JPH06350210A - Flexible printed wiring board - Google Patents

Abstract

PURPOSE:To provide a colored FPC excellent in mechanical strength, dimensional stability, and heat resistance while exhibiting shading properties, identifiableness, and decorativeness. CONSTITUTION:The flexible printed wiring board comprises a heat resistant film, i.e., a dielectric board, and a wiring pattern of conductive metal layer formed on the surface of the film, wherein the dielectric board and/or a coverlay is composed of a colored para position aromatic polyamide film containing a dye or a pigment by 1wt.% or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible printed wiring board, and more specifically, it has excellent mechanical properties, heat resistance and dimensional stability, and is characterized by distinctiveness, light-shielding properties, decorative properties and the like. The present invention relates to a flexible printed wiring board (FPC).

[0002]

2. Description of the Related Art In recent years, electronic devices have become smaller and lighter,
The demand for FPCs that are lighter in weight, occupy a smaller area than conventional rigid types, and that allow free three-dimensional wiring and wiring simplification is rapidly increasing. Further, as the uses and usage forms of the FPC have been diversified, various performances have been required.

As a conventional FPC, a polyimide film, polyester film or the like is used as a base material, copper foil is adhered to these long sheets, pattern etching is performed, and a cover lay is adhered. There is. FPCs are used for wiring, component mounting, etc. in printers, cameras, VTRs, optical disc devices, and the like. Of these, when used in optical systems such as cameras, VTR cameras, and laser discs, the reflected light or transmitted light on the FPC surface may interfere with the functions of these devices. Measures have been taken such as applying a matte paint to the surface. However, the matte coating has insufficient flexing resistance and abrasion resistance, and has a drawback that reliability is impaired.

On the other hand, while the number of FPCs used is increasing, there is a need for color coding for distinguishing various types of FPCs, adhesion confirmation of coverlays, etc., and FPCs colored for decoration. FPC could not meet such demand.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a colored FPC which is excellent in mechanical properties, heat resistance, dimensional stability, light shielding properties, distinctiveness, and decorative properties.

[0006]

Means for Solving the Problems As a result of intensive studies for achieving the above object, the present inventors have used a specific para-oriented aromatic polyamide colored film for one or both of an insulating substrate and a coverlay. As a result, they have found that these requirements can be met, leading to the present invention.

That is, according to the present invention, in a flexible printed wiring board in which a heat resistant film is used as an insulating substrate, and a wiring pattern made of a conductive metal layer is formed on the surface of the film, one or both of the insulating substrate and the coverlay is formed. The flexible printed wiring board is a para-oriented aromatic polyamide film containing 1% by weight or more of a dye.

In the present invention, it is necessary to use a heat resistant film as the insulating substrate. As such a heat-resistant film, a film made of a heat-resistant polymer having a melting point of 300 ° C. or higher such as aromatic polyamide, aromatic polyimide, or aromatic polyester is preferably used. As the heat resistant film, para-oriented aromatic polyamide having excellent mechanical properties and dimensional accuracy is preferably used. The para-oriented aromatic polyamide is substantially composed of units selected from the group consisting of the following constitutional units.

-NH-Ar1-NH- (1) -CO-Ar2-CO- (2) -NH-Ar3-CO- (3) Here, Ar1, Ar2, and Ar3 each represent at least one aromatic ring. And (1) and (2) are substantially equimolar when present in the polymer, and Ar 1, Ar 2 and Ar 3 are each a para-oriented group. preferable.

Here, the para-orientation type means that the binding direction of the main chain in the aromatic ring is located at the para position, or the binding directions of the main chains at both ends are coaxial in the residue consisting of two or more aromatic rings. Or it means parallel. As a typical example of such a divalent aromatic group, chemical formula 1 and the like can be mentioned.

[0011]

[Chemical 1]

Where X is --O--, --CH _2- , --S
_{O 2 -, - S -,} - CO- selected from among. Further, a part of hydrogen atoms of these aromatic rings may be substituted with a halogen group, a nitro group, a sulfone group, an alkyl group, an alkoxy group or the like. Ar1, Ar2 and Ar3 may all be two or more kinds, and may be the same or different from each other.

The para-oriented aromatic polyamide is obtained, for example, by casting an optically anisotropic dope using sulfuric acid or the like as a solvent on a supporting surface and adding the dope to the isotropic layer by absorbing moisture and / or heating. A film can be produced by a method in which after coagulation and washing, if necessary, uniaxial or biaxial stretching is performed, and then drying is performed while controlling shrinkage. The thickness of the heat resistant film used in the present invention is preferably 9 to 50 μm, more preferably 9 to 25 μm.

The FPC of the present invention usually has a structure in which a coverlay is adhered on a wiring pattern with an adhesive. However, depending on the required performance, a solder resist may be used for circuit protection without using a coverlay. When the coverlay is used, a heat resistant film is used as the material for the coverlay, and preferably a para-oriented aromatic polyamide film is used.

In the present invention, it is necessary to use a para-oriented aromatic polyamide film containing 1% by weight or more of a dye or a pigment on one or both of the insulating substrate and the coverlay. As the dye used for coloring, an anionic dye, a cationic dye, a disperse dye, a direct dye and the like can be used, and among these, a dye having high heat resistance is preferably used. As the pigment, synthetic organic pigments, synthetic and inorganic pigments are used. As a method of coloring, it is possible to use a method of adding a dye or a pigment to a film-forming solution of para-oriented aromatic polyamide, or a method of contacting a liquid containing a dye to a wet film before drying or a film after drying to dye the film. However, from the viewpoints of processability, color fastness, film performance, etc., a method of contacting a liquid containing a dye with a wet film before drying, followed by drying and heat treatment is preferably used.

The content of dye or pigment is FPC.
1% by weight or more is required to obtain the above coloring effect, but it is preferably 10% by weight or less in order not to impair the mechanical performance, electrical performance, heat resistance and the like of the film. The tensile elastic modulus of the colored para-oriented aromatic polyamide film is preferably 600 Kg / mm ² or more,
0 kg / mm ² or more is more preferable. Also, tensile elongation 1
0% or more is preferable, and 20% or more is more preferable. The volume resistivity of the film is preferably 1 × 10 10 Ω · cm or more in order to maintain insulation between the patterns as the FPC and prevent deterioration of the characteristics due to migration.
Therefore, inclusion of conductive particles such as carbon for coloring the film used in the present invention should be avoided. On the other hand, the colored film needs to withstand heating during soldering as FPC, and the heat shrinkage at 250 ° C. is preferably 1% or less, more preferably 0.2% or less.

In the present invention, the para-oriented aromatic polyamide film colored according to the required performance can be used for the insulating substrate only, the coverlay only, or both the insulating substrate and the coverlay. When used on only one side, a heat resistant film which is not colored on the other side can be used. Since the natural color of the para-oriented aromatic polyamide film is yellow, it is necessary to color it with a dye or pigment other than yellow in order to distinguish it from the natural color. In particular, in the use of light shielding, it is effective to color in black in order to prevent light transmission.

The surface of the film may be smooth and mirror-like with a high reflectance depending on the intended use, but for the purpose of blocking light, a rough surface having a specific optical property is provided in order to prevent reflected light. It is also preferable to make it planar. In such a case, it is most preferable to use a black film having a specular gloss Gs (60 °) of 10% or less and a Y value of 10% or less. Here, the specular gloss Gs (60 °) is JIS
It is a value measured according to Z8741 and Gs (60
If the value of (°) exceeds 10%, the effect of suppressing the reflected light becomes insufficient. Gs (60 °) is, for example, a digital variable angle gloss meter U
It can be measured using GV-4D (manufactured by Suga Test Instruments). On the other hand, the Y value is the Y value of the tristimulus values XYZ relating to the color specified in JIS Z8701, and can be measured using, for example, a colorimetric color difference meter (Suga tester). By setting the Y value to 10% or less, a sufficient light shielding effect can be obtained.

The film having such specific optical characteristics can be produced, for example, by the following method. (1) In the production of a para-oriented aromatic polyamide film, a wet film before drying is brought into contact with a liquid containing a black dye to be dyed, and a satin surface is brought into contact pressure before drying, followed by drying and heat treatment to obtain a film. To manufacture. (2) The wet film before drying is contacted with a liquid containing a black dye, dyed, dried, and heat-treated to blow a sand having a maximum diameter of 0.05 to 0.7 mm, and blast treatment is applied. The surface is roughened by carrying out.

The FPC of the present invention uses the above heat-resistant film as an insulating substrate and has a wiring pattern made of a conductive metal layer laminated on one or both sides of the film.
Usually, it is manufactured by laminating a metal layer on a heat-resistant film and then etching it into a wiring pattern. here,
As the conductive metal, copper, aluminum, an alloy containing iron-nickel as a main component, tantalum, molybdenum, or the like can be used.

The heat-resistant film and the metal are usually laminated through an adhesive such as an epoxy-based adhesive. However, use should be made of a metal layer directly formed on the heat-resistant film by vapor deposition, sputtering, plating or the like. You can also Also,
The wiring pattern can be formed by screen printing using a conductive paste such as copper or silver. F of the present invention
The PC may be a single-sided type in which a metal layer is formed on one side of an insulating substrate, or a double-sided type in which metal layers are formed on both sides. Also, a so-called multi-layer substrate having two or more insulating substrates can be used.

[0022]

EXAMPLES Examples will be shown below, but these Examples illustrate the present invention and do not limit the present invention. The film thickness was measured with a dial gauge having a measuring surface with a diameter of 2 mm. Toughness and modulus are
A sample having a size of 100 mm × 10 mm was measured using a constant-speed extension type strong elongation tester at a measurement length of 30 mm and a pulling rate of 30 mm / min. The volume resistivity is calculated based on the ultra insulation meter SM-
10E (measured by Toa Denpa Kogyo Co., Ltd., specular gloss Gs (60 °) was measured using a digital variable angle gloss meter UGV-4D (manufactured by Suga Test Instruments Co., Ltd.) Y value was measured by a colorimeter (color computer SM. -4, manufactured by Suga Test Instruments Co., Ltd.).

[0023]

Example 1 As an insulating substrate and a coverlay, black polyparaphenylene terephthalamide (hereinafter, referred to as PP
An example using a film called TA) is shown. Concentration 99.5
PPTA of ηinh = 6.1 was dissolved in 60% concentrated sulfuric acid at 60 ° C. to prepare a stock solution having a polymer concentration of 12%. The stock solution was degassed under vacuum while maintaining it at 60 ° C. 0.4m from the tank through the filter and then by the gear pump
From a T-die having a slit of mx 700 mm, cast the dope on a belt made of tantalum, and the relative humidity is about 5
%, The air was blown at a temperature of about 105 ° C., the casting dope was optically isotropic, and it was introduced into water at 5 ° C. together with the belt to be solidified. Then, the coagulated film was peeled off from the belt and washed by running in warm water of about 30 ° C., then in 0.5% NaOH aqueous solution, and further in water at room temperature. 5% by weight of black dye (nylon black GL) on the washed film
After contacting with the aqueous solution for 10 minutes, washing with water, roll stretching 1.15 times in the machine direction in the longitudinal direction, then stretching in the transverse direction by 1.20 times with a tenter, further drying at 260 ° C. for a fixed length, and heat treatment at 400 ° C. After the removal, one surface was blasted using a 0.1 mm sand. The film obtained has a thickness of 1
2 micron, heat shrinkage (250 ° C) 0.2%, strength 32
Kg / mm ^2, tensile elastic modulus 1170Kg / mm ^2, tensile elongation of 21%, the volume resistivity of 3.5 × 1012Ω · cm, specular gloss Gs (60 °) 5.5%, in Y value 7.2% there were. An epoxy adhesive was applied to the non-blasted surface of this film, and then an electrolytic copper foil with a thickness of 35 μm was laminated and cured to adhere the film. Next, using thermosetting silk screen printing ink as an etching resist,
A wiring pattern was created by etching with a cupric chloride / hydrochloric acid aqueous solution. On this, a cover lay made by applying an epoxy adhesive to the same film was attached and an FPC was made.

This FPC had a light-shielding property suitable for use in an optical system such as a camera. No problems such as deformation occurred in the solder heat resistance test (260 ° C., 5 seconds). Even if the FPC surface was rubbed with a metal, there was no change.

[0025]

Example 2 PPTA was dissolved in concentrated sulfuric acid, cast, coagulated and dyed in the same manner as in Example 1, and then pressure-pressed with a # 800 satin roll, followed by 1.15 times roll stretching in the longitudinal direction, and then The film was stretched in the transverse direction by a 1.20 times tenter, dried at a constant length of 260 ° C., and heat-treated at 400 ° C. to obtain a colored film. The obtained film has a thickness of 12 μm, a heat shrinkage rate (250 ° C.) of 0.2%, and a strength of 34 kg / m.
m ² , tensile modulus 1130 kg / mm ² , tensile elongation 32
%, Volume resistivity 8.25 × 10 12 Ω · cm, specular gloss Gs (60 °) 8.8%, and Y value 5.4%. An FPC was manufactured in the same manner as in Example 1.

This FPC had a light-shielding property suitable for use in an optical system such as a camera. No problems such as deformation occurred in the solder heat resistance test (260 ° C., 5 seconds). Even if the FPC surface was rubbed with a metal, there was no change.

[0027]

[Comparative Example 1] A 25 μm thick polyimide film (Kapton 100H) was used as an insulating substrate and a coverlay to prepare an FPC in the same manner as in Example 1, and a black matte coating was applied on it to deluster it. Processed. This FPC had a light-shielding property suitable for being used in an optical system such as a camera, but when the surface of the FPC was rubbed with a metal, the paint was peeled off and the abrasion resistance was insufficient.

[0028]

Example 3 PPTA was dissolved, cast and coagulated in concentrated sulfuric acid in the same manner as in Example 1 and then contacted with a 1.5% by weight aqueous solution of a blue dye (Turkis blue 3G) for 10 minutes,
Roll stretched 1.05 times in the machine direction and then 1.
Stretching with a ten-fold tenter and drying at 260 ° C for a fixed length,
It heat-processed at 400 degreeC and the blue film was obtained. The film obtained has a thickness of 12 microns and a heat shrinkage rate (250 ° C).
0.15%, strength 38 kg / mm ² , tensile modulus 108
0 kg / mm ² , tensile elongation 38%, volume resistivity 1.2 ×
It was 1013 Ω · cm. Blue FP as in Example 1
C was produced.

This FPC was tested for solder heat resistance (26
No problems such as deformation occurred at 0 ° C. for 5 seconds.

[0030]

[Comparative Example 1] A blue FPC was used in the same manner as in Example 1 except that a 25 μm thick polyethylene-terephthalate film colored in blue was used as an insulating substrate and a coverlay.
It was created. This FPC is solder heat resistance test (260
It was significantly deformed at 5 ° C for 5 seconds, and it was impossible to mount the component by soldering.

[0031]

The FPC of the present invention is excellent in mechanical performance and dimensional accuracy and is colored in an arbitrary color. Therefore, it is possible to identify various types of FPCs depending on the application and also have a function of decoration. You can also Further, when used in an optical system such as a camera, a VTR camera, an optical disc, a halo due to reflected light can be prevented. Colored FP of the present invention
C is characterized in that such a function can be imparted without impairing heat resistance and durability, and can be mounted by soldering components by flow or reflow, and can be used for bending parts and bending parts. It is possible without problems.

Claims (2)

[Claims] 1. A flexible printed wiring board having a heat-resistant film as an insulating substrate and a wiring pattern made of a conductive metal layer formed on the surface of the film, wherein one or both of the insulating substrate and the coverlay is a dye or A flexible printed wiring board, which is a para-oriented aromatic polyamide film containing 1% by weight or more of a pigment. 2. A para-oriented aromatic polyamide film,
Specular gloss Gs (60 °) is 10% or less, Y value is 10%
The flexible printed wiring board according to claim 1, which is the following black film.