JPH10126038A - Printed wiring board and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an exposing process and developing process using a photomask omittable after a resist is formed by roughening the surface of a metallic layer on a wiring circuit forming surface side so that a prescribed roughness can be obtained non-directionally and jetting photo-setting ink upon a roughened circuit forming section from an ink jet head. SOLUTION: The surface of a metallic layer 11 is roughened by non- directionally forming recessed and projecting sections by spraying particles with a sandblaster 16 from the direction perpendicular to the surface in a roughening process. After the surface is roughened, photo-setting ink is jetted upon the roughened surface from an ink jet head 17 in accordance with a set pattern. Consequently, the cured photo-curing ink composition 13B corresponding to a circuit forming section 13a is formed on the surface of the roughened metal layer 11. Thereafter, a conductive circuit 11A can be formed on an insulating layer 12 through an etching process. The sandblast in the roughening process is performed by using, for example, fused alumina particles having a particle size of #220.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board and a method of manufacturing the same, and more particularly, to a printed wiring board formed by forming a figure using a printing technique and leaving a wiring circuit by etching, and a method of manufacturing the same. About.

[0002]

2. Description of the Related Art A conventional general printed circuit board manufacturing method will be described with reference to FIG.

In FIG. 3A, reference numeral 11 denotes an insulating layer 12.
It is a metal layer laminated thereon. The insulating layer 12 is formed mainly of glass or epoxy resin called glass epoxy, for example, and serves as a base (resin layer). The metal layer 11 made of a conductive metal such as copper is laminated thereon and printed. It is prepared as a wiring substrate 21. (B) shown below is a surface conditioning process in which a resist layer 13 that is sensitive to UV light (ultraviolet light) is formed on the metal layer 11 in the process shown in (C). Prior to that, resist layer 1
3 is performed for the purpose of improving the adhesion to the metal layer 11. Note that a method such as buff polishing has been generally used for such surface conditioning treatment.

[0004] By such buff polishing, the surface roughness of the metal layer 11 is made slightly rougher than before polishing. Thus, in the step (C), the adhesion of the resist layer 13 to the metal layer 11 is enhanced. Next, (D) shows an exposure state in an exposure process, where 14 is a photomask, 14A is a light transmitting window provided in the photomask 14, and 14B is ultraviolet light. Thus, the light transmitting window 14 is formed by the exposing process (D).
The exposed portion (hereinafter, referred to as a circuit forming portion) 13A of the resist layer 13 exposed through A changes in composition, and the circuit forming portion 13A becomes insoluble in a developing process (E) described below and becomes insoluble on the metal layer 11. Remains. The light transmitting window 14A is made of the metal layer 11.
It is formed in accordance with a circuit pattern formed on demand. The above-described process is known as a photolithography technique, and the actual operation is different depending on whether it is a positive type or a negative type. However, the above is only a basic example. In forming the resist layer 13, a dry film type material may be used instead of a liquid resist forming material.

After the unexposed portion of the photoresist layer 13 is dissolved and removed with a developing solution in the developing process shown in FIG. 1E, the metal is chemically etched in the etching process shown in FIG. Circuit forming unit 13 using chemical
By dissolving and removing the circuit forming portion 13A of the resist layer 13 together with the metal layer exposed portion 11B not covered with A, the conductive circuit 11A can be formed in the portion of the metal layer 11 covered by the circuit forming portion 13A. Therefore, in the subsequent process (G), a solder resist (a protective insulating layer of solder) 15 is formed around the conductive circuit 11A on the insulating layer 12, and a desired printed wiring board 20 is obtained. In addition,
If necessary, in addition to the process of (G), the conductive circuit 11A
Silver plating may be applied on the top (not shown).

[0006]

In the above-mentioned conventional method for manufacturing a printed wiring board, a photosensitive resist layer is formed once and then exposed using a photomask to form a resist layer on a metal layer into a wiring circuit. A process of forming a corresponding circuit forming portion is required, and the manufacturing cost of the printed wiring board is correspondingly high.

Therefore, the inventors of the present invention have shown in FIG. 3B that an ink jet recording apparatus has been used to form a photosensitive layer having ultraviolet light sensitivity on the metal layer 11 on which the surface of the laminated substrate 21 has been adjusted. A manufacturing method has been proposed in which the ink having a certain composition portion is directly discharged, and the ink discharge is performed according to a desired pattern, whereby the steps (C), (D) and (E) can be omitted. According to the proposals of the present inventors, thereafter, it is only necessary to carry out the processes shown in FIGS. 3 (F) and 3 (G), thereby reducing the manufacturing time and the cost of the printed wiring board by simplifying the manufacturing equipment. Can contribute to

[0008] However, the method of manufacturing a printed wiring board according to the above proposal can contribute to cost reduction of the printed wiring board, but has a problem in performing the same leveling treatment on the surface of the metal layer as before.

That is, when the above-described ink (hereinafter, referred to as a UV-curable ink) is landed on the surface of a conventional metal layer having a flat surface, the landed UV-curable ink droplets are fine, but the impact amount at the time of landing is small. It has a tendency to spread to some extent. However, on the surface of the metal layer that has been surface-formed, fine streaks and irregularities formed when the surface is ground in the surface-setting process by, for example, buff polishing, remain. Tend to be formed along. Therefore, the pattern formed on the metal layer 11 by the UV curable ink droplets is an aggregate of pixels 30B having a shape as shown in FIG. 2B, and therefore, especially when a high-density pattern is to be drawn. In some cases, adjacent circuit patterns may be joined to each other, or conversely, the pixels 30B may be separated from each other regardless of the need for continuity. In such a case, a short circuit or a short circuit may occur in the finished pattern. Disconnection may occur, leading to a reduction in manufacturing yield.

An object of the present invention is to pay attention to the above-mentioned problems, and it is possible to omit a process of exposing and developing using a photomask after forming a resist layer as in the related art, It is an object of the present invention to provide and propose a printed wiring board capable of forming a wiring circuit following an accurate circuit pattern and a method of manufacturing the same.

[0011]

In order to achieve the above object, the present invention is directed to a method for forming a circuit forming portion of a metal layer on a substrate having a metal layer for forming a wiring circuit formed on an insulating layer. In a method for manufacturing a printed wiring board, wherein the wiring circuit is obtained on the insulating layer by etching after coating with a photocurable composition, a roughening means such that a predetermined roughness is obtained in a non-directional manner. Roughening the surface of the metal layer on the wiring circuit forming side, and discharging the photocurable composition as ink from the inkjet head to the circuit forming portion on the roughened wiring circuit forming surface. It is characterized by the following.

According to the present invention, the surface of the metal layer on which the wiring circuit is formed is roughened in a non-directional manner so as to obtain a predetermined roughness. Since a circuit capable of forming a photo-curable composition is ejected from the head to cover the circuit forming portion, a process of forming a photoresist layer, exposing and developing as in the related art can be omitted. The surface corresponding to the wiring circuit is covered with fine, almost circular dots without fear of non-contact and short circuit on the surface of the wiring circuit, and a metal layer is formed on the surface by etching. A fine wiring circuit can be formed.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a process of manufacturing a printed wiring board according to the present invention. FIG. 1A shows the configuration of a substrate 21 prepared in advance similarly to that described with reference to FIG.
Here, the insulating layer 12 is not limited to the glass epoxy, but may be of any form as long as the metal layer 11 such as copper is laminated on one or both sides thereof. FIG. 1B shows a step of leveling the surface of the metal layer 11. As described above, the conventional method using buffing or the like forms fine stripes formed on the surface in almost the same direction. The scar was a problem.

In the present invention, attention is paid to this point, and fine irregularities without directivity are obtained in this step. Therefore, in the case of this embodiment, random fine irregularities having no directivity are obtained by sandblasting. This process is called a roughening process in order to distinguish it from the conventional surface smoothing. Thus, in the surface roughening process shown in FIG. 1B, particles are sprayed from a direction perpendicular to the surface by sandblasting 16 as shown by the arrow direction to roughen the surface of the metal layer 11 by forming irregularities having no direction. In the next step (C), the UV curable ink is ejected from the inkjet head 17 according to the set pattern. Here, 13B is a UV ink curing composition formed on the surface of the roughened metal layer 11, and the curing composition 13B corresponds to the circuit forming portion 13A shown in FIG. .

After this, the etching process (FIG. 3)
1D), the conductive circuit 11A can be formed on the insulating layer 12 as shown in FIG. The pixel 30A forming the conductive circuit 11A in this case was formed in a substantially circular shape as shown in FIG. Therefore, the current does not flow in a streak like the pixel (see FIG. 2B) 30B formed on the surface of the metal layer 11 that has been flattened so far. Disconnection can be prevented.
In the case of this example, when discharging the UV curable ink, 360
The recording was performed using a recording head having 64 ejection openings at a dot / inch density. The ejection amount for forming the pixel 30A was about 80 ng, and the diameter of the obtained pixel 30A was about 100 μm per one.

Hereinafter, a specific example of roughening performed when a circuit pattern is formed by discharging the UV curable ink from the recording head and using the pixels 30A will be described.

[Embodiment 1] The surface roughening treatment of this embodiment was performed by blasting. Fused alumina was used as the blast material, and the particle size was # 220.

First, the substrate 21 was set on a stage movable in the horizontal plane direction, and the blasting direction of the blast material was set on the substrate in the upper vertical direction. The distance between the two is maintained at about 20 cm, and the injection nozzle diameter is about φ6.5 m
m, air pressure is about 2.0 kgf / cm ² . The movement was performed while moving the substrate on the stage until the roughness of the rope ground surface 11 was no longer changed.

As another spraying example, the surface was similarly roughened using a # 400 blast material. The former had a surface roughness of about 10 μm, but in this example was about 5 μm. Since the purpose of the present embodiment is to obtain a surface having no directivity, the surface may be roughened by using a blast having a finer grain size. However, if the blast material of # 46 is used on the side having a large particle size, for example, the pattern may be too large when performing patterning by inkjet in the blowing step, or the ink may be reduced to a desired size. However, there is a possibility that the pattern does not spread and the pattern becomes fine or short-circuit occurs.

Further, after processing with a blast material having several particle sizes, patterning with ink was performed, and the quality was visually checked. The results are shown in the table below.

In the table, the mark ○ indicates that the pattern uniformity was good and there were no problems such as short-circuits, and the mark × indicates that the size was irregular, that it seemed to be short, etc., and that it was not practical. It was done. The symbol "△" is intermediate.

As is apparent from the table, the particle size distribution is # 60.
It can be seen that a finer blast material has better patterning properties.

[0024]

[Table 1]

The recording head as described above is generally commercially available. In the above-described embodiment, an electric heat source for converting electric energy into heat energy is used as an energy source for discharging the UV curable ink. The test was performed using a recording head having a conversion element in each liquid path. on the other hand,
Obviously, the size of the obtained pixel also changes depending on the relationship between the roughness of the surface of the metal layer formed by sandblasting and the viscosity and surface tension of the UV curable ink. Therefore, it is of course necessary to select an appropriate particle size for sandblasting according to the physical properties of the UV curable ink used. In particular, if the surface roughness is unnecessarily large, diffusion on the surface of the UV-curable ink is inhibited, resulting in an irregular pixel shape, which is not preferable.
Rmax = 10 μm to Rmax = 0.1 μm in surface roughness
Good range.

The means for roughening the surface is not limited to the sandblasting used in the above-described embodiment, but may be, for example, liquid honing. Irregular irregularities can be formed on the surface of the metal layer by such liquid honing. Furthermore, it is also possible to use a chemical etching method. In short, any roughening means can be used as long as it is a means capable of forming fine and non-directional irregularities on the metal surface.

[0027]

As described above, according to the method of manufacturing a printed wiring board according to the present invention, the wiring circuit of the metal layer is formed by the surface roughening means for obtaining a predetermined roughness in a non-directional manner. The surface on the side is roughened, and the photocurable composition is ejected as ink from the inkjet head to the circuit forming portion on the roughened wiring circuit forming surface, so that the process is simplified. As a result, the working time can be shortened, and a circuit pattern having a fine density can be formed on the substrate without causing discontinuous portions in the circuit or short-circuiting.

Further, the work time can be shortened, and the exposure process and the development process using a photomask can be omitted, which contributes to a reduction in the cost of a printed wiring board. Can be achieved.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a method of manufacturing a printed wiring board according to the present invention in the order of steps (A) to (D).

FIGS. 2A and 2B are schematic diagrams showing that pixels obtained by discharging UV curable ink for forming a circuit on a substrate are different due to a difference in metal surface flattening work, by a schematic comparison of FIGS. It is.

FIGS. 3A to 3C show a conventional method for manufacturing a printed wiring board.
It is explanatory drawing shown in process order of (G).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Metal layer 11A Conductive circuit 12 Resin layer 13 Resist layer 13A Exposure part (circuit formation part) 13B UV ink curing composition 14 Photomask 14A Translucent window 15 Solder resist 16 Sandblast 17 Inkjet head 20 Printed wiring board 21 Laminated substrate 30A, 30B pixels

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiromichi Noguchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroshi Sugitani 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside the corporation

Claims (10)

[Claims] 1. A circuit in which a circuit forming portion of a metal layer is coated with a photocurable composition on a substrate on which a metal layer for forming a wiring circuit is laminated on an insulating layer, and then the wiring circuit is etched by an etching process. In the method for manufacturing a printed wiring board to be obtained on the insulating layer, the surface of the metal layer on the wiring circuit forming side of the metal layer is roughened by a surface roughening means such that a predetermined roughness is obtained in a non-directional manner. A method for manufacturing a printed wiring board, characterized in that the photocurable composition is ejected as ink from an ink jet head to the circuit forming portion on the roughened wiring circuit forming surface. 2. The method for manufacturing a printed wiring board according to claim 1, wherein said predetermined roughness is obtained by sandblasting from a direction perpendicular to a wiring circuit forming surface of said metal layer. 3. The method according to claim 2, wherein the size of the spray particles used in the sandblasting is smaller than that of # 60. 4. The method according to claim 1, wherein the predetermined roughness is obtained by liquid honing from a direction perpendicular to a wiring circuit forming surface of the metal layer. 5. The predetermined roughness is such that Rmax is 20 μm.
The method for manufacturing a printed wiring board according to claim 1, wherein the range is as follows. 6. The method for manufacturing a printed wiring board according to claim 1, wherein the photocurable composition is cured by ultraviolet light. 7. The ink-jet head according to claim 1, wherein an element for generating energy for ejecting the ink containing the photocurable composition includes an electrothermal converter for converting electric energy to heat energy. Manufacturing method of printed wiring board. 8. The ink jet head has an ink ejection port provided at a density of 360 dots / inch,
The diameter of the photo-cured product formed on the wiring circuit forming surface by the ink droplets discharged from the ink discharge port is about 100 μm.
The method for manufacturing a printed wiring board according to claim 7, wherein 9. The method according to claim 1, wherein the metal layer is formed of copper. 10. A printed wiring board manufactured by the manufacturing method according to claim 1. Description: