JPH07123178B2 - Flexible wiring board and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a flexible wiring board, particularly a high-quality flexible wiring board having excellent heat resistance and high dimensional accuracy, and a method for manufacturing the same.

[Prior Art] Flexible wiring boards are widely used in the field of electronic devices because they are highly flexible and thin. But,
The conventional manufacturing method of the flexible wiring board has a complicated manufacturing process, and the flexible wiring board manufactured by the conventional method has a drawback inevitably caused by its structure.

That is, the conventional flexible wiring board is shown in FIG.
As shown in the example, a material in which a copper foil 3 as a conductor is adhered to an insulating base film 1 with an adhesive 2 is used, and an insulating cover lay film 5 is further adhered to the copper foil 3 with an adhesive 4. Is provided.

Therefore, even when a polyimide film is used for the insulating film, since a rubber-modified epoxy resin or a rubber-modified phenol resin is used as the adhesive layer, it becomes inferior in terms of heat resistance, particularly solder heat resistance. Resin may blister or peel off during dip coating.

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to solve the above-mentioned conventional drawbacks and to provide a flexible wiring board having high quality, particularly excellent heat resistance, and high dimensional accuracy, and the flexible wiring board. It is an object of the present invention to provide a manufacturing method capable of manufacturing a resin by a simple process.

[Means for Solving the Problems] In order to achieve such an object, in the flexible wiring board of the present invention, a predetermined portion of one surface of the metal conductor plate is directly covered with a polyimide resin, and the other is covered. Since a predetermined portion of the surface is directly covered with the solder resist and therefore no adhesive is used, the heat resistance is excellent.
The polyimide resin is applied to a predetermined portion to form a first insulating layer, and the solder resist is applied to a predetermined portion, or after being applied, the second insulating layer is patterned by a photographic method. Form.

That is, in the first embodiment of the flexible wiring board of the present invention, a predetermined portion of one surface of the metal conductor plate is directly covered with a polyimide resin, and a predetermined portion of the other surface of the metal conductor plate is directly covered with a solder resist. It is characterized by

The second embodiment of the flexible wiring board of the present invention has a terminal portion of a metal conductor on at least one end portion of a metal conductor plate, and at least one surface of the terminal portion is not covered with an insulating layer,
A specific portion of the metal conductor plate other than the terminal portion is directly covered with a polyimide resin, and a predetermined portion of the other surface of the metal conductor plate is directly covered with a solder resist. And

The first embodiment of the method for manufacturing a flexible wiring board of the present invention is
A step of forming a photoresist pattern on a thin metal plate, a step of forming a conductor pattern by using a photoresist pattern on a thin metal plate, and a solvent-soluble polyimide in which only a predetermined portion of the surface of the thin metal plate having the conductor pattern is formed. A step of forming a first insulating layer by coating a system resin, a step of removing the thin metal plate, and a second insulating layer by coating a predetermined portion of the surface from which the thin metal plate has been removed with a solder resist. And a step of forming.

The second embodiment of the method for manufacturing a flexible wiring board of the present invention is
A step of forming a photoresist pattern on a metal thin plate, a step of forming a conductor pattern using a photoresist pattern on a metal thin plate, and a solvent-soluble polyimide only on a predetermined portion of the surface of the metal thin plate on the side having the conductor pattern. A step of forming a first insulating layer by coating a resin based resin, a step of removing the thin metal plate, a step of coating a solder resist on the surface from which the thin metal plate has been removed, and a photograph of the coated solder resist And a step of forming a second insulating layer by patterning by a method.

The third embodiment of the method for manufacturing a flexible wiring board of the present invention is
A step of forming a first insulating layer by coating a solvent-soluble polyimide resin on a predetermined portion of one surface of the metal foil, and a portion of the metal foil which is not covered with the first insulating layer. A step of forming a resist pattern, a step of pattern etching a metal foil, a step of removing the resist pattern, and a predetermined portion of the surface of the metal foil opposite to the surface on which the first insulating layer is formed. And forming a second insulating layer by coating a solder resist on the substrate.

A fourth embodiment of the method for manufacturing a flexible wiring board of the present invention is
A step of forming a first insulating layer by coating a solvent-soluble polyimide resin on a predetermined portion of one surface of the metal foil, and a portion of the metal foil which is not covered with the first insulating layer. A step of forming a resist pattern, a step of pattern-etching the metal foil, a step of removing the resist pattern, and a step of applying a solder resist on the surface of the metal foil opposite to the surface on which the first insulating layer is formed. The method is characterized by including a step of coating and a step of patterning the coated solder resist by a photographic method to form a second insulating layer.

[Operation] Since the flexible wiring board of the present invention has no adhesive, it can exhibit excellent heat resistance. Furthermore, since the second insulating layer is formed by using the pattern coating method or the photographic method, the flexible wiring board can be manufactured in a simple process, and the flexible wiring board having excellent dimensional accuracy can be manufactured. it can.

[Examples] Hereinafter, the present invention will be described in detail with reference to the drawings.

1 (a) to 1 (e) show an example of a wiring board having terminals and lands as an embodiment of the flexible wiring board of the present invention.

1 (a) is a plan view of a portion including a terminal portion of a flexible wiring board, FIG. 1 (b) is a plan view including a land portion of the flexible wiring board, and FIG. 1 (c) is FIG. 1 (a). 1) is a sectional view taken along line XX in FIG. 1A, FIG. 1D is a sectional view taken along line YY in FIG. 1A, and FIG. 1E is taken along line ZZ in FIG. 1B. FIG.

In FIGS. 1 (a) to (e), 11 is a conductor plate such as copper,
11A is its terminal portion, 11B is the exposed land portion of the conductor plate 11,
12 is an insulating layer made of a polyimide resin provided on one main surface of the conductor plate 11, 12 'is an insulating layer made of solder resist provided on the other main surface of the conductor plate 11, and 13 is a conductor plate 11. It is a photoresist layer that fills in between the patterns.

As shown in the figure, the flexible wiring board according to the present invention, except for the terminal portion 11A and the land portion 11B, one main surface and the other main surface of the conductor plate 11, respectively, by the polyimide resin layer 12 , And the solder resist layer 12 ′ is directly coated.

A flexible wiring board having such a structure is easily manufactured by the steps shown in FIGS. 3 (a) to (e), 4 (a) to (e), and 5 (a) to (e). be able to.

FIGS. 3 (a) to 3 (e) are cross sections taken along line XX in FIG. 1 (a), FIGS. 4 (a) to 4 (e) are cross sections taken along line YY, and FIGS. (E) shows the cross section along the line ZZ.

Next, each step will be briefly described.

(1) A photoresist pattern 22 is formed on the thin metal plate 21 (FIGS. 3 (a), 4 (a) and 5 (a)).

(2) A conductor pattern 23 is formed on the thin metal plate 21 along the resist pattern 22 by pattern plating. (Third
Figure (b), Figure 4 (b), Figure 5 (b)).

(3) The first insulating layer 24 is formed only on a necessary portion of the resist pattern 22 and the conductor pattern 23 by pattern coating with a polyimide resin (FIGS. 3 (c) and 4 (c)). , FIG. 5 (c)). This insulation layer 24
The land 25 is exposed in the uncovered portion, that is, the opening portion.

(4) The thin metal plate 21 is removed (FIG. 3 (d), FIG. 4 (d), FIG. 5 (d)).

(5) The second insulating layer 24 'is formed only on a necessary portion of the exposed surfaces of the patterns 22 and 23 by pattern coating with solder resist (FIGS. 3 (e), 4 (e), 5). Figure (e)). The land 25 'is exposed in the uncovered portion of the insulating layer 24', that is, in the opening portion.

In this way, a flexible wiring board having terminals and lands as shown in FIGS. 1A to 1E is manufactured.

Next, specific examples of the flexible wiring board of the present invention will be shown.
The invention is not limited to only these examples.

Alternatively, instead of the above step (5), an ultraviolet curable solder resist is applied to the entire exposed surfaces of the patterns 22 and 23, and then exposed to ultraviolet rays through a pattern mask to cure only necessary portions. Then, the insulating layer 24 'can be formed by a so-called photographic method in which the phenomenon is then performed. This is particularly preferable when the pattern is fine and the dimensional accuracy needs to be strictly determined.

The flexible wiring board having such a structure is also manufactured by the steps shown in FIGS. 6 (a) to (e), 7 (a) to (e) and 8 (a) to (e). You can

6 (a) to 6 (e) are cross sections taken along line XX in FIG. 1 (a), FIGS. 7 (a) to 7 (e) are cross sections taken along line YY in FIG. 1 (a), 8 (a)-(e) are the lines of FIG. 1 (d).
A cross section along ZZ is shown.

These steps will be described step by step.

(1) The insulating layer 32 is formed by pattern-coating a polyimide resin on a predetermined portion of one surface of the metal foil 31 excluding terminals and the like (FIGS. 6A, 7A, and 7A). FIG. 8 (a)).

(2) Resist pattern 3 on the exposed surface of the metal foil 31
3, a resist layer 33 'and a resist pattern 33 "are formed. The insulating layer in FIGS. 6 (b) and 7 (b)
No resist pattern is formed on the side of 32, but there is no problem in forming a resist on this portion as well.
Furthermore, although the lower resist layer 33 'in FIG. 7 (b) is not patterned, it is also possible to pattern this resist layer 33' and etch the metal foil 31 from both sides in the subsequent step. It is possible (Fig. 6 (b), Fig. 7 (b), Fig. 8 (b)).

(3) The metal foil 31 is etched using an appropriate etching solution (FIG. 6 (c), FIG. 7 (c), FIG. 8 (c)).

(4) The remaining resist portions 33, 33 'and 33 "are stripped and removed using a stripping solution (Fig. 6 (d), Fig. 7 (d), Fig. 8 (d)).

(5) A predetermined portion of the insulating layer 32 is pattern-coated with a solder resist to form an insulating layer 32 '(FIGS. 6 (e), 7 (e), 8 (e)).

In place of the above step (5), a UV-curable solder resist is applied to the entire surface of the insulating layer 32, and then exposed to UV light through a pattern mask to obtain the solder resist required. The insulating layer 34 is formed by so-called photographic method in which only a part is cured and then developed.
Can also be formed.

Example 1 A negative resist "Microresist 747" manufactured by Eastman Kodak Co. was coated on an aluminum thin plate having a thickness of 80 μm so that the film thickness was 5 μm. The resist-coated aluminum plate was pre-baked, exposed through a high-pressure mercury lamp through the wiring board pattern, developed using a dedicated developer and rinse solution, and post-baked to form a resist pattern on one side of the aluminum thin plate. .

Next, electrolytic copper plating was performed using a copper pyrophosphate plating bath with the aluminum thin plate having the resist pattern formed as a cathode. The conductor pattern obtained has a conductor width of 20.
The thickness was 0 μm, the conductor interval was 250 μm, and the conductor thickness was 40 μm.

Then, using a stainless metal mask, polyimide resin "U varnish" manufactured by Ube Industries, Ltd. except for the terminals and lands was pattern-coated by, for example, screen printing, and dried and cured to obtain an insulating layer having a thickness of 20 μm.
The aluminum sheet was then etched away with 10 weight percent hydrochloric acid. At this time, since the photoresist left on the terminal portion has weak mechanical strength and is not supported by the insulating layer, the end portion of the insulating layer (12A in FIG. 1A) is
Part). Therefore, no photoresist remains on the terminals. After that, by screen printing, "FOC-800G" manufactured by Taiyo Ink Mfg. Co., Ltd. is also pattern-coated on the back side except the terminals and lands, and UV cured to form an insulating layer with a thickness of 20 μm, and flexible with terminals and lands. A wiring board was obtained. After that, the terminal portion and the land portion were subjected to flux treatment, and were dipped in a solder bath at 280 ° C. for about 5 seconds for solder coating, but no deterioration was observed in the resin layer.

Example 2 As in Example 1, after forming a resist pattern on an aluminum thin plate, copper plating was performed to obtain a conductor width of 300 μm and a conductor interval of 350.
A conductor pattern having a thickness of 35 μm and a conductor thickness of 35 μm was obtained.

Then, a solvent-soluble polyamide-imide resin synthesized from diamino-diphenyl ether and trimetic acid chloride is screen-printed except for terminals and lands using a stainless metal mask, and dried and heat-treated to form a 30 μm thick insulating layer. Obtained. Then, the aluminum thin plate was removed by etching with 10% by weight of hydrochloric acid, and the photoresist was stripped using a resist stripping solution "N-500" manufactured by Nagase Chemicals. After that, Taiyo Ink Mfg. Co., Ltd.'s solder resist "PS
R-4000 "is applied over the entire surface by a blade coater, pre-baked, exposed with a high-pressure mercury lamp through a pattern mask, developed with a special developer, and then post-baked to form an insulating layer with a thickness of 20 μm. A flexible wiring board having terminals and lands was obtained. Then, the terminal portion and the land portion were subjected to flux treatment, and the solder coating was performed by dipping in a solder bath at 260 ° C. for about 10 seconds, but no deterioration was observed in the resin layer. The adhesive strength and dimensional accuracy were also excellent.

As the conductor metal, any metal can be used as long as it is a metal that can be electroplated, but copper is preferable from the viewpoint of conductivity and economy.

The removal of the thin metal plate can be performed by peeling (peeling off) instead of etching as in the present embodiment. However, in order not to disturb the conductor pattern, etching is preferable, and in the case of etching, one having an etching characteristic different from that of the conductor metal is preferable. When copper is used as the conductor metal as in this embodiment, it is desirable to use aluminum, tin, zinc or the like.

The photoresist used for the conductor layer pattern plating is
It is also preferable to peel off at an appropriate time after the plating is finished, for example, after the plating is finished or after the metal thin plate is removed.

Since the polyimide resin used in the present invention is pattern-coated, it is solvent-soluble. Unlike the case of adhering the film to the metal foil, since it is coated with a liquid type, there is no bubble left between the metal and the insulating layer, the adhesiveness can be improved, and no external force is applied. The dimensional accuracy of the product can be improved.

Polyimide-based resins include polyamic acid, polyimide resin, polyamide-imide resin, polyester-modified imide resin, silicone-imide resin, etc., and solvent-soluble imide group-containing polymers, particularly solvent-soluble polyamide-imide resin, are preferable, It does not occur, and it has excellent adhesiveness and dimensional accuracy.

Still another embodiment of the present invention will be shown below.

Example 3 On a copper foil having a thickness of 35 μm, a polyimide resin “U varnish” manufactured by Ube Industries, Ltd. was removed from the terminals using a metal mask made of stainless steel, for example, pattern coating was performed by screen printing, followed by drying and curing. Then, an insulating layer having a thickness of 20 μm was obtained.

Next, a negative resist "Microresist 747" manufactured by Eastman Kodak Company was applied. The resist-coated copper foil was pre-baked, exposed through a high-pressure mercury lamp through the pattern of the wiring board, developed using a dedicated developer and rinse solution, and post-baked to form a resist pattern.

Then, copper was etched using a ferric chloride solution to obtain a conductor pattern having a conductor width of 200 μm and a conductor interval of 250 μm.

Furthermore, the resist stripper "N-50" manufactured by Nagase Kasei Co., Ltd.
The photoresist was stripped using "0".

After that, by screen printing, "FOC-800G" manufactured by Taiyo Ink Mfg. Co., Ltd. was also pattern-coated on the back side, except for the terminals and lands, and then UV-cured to form a 20 μm thick insulating layer. Thus, a flexible wiring board having terminals and lands was obtained. Then, the terminal portion and the land portion were subjected to a flux treatment and dipped in a solder bath at 280 ° C. for about 5 seconds for solder coating, but no deterioration was observed in the resin layer.

Example 4 Polyamideimide resin synthesized from diamino-diphenyl ether and trimellitic acid on a copper foil having a thickness of 50 μm,
Using a stainless steel metal mask, remove the terminals, pattern-coat, then dry and heat-treat
An insulating layer having a thickness of μm was obtained.

Then, a negative resist "Microresist 747" manufactured by Eastman Kodak Co., Ltd. is applied to the surface of the copper foil on which the insulating layer is not formed, and then prebaked, through the pattern of the wiring board, and exposed by a high-pressure mercury lamp, The resist pattern was developed using a dedicated developer and rinse solution, and post-baked to form a resist pattern only on the surface of the copper foil opposite to the above-mentioned insulating layer. Next, after the polypropylene adhesive tape was attached to the terminal portion on the insulating layer side, copper was etched using a ferric chloride solution to give a conductor width of 30
A conductor pattern having a conductor interval of 350 μm at 0 μm was obtained.

Furthermore, a resist stripper "N-500" manufactured by Nagase Kasei Co., Ltd.
Was used to peel off the photoresist, and then the polypropylene tape was peeled off.

After that, Taiyo Ink Mfg. Co., Ltd. solder resist "PSR-4000" is applied over the entire surface with a blade coater,
After pre-baking, it was exposed to a high-pressure mercury lamp through a pattern mask and developed using a dedicated developer to obtain a flexible wiring board having terminals and lands. Then, the terminal portion and the land portion were subjected to flux treatment and dipped in a solder bath at 260 ° C. for about 10 seconds to perform solder coating, but no deterioration was observed in the resin layer. The adhesive strength and dimensional accuracy were also excellent.

Incidentally, the etching resist portion 33,3 used in the present invention
3'and 33 "prevent copper etching under the resist,
Conductor that can be peeled off in the next step and is patterned
The resist portion 33 on the 31 side is produced by a photographic method, screen printing or the like, and a photoresist, a resist ink or the like can be used. If fine patterning is not particularly required, tape, gum arabic, gelatin, wax or the like may be used instead of the resist layer 33 '. Furthermore, solder can also be used as an etching resist.

9 and 10 show another embodiment in which the structure of the terminal portion is different.

When the terminal portion is exposed only on one side and the other side may be insulated, it does not matter if the insulating layers 12 and 12 'are pattern-coated, for example, as shown in FIG.
12 is evenly provided up to the tip of the terminal portion 11A, and the second insulating layer 1
2'is not provided in the terminal portion 1A.

Alternatively, as shown in FIG. 10, the end portion of the first insulating layer 12 can be provided only on the terminal portion 11A. In this way, the insulating layer 12 can be used as a reinforcing material for the terminal portion 11A.

FIG. 11, FIG. 12 and FIG. 13 show three embodiments of the flexible wiring board of the present invention having different structures of lands.

In the embodiment of FIG. 11, the insulating layers 12 and 12 'are not provided on both surfaces of the land portion 11B.

In the embodiment of FIG. 12, the uncovered portion of the insulating layer 12, that is, the opening portion is made larger than the land portion 11B.

In the embodiment of FIG. 13, a through hole 20 is formed in the land portion 11B, and a pin or the like can be inserted into this hole 20.

In the above description, the flexible wiring board with terminals is mainly described, but the terminal portion does not necessarily have to be provided in advance. It is also possible to expose the terminal portion by cutting out a required dimension from the flexible wiring board where the terminal portion is not exposed and removing the polyimide resin with a corrosive liquid such as hydrazine.

[Effects of the Invention] As described above, according to the present invention, since there is no adhesive layer between the conductor layer and the insulating layer, there is no deterioration due to heat due to the adhesive, and the heat resistance of the polyimide resin is improved. It is possible to obtain a high-quality flexible wiring board having excellent heat resistance and high dimensional accuracy by utilizing the characteristics, and moreover, it is possible to easily manufacture such a wiring board by a simple manufacturing process.

[Brief description of drawings]

1 (a) and 1 (b) are plan views showing an embodiment of a flexible wiring board of the present invention, and FIGS. 1 (c) and 1 (d) are respectively FIG. 1 (a).
XX and YY line sectional views, FIG. 1 (e) is a ZZ line sectional view of FIG. 1 (b), FIG. 2 is a sectional view showing a structure of a conventional flexible wiring board, and FIG. (E), FIGS. 4 (a) to (e) and FIGS. 5 (a) to (e) are cross-sectional views for explaining one embodiment of the manufacturing process of the flexible wiring board of the present invention, and FIG. 6 (a). ~ (E), Fig. 7 (a) ~ (e) and Fig. 8 (a) ~ (e) are sectional views, Fig. 9 and Fig. 9 for explaining another embodiment of the manufacturing process of the flexible wiring board of the present invention. FIG. 10 is a sectional view showing another two embodiments of the terminal portion of the flexible wiring board of the present invention, and FIGS. 11 to 13 are sectional views showing other three embodiments of the land portion of the flexible wiring board of the present invention. is there. 1 ... Base film, 2, 4 ... Adhesive, 3 ... Conductor,
5 ... Coverlay film, 11 ... Conductor plate, 11A ... Terminal part, 11B ... Land part, 12 ... Insulation layer made of polyimide resin, 12 '... Insulation layer made of solder resist, 13
...... Photoresist layer, 21 …… Metal thin plate, 22 …… Resist pattern, 23 …… Conductor pattern, 24,32 …… Insulation layer made of polyimide resin, 24 ′, 32 ′ …… Insulation layer made of solder resist, 25 , 25 '…… Land, 31 …… Metal foil, 3
3,33 ″ …… resist pattern, 33 ′ …… resist layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shunji Chikamori 648, Hirookaue, Haruno-cho, Agawa-gun, Kochi Prefecture Nippon ▲ Kodoshi Paper Industry Co., Ltd. (56) Reference JP-A-57164597 (JP, A) ) Actually open 57-104563 (JP, U)

Claims (6)

[Claims] 1. A flexible structure characterized in that a predetermined portion of one surface of a metal conductor plate is directly covered with a polyimide resin and a predetermined portion of the other surface of the metal conductor plate is directly covered with a solder resist. Wiring board. 2. A metal conductor plate having a terminal portion of a metal conductor on at least one end portion, at least one surface of the terminal portion not being covered with an insulating layer, and the metal conductor plate other than the terminal portion. A flexible wiring board, characterized in that a predetermined portion of one surface is directly covered with a polyimide resin, and a predetermined portion of the other surface of the metal conductor plate is directly covered with a solder resist. 3. A step of forming a photoresist pattern on a metal thin plate, a step of forming a conductor pattern on the metal thin plate using the photoresist pattern, and a surface of the metal thin plate on the side having the conductor pattern. Forming a first insulating layer by coating a solvent-soluble polyimide resin only on a predetermined part of the above, a step of removing the metal thin plate, and a solder resist only on a predetermined part of the surface from which the metal thin plate is removed. And a step of forming a second insulating layer by coating the same. 4. A step of forming a photoresist pattern on a metal thin plate, a step of forming a conductor pattern on the metal thin plate using the photoresist pattern, and a surface of the metal thin plate on the side having the conductor pattern. Forming a first insulating layer by coating a solvent-soluble polyimide resin only on a predetermined portion of the above step, removing the thin metal plate, and coating a solder resist on the surface from which the thin metal plate has been removed. And a step of forming a second insulating layer by patterning the coated solder resist by a photographic method, the method for producing a flexible wiring board. 5. A step of forming a first insulating layer by coating a predetermined portion of one surface of the metal foil with a solvent-soluble polyimide resin, and the first insulating layer of the metal foil. A step of forming a resist pattern on a portion that is not covered, a step of pattern etching the metal foil, a step of removing the resist pattern, and a step of forming the first insulating layer of the metal foil. A step of forming a second insulating layer by coating a predetermined portion of the surface opposite to the surface with a solder resist, the method for manufacturing a flexible wiring board. 6. A step of forming a first insulating layer by coating a solvent-soluble polyimide resin on a predetermined portion of one surface of the metal foil, and the first insulating layer of the metal foil. A step of forming a resist pattern on a portion that is not covered, a step of pattern etching the metal foil, a step of removing the resist pattern, and a step of forming the first insulating layer of the metal foil. A step of coating a solder resist on a surface opposite to the surface, and a step of patterning the coated solder resist by a photographic method to form a second insulating layer. Production method.