JPH09246329A - Manufacture of circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the excellent bondability with small vertical difference of line widths of circuit patterns and smooth circuit surface by forming a metal circuit pattern by additive electroplating, and removing photosensitive resin and the conductive layer of a space part. SOLUTION: A resin coating pattern in which the space part is covered and the line part is exposed is formed. Simultaneously, a metal circuit pattern is formed on line part by additive electroplating. Then, after the upper surface of the circuit pattern is polished to be smoothed, photoesensitive resin and the conductive layer of the space part are removed. Thus, the irregularity in the line width of upper and lower circuit pattern is reduced irrespective of whether it is a transfer type or not, and a circuit board in which circuit surface is smooth and which has excellent bondability can be obtained. In the case of polishing the surface of the metal circuit, the resin performs the role of a protector, and hence the defect or release of the metal circuit can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a circuit board.

[0002]

2. Description of the Related Art Circuit patterns of various electronic materials such as TAB, FPC, and MCM-L used in color filters for liquid crystal displays are becoming finer in line width and finer in pitch of lines or spaces as IC chips become finer. It is progressing rapidly.

Incidentally, such TAB, FPC, MCM-L
A three-layer copper-polyimide film in which a copper foil is laminated with a polyimide film with an adhesive is widely used as a base material for the circuit, and its circuit is coated with a photosensitive resin (photoresist) and exposed. , Development, etching,
It is formed through various steps such as resin peeling.

[0004]

However, this method is
A photosensitive resin is coated on a polyimide film laminated with copper foil, and then a portion where a circuit is to be formed (hereinafter referred to as a line portion) is covered and a portion where a circuit is not formed (hereinafter a space portion). Is formed, and the copper foil in such a space portion is removed by etching. Therefore, during the etching, part of the line portion (space portion and A situation that adjacent portions) are simultaneously etched, that is, a situation generally called side etching occurs.

Therefore, the cross section of the formed circuit tends to have a shape similar to a trapezoid or a triangle. Therefore, when bumps are formed on the circuit or the circuit is connected with an anisotropic conductive resin such as ACF or ACA. However, there is a drawback in that a sufficient contact area cannot be obtained and a defective joint is likely to occur.

In that respect, another method, that is, applying a photosensitive resin on a metal plate and then covering the space portion,
And, forming a resin coating pattern exposing the line portion, on the line portion, to form a metal circuit pattern by additive electrolytic plating, then, after removing the photosensitive resin, the metal circuit pattern, the substrate The circuit board manufacturing method (hereinafter referred to as a transfer type) in which the transfer is performed by pressure bonding via an adhesive has a smaller vertical line width difference (line width variation) than the above-mentioned non-transfer type case. It has the advantage that the bonding area is relatively large, but on the other hand, the tip is rounded (formed into a rounded shape) and the thickness of the circuit surface varies due to the current density of plating. Since unevenness (height variation) occurs and overall smoothness is inferior, the reliability of joining with the IC chip is not sufficient, and when used as an FPC or MCM-L, it is for insulation. Adhesion to the polyimide film is not necessarily sufficient.

In view of such a drawback, the present invention has made earnest studies to solve the above-mentioned problems, and as a result, in the case of a non-transfer type, a resin coating pattern in which a space portion is covered and a line portion is exposed is provided. A metal circuit pattern is formed on the line portion by additive electrolytic plating, and further, the upper surface of the metal circuit pattern is polished and smoothed by a predetermined method prior to the removal of the resin. It has been found that a circuit board having excellent bondability can be obtained, in which the disadvantages of the conventional method such as a trapezoid or a shape similar to a triangle to obtain a sufficient contact area can be ignored, and even in the case of a transfer type. ,
It was found that a circuit board having excellent bondability can be obtained by polishing and smoothing the upper surface of the metal circuit pattern before removing the resin coating pattern.

[0008]

That is, one of the methods for manufacturing a circuit board according to the present invention is, as described in claim 1, that a photosensitive resin is applied onto a base material on which a conductive layer is formed. ,
Next, a resin coating pattern that covers the space portion and exposes the line portion is formed, and a metal circuit pattern is formed on the line portion by additive electrolytic plating, and then the upper surface of the metal circuit pattern is polished. After smoothing by smoothing, the photosensitive resin and the conductive layer in the space portion are removed.

Further, according to another method of manufacturing a circuit board according to the present invention, as described in claim 2, a photosensitive resin is applied onto a metal plate having a conductive layer formed thereon, and then a space is applied. Forming a resin coating pattern that covers the part and exposes the line part, forms a metal circuit pattern on the line part by additive electrolytic plating, and then polishes and smoothes the upper surface of the metal circuit pattern. After that, the photosensitive resin is removed, and further, the laminate of the conductive layer and the metal circuit pattern is transferred onto a base material, and the conductive layer on the upper surface side of the transferred laminate is removed. It is characterized by.

Further, according to another method of manufacturing a circuit board according to the present invention, as described in claim 3, a photosensitive resin is applied onto a metal plate, and then a space portion is covered, and , Forming a resin coating pattern exposing the line portion, forming a metal circuit pattern on the line portion by additive electrolytic plating, and then removing the photosensitive resin, and then forming the metal circuit pattern on the substrate. In the method of manufacturing a circuit board to be transferred to, the photosensitive resin is removed after the upper surface of the metal circuit pattern is polished and smoothed.

According to another aspect of the present invention, there is provided a method for manufacturing a circuit board according to the present invention.
Alternatively, in the method for manufacturing a circuit board as described in 3, the base material is a polyimide film.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a metal circuit is formed by additive electrolytic plating. Therefore, a metal plate having electrical conductivity or a base material on which a conductive layer is formed is used, and a stainless steel plate is a typical example of such a metal plate, and a metal film or a base material on which a conductive layer is formed is used. Examples include polyimide and ceramics coated with a conductive material such as ITO.

It should be noted that which of the base materials on which the metal plate or conductive layer is formed is selected depends on the performance required for the final product. For example, TA
In the case of B or FPC, a two-layer copper polyimide film (polyimide film having a copper thin film formed) is preferable in terms of miniaturization of the circuit pattern and heat resistance.

A metal plate such as a stainless plate is generally used when the circuit formed on the metal plate is transferred onto another insulating material (for example, a polyimide film). At that time, not only a metal plate on which a conductive layer such as a copper thin film is formed but also a metal plate on which no conductive layer is formed may be used, but it is preferable to use a metal plate on which a conductive layer is formed.

Because the metal thin film fixes the metal circuit pattern when transferring the circuit formed by additive after removing the resin coating pattern, the circuit is not displaced at the time of transfer. This is because the quality can be stabilized.

As a circuit transfer method, thermocompression transfer via an adhesive is preferable, but not limited to this.
Other methods may be used, and a photosensitive resin for forming a resin coating pattern that covers the space portion (portion where the circuit is not formed) and exposes the line portion (portion where the circuit is to be formed). Also for the (photoresist), a necessary one such as a commercially available UV curable photosensitive resin can be appropriately selected. It is preferable to use a high-definition photosensitive resin (photoresist) having a high resolution and a large aspect ratio because the precision of the circuit pattern is rapidly progressing.

Further, also for the formation of the metal circuit, a predetermined electrolytic plating such as electrolytic copper plating or electrolytic nickel plating is selected as necessary, and the surface of the copper circuit is formed for the purpose of preventing oxidation of the metal film and increasing hardness. Alternatively, multi-layer plating of nickel, tin, or the like may be performed. At that time, the surface of the metal circuit is smoothed when a metal circuit such as a copper circuit that is easily polished is formed.

Polishing can be cited as such a smoothing method, and the polishing material therefor is copper foil, polyester non-woven fabric, buff material for polishing the surface of a silicon wafer such as polyurethane foam, or the like, which corresponds to finer circuit patterns. Can be selected as appropriate, and as the polishing particles, 0.0
Colloidal silica of 1 μm to 0.05 μm can be used, and in order to maintain the uniformity of thickness after polishing, a metal mask for polishing can be used in addition to automatic control of positioning of the polishing surface. The conductive layer is preferably removed by soft etching, and the base material is preferably a polyimide film.

As described above, in the present invention, in the case of the non-transfer type, for example, a photosensitive resin (photoresist) is applied on the copper thin film of the polyimide film coated with the copper thin film, and a predetermined mask is applied. Form a resin coating pattern that exposes and develops the copper thin film in the space (the part where the circuit is not formed) and exposes the copper thin film in the line (the part where the circuit is to be formed) At the same time, after forming a copper circuit pattern on such a line portion by additive electrolytic plating, prior to peeling of the photosensitive resin (photoresist), the rounded circuit portion protruding to the upper part of the coating resin is uneven in thickness. It is also removed by polishing, including the photosensitive resin and the copper thin film in the space portion.

Therefore, the line width difference (line width variation) between the upper and lower sides of the circuit pattern is small, and the circuit surface is smooth.
Polyimide FPC having excellent bonding properties can be manufactured.

Also in the transfer type, a circuit board having excellent bondability can be obtained by polishing and smoothing the upper surface of the metal circuit pattern before removing the resin coating pattern. During the polishing, since the resin serves as a protector, it is possible to prevent the copper circuit from being damaged or peeled off.

[0022]

【Example】

Example 1 A sample of polyimide film manufactured by Ube Industries, Ltd. (50 mm × 150 mm, thickness 75 μm) was exposed to light.
After hydrogen peroxide oxidation and permanganese oxidation to improve the adhesiveness of the film surface, by the sputtering method,
A polyimide film having a copper thin film of 0.2 μm, that is, a base material having a conductive layer formed thereon was prepared.

Then, a UV curable photosensitive resin (PMER-N manufactured by Tokyo Ohka Co., Ltd.) was applied to the film by applying 25
A resin coating pattern (line) in which the copper thin film in the space portion (portion where the circuit is not formed) is coated and the copper thin film in the line portion (portion where the circuit is to be formed) is exposed by applying μm, exposing and developing. 25 μm in the portion and 35 μm in the space portion), and a copper circuit pattern having a thickness of about 25 μm was formed on the line portion by additive electrolytic copper plating.

The formed copper circuit had substantially the same shape as the line portion of the resin coating pattern, and its surface was slightly rounded higher than the resin coating pattern, and the thickness of the pattern was uneven. .

Therefore, this circuit is provided with a buffing abrasive (0.0%) for polishing a silicon wafer in the presence of the resin protective wall (while the UV curable photosensitive resin is still applied).
5 μm silica particles) were used to polish about 1 μm.

After polishing, the silica-based buffing abrasive was washed with water, and then the applied UV-curable photosensitive resin was peeled off with an alkali. The upper line width was 25 μm and the lower line width was 35 μm. A copper circuit was obtained, and the surface thereof was a smooth surface without irregularities.

Then, the copper thin film in the space portion (portion where the circuit is not formed) is soft-etched to form a circuit having a smooth surface with an upper line width of 22 μm, a lower line width of 25 μm and a space portion width of 35 μm. Was done.
Then, an IC chip with solder bumps was bonded onto the circuit and inspected, and as a result, the bondability was very good.

[Embodiment 2] ... 100 mm × 100 mm,
A copper thin film having a thickness of 0.5 μm was previously formed on a stainless steel plate having a thickness of 0.1 mm by electrolytic plating, and then a UV curable photosensitive resin film (PMER-N, 25 μm manufactured by Tokyo Ohka Co., Ltd.) was formed thereon. ) Is applied, exposed and developed to cover the copper thin film in the space part (the part where the circuit is not formed) and the thin copper film in the line part (the part where the circuit is to be formed) is exposed. A pattern (25 μm in the line portion and 35 μm in the space portion) was formed.

Next, when a copper circuit pattern having a thickness of 25 μm was formed on the line portion by additive electrolytic plating, the circuit showed a shape almost the same as the shape of the line portion, the upper line width was 25 μm, and the lower line was formed. 24 μm wide
However, the upper surface of the circuit was slightly rounded and unevenness was found.

Therefore, the silica-based buffing abrasive used in Example 1 was applied to the upper surface of this circuit in the presence of the resin protective wall (while the UV-curable photosensitive resin was still applied). After polishing the same abrasive with about 0.5 μm and then washing the abrasive with water, the applied UV-curable photosensitive resin is peeled off with an alkali to form a copper plate on the stainless steel plate. A copper circuit pattern was formed on the thin film.

Then, the laminated body of the copper thin film and the copper circuit pattern is transferred by heat and pressure onto the polyimide film through a polyimide adhesive, whereby a copper circuit whose entire surface is covered with the copper thin film is formed on the polyimide film. A pattern was formed, and then the copper thin film on the upper surface side of the laminate was removed by soft etching.

The circuit pattern thus obtained is
The upper line width is 23 μm, the lower line width is 25 μm,
There was little variation in the upper and lower line widths, and the surface was a smooth surface with no irregularities.

[0033]

As described above, according to the present invention, regardless of whether it is a transfer type or not, the variation in the upper and lower line widths of the circuit pattern is small, and the circuit surface is smooth and has excellent bondability. It is possible to obtain a circuit board having When the surface of the metal circuit is polished, the photosensitive resin serves as a protector, so that the metal circuit can be prevented from being damaged or peeled off.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masanori Akita 1-45 Oe 1-chome Otsu City Shiga Toray Engineering Co., Ltd. (72) Inventor Hideo Uehara 1-103-54 Yoshinodai, Kawagoe, Saitama Prefecture Inside Ray Tech Co., Ltd.

Claims (4)

[Claims] 1. A photosensitive resin is applied on a base material on which a conductive layer is formed, and then a resin coating pattern is formed to cover a space portion and expose a line portion, and to the line portion. A circuit board characterized in that a metal circuit pattern is formed by additive electrolytic plating, and then the upper surface of the metal circuit pattern is polished and smoothed, and then the photosensitive resin and the conductive layer in the space portion are removed. Manufacturing method. 2. A metal plate having a conductive layer formed thereon is coated with a photosensitive resin, and then a space portion is covered and a resin coating pattern exposing a line portion is formed, and the line portion is formed. A metal circuit pattern is formed by additive electroplating, then, the upper surface of the metal circuit pattern is polished and smoothed, the photosensitive resin is removed, and a laminate of the conductive layer and the metal circuit pattern is formed, A method for manufacturing a circuit board, which comprises transferring the conductive layer onto a base material and removing the conductive layer on the upper surface side of the transferred laminated body. 3. A resin coating pattern is formed by coating a photosensitive resin on a metal plate, then covering a space portion and exposing a line portion, and a metal circuit is formed on the line portion by additive electrolytic plating. In a method for manufacturing a circuit board, in which a pattern is formed and then the photosensitive resin is removed, the metal circuit pattern is transferred onto a base material, the photosensitive resin is removed by removing the upper surface of the metal circuit pattern. A method for manufacturing a circuit board, which is carried out after polishing and smoothing. 4. The method of manufacturing a circuit board according to claim 1, 2, or 3, wherein the base material is a polyimide film.