JP2003031033A - Flexible flat cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible flat cable having proper matching with a high frequency circuit and short propagation delay time. SOLUTION: A conductor row 3 with a plurality of straight-angle conductors 2, arrayed in parallel in the width direction, is pinched with foamed insulators 21 from both sides in the width direction and is laminated, whereby the dielectric constant of the foamed insulators 21 is composited with that of air, and the resulting complex dielectric constant becomes lower than that (about 3.0) of the conventional unfoamed insulators, so that the propagation delay time becomes low of 5 ns/m or smaller. By lowering the complex dielectric constant of the foamed insulators 21, capacitance which is factor of characteristics impedance can be controlled, and characteristics impedance can be set at 50 Ω. Therefore, matching of a flat flexible cable 20 with a high-frequency circuit is improved, and propagation delay time is shortened.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a flexible flat cable.

[0002]

2. Description of the Related Art FIG. 5 is a sectional view showing a conventional example of a flexible flat cable.

This flexible flat cable 1 is
A plurality of plated flat conductors 2 of arbitrary width are arranged in parallel in the width direction at a predetermined center interval to form a conductor row 3, and the conductor row 3 is bonded from both sides in the thickness direction (vertical direction in the figure). The film-shaped insulator 4 with layers is sandwiched so that the adhesive layers 5 are in contact with each other (inward), and laminated.

FIG. 6 is a sectional view showing another conventional example of a flexible flat cable.

This flexible flat cable 6 is
A shielding tape 10 having a conductive adhesive layer 7, an aluminum vapor-deposited metal layer 8 and a film-like insulator 9 in this order on both film-like insulators 4 of the flexible flat cable 1 shown in FIG.
Is adhered from both sides, and the aluminum vapor-deposited metal layer 8 and at least one rectangular conductor 2a are electrically connected.

[0006]

By the way, while the value of the characteristic impedance on the input / output side of a general high frequency circuit (for example, an amplifier circuit) is 50Ω, a flexible flat cable which is a transmission line used in the high frequency circuit. The value of the characteristic impedance (hereinafter referred to as “FFC”) is 70 to 90Ω for the FFC as shown in FIG. 5 and 10 to 30Ω for the FFC as shown in FIG. 6, so that the high frequency circuit and the FFC are different. When they are connected, energy is reflected at the connection points, resulting in loss.

Further, the propagation delay time of the FFC shown in FIG. 5 is 12 to 13 ns / m, and the propagation delay time of the FFC shown in FIG. 6 is 6 to 8 ns / m, which are currently used in transmission lines. There was a problem that the value was large compared to existing cables.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems and to provide a flexible flat cable having good compatibility with a high frequency circuit and a short propagation delay time.

[0009]

In order to achieve the above object, the flexible flat cable of the present invention comprises a conductor row in which a plurality of conductors are arranged in parallel, and an adhesive which is laminated after sandwiching the conductor row from both sides. The foamed insulator with layers and the metal layer with conductive adhesive layers sandwiching the foamed insulators with both adhesive layers from both sides are provided.

The flexible flat cable of the present invention includes a conductor row in which a plurality of flat rectangular conductors having a width of 0.5 mm are arranged in parallel in the width direction with a conductor center interval of 1.0 mm, and a conductor row is formed. It has a foamed insulator with an adhesive layer having a thickness of 0.15 mm to 0.25 mm, which is laminated after being sandwiched from both sides in the thickness direction, a conductive adhesive layer, an aluminum foil metal layer, and a film-like insulator in order. And a shielding tape having a thickness of 0.04 mm, which is attached to the outside of each of the foamed insulators so that the conductive adhesive layer contacts the foamed insulators.

In addition to the above structure, in the flexible flat cable of the present invention, it is preferable that at least one of the conductors and the metal layer are electrically connected via a conductive adhesive layer.

According to the present invention, the dielectric constant of the foamed insulator is obtained by sandwiching a conductor row in which a plurality of rectangular conductors are arranged in parallel in the width direction with foamed insulators from both sides in the thickness direction and then laminating. Becomes complex with the permittivity of air, and the complex permittivity becomes lower than the permittivity (about 3.0) of the conventional non-foamed insulator (about 1.5), so that the propagation delay time is 5 ns. / M or less. By reducing the composite permittivity of the foamed insulator, it is possible to control the electrostatic capacitance, which is a factor of the characteristic impedance, and the characteristic impedance can be set to 50Ω. Therefore, the compatibility between the flexible flat cable and the high frequency circuit is improved.
Note that the factors of capacitance are the conductor width and the dielectric constant / thickness of the insulating film (assuming that there is a shield).

In particular, the rectangular conductor has a width of 0.5 mm, the conductor center interval is 1.0 mm, the thickness of the foam insulation is 0.15 mm to 0.25 mm, and the thickness of the shielding tape is 0.04 mm. As a result, the characteristic impedance value becomes 50Ω, and the transmission line propagation delay time is 5 ns /
m or less.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1A is a plan view showing an embodiment of the flexible flat cable of the present invention, FIG. 1B is a sectional view taken along line 1b-1b of FIG. 1A, and FIG. Figure 1
It is the 1c-1c sectional view taken on the line of (a). The same reference numerals are used for the same members as in the conventional example shown in FIG.

This flexible flat cable 20
Is a conductor row 3 in which a plurality of (8 in the figure, but not limited to) rectangular conductors 2 are arranged in parallel in the width direction. It is sandwiched after sandwiching, and sandwiched between the metal layers 22 with a conductive adhesive layer from both sides.

Specifically, a plurality of plated (eg tin-plated) 0.035 mm thick and 0.5 mm wide rectangular conductors (eg copper) 2 are arranged in parallel so that the conductor center interval is 1.0 mm. To form the conductor row 3, and the body row 3 is formed into a foamed insulator (for example, PET (polyethylene terephthalate)) 2 having a thickness of 0.15 mm to 0.25 mm with an adhesive layer.
1 is sandwiched so that the adhesive layers 5 are in contact with each other and laminated, and further has a conductive adhesive layer 5, an aluminum foil metal layer 22 and a film-shaped insulator 9 in order on both sides (vertical direction in FIG. 1B). A shielding tape 23 having a thickness of 0.04 mm is attached (the thickness of the adhesive layer 5 is 0.03 mm or 0.04 mm, the thickness of the foamed insulator 21 is 0.18 m).
m).

The aluminum foil metal layer 22 and at least one rectangular conductor 2a of the conductor array 3 are electrically connected via the conductive adhesive layer 7. Incidentally, 24 is a reinforcing layer.

By combining the permittivity of the foamed insulator 21 with the permittivity of air, the permittivity of the conventional insulator is 3.0.
It is possible to reduce the capacitance value to about 1.5, and to control the electrostatic capacitance value by using the above-described structure, to reduce the characteristic impedance to 50Ω and the propagation delay time.

[0020]

EXAMPLES Next, the widths and conductor center intervals of a plurality of plated rectangular conductors 2, the thickness of the foamed insulator 21, and the shielding tape 2
An example in which the dimensions specified in the present invention are applied to the thickness of 3;
The width and conductor center spacing of a plurality of plated rectangular conductors 2, the thickness of the foamed insulator 21, and the thickness of the shielding tape 23 are compared with a comparative example in which dimensions not specified in the present invention are applied.

(Example 1) The width W of the rectangular conductor 2 was 0.5 m.
m, the conductor center interval P is 1.0 mm, the thickness of the foam insulator 21 is 0.18 mm, and the thickness of the shielding tape 23 is 0.04 m.
As m, an FFC having the structure shown in FIG. 1 was produced.

(Embodiment 2) The width W of the rectangular conductor 2 is 0.5 m.
m, the conductor center interval P is 1.0 mm, the thickness of the foamed insulator 21 is 0.22 mm, and the thickness of the shielding tape 23 is 0.04 m.
As m, an FFC having the same structure as in Example 1 was produced.

(Comparative Example 1) The width W of the rectangular conductor 2 is 0.5 m.
m, the conductor center interval P is 1.0 mm, the thickness of the foamed insulator 21 is 0.10 mm, and the thickness of the shielding tape 23 is 0.04 m.
As m, an FFC having the same structure as in Example 1 was produced.

(Comparative Example 2) The width W of the rectangular conductor 2 is 0.3 m.
m, the conductor center interval P is 1.0 mm, the thickness of the foam insulator 21 is 0.18 mm, and the thickness of the shielding tape 23 is 0.04 m.
As m, an FFC having the same structure as in Example 1 was produced.

(Comparative Example 3) The width W of the rectangular conductor 2 is 0.7 m.
m, the conductor center interval P is 1.0 mm, the thickness of the foam insulator 21 is 0.18 mm, and the thickness of the shielding tape 23 is 0.04 m.
As m, an FFC having the same structure as in Example 1 was produced.

(Comparative Example 4) The width W of the rectangular conductor 2 is 0.5 m.
m, the conductor center interval P is 1.25 mm, the thickness of the foam insulator 21 is 0.18 mm, and the thickness of the shielding tape 23 is 0.04.
An FFC having the same structure as that of Example 1 was produced in mm.

(Comparative Example 5) The width W of the rectangular conductor 2 is 0.5 m.
m, the conductor center interval P is 0.8 mm, the thickness of the foamed insulator 21 is 0.18 mm, and the thickness of the shielding tape 23 is 0.04 m.
As m, an FFC having the same structure as in Example 1 was produced.

Characteristic impedance / propagation delay time is measured by an oscilloscope (manufactured by Sony Tektronix 11801).
B) was used for measurement by a TDR (Time Domain Reflectometer) method. Those having characteristic impedance of 50 ± 3Ω and propagation delay time of 5 ns / m or less are marked as “◯”, those satisfying one of them are marked as “△”, and those not satisfying both are marked as “×”. It was judged as ". The judgment results are shown in Table 1. However, the thickness of the rectangular conductor was 0.035 mm. The conductor thickness is 0.022 mm
Even with 0.1 mm, there was almost no difference in the results.

[0029]

[Table 1]

From the table, the width of the rectangular conductor 2 is 0.5 mm, the conductor center interval is 1.0 mm, and the thickness of the foamed insulator 21 is 0.
15 mm to 0.25 mm, the thickness of the shielding tape 23 is 0.
It can be seen that it is preferable to set it to 04 mm.

FIG. 2 is a plan view showing a modification of the flexible flat cable of the present invention. 1 (a)-(c)
The difference with the flexible flat cable shown in
This is that the conductor center spacing in the width direction of the flat conductor 2 is different.
For example, F with conductor center spacing of 0.8 mm, 1.25 mm, etc.
It is FC.

FIG. 3A is a plan view of the connector connecting component 25, and FIG. 3B is a sectional view taken along line 3b-3b of FIG. 3A. FIG. 4A is a plan view showing a state in which the connector connecting component 25 shown in FIG. 2 and the connector connecting component shown in FIGS. 3A and 3B are connected to each other, and FIG.
FIG. 4B is a sectional view taken along line 4b-4b of FIG.

Reinforcing layer (FIG. 1 (c)) 24 and foam insulation 2
The flat conductor 2 of the terminal portion (at least one side) of the FFC 20 from which a part of 1 is removed is connected to the flat conductor 27 of the terminal portion 26 of the connector connecting component 25 by ultrasonic waves, solder, laser, or the like. Has been done.

The connector connecting part 25 is formed by adhering a film-like insulator 28, a reinforcing layer 29 and a heat resistant reinforcing layer 30 to each other and is adjusted to the conductor center interval of a connector (not shown) to be fitted in advance. The rectangular conductor 27 is wired in the film-shaped insulator 28. The thickness of the reinforcing layer 29 can be freely set according to various connectors for easy fitting.

In the above, it has a value equivalent to 50Ω which is the value of the characteristic impedance of a general high frequency circuit,
That is, it is possible to obtain a flexible flat cable that can achieve impedance matching with a high frequency circuit.

A flexible flat cable having a current transmission line propagation delay time level of 5 ns / m or less can be obtained.

[0037]

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

It is possible to provide a flexible flat cable having good matching with a high frequency circuit and a short propagation delay time.

[Brief description of drawings]

FIG. 1A is a plan view showing an embodiment of a flexible flat cable of the present invention, and FIG. 1B is a view 1b of FIG.
-1b line sectional view, (c) is a 1c-1c line sectional view of (a).

FIG. 2 is a plan view showing a modified example of the flexible flat cable of the present invention.

FIG. 3A is a plan view of a connector connecting part,
(B) is a 3b-3b line sectional view of (a).

FIG. 4A is a plan view showing a state in which the flexible flat cable shown in FIG. 2 and the connector connecting parts shown in FIGS. 3A and 3B are connected, and FIG. It is the 4b-4b sectional view taken on the line a).

FIG. 5 is a cross-sectional view showing a conventional example of a flexible flat cable.

FIG. 6 is a cross-sectional view showing another conventional example of a flexible flat cable.

[Explanation of symbols]

2 flat conductor 3 conductor row 5 Conductive adhesive layer 21 Foam insulation 22 Aluminum foil metal layer 23 Shielding tape

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masato Ito             4-10-1, Kawajiri-cho, Hitachi-shi, Ibaraki Hitachi             Electric Wire Fine Tech Co., Ltd. F-term (reference) 5G311 CA01 CB05 CC01 CD10

Claims (3)

[Claims] 1. A conductor row in which a plurality of conductors are arranged in parallel, a foamed insulator with an adhesive layer laminated after sandwiching the conductor row from both sides, and a foamed insulator with both adhesive layers from both sides. A flexible flat cable comprising a sandwiched metal layer with a conductive adhesive layer. 2. A conductor row in which a plurality of flat rectangular conductors having a width of 0.5 mm are plated in parallel and are arranged in parallel in the width direction at a conductor center interval of 1.0 mm, and the conductor row is formed on both sides in the thickness direction. After being sandwiched, it is laminated and has a thickness of 0.15 mm ~
A foamed insulator with an adhesive layer of 0.25 mm, a conductive adhesive layer, an aluminum foil metal layer, and a film-shaped insulator in order, so that the conductive adhesive layer contacts both foamed insulators. 0.04m thick attached to the outside of each
A flexible flat cable characterized by having a shielding tape of m. 3. The flexible flat cable according to claim 1, wherein at least one of the conductors and the metal layer are electrically connected via the conductive adhesive layer.