JP2002109967A - Flexing resistant flexible flat cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexing resistant flexible flat cable having high flexing resistant property without making the thickness of a plastic film with adhesives, or a conductor thin. SOLUTION: A high flexing resistance property is obtained by making the lengthwise coefficient of elasticity of adhesive plastic films 22, 23 of FFC 20 not less than 209 kg/mm2 which is unified by laminating a group of conductors 21a, formed by arranging at least more than one pieces of conduction body 21 in parallel, with two sheets of adhesive plastic films 22, 23 with insulation property.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible flat cable having flexibility.

[0002]

2. Description of the Related Art A flexible flat cable (hereinafter referred to as "FF") used for wiring a movable part of an electric / electronic device.
C ". ) Is a thin tape-shaped electric wire having a thickness of 0.1 to 0.3 mm.

FIG. 3 is a conceptual diagram showing an apparatus for manufacturing an FFC, and FIG. 4 is a view of the apparatus shown in FIG.

[0004] The FFC 1 is composed of two plastic films 3 with an adhesive having insulating properties on both sides (up and down in FIG. 3) of a conductor group 2a in which one to several tens of conductors 2 are arranged in parallel.
It is manufactured by laminating with a pair of heat rolls 5 and 6 sandwiched by 4. Reference numeral 7 denotes a press die for forming an FFC end 8 by punching a part of the plastic film 3 with an adhesive at a predetermined interval. 9 is a plastic film of the plastic film 3 with an adhesive. This FFC
1 is cut at the FFC end 8 and a reinforcing plate is provided to produce a product.

The FFC 1 has been used as a jumper line (fixed wiring) between circuits by utilizing its flexibility.

FIG. 5 (a) shows an FF using pure Sn or a solder-plated rectangular conductor (pure copper such as TPC) as a representative product.
FIG. 5B is a side view showing the basic structure of C, and FIG.
It is a BB sectional view taken on the line of (a).

In this FFC 10, a plurality of rectangular conductors 2 are arranged in parallel, two plastic films 9 are adhered to both surfaces (upper and lower surfaces in the figure) with an adhesive 11, and conductors 2 at both end surfaces are provided.
The reinforcing plate 12 is provided on the back surface of the exposed portion.

In recent years, the evaluation of flex life characteristics of FFCs has been advanced, and the number of cases where the FFC is used as a flexible printed wiring board (hereinafter, referred to as FPC) as a movable portion wiring member of electric / electronic devices is increasing. In particular, print head wiring and CD-RO for an ink jet printer for a personal computer (hereinafter referred to as "PC") aiming at low price.
M, in addition, the number of cases where it is used as an optical pickup unit wiring of a car navigation system, a laser disk player, or the like is increasing rapidly.

Today, the conductor thickness is 22 μm × pitch 0.5
The development and mass production of mm high-definition products are progressing, and application to the latest electronic devices such as optical pickup wiring for DVDs (digital video disc players) is also progressing.

[0010] Ink jet printer print head and C
By moving the optical pickup section of the D-ROM,
The FFC used for the movable part is repeatedly bent. At present, in the case of printer print head wiring, the flex life Nf is 5
× 10 ⁶ to 1 × 10 ⁷ times (bending radius: 8 to 10 mm), and in the case of wiring of a pickup section of a CD-ROM or DVD having a narrow internal space of a device, the bending life Nf is 1 × 10 ⁵ to 1 ×.
10 ⁶ times (bending radius 3 to 5 mm) is required.

[0011] The bending resistance of the JIS is close to that of the actual machine.
It is evaluated by a repeated sliding and bending test according to C5016.

FIG. 6 is a conceptual diagram of a repetitive sliding and bending test apparatus, and FIG. 7 is a partially enlarged view of a bent portion of an FFC repeatedly tested by the apparatus shown in FIG.

In this test apparatus 13, two FFCs 10 are bent into a U-shape and set (FIG. 7), and one end of each of the two FFCs 10 is fixed between two opposing fixing plates 14 by sample fixing brackets 15, respectively. And the other end of the FFC 10 (center in the figure)
Is fixed to the drive plate 16 and the FFC 1
By repeatedly sliding 0, the fatigue life until the conductor 2 of the FFC 10 is disconnected is evaluated.
Reference numeral 17 denotes a disconnection detecting device.

[0014]

By the way, it is already known that the bending resistance of an FFC can be improved by reducing the thickness of a plastic film with an adhesive having an insulating property or a rectangular copper wire.

However, in the above-mentioned prior art, the cost is increased and the allowable current is reduced by making the conductor thin.

By reducing the thickness of the plastic film provided with the adhesive, the withstand voltage characteristics are reduced.

There was a problem that

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a flexible flat cable having high bending resistance without reducing the thickness of a plastic film with an adhesive or a conductor. is there.

[0019]

In order to achieve the above object, a flexible flat cable according to the present invention is provided by arranging at least one conductor in parallel and laminating it with two insulating plastic films with an adhesive. In the flexible flat cable integrated with the adhesive, the longitudinal elastic modulus of the plastic film with the adhesive is 209 kg.
/ Mm ² or more.

In addition to the above configuration, the flexible flat cable according to the present invention has a 180 ° peel strength between the adhesive of the plastic film with the adhesive and the conductor of 1.0.
It is preferably at least kg / cm.

In addition to the above structure, the flexible flat cable according to the present invention has a conductor having an elongation of 25% or more, a tensile strength of 25 kg / mm ² or more and less than 30 kg / mm ² , and a 0.2% proof stress of 15 kg / mm 2. ² or more 20kg / m
It is preferable to use a flat rectangular pure copper wire of less than m ² .

Here, the bending resistance characteristics of the conductor alone are improved as the tensile strength, 0.2% proof stress and elongation characteristics are higher, and as the added bending strain is smaller, the bending resistance is improved.

Here, the amount of bending strain applied to the surface of the conductor when the FFC is bent is given geometrically by Equation 1.

[0024]

(Equation 1)

Where, ε: bending strain (%) h _c : thickness of conductor R: bending radius of the center of FFC Therefore, in order to improve the bending resistance of the conductor of FFC, the curvature of FFC is obtained from equation (1). It can be seen that the radius R should be increased. In order to further increase the radius of curvature R of the FFC, it is effective to improve the elasticity of the conductor, the film with the adhesive, and the FFC itself.

Therefore, the present invention proposes the following two means for the purpose of improving the bending resistance of the FFC.

1) The longitudinal elastic modulus of the plastic film with an adhesive is increased in the longitudinal direction.

2) Mechanical properties of the conductor (tensile strength, 0.2%
Strength and elongation).

More specifically, the longitudinal elastic modulus of the FFC-coated film is 209 kg / mm ² or more, and the flat copper wire has an elongation of 25% or more and a tensile strength of 25 kg / mm ² or more and less than 30 kg / mm ^2. , 0.2% proof stress 15kg / m
m ² or more and less than 20 kg / mm ² .

As described above, the bending resistance of the FFC is greatly improved.

In the past, a conventional example in which the longitudinal elastic modulus of the adhesive in the longitudinal direction was increased to improve the bending life of the FFC (Japanese Patent Laid-Open No.
161938). The FFC uses a plastic film with an adhesive formed of a plastic film, an adhesive, and an anchor coat (thickness of several μm) for fastening the plastic film and the adhesive as shown in FIG. 8 in addition to the conductor. I have.

FIG. 8 is a sectional view taken along line CC of FIG.

To increase the elasticity of the FFC 1, the adhesive 11
It is not sufficient to simply increase the longitudinal elastic modulus of the plastic film 3, and it is necessary to increase the longitudinal elastic modulus of the entire plastic films 3 and 4 with an adhesive. Plastic film with adhesive 3,
4 Overall longitudinal modulus (E) is given by the composite rule. The longitudinal elastic modulus (E) of the entire plastic films 3 and 4 with an adhesive is represented by Formula 2.

[0034]

(Equation 2)

Here, E _FIL : the longitudinal elastic modulus of the plastic film 9 E _AC : the longitudinal elastic modulus of the anchor coat 18 E _AD : the longitudinal elastic modulus of the adhesive 11 t _FIL : the thickness of the plastic film 9 t _AC : the anchor coat 18 Thickness t _AD : thickness of adhesive 11 T: thickness of plastic films 3 and 4 with adhesive (t
To increase the longitudinal elastic modulus of _FIL + t _AC + t _AD) with adhesive from the equation (2) plastic films 3 and 4, it is seen that may increase the longitudinal elastic modulus of the plastic film 9. Conversely, even if only the longitudinal elastic modulus of the adhesive 11 is increased, if the longitudinal elastic modulus of the plastic film 9 is low, the overall longitudinal elastic modulus of the plastic films 3 and 4 with the adhesive decreases as a result. However, an FFC having high bending characteristics cannot be obtained.

The conductor has a tensile strength of 35 kg / mm ²
As described above, a conventional example in which the elongation of the FFC is improved by increasing the elongation to 7% or more (Japanese Patent Laid-Open No. 11-11107).
No. 0 publication).

However, in this conventional example, the FFC is often used by being bent, and when the conductor has an elongation of 7%, the conductor may be broken when bent.

In order to avoid such a problem, at present, FF
Elongation is given to the C conductor empirically by about 20% or more. As a result, when the conductor is made of pure copper (TPC or OFC), its tensile strength is 20 to 30 kg / mm ² , 0.2
The% yield strength is only 10 to ²⁰ kg / mm ² . The conductor has an elongation of about 20% and a tensile strength of 35 kg /
If more than mm ^{2 is} given, copper must be alloyed.

However, the alloying of copper causes a problem that the electric conductivity is remarkably reduced.

Therefore, the present inventors have proposed an FFC using a pure copper-based (TPC or OFC) conductor having high elongation characteristics, high tensile strength and high 0.2% proof stress, and high conductivity.

[0041]

Embodiments of the present invention will be described below.

The flexible flat cable according to the present invention is a flexible flat cable in which at least one conductor is arranged in parallel, laminated with two insulating plastic films having an adhesive and integrated. The longitudinal elastic modulus of the plastic film with the agent is 209 kg / mm ² or more. 180 ° between adhesive and conductor of plastic film with adhesive
The peel strength is preferably 1.0 kg / cm or more, and the conductor has an elongation of 25% or more and a tensile strength of 25 kg.
/ Mm less than ^2, 0.2% proof stress 15 kg / mm ² or more 2
It is preferable to use a rectangular pure copper wire of less than 0 kg / mm ² .

With this configuration, the bending resistance of the FFC is greatly improved.

[0044]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a plan view showing an embodiment of the flexible flat cable according to the present invention, and FIG.
5 is a view in the direction of arrow D of the device shown in FIG. The same members as those of the conventional example shown in FIG.

The FFC 20 is formed by laminating a conductor group 21a in which a plurality of conductors 21 are arranged in parallel and two plastic films 22 and 23 having an insulating property with an adhesive by heating rolls 5 and 6.

The specifications and flex life evaluation conditions of the prototype FFC 20 are as follows. The target flex life was 4 million times or more. The longitudinal elastic coefficients of the plastic films with adhesives 22 and 23, which greatly vary depending on the test conditions, were measured using a tensile tester with a gauge length of 30 mm, a sample width of 10 mm, and a tensile speed of 4 mm / min.

○ Test FFC Conductor: Solder-plated rectangular TPC wire (thickness: 0.035 mm x width: 0.7 mm, plating thickness: 1.5 μm) Plastic film with adhesive: Film / PET (thickness: 25 μm) Adhesive / Flame retardant polyester type (thickness 35 μm, of which anchor coating agent (AC agent) is about 3 μm) Cable dimensions: 170 μm thickness × 15 mm width between conductors 1.0 mm Number of cores 14 cores ○ Flex life measurement conditions Flex speed V : 1500 times / minute Stroke S: 25mm Distance between FFC fixed plates H: 7mm Life detection: Number of times the conductor current for monitoring stopped for 10 ^-6 seconds or more or conductor resistance increased by 10% from the initial value. 4,000,000 times or more Table 1 and Table 2 show the mechanical properties and flex life evaluation results of the constituent materials of the FFCs tested.

[0049]

[Table 1]

[0050]

[Table 2]

No. 1 in Table 1. Nos. 1 to 4 show the results of the bending-resistant FFC according to the present invention. 5 to 7 show the results of the FFC according to the prior art. From Tables 1 and 2, the modulus of longitudinal elasticity of the film with the adhesive and the mechanical properties of the conductor (tensile strength,
By increasing the 0.2% proof stress and elongation), it was verified that the flex life of the FFC was significantly improved as compared with the conventional FFC.

No. 1 having a low 180 ° peel strength (measured at a pulling speed of 20 mm / min) indicating the bonding strength between the conductor and the adhesive. The FFC of 15, 16 is the longitudinal modulus of elasticity of the film with the adhesive and the mechanical properties of the conductor (tensile strength,
Despite setting high 0.2% proof stress and elongation),
The service life has been shortened. From these results, it can be seen that the adhesive strength of the adhesive has a great effect on the flex life of the FFC, and that a peel strength of 1.0 kg / cm or more is required.

In the above, by increasing the modulus of longitudinal elasticity and the adhesive strength of a plastic film with an adhesive of FFC, and by enhancing the mechanical properties (tensile strength, 0.2% proof stress and elongation properties) of the conductor, Using conductors with high conductivity without reducing the thickness of the film with adhesive or adhesive
High flex resistance can be imparted to C.

[0054]

In summary, according to the present invention, the following excellent effects are exhibited.

It is possible to provide a flexible flat cable having high bending resistance, without reducing the thickness of the plastic film with an adhesive or the conductor.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of a flexible flat cable according to the present invention.

FIG. 2 is a view of the device shown in FIG.

FIG. 3 is a conceptual diagram showing an apparatus for manufacturing a flexible flexible flat cable.

FIG. 4 is a view of the manufacturing apparatus shown in FIG.

FIG. 5A is a side view showing a basic structure of a flexible flexible flat cable using a pure Sn or a solder-plated rectangular conductor as a representative product, and FIG. 5B is a cross-sectional view taken along the line BB of FIG. FIG.

FIG. 6 is a conceptual diagram of a repeated sliding and bending test apparatus.

FIG. 7 is a partially enlarged view of a bent portion of the flexible flat cable which is repeatedly tested by the apparatus shown in FIG. 6;

FIG. 8 is a sectional view taken along line CC of FIG. 3;

[Explanation of symbols]

 Reference Signs List 20 FFC (flexible flexible flat cable) 21 conductor 21a conductor group 22, 23 plastic film with adhesive

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayoshi Aoyama 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Cable Engineering Co., Ltd. (72) Inventor Masato Ito 4-chome Kawajiri-cho, Hitachi City, Ibaraki Prefecture No. 10-1 Hitachi Cable Finetech Co., Ltd. (72) Inventor Tsutomu Komori 4-1-1 Kawajiricho, Hitachi City, Ibaraki Prefecture Within Hitachi Cable Finetech Co., Ltd. (72) Inventor Katsuo Endo Hidaka, Hitachi City, Ibaraki Prefecture 5-1-1, Hachidachi Plant, Hitachi Cable Co., Ltd. F-term (reference) 5G311 AA03 AB04 AC06 AD03 CA02 CD03 5G333 AA03 AB07 AB10 AB14 BA03 CB04 DA03

Claims (3)

[Claims] 1. A flexible flat cable in which at least one conductor is arranged in parallel, laminated with two insulating plastic films with adhesive, and integrated, the longitudinal elastic modulus of the plastic film with adhesive is A flexible flat cable having a flex resistance of 209 kg / mm ² or more. 2. A 180 ° peel strength between the adhesive of the plastic film with the adhesive and the conductor is 1.0.
The flexible flat cable according to claim 1, wherein the cable is not less than kg / cm. 3. The conductor has an elongation of 25% or more and a tensile strength of 25 kg / mm ² or more and less than 30 kg / mm ² ,
0.2% proof stress 15 kg / mm ² or more 20 kg / mm ²
The flexible flat cable according to claim 1 or 2, wherein the flat copper wire is less than the rectangular flat copper wire.