JP3831304B2 - Flexible circuit board and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flexible circuit board and a manufacturing method thereof, and more particularly to a flexible circuit board and a manufacturing method thereof capable of suitably forming a surface protective layer on a circuit wiring pattern.
[0002]
[Prior art]
The flexible circuit board is configured using a copper-clad laminate in which a copper foil is provided on the surface of a flexible insulating base material. That is, a photoresist is applied to copper foil, and a series of processes such as exposure, development, etching, and resist stripping are performed to form a circuit wiring pattern. On this circuit wiring pattern, electronic components such as circuit components and external boards are formed. It is manufactured by forming a surface protective layer having an opening at a portion where a terminal for connection to a component or a circuit is formed, punching it out with a mold or the like, and processing the outer shape.
[0003]
Here, the surface protective layer has an opening formed by punching with a mold or the like on the flexible insulating film having an adhesive layer on one surface, and the flexible insulating film is formed on the circuit wiring pattern. To form a surface protective layer.
[0004]
[Problems to be solved by the invention]
In such a surface protective layer, it has become impossible to cope with the miniaturization and high precision of openings for terminal formation, which are required in electronic devices with higher functions and higher density in recent years.
[0005]
In recent years, a method of forming a surface protective layer on a circuit wiring pattern by performing exposure, development, and effect processing following application or lamination of a photosensitive insulating resin has been adopted for the above problem.
[0006]
However, such a surface protective layer made of a photosensitive insulating resin is inferior in mechanical strength as compared with a surface protective layer made of a flexible insulating film. Provided a flexible circuit board that has a high-precision opening at low cost because it is expensive and has problems such as bending parts becoming obstacles in mounting circuit parts and poor flex resistance. It has become an obstacle to doing.
[0007]
Therefore, for the fine terminal forming part, a surface protective layer is formed by a photosensitive insulating resin, and other parts, that is, parts that do not require fine openings, where mechanical strength is required, A conventional method using a flexible insulating film has been adopted for a portion where bending resistance is required.
[0008]
In this configuration, as shown in FIG. 3, the flexible circuit having the opening 34 described above except for the part that requires the fine opening 33 of the circuit wiring pattern 32 formed on the upper surface of the flexible insulating base material 31. The surface protection layer 37 is formed by adhering the photosensitive insulating film 35 with the adhesive 36, and the portion requiring the fine opening 33 is made photosensitive by laminating or applying the photosensitive insulating resin, exposure, development, and curing treatment. A surface protective layer 38 made of an insulating resin is formed.
[0009]
At this time, since the surface protective layer 38 made of the photosensitive insulating resin is formed after the surface protective layer 37 made of the flexible film is formed, the peripheral portion 39 of the surface protective layer 38 made of the photosensitive insulating resin is exposed.
[0010]
In such a configuration, since the surface protective layer 38 made of a photosensitive insulating resin is formed after the surface protective layer 37 is formed by bonding the flexible insulating film, the heating condition is 140 when the flexible insulating film is bonded. Since it is not affected by the heat of 2 ° C. × 2 hours, the flexibility of the photosensitive insulating resin can be maintained without being greatly impaired, so that it can be adopted for such a flexible circuit board.
[0011]
However, on the other hand, since the peripheral edge 39 of the surface protective layer 38 made of the photosensitive insulating resin is exposed at the outermost surface, the photosensitive insulating resin is used in a punching process for external processing, handling at the time of mounting, and the like. A part of the peripheral edge of the surface protective layer may be peeled off to become a foreign substance, which may cause problems during mounting, and may cause problems such as deterioration of environmental resistance characteristics.
[0012]
[Means for Solving the Problems]
In order to suitably solve the above-described problem, in the present invention, at least one or more flexible insulating base materials, a circuit wiring pattern formed on the flexible insulating base material, and the circuit wiring pattern In a flexible circuit board comprising a surface protective layer having an opening at a terminal forming portion and covering the circuit wiring pattern, the surface protective layer is formed on the terminal forming portion of the circuit wiring pattern with high precision and fineness. After forming a part requiring opening by lamination or application of photosensitive insulating resin, exposure, development, and curing treatment, the other part is adhered by a flexible insulating film having an opening, and the photosensitive There is provided a flexible circuit board having a surface protective layer formed so as to cover a peripheral portion of the surface protective layer made of a conductive insulating resin with the flexible insulating film.
[0013]
In order to obtain such a flexible circuit board, a step of forming a circuit wiring pattern on at least one or more flexible insulating base materials, a terminal forming portion of the circuit wiring pattern, for forming a terminal A process for forming a surface protective layer with a photosensitive insulating resin by laminating or applying a photosensitive insulating resin, exposure, development, and effect processing, and an opening for another terminal forming part in a part requiring a high-precision fine opening. A step of forming a surface protective layer by adhering a flexible insulating film on the circuit wiring pattern so as to cover a peripheral portion of the surface protective layer formed of the photosensitive insulating resin is possible. A flexible circuit board manufacturing method is employed.
[0014]
Here, in the step of forming the surface protective layer with the photosensitive insulating resin, the curing treatment following the lamination or application, exposure, and development of the photosensitive insulating resin is performed to eliminate the tackiness of the surface of the photosensitive insulating resin. After that, the flexible insulating film having an opening for a terminal forming portion is adhered onto the circuit wiring pattern so as to cover a peripheral portion of the surface protective layer formed of the photosensitive insulating resin. A method of manufacturing a flexible circuit board is also employed, in which a complete curing process is performed in the heat treatment during bonding in the step of forming the surface protective layer.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a conceptual cross-sectional view showing an embodiment of the present invention in a single-sided flexible circuit board, which is formed on the upper surface of a flexible insulating base material 1 made of a flexible insulating film such as polyimide. In addition, an epoxy-acrylic resin having a photosensitive group is formed on the upper surface of the circuit wiring pattern 2 formed by using a photofabrication etching method or the like for a conductive layer such as copper, and the like where a fine opening 3 is required. Alternatively, a surface protective layer 4 made of a photosensitive insulating resin is formed by laminating or applying a polyimide-based photosensitive insulating resin, exposure, development, and curing treatment, and a flexible insulating film 6 such as polyimide having an opening 5. Are adhered by an adhesive 7 to form a surface protective layer 8.
[0016]
At this time, since the surface protective layer 4 made of the photosensitive insulating resin is formed before the formation of the surface protective layer 8 made of the flexible film, the peripheral portion 9 of the surface protective layer 4 made of the photosensitive insulating resin is made of the flexible insulating film. Is covered with a surface protective layer 8.
[0017]
Here, the flexible circuit board is not limited to the single-sided circuit board shown in the above embodiment, but can be implemented in a double-sided or multi-layered form.
[0018]
FIG. 2 is a manufacturing process diagram of the flexible circuit board of the embodiment shown in FIG. 1. First, as shown in FIG. A circuit wiring pattern 2 is formed by etching using a photofabrication technique.
[0019]
Next, as shown in FIG. 2 (2), an epoxy-acrylic or polyimide-based photosensitive insulation having a photosensitive group is applied to a portion of the upper surface of the circuit wiring pattern 2 that requires a fine opening 3. The surface protective layer 4 made of a photosensitive insulating resin is formed by laminating or applying resin, exposure, development, and curing.
[0020]
Here, the above-described curing process following lamination or application of the photosensitive insulating resin, exposure, and development is performed in order to eliminate the tackiness of the surface of the photosensitive insulating resin, and the flexible insulating film that is subsequently implemented is cured. In the heat treatment at the time of bonding, a complete curing process is performed.
[0021]
In addition, the conditions for the curing treatment to be performed are 80 ° C. × 20 minutes, and the surface is dried by taking into account the conditions of the curing treatment to be performed later, and performing the conventional curing treatment at 140 ° C. × 2 hours. The tackiness was eliminated.
[0022]
Next, a surface protection layer 8 is formed by bonding a flexible insulating film 6 such as polyimide having openings 5 with an adhesive 7 as shown in FIG. Here, the peripheral edge portion 9 of the surface protective layer 4 made of a photosensitive insulating resin is covered with a surface protective layer 8 made of a flexible insulating film 6 as shown in the figure.
[0023]
In this process, the condition for bonding the flexible insulating film 6 is a step cure method of 140 ° C. × 2 hours followed by 120 ° C. × 30 minutes instead of the conventional 140 ° C. × 2 hours. did. In this step, the surface protective layer 4 made of a photosensitive insulating resin is completely cured.
[0024]
And although not shown in figure, after the said process, an external shape process by a metal mold | die etc. can be given and a flexible circuit board can be obtained.
[0025]
According to the manufacturing method described above, the heat treatment step of 140 ° C. × 2 hours is performed only once on the surface protective layer made of the photosensitive insulating resin.
[0026]
【The invention's effect】
According to the flexible circuit board of the present invention, in the flexible circuit board having fine and highly accurate openings, the peripheral portion of the surface protective layer made of the photosensitive insulating resin is covered with the surface protective layer made of the flexible insulating film. Therefore, part of the peripheral part of the surface protection layer by the photosensitive insulating resin is peeled off during the punching process for external processing and handling at the time of mounting, which may become a foreign object and become an obstacle during mounting. Can be prevented.
[0027]
In addition, according to the manufacturing method, it is possible to minimize the thermal influence on the photosensitive insulating resin, so that it becomes possible to adopt a surface protective layer and a flexible insulating film made of the photosensitive insulating resin in the right place, It is possible to provide a flexible circuit board having a highly accurate opening at low cost while maintaining environmental resistance characteristics.
[Brief description of the drawings]
FIG. 1 is a conceptual cross-sectional configuration diagram of a flexible circuit board according to an embodiment of the present invention.
FIG. 2 is a manufacturing process diagram of a flexible circuit board according to an embodiment of the present invention.
FIG. 3 is a conceptual cross-sectional configuration diagram showing a conventional flexible circuit board.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Flexible insulating base material 2 Circuit wiring pattern 3 Fine opening 4 Surface protective layer 5 by photosensitive insulating resin Opening 6 Flexible insulating film 7 Adhesive 8 Surface protective layer 9 Perimeter of surface protective layer by photosensitive insulating resin Part

Claims (3)

At least one or more flexible insulating base materials, a circuit wiring pattern formed on the flexible insulating base material, and an opening at a terminal forming portion of the circuit wiring pattern and covering the circuit wiring pattern In the flexible circuit board formed of the formed surface protective layer, the surface protective layer is a terminal forming portion of the circuit wiring pattern, and a photosensitive insulating resin laminate or a portion of the portion requiring a highly precise fine opening. After coating, exposure, development, and curing, the other part is adhered by a flexible insulating film having an opening, and the periphery of the surface protective layer is coated with a photosensitive insulating resin. A flexible circuit board having a surface protective layer formed so as to be covered with a flexible insulating film. A step of forming a circuit wiring pattern on at least one layer of a flexible insulating base material, a photosensitive insulating material at a terminal forming portion of the circuit wiring pattern that requires a high-precision fine opening for terminal formation. The step of forming a surface protective layer with a photosensitive insulating resin by laminating or coating resin, exposure, development, and curing treatment, and a flexible insulating film having openings for other terminal forming portions are formed with the photosensitive insulating resin. A method for producing a flexible circuit board, comprising a step of forming a surface protective layer by adhering to the circuit wiring pattern so as to cover a peripheral portion of the formed surface protective layer. In the surface protective layer forming step with the photosensitive insulating resin, the curing treatment following the lamination or application of the photosensitive insulating resin, exposure, and development is performed in order to eliminate tackiness of the surface of the photosensitive insulating resin, and thereafter The surface protective layer is bonded by adhering the flexible insulating film having an opening for a terminal forming portion on the circuit wiring pattern so as to cover a peripheral portion of the surface protective layer formed of the photosensitive insulating resin. The method for producing a flexible circuit board according to claim 2, wherein a complete curing process is performed in the heat treatment during bonding in the forming step.

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