JP2008205244A - Printed wiring board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an opening for connection without damaging a surface of a base film. <P>SOLUTION: In the printed wiring board, a protection film (c) is overlapped with the base film (b) where a wiring pattern is formed by conductor foil (e) and it is thermocompression-bonded by a heating/pressurizing means. The base film (b) and the protection film (c) are polyimide. First opening parts h1, h2 and h3 from which the base film (b) is exposed and second opening parts k4, k5 and k6 from which only conductor foil (e) is exposed are formed in the protection film (c) and an adhesive layer (a). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a printed wiring board and a method for manufacturing a printed wiring board.

  Electronic devices such as personal digital assistants and digital cameras are required to be smaller, have higher performance, and be thinner. To meet the demands of these electronic devices, various modules can be used without internal signal connection connectors that occupy a large volume. Printed wiring boards with flexible connections without connector have been developed and commercialized.

  As a conventional so-called flexible printed circuit board (FPC), a wiring pattern made of copper foil or the like is formed on a base film, and a protective film (coverlay film) is bonded to the surface on which the wiring pattern is formed. Has been configured. Although a liquid crystal polymer is also used as the base film, in recent years, most of the polyimide film is used, and it is becoming common that the protective film is also used as the protective film. In the conventional printed wiring board, an opening (land portion) for connecting a mounted component or the like is formed. The opening is formed by a punching press using a mold.

However, a relatively large opening is possible with an opening with a punching press. However, when a small opening is required for high-density mounting, it is difficult to cope with the opening with the punching press. For this reason, in Patent Document 1, a non-thermoplastic polyimide film is heated and bonded via a thermoplastic polyimide film to the surface of the base plate on which the conductor circuit is formed on at least one surface. There is disclosed a printed wiring board in which the non-thermoplastic polyimide film and the thermoplastic polyimide film that are heat-bonded are etched with holes (Claim 1). A step of forming a conductor circuit on the base plate; a step of thermally bonding a non-thermoplastic polyimide film on the base plate on which the conductor circuit is formed via a thermoplastic polyimide film; and Forming a pattern with a resist film in conformity with the conductor circuit, and etching the bonded non-thermoplastic polyimide film and thermoplastic polyimide film into a desired pattern with a resist film integrally with alkali. A method for manufacturing a printed wiring board is disclosed. (Claim 7)
Japanese Patent No. 3356298

  However, the opening method of the coverlay (polyimide film, polyimide layer) described in Patent Document 1 described above is based on copper via an adhesive 14 having chemical resistance on one surface of the non-thermoplastic polyimide film 12 as a base film. A conductor circuit 16 made of foil or the like is formed, and a non-thermoplastic polyimide film 20 as a cover lay is further heat-bonded thereon via a thermoplastic polyimide film 18. A land portion 22 having a slightly larger area than the other portions is formed in a part of the conductor circuit 16 so as to be connected to a mounted component or the like, and is not connected to the thermoplastic polyimide film 18 on the land portion 22. A connection hole 24 is formed by etching in the thermoplastic polyimide film 20 in a state of being heat-bonded and integrated, and the land portion 22 and the mounted component can be soldered in the connection hole 24 ( (See paragraph 0028, FIG. 1, etc.). That is, since the resist film is formed in conformity with the conductor circuit 22, the connection hole 24 is sized so that a part of the land portion 22 is exposed. Enters the boundary portion between the land portion 22 and the non-thermoplastic polyimide film 12 as the base plate, and the adhesive is interposed at the boundary between the land portion 22 and the non-thermoplastic polyimide film 12 as the base plate. There is a problem that a part of the layer 14 is eroded and the wiring pattern is easily peeled off from the base film. In addition, if the base film is eroded by etching, the base film may be weakened. In order to prevent this, it is necessary to use an etching solution that does not cause such adverse effects, but such a complete etching solution has not yet been developed. In some cases, the alignment mark is applied to the wiring pattern, which may be used as a guideline for the processing position. Conventionally, the alignment mark is exposed by forming an opening by etching. Is eroded and the contour of the alignment mark is blurred. In addition, in the opening formation by the etching, the surface of the base substrate and the surface of the adhesive layer 14 on the base substrate 12 in the above-mentioned Patent Document 1 are roughened. For example, when bonding to a glass substrate for a liquid crystal display or the like. The problem was that the adhesive strength was reduced.

  Accordingly, an object of the present invention is to provide a printed wiring capable of forming an opening for connection without roughening the surface of the base film, and capable of forming openings of various sizes for wiring. It is providing the manufacturing method of a board and a printed wiring board.

  The printed wiring board of the present invention is a printed wiring board in which a protective film is superposed on a base film on which a wiring pattern is formed with a conductive foil via an adhesive, and is thermocompression bonded by a heating / pressurizing means. The adhesive layer is formed with a first opening for exposing the base film and a second opening for exposing only the conductive foil. This printed wiring board is manufactured by the following manufacturing method.

  The method for producing a printed wiring board according to the present invention is a method for producing a printed wiring board in which a protective film is superposed on a base film on which a wiring pattern is formed with a conductive foil, and is thermocompression bonded by a heating / pressurizing means. A first opening for exposing the base film and a second opening for exposing only the conductive foil are formed in the film and the adhesive layer, and the first opening for exposing the base film is a mold. The second opening that is formed by the above and exposes the conductor foil is formed by a mold or etching. Further, after forming a resist film covering the first opening and the second opening, the second opening is formed by etching.

  According to this invention, since the first opening exposing the base film is formed by the mold, the surface of the base film may be eroded by etching as in the case of forming by etching. Absent. That is, even when the second opening for exposing the conductor foil is formed by etching, the base film exposed from the first opening is protected by the resist film, so that it is not eroded by the etching, The strength of the base film can be maintained while the adhesiveness with the connecting parts is not impaired. And according to this printed wiring board manufacturing method, openings of various sizes can be formed for wiring.

  As this invention, it is preferable to use a polyimide for the said base film, a protective film, and an adhesive agent.

  According to this invention, the base film, the protective film, and the adhesive can be made of a unified material called polyimide, and a printed wiring board can be configured only with a conductive foil such as copper foil and polyimide, and is halogen-free. In addition, it is possible to realize a flexible printed circuit board corresponding to the UL standard, and to facilitate the recycling process.

  According to the present invention, the first opening for exposing the base film is formed by the mold, so that the surface of the base film is not eroded by etching. Accordingly, the strength of the base film is not adversely affected, and the base film surface is roughened to prevent the adhesive force from being lowered when adhering to a glass substrate or the like. For example, a glass substrate for a liquid crystal display And a printed wiring board connecting the control circuit and the control circuit. Also, openings of various sizes can be formed for wiring, and high-density mounting becomes possible. Further, a general etching solution can be used. The base film, the protective film, and the adhesive are made of a unified material called polyimide, so that a printed wiring board can be composed only of a conductive foil such as copper foil and polyimide, and is halogen-free and UL standard. A flexible printed circuit board corresponding to the above can be realized and the recycling process can be facilitated.

The best mode for carrying out the present invention will be described below with reference to the drawings.
Fig.1 (a) is the schematic diagram which looked at the printed wiring board Z1 to which this invention was applied from the upper surface. Moreover, FIG.1 (b) is AA sectional drawing of Fig.1 (a). In this embodiment, a base film b in which wiring patterns 1e, 2e,..., 10e are formed of a conductive foil e such as copper, and a protective film c covering the wiring patterns 1e, 2e,. And an adhesive layer a for adhering the protective film c and the base film b. The base film b is made of a polyimide film, the adhesive layer a is made of a polyimide adhesive, and the protective film (coverlay) c is made of a polyimide film. Since the base film b is made of a polyimide film, the printed wiring board Z1 has both flexibility and heat resistance. However, the thickness of the portion where the bending strength is desired to be increased and the insertion destination such as a socket are made to coincide. In this case, a reinforcing plate such as polyimide is appropriately bonded to the outside of the base film b (the lower side of the base material b in FIG. 1B). The reinforcing plate is preferably removed from the outer shape after being bonded to the substrate with reference to the alignment mark. This is because the reinforcing plate can be accurately bonded to a desired position.

  The protective film c and the adhesive layer a are provided with first openings h1, h2, h3 and second openings k4, k5, k6 for wiring formation. The first openings h1, h2, h3 are for the purpose of exposing the base film b, and are formed by a mold. The first openings h1, h2, h3 are formed larger than the wiring patterns 1e, 6e and 7e, 9e and 10e made of the conductor foil e, respectively. The second openings k4, k5, k6 are for the purpose of exposing only the conductor foil e, and are formed by etching in addition to the mold. That is, the second openings k4, k5, and k6 may be used separately depending on the size. However, in order to simplify the manufacturing process, it is preferable to first form a large opening and then form a smaller opening on the conductor foil e. The mold is excellent in forming a relatively large opening, and the etching is excellent in forming a high density of fine openings. That is, a large opening can be formed instantaneously in the mold. In the etching, a fine opening can be formed without being affected by the accuracy of the bonding position between the protective sheet c and the base film b, and the mounting density of chip parts such as ICs can be increased.

  The wiring patterns (wiring electrodes) 2e, 3e, and 4e are exposed through the second openings k4, k5, and k6 having a size smaller than the width of each wiring pattern 2e, 3e, and 4e. It is exposed. The wiring patterns 2e, 3e, 4e are used as electrodes for mounting a chip component such as an IC, for example. However, a large opening of about 2 mm or more may be formed by a mold. In addition, the surface where the conductor foil e is exposed can be easily mirror-finished by a surface treatment such as chemical polishing.

  The wiring patterns 6e and 7e are exposed through an opening h2 formed by a mold having a larger size than the wiring patterns 6e and 7e. The height between the wiring patterns 6e and 7e is reduced by these thicknesses, which is suitable for mounting a component in which the flatness of the mounting surface is important, for example.

  The wiring patterns 5e and 8e connect the wiring electrodes to form a wiring circuit, and are protected by the adhesive layer a and the protective sheet c so as not to be damaged from the outside.

  The wiring pattern 9e composed of a large number of wiring electrodes and the positioning wiring pattern 10e formed on both sides are exposed through an opening h3 formed by a mold having a size larger than the wiring patterns 9e and 10e. The line m is the end of the protective sheet c and the adhesive layer a, and the opening h3 is a space opened on one side (upward from the line m in FIG. 1A). The wiring pattern 9e is also called a terminal electrode. For example, the wiring pattern 9e is inserted into a connector of an external device for electrical connection, or is bonded to a glass substrate of a liquid crystal display for electrical connection. The wiring pattern 10e is a positioning mark for connecting the terminal electrode 9e to an external connector or a glass substrate.

  The wiring pattern 1e is also called an alignment mark, and is used to indicate a reference position for recognizing a mounting position when a chip component such as an IC is mounted on the printed wiring board Z1. As the alignment mark of the wiring pattern 1e is smaller and the outline is clearer, the recognition position accuracy becomes higher. In the present embodiment, the wiring pattern 1e is exposed through the first opening h1 formed by a mold having a size larger than the width of the wiring pattern 1e, so that the outline can be clearly recognized. Conventionally, since the opening is formed by etching to expose the alignment mark 1e, the periphery of the alignment mark 1e is eroded by the etching solution, and it is difficult to reduce the alignment mark 1e. Was often blurred.

  FIG. 2 is a process flowchart showing the manufacturing procedure of the present embodiment. S1 and S2 are processes for processing the base material 1 composed of the base film b and the conductor foil e. S11 and S12 are steps for processing the substrate 2 composed of the protective film c and the adhesive layer a. S3 to S6 are processes in which the base material 1 and the base material 2 are combined. FIG. 3 is a cross-sectional view of a work in the main manufacturing process. A method of manufacturing the printed wiring board Z1 to which the present invention is applied will be described below in accordance with the process flowchart shown in FIG.

  First, a conductive foil e is formed on one surface of a base film b made of a polyimide film to form a substrate 1 (FIG. 2 (S1), FIG. 3 (a)). As the conductor foil e, a conductive material such as copper foil, aluminum foil or nickel foil is used. The conductor foil e may be formed by plating or additive method, or may be bonded with an adhesive layer interposed between the conductor foil e and the base film b. Then, desired wiring patterns 1e to 10e are formed by etching or the like (FIG. 2 (S2)).

  Further, as a step different from the steps S1 and S2, the base material 2 is formed by bonding the polyimide adhesive sheet a to one surface of the protective film c made of polyimide (FIG. 2 (S11), FIG. 3 (b)). ). Then, desired first openings h1 to h3 are formed by a mold (FIG. 2 (S12)). It is also possible to use a single layer of the polyimide adhesive sheet as the protective film c. The first openings h1, h2, and h3 can be formed larger than the wiring patterns 1e, 6e, 7e, 9e, and 10e made of the conductor foil e by forming a mold (FIG. 1 ( a) (b)).

  Next, the surface of the conductive foil e of the substrate 1 and the surface of the adhesive layer a of the substrate 2 are faced to each other, for example, the first openings h1 corresponding to the wiring patterns 1e, 6e, 7e, 9e, and 10e, respectively. , H2 and h3 are aligned so that the base material 1 and the base material 2 are brought into close contact with each other by the pressurizing / heating means K1 and K2 and are heated by pressing (FIG. 2 (S3 ), FIG. 3 (c)).

  Next, a resist film r such as a solder resist is applied to the surface of the integrally formed base films b, a and c (FIG. 3D) on which the conductor foil e is formed, and the protective film c and the first opening. The wiring patterns 1e, 6e, 7e, 9e, 10e exposed by the parts h1, h2, h3 are formed so as to cover them, and the etching patterns k1, k2 are formed at positions where desired openings k4, k5, k6 are formed. , K3 (FIG. 2 (S4), FIG. 3 (e)). The etching pattern can be formed by the resist film r by a screen printing method, a dry film / photographic method, or a liquid resist / photographic method, which is used depending on the application. By covering the first openings h1, h2, and h3 with the resist film r, the surface of the base film b and the wiring patterns 1e, 6e, 7e, 9e, and 10e are eroded, and the surface is roughened. There is no such thing as weakening film b. On the other hand, the etching solution is not limited to a specific one as in the prior art, and a general one can be used.

  Then, desired openings k1, k2, and k3 are formed by polyimide etching (FIG. 2 (S5), FIG. 3 (f)), and the resist film r is removed to complete the printed wiring board Z1 (FIG. 2 ( S6), FIG. 3 (g)). In order to make the surface of the conductor foil e such as copper exposed to a mirror finish, it is cleaned using, for example, a chemical polishing liquid composed of dilute sulfuric acid and hydrogen peroxide. In order to increase the corrosion resistance of the surface and make it easier to mount, a protective film such as gold plating using nickel as a base plating is formed.

  In order to simultaneously manufacture a large number of the above-described printed wiring boards Z1, a plurality of wiring patterns to be printed wiring boards Z1 are formed on the base material 1 and the base material 2, and a die or the like is formed at the end of the processing step. There is a manufacturing method such as separating the printed wiring board Z1 into a printed wiring board Z1.

(Example)
By the manufacturing method of the present embodiment, the printed wiring board Z1 was manufactured by setting the thickness of the protective sheet c to 10 to 12.5 μm and the thickness of the adhesive layer (adhesive sheet) a to 10 to 15 μm. The minimum processing size (length, diameter) of the first opening by the mold was 1 mm and the positional accuracy was 0.15 mm. However, in etching, the size (length, diameter) of the opening was set to 0. The position accuracy could be set to 07 mm, and the positional accuracy could also be set to 0.05 mm. Thus, the base film b can be formed without weakening or roughening the surface of the base film b, and openings of various sizes for wiring can be formed.

    As described above, the present invention is not limited to the embodiment described above. For example, here, the base film b is a polyimide film, but there is no problem even if a liquid crystal polymer or the like is used. In the present embodiment, the single-sided copper-clad plate sheet 1 is applicable, but can also be applied to a double-sided copper-clad plate sheet or a laminated sheet. Thus, it goes without saying that the present invention can be modified as appropriate without departing from the spirit of the present invention.

It is a schematic diagram which shows the printed wiring board of embodiment to which this invention is applied. It is a process flowchart which shows the manufacture procedure of the said embodiment. It is workpiece | work sectional drawing in the manufacturing process of the said embodiment.

Explanation of symbols

Z1 printed wiring board,
1, 2, base material,
a adhesive layer,
b Base film,
c Protective film (coverlay film),
e, 1e, 2e, ..., 10e Conductor foil (wiring pattern),
h1, h2, h3 first opening,
k4, k5, k6 second opening,
r Resist film

Claims (7)

  A printed wiring board in which a protective film is superimposed on a base film on which a wiring pattern is formed with a conductive foil via an adhesive and is thermocompression bonded by a heating / pressurizing means. The printed wiring board characterized by the 1st opening part which exposes a film, and the 2nd opening part which exposes only conductor foil.   The size of the second opening for exposing the conductive foil is an opening smaller than the size of the first opening for exposing the base film, and the second opening is smaller than the pattern width of the conductive foil. The printed wiring board according to claim 1, wherein the printed wiring board is an opening.   The printed wiring board according to claim 1, wherein the base film, the protective film, and the adhesive are polyimide.   A method of manufacturing a printed wiring board in which a protective film is superimposed on a base film on which a wiring pattern is formed with a conductive foil via an adhesive and is thermocompression-bonded by a heating / pressurizing means. The first opening for exposing the base film and the second opening for exposing only the conductive foil are formed, and the first opening for exposing the base film is formed by a mold, and the conductive foil is formed. A method for manufacturing a printed wiring board, wherein the second opening exposing the substrate is formed by a mold or etching.   5. The method of manufacturing a printed wiring board according to claim 4, wherein after forming a resist film covering the first opening and the second opening, the second opening is formed by etching.   The size of the second opening that exposes the conductive foil is smaller than the size of the first opening that exposes the base film, and the second opening is formed by etching. The manufacturing method of the printed wiring board of Claim 4.   The method for manufacturing a printed wiring board according to claim 4, wherein polyimide is used for the base film, the protective film, and the adhesive.

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