JP7823488B2 - Shielded Flat Cable - Google Patents

Description

This disclosure relates to a shielded flat cable.

Patent Document 1 discloses a circuit board including one or more ground lines arranged in parallel,
one or more signal lines arranged in parallel to the ground line;
an insulating layer covering the ground line and the signal line;
A shielded flat cable having a shielding layer provided on the outer periphery of the insulating layer,
The disclosed shielded flat cable has, in a cross section perpendicular to the longitudinal direction of the ground wires, a plurality of openings in the insulating layer, each of which has a bottom corresponding to the top and bottom surfaces of one of the ground wires, and the ground wires are electrically connected to the shielding layer in the openings, and the signal wires are surrounded by the ground wires and the shielding layer.

International Publication No. 2019/208247

Flexible flat cables have traditionally been used for internal wiring in various electronic and information devices to save space and provide easy connections.

In flexible flat cables, it is desirable to have a configuration that includes, for example, a signal line that uses a single conductor to transmit signals single-ended, and a signal line that uses a pair of conductors to transmit signals differentially, so that they can accommodate various signal transmission methods.

In addition, signal lines are required to have a specified impedance depending on the components they are connected to.

The present disclosure therefore aims to provide a shielded flat cable containing multiple signal lines with a predetermined impedance.

The shielded flat cable of the present disclosure comprises: a plurality of conductors arranged in parallel;
a first dielectric layer and a second dielectric layer;
a shielding layer;
the plurality of conductors include a first signal line, a second signal line, and a ground line;
The second signal line includes one or more pairs of adjacently arranged conductors, and the ground line is arranged at either end of the plurality of conductors in the arrangement direction.
the first dielectric layer is attached to the upper surfaces of the conductors,
the second dielectric layer is attached to the lower surfaces of the conductors,
the first dielectric layer and the second dielectric layer are bonded together in a region where the conductor is not disposed;
Among the outer surfaces of a dielectric layer including the first dielectric layer and the second dielectric layer, a surface opposite to a surface in contact with any one of the plurality of conductors selected from the first dielectric layer and the second dielectric layer is defined as a first outer surface, a surface opposite to the first outer surface is defined as a second outer surface, and one of two side surfaces orthogonal to the arrangement direction of the plurality of conductors is defined as a first side surface,
the shielding layer is provided on the first outer surface and the first side surface, and is connected at the second outer surface to the ground line disposed at either end of the plurality of conductors in an arrangement direction;
The second outer surface of the dielectric layer is exposed except for a portion of the shielding layer arranged for connection to the ground line.

This disclosure provides a shielded flat cable containing multiple signal lines with a predetermined impedance.

FIG. 1A is a top view of a shielded flat cable according to one embodiment of the present disclosure. FIG. 1B is a bottom view of a shielded flat cable according to one embodiment of the present disclosure. FIG. 2 is a cross-sectional view of a shielded flat cable according to one embodiment of the present disclosure taken along a plane perpendicular to the longitudinal direction. FIG. 3 is a cross-sectional view of a shielded flat cable according to another embodiment of the present disclosure taken along a plane perpendicular to the longitudinal direction. FIG. 4 is an explanatory diagram of a shield layer included in a shielded flat cable according to one embodiment of the present disclosure.

The implementation form is described below.

Description of the embodiments of the present disclosure
First, embodiments of the present disclosure will be listed and described. In the following description, the same or corresponding elements will be denoted by the same reference numerals, and the same description will not be repeated.

(1) A shielded flat cable according to one aspect of the present disclosure includes a plurality of conductors arranged in parallel,
a first dielectric layer and a second dielectric layer;
a shielding layer;
the plurality of conductors include a first signal line, a second signal line, and a ground line;
The second signal line includes one or more pairs of adjacently arranged conductors, and the ground line is arranged at either end of the plurality of conductors in the arrangement direction.
the first dielectric layer is attached to the upper surfaces of the conductors,
the second dielectric layer is attached to the lower surfaces of the conductors,
the first dielectric layer and the second dielectric layer are bonded together in a region where the conductor is not disposed;
Among the outer surfaces of a dielectric layer including the first dielectric layer and the second dielectric layer, a surface opposite to a surface in contact with any one of the plurality of conductors selected from the first dielectric layer and the second dielectric layer is defined as a first outer surface, a surface opposite to the first outer surface is defined as a second outer surface, and one of two side surfaces orthogonal to the arrangement direction of the plurality of conductors is defined as a first side surface,
the shielding layer is provided on the first outer surface and the first side surface, and is connected at the second outer surface to the ground line disposed at either end of the plurality of conductors in an arrangement direction;
The second outer surface of the dielectric layer is exposed except for a portion of the shielding layer arranged for connection to the ground line.

The ground wire is electrically connected to the shielding layer, which is then electrically connected to the ground layer of the board to which the ground wire is connected. Therefore, even if the shielding layer is provided mainly on the first outer surface of the dielectric layer, it is possible to create a shielded flat cable containing multiple signal lines with a predetermined impedance.

(2) In (1) above, the width of the conductor of the first signal line may be wider than the width of the conductor of the second signal line.

The center-to-center distance between adjacent conductors in a shielded flat cable is not particularly limited, but it is preferable that it be constant, for example.

In this case, by making the width of the conductor of the first signal line wider than the width of the first and second conductors of the second signal line, the width between the first signal lines becomes shorter than the width between the conductors of the second signal line. This makes it possible to make the impedance of the first signal line and the second signal line different and achieve the desired value.

(3) In (1) or (2) above, the thickness of the conductor of the first signal line may be thicker than the thickness of the conductor of the second signal line.

Increasing the thickness of the conductor of each signal line can reduce the impedance of that signal line. Therefore, for example, by making the conductor of a first signal line thicker than the conductor of a second signal line, the impedance of the first signal line can be made lower than that of the second signal line, and the impedance of the first signal line and the second signal line can be made different and set to the desired value.

(4) In any of (1) to (3) above, the ground line may be disposed between the first signal line and the second signal line.

By placing a ground line between the first signal line and the second signal line, the first signal line and the second signal line can be surrounded by the ground line and the shielding layer, respectively. This makes the first signal line and the second signal line particularly less susceptible to the effects of external noise and crosstalk.

(5) In any one of the above (1) to (4), the plurality of conductors include power lines,
The ground line may be disposed between the first signal line and the power supply line.

By including a power line, the shielded flat cable can supply power to connected devices, making it suitable for connecting to devices that require a power supply.

[Details of the embodiment of the present disclosure]
Specific examples of a shielded flat cable according to an embodiment of the present disclosure (hereinafter referred to as the "present embodiment") will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.
[Shielded flat cable]
Fig. 1A shows a top view of the shielded flat cable 10 according to this embodiment, and Fig. 1B shows a bottom view of the shielded flat cable 10 according to this embodiment. Fig. 2 shows a cross-sectional view of the shielded flat cable 10 according to this embodiment taken along line A-A' in Fig. 1A, taken along a plane perpendicular to the longitudinal direction.

Figure 3 is a cross-sectional view of a modified shielded flat cable according to this embodiment, taken along a plane perpendicular to the longitudinal direction.

Figure 4 is an explanatory diagram of an example of the shield layer configuration.

As mentioned above, Figure 3 is a modified example, so the following explanation will be primarily based on Figures 1A, 1B, and 2, with Figure 3 used as needed.

In Figures 1A to 3, the X axis corresponds to the longitudinal direction of the shielded flat cable and the multiple conductors, the Y axis corresponds to the width direction of the shielded flat cable and also corresponds to the arrangement direction of the multiple conductors. The Z axis corresponds to the thickness direction of the shielded flat cable and also corresponds to the stacking direction of the multiple conductors and dielectric layers.

For ease of explanation, in this specification, the surface located above the Z axis in Figures 1A to 3 may be referred to as the upper surface, and the surface located below as the lower surface. However, when using a shielded flat cable, the orientation of use will vary depending on the device to which it is connected, and the above notation is not intended to limit use to situations where the upper surface is located above the lower surface.

Furthermore, the drawings are schematic diagrams used to explain the arrangement of each component of the shielded flat cable of this embodiment, and do not accurately show the size ratios of each component, etc.

Figures 1A and 1B show the state in which the ends of the conductor 20 of the shielded flat cable 10 are exposed at the first end 10A and second end 10B, which are the longitudinal ends of the shielded flat cable 10 of this embodiment. Note that the portions of the second dielectric layer 12B at the first end 10A and second end 10B in Figure 1B that correspond to the areas where the conductor 20 is exposed on the top surface as shown in Figure 1A are hatched differently from the other portions.

As described above, at the first end 10A and the second end 10B of the shielded flat cable 10, the conductor 20 of the shielded flat cable 10 is exposed from the dielectric layer 12 (described below) in order to connect to equipment, etc. In Figures 1A and 1B, the conductor 20 is shown exposed on the top surface of the shielded flat cable 10, but this is not a limitation. For example, the conductor 20 may be exposed on the top surface at the first end 10A and on the bottom surface at the second end 10B. Alternatively, the dielectric layer surrounding the conductor 20 may be completely removed at either or both of the first end 10A and the second end 10B, exposing the conductor 20 on both the top and bottom surfaces. A connector, etc., may be connected to the exposed conductor 20.

As shown in FIG. 2 , the shielded flat cable 10 of this embodiment includes a plurality of conductors 20 , a dielectric layer 12 , and a shielding layer 13 .
(1) Components of the Shielded Flat Cable Each component will be described below.
(1-1) Conductors As shown in Fig. 2, the shielded flat cable 10 has a plurality of conductors 20. The plurality of conductors 20 are arranged in parallel along the Y axis in Fig. 2.

The plurality of conductors 20 may include first signal lines 22A and 22B, a second signal line 23, and ground lines 21A, 21B, and 21C.
(Conductor configuration)
The multiple conductors 20 can be one or more types selected from flat conductors (rectangular conductors), round conductors, and flat conductors. The flat conductor refers to a conductor having a rectangular cross section perpendicular to the longitudinal direction. The flat conductor can be, for example, a conductor whose thickness is shorter than its width in a cross section perpendicular to the longitudinal direction. The round conductor refers to a conductor whose circular cross section perpendicular to the longitudinal direction. The flat conductor refers to a conductor whose sectional shape perpendicular to the longitudinal direction is a flattened circle, for example, an ellipse. The flat conductor can be, for example, a conductor whose thickness is shorter than its width in a cross section perpendicular to the longitudinal direction.

The material of the conductor 20 is not particularly limited, but examples include copper. The copper may be one or more types selected from soft copper and copper alloys. The surface of the conductor 20 may be plated; for example, the copper may be plated with nickel, tin, or silver.

The size of the conductor 20 is not particularly limited, but for example, in the case of a flat conductor, the thickness is preferably 10 μm to 100 μm and the width is preferably 0.2 mm to 0.8 mm. In the case of a round conductor, the outer diameter is preferably 25 μm to 500 μm. As described below, for example, the first signal conductors 22A, 22B and the second signal conductor 23 may have different thicknesses and widths. In other words, the shielded flat cable 10 may include conductors 20 with different thicknesses and widths. Furthermore, the shielded flat cable 10 may include conductors 20 with different cross-sectional shapes perpendicular to the longitudinal direction, such as flat conductors and round conductors.

The conductors 20 can be arranged so that the pitch between them is, for example, 0.5 mm to 1.0 mm. The pitch between the conductors 20 means the distance between the centers of the conductors 20, specifically the distance between the centers of the conductors 20 in the width direction.
(first signal line)
The first signal lines 22A and 22B are single-ended lines that perform single-ended transmission, transmitting signals through a single conductor 20. While Fig. 2 shows the shielded flat cable 10 having two first signal lines 22A and 22B, the shielded flat cable 10 is not limited to this configuration. The shielded flat cable 10 may have only one first signal line, or may have three or more first signal lines.
(Second signal line)
The second signal line 23 is a differential transmission line that performs differential transmission. Therefore, the second signal line 23 can have a configuration including a pair of adjacently arranged conductors, a first conductor 23A and a second conductor 23B. Therefore, the second signal line 23 can include one or more pairs of adjacently arranged conductors.

2 shows an example in which the shielded flat cable 10 has one pair of second signal wires 23, but the present invention is not limited to this. The shielded flat cable 10 may also have two or more pairs of second signal wires 23.
(Ground wire)
The ground line can be arranged at either end in the arrangement direction of the conductors 20. The ground line may also be arranged between the first signal lines 22A and 22B and the second signal line 23.

Figure 2 shows an example in which ground lines 21A and 21C are arranged at the ends of the multiple conductors 20 in the arrangement direction, and ground line 21B is arranged between first signal lines 22A and 22B and second signal line 23. However, the arrangement of the ground lines is not limited to the form shown in Figure 2.

In the shielded flat cable 10 shown in Figure 2, only one of the ground wires 21A and 21C may be used as the ground wire. Also, two or more of the ground wires 21A to 21C may be used as the ground wire.

Ground lines 21A, 21B, and 21C are typically electrically connected to the ground layer of the circuit board of the device to which the shielded flat cable 10 is connected.

By arranging the ground lines 21A and 21C at either end of the multiple conductors 20 in the arrangement direction, the first signal lines 22A and 22B and the second signal line 23 can be surrounded by the ground lines and the shielding layer. This makes the first signal lines 22A and 22B and the second signal line 23 less susceptible to external noise and crosstalk.

2, the ground line 21B may be disposed between the first signal lines 22A, 22B and the second signal line 23. By disposing the ground line 21B between the first signal lines 22A, 22B and the second signal line 23, the first signal lines 22A, 22B and the second signal line 23 can be disposed so as to be surrounded by the ground line and the shielding layer, respectively. This makes it possible to make the first signal lines 22A, 22B and the second signal line 23 particularly less susceptible to the effects of external noise and crosstalk.
(power line)
As shown in Fig. 3, in the shielded flat cable 110, the multiple conductors 20 may also include power lines 31A and 31B. The power lines 31A and 31B are conductors for supplying power to electronic/electrical devices and electronic components to which the shielded flat cable 110 shown in Fig. 3 is connected. The power lines 31A and 31B may also have the same conductor configuration as that described for the first signal lines 22A and 22B. The thickness and width of the power lines 31A and 31B can be selected so that the cross-sectional area corresponds to the magnitude of the current to be carried. Note that if power lines are not required, the power lines 31A and 31B may not be provided, as in the shielded flat cable 10 shown in Fig. 2.

By including power lines 31A and 31B, the shielded flat cable 110 can supply power to connected devices, making it suitable for connecting to devices that require a power supply.

If the shielded flat cable 110 has power lines 31A and 31B, the ground line 21B can be placed between the first signal lines 22A and 22B and the power lines 31A and 31B.

By arranging the ground line 21B, the first signal lines 22A and 22B can be arranged so as to be surrounded by the ground line 21B and the shielding layer 13. This makes it possible to make the first signal lines 22A and 22B less susceptible to the effects of external noise and crosstalk.
(1-2) Dielectric Layer The shielded flat cable 10 can have a first dielectric layer 12A and a second dielectric layer 12B. The first dielectric layer 12A can be attached to the upper surfaces of the multiple conductors 20. The second dielectric layer 12B can be attached to the lower surfaces of the multiple conductors 20. The first dielectric layer 12A and the second dielectric layer 12B can be attached to each other in direct contact in areas where the conductors 20 are not present.

The upper and lower surfaces of the conductor 20 refer to, for example, the upper surface 211 and the lower surface 212 in the case of the ground line 21C in Figure 2, and refer to the upper and lower surfaces along the stacking direction of the multiple conductors 20 and the dielectric layer 12, i.e., along the Z axis.

As described below, the shielding layer 13 can be connected at the second outer surface 1202 of the dielectric layer 12 to a ground line located at either end along the Y axis, which is the arrangement direction of the multiple conductors 20. Therefore, the dielectric layer 12 is not disposed on at least a portion of the top surface 211 of either of the ground lines 21A, 21C connected to the shielding layer 13, and at least a portion of the ground line can be exposed.

The configuration of the dielectric layer 12 is not particularly limited, and the thickness and configuration of the dielectric layer 12 can be selected depending on, for example, the magnitude of impedance required for the signal wires of the shielded flat cable. The dielectric layer 12 can include one or more types selected from, for example, the substrate, adhesive layer, and interposer described below.

In the following description, of the outer surfaces of the dielectric layer 12 including the first dielectric layer 12A and the second dielectric layer 12B, the surface of either the first dielectric layer 12A or the second dielectric layer 12B opposite to the surface that contacts the multiple conductors 20 is referred to as the first outer surface 1201. Figure 2 shows an example in which the surface of the second dielectric layer 12B opposite to the surface that contacts the multiple conductors 20 is referred to as the first outer surface 1201.

Furthermore, of the outer surfaces of the dielectric layer 12, the surface opposite the first outer surface 1201 is referred to as the second outer surface 1202. Of the two outer surfaces of the dielectric layer 12 that are perpendicular to the Y axis, which is the arrangement direction of the multiple conductors 20, the side closest to the ground line is referred to as the first side 1203. The surface opposite the first side 1203 is referred to as the second side 1204. The side closest to the ground line means the side that is closest to the ground line provided at either end of the multiple conductors 20. As shown in Figure 2, when ground lines 21A and 21C are provided at both ends of the multiple conductors 20, the side closest to the ground line 21A connected to the shielding layer 13 is referred to as the first side 1203.

For example, as shown in FIG. 2, the dielectric layer 12 can be constructed by bonding a substrate having an adhesive layer on the inner adhesive surface. In this case, each dielectric layer can include a substrate and an adhesive layer. Specifically, as shown in FIG. 2, the first dielectric layer 12A can include a first substrate 121A and a first adhesive layer 122A. The first adhesive layer 122A bonds the top surface of the conductor 20 to the first substrate 121A.

The second dielectric layer 12B can include a second base material 121B and a second adhesive layer 122B. The second adhesive layer 122B bonds the lower surface of the conductors 20 to the second base material 121B. The first dielectric layer 12A and the second dielectric layer 12B can be bonded together and integrated by, for example, sandwiching the plurality of conductors 20 between them, with the adhesive layers of the dielectric layers facing each other, and bonding them while applying heat with a heating roller.
(Base material)
It is preferable to use a resin film with excellent flexibility for the first substrate 121A and the second substrate 121B (hereinafter collectively referred to as "substrate"). Therefore, the substrate material can be one or more selected from, for example, polyester resin, polyphenylene sulfide resin, polyimide resin, etc. Examples of polyester resin include resin materials such as polyethylene terephthalate resin, polyethylene naphthalate resin, and polybutylene naphthalate resin. The thickness of each substrate can be, for example, 9 μm or more and 400 μm or less. The thickness and material of the first substrate 121A and the second substrate 121B may be different or the same.
(Adhesive layer)
Examples of materials for the first adhesive layer 122A and the second adhesive layer 122B (hereinafter collectively referred to as "adhesive layers") include polyester-based resins and polyolefin-based resins. Examples of polyolefin-based resins include polypropylene. The adhesive layers may also contain additives such as flame retardants as needed. The thickness of each adhesive layer may be, for example, 10 μm or more and 200 μm or less. The thickness and material of the first adhesive layer 122A and the second adhesive layer 122B may be different or the same.
(intervention)
The dielectric layer 12 may also have intervening layers to adjust the thickness of the dielectric layer 12 and adjust the impedance of the conductor 20 .

Examples of materials for the filler include polyester resins and polyolefin resins. Examples of polyolefin resins include polypropylene. The filler may contain additives such as flame retardants as needed. The thickness of the filler can be selected depending on the impedance required for the conductor.

2 and 3 show a configuration in which the dielectric layer 12 has a base material and an adhesive layer, but the present invention is not limited to such a configuration. For example, the dielectric layer 12 may be configured not to be adhered to the conductor 20, in which case the dielectric layer 12 may not include an adhesive layer. The dielectric layer 12 may also be configured not to include a base material.
(1-3) Shield layer (Shield layer configuration)
The shielded flat cable 10 of this embodiment may have a shielding layer 13 disposed outside the dielectric layer 12 .

The shielding layer 13 can be arranged outside the dielectric layer 12, specifically on its outer surface. The shielding layer 13 is provided on the first outer surface 1201 and the first side surface 1203 of the dielectric layer 12. Furthermore, the shielding layer 13 can be connected on the second outer surface 1202 of the dielectric layer 12 to a ground line, such as ground line 21A or ground line 21C, arranged at either end along the Y axis, which is the arrangement direction of the multiple conductors 20.

For this reason, the shield layer 13 can have a first shield layer 13A provided on a portion of the second outer surface 1202 of the dielectric layer 12, a second shield layer 13B covering the first outer surface 1201, and a third shield layer 13C covering the first side surface 1203.

The first shielding layer 13A, second shielding layer 13B, and third shielding layer 13C can be continuous layers. In other words, the shielding layer 13 can be formed by folding a single shielding layer and arranging it along the outer shape of the dielectric layer 12.

The shielding layer 13 may include a metal layer, and may have a structure in which a resin layer 401 and a metal layer 402 are stacked, as shown in Figure 4. Note that Figure 4 is a cross-sectional view of the shielding layer 13 taken along the direction in which the resin layer 401 and the metal layer 402 are stacked.

The resin contained in the resin layer 401 is not particularly limited as long as it is a material that can support the metal layer 402, but examples include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN).

The metal layer 402 can be, for example, a metal foil or a metal vapor deposition film formed on the resin layer 401. The material for the metal layer 402 can be any conductive material, but copper or aluminum, which are relatively inexpensive and have excellent conductivity, are suitable.

The thickness of each shield layer 13 is not particularly limited, but can be, for example, 200 pm or more and 200 μm or less. The first shield layer 13A, second shield layer 13B, and third shield layer 13C may have different thicknesses and materials, or they may be the same.

Each shield layer 13 can be positioned so that the first surface 41A on which the metal layer 402 is arranged faces inward, i.e., facing the multiple conductors 20. Therefore, the second surface 41B on which the resin layer 401 is arranged is located on the outside of the shielded flat cable 10 and can be the surface exposed to the outside. An adhesive layer can also be provided between the metal layer 402 and the dielectric layer 12, if necessary.

As described above, the shield layer 13 can be connected at its second outer surface 1202 to the ground line 21A or ground line 21C located at either end along the Y axis, which is the arrangement direction of the multiple conductors 20. Figure 2 shows an example configuration in which the first shield layer 13A and the ground line 21A are connected. Therefore, it is preferable to place a conductive adhesive at least between the top surface 211 of the ground line 21A and the first shield layer 13A so that the first shield layer 13A and the ground line 21A can be electrically connected. Note that, from the perspective of improving workability, all of the adhesive placed between the shield layer 13 and the dielectric layer 12 may be a conductive adhesive.

The width of the ground line 21A connected to the shielding layer 13 can be selected to ensure a sufficient adhesive area between the ground line 21A and the shielding layer 13. Specifically, for example, the width of the ground line 21A can be made wider than the other ground lines 21B and 21C.

The ground line 21A is electrically connected to the shielding layer 13, which is then electrically connected to the ground layer of the substrate to which the ground line 21A is connected. Therefore, even if the shielding layer 13 is provided mainly only on the first outer surface 1201 of the dielectric layer 12, i.e., on only one side, it is possible to create a shielded flat cable 10 containing multiple signal lines with a predetermined impedance.

It is sufficient that at least a portion of the ground line 21A connected to the shield layer 13 is connected to the shield layer 13. Therefore, for example, only a portion of the top surface 211 of the ground line 21A may be exposed from the dielectric layer 12, and only this exposed portion may be connected to the shield layer 13.

Like the other conductors 20, the ground wire 21A can be provided along the entire length of the shielded flat cable 10, which is the X-axis, or the longitudinal direction of the cable. However, the ground wire 21A only needs to be configured to include the exposed conductor 20 portions at the first end 10A and second end 10B, which are the longitudinal ends of the cable 10, and to be able to connect to the shielding layer 13. For this reason, the ground wire 21A can be provided, for example, only between the exposed conductor 20 portions at the first end 10A and second end 10B and the connection portions with the shielding layer 13, and not along the entire length of the shielded flat cable 10, which is the X-axis, or the longitudinal direction of the cable 10.

A first shield layer 13A, which is a shield layer 13, can be disposed on the second outer surface 1202 of the dielectric layer 12 to the extent necessary for connection to the ground line 21A. Therefore, the second outer surface 1202 of the dielectric layer 12 can be configured to be exposed except for the portion of the first shield layer 13A, which is a shield layer 13 disposed for connection to the ground line. In other words, the shield layer 13 has an opening 11 on the second outer surface 1202.

In Figures 1A and 1B, the positions of the first end 131 and second end 132 of the shielding layer 13 in the longitudinal direction of the shielded flat cable 10 are not particularly limited. For example, the positions can be selected depending on the dimensional tolerance of the metal film used to form the shielding layer 13.

Therefore, the first end 131 and the second end 132 of the shield layer 13 in the longitudinal direction of the shielded flat cable 10 may be located at the same positions as, for example, the first end 120A and the second end 120B of the dielectric layer 12. Also, as shown in Figures 1A and 1B, the first end 131 and the second end 132 of the shield layer 13 in the longitudinal direction of the shielded flat cable 10 may be located inwardly of, and different from, the first end 120A and the second end 120B of the dielectric layer 12. The first end 120A and the second end 120B of the dielectric layer 12 refer to the ends of the dielectric layer 12 excluding the portions where the conductors 20 are exposed.
(2) Regarding the impedance of the signal lines and the configuration of each signal line, the single-ended lines that are the first signal lines 22A and 22B may be required to have a smaller impedance than the differential transmission line that is the second signal line 23.

Specifically, the single-ended lines that make up the first signal lines 22A and 22B may be required to have an impedance of, for example, 50 Ω or 75 Ω. Furthermore, the differential transmission line that makes up the second signal line 23 may be required to have an impedance of, for example, 80 Ω or more and 125 Ω or less.

Therefore, in order to set the impedance of the first signal lines 22A, 22B and the second signal line 23 to the desired value, it is also possible to select the arrangement of the first signal lines 22A, 22B and the second signal line 23, the size of the conductor 20, etc. For example, the first signal lines 22A, 22B and the second signal line 23 may be configured such that the lengths of each part in a cross section perpendicular to the longitudinal direction or the cross-sectional area of the conductor are different.
(conductor width, thickness)
The width W22 of the conductor 20 of the first signal lines 22A and 22B may be different from the width W23 of the conductor 20 of the second signal line 23. For example, the width W22 of the conductor 20 of the first signal lines 22A and 22B may be wider than the width W23 of the conductor 20 of the second signal line 23.

The center-to-center distance between adjacent conductors 20 in the shielded flat cable of this embodiment is not particularly limited, but is preferably constant. Therefore, for example, it is preferable that the center-to-center distance P1 between the conductors 20 of the first signal lines 22A and 22B and the center-to-center distance P2 between the first conductor 23A and the second conductor 23B that make up the second signal line 23 be P1 = P2.

In this case, by making the width W22 of the conductors 20 of the first signal lines 22A and 22B wider than the width W23 of the first conductors 23A and second conductors 23B of the second signal line 23, the width W1 between the first signal lines 22A and 22B becomes shorter than the width W2 between the conductors 20 of the second signal line 23. As a result, the impedance of the first signal lines 22A and 22B is made smaller than that of the second signal line 23, and the impedance of the first signal lines 22A and 22B and the second signal line 23 can be made different and set to the desired value.

Furthermore, the thickness T22 of the conductor 20 of the first signal lines 22A and 22B may be different from the thickness T23 of the conductor 20 of the second signal line 23. For example, the thickness T22 of the conductor 20 of the first signal lines 22A and 22B may be thicker than the thickness T23 of the conductor 20 of the second signal line 23.

Increasing the thickness of the conductor 20 of each signal line can reduce the impedance of that signal line. Therefore, for example, by making the thickness T22 of the conductor 20 of the first signal lines 22A and 22B thicker than the thickness T23 of the conductor 20 of the second signal line 23, the impedance of the first signal lines 22A and 22B can be made lower than that of the second signal line 23. The impedance of the first signal lines 22A and 22B and the second signal line 23 can then be made different and set to the desired value.

The present invention will be explained below by giving specific examples, but the present invention is not limited to these examples.
(1) Evaluation Method The impedance was calculated for the first signal line and the second signal line of the shielded flat cable produced in the following experimental example.
(2) Conditions for Producing Shielded Flat Cable The following describes the conditions and results of Experimental Example 1. The following Experimental Example 1 is an example of the present invention.
[Experimental Example 1]
A shielded flat cable 110 was fabricated whose cross section perpendicular to the longitudinal direction has the structure shown in Fig. 3. The fabricated shielded flat cable has an upper surface and a lower surface having the structures shown in Figs. 1A and 1B, respectively.

That is, the manufactured shielded flat cable 110 has a plurality of conductors 20 arranged in parallel, a dielectric layer 12 including a first dielectric layer 12A and a second dielectric layer 12B, and a shielding layer 13 arranged outside the dielectric layer 12.
(conductor)
The conductors 20 were flat conductors made of copper. The conductors 20 were arranged so that the center-to-center distance between adjacent conductors 20 was equal, and the center-to-center distance between adjacent conductors 20 was 0.5 mm. Therefore, for example, the center-to-center distance P1 (see FIG. 2 ) between the conductors 20 of the first signal lines 22A and 22B and the center-to-center distance P2 between the first conductors 23A and the second conductors 23B that make up the second signal line 23 were P1 = P2 = 0.5 mm.

The multiple conductors 20 include first signal lines 22A and 22B, a second signal line 23 including a pair of adjacently arranged conductors 20, ground lines 21A, 21B, and 21C, and power lines 31A and 31B.

The multiple conductors 20 were arranged as shown in Figure 3.

The width and thickness of each conductor 20 are as shown in Table 1. In Table 1, ground line 21A is referred to as the first ground line, ground line 21B as the second ground line, and ground line 21C as the third ground line. The two first signal lines 22A and 22B have the same configuration, so they are listed together in the first signal line column. The first conductor 23A and second conductor 23B of second signal line 23 also have the same configuration, so they are listed together in the second signal line column.

(Dielectric layer)
A first dielectric layer 12A and a second dielectric layer 12B are bonded to the upper and lower surfaces of the plurality of conductors 20 to form the dielectric layer 12. The first dielectric layer 12A and the second dielectric layer 12B are bonded together in direct contact in areas where the conductors 20 are not placed.

The first dielectric layer 12A and the second dielectric layer 12B each have a first substrate 121A and a second substrate 121B, and a first adhesive layer 122A and a second adhesive layer 122B. The first substrate 121A and the second substrate 121B were made of polyethylene terephthalate with a thickness of 12 μm. The first adhesive layer 122A and the second adhesive layer 122B were made of polypropylene, with the first adhesive layer 122A being 40 μm thick and the second adhesive layer 122B being 140 μm thick.

The dielectric layer 12 is not provided on the upper surface 211 of the ground line 21A, and the ground line 21A is exposed.
(Shield layer)
A shield layer 13 was disposed outside the dielectric layer 12 .

Specifically, as shown in FIG. 2, the shielding layer 13 is provided on the first outer surface 1201 and the first side surface 1203 of the dielectric layer 12. Furthermore, the shielding layer 13 is connected on the second outer surface 1202 to a ground line 21A located at the end of the multiple conductors 20 in the Y-axis direction, which is the arrangement direction of the conductors 20.

For this reason, the shield layer 13 is configured to include a first shield layer 13A provided on a portion of the second outer surface 1202 of the dielectric layer 12, a second shield layer 13B covering the first outer surface 1201, and a third shield layer 13C covering the first side surface 1203. The second outer surface 1202 of the dielectric layer 12 is exposed except for the portion covered by the first shield layer 13A, and the shield layer 13 is configured to have an opening 11 in the second outer surface 1202.

As shown in Figure 4, the shielding layer 13 has a laminated structure of a resin layer 401 and a metal layer 402, with the resin layer 401 made of polyethylene terephthalate (PET) and the metal layer 402 made of aluminum foil. Each shielding layer 13 was positioned so that the first surface 41A, on which the metal layer 402 was arranged, faced inward, i.e., facing the multiple conductors 20. A conductive adhesive was applied to the surface of the shielding layer 13 facing the dielectric layer 12, and the shielding layer 13 was adhered to the dielectric layer 12. The shielding layer 13 was also electrically connected to the ground line 21A.

The impedances of the first signal wires 22A and 22B of the resulting shielded flat cable 110 were 48.9 Ω and 49.5 Ω, respectively, and the impedance of the second signal wire 23 was 90 Ω. In other words, a shielded flat cable was obtained that included signal wires with predetermined impedances, and in particular signal wires with different impedances. Furthermore, since the target impedance values for the first signal wires 22A and 22B were 50 Ω and the target impedance value for the second signal wire 23 was 90 Ω, a shielded flat cable was obtained that included conductors with impedances that met the target values.

10, 110 Shielded flat cable 10A First end 10B Second end 11 Opening 12 Dielectric layer 1201 First outer surface 1202 Second outer surface 1203 First side 1204 Second side 12A First dielectric layer 121A First substrate 122A First adhesive layer 12B Second dielectric layer 121B Second substrate 122B Second adhesive layer 120A First end 120B Second end 13 Shield layer 13A First shield layer 13B Second shield layer 13C Third shield layer 131 First end 132 Second end 401 Resin layer 402 Metal layer 20 Conductor 21A, 21B, 21C Ground line 211 Upper surface 212 Lower surface 22A, 22B First signal line 23 Second signal line 23A First conductor 23B Second conductor P1, P2 Center-to-center distances T22, T23 Thickness W1, W2 Width W22, W23 Width 31A, 31B Power line 41A First surface 41B Second surface

Claims (4)

A plurality of conductors arranged in parallel;
a first dielectric layer and a second dielectric layer;
a shielding layer;
the plurality of conductors include a first signal line, a second signal line, and a ground line;
the width of the conductor of the first signal line is wider than the width of the conductor of the second signal line;
the second signal line includes one or more pairs of adjacently arranged conductors ,
the ground line is disposed at either end of the plurality of conductors in the arrangement direction,
the first dielectric layer is attached to the upper surfaces of the conductors,
the second dielectric layer is attached to the lower surfaces of the conductors,
the first dielectric layer and the second dielectric layer are bonded together in a region where the conductor is not disposed;
Among the outer surfaces of a dielectric layer including the first dielectric layer and the second dielectric layer, a surface opposite to a surface in contact with any one of the plurality of conductors selected from the first dielectric layer and the second dielectric layer is defined as a first outer surface, a surface opposite to the first outer surface is defined as a second outer surface, and one of two side surfaces orthogonal to the arrangement direction of the plurality of conductors is defined as a first side surface,
the shielding layer is provided on the first outer surface and the first side surface, and is connected at the second outer surface to the ground line disposed at either end of the plurality of conductors in an arrangement direction;
A shielded flat cable in which the second outer surface of the dielectric layer is exposed except for a portion of the shielding layer that is positioned for connection to the ground wire. A plurality of conductors arranged in parallel;
a first dielectric layer and a second dielectric layer;
a shielding layer;
the plurality of conductors include a first signal line, a second signal line, and a ground line;
the thickness of the conductor of the first signal line is greater than the thickness of the conductor of the second signal line;
the second signal line includes one or more pairs of adjacently arranged conductors,
the ground line is disposed at either end of the plurality of conductors in the arrangement direction,
the first dielectric layer is attached to the upper surfaces of the conductors,
the second dielectric layer is attached to the lower surfaces of the conductors,
the first dielectric layer and the second dielectric layer are bonded together in a region where the conductor is not disposed;
Among the outer surfaces of a dielectric layer including the first dielectric layer and the second dielectric layer, a surface opposite to a surface in contact with any one of the plurality of conductors selected from the first dielectric layer and the second dielectric layer is defined as a first outer surface, a surface opposite to the first outer surface is defined as a second outer surface, and one of two side surfaces orthogonal to the arrangement direction of the plurality of conductors is defined as a first side surface,
the shielding layer is provided on the first outer surface and the first side surface, and is connected at the second outer surface to the ground line disposed at either end of the plurality of conductors in an arrangement direction;
A shielded flat cable in which the second outer surface of the dielectric layer is exposed except for a portion of the shielding layer that is positioned for connection to the ground wire. A shielded flat cable as described in claim 1 or claim 2, wherein the ground wire is disposed between the first signal wire and the second signal wire. the plurality of conductors include power lines,
3. The shielded flat cable according to claim 1, wherein the ground wire is disposed between the first signal wire and the power supply wire.