JP2002050872A - Method and device for processing surface of multilayer printed board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface processing method for a multilayer printed board for quick and effective surface processing. SOLUTION: A high-frequency power source 21 causes corona a discharge between a first electrode 22 and a second electrode 24. The electric discharge generated at the first electrode 22 converges in a conductive layer 102 exposed within a hole 104 to remove a smear 105 remaining inside the hole 104. A part of the electric discharge generated from the first electrode 22 is made to irradiate on the hole formation surface of a board 100, allowing the hole formation surface to be hydrophilic. With this processing method, a dielectrics 23 coated on the first electrode 22 functions as an aggregate of micro capacitors so that no electric discharge is converged on a specific position, giving no damage on the hole formation surface and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method and a surface treatment apparatus for performing a surface treatment on a multilayer printed circuit board.

[0002]

2. Description of the Related Art A multilayer printed circuit board is formed as a laminated body in which a conductive layer made of metal or the like and having a planar circuit pattern and an insulating layer made of polymer or the like and electrically insulating the conductive layers are alternately stacked and integrated. Have been. In this multilayer printed circuit board, an electric conduction hole called a via hole is provided in the insulating layer to form a three-dimensional electric circuit, and the conductive layers are electrically connected. In the present application, the via hole refers to a blind via hole or the like that does not penetrate the substrate, and is distinguished from a through hole that penetrates the substrate.

Generally, when a hole for a via hole is formed in a multilayer printed circuit board, a residue containing a constituent material of an insulating layer called smear is left on the bottom surface or the inner wall surface of the hole, or metal burrs forming the conductive layer are burred. May occur.
Smear prevents exposure of the conductive layer and causes poor conduction of via holes. Therefore, desmear treatment for removing the smear with an oxidizing agent solution such as a potassium permanganate solution is performed. Further, other wet treatments such as a treatment for removing an oxide film of the conductive layer and a blackening treatment for roughening the inner surface of the hole to improve the plating performance may be performed. Then, the inside of the hole is covered with a conductive plating such as a metal to electrically connect the conductive layers, thereby completing the via hole.

[0004] With the high-density mounting of the multilayer printed circuit board, the required diameter of the via hole is, for example, φ50.
The size has been reduced to about μm, and the smear cannot be sufficiently removed by the conventional wet processing. Therefore, instead of the wet desmear treatment using an oxidizing agent solution, a dry desmear treatment without using a solution or the like is being used. As such a dry desmear treatment, a treatment technique using a plasma discharge, a treatment technique using a corona discharge with a needle-like electrode or a linear electrode, and the like are known, and such treatment techniques are disclosed in Japanese Patent Application Laid-Open No. 8-215934. Gazette, JP-A-3-268
No. 889, Japanese Unexamined Patent Publication No. 3-28087, Japanese Patent No. 2625078, Japanese Patent No. 2500293,
Japanese Patent No. 2572199, JP-A-8-132392
Patent, Japanese Patent No. 2572201, Japanese Patent No. 2614
No. 697, Japanese Patent No. 2618211, Japanese Patent No.
680986, JP-A-60-225493, JP-A-61-36991, JP-A-5-175
No. 069, JP-A-62-98798 and JP-A-7-99378.

[0005]

However, the conventional processing technique using plasma discharge as disclosed in Japanese Patent Application Laid-Open No. 3-268889 has the following problems. In other words, when plasma discharge is used, the object to be removed is only an organic substance of about 100 °,
It takes time to remove the thicker organic layer,
Inorganic substances could not be removed. Further, since plasma does not easily enter the inside of the via hole, it is difficult to remove the smear, especially inside the small diameter hole. Furthermore, the processing technology using plasma discharge requires large-scale equipment and work for stabilizing plasma, and thus costs and labor are required.

On the other hand, in the conventional processing technique using corona discharge with a needle-shaped electrode as disclosed in the above-mentioned Japanese Patent No. 2625078 or the like, although the problem caused in the processing technique by plasma discharge can be solved, the needle-shaped electrode is used. Since the electrodes need to be accurately arranged in the vicinity of the holes, it is difficult to accurately position the needle electrodes when a large number of holes are irregularly arranged. In addition, Japanese Patent Application Laid-Open No. 8-215
In the conventional processing technique using corona discharge by a linear electrode as disclosed in Japanese Patent No. 934, although the difficulty of alignment is reduced, the discharge tends to be unstable,
There is a case where current concentration occurs in one place and the arc transition occurs, and the substrate surface may be damaged.

An object of the present invention is to provide a surface treatment method and a surface treatment apparatus for a multilayer printed circuit board capable of performing a quick and effective surface treatment by solving the above problems of the conventional treatment technology. Aim.

[0008]

SUMMARY OF THE INVENTION A surface treatment method for a multilayer printed board according to the present invention is a method for performing surface treatment on a multilayer printed board comprising a laminate in which conductive layers and insulating layers are alternately laminated. A first arrangement in which a first electrode is arranged at a position facing a hole forming surface in which a hole for a via hole reaching the conductive layer is formed, and a dielectric is arranged between the hole forming surface and the first electrode; A step of arranging a second electrode at a position facing the first electrode with the multilayer printed circuit board interposed therebetween; and applying a voltage between the first electrode and the second electrode to form the first electrode. A discharge step of generating a corona discharge between the conductive layer and the conductive layer.

Further, the apparatus for treating the surface of a multilayer printed circuit board according to the present invention is an apparatus for performing a surface treatment on a multilayer printed circuit board comprising a laminate in which conductive layers and insulating layers are alternately laminated. A first electrode disposed at a position facing a hole forming surface in which a via hole to be formed is formed; a dielectric disposed between the hole forming surface and the first electrode; A second electrode disposed at a position facing the first electrode, and a voltage applied between the first electrode and the second electrode to generate a corona discharge between the first electrode and the conductive layer. And an application unit.

According to these inventions, the dielectric is arranged between the hole forming surface and the first electrode, so that the dielectric functions as an aggregate of minute capacitors, and discharge is concentrated at a specific position. Play a role to prevent. Therefore, it is possible to suppress the transition to the arc discharge as in the conventional processing technique using corona discharge by the linear electrode, and to remove the smear inside the via hole without damaging the hole forming surface and the like. It becomes possible. Further, since the hole forming surface can be made hydrophilic by corona discharge, it is possible to easily perform wet treatment, plating treatment, and the like even for small-diameter holes.

In the method for treating a surface of a multilayer printed circuit board, in the first arranging step, a linear electrode is used as the first electrode.
It is also preferable to dispose electrodes in which discharge points are continuous in a grid or plane.

In the apparatus for treating a surface of a multilayer printed circuit board, it is also preferable that the first electrode is an electrode having a continuous discharge point in a linear, lattice or plane shape.

As in these inventions, the first electrode is linear,
If the discharge points are arranged continuously in a grid or plane, the problem of difficulty in alignment as in the above-described conventional technique using corona discharge by needle electrodes does not occur. In addition, since the first electrode has a structure in which the discharge points are continuously arranged in a grid or a plane, processing can be performed on the entire hole forming surface at one time, and the processing time can be reduced. .

In the method for treating a surface of a multilayer printed circuit board, in the first disposing step, as the first electrode,
It is also preferable to arrange a plurality of electrode members.

In the apparatus for treating a surface of a multilayer printed circuit board, it is preferable that the first electrode is constituted by a plurality of electrode members.

If the first electrode is composed of a plurality of electrode members as in these inventions, a large number of holes can be processed at one time, and the processing time can be reduced.

In the method for treating a surface of a multilayer printed circuit board, in the first disposing step, as the first electrode,
It is also preferable to dispose electrodes in which the length of the discharge point in the longitudinal direction is equal to or longer than the length of the diagonal line of the hole forming surface.

In the apparatus for treating a surface of a multilayer printed circuit board, the first electrode preferably has a discharge point in the longitudinal direction having a length equal to or longer than a diagonal length of the hole forming surface.

The hole forming surface of the multilayer printed board is usually rectangular or square. However, if the length of the discharge point in the longitudinal direction of the first electrode is longer than the length of one side of the hole forming surface, one side of the hole forming surface. By arranging the electrode and the longitudinal direction of the first electrode in parallel, it is possible to perform the processing at one time up to the end of the hole forming surface. However, when one side of the hole forming surface and the longitudinal direction of the first electrode cannot be arranged in parallel (that is, when the longitudinal direction of the first electrode is inclined with respect to one side of the hole forming surface). In some cases, a portion where discharge treatment is not performed may occur at the end of the hole forming surface. Therefore, if the length of the discharge point in the longitudinal direction of the first electrode is equal to or greater than the length of the diagonal line of the hole forming surface as in these inventions, the first electrode is exactly parallel to one side of the hole forming surface. , It is possible to perform the processing all the way to the end of the hole forming surface.

In the method for treating a surface of a multilayer printed circuit board, it is preferable that the dielectric is coated on at least a portion of the first electrode facing the hole forming surface.

In the apparatus for treating a surface of a multilayer printed circuit board, it is preferable that the dielectric is coated on at least a portion of the first electrode facing the hole forming surface.

As in these inventions, if an integrated structure is used in which the dielectric is covered with the first electrode, the first electrode and the dielectric can be easily arranged and moved.

In the method of treating a surface of a multilayer printed circuit board, it is preferable that in the discharging step, corona discharge is generated while the first electrode and the hole forming surface are relatively moved.

It is preferable that the apparatus for treating a surface of a multilayer printed circuit board further includes a moving means for moving the first electrode and the hole forming surface relatively to each other.

By moving the first electrode and the hole forming surface relatively to each other as in these inventions, even when a linear electrode is used as the first electrode, the entire hole forming surface can be treated. And the processing time can be reduced.

It is preferable that the method for treating a surface of a multilayer printed circuit board further includes a punching step of forming a hole for a via hole by irradiating a laser beam.

It is preferable that the apparatus for treating a surface of a multilayer printed circuit board further includes a laser oscillating means for oscillating a laser beam for forming a via hole.

By forming a via hole using laser light (more preferably, infrared laser light) as in these inventions, it is advantageous in terms of drilling speed, running cost, and the like. In particular, the laser beam emitted by the carbon dioxide gas laser has a property that it is easily reflected by copper, so that perforation can be stopped by a conductive layer made of copper foil, which is suitable for forming a via hole.

[0029] The surface treatment method for a multilayer printed circuit board preferably further comprises a wet treatment step of subjecting at least the hole forming surface to a wet treatment, and a plating treatment for covering the inner surface of the via hole with conductive plating. It is also preferable to further include a step.

It is preferable that the apparatus for treating a surface of a multilayer printed circuit board further comprises a wet treatment means for performing a wet treatment on at least a surface on which holes are formed. It is also preferable to further include plating means for coating the inner surface of the via hole with conductive plating.

According to these inventions, it is possible to quickly perform the wet treatment or the plating treatment before the effect of hydrophilizing the hole forming surface by corona discharge is reduced. In addition, since the process of forming a via hole in a multilayer printed circuit board can be completed only by the present method and the present apparatus, other processing devices and transport operations are not required, and rapid formation of a via hole can be realized.

[0032]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of a surface treatment method and a surface treatment apparatus for a multilayer printed board according to the present invention will be described in detail. In the description of the drawings, the same or corresponding elements will be denoted by the same reference characters, without redundant description.

FIG. 1 is a flowchart illustrating a method for treating the surface of a multilayer printed circuit board according to the present embodiment. As shown in the figure, the surface treatment method for a multilayer printed circuit board according to the present embodiment can be roughly divided into four steps. Hereinafter, the apparatus used in each step and the processing in each step will be described in detail.

First, the first step of forming a via hole in a multilayer printed circuit board will be described. FIG. 2 shows the first
It is a perspective view explaining processing in a process. As shown in the figure, in the first step, a laser oscillation unit 11, galvanometer mirrors 15 and 16, and an f-θ lens 17 are used. Here, the laser oscillating unit 11 is provided with a carbon dioxide gas (C
O ₂ ) a laser oscillator 12 and a transfer optical system 14 including a collimator lens 13 and the like. Further, the galvanometer mirrors 15 and 16 are installed so as to be rotatable about the y-axis and the x-axis in FIG.
Is installed below the galvanometer mirror 16.

In the first step, the insulating layer 101 and the conductive layer 10
2 and a multilayer printed circuit board 100 composed of a laminated body in which insulating layers 103 are alternately laminated.
After being disposed below the −θ lens 17, the laser irradiation position is adjusted by the galvanometer mirrors 15 and 16, and the laser light is oscillated from the laser oscillation unit 22. This laser light is reflected by the galvanometer mirrors 15 and 16, and then condensed by the f-θ lens 17.
Irradiation is performed at a predetermined via hole formation location of 00. Also,
When a plurality of via holes are formed, the laser irradiation position is adjusted by the galvanomirrors 15 and 16 each time, and the laser light is repeatedly irradiated. This allows
A hole 104 for a via hole reaching the conductive layer 102 is formed on the hole forming surface of the substrate 100.

In the first step, the substrate 1 is
The via hole 104 formed at 00 has a partial conical shape whose bottom diameter is slightly smaller than its top diameter, as shown in FIG. Further, the insulating layer 101 is provided at the bottom of the hole 104.
Smear 105 consisting of the residue of the constituent material of
Even if the hole 104 is coated with conductive plating in this state, conduction between the plating layer and the conductive layer 102 cannot be established, so that the smear 105 is removed in the following second and third steps.

Next, a second step of performing corona discharge on the hole forming surface is described.
The steps will be described. FIG. 4 is a cross-sectional view for explaining the processing in the second step, and FIG. 5 is a cross-sectional view along II of FIG. As shown in these figures, in this second step,
An interval a (0.1 mm to 9 mm) is provided above the hole forming surface of the substrate 100.
mm, more preferably 0.3 mm to 5 mm). The first electrode 22 is an electrode made of a metal rod or pipe, and has a dielectric 2 around it.
3 are coated. Here, it is preferable that the length of the first electrode 22 be equal to or longer than the length of the short side of the substrate 100, since the processing can be performed on the plurality of holes 104 formed one-dimensionally in the substrate 100 at one time. The length of the first electrode 22 is
It is more preferable that the length be equal to or greater than the length of the diagonal line of 0 because one side of the substrate 100 and the longitudinal direction of the first electrode 22 can be processed all at once up to the end of the substrate 100 without having to be arranged exactly in parallel. . In addition, the dielectric 2 coated on the first electrode 22
Glass, ceramics or rubber is used for 3 and the thickness is 0.2 to 5 mm (preferably 0.5 to 2.5 mm)
It is said. Further, moving means (not shown) for moving the substrate 100 in a direction orthogonal to the longitudinal direction of the first electrode 22 is provided.

A second electrode 24 made of a metal plate having a larger area than the substrate 100 is arranged on the opposite side of the substrate 100 from the hole forming surface. The second electrode 24 may or may not be grounded. Further, the first electrode 22 and the second electrode 24 are connected via an RF circuit 21 by an external circuit. The high-frequency power supply 21 includes a first electrode 22
In addition, an AC voltage of 4 kV to 20 kV can be applied to the second electrode 24 at a high frequency of 5 kHz to 500 kHz.

In this second step, when a voltage is applied to the first electrode 22 and the second electrode 24 by the high frequency power supply 21, the electric field between the electrodes increases, and when the electric field reaches a certain critical value, corona discharge occurs. Occurs. At this time, the first electrode 22
Is concentrated on the conductive layer 102 exposed in the hole 104. Thereby, the smear 105 remaining at the bottom of the hole 104 can be removed by decomposition or evaporation. Further, a part of the discharge generated from the first electrode 22 is applied to the hole forming surface of the substrate 100. Thereby, the pore forming surface can be rapidly hydrophilized. By performing such a corona discharge process while moving the substrate 100 in a direction orthogonal to the longitudinal direction of the first electrode 22 by a moving means (not shown), the smear 1 remaining at the bottom of all the holes 104 is obtained.
05 can be removed, and the entire hole forming surface can be made hydrophilic.

Here, the superiority of the corona discharge treatment in the second step is based on the conventional treatment technique using plasma discharge (hereinafter referred to as Conventional Example 1) and the conventional treatment technique using corona discharge using needle-like electrodes ( Hereinafter, Conventional Example 2), a conventional processing technique using corona discharge with a linear electrode (hereinafter, Conventional Example 3).
This will be specifically described in comparison with.

FIG. 6 is a sectional view for explaining the processing technique in the first conventional example. As shown in FIG. 1, in the conventional example 1, the electrodes 32 and 33 are arranged to face each other with the substrate 100 interposed therebetween, and each electrode is connected to the high frequency power supply 3 by an external circuit.
The high-frequency power supply 31 applies a voltage to each electrode to generate a plasma discharge between the electrodes, thereby irradiating the plasma on the hole forming surface of the substrate 100.

However, the conventional example 1 has the following problems. The first problem is that the removal target is 10
The point is that only organic matter of about 0 ° is present. Therefore, it takes a long time to remove the thicker organic layer, and when a thick smear layer remains in the hole 104, the smear cannot be quickly removed. In addition, since the inorganic substance cannot be removed, the conductive layer 1 generated at the time of the perforation processing is removed.
02 was not able to be removed. On the other hand, in the corona discharge treatment in the second step of the present embodiment, the holes 10
In the case where a thick smear layer remains on the substrate 4, smear can be quickly removed, and burrs of the conductive layer 102 generated during the perforation process (first step) can also be removed.

The second problem of the first conventional example is that plasma does not easily enter the inside of the hole 104. That is, FIG.
As shown in (1), since the plasma reaches only the hole forming surface, it is difficult to remove the smear inside, particularly when the hole 104 has a small diameter. As shown in FIG. 8, in order for plasma to reach the bottom surface of the hole 104, the plasma intensity must be increased more than necessary. However, if the plasma intensity is increased more than necessary, the hole indicated by the broken line in FIG. In some cases, the formed surface was shaved and the surface became rough as shown by the solid line in FIG. On the other hand, in the corona discharge treatment in the second step of the present embodiment, the discharge generated from the first electrode 22 is:
Due to its discharge characteristics, as shown by the arrow in FIG.
Even if 4 has a small diameter, it can penetrate inside.

The third problem of the conventional example 1 is that the processing requires cost and labor. That is, in Conventional Example 1, M
A large-sized apparatus such as a high-frequency power supply for applying a high-frequency voltage on the order of Hz and a pressure-controllable chamber is required, and a supply of a plasma gas such as oxygen, helium, or argon is required as a plasma source. In addition, an operation for reducing the pressure in the chamber and an adjustment operation for stabilizing the plasma are required, and the processing time is long.
On the other hand, the high-frequency power supply 21 used for the corona discharge treatment in the second step of the present embodiment may be of the order of kHz, and can perform discharge in air under atmospheric pressure, so that special equipment and work are not required, and Processing can be performed.

FIG. 11 is a sectional view for explaining a processing technique in the second conventional example. As shown in FIG.
In the embodiment, the needle-shaped electrode 42 is arranged on the hole forming surface side of the substrate 100, the counter electrode 43 is arranged on the opposite surface side of the hole forming surface, and each electrode is connected by an external circuit via the high frequency power supply 41. I have. In this conventional example 2, the needle electrode 4
After the electrodes 2 are arranged in the vicinity of the holes 104, a voltage is applied to each electrode by the high frequency power supply 41 to generate corona discharge between the electrodes, and the discharge is applied to the hole forming surface of the substrate 100.

However, in the conventional example 2, the substrate 1
In addition to accurately grasping the position of the hole 104 formed in the hole 00, it is necessary to accurately arrange the needle electrode 42 in the vicinity of the hole 104. Therefore, a separate means for accurately positioning the needle electrode 42 is required, and it has been difficult to accurately position the needle electrode 42, particularly when the hole 104 has a small diameter. In addition, when a large number of holes are irregularly arranged, it is necessary to repeat the positioning of the needle-shaped electrodes 42, which increases the labor and the processing time.

In the third conventional example, corona discharge is applied to the hole forming surface of the substrate 100 using the linear electrodes 51 as shown in FIG. In the third conventional example, since the linear electrodes 51 are used instead of the needle electrodes, the difficulty of alignment is reduced. However, the corona discharge is performed with the linear electrodes 51 exposed in this manner. When it is generated, the discharge is likely to be unstable, and current concentration may occur at one location, causing a transition to arc discharge, and a larger current than necessary may flow. Therefore, the insulating layer 101 at the position indicated by the broken line in FIG. 12 is damaged, and the hole 104 is formed as shown by the solid line in FIG.
Was sometimes spread out.

On the other hand, the electrode 22 used in the second step of this embodiment is covered with a dielectric 23. This dielectric material 23 is a small capacitor 25 as shown in FIG.
a, 25b,..., 25n, and serves to prevent the discharge from being concentrated at a specific position. That is, if a certain minute capacitor is charged in a half cycle of the applied high-frequency voltage, the current stops flowing at the position of the minute capacitor, the current flows at the position of another minute capacitor, and the minute capacitor is charged. In this case, the current flowing position changes sequentially, for example, the current flows at the position of another minute capacitor. In the next half cycle, the minute capacitor is charged in the reverse direction, and the position where the reverse current flows changes sequentially. That is, a current I as shown in FIG. 14 flows every half cycle of the high frequency voltage V. Thus, in the second step of the present embodiment, the third conventional example is used.
And the transition to arc discharge can be suppressed, and there is no risk of damaging the insulating layer 101 and the like.

As described above, in the corona discharge treatment in the second step of the present embodiment, the problems in Conventional Examples 1, 2, and 3 can be solved, and a quick and effective surface treatment can be performed.

Here, an experimental example showing the effect of hydrophilization by corona discharge treatment in the second step of this embodiment will be described. In this experimental example, the area of the substrate 100 was set to 150 mm
A hole 104 having an upper diameter of 120 μm with an insulating layer (epoxy resin) 101 having a thickness of 80 μm, a conductive layer (copper) 102 having a thickness of 50 μm, and a thickness of 1 mm.
Formed at intervals of 1 mm. The AC voltage output of the high frequency power supply 21 is 10 kV, and the frequency is 20 kHz.
As the first electrode 22, a stainless steel round bar having a diameter of 5 mm coated with a dielectric material 23 made of silicon rubber having a thickness of 1.5 mm was used and arranged so that the discharge interval a was 1 mm. Under these conditions, a corona discharge generated from the first electrode 22 is applied to the hole forming surface (epoxy resin layer surface) of the substrate 100, and the irradiation time and the contact angle of water at the discharge irradiation site of the hole forming surface are determined. When the relationship was measured, a measurement result as shown by a solid line in FIG. 15 was obtained. Example of irradiating the hole forming surface with ultraviolet rays instead of corona discharge (see broken line in the figure)
As is apparent from comparison with the above, it can be understood that the pore-forming surface can be rapidly and hydrophilically (approximately 1 to 2 seconds) by irradiation with corona discharge. In addition, when the same measurement was performed on the surface of the conductive layer (copper layer), as shown in the figure, it was found that the surface could be hydrophilized very quickly as in the case of the surface of the epoxy resin layer. Further, although not shown, it has been measured that when plasma is applied to the surface on which holes are formed, it takes about several minutes for hydrophilization. It is confirmed that the surface can be rapidly hydrophilized.

When the conductive layer 102 is made of copper, if the corona discharge treatment time is long, copper is oxidized.
It is preferable to keep it for about 5 seconds. As described above, when the corona discharge treatment is performed on the entire hole forming surface by moving the substrate 100 in a direction orthogonal to the longitudinal direction of the first electrode 22, the discharge processing time is changed by changing the moving speed of the substrate 100. Can be adjusted, and oxidation of the conductive layer 102 can be prevented. For example, when the first electrode 22 is a round bar having a diameter of 5 mm, the moving speed of the substrate 100 is 10 mm.
mm / sec.

Next, the third step of performing a wet treatment on the hole forming surface will be described. FIG. 16 is a cross-sectional view illustrating a process in the third step. As shown in the figure, in this third step, a desmear solution 6 such as a potassium permanganate solution is used.
The substrate 100 is immersed in the processing tank 61 containing the substrate 2, and the hole forming surface is wet-processed. Generally, the diameter of the hole 104 is 100 μm.
m or less, it is difficult for the liquid to enter the inside of the hole 104 due to surface tension, but due to the effect of the corona discharge irradiation in the second step, the desmear solution 62 can smoothly enter the inside of the hole 104, This makes it possible to remove the smear 105 that could not be removed in the second step.

In the third step, in addition to the desmear processing described above, other wet processing is performed as necessary. For example, if the exposed portion of the conductive layer 102 in the hole 104 is covered with an oxide film, a conduction failure may be caused. Therefore, a process of removing the oxide film with a reducing agent solution or the like is performed. Further, in order to roughen the inner surface of the hole 104 to improve plating, a blackening process using a processing solution containing a catalyst or the like is performed. Even in such other wet processing, the respective solutions can smoothly penetrate into the holes 104 by the effect of the corona discharge irradiation in the second step.

Finally, the fourth step of coating the inside of the hole with plating will be described. FIG. 17 is a cross-sectional view illustrating a process in the fourth step. As shown in FIG.
In the process, the hole forming surface and the inner surface of the hole 104 are coated with the electroless copper plating 71. This plating coating treatment is performed by immersing the substrate in a bath containing a plating solution as in the third step. Here, however, the plating solution is smoothly introduced into the hole 104 by the effect of the corona discharge irradiation in the second step. Can be infiltrated. By such plating treatment, a via hole is formed in the hole 104, and a three-dimensional electric circuit is formed on the substrate 100.

As described above, according to the present embodiment, compared with the above-described Conventional Example 1, Conventional Example 2, and Conventional Example 3,
Quick and effective surface treatment can be performed. That is, it is possible to prevent discharge concentration at a specific position, suppress transition to arc discharge, and remove smear inside the via hole for the hole without damaging the hole forming surface and the like.
In addition, by making the hole forming surface hydrophilic by corona discharge, a wet process, a plating process, and the like can be easily performed even on a small-diameter hole. Therefore, the first to fourth steps of the present embodiment can form a via hole having sufficient electrical continuity.

The method and apparatus for treating the surface of a multilayer printed board according to the present invention are not limited to those described in the above embodiments, but may take various modifications in accordance with other conditions. It is possible. For example, in the second step of the above embodiment, it is not necessary to dispose the second electrode 24 in contact with the substrate 100, and a separate dielectric member is disposed between the substrate 100 and the second electrode 24. Is also good.

In the second step of the above embodiment, the first step
Although an example in which a linear electrode is used as the electrode 22 has been described, a grid electrode in which discharge points are formed in a grid shape (mesh shape) or a planar electrode similar to the second electrode 24 is used as the first electrode 22. It is also preferable to use them. If such a grid electrode or a planar electrode is used, processing can be performed on the entire hole forming surface at once, and the processing time can be reduced. Further, it is also preferable to use a plurality of electrodes as the first electrode 22. By using a plurality of electrodes as described above, processing can be performed on many holes at once, and the processing time can be reduced.

In the second step of the above embodiment, the first step
Although an example in which the dielectric 23 is coated on the entire surface of the electrode 22 has been described, the present invention is not limited to this, and the dielectric may be disposed between the first electrode 22 and the substrate 100. For example, only the lower side of the first electrode 22 in FIGS. 4 and 5 may be covered with a dielectric, or FIG.
As shown in FIG. 3, the independent dielectric member 26 is connected to the first electrode 22.
Below.

In the second step of the above-described embodiment, an example has been described in which the substrate 100 is moved in a direction perpendicular to the longitudinal direction of the first electrode 22 to perform processing on the entire surface on which the holes are formed. First instead of moving
The processing may be performed on the entire hole forming surface by moving the electrode 22.

[0060]

According to the method and apparatus for treating the surface of a multilayer printed circuit board according to the present invention, it is possible to solve the problems of the conventional processing techniques and to carry out a quick and effective surface treatment. .

That is, by disposing a dielectric between the hole forming surface and the first electrode, the dielectric functions as an aggregate of minute capacitors, and prevents the discharge from being concentrated at a specific position. Fulfill. Therefore, it is possible to suppress the transition to the arc discharge as in the conventional processing technique using corona discharge by the linear electrode, and to remove the smear inside the via hole without damaging the hole forming surface and the like. It becomes possible. In addition, since the hole forming surface can be made hydrophilic by corona discharge, it is possible to easily perform wet processing, plating processing, and the like even for small-diameter holes, and thus, a via hole having sufficient electrical continuity. Can be formed.

Further, if the first electrode has a structure in which discharge points are continuous in a linear, lattice or plane shape, there is a problem of difficulty in alignment as in the above-mentioned prior art using corona discharge by needle electrodes. Does not occur. Further, by forming the first electrode in a configuration in which the discharge points are continuous in a grid or plane, surface treatment can be performed on the entire hole forming surface at one time, and the processing time can be reduced. Become.

Further, if the first electrode is composed of a plurality of electrode members, a large number of holes can be processed at one time, and the processing time can be reduced.

Further, if the length of the discharge point in the longitudinal direction of the first electrode is set to be equal to or greater than the length of the diagonal line of the hole forming surface, the first electrode will not be arranged exactly parallel to one side of the hole forming surface. Even in this case, it is possible to perform the processing at one time up to the end of the hole forming surface.

Further, if the dielectric has an integral structure covered with the first electrode, the first electrode and the dielectric can be easily arranged and moved.

Further, by moving the first electrode and the hole forming surface relative to each other, even when, for example, a linear electrode is used as the first electrode, the entire hole forming surface can be treated. In addition, the processing time can be reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a surface treatment method for a multilayer printed circuit board according to an embodiment.

FIG. 2 is a perspective view illustrating a process in a first step.

FIG. 3 is a perspective view showing a hole for a via hole formed in a first step.

FIG. 4 is a cross-sectional view illustrating a process in a second step.

FIG. 5 is a sectional view taken along the line II of FIG. 4;

FIG. 6 is a cross-sectional view illustrating a processing technique in Conventional Example 1.

FIG. 7 is a cross-sectional view illustrating a processing technique in Conventional Example 1.

FIG. 8 is a cross-sectional view illustrating a processing technique in Conventional Example 1.

FIG. 9 is a cross-sectional view illustrating a processing technique in Conventional Example 1.

FIG. 10 is a cross-sectional view illustrating a process in a second step.

FIG. 11 is a cross-sectional view illustrating a processing technique in Conventional Example 2.

FIG. 12 is a cross-sectional view illustrating a processing technique in Conventional Example 3.

FIG. 13 is a perspective view illustrating a process in a second step.

FIG. 14 is a graph illustrating a process in a second step.

FIG. 15 is a graph showing the effect of hydrophilization by the treatment in the second step.

FIG. 16 is a cross-sectional view illustrating a process in a third step.

FIG. 17 is a cross-sectional view illustrating a process in a fourth step.

FIG. 18 is a perspective view illustrating a modification of the present embodiment.

[Explanation of symbols]

11 laser oscillator, 12 laser oscillator, 13 collimating lens, 14 transfer optical system, 15 galvanomirror, 16 galvanomirror, 17 f-θ lens, 21
... High frequency power supply, 22 ... First electrode, 23 ... Dielectric, 24 ...
2nd electrode, 25 ... minute capacitor, 26 ... dielectric member,
31: High frequency power supply, 32: Electrode, 33: Electrode, 41: High frequency power supply, 42: Needle electrode, 43: Counter electrode, 51: Linear electrode, 61: Processing tank, 62: Desmear solution, 71: Electroless copper Plating, 100: multilayer printed circuit board, 101: insulating layer, 102: conductive layer, 103: insulating layer, 104: hole,
105 ... Smear

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 3/26 H05K 3/26 B (72) Inventor Tomonori Oya 1126-1, Nomachi, Ichinomachi, Hamamatsu-shi, Hamamatsu Shizuoka F term (reference) in Photonics Co., Ltd.

Claims (18)

[Claims] 1. A method for performing a surface treatment on a multilayer printed circuit board comprising a laminate in which conductive layers and insulating layers are alternately laminated, wherein a hole forming surface having a via hole reaching the conductive layer is formed. A first electrode is disposed at a position facing the first electrode, and a first dielectric is disposed between the hole forming surface and the first electrode.
An arranging step, a second arranging step of arranging a second electrode at a position facing the first electrode with the multilayer printed board interposed therebetween, and applying a voltage between the first electrode and the second electrode. A discharge process for generating a corona discharge between the first electrode and the conductive layer. 2. The multilayer printed circuit board according to claim 1, wherein, in the first disposing step, an electrode having a continuous discharge point in a linear, lattice, or planar shape is disposed as the first electrode. Surface treatment method. 3. The method according to claim 1, wherein in the first arranging step, a plurality of electrode members are arranged as the first electrodes. 4. The method according to claim 1, wherein in the first arranging step, an electrode having a length of a discharge point in a longitudinal direction that is equal to or greater than a length of a diagonal line of the hole forming surface is arranged as the first electrode. The surface treatment method for a multilayer printed board according to any one of claims 1 to 3. 5. The surface treatment of a multilayer printed circuit board according to claim 1, wherein the dielectric is coated on at least a portion of the first electrode facing the hole forming surface. Method. 6. The corona discharge according to claim 1, wherein in the discharging step, the corona discharge is generated while moving the first electrode and the hole forming surface relatively to each other. Surface treatment method for multilayer printed circuit boards. 7. The method according to claim 1, further comprising the step of forming a hole for the via hole by irradiating a laser beam. 8. The surface treatment method for a multilayer printed circuit board according to claim 1, further comprising a wet treatment step of subjecting at least the hole forming surface to a wet treatment. 9. The surface treatment method for a multilayer printed circuit board according to claim 1, further comprising a plating step of coating an inner surface of the via hole with conductive plating. 10. An apparatus for performing a surface treatment of a multilayer printed circuit board comprising a laminate in which conductive layers and insulating layers are alternately laminated, wherein a hole forming surface in which holes for via holes reaching the conductive layer are formed. A first electrode disposed at a position facing the first electrode, a dielectric disposed between the hole forming surface and the first electrode, and a dielectric disposed at a position facing the first electrode with the multilayer printed circuit board interposed therebetween. And a voltage applying unit that applies a voltage for generating a corona discharge between the first electrode and the conductive layer between the first electrode and the second electrode. An apparatus for treating a surface of a multilayer printed circuit board. 11. The apparatus for treating a surface of a multilayer printed circuit board according to claim 10, wherein the first electrode is an electrode having a continuous discharge point in a linear, lattice, or planar shape. 12. The apparatus according to claim 10, wherein the first electrode comprises a plurality of electrode members. 13. The multilayer print according to claim 10, wherein the first electrode has a length of a discharge point in a longitudinal direction equal to or greater than a length of a diagonal line of the hole forming surface. Substrate surface treatment equipment. 14. The surface treatment of a multilayer printed circuit board according to claim 10, wherein the dielectric is coated on at least a portion of the first electrode facing the hole forming surface. apparatus. 15. The apparatus for treating a surface of a multilayer printed circuit board according to claim 10, further comprising moving means for moving the first electrode and the hole forming surface relatively to each other. . 16. The apparatus for treating a surface of a multilayer printed circuit board according to claim 10, further comprising a laser oscillating means for oscillating a laser beam for forming the via hole. 17. The apparatus for treating a surface of a multilayer printed circuit board according to claim 10, further comprising a wet treatment means for performing a wet treatment on at least the hole forming surface. 18. The apparatus for treating a surface of a multilayer printed circuit board according to claim 10, further comprising plating means for coating an inner surface of said via hole with conductive plating.