JPH07106723A - Flexible printed circuit board and method for mounting component - Google Patents

Abstract

PURPOSE:To provide a flexible printed circuit board and its mounting method, in which an ultraviolet-ray curing resin is cured easily in a part mounted step. CONSTITUTION:In a flexible printed circuit board 1, a base film 2, an electrolytic copper 4 for forming a circuit in a given shape, and a cover-lay film 6 are formed in a body with adhesives 3 and 5 in between. In the flexible printed circuit board 1, the base film 2, the cover-lay film 6, and the adhesives 3 and 5 are made of each given material with ultraviolet-ray transmittance of 5% or above for light ranging from 350 to 400nm in wave length.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is excellent in ultraviolet light transmittance,
TECHNICAL FIELD The present invention relates to a flexible printed wiring board (FPC) configured to easily cure an ultraviolet curable resin used for molding an electronic device and the like, and a component mounting method.

[0002]

2. Description of the Related Art The use of FPC as an integrated wiring material is expanding with the miniaturization and high functionality of electronic equipment.
Then, in order to improve the reliability of mounting the electronic device on the FPC and connecting to another printed circuit board, the connection portion is molded with an ultraviolet curable resin to improve the heat stress resistance, or further the ultraviolet curable resin is used. There is known a technique in which the connection portion is adhered by the method and the contact pressure of the connection portion is increased by the curing shrinkage.

FIG. 3 is a sectional view schematically showing a state in which components (electronic devices) are mounted on the FPC. As shown in the figure, in FPC01, after the pattern of electrolytic copper 04 is formed on the base film 02 via the first adhesive layer 03, the second adhesive layer 05 and the cover layer are covered so as to cover other than the connection portion. The film 06 is provided. When the component (electronic device) 07 is mounted on the FPC 01, the UV curable resin 08 is applied between the FPC 01 and the component 07, and the UV curable resin 0 is irradiated by UV irradiation.
Allow 8 to cure.

[0004]

By the way, since polyimide, which is a typical constituent material of FPC, has an ultraviolet transmittance of almost zero, conventionally, when curing an ultraviolet curable resin on an FPC, an ultraviolet light is emitted. It was necessary to irradiate the resin directly.

Therefore, the ultraviolet curable resin 0 shown in FIG.
In the case of curing No. 8, it is necessary to irradiate the ultraviolet light through the gap between the FPC01 and the component 07, but the ultraviolet light is cured by the ultraviolet light due to the shape of the molding target (component 07) or the assembly space constraint. The space for directly irradiating the resin 08 may become extremely small. In this case, it is necessary to extend the curing time or significantly increase the irradiation light amount, which causes a problem that work efficiency is reduced and variations in resin curing characteristics occur.

In view of such circumstances, an object of the present invention is to
A flexible printed wiring board and a component mounting method that facilitate curing of an ultraviolet curable resin during component mounting.

[0007]

In a flexible printed wiring board according to the present invention which achieves the above object, a base resin film, a metal foil pattern forming a circuit having a predetermined shape, and a coverlay film are bonded via an adhesive. In the integrated flexible printed wiring board, the base resin film, the coverlay film, and the adhesive are made of a material having an ultraviolet transmittance of 5% or more at a light wavelength of 350 nm to 400 nm. .

Further, in the method of mounting a component of the present invention, when the component is mounted on the flexible printed wiring board by using an ultraviolet curable resin, the component is irradiated with ultraviolet light to temporarily adhere the component to the flexible printed wiring board. It is characterized in that the ultraviolet curable resin is cured by irradiating ultraviolet light from the back surface side of the wiring board.

According to the method of the present invention, if the base resin film, the coverlay film and the adhesive are FPCs using a material having an ultraviolet transmittance of 5% or more for light having a wavelength of 350 to 400 nm, the FPC is used. This has been achieved based on the finding that sufficient ultraviolet irradiation characteristics can be obtained even with ultraviolet irradiation.

A base resin film used in the present invention,
The materials of the coverlay film and the adhesive may be those satisfying the above-mentioned conditions, but as the base resin film and the coverlay film, polyetherimide (PEI), polyethersulfone (PES), polyethylene Phthalate, polyetheretherketone (PEEK), polycarbonate (PC), polyethylene terephthalate (PET), etc. are suitable. As the adhesive, epoxy-based, acrylic-based, urethane-based,
Nylon type or the like can be used, and the flame retardant compounding type that has been conventionally used can be used within a range in which the ultraviolet transmittance can be maintained within the above range.

[0011]

EXAMPLES The present invention will be described below based on examples.

(Embodiment) FIG. 1 is a sectional view showing a method of mounting components using a flexible printed wiring board according to an embodiment. As shown in the figure, after forming a pattern of electrolytic copper 4 on the base film 2 via the first adhesive layer 3, the FPC 1 includes the second adhesive layer 5 and the cover layer so as to cover other than the connection portion. The film 6 is provided.

The base film 2 has a thickness of 2
5μm PEI film (Mitsubishi resin; wavelength 350nm
The first adhesive layer 3 using the ultraviolet transmittance of 17%)
Is formed of an epoxy / urethane adhesive (UV transmittance of 15% at a wavelength of 350 nm), the pattern of the electrolytic copper 4 is formed of an electrolytic copper foil of 35 μm (manufactured by Nippon Denki Co., Ltd.), the second adhesive layer 5 and the coverlay. As the film 6, a PEI film (made by Mitsubishi Plastics) coated with an epoxy / urethane adhesive (UV transmittance of 15% at a wavelength of 350 nm)
Was used. The UV transmittance of the FPC1 of this example for light having a wavelength of 350 nm was 5%.

A component (electronic device) 7 is attached to the FPC 1.
In the case of mounting, the acrylate-based UV curable resin 8 is applied between the FPC 1 and the component 7, and first, the UV curable resin 8 is temporarily adhered by irradiating the UV light from between the FPC 1 and the component 7, Further, the ultraviolet curable resin 8 is sufficiently cured by irradiating ultraviolet rays from the back surface side (base film 2 side) of the FPC 1.

(Test Example) As shown in FIG. 2, the coverlay film 6 of the FPC sample 1A having the same structure as the above-mentioned embodiment.
Apply acrylate UV curable resin 9 on top and
After irradiating with ultraviolet light of 300 mW / cm ² from the back surface side of No. 1 for 5 minutes, the surface hardness of the ultraviolet curable resin 9 was measured by the Vickus hardness meter to examine the degree of curing.

Comparative Example In a comparative example, a polyimide film having a thickness of 25 μm as a base film (manufactured by Toray Dupont; ultraviolet transmittance at a wavelength of 350 nm is 1% or less)
And the first adhesive layer is an epoxy / nitrile rubber compounding adhesive (ultraviolet transmittance of 1% or less at a wavelength of 350 nm)
The electrolytic copper pattern is formed by an electrolytic copper foil of 35 μm (manufactured by Nippon Denshoku Co., Ltd.), and as the second adhesive layer and the coverlay film, an epoxy / nitrile rubber compound adhesive (UV transmittance of 1% at a wavelength of 350 nm is 1%. FP using a polyimide film (manufactured by Toray DuPont) coated with the following)
A C sample was used. The ultraviolet transmittance of the entire FPC sample was 1% or less at a wavelength of 350 nm.

On the coverlay film of this FPC sample, an acrylate-based UV curable resin was applied in the same manner as in the test example, and 300 mW / cm ² of UV light was irradiated from the back side of the FCP for 5 minutes, and then the UV curable resin was applied. The surface hardness was measured with a Vickus hardness tester to examine the degree of curing.

The results of the test examples and comparative examples are shown in Table 1. As shown in Table 1, in the test example using the FPC having the same configuration as that of this example, the surface hardness of the ultraviolet curable resin was 7H, and the degree of curing of the resin was sufficient, but in the comparative example, the ultraviolet curable was used. The surface hardness of the resin was 2H, and the resin was in a semi-cured state.

From the above results, it was found that when the FPC of the present invention is used, sufficient curing characteristics can be obtained even when the ultraviolet curable resin is cured by irradiating it with ultraviolet light from the back surface side.

[0020]

[Table 1]

[0021]

As described above, the F according to the present invention
Since the PC is composed of a base resin film, a coverlay film, and an adhesive, using a material having an ultraviolet transmittance of 5% or more in a light wavelength of 350 nm to 400 nm,
When a component or the like is molded or adhered to the FPC by using an ultraviolet curable resin, the ultraviolet curing can be performed through the FPC, and it is possible to prevent a decrease in work efficiency in mounting the component and a variation in curing characteristics.

[Brief description of drawings]

FIG. 1 is a sectional view showing a state in which components are mounted on an FPC according to an embodiment of the present invention.

FIG. 2 is a sectional view illustrating a test example of the present invention.

FIG. 3 is a cross-sectional view showing a state in which components are mounted on an FPC according to a conventional technique.

[Explanation of symbols]

 1,1A FPC 2 Base film 3 First adhesive layer 4 Electrolytic copper 5 Second adhesive layer 6 Coverlay film 7 Parts 8, 9 UV curable resin

Claims (2)

[Claims] 1. A flexible printed wiring board in which a base resin film, a metal foil pattern for forming a circuit having a predetermined shape, and a coverlay film are integrated via an adhesive, wherein the base resin film and the coverlay film are provided. And the adhesive with a light wavelength of 350 nm to 40 nm
A flexible printed wiring board comprising a material having a UV transmittance of 5% or more at 0 nm. 2. When mounting a component on a flexible printed wiring board by using an ultraviolet curable resin, after irradiating ultraviolet light from the component side to temporarily adhere the component, ultraviolet light is applied from the back surface side of the flexible printed wiring board. A method for mounting a component, which comprises irradiating to cure the ultraviolet curable resin.