Method for manufacturing flat cables

Abstract

To reduce the costs and labor required for manufacturing flat cables. [Solution] A method for manufacturing a flat cable according to one embodiment includes a preparation step of preparing a plurality of coaxial wires 10, each having an outer surface 11 formed by a horizontally wound tape 20; an arrangement step of arranging the plurality of coaxial wires 10 parallel to each other and bringing the outer surfaces 11 of adjacent coaxial wires 10 into contact with each other; and a fixing step of integrating the plurality of coaxial wires 10 by bonding adjacent coaxial wires 10 to each other. In the fixing step, the adhesive forming the adhesive layer on the back surface of the tape 20 is softened by heat or a solvent and seeped out onto the outer surface 11 of the coaxial wires 10 from between the overlapping tapes 20.

Description

Technical Field

[0006] , , , , , , ,

[0001] The present invention relates to a method for manufacturing a flat cable.

Background Art

[0002] There is known a flat cable having a plurality of coaxial lines or coaxial cables arranged in parallel and integrated. Patent Document 1 describes a flat cable having a plurality of coaxial cables arranged in parallel and a tape for fixing those coaxial cables.

[0003] The flat cable as described above is manufactured, for example, as follows. First, a plurality of coaxial lines are arranged in parallel at a predetermined pitch using a jig. Next, the plurality of coaxial lines arranged at the predetermined pitch are fixed to each other using a tape.

[0004] More specifically, two laminated tapes provided with an adhesive layer on one surface are prepared. Next, the adhesive layer of one laminated tape is attached to the outer peripheral surfaces of the plurality of coaxial lines arranged on the jig. Then, the plurality of coaxial lines are taken out from the jig and inverted up and down (front and back). Next, the adhesive layer of the other laminated tape is attached to the outer peripheral surfaces of the plurality of coaxial lines.

[0005] That is, the plurality of coaxial lines are sandwiched between two laminated tapes. Then, one side in the radial direction of each coaxial line is adhered to one laminated tape, and the other side in the radial direction of each coaxial line is adhered to the other laminated tape. As a result, the plurality of coaxial lines are fixed to each other and integrated. Then, the ends of the adhesive layers of both laminated tapes protruding outside both outer sides of the plurality of coaxial lines are bonded together.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] Manufacturing flat cables required jigs and tape. Furthermore, it involved processes such as arranging multiple coaxial cables on a jig and applying tape to these coaxial cables. Therefore, there is a need to reduce the costs and labor involved in manufacturing flat cables. [Means for solving the problem]

[0008] A method for manufacturing a flat cable according to one embodiment includes a preparation step of preparing a plurality of coaxial wires whose outer surfaces are formed by a horizontally wound tape; an arrangement step of arranging the plurality of coaxial wires parallel to each other and bringing the outer surfaces of adjacent coaxial wires into contact with each other; and a fixing step of integrating the plurality of coaxial wires by bonding adjacent coaxial wires to each other. In the fixing step, the adhesive forming the adhesive layer on the back surface of the tape is softened by heat or a solvent and seeped out onto the outer surfaces of the coaxial wires from between the overlapping tapes. [Effects of the Invention]

[0009] According to the present invention, it is possible to reduce the costs and man-hours required for manufacturing flat cables. [Brief explanation of the drawing]

[0010] [Figure 1] This is a plan view of a flat cable. [Figure 2] This is a cross-sectional view of the flat cable along line XX in Figure 1. [Figure 3] This is an explanatory diagram showing the structure of a coaxial cable. [Figure 4] This is an explanatory diagram showing the tape that forms the jacket. [Figure 5] This is a partially enlarged cross-sectional view of the tape along the YY line in Figure 4. [Figure 6] This is a schematic diagram showing a portion of the outer surface of two adjacent coaxial lines. [Figure 7] This is a process diagram showing the manufacturing method of a flat cable. [Modes for carrying out the invention]

[0011] An embodiment of the present invention will be described below. In all drawings used to illustrate the embodiment, the same or substantially identical components and elements will be denoted by the same reference numerals. Furthermore, components and elements that have already been described will not be described again in principle.

[0012] (First Embodiment) <Overview of Flat Cables> Figure 1 is a plan view of the flat cable 1A according to this embodiment. Figure 2 is a cross-sectional view of the flat cable 1A along line XX in Figure 1. The applications of the flat cable 1A are not particularly limited. For example, the flat cable 1A can be used as internal wiring for medical equipment. More specifically, the flat cable 1A can be used as internal wiring for ultrasound probes, endoscopes, etc. The flat cable 1A can also be used as internal wiring for small electronic devices such as laptop computers and tablet terminals.

[0013] The flat cable 1A has multiple coaxial cables 10. In other words, the flat cable 1A is an assembly of multiple coaxial cables 10. There is no particular limit to the number of coaxial cables 10 that make up the flat cable 1A, and they can be increased or decreased as appropriate.

[0014] The coaxial cable that makes up flat cable 1A is sometimes called a "coaxial cable," "cable coaxial core," or "electric wire," but in this specification it will be referred to as a "coaxial cable."

[0015] The plurality of coaxial lines 10 constituting the flat cable 1A are arranged parallel to each other. In other words, in the flat cable 1A, the plurality of coaxial lines 10 are arranged in parallel. In the following description, the arrangement direction of the plurality of coaxial lines 10 constituting the flat cable 1A may be referred to as the "width direction".

[0016] As will be described in detail later, the coaxial lines 10 adjacent to each other in the width direction are in contact with each other and are fixed to each other. More specifically, the outer peripheral surfaces 11 of the coaxial lines 10 adjacent to each other in the width direction are adhered to each other. Viewed from another perspective, the outermost layers of the coaxial lines 10 adjacent to each other in the width direction are adhered to each other.

[0017] In the present embodiment, one connector 2 is provided at each end of the flat cable 1A. Further, one end of all the coaxial lines 10 is connected to one connector 2, and the other end of all the coaxial lines 10 is connected to the other connector 2. However, there is also an embodiment in which a plurality of connectors are provided at one end or both ends of the flat cable 1A.

[0018] For example, in another embodiment, two connectors (first connector, second connector) are provided at one end of the flat cable 1A, and one connector (common connector) is provided at the other end of the flat cable 1A. In this case, on one end side of the flat cable 1A, a part of the plurality of coaxial lines 10 is connected to the first connector, and the remaining part of the plurality of coaxial lines 10 is connected to the second connector. On the other hand, on the other end side of the flat cable 1A, all the coaxial lines 10 are connected to the common connector. There is also an embodiment in which one end of the flat cable 1A is connected to a printed circuit board (edge connector).

[0019] <Coaxial line> FIG. 3 is an explanatory diagram showing the structure of the coaxial line 10. Each coaxial line 10 shown in FIGS. 1 and 2 has a center conductor (inner conductor) 12, an insulator 13, a skin layer 14, an outer conductor 15, and a jacket 16.

[0020] <Center conductor> As shown in Figure 3, the central conductor 12 is a stranded conductor made of multiple metal strands twisted together. More specifically, the central conductor 12 is a stranded conductor made of three copper alloy wires 12a twisted together. The outer diameter of each copper alloy wire 12a is 0.0245 [mm]. In addition, each copper alloy wire 12a is silver-plated.

[0021] The central conductor 12 may be replaced with a stranded conductor (compressed stranded conductor) that has been compressed to have a circular cross-sectional shape. Generally, compressed stranded conductors have a larger contact area between the metal strands, resulting in improved electrical characteristics compared to simple stranded conductors. Therefore, by using a compressed stranded conductor for the central conductor 12, it is expected that the transmission characteristics of the coaxial cable 10 will be further improved.

[0022] Furthermore, from the viewpoint of improving the transmission characteristics and mechanical strength of the coaxial cable 10, it is preferable that the metal strands constituting the stranded conductor or compressed stranded conductor be copper alloy wires containing Sn (tin), Ag (silver), In (indium), Ti (titanium), Mg (magnesium), Fe (iron), etc.

[0023] <insulator> As shown in Figure 3, the insulator 13 is provided around the central conductor 12. Alternatively, the insulator 13 forms an insulating layer around the central conductor 12, covering it. The insulator 13 is made of fluororesin. More specifically, the insulator 13 is made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer).

[0024] However, the insulator 13 may be formed from a fluororesin other than PFA (for example, FEP (tetrafluoroethylene-hexafluoropropylene copolymer)), or from PE (polyethylene) or PP (polypropylene), etc. Furthermore, the insulator 13 may be formed from a foamed resin, or from a resin whose heat resistance has been improved by crosslinking.

[0025] Furthermore, the insulator 13 may have a multilayer structure. For example, the insulator 13 may have a three-layer structure including a first non-foamed layer made of a non-foaming resin, a foamed layer made of a foaming resin and provided around the first non-foamed layer, and a second non-foamed layer made of a non-foaming resin and provided around the foamed layer.

[0026] When the insulator 13 has the multilayer structure described above, cracks are less likely to occur in the insulator 13 when the flat cable 1A is wired in a bent state. Furthermore, when adopting the three-layer structure described above, it is preferable that the thickness of the first non-foamed layer is smaller (thinner) than the thicknesses of the foamed layer and the second non-foamed layer.

[0027] <Skin layer> As shown in Figure 3, the skin layer 14 is provided around the insulator 13 and covers the insulator 13. The skin layer 14 is formed from a tape or film made of PET (polyethylene terephthalate) and has a thickness of 0.005 [mm].

[0028] <External conductor> As shown in Figure 3, the outer conductor 15 is formed from multiple metal strands. More specifically, the outer conductor 15 is formed from multiple copper alloy wires 15a. Each copper alloy wire 15a is tin-plated.

[0029] <Jacket> The jacket 16 shown in Figure 3 is formed by tape wrapped around the outer surface of the outer conductor 15 and forms the outer surface 11 of the coaxial cable 10. For this reason, the jacket 16 is sometimes called a "tape jacket".

[0030] The outer diameter D of the jacket 16 shown in Figure 2 is 0.228 [mm]. As previously described, the outer circumferential surface 11 of the coaxial cable 10 is formed by the jacket 16. Therefore, the outer diameter D of the jacket 16 corresponds to the diameter of the coaxial cable 10. In other words, the diameter of the coaxial cable 10 in this embodiment is 0.228 [mm].

[0031] Figure 4 is an explanatory diagram showing the tape 20 forming the jacket 16. Figure 5 is a partially enlarged cross-sectional view of the tape 20 along the YY line in Figure 4. The tape 20 is a laminate tape having a strip-shaped base material 21 and an adhesive layer 22 provided on one surface of the base material 21.

[0032] The base material 21 is formed in a strip shape from a plastic material. In other words, the base material 21 is a strip-shaped plastic film. More specifically, the base material 21 is made of PET (polyethylene terephthalate). The width W of the base material 21 shown in Figure 4 is 25.0 [mm]. The thickness t1 of the base material 21 shown in Figure 5 is 0.0475 [mm]. However, the material of the base material 21 is not limited to a specific material. Also, the width W and thickness t1 of the base material 21 can be changed as appropriate. Note that the width W of the base material 21 corresponds to the width of the tape 20.

[0033] The adhesive layer 22 is formed by an adhesive applied to one surface of the substrate 21. More specifically, the adhesive layer 22 is formed by a thermosetting acrylic adhesive. The thickness t2 of the adhesive layer 22 shown in Figure 5 is 0.0025 [mm]. That is, the thickness T of the tape 20 is 0.05 (= 0.0475 + 0.0025) [mm]. However, the adhesive forming the adhesive layer 22 is not limited to a specific adhesive. Also, the thickness t2 of the adhesive layer 22 can be changed as appropriate.

[0034] In the following explanation, one side of the substrate 21 on which the adhesive layer 22 is provided may be referred to as the "upper surface of the substrate," and the other side of the substrate 21 may be referred to as the "lower surface of the substrate." Also, one side of the adhesive layer 22 facing the upper surface of the substrate may be referred to as the "lower surface of the adhesive layer," and the other side of the adhesive layer 22 may be referred to as the "upper surface of the adhesive layer."

[0035] Alternatively, one side of the tape 20 is formed by the lower surface of the substrate, and the other side of the tape 20 is formed by the upper surface of the adhesive layer. In the following explanation, the side of the tape 20 formed by the lower surface of the substrate may be referred to as the "front surface 23," and the other side of the tape 20 formed by the upper surface of the adhesive layer may be referred to as the "back surface 24."

[0036] The tape 20 is wrapped around the outer surface of the outer conductor 15 with its back surface 24 facing inward. In other words, the tape 20 is wrapped around the outer surface of the outer conductor 15 with its adhesive layer 22 facing inward. More specifically, the tape 20 is wound horizontally (spiral) around the outer surface of the outer conductor 15. The overlap ratio (wrap width) of the tape 20 is 1 / 3 to 1 / 2.

[0037] As a result, in each coaxial cable 10, a portion of the width direction of the lower tape 20 and a portion of the width direction of the upper tape 20 overlap each other. In other words, in each coaxial cable 10, a portion of the width direction of the later-wound tape 20 overlaps with a portion of the width direction of the earlier-wound tape 20.

[0038] Figure 6 is a schematic diagram showing a portion of the outer surface 11 of two adjacent coaxial lines 10. In the following explanation, one of the two coaxial lines 10 shown in Figure 6 may be referred to as "coaxial line 10a" and the other as "coaxial line 10b" to distinguish them. However, this distinction is merely for the convenience of explanation.

[0039] As previously described, the outer surface 11 of each coaxial cable 10 is formed by a jacket 16. Furthermore, the jacket 16 is formed by a tape 20 that is wound horizontally with an overlap ratio of 1 / 3 to 1 / 2. As a result, a spirally extending winding ridge 25 exists on the outer surface 11 of each coaxial cable 10. This winding ridge 25 is the edge on one side in the width direction of the tape 20 that forms the jacket 16.

[0040] Furthermore, in this embodiment, the positions of the windings 25 of each coaxial cable 10 do not coincide with each other. More specifically, the position of the winding 25 of coaxial cable 10a and the position of the winding 25 of coaxial cable 10b are offset in the longitudinal direction of these coaxial cables 10a and 10b.

[0041] As a result, the winding 25 of the coaxial cable 10a is in contact with the outer surface 11 of the coaxial cable 10b (the surface 23 of the tape 20). Similarly, the winding 25 of the coaxial cable 10b is in contact with the outer surface 11 of the coaxial cable 10a (the surface 23 of the tape 20).

[0042] <Manufacturing method> Next, a method for manufacturing the flat cable 1A according to this embodiment will be described. Figure 7 is a process diagram showing the manufacturing method according to this embodiment. The manufacturing method according to this embodiment includes at least a preparation step S1, an arrangement step S2, and a fixing step S3.

[0043] <Preparation process> In preparation step S1 shown in Figure 7, multiple coaxial cables 10, as shown in Figures 1 and 2, are prepared. The structure of the coaxial cables 10 prepared in preparation step S1 is as previously described.

[0044] <Arrangement Process> In the alignment process S2 shown in Figure 7, the multiple coaxial lines 10 prepared in the preparation process S1 are aligned. More specifically, in the alignment process S2 of this embodiment, the multiple coaxial lines 10 are arranged parallel to each other, and the outer surfaces 11 of adjacent coaxial lines 10 are brought into contact (close contact) with each other. In other words, in the alignment process S2, the multiple coaxial lines 10 are arranged parallel to each other, and the outermost layers of adjacent coaxial lines 10 are brought into contact (close contact) with each other.

[0045] As a result, when the alignment process S2 is performed, the multiple coaxial cables 10 are arranged in parallel at a pitch that is the same as or substantially the same as the diameter of each coaxial cable 10 (the outer diameter D of the jacket 16).

[0046] Alternatively, by preparing coaxial cables 10 having the same diameter as the desired pitch, multiple prepared coaxial cables 10 can be aligned at the desired pitch without using jigs or other fixtures.

[0047] Furthermore, in the arrangement step S2 of this embodiment, multiple coaxial cables 10 are arranged such that the positions of the windings 25 of adjacent coaxial cables 10 do not coincide with each other.

[0048] <Fixed process> In the fixing process S3 shown in Figure 7, the multiple coaxial wires 10 that were aligned in the alignment process S2 are integrated. More specifically, the multiple coaxial wires 10 are integrated by bonding adjacent coaxial wires 10 to each other.

[0049] In the fixing step S3 of this embodiment, the adhesive is dissolved from the adhesive layer 22 of the tape 20 wrapped around each coaxial cable 10, thereby bonding adjacent coaxial cables 10 together.

[0050] More specifically, the adhesive forming the adhesive layer 22 on the back surface 24 of the tape 20 is softened by heat or a solvent and seeped out onto the outer surface 11 of the coaxial cable 10 from between the overlapping tapes 20. In other words, the adhesive forming the adhesive layer 22 is softened by heat or a solvent and seeped out onto the surface 23 of the tape 20 from the winding 25.

[0051] As described above, when the adhesive dissolves onto the outer surface 11 of each coaxial cable 10, the dissolved adhesive adheres adjacent coaxial cables 10 to each other. As a result, all the coaxial cables 10 are fixed to each other and integrated. In other words, in this embodiment, the flat cable 1A is manufactured without using tape or film to fix the coaxial cables 10.

[0052] Here, the multiple coaxial cables 10 are arranged in the previous step (arrangement step S2) so that the positions of the windings 25 of adjacent coaxial cables 10 do not coincide. Therefore, adjacent coaxial cables 10 are bonded to each other by the adhesive seeping out from their respective windings 25. As a result, there are more bonding points and the bonding strength is increased compared to the case where the positions of the windings 25 of adjacent coaxial cables 10 coincide.

[0053] In the fixing process S3, it is required to dissolve the adhesive completely and without deforming or damaging the jacket 16 of the coaxial cable 10. Therefore, when dissolving the adhesive by heat, it is preferable to determine the heating temperature and heating time according to the material of the base material 21 and the type of adhesive forming the adhesive layer 22.

[0054] Specifically, the solid adhesive softens and dissolves upon heating, and then hardens back to a solid state. Therefore, if the heating temperature in the fixing process S3 is too low, the adhesive may not dissolve at all or may dissolve insufficiently. On the other hand, if the heating temperature in the fixing process S3 is too high, the adhesive that dissolves from each of the adjacent coaxial cables 10 may harden before it can spread between them.

[0055] Based on the results of experiments conducted by the inventors of this invention, when the material of the base material 21 is PET (polyethylene terephthalate) and the adhesive is a thermosetting acrylic adhesive, it is preferable in the fixing step S3 to heat the multiple coaxial wires 10 at a temperature of 130 degrees Celsius or higher and 165 degrees Celsius or lower for 8 seconds or higher and 12 seconds or lower. One example of how to carry out the fixing step S3 is to heat the multiple coaxial wires 10 that have gone through the arrangement step S2 in a heating furnace heated to 160 degrees Celsius for about 10 seconds. Another example of how to carry out the fixing step S3 is to pass the multiple coaxial wires 10 that have gone through the arrangement step S2 through the inside of an oven heated to 160 degrees Celsius for 10 seconds.

[0056] Even when dissolving the adhesive with a solvent, it is preferable to determine the type of solvent and processing time according to the material of the base material 21 and the type of adhesive forming the adhesive layer 22. Based on the results of experiments conducted by the inventors, when the material of the base material 21 is PET (polyethylene terephthalate) and the adhesive is an acrylic adhesive, alcohol (ethanol) is preferred as the solvent used in the fixing step S3, and the processing time (immersion time) is preferably 15 seconds or more and 25 seconds or less. An example of a method for carrying out the fixing step S3 is to immerse a plurality of coaxial wires 10 that have gone through the arrangement step S2 in ethanol stored in a processing tank for 20 seconds.

[0057] The present invention is not limited to the embodiments described above, and can be modified in various ways without departing from its spirit. [Explanation of Symbols]

[0058] 1A...Flat cable, 2...Connector, 10, 10a, 10b...Coaxial cable, 11...Outer surface, 12...Center conductor (inner conductor), 12a...Copper alloy wire, 13...Insulator, 14...Skin layer, 15...Outer conductor, 15a...Copper alloy wire, 16...Jacket, 20...Tape, 21...Base material, 22...Adhesive layer, 23...Front surface, 24...Back surface, 25...Wound, D...Outer diameter, S1...Preparation process, S2...Arrangement process, S3...Fixing process, W...Width

Claims

1. A preparation step involves preparing multiple coaxial wires whose outer surfaces are formed by horizontally wound tape, The process involves arranging multiple coaxial lines parallel to each other and bringing the outer surfaces of adjacent coaxial lines into contact with each other, The process includes a fixing step of integrating multiple coaxial wires by bonding adjacent coaxial wires together, A method for manufacturing a flat cable, wherein in the fixing step, the adhesive forming the adhesive layer on the back surface of the tape is softened by heat or a solvent and seeped out from between the overlapping tapes onto the outer surface of the coaxial cable.

2. The method for manufacturing a flat cable according to claim 1, wherein, in the arrangement step, a plurality of coaxial cables are arranged such that the positions of the tape windings on adjacent coaxial cables do not coincide with each other.

3. The tape comprises a base material and the adhesive layer provided on one surface of the base material. The method for manufacturing a flat cable according to claim 1, wherein the adhesive forming the adhesive layer is an acrylic adhesive.

4. The method for manufacturing a flat cable according to claim 3, wherein in the fixing step, a plurality of the coaxial wires are heated at a temperature of 130 degrees Celsius or more and 165 degrees Celsius or less for 8 seconds or more and 12 seconds or less.

5. The method for manufacturing a flat cable according to claim 3, wherein in the fixing step, a plurality of the coaxial wires are immersed in alcohol as the solvent for 15 seconds or more and 25 seconds or less.

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