JP7701783B2 - Coaxial Flat Cable - Google Patents

Description

The present invention relates to a coaxial flat cable, and more specifically, to a coaxial flat cable that is used in or between electronic devices such as liquid crystal televisions and servers, suppresses impedance fluctuations, and has a uniform pitch for easy connection to a circuit board.

Flat cables are excellent in workability and flexibility, and are widely used as internal wiring materials and external wiring materials for electronic devices. In particular, coaxial flat cables using multiple coaxial cables have been proposed as flat cables suitable for transmitting high-frequency signals. For example, Patent Document 1 proposes a coaxial flat cable with a large central conductor diameter, a small finished outer diameter, and stable high-frequency characteristics. This coaxial flat cable has multiple coaxial cables arranged in parallel at a predetermined interval and a fixing tape that integrates at least the terminal portions of the multiple coaxial cables from one side or both sides, and the coaxial cable at least includes a central conductor, a dielectric layer provided on the outer periphery of the central conductor and having a continuous void portion in the longitudinal direction, an outer conductor provided on the outer periphery of the dielectric layer, and an insulating layer provided on the outer periphery of the outer conductor.

JP 2019-67518 A

In the conventional coaxial flat cables described above, each coaxial cable is terminated before being connected to a circuit board, connector, etc. The termination of the coaxial cable is performed by stripping off the outer jacket to expose the outer conductor, and then stripping off the outer conductor and insulator to expose the central conductor. The exposed outer conductor and central conductor are soldered to their corresponding circuit board electrodes. At this time, there is a problem that impedance mismatch occurs in the part where the outer conductor has been stripped, resulting in poor transmission characteristics.

In addition, the coaxial cables are arranged to match the pitch of the board electrodes, but this pitch is often larger than the outer diameter of the coaxial cables, making it necessary to manufacture a coaxial flat cable with appropriate gaps between the coaxial cables. However, each coaxial cable is circular and prone to misalignment, making it difficult to maintain the specified gaps between the coaxial cables so that they can be stably soldered to the board electrodes.

The present invention was made to solve the above problems, and its purpose is to provide a coaxial flat cable that can suppress impedance fluctuations and maintain a specified distance between coaxial cables, making it easy to connect to a board.

The coaxial flat cable according to the present invention comprises a plurality of coaxial cables arranged at intervals in the width direction, and a resin tape that is attached to one or both sides of at least the terminal portions of the plurality of coaxial cables to integrate the terminal portions, and the plurality of coaxial cables are each terminated and soldered to a board or connector. In the coaxial flat cable, a metal member is disposed between adjacent coaxial cables at least in the portion that forms the coaxial structure of the coaxial cables, and the metal member is soldered to the board or connector together with the coaxial cables.

According to this invention, the metal member is disposed between adjacent coaxial cables at least in the portion that forms the coaxial structure of the coaxial cables, and is therefore disposed at least in the coaxial structure portion (the portion where the insulator is exposed) that does not have an outer conductor. Furthermore, since the metal member is solder-connected to the board or connector together with the coaxial cable, it is connected to the outer conductor of the coaxial cable as a common GND. Therefore, it is possible to suppress the fluctuation of impedance in the portion where the insulator is exposed. Furthermore, since the metal member is disposed between adjacent coaxial cables, it is possible to maintain a predetermined distance between the coaxial cables.

In the coaxial flat cable according to the present invention, the coaxial cable comprises at least a central conductor, an insulator disposed around the central conductor, an outer conductor disposed around the insulator, and an outer jacket disposed around the outer conductor.

According to this invention, the coaxial structure part in which the metal member is placed is placed arbitrarily in the exposed part of the central conductor that is no longer a coaxial structure after terminal processing, but is always placed in the exposed part of the insulator from which the outer conductor has been stripped. As a result, it is possible to suppress the fluctuation of impedance at least in the part where the insulator is exposed.

In the coaxial flat cable according to the present invention, the metal member is arranged so that its tip is located between the tip of the central conductor and the tip side of the peeled portion or the portion to be peeled of the outer conductor.

In the coaxial flat cable according to the present invention, if the metal member is a metal wire, then when the outer diameter of the metal wire is D1 and the outer diameter of the coaxial cable is D2, D1/D2 is within the range of 0.5 to 1.5.

In the coaxial flat cable according to the present invention, the resin tape is (a) a cover tape that sandwiches and integrates the entirety of the multiple coaxial cables from both sides, (b) a reinforcing tape that is provided at the terminal portions of the multiple coaxial cables, or (c) a cover tape that sandwiches and integrates the entirety of the multiple coaxial cables from both sides and a reinforcing tape that is attached to one side of the cover tape at the terminal portions of the multiple coaxial cables.

The present invention provides a coaxial flat cable that can suppress impedance fluctuations and maintain a predetermined distance between coaxial cables, making it easy to connect to a board.

1 is a perspective view showing an example of a coaxial flat cable according to the present invention. FIG. 4 is a perspective view showing another example of a coaxial flat cable according to the present invention. FIG. 4 is a perspective view showing another example of a coaxial flat cable according to the present invention. 3A is a cross-sectional view of the coaxial flat cable shown in FIG. 1; FIG. 3B is a cross-sectional view of the coaxial flat cable shown in FIG. 2; and FIG. 3C is a cross-sectional view of the coaxial flat cable shown in FIG. 1A and 1B are cross-sectional views of coaxial cables constituting a coaxial flat cable, in which (A) is an example of a solid insulator and (B) is an example of a hollow insulator. FIG. 2 is a plan view showing an example of a coaxial flat cable after terminal processing. 7A is a plan view showing an example of the coaxial flat cable of FIG. 6 after being soldered to a substrate, and FIG. 7B is a side view showing the same. FIG. 11 is a plan view showing another example of a coaxial flat cable after terminal processing. 9A is a plan view showing an example of the coaxial flat cable of FIG. 8 after being soldered to a substrate, and FIG. 9B is a side view showing the same. FIG. 1 is a plan view showing an example of a conventional coaxial flat cable after terminal processing. 11A is a plan view showing an example of the coaxial flat cable of FIG. 10 after it has been soldered to a substrate, and FIG. 11B is a side view showing the same.

The following describes an embodiment of a coaxial flat cable according to the present invention with reference to the drawings. Note that the present invention includes inventions with the same technical concept as the embodiments described below and the forms shown in the drawings, and the technical scope of the present invention is not limited to the description of the embodiments or the descriptions in the drawings.

As shown in Figs. 1 to 6, the coaxial flat cable 20 according to the present invention comprises a plurality of coaxial cables 10 arranged at intervals in the width direction X, and a resin tape 11 that integrates at least the terminal portions 21 of the coaxial cables 10 from one or both sides. The coaxial flat cable 20 is formed by processing the terminals of the plurality of coaxial cables 10 and soldering them to a substrate 30 or the like. In the coaxial flat cable 20, a metal member 7 is disposed between adjacent coaxial cables at least in the portion that forms the coaxial structure of the coaxial cables 10, and the metal member 7 is soldered together with the coaxial cables 10 to the substrate 30 or the like.

This coaxial flat cable 20 has the metal member 7 disposed between adjacent coaxial cables at least in the portion that forms the coaxial structure of the coaxial cable 10, and is therefore disposed at least in the coaxial structure portion (where the insulator 2 is exposed) that does not have the outer conductor 3. The metal member 7 is solder-connected to the board 30 or connector together with the coaxial cable 10, and is connected to the outer conductor 3 of the coaxial cable 10 as a common GND (GND member not shown). This makes it possible to suppress impedance fluctuations in the portion where the insulator 2 is exposed. Furthermore, because the metal member 7 is disposed between adjacent coaxial cables, a predetermined distance can be maintained between the coaxial cables.

The components of a coaxial flat cable are explained below.

<Coaxial cable>
The coaxial cables 10 constitute a coaxial flat cable 20, and a plurality of the coaxial cables 10 are arranged side by side at intervals in the width direction X, as shown in Fig. 1 to Fig. 3. As shown in Fig. 5, the coaxial cable 10 at least includes a central conductor 1, an insulator 2 provided on the outer periphery of the central conductor 1, an outer conductor 3 provided on the outer periphery of the insulator 2, and an outer jacket 4 provided on the outer periphery of the outer conductor 3. Then, as shown in Fig. 6 to Fig. 9, after an end portion 21 of the coaxial cable 10 is processed, the exposed central conductor 1 and outer conductor 3 are soldered to a substrate 30 or electrodes 31, 32 of a connector.

(center conductor)
As shown in Fig. 5 (A) and (B), the central conductor 1 is composed of one wire extending in the longitudinal direction Y of the coaxial cable 10, or is composed of a plurality of wires twisted together. The type of the wire is not particularly limited as long as it is made of a metal with good electrical conductivity, but preferred examples include metal conductors with good electrical conductivity such as copper wire, copper alloy wire, aluminum wire, aluminum alloy wire, and copper-aluminum composite wire, or those with a plating layer applied to the surface. From the viewpoint of high frequency use, copper wire and copper alloy wire are particularly preferred. As the plating layer, a solder plating layer, a tin plating layer, a gold plating layer, a silver plating layer, a nickel plating layer, and the like are preferred. The cross-sectional shape of the wire is also not particularly limited, but the cross-sectional shape may be circular or approximately circular, or may be rectangular.

The cross-sectional shape of the central conductor 1 is not particularly limited. It may be circular (including elliptical) or rectangular, but is preferably circular. It is desirable that the outer diameter of the central conductor 1 is as large as possible so that the electrical resistance (AC resistance, conductor resistance) is small, but in order to reduce the final outer diameter of the coaxial cable 10, for example, the outer diameter may be in the range of about 0.1 to 0.4 mm. Note that each coaxial cable 10 is preferably in the range of 2.5 to 10 times the outer diameter of the central conductor 1. An insulating coating (not shown) may be provided on the surface of the central conductor 1 as necessary. The type and thickness of the insulating coating are not particularly limited, but it is preferable to use one that decomposes well during soldering, and a thermosetting polyurethane coating is a preferable example.

(Insulator)
As shown in FIG. 5, the insulator 2 is a low dielectric constant insulating layer that is continuously provided on the outer periphery of the central conductor 1 in the longitudinal direction. The material of the insulator 2 is not particularly limited and may be selected as desired depending on the impedance characteristics required. However, for example, fluororesins with a low dielectric constant of 2.0 to 2.5, such as PFA (ε2.1), ETFE (ε2.5), and FEP (ε2.1), are preferred, and PFA resin is particularly preferred. The material of the insulator 2 may contain a colorant. The thickness of the insulator 2 is also not particularly limited and may be selected as desired depending on the impedance characteristics required, but it is preferred to set the thickness within the range of about 0.15 to 1.5 mm, for example. The method of forming the insulator 2 is not particularly limited, but any of solid, hollow, and foamed structures can be easily formed by extrusion.

The insulator 2 may have a solid structure as shown in FIG. 5(A), a hollow structure as shown in FIG. 5(B), or a foam structure (not shown). The hollow structure has a void 2A inside the structure, and can have a cross-sectional shape in which the void 2A is surrounded by an inner annular portion 2B, an outer annular portion 2C, and a connecting portion 2D. In the case of a hollow structure or a foam structure, the material density of the insulator 2 is reduced, and there is an additional effect that the insulator 2 can be softened. The void 2A is continuously provided in the insulator 2, and its shape may be round or rectangular, and is not particularly limited. The insulator 2 having such a hollow structure has excellent lateral pressure strength, so it is difficult to be crushed during the manufacture of the coaxial cable 10 and the coaxial flat cable 20 or during the wiring work of the coaxial flat cable 20, and the high frequency characteristics can be stable. The insulator 2 having a hollow structure can be molded by extruding resin around the outer periphery of the central conductor 1 traveling through an extrusion die. The thickness of each of the inner annular portion 2B, the outer annular portion 2C, and the connecting portion 2D is not particularly limited, but may be within a range of, for example, 0.01 mm to 0.05 mm, and the outer diameter of the hollow structured insulator 2 may be within a range of, for example, 0.4 mm to 1.0 mm.

(Outer conductor)
The outer conductor 3 is provided on the outer periphery of the insulator 2, and may be a braided or horizontally wound thin wire, a metal-layered insulating tape (e.g., a polyethylene terephthalate film with a copper layer, or the like), or a combination of both. In the example of Fig. 5, a horizontally wound thin wire 3A is provided on the outer periphery of the insulator 2, and a metal-layered insulating tape 3B is further provided to cover it, but this configuration is not limited. The thickness of the outer conductor 3 is not particularly limited, but is within the range of about 0.01 mm to 0.15 mm, for example.

(outer covering)
The jacket 4 is provided on the outer periphery of the outer conductor 3, and the material is not particularly limited as long as it has insulating properties. Preferably, as illustrated in FIG. 5, the jacket 4 can be constructed by spirally winding an insulating tape 4A having an adhesive layer 4B on one side thereof, but is not limited to this form. As the adhesive layer 4B, various adhesives applied to the coaxial cable 10 can be used, and for example, a polyester-based thermoplastic adhesive resin can be preferably exemplified, and as the insulating tape 4A, a polyester film such as a polyethylene terephthalate film can be preferably exemplified. In particular, it is preferable to select a material having good adhesion to the resin tape 11 described later, and for example, when the adhesive layer constituting the resin tape 11 is a polyester-based thermoplastic adhesive layer, the jacket 4 is also preferably a polyester film. The total thickness of the insulating tape 4A having an adhesive layer 4B on one side thereof is preferably within a range of 0.03 mm to 0.1 mm.

(others)
The coaxial flat cable 20 may be provided with a shielding layer (not shown) as necessary. The shielding layer is provided on the resin tape 11 shown in FIG. 1, for example. An example of the shielding layer is a tape composed of at least a metal foil and a conductive adhesive layer provided on one side of the metal foil, but the layer structure is not particularly limited as long as it can exhibit a shielding function. The shielding layer can also act to keep the capacitance and external inductance between the central conductor and the shielding layer uniform, and can prevent impedance mismatches from occurring in this area.

<Metallic Components>
As shown in Fig. 1 to Fig. 4, the metal member 7 is an essential member constituting the coaxial flat cable 20. The coaxial cables 10 are arranged side by side with a gap therebetween in the width direction X, and the "gap" is ensured by the metal member 7. That is, the metal members 7 are arranged side by side in the width direction X between the coaxial cables 10, so that the coaxial cables 10 are arranged with a gap therebetween. "With a gap" includes both cases where the coaxial cables 10 are arranged side by side with a metal member (metal wire) 7 interposed between them as shown in Fig. 1, Fig. 2, and Fig. 4(A) and (B), and cases where the two coaxial cables 10, 10 are closely attached pair wires 10a, and the pair wires 10a, 10a are arranged side by side with a metal member (metal wire) 7 interposed between them as shown in Fig. 3 and Fig. 4(C). As long as there are some parts spaced apart by the metal member 7, other configurations are also acceptable. For example, the coaxial flat cable 20 may include the single wire and pair wire of the coaxial cable 10, as in the following order from one side in the width direction X: pair wire 10a, metal member 7, coaxial cable 10, metal member 7, pair wire 10a, metal member 7, .... Note that the metal member 7 may be located in the middle between the upper and lower cover tapes 11a as shown in Fig. 4(A), or may be in contact with the lower reinforcing tape 11b or cover tape 11a as shown in Fig. 4(B) and (C). The metal member 7 thus arranged can maintain a predetermined interval between the coaxial cables, facilitating connection to the substrate 30, etc.

As shown in Figs. 1 to 3, the metal member 7 is a metal wire. The cross-sectional shape of the metal wire is not particularly limited, but is preferably a circular round wire as shown in Fig. 4. When the outer diameter of the circular cross-sectional metal wire is D1 and the outer diameter of the coaxial cable 10 is D2, it is preferable that D1/D2 is within the range of 0.5 to 1.5. By setting it in this range, the coaxial cable 10 and the metal wire can be adhered and fixed to the resin tape 11. On the other hand, if D1/D2 is less than 1/2, the metal wire cannot be adhered to the resin tape 11, and the spacing between the coaxial cables may become unstable, and if D1/D2 exceeds 1.5, the resin tape 11 and the coaxial cable 10 may not adhere to each other, and the required adhesion may not be obtained.

In the longitudinal direction Y, the metal member 7 is arranged at least in the portion between adjacent coaxial cables that forms a coaxial structure, as shown in Figs. 6 and 8. Since the "coaxial structure" does not mean that the central conductor 1 alone is a coaxial structure, "the metal member 7 is arranged at least in the portion that forms a coaxial structure" means that it is always arranged in the portion where the insulator 2 is provided on the outer periphery of the central conductor 1. Therefore, the entire intermediate portion 22 of the coaxial cable 10 is included, and in the terminal portion 21, as shown in Figs. 6 and 8, the metal member 7 is always arranged in the portion where the outer conductor 3 is exposed by terminal processing and the portion where the insulator 2 is exposed. Also, as shown in Fig. 8, it is not essential to arrange the metal member 7 in the portion where only the central conductor 1 is not a coaxial structure, but it may be arranged arbitrarily. That is, the tip 7a of the metal member 7 is arranged so as to be located between the tip 1a of the exposed central conductor 1 after terminal processing and the tip side 3a of the tip peeled portion or the portion to be peeled portion of the exposed insulator 2 after terminal processing.

In this way, the metal member 7 is placed at least in the coaxial structure portion (the portion that becomes the coaxial structure) without the outer conductor 3, and is soldered to the board 30 or connector together with the outer conductor 3 of the coaxial cable 10. In this way, as shown in Figures 7 and 9, the metal member 7 is connected to the outer conductor 3 of the coaxial cable 10 as a common GND (GND member not shown). Therefore, it is possible to suppress the fluctuation of impedance in the portion where the insulator 2 is exposed.

The metal member 7 may be a single metal wire extending in the longitudinal direction Y of the coaxial cable 10, or may be a twisted wire formed by twisting together a plurality of strands. In the case of a twisted wire, it is desirable that the strands do not fray and the outer diameter does not change. For example, it is preferable that thin wires coated with an insulating layer with a solderable fusion layer are twisted together and then fused to prevent fraying. The strands are not particularly limited as long as they are made of a metal with good electrical conductivity, but preferred examples include metal conductors with good electrical conductivity such as copper wire, copper alloy wire, aluminum wire, aluminum alloy wire, and copper-aluminum composite wire, or those with a plating layer applied to the surface thereof. Preferred examples of the plating layer include a solder plating layer, a tin plating layer, a gold plating layer, a silver plating layer, and a nickel plating layer. The surface of the metal member 7 may be provided with a solderable insulating coating (not shown) as necessary. The reason for using a solderable insulating coating is that it is soldered together with the outer conductor 3 of the coaxial cable 10m, as shown in Figures 9 and 11. There are no particular limitations on the type and thickness of the insulating coating that can be soldered, but it is preferable to use one that decomposes easily when soldered, such as a thermosetting polyurethane coating. When an insulating coating is provided, the outer diameter of the metal member 7 includes the thickness of the insulating coating.

The outer diameter of the coaxial cable 10 thus constructed is preferably within the range of approximately 0.1 to 0.4 mm, as described above, and is preferably within the range of 2.5 to 10 times the outer diameter of the central conductor 1.

<Resin tape>
The resin tape 11 constitutes the coaxial flat cable 20, and is used to bond at least the terminal portions 21 of the multiple coaxial cables 10 arranged at intervals in the width direction X from one side or both sides to integrate the terminal portions 21 as shown in Figures 1 to 4. Examples of the resin tape 11 include, but are not limited to, the cover tape 11a shown in Figure 1, the reinforcing tape 11b shown in Figure 2, and the bonding of the cover tape 11a and the reinforcing tape 11b shown in Figure 3. The term "at least" means that the resin tape 11 (11a, 11b, 11a, and 11b) is always provided on the terminal portions 21, but the resin tape 11 (11a) may also be provided on the intermediate portion 22 other than the terminal portions. Note that "both sides" refers to the top and bottom surfaces of the multiple coaxial cables 10 arranged at intervals in the width direction X as shown in Figures 4(A) and (C), and "one side" refers to one side (e.g., the bottom surface) of the multiple coaxial cables 10 arranged at intervals in the width direction X as shown in Figure 4(B).

(A) The resin tape 11 shown in Fig. 1 and Fig. 4(A) is a cover tape 11a that sandwiches and integrates the entirety of multiple coaxial cables from both sides. As shown in Fig. 1, etc., it is preferable that the cover tape 11a is attached to all of the multiple coaxial cables 10 in the longitudinal direction Y, but it may also be attached only to the terminal portions 21 on both sides of the longitudinal direction Y, leaving the middle portion 22 as a non-integral portion. The non-integral portion allows the middle portion 22 to be easily deformed, improving the degree of freedom when wiring within an electronic device. Note that, in the example of Fig. 1, etc., two sheets of cover tape 11a are sandwiched and bonded to each other from both sides to integrate the cables, but it may also be possible to fold back one sheet of cover tape 11a and sandwich and bond it to each side to integrate the cables.

(a) The resin tape 11 shown in Fig. 2 and Fig. 4 (B) is a reinforcing tape 11b provided on the terminal portions 21 of multiple coaxial cables 10. As shown in Fig. 2 etc., the reinforcing tape 11b is provided only on the terminal portions 21 in the longitudinal direction Y of multiple coaxial cables 10, and the intermediate portions 22 are non-integral portions. The non-integral portion allows the intermediate portions 22 to easily deform, improving the degree of freedom when wiring within electronic devices. The length of the reinforcing tape 11b in the longitudinal direction Y is preferably, for example, about 5 to 20 mm.

(C) The resin tape 11 shown in Fig. 3 and Fig. 4(C) is composed of a cover tape 11a that sandwiches and integrates the entirety of the multiple coaxial cables from both sides, and a reinforcing tape 11b that is attached to one side of the cover tape 11a at the terminal portions 21 of the multiple coaxial cables 10. The cover tape 11a and the reinforcing tape 11b have the same configuration as described in (A) and (B).

Regarding (a) to (c), the cover tape 11a and the reinforcing tape 11b described above are usually composed of a base material and an adhesive layer. The base material for the cover tape 11a is not particularly limited, but a polyester film such as polyethylene terephthalate or polyethylene naphthalate can be preferably used. The thickness of the base material is selected from a range of about 0.025 mm to 0.1 mm. The adhesive layer is also not particularly limited, but it is desirable that the material be one that can be bonded to the outer cover 4 with good adhesion, and a preferred example is a polyester thermoplastic adhesive resin layer. The thickness of the adhesive layer is selected from a range of about 0.02 mm to 0.035 mm.

The base material of the reinforcing tape 11b is not particularly limited, and a polyester film such as polyethylene terephthalate or polyethylene naphthalate, or a polycarbonate film can be preferably used. These base materials have excellent dimensional stability, and have the advantage that dimensional changes are unlikely to occur even due to the fitting force applied when connecting to the connector, or even when the temperature changes or time passes. The thickness of the base material is selected from a range of about 0.025 mm to 0.3 mm. The adhesive layer is also not particularly limited, but it is desirable that it is made of a material that can be bonded to the outer casing 4 to be bonded with good adhesion, and a polyester-based thermoplastic adhesive resin layer is a preferred example. The thickness of the adhesive layer is selected from a range of about 0.02 mm to 0.05 mm.

The bonding of the cover tape 11a and the reinforcing tape 11b is a combination of the cover tape 11a and the reinforcing tape 11b described above, as shown in Figures 3 and 4(C), so a description of this will be omitted here.

The present invention will be explained in more detail below with reference to examples. Note that the present invention is not limited to the following examples.

[Making a coaxial cable]
The coaxial cable 10 used, as the central conductor 1, an AWG32 (outer diameter about 0.24 mm) in which seven silver-plated soft copper wires with a diameter of 0.08 mm were twisted. The insulator 2 was formed by extruding PFA resin (manufactured by DuPont) at 350° C. using a die nipple for hollow structures to form a hollow structure having a cross-sectional shape in which a void 2A is surrounded by an inner annular portion 2B, an outer annular portion 2C, and a connecting portion 2D, as shown in FIG. 8(B). In this hollow structure, the thickness of the inner annular portion 2B was 0.05 mm, the thickness of the outer annular portion 2C was 0.05 mm, the thickness of the connecting portion 2D was 0.05 mm, the outer diameter of the hollow structure (insulator 2) was 0.60 mm, and the void ratio of the void portion 2A was 30% with respect to the area of the entire insulator (entire hollow structure). The dielectric constant ε was about 1.6.

The outer conductor 3 was made of 38 tin-plated soft copper wires with a diameter of 0.05 mm, which were wound around the outer circumference of the insulator 2 at a pitch of 12 mm using a horizontal winding shielding machine to form a horizontally wound thin wire horizontal winding 3A. Furthermore, a 0.004 mm thick polyethylene terephthalate film (insulating tape with metal layer 3B) on which a 0.008 mm thick copper layer was formed was cut to a width of 2.5 mm, and a tape winding machine was used to wind the copper layer on the horizontally wound thin wire horizontal winding 3A side with 1/3.5 wrap. Next, a 0.004 mm thick polyester tape (insulating tape 4A) with a 0.001 mm thick polyester thermoplastic resin (adhesive layer 4B) on one side was cut to a width of 3.0 mm, and a tape winding machine was used to wind the adhesive layer 4B on the outer conductor side with 1/3 wrap.

[Coaxial flat cable]
Example 1
Sixteen of the obtained coaxial cables 10 were prepared, and as shown in Fig. 1 and Fig. 4 (A), the coaxial cables 10 were arranged side by side with a copper wire having a diameter of 0.5 mm between each pair of the coaxial cables 10 as the metal member 7, and then the entire surfaces of the coaxial cables 10 were bonded with a cover tape 11a as shown in Fig. 1 to integrate the two, thereby forming a coaxial flat cable 20 as shown in Fig. 4 (A). The cover tape 11a was a polyethylene terephthalate film substrate having a thickness of 0.025 mm and a polyester thermoplastic resin (adhesive layer) having a thickness of 0.035 mm on one side, cut to a width of 25 mm. The coaxial flat cable 20 was cut to a predetermined length, and the terminal portion 21 was processed as shown in Fig. 6 to expose the central conductor 1, the insulator 2, and the outer conductor 3. The longitudinal direction Y of the metal member 7 was arranged at a length such that the tip 7a was the same as the tip 1a of the central conductor 1, as shown in Fig. 6.

The obtained coaxial flat cable 20 was attached to the substrate 30 as shown in FIG. 9. The attachment was performed by soldering the central conductor 1 to the solder connection portion 41, and soldering the outer conductor 3 and the metal member 7 to the solder connection portion 42.

Example 2
Sixteen of the obtained coaxial cables 10 were prepared, and the coaxial cables 10 were arranged side by side with a copper wire having a diameter of 0.5 mm between each pair of the coaxial cables 10 as shown in Fig. 2 and Fig. 4 (B), and then the reinforcing tape 11b was attached to one side of the terminal portion 21 side to integrate the cables, and the coaxial flat cable 20 shown in Fig. 4 (B) was obtained. The reinforcing tape 11b was a polyethylene terephthalate film substrate having a thickness of 0.125 mm and a polyester thermoplastic resin (adhesive layer) having a thickness of 0.042 mm on one side, cut to a width direction X of 25 mm and a longitudinal direction Y of 10 mm. The coaxial flat cable 20 was cut to a predetermined length, and the terminal portion 21 was processed as shown in Fig. 8, so that the central conductor 1, the insulator 2, and the outer conductor 3 were exposed. The longitudinal direction Y of the metal member 7 was arranged at a length such that the tip 7a of the metal member 7 was the same as the tip 2a of the insulator 2, as shown in Fig. 8.

The obtained coaxial flat cable 20 was attached to the substrate 30 as shown in FIG. 9. The attachment was performed by soldering the central conductor 1 to the solder connection portion 41, and soldering the outer conductor 3 and the metal member 7 to the solder connection portion 42.

Example 3
Sixteen of the obtained coaxial cables 10 were prepared, and as shown in Fig. 3 and Fig. 4 (C), two of the coaxial cables 10 were arranged as pair wires 10a, and a copper wire having a diameter of 0.5 mm was interposed between the pair wires 10a as the metal member 7. Then, as shown in Fig. 3, the entire surface was attached to both sides with a cover tape 11a to integrate them, and further, a reinforcing tape 11b was attached to the terminal portion 21 on one side of the cover tape 11a to obtain a coaxial flat cable 20 shown in Fig. 4 (C). The cover tape 11a and the reinforcing tape 11b used were the same as those used in Example 1 and Example 2, respectively. The coaxial flat cable 20 was cut to a predetermined length, and the terminal portion 21 was processed in the same manner as in Fig. 6 and Fig. 8, to expose the central conductor 1, the insulator 2, and the outer conductor 3. The longitudinal direction Y of the metal member 7 was arranged at a length such that the tip 7a was the same as the tip 1a of the central conductor 1, as in Fig. 6.

The obtained coaxial flat cable 20 was attached to the substrate 30 as in FIG. 6. To attach it, the central conductor 1 was soldered to the solder connection portion 41, and the outer conductor 3 and the metal member 7 were soldered to the solder connection portion 42.

(Comparative Example 1)
Sixteen of the obtained coaxial cables 10 were prepared, and the coaxial cables 10 were arranged side by side at regular intervals as shown in Fig. 10, and then the entire surfaces of the coaxial cables 10 were bonded with cover tape 11a from both sides to be integrated, thereby forming a coaxial flat cable 20. The cover tape 11a used was the same as that in Example 1. The coaxial flat cable 20 was cut to a predetermined length, and the terminal portion 21 was processed as shown in Fig. 10 to expose the central conductor 1, the insulator 2, and the outer conductor 3.

The obtained coaxial flat cable 20 was attached to the substrate 30 as shown in FIG. 11. The attachment was performed by soldering the central conductor 1 to the solder connection portion 41 and the outer conductor 3 to the solder connection portion 42.

REFERENCE SIGNS LIST 1 central conductor 1a central conductor tip 2 insulator 2a insulator tip 2A gap 2B inner annular portion 2C outer annular portion 2D connecting portion 2E gap 3 outer conductor 3a outer conductor tip 3A thin wire horizontal winding 3B metal layer-attached insulating tape 4 outer jacket 4A insulating tape 4B adhesive layer 7 metal member 7a metal member tip 9 impedance mismatching portion 10 coaxial cable 10a paired wire 11 resin tape 11a cover tape 11b reinforcing tape 20 coaxial flat cable 21 terminal portion 22 intermediate portion 30 substrate 31 electrode 32 electrode 41 central conductor solder connection portion 42 outer conductor solder connection portion X width direction Y longitudinal direction

Claims (5)

A coaxial flat cable having a plurality of coaxial cables arranged in a line with gaps in the width direction, and a resin tape that is attached to at least one or both sides of the terminal side of the intermediate portion of the coaxial cables other than the terminal portions to integrate at least the terminal portions, in which each of the coaxial cables is terminated and soldered to a board or a connector, characterized in that a metal member is arranged between each of the plurality of coaxial cables in a form that contacts adjacent coaxial cables to ensure the gap, the metal member is arranged in at least a portion that forms a coaxial structure in the longitudinal direction of the coaxial cables , and the metal member is soldered together with the outer conductor of the coaxial cables to a common GND of the board or connector. The coaxial flat cable according to claim 1, wherein the coaxial cable comprises at least a central conductor, an insulator disposed around the central conductor, an outer conductor disposed around the insulator, and an outer jacket disposed around the outer conductor. The coaxial flat cable according to claim 2, wherein the metal member is disposed at least in the portion of the outer circumference of the central conductor where the insulator is provided, and the tip of the metal member is disposed between the tip of the central conductor and the tip side of the peeled portion or the portion to be peeled of the outer conductor. A coaxial flat cable according to any one of claims 1 to 3, in which, when the metal member is a metal wire, the outer diameter of the metal wire is D1 and the outer diameter of the coaxial cable is D2, D1/D2 is within the range of 0.5 to 1.5. The coaxial flat cable according to any one of claims 1 to 4, wherein the resin tape is (a) a cover tape that sandwiches and integrates the middle portion of the coaxial cable from both sides , (b) a reinforcing tape provided on the terminal side of the middle portion of the coaxial cable, or (c) a cover tape that sandwiches and integrates the middle portion of the coaxial cable from both sides and a reinforcing tape attached to one side of the cover tape on the terminal side of the middle portion of the coaxial cable.

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