of the present application is a first device for detecting and recording the position and size of a through hole formed on a printed circuit board, and a plasma discharge based on data detected by the first device. Adjust the electrode spacing and / or voltage
This is a device for processing a small-diameter hole in a printed board material, comprising a second device for performing a plasma discharge. In either of the above two inventions, not only when the first step or apparatus and the second step or apparatus are separated, but also by performing the first step or apparatus and the second step or apparatus simultaneously and continuously, The case where the first step or apparatus and the second step or apparatus are substantially one step or apparatus is also included in the present invention.
In the following description, a case where a through hole is drilled by using a micro drill in a multilayer printed board on which a copper foil-coated glass cloth-filled epoxy resin is laminated will be described as an example, but the invention is not limited thereto. Even with laser or discharge, problems such as smears occur to some extent. Similarly, for the ceramic substrate, it is necessary to remove the smear or the like of the through hole that has been drilled and process the small diameter hole.
The method and apparatus for processing a small diameter hole according to the present invention are applied to all these printed circuit boards.

[0011] In the present invention, a small-diameter hole is formed in a substrate material.
Plasma discharge is used. The shape of the electrode is a fine needle, and the tip may be sharp or may be curved and round.

Hereinafter, the first and second inventions of the present application will be described in detail with reference to the drawings. The first step of recording the position of each through hole and the hole size is to determine at which position in a substrate there is a through hole having a diameter of how many mm, and convert it into data. FIG. 2 is a schematic diagram of a printed circuit board. The size of the printed circuit board 3 varies in size depending on the purpose of use.
The position of the through hole 1 is determined by the X-axis coordinate and the Y-axis coordinate, and is recorded together with the hole size. If design data for drilling a printed circuit board is available, this can be used, which is the simplest.

When the design data cannot be used directly, as shown in FIG. 3, the printed circuit board 3 is moved in the X-axis and Y-axis directions by an NC automatic positioning device, and the light from above the printed circuit board is located at the position of each through hole. Is irradiated.
In FIG. 3, a laser beam emitted from a light source 4, for example, a laser source, is converted into a wide parallel beam by a lens 5. The parallel light is stopped by the stop / slit 6 so as to be a straight line having a certain direction on the X-axis-Y-axis plane, and passes through the through hole of the printed circuit board 3. The laser light that has passed through the through hole is diffused by the lens 7 and stopped down by the stop 8 having a constant diameter, and the light amount is measured by the optical sensor 9. The light quantity measurement is performed not only once, but also two or more times by rotating the slit 6 at a certain angle on two or more straight lines having different directions on the X-axis-Y-axis plane. In FIG. 4, the amount of transmitted light having a linear cross section in the directions (b) and (d) is reduced by the smear 2 attached to the through hole. As a result, the hole size is measured smaller than the actual diameter, which is inconvenient. However, if measurements are taken in four directions, for example (a), (b), (c) and (d), (a) will give the correct diameter of the hole size, and (c) will be close to that. Becomes Therefore, by measuring the same through hole a plurality of times in a plurality of directions, the maximum value among them may be recorded as the hole size. The number of directions is two or more, in which case they are 90 ° with each other and 60 ° with three directions. Generally, two directions are sufficient.

Another method of recording the position and hole size of each through hole is to use the reflection intensity of light. When light of a certain wavelength is irradiated on the printed circuit board surface, the light is reflected by the copper foil on the surface. However, light is not reflected in the portion where the through hole is opened. As shown in FIG. 5, light of a certain wavelength generated by a laser, a light emitting diode, or the like is irradiated to the printed circuit board 3. The amount of the emitted light is measured using an optical sensor such as a photodiode. If the light is directed to the through hole, the light quantity decreases according to its diameter. In addition, even when smear is adhered to the through hole, the reflection of light due to the smear is much smaller than that of the copper foil, so that the hole size can be measured without being affected by the smear. In addition to the method and apparatus using the laser light and the optical sensor and the method using the reflection intensity of light, an image processing technique using a CCD camera can be used for hole position detection.

The second step or apparatus for adjusting the electrode spacing and / or the voltage of the discharge based on the data obtained in the first step or the apparatus includes the step of adjusting the distance between the electrodes of the discharge and / or the voltage depending on the size of the through hole. It adjusts the voltage.

As shown in FIG. 6, a large number of through holes having different hole diameters are formed in the printed circuit board. These electrodes are moved at a high speed on the surface of the printed circuit board, and are moved at a low speed when approaching the position of the through hole. The minute interval between the needle electrode 10 and the opposing electrode 11 is adjusted by moving the needle electrode 10 up and down, and discharge is started when the needle electrode 10 comes near the center of the through hole. In order to remove the through-hole smear etc. by discharging, it is effective to increase the electrode spacing when the hole size is large, and to increase the voltage.On the contrary, when the hole size is small, reduce the electrode spacing. It is effective to reduce the voltage. In the present invention,
The above adjustment is performed by either the electrode spacing alone, the voltage only, or both the electrode spacing and the voltage. At least one of the discharges is a needle-shaped electrode, and the position of the needle-shaped electrode can be accurately matched with the position of the through hole to be processed by the data obtained in the first step or the apparatus.
In FIG. 6, only one of the electrodes is a needle electrode, but both upper and lower electrodes may be needle electrodes. Alternatively, the counter electrode terminal may be directly provided on the substrate, which is the material to be processed, without particularly providing the counter electrode as shown in FIG.

In order to completely automate the method and apparatus of the present invention, it is effective to continuously connect the first step or apparatus and the second step or apparatus by a transfer device. In this case, a large number of needle electrodes can be provided in a row so as to cross the direction of travel of the substrate, and the vertical movement of each needle electrode and the applied voltage can be individually controlled. For example, for a printed board having a width of 600 mm, 600 needle electrodes are used at 1 mm intervals. The applied voltage may be a DC voltage or a pulse voltage, but a pulse voltage is preferable in order to prevent scorching of the substrate surface.

[0018]

【Example】

Example 1 A cathode plate and a needle-like positive electrode were used as electrodes, and 400 needle-like electrodes were mounted in a line in a direction transverse to the substrate at intervals of 1 mm. The substrate used was 1.6mm thick, 33cm long, 40c wide.
In the resin substrate containing the glass-fiber-bonded glass fiber having a diameter of 0.2 m, holes of 0.2, 0.3, 0.4, and 0.5 mm in diameter were formed on the entire surface at intervals of 5 mm using an NC drilling machine. The number of holes was 4,500, but during step processing, chip clogging became remarkable from around 400 holes, the inner wall of the holes became rough, and the occurrence of burrs increased. The substrate was placed on a roller conveyor, transported at a moving speed of 3 cm / sec per second, and passed through the first device shown in FIG. 3 and the second device shown in FIG. Discharge treatment conditions are as follows: atmosphere is air, 760 Torr
r, the interval between the two electrodes is 5 to 15 mm, and τ _on is 10 m.
s, the peak voltage was 5000 to 11000 V, and the plasma discharge treatment was performed. As a result, there were almost no chips inside the holes, and the inner wall surfaces of the holes were turned up by glass discharge or resin or resin by plasma discharge, and the protrusions became smooth due to molten oxidation or the like, and there were almost no burrs.

[0019]

[0020]

According to the present invention, there is provided an excellent effect that a through hole of a printed circuit board can be quickly and reliably processed, and automation thereof is possible.
Further, the present invention is useful for increasing the reliability of electric devices, electronic devices, optical devices, and the like in which a printed circuit board is built.

[Brief description of the drawings]

FIG. 1 is a schematic view of a cross section of a through hole showing adhesion of smear.

FIG. 2 is a schematic diagram of an X-Y coordinate on a printed circuit board surface and positions of through holes.

FIG. 3 is an explanatory diagram of an apparatus for recording the position of a through hole and a hole size.

FIG. 4 is a conceptual diagram for examining a hole size of a through hole to which smear has adhered.

FIG. 5 is an explanatory diagram of another apparatus for recording the position and the hole size of a through hole.

FIG. 6 is an explanatory view of an apparatus for electric discharge machining of a through hole.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Through hole 2 Smear 3 Printed circuit board 4 Laser light source 5 Lens 6 Slit / aperture 7 Lens 8 Aperture 9 Optical sensor 10 Needle electrode 11 Counter electrode

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location H05K 3/00 H05K 3/00 K (72) Inventor Yoshinori Shima 768 Ozenji Temple, Aso-ku, Kawasaki City, Kanagawa Prefecture Address 15 (72) Inventor Akira Oba 3-12-89 Miyado, Asaka-shi, Saitama (56) References JP-A-6-55352 (JP, A) JP-A-3-79224 (JP, A) JP-A-4-60597 (JP, A) JP-A-4-41897 (JP, A) JP-A-5-285739 (JP, A) JP-A-5-256702 (JP, A) JP-A-62-167008 (JP, A A)

Claims (8)

(57) [Claims] 1. A method of plasma discharge machining through holes bored on a printed circuit board, a first step of recording the location and the hole size of each through hole on the printed circuit board, and the data obtained in the first step Based on plasm
A method for processing a small-diameter hole in a printed circuit board material, comprising a second step of adjusting an electrode interval and / or a voltage of a ma discharge. 2. A first step of recording a position and a hole size of each through hole is to move a printed circuit board in the X-axis and Y-axis by an NC automatic positioning device, and to emit light from above the printed circuit board at each through hole position. 2. The method for processing a small-diameter hole in a printed circuit board material according to claim 1, wherein the hole size is detected and measured by measuring the amount of light radiated and passed in at least two directions on an X-axis-Y-axis plane. 3. A first step of recording a position and a hole size of each through-hole is to move the printed board in the X-axis and Y-axis by an NC automatic positioning device, and to emit light from above the printed board at the position of each through-hole. 2. The method for processing a small-diameter hole in a printed circuit board material according to claim 1, wherein the irradiation is performed, and the reflected light intensity is measured by an optical sensor also above the printed circuit board to detect and record the hole size. 4. A first step of recording the location and the hole size of each through hole is, printed circuit <br/> plate material according to claim 1, wherein the design data is to use the time of processing drilling the printed circuit board Small hole drilling method. 5. A first device for detecting and recording a position and a hole size of a through hole formed on a printed circuit board, and an electrode interval and / or a voltage of a plasma discharge based on data detected by the first device. A small-diameter hole processing device for printed circuit board material, comprising a second device for adjusting the pressure and performing a plasma discharge. 6. detecting the position and hole size of the through hole of bored in printed circuit board, a first device for recording, purine
NC automatic positioning device for moving the door substrate in the X-axis -Y-axis, printed circuit board above the light source, the slit diaphragm for the lens to collimate light irradiation light with a wide, parallel beam with a width in a slit shape, and the substrate 6. The apparatus for processing a small-diameter hole in a printed circuit board material according to claim 5 , comprising a lower optical sensor. 7. detecting the position and hole size of the through hole of bored in printed circuit board, a first device for recording, purine
NC automatic positioning device for moving the door substrate in the X-axis -Y-axis, claim 5 above the substrate of the light irradiation apparatus, and those composed of an optical sensor which measures the intensity of reflected light from the same substrate above
A small-diameter hole processing device for the printed circuit board material described in the above. 8. A plasma discharge interval and / or voltage regulator to the second device mounting apparatus of the printed circuit board to a plasma discharge electrode to be disposed vertically across the substrate to generate plasma discharge, and 6. A small-diameter hole processing method for a printed circuit board material according to claim 5 , wherein at least one of these electrodes is a needle-like electrode, and the device comprises a device for vertically moving at least one needle-like electrode to adjust the interval between these electrodes. apparatus.