Shielded thin flat cable and its manufacturing method

Abstract

To provide a shielded thin flat cable having sufficient adhesive strength between a film-like insulator and a conductor, an inner layer electrode, and the other insulator, without melting the other insulator, by heating the film-like insulator to a temperature equal to or higher than the melting point of the other insulator and lower than the melting point of the other insulator. [Solution] A shielded thin flat cable having a conductor (204) made of metal, an insulator (106) that sandwiches the conductor (204) and wraps the conductor (204) other than the conductor electrode (105) that is conductive with the conductor (204) and exposed on the surface, and a metal film (202) that is continuous with the surface of the insulator (106) other than around the conductor electrode (105), wherein the melting point of the second film-shaped insulator (106B) that is bonded to the conductor (204), inner layer electrode (214) and first film-shaped insulator (106A) on the surface of the first film-shaped insulator (106A) on which an inner layer electrode (214) conductive with the conductor (204) and the conductor electrode (105) is formed is set to be 10°C or more lower than the melting point of the first film-shaped insulator.

Description

[Technical field]

[0001] The present disclosure relates to a shielded thin flat cable used for communication and wiring of devices requiring high density mounting and light weight, and a manufacturing method thereof. [Background technology]

[0002] Coaxial cables, which have a core material covered with a shielding layer, are widely used for power supply lines connecting television sets or radio sets to antennas, for connecting measuring instruments, for transmitting audio and video signals, and for wiring high-speed transmission lines also known as high-frequency parts or RF circuits represented by RF circuits inside electronic devices and their surrounding areas.

[0003] Generally, coaxial cables are structured such that a core wire made of copper or the like is wrapped in an insulator such as polyethylene, which is then wrapped in a shielding layer called a braided wire made of thin conductor wires, and finally the outside is covered with a protective coating such as polyvinyl chloride. The braided wire blocks electromagnetic waves from the outside, suppressing noise and attenuation, and also reducing the leakage of electromagnetic waves from the inside. It has a wide transmission frequency range, and can transmit from direct current to millimeter waves (see Non-Patent Document 1).

[0004] On the other hand, in mobile devices and the like, triplate lines are sometimes provided as signal transmission lines for transmitting high-frequency signals in resin multilayer boards made of thermoplastic resin, such as flexible wiring boards for high-density mounting of components in electronic devices and flat cables for wiring through narrow gaps inside devices. A triplate line is a signal transmission line in which a line conductor and a ground conductor are provided on a wiring board, and ground conductors that are wider than the line conductors are arranged opposite both sides of the line conductor (see Patent Documents 1 and 2). As the ground conductors are provided on both sides of the triplate line, it has the characteristic of suppressing noise from the outside and making it less likely to cause a phenomenon called unwanted radiation or unwanted radiation.

[0005] It has been proposed to provide a wiring board that is easy to bend even if a triplate line is provided, and in which deterioration of transmission characteristics is unlikely to occur even when the wiring board is bent (see Patent Document 3).

[0006] To improve the shielding effect, a method has been used in which a metal foil tape is attached to the flat cable to encase the flat cable (see Patent Document 4). However, the short side of such a flat cable exposes the insulator to the outside air, and the exposed insulator is exposed to water vapor, which penetrates into the insulator and causes it to absorb moisture. The absorbed water affects the transmission characteristics. Insulators with a high moisture absorption rate are easily affected by water vapor, and the effect is particularly noticeable in the high frequency range, causing changes in the transmission characteristics.

[0007] There is a method of wrapping shielding tape to strengthen the shielding in the longitudinal direction (see Patent Documents 5 and 6), but this involves wrapping a shielding film as a shielding layer, and gaps and contact resistance occur where the shielding films overlap or contact, making it impossible to achieve complete shielding.Furthermore, overlapping shielding films make the flat cable thicker.Furthermore, at the contacting parts, organic substances such as adhesive and bonding layers are exposed to the outside air, so the insulators absorb moisture.

[0008] The above-mentioned moisture absorption causes the electrical properties of the insulator to change, which in turn changes the transmission properties of the cable. The effect of moisture absorption on the transmission properties is particularly noticeable when handling high-frequency or high-speed signals.

[0009] A flat cable has also been proposed in which a seamless shielding film is formed in the longitudinal direction using copper plating (see Patent Document 7). However, since the short sides are cut into individual pieces, the cross sections are not plated and the conductor and insulator are exposed. In other words, the short end faces are affected by humidity and water vapor penetrates them. Therefore, in this case, for flat cables that require stable transmission characteristics, there are restrictions on the use of highly hygroscopic resins as insulators. Also, in order to connect to other components, new terminals must be formed.

[0010] The recent trend toward higher frequencies in communication, such as 5G communication, and faster transmission speeds in semiconductors has led to a demand for lower loss in transmission lines. Insulators with low transmission loss are also required. For example, general-purpose hydrocarbon resins such as polyethylene, polystyrene, and polypropylene have low transmission loss, are easy to process, and are inexpensive, making them suitable materials for higher frequencies and faster transmission speeds. However, these materials lack heat resistance and flame retardancy, making them difficult to use in portable devices and in-vehicle devices, which require heat resistance and flame retardancy.

[0011] In flat cables with a structure in which the insulating resin is exposed to the outside, the temperature reaches about 250°C during the reflow process of the soldering work, so if the insulating material is a general-purpose hydrocarbon resin, defects such as peeling of the insulating material from the shielding metal film when heated and flow of the resin from the end face of the flat cable will occur. For this reason, currently, highly heat-resistant resins such as fluororesin and liquid crystal polymers are used as insulating materials for applications that transmit high-speed high-frequency signals.

[0012] Furthermore, flat cables that use copper wires as conductors can only be formed in the same shape in the longitudinal direction, and flat cables with multiple conductors have difficulty forming a bent shape while maintaining their flatness. Also, the ends of the copper wires are exposed from the insulating resin.

[0013] To address this phenomenon, thin wiring boards with triplate lines and microstrip lines using low transmission loss resins such as liquid crystal polymers have been proposed (see Patent Document 3). This wiring board allows for the formation of circuits in the same way as flexible wiring boards, making it possible to form multiple signal lines on a single wiring board, and is therefore expected to contribute to future mobile devices.

[0014] Thin wiring boards with triplate lines or microstrip lines that use low transmission loss resins such as liquid crystal polymers do not provide complete shielding compared to coaxial cables, and there are limitations to the ground stability due to the upper and lower grounds being connected with vias. As higher frequencies and speeds are pursued, there are concerns about low transmission loss and EMI shielding.

[0015] Even low transmission loss resins such as liquid crystal polymers are affected by the outside air. For example, polyimide, a low dielectric resin, has excellent transmission characteristics, but has a high moisture absorption rate and its transmission characteristics are affected by humidity, making it unsuitable for use in current RF circuits. In other words, for thin wiring boards with triplate lines or microstrip lines, it is necessary to select a resin that is less affected by humidity, and there are significant limitations on the resins that can be used. If the use of high frequency bands progresses in the future, further stabilization of transmission characteristics will be required, so it will be necessary to minimize the effects of water vapor from the outside air.

[0016] Resins such as polyimide and air-containing resins absorb moisture due to the penetration of water vapor in the air, causing a large change in their electrical properties. For this reason, it is difficult to use them in current FFCs (Flat Flexible Cables), and PTFE, a fluororesin, or liquid crystal polymers are used exclusively. However, these resins are expensive, require processing at high temperatures, and have poor adhesive properties, making them difficult to produce and limiting the range of their use.

[0017] In addition to the inherent properties of flat cables, such as thinness and flexibility, flat cables for high-speed or high-frequency transmission are required to have transmission lines with stable transmission characteristics that are not affected by moisture absorption from the outside air, to have high electromagnetic shielding effect, to have heat resistance sufficient to withstand soldering and the like, to be flame retardant, and to be easily manufacturable and use inexpensive materials.

[0018] In response to the above demands, a shielded thin flat cable has been proposed that has stable transmission characteristics without being affected by moisture absorption from the outside air, has a high electromagnetic wave shielding effect, can be soldered even when using a general-purpose resin with low heat resistance as an insulator, and can be adapted to complex shapes, and a manufacturing method thereof (see Patent Document 8). Figure 1 is a diagram explaining Patent Document 8, and shows the structure of a shielded thin flat cable that is not affected by the outside air such as moisture absorption, and can use a thermoplastic resin with a low melting point as an insulator for a transmission line that has stable electrical characteristics.

[0019] Patent Document 8 proposes a shielded thin flat cable that has stable transmission characteristics that are not affected by moisture absorption from the outside air by covering the conductor and insulator with a metal film, has a high electromagnetic wave shielding effect, can be soldered even when a general-purpose resin with low heat resistance is used for the insulator, and can be adapted to complex shapes.

[0020] FFCs that use polyimide as an insulator, which is currently in widespread use, have poor alkali resistance, so their use near lithium-ion batteries, for example, is limited. Liquid crystal polymers are more resistant to alkali than polyimides, but the resistance is still insufficient. Also, lamination is difficult with PTFE, a representative fluororesin, and it is difficult to create a multi-layer structure as shown in Figure 1. There is a demand for flat cables that use insulation with excellent alkali resistance. [Prior art documents] [Patent documents]

[0021] [Patent Document 1] JP 2011-71403 A [Patent Document 2] JP 2017-188307 A [Patent Document 3] International Publication No. WO2014 / 156422 [Patent Document 4] JP 2010-182576 A [Patent Document 5] Japanese Patent Application Publication No. 5-242736 [Patent Document 6] International Publication No. WO2016 / 104066 [Patent Document 7] Japanese Patent Application Publication No. 61-131306 [Patent Document 8] International Publication No. WO2020 / 195784 [Non-patent literature]

[0022] [Non-Patent Document 1] Diatrend Co., Ltd., Glossary, Coaxial Cable Summary of the Invention [Problem to be solved by the invention]

[0023] Currently, flexible wiring boards are often used to wire the main board to the internal components of mobile devices, including smartphones, such as cameras and displays. On the other hand, coaxial cables are generally used for RF parts. In devices equipped with displays, such as smartphones, displays tend to become larger, so thinning in the thickness direction is important to make smartphones smaller and lighter. However, it is difficult to make coaxial cables thin, and recently, the thickness of coaxial cables has become an obstacle to the mounting design of devices. In other words, in order to mount them in devices with thickness restrictions, it is necessary to make the cables thinner.

[0024] In mobile devices such as smartphones, the functions of cameras and displays are becoming more sophisticated, the circuit scale of application processors is growing as applications evolve, and batteries are becoming larger as transmission speeds increase, making it difficult to fit all of these functions and components into the limited space inside the case. On the other hand, the number of types of wireless communication used by smartphones is also increasing, and the number of wires connecting antennas and devices, and wires connecting components and main boards is also increasing.

[0025] In order to solve the above-mentioned problems, Patent Document 8 proposes a shielded thin flat cable and a manufacturing method thereof, which has stable transmission characteristics that are not affected by moisture absorption from the outside air, have a high electromagnetic wave shielding effect, can be soldered even when an insulator made of general-purpose thermoplastic resin with low heat resistance is used, and can be adapted to complex shapes by covering the insulator surrounding the conductor with a metal film.

[0026] When using a general-purpose thermoplastic resin with low heat resistance as an insulator, in the manufacturing process of a shielded thin flat cable, the resin flows out from the end faces during the lamination process by thermocompression, resulting in large variations in the thickness of the flat cable. In addition, it is difficult to set processing conditions, etc., resulting in poor productivity.

[0027] To create a signal line with low transmission loss, it is important to match the characteristic impedance, so the characteristic impedance of the signal line, via land, and conductor electrode must be matched to the characteristic impedance of the conductor. In other words, the diameter of the signal line and via land must be as small as possible. However, general-purpose thermoplastic resins with low heat resistance are easily subject to dimensional changes and deformation due to thermal stress and mechanical stress. Therefore, compared to thermosetting resins with high heat resistance such as polyimide and epoxy resin, the accuracy of layer alignment during processing is inferior, and the diameter of the signal line and via land becomes larger.

[0028] As described in Reference 8, when forming grooves in an insulator, if the laser processing machine for forming the grooves has extremely low absorption of laser light, the laser will pass through a general-purpose thermoplastic resin with low heat resistance and be absorbed by the metal body, generating heat and causing the insulator to melt, resulting in the disadvantage that the desired shape cannot be obtained.

[0029] The grooves are preferably formed by laser processing, particularly using infrared light as the laser light. When using ultraviolet or visible light lasers, the processing speed is slow and the life of the laser light is short.

[0030] Carbon dioxide laser processing equipment is capable of high-speed processing and is widely used in industrial production. In order to perform efficient carbon dioxide laser processing, the processing wavelength is mainly around 10 μm, so the insulator needs to absorb that wavelength. If the absorption efficiency is poor, processing is possible by changing the processing conditions, but the processing time will be longer.

[0031] In the manufacture of shielded thin flat cables in which the insulator surrounding the conductor is covered with a metal film, there is a demand for a simple, highly productive method for manufacturing shielded thin flat cables that does not change in shape due to the lamination process or laser processing.

[0032] There is also a demand for a method of manufacturing a flat cable in which the characteristic impedance of the signal lines, via lands, conductor electrodes and conductors are matched.

[0033] The present disclosure provides a shielded, thin, flat cable in which a metal film is continuously provided on the surface of an insulator surrounding a conductor, and a method for manufacturing the same that solves the above-mentioned problems. [Means for solving the problem]

[0034] The shielded thin flat cable according to the present disclosure is a shielded thin flat cable having a conductor made of metal, an insulator sandwiching the conductor and encasing the conductor other than a conductor electrode that is conductive from the conductor and exposed on the surface, and a metal film that is continuous on the surface of the insulator other than around the conductor electrode, wherein the melting point of the conductor on a first film-like insulator surface on which an inner layer electrode conductive to the conductor and the conductor electrode is formed, the inner layer electrode, and a second film-like insulator that is bonded to the first film-like insulator is 10° C. or more lower than the melting point of the first film-like insulator. a third film-shaped insulator having a melting point equal to or higher than that of the first film-shaped insulator, on a surface of the second film-shaped insulator opposite to the surface that sandwiches the conductor,A shielded thin flat cable according to another embodiment of the present disclosure is a shielded thin flat cable having a conductor made of metal, an insulator that sandwiches the conductor and wraps the conductor other than the conductor electrodes that are conductively connected to the conductor and exposed on the surface, and a metal film that is continuous with the surface of the insulator other than the periphery of the conductor electrodes, the insulator containing 30% by weight or more of a polymer containing 80 mol % or more of an alkene and a laser light absorber, and having a minimum transmittance of 85% or less for light with a wavelength of 0.8 μm or more and 11.0 μm or less when the insulator has a thickness of 50 μm.

[0035] In addition, in a shielded thin flat cable according to another embodiment of the present disclosure, The alkene is preferably one or more of ethylene, propylene, butene, pentene, hexene, heptene, octene, cyclopropene, cyclobutene, cyclopentene, cyclohexene, and cyclopentene.

[0036] In the shielded thin flat cable according to the present disclosure, the first and second film-like insulators preferably contain 30% by weight or more of a polymer containing 80% by mole or more of an alkene.In the shielded thin flat cable according to another embodiment of the present disclosure, the polymer preferably contains less than 20% by mole of one or more of vinyl acetate, acrylic acid, methyl acrylate, ethyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, and maleic anhydride.

[0037] In the shielded thin flat cable according to the present disclosure, it is preferable that the second film-like insulator contains a copolymer of a monomer having a carboxyl group and an alkene.In the shielded thin flat cable according to another embodiment of the present disclosure, it is preferable that the melting points of the insulators sandwiching the conductor differ from each other by 10°C or more.

[0038] In addition, in the shielded thin flat cable according to another embodiment of the present disclosure, it is preferable that the laser light absorber is one or more of silicon dioxide, hollow silica, black silica, silicic acid and metal salts thereof, quartz, glass, glass balloons, magnesium oxide, nickel oxide, cobalt oxide, molybdenum oxide, copper oxide, iron oxide, tin oxide, manganese dioxide, aluminum oxide, titanium oxide, calcium oxide, aluminum nitride, sodium phosphate, potassium dihydrogen phosphate, barium sulfate, aluminum sulfate, aluminum hydroxide, carbon black, carbon nanotubes, and titanium black.

[0039] In the shielded thin flat cable according to the present disclosure, it is preferable that the first film-like insulator contains a copolymer of a monomer having a carboxyl group and an alkene. In the shielded thin flat cable according to another embodiment of the present disclosure, it is preferable that the metal film is formed on a wall surface of a groove formed by a laser beam on the surface of the insulator.

[0040] In addition, in the shielded thin flat cable according to the present disclosure, it is preferable that a plurality of shielded thin flat cables each having a metal film continuous with the outer surface of the insulator encasing the conductor are integrally formed.

[0041] In the shielded thin flat cable according to the present disclosure, it is preferable that the metal film between the integrated plurality of shielded thin flat cables is continuous.

[0042] In addition, in the shielded thin flat cable according to the present disclosure, when the first film-shaped insulator is homopolypropylene or block polypropylene, it is preferable that the second film-shaped insulator is random copolymer polypropylene of propylene and ethylene. In addition, in the shielded thin flat cable according to the present disclosure, when the first film-shaped insulator is high-density polyethylene, it is preferable that the second film-shaped insulator is linear low-density polyethylene. In addition, in the shielded thin flat cable according to another embodiment of the present disclosure, it is preferable that the metal film continuously covers the entire surface of the insulator except for the periphery of the conductor electrode.

[0043] The method for manufacturing a shielded thin flat cable according to the present disclosure includes laminating metal films on both sides of a first film-like insulator, performing a circuit formation process on the metal film on one side of the first film-like insulator to form a conductor and an inner layer electrode that is conductive to an electrode continuous with the conductor, and performing a circuit formation process on the metal film on the other side to form an opening for drilling a via hole, and forming, on the conductor and the inner layer electrode formed on one side of the first film-like insulator, a second film-like insulator having a melting point that is 10° C. or more lower than the melting point of the first film-like insulator, A metal film is laminated on the second film-like insulator, and the metal film on the other side of the first film-like insulator, the first film-like insulator, and the second film-like insulator are removed, or the metal film on the other side of the first film-like insulator, the first film-like insulator, the second film-like insulator, and the metal film on the second film-like insulator are broken, thereby forming an end face of the shielded thin flat cable to have an outer peripheral shape of the shielded thin flat cable, and forming a metal film on the end face. A manufacturing method for a shielded thin flat cable according to another embodiment of the present disclosure is characterized in that a conductor made of metal is sandwiched, an insulator is provided that wraps the conductor other than a conductor electrode that is conductive from the conductor and exposed on the surface, a metal film is provided continuously on the surface of the insulator other than the periphery of the conductor electrode, the insulator contains 30% by weight or more of a polymer containing 80 mol% or more of an alkene, and a laser light absorber, and when the insulator is made 50 μm thick, the minimum transmittance of light with a wavelength of 0.8 μm or more and 11.0 μm or less is 85% or less.

[0044] In addition, in the method for producing a shielded thin flat cable according to the present disclosure, ShapeIt is preferable that a third film-like insulator having a melting point equal to or higher than that of the first film-like insulator is provided on the surface opposite to the conductor side of the insulator.In addition, in the method for producing a shielded thin flat cable according to another embodiment of the present disclosure, it is preferable that the alkene is one or more of ethylene, propylene, butene, pentene, hexene, heptene octene, cyclopropene, cyclobutene, cyclopentene, cyclohexene, and cyclopentene.

[0045] In the method for producing a shielded thin flat cable according to the present disclosure, it is preferable that the first film-like insulation and the second film-like insulation contain 30% by weight or more of a polymer containing 80% by mole or more of an alkene. In the method for producing a shielded thin flat cable according to another embodiment of the present disclosure, it is preferable that the polymer contains less than 20% by mole of one or more of vinyl acetate, acrylic acid, methyl acrylate, ethyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, and maleic anhydride.

[0046] In the method for producing a shielded thin flat cable according to the present disclosure, it is preferable that the second film-like insulator contains a copolymer of an alkene and a monomer having a carboxyl group. In the method for producing a shielded thin flat cable according to another embodiment of the present disclosure, it is preferable that the melting points of the insulators sandwiching the conductor differ by 10° C. or more.

[0047] In the method for producing a shielded thin flat cable according to the present disclosure, it is preferable that the first film-like insulator contains a copolymer of an alkene and a monomer having a carboxyl group.In the method for producing a shielded thin flat cable according to another embodiment of the present disclosure, it is preferable that the laser light absorber is one or more of silicon dioxide, hollow silica, black silica, silicic acid and its metal salts, quartz, glass, glass balloon, magnesium oxide, nickel oxide, cobalt oxide, molybdenum oxide, copper oxide, iron oxide, tin oxide, manganese dioxide, aluminum oxide, titanium oxide, calcium oxide, aluminum nitride, sodium phosphate, potassium dihydrogen phosphate, barium sulfate, aluminum sulfate, aluminum hydroxide, carbon black, carbon nanotubes, and titanium black.

[0048] In addition, in the method for producing a shielded thin flat cable according to the present disclosure, when the first film-like insulator is homopolypropylene or block polypropylene, it is preferable that the second film-like insulator is random copolymer polypropylene of propylene and ethylene. In addition, in the method for producing a shielded thin flat cable according to another embodiment of the present disclosure, it is preferable that the surface of the insulator is irradiated with laser light, the insulator is removed by the laser light, and the metal film is formed on the wall surface of the groove formed by removing the insulator.

[0049] In the method for producing a shielded thin flat cable according to the present disclosure, it is preferable that when the first film-like insulator is high-density polyethylene, the second film-like insulator is linear low-density polyethylene.In the method for producing a shielded thin flat cable according to another embodiment of the present disclosure, it is preferable to vertically integrate a plurality of the thin flat cables sandwiching a plurality of the conductors, remove the metal film on one of the upper and lower surfaces of the integrated shielded thin flat cable, irradiate the insulator from which the metal film has been removed with the laser light, remove the insulator up to the metal film of the other shielded thin flat cable, and form the metal film on the wall surface of the groove formed by removing the insulator.

[0050] In addition, in the method for producing a shielded thin flat cable according to the present disclosure, it is preferable to perform a circuit formation process on the metal film on one side of the first film-like insulator to form an inner layer electrode that is conductive to the conductor and the electrode continuous with the conductor, and perform a circuit formation process on the metal film on the other side to form an opening for drilling a via hole, and then bond a second film-like insulator, a metal film, another second film-like insulator, and the conductor of another intermediate product of the shielded thin flat cable to the other second film-like insulator, and irradiate the insulators on the top and bottom of the shielded thin flat cable in which multiple shielded thin flat cable intermediate products are integrated vertically with laser light, remove the insulator up to the metal film of the other shielded thin flat cable, and form the metal film on the wall surface of the groove formed by removing the insulator. In addition, in the method for producing a shielded thin flat cable according to another embodiment of the present disclosure, it is preferable to form the metal film continuously on the entire surface of the insulator except for the periphery of the conductor.

[0051] In the method for producing a shielded thin flat cable according to the present disclosure, a circuit forming step is performed on the metal film on one side of the first film-like insulator to form an inner layer electrode that is conductive with a conductor and an electrode continuous with the conductor, and a circuit forming step is performed on the metal film on the other side to form an opening for drilling a via hole, and a second film-like insulator, a metal film, another second film-like insulator, and the conductor of another intermediate product of the shielded thin flat cable are bonded to the conductor side of the first film-like insulator of the shielded thin flat cable intermediate product as the other second film-like insulator side, and the upper and lower metal films and the insulators are broken along the outer shape of a shielded thin flat cable in which a plurality of the shielded thin flat cable intermediate products are integrated vertically, and the metal film is formed on an end face of the shielded thin flat cable formed. In the method for producing a shielded thin flat cable according to another embodiment of the present disclosure, the groove is preferably formed by the laser light, and the metal film is preferably formed on the wall surface of the formed groove by plating.

[0052] In the method for manufacturing a shielded thin flat cable according to the present disclosure, it is preferable that the metal film between the integrated shielded thin flat cables is formed continuously. In another embodiment of the method for manufacturing a shielded thin flat cable according to the present disclosure, the method for manufacturing a shielded thin flat cable includes providing an insulator that encases the multiple conductors except for the multiple conductor electrodes that are conductive from the multiple conductors and exposed on the surface, forming multiple rows of the metal film parallel to the conductors on the surface of the insulator except around the conductor electrodes, and then cutting the insulator into individual pieces parallel to the conductors. Effect of the Invention

[0053] The present disclosure provides a thin, shielded flat cable with excellent shielding properties, high precision, and high energy efficiency, as well as a thin, shielded flat cable with excellent transmission characteristics and a method for manufacturing the same. [Brief description of the drawings]

[0054] [Figure 1] 1 shows a shielded thin flat cable according to a first embodiment of the present disclosure, where (A) is a perspective view. (B) is an enlarged perspective view of a terminal portion of the shielded thin flat cable. (C) is a perspective cross-sectional view of a portion of the shielded thin flat cable where a conductor is present. (B-1), (B-2), and (B-3) are plan views of the terminal portion of the terminal exposed portion of the shielded thin flat cable, where (B-1) is a plan view of B, and (B-2) and (B-3) show other terminal portions. [Diagram 2] 3 illustrates a manufacturing process for a thin shielded flat cable according to a first embodiment of the present disclosure. [Diagram 3] 1 shows a conventional manufacturing process for a thin shielded flat cable. [Figure 4] 6 illustrates a manufacturing process for a thin shielded flat cable according to a second embodiment of the present disclosure. [Diagram 5] 1 shows an inner layer wiring structure of a shielded thin flat cable according to an embodiment of the present disclosure. [Figure 6] 2 shows a conventional manufacturing process for a thin shielded flat cable, illustrating the step of cutting the insulation. [Figure 7] 1 shows the structure of a thin flat cable according to a conventional embodiment. [Figure 8] 11 shows a part of a manufacturing process for a thin shielded flat cable according to a third embodiment of the present disclosure. [Figure 9] 13 shows a structure of a shielded, thin flat cable in which a plurality of thin flat cables according to a fourth embodiment of the present disclosure are integrated in a horizontal direction. [Figure 10]13 shows the structure of a shielded, thin flat cable in which a plurality of thin flat cables according to a fifth embodiment of the present disclosure are integrated in the horizontal and vertical directions. [Figure 11] 13 shows a manufacturing process for a shielded, thin flat cable in which a plurality of thin flat cables according to a fourth embodiment of the present disclosure are integrated in a horizontal direction. [Figure 12] 13 shows a manufacturing process for a shielded thin flat cable in which a plurality of thin flat cables according to a fifth embodiment of the present disclosure are integrated in the horizontal and vertical directions. [Figure 13] 13 shows a shielded thin flat cable having conductor electrodes provided on the end faces of the thin flat cable according to a sixth embodiment of the present disclosure. [Figure 14] 13 shows a manufacturing process for a shielded thin flat cable having conductor electrodes on its end faces according to a sixth embodiment of the present disclosure. [Figure 15] 13 shows a shielded thin flat cable having conductor electrodes provided on end faces in a case where the thin flat cable has two conductors according to a sixth embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0055] (Embodiment 1) 1 shows a shielded thin flat cable 101 according to a first embodiment of the present disclosure, with (A) showing a perspective view. (B) shows an enlarged perspective view of a terminal portion 103 of the shielded thin flat cable 101. (C) shows a perspective cross-sectional view of a conductor portion 102 in which a conductor 204 of the shielded thin flat cable 101 exists. (B-1), (B-2), and (B-3) show plan views of the terminal portion 103 of the shielded thin flat cable, with (B-1) being a plan view of B, and (B-2) and (B-3) showing other terminal portions 103.

[0056] In addition to the inherent flat cable characteristics of being thin and flexible and having low transmission loss, flat cables are required to have the following: a transmission line that is free from the effects of external air such as moisture absorption and has stable physical and electrical characteristics, a high electromagnetic shielding effect, heat resistance that can withstand soldering and the like, flame retardancy, excellent chemical resistance, good processability, high productivity, and the use of inexpensive materials. Transmission characteristics are particularly important for flat cables used for high-frequency and high-speed transmission.

[0057] The shielded thin flat cable 101 of the present disclosure has a conductor 204 made of metal, an insulator 106 that sandwiches the conductor 204 and encases the conductor 204 other than the conductor electrode 105 that is conductive from the conductor 204 and exposed on the surface, and a metal film 202 that extends continuously over the surface of the insulator 106 other than around the conductor electrode 105.

[0058] 1(A), a shielded thin flat cable 101 is composed of a terminal portion 103 having a conductor electrode 105 with which a conductor 204 is electrically connected, and a conductor portion 102 in which the conductor 204 is present. The terminal portion 103 is composed of the conductor electrode 105 with which the conductor 204 is electrically connected, an exposed insulator 106 around the conductor electrode 105 where no metal film 202 is provided, and a metal film 202 provided continuously on the surface of the insulator 106 other than the exposed insulator 106 where no metal film 202 is provided. The conductor portion 102 is composed of the conductor 204, the insulator 106 that encases the conductor 204, and the metal film 202 provided continuously on the surface of the insulator 106.

[0059] As shown in Fig. 1(B), the short end faces of the shielded thin flat cable 101 also have metal films 202. As shown in Fig. 1(C), the shielded thin flat cable 101 has an insulator 106 encasing the conductors 204 other than the conductor electrodes 105 that are exposed on the surface of the shielded thin flat cable 101 and in which the conductors 204 are conductive, and has a metal film 202 that is continuous with the surface of the insulator 106 other than around the conductor electrodes 105.

[0060] The metal film 202 is provided continuously in the short and long directions of the shielded thin flat cable 101. It is also provided continuously on the end faces in the long direction. The continuous metal film 202 can suppress the effects of deformation of the insulator 106 due to heat, defects due to peeling, and the intrusion of water vapor from the outside air on the electrical properties of the conductor 204. The metal film 202 may not be provided on a part of the surface of the insulator 106, so long as it does not cause damage to the shielding properties of the conductor 204, damage to the electrical properties, deformation of the insulator 106, or peeling of the insulator 106 and the metal film 202.

[0061] In order to improve the shielding performance of the conductor 204 of the shielded thin flat cable 101, the metal film 202 is preferably provided on the entire surface of the insulator 106 except for the periphery of the conductor electrode 105. The metal film 202 is not provided around the conductor electrode 105. The periphery needs to have an area that satisfies the distance that prevents the conductor electrode 105 and the metal film 202 from being electrically connected. It is preferable that the area on the surface of the insulator 106 where the metal film 202 is not provided is small. In addition, since the adhesive strength between the metal film 202 and the insulator 106 is reduced by heat and they are easily peeled off, it is preferable that the end faces in the longitudinal direction and the lateral direction of the shielded thin flat cable 101 are covered with the metal film 202 without exposing the insulator 106. The end faces in the longitudinal direction and the lateral direction are covered with the metal film 202, and it is preferable that the metal film 202 is provided on 95% or more of the surface of the insulator 106.

[0062] The exposed portion of the insulator 106 where the metal film 202 is not provided around the conductor electrode 105 is exposed to the outside air. It is important to minimize the area of ​​the exposed portion of the insulator 106 around the conductor electrode 105. If the exposed area is large, the insulator 106 may absorb moisture due to water vapor in the outside air, and may be affected by the moisture absorption, resulting in a deterioration of the transmission characteristics.

[0063] Conductor 204 other than conductor electrode 105 is wrapped in insulator 106, and metal film 202 is provided continuously on the surface of insulator 106 other than around conductor electrode 105. In other words, by providing metal film 202 on both the longitudinal end faces and the lateral end faces of shielded thin flat cable 101, the protective function of metal film 202 reduces the influence of outside air on shielded thin flat cable 101, enabling it to maintain its transmission characteristics for a long period of time.

[0064] A conventional flat cable is shown in Fig. 7. The flat cable does not have metal film 202 on its longitudinal end faces or lateral end faces. In such a flat cable, the insulator 106 absorbs moisture due to water vapor in the outside air, and the transmission characteristics may deteriorate due to the influence of moisture absorption. In addition, the adhesion strength between the metal film 202 and the insulator 106 may decrease due to moisture absorption due to heat such as solder reflow, causing peeling or melting and deformation of the insulator 106.

[0065] The distance between the end of the conductor electrode 105 and the end of the metal film 202 is 10 μm or more and 1000 μm or less. The insulator 106 is exposed between them. If the distance is less than 10 μm, the end of the conductor electrode 105 and the end of the metal film 202 may be electrically connected. If the distance is more than 1000 μm, water vapor from the outside air may penetrate more into the insulator 106, which may deteriorate the transmission characteristics and heat resistance. In addition, the shielding properties of the conductor 204 may be damaged. Furthermore, the insulator 106 may melt and change shape during a thermal process such as reflow. The distance between the end of the conductor electrode 105 and the end of the metal film 202 may be equal or different around the conductor electrode 105.

[0066] 1(B-1), (B-2), and (B-3) show plan views of the terminal portion 103. (B-1) shows the case where the conductor electrode 105 in FIG. 1(B) is circular. (B-2) shows the case where the conductor electrode 105 is rectangular and there are multiple conductor electrodes 105. (B-3) shows the case where the conductor electrodes 105 are multiple rectangular and are provided at the longitudinal end of the shielded thin flat cable 101. The metal film 202 is not provided around the conductor electrode 105 in accordance with the shape of the conductor electrode 105. The conductor electrode 105 may have any shape. Also, multiple conductor electrodes 105 may be provided on one conductor 204. The metal film 202 is used as a ground.

[0067] As shown in FIG. 2(G), in the terminal portion 103, the conductor 204 is connected to the conductor electrode 105 through the inner layer electrode 214 and the via hole 208. The conductor electrode 105 is for connection to an external element, and is used as a connector connection terminal, an SMT soldering electrode, a soldering terminal for fixing a connector, a terminal for ACF (Anisotropic Conducting Film) connection, etc. In order to achieve the above purpose, the surface of the conductor electrode 105 may be subjected to surface treatment such as solder coating, gold plating, tin plating, silver plating, OSP (Organic Solderability Preservatives), etc. as necessary. The periphery of the conductor electrode 105 is structured such that there is no electrical continuity between the metal film 202 and the conductor electrode 105 by the insulator 106 on which the metal film 202 is not formed.

[0068] In the shielded thin flat cable 101 according to the present disclosure, the insulator 106 protects the conductor 204, and the metal film 202 protects the insulator 106. The metal film 202 shields the conductor 204.

[0069] Metal film 202, which is provided continuously on the surface of insulator 106 except around conductor electrode 105, prevents water vapor or chemical liquid from penetrating from the outside into insulator 106. In addition, metal film 202 prevents flames directed from the outside at shielded thin flat cable 101 from directly touching insulator 106, improving the flame retardancy of insulator 106.

[0070] The insulator 106 contains 30% by weight or more of a polymer containing 80% by mole or more of an alkene, and a laser light absorber, and when the insulator 106 has a thickness of 50 μm, the minimum transmittance of light having a wavelength of 0.8 μm or more and 11.0 μm or less is 85% or less. Laser processing is possible even if the transmittance exceeds 85%, but for efficient processing, the transmittance is preferably 60% or less, and more preferably 30% or less.

[0071] The alkene is suitably one or more of ethylene, propylene, butene, pentene, hexene, heptene octene, cyclopropene, cyclobutene, cyclopentene, cyclohexene, cyclopentene.

[0072] Polymers containing 80 mol % or more of alkenes include high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, cycloolefin polymer (COP), cycloolefin copolymer (COC), methylpentene polymer, and the like.

[0073] The alkene such as ethylene or propylene may be a monomer obtained from biomass or a monomer obtained by recycling. The use of a monomer obtained from biomass or a monomer obtained by recycling can contribute to the suppression of carbon dioxide emissions.

[0074] The polymer suitably contains, as monomers other than alkenes, less than 20 mol % of one or more of vinyl acetate, acrylic acid, methyl acrylate, ethyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, and maleic anhydride.

[0075] The insulator 106 may include a resin such as polybutadiene, polyphenylene ether, fluororesin, liquid crystal polymer, polystyrene, SBS, or the like.

[0076] The laser light absorber contained in the insulator 106 is preferably silicon dioxide, hollow silica, black silica, silicic acid and its metal salts, quartz, glass, glass balloons, magnesium oxide, nickel oxide, cobalt oxide, molybdenum oxide, copper oxide, iron oxide, tin oxide, manganese dioxide, aluminum oxide, titanium oxide, calcium oxide, aluminum nitride, sodium phosphate, potassium dihydrogen phosphate, barium sulfate, aluminum sulfate, aluminum hydroxide, carbon black, carbon nanotubes, or titanium black.

[0077] Further, silicon dioxide, hollow silica, black silica, silicic acid and its metal salts, quartz, glass, glass balloons, magnesium oxide, nickel oxide, cobalt oxide, molybdenum oxide, copper oxide, iron oxide trioxide, tin oxide, manganese dioxide, aluminum oxide, titanium oxide, calcium oxide, aluminum nitride, carbon black, carbon nanotubes, and titanium black are more preferable as laser light absorbers that do not deteriorate the dielectric properties of the insulator 106. In addition to the polymer containing 80 mol % or more of an alkene, the laser light absorber, and the resin, the insulator 106 can appropriately contain additives such as fillers, viscosity adjusters, lubricants, and flame retardants within a range that does not deteriorate the dielectric properties.

[0078] The thickness of the insulator 106 is preferably 10 μm to 1000 μm. More preferably, it is 30 μm to 500 μm. If it is thinner than 10 μm, poor interlayer insulation between the conductor 204 and the metal film 202 occurs, and it becomes difficult to control the line width for impedance matching. If it is thicker than 1000 μm, the speed of the laser processing for forming grooves in the insulator 106 with a laser, which will be described later, becomes extremely slow.

[0079] By making the insulator 106 contain 30% by weight or more of a polymer containing 80% by mole or more of an alkene, it is possible to manufacture a thin shielded flat cable 101 at low cost. However, since a polymer containing 80% by mole or more of an alkene does not easily absorb laser light having a wavelength of 0.8 μm or more and 11.0 μm or less, it is difficult to form a groove by irradiating the surface of the insulator 106 with laser light. However, by making the insulator 106 contain a laser light absorber, it is possible to form a groove by irradiating with laser light. When the insulator 106 has a thickness of 50 μm, the insulator 106 is made to contain a laser light absorber so that the minimum transmittance of light having a wavelength of 0.8 μm or more and 11.0 μm or less is 85% or less. If the transmittance is 85% or more, it becomes difficult to form a groove by irradiating with laser light, or it takes a long time.

[0080] The conductor 204 is preferably made of a material having good electrical conductivity, such as gold, silver, copper, or aluminum. In consideration of flexibility and electrical conductivity, copper is most suitable. If the conductor 204 is not made of gold or silver, it may be plated with gold or silver.

[0081] The width of the conductor 204 is preferably 0.01 mm to 10 mm, and more preferably 0.02 mm to 5 mm. If the conductor width is less than 0.01 mm, it is difficult to control the finished dimensional accuracy of the width of the conductor 204. Therefore, impedance matching is difficult and it is not preferable as a conductor. Furthermore, if the width of the conductor 204 is less than 0.01 mm, the conductor loss increases and it is not preferable as a transmission line. Conversely, if the width of the conductor 204 exceeds 10 mm, the thickness of the insulator 106 to obtain the desired characteristic impedance becomes too thick, and it is not suitable for a shielded thin flat cable 101 that pursues thinness.

[0082] The width of the conductor 204 has a large effect on the transmission characteristics, so the width must be precisely controlled. In addition, in order to improve the line width precision of the conductor 204, the MSAP method (Modified Semi Additive Process) can be used. In order to further improve the transmission characteristics, if the conductor 204 is not made of gold or silver, it may be plated with gold or silver. Since the shielded thin flat cable 101 according to the present disclosure has a strip line structure, the characteristic impedance of the conductor 204 is determined by the conductor width, conductor thickness, insulator thickness, dielectric constant of the insulator, and the like. In order to obtain a desired impedance, the width of the conductor 204 is usually adjusted.

[0083] The thickness of the conductor 204 is preferably 1 μm to 75 μm. Due to conductor loss and the skin effect, electrical signals are not transmitted efficiently if the thickness is less than 1 μm. Furthermore, if the thickness is less than 1 μm, there is a high possibility that the conductor 204 will break when bent. If the thickness exceeds 75 μm, it becomes difficult to achieve precision in the width when manufacturing the conductor 204, and furthermore, the insulator 106 for wrapping the conductor 204 becomes thick, which is not suitable for the shielded thin flat cable 101 that pursues thinness.

[0084] The metal film 202 of the shielded thin flat cable 101 uses a metal with good electrical conductivity, and gold, silver, copper, and aluminum are preferable, with copper being preferred. In consideration of flexibility and electrical conductivity, copper is most preferable. The metal film 202 on the flat upper and lower surfaces of the shielded thin flat cable 101 can be copper foil, but the longitudinal end faces and lateral end faces of the shielded thin flat cable 101 are preferably copper formed by plating. The electrical resistivity of the metal film 202 is preferably 1 μΩ·m or less. In order to add functions such as oxidation prevention and noise countermeasures, the metal film 202 may be a combination of different metals, and for example, nickel, zinc, chromium, iron-based alloys, etc. can be formed on the outside of the copper film.

[0085] The thickness of the metal film 202 is preferably 3 μm to 100 μm. If the thickness is less than 3 μm, pinholes and scratches occur, making it impossible to maintain the internal barrier properties, and the metal film 202 melts during laser processing, making it impossible to form the linear grooves 206. Furthermore, the metal film 202 cracks due to the expansion of the insulator 106 during heating. Furthermore, if the thickness exceeds 100 μm, the processing for forming the linear grooves 206 and the holes 207 as via holes becomes complicated and takes a long time. When the metal film 202 is formed by plating, the plating time is long, which causes problems in the manufacturing process, such as warping of the work plate.

[0086] The distance in the planar direction between the conductor 204 and the metal film 202 is 20 μm or more. If it is less than 20 μm, there is a possibility that the conductor 204 and the metal film 202 may short-circuit. In addition, the distance in the vertical direction between the conductor 204 and the metal film 202 is 10 μm or more and 700 μm or less. If it is less than 10 μm, there is a possibility that a short-circuit may occur, and if it exceeds 700 μm, it takes a long time to form the linear groove 206 in the insulator 106 by a laser.

[0087] 2(G), in the terminal portion 103, the conductor 204 is connected to the conductor electrode 105 through the inner layer electrode 214 and the via hole 208. An electric signal enters from one conductor electrode 105, exits from the via hole 208, the inner layer electrode 214, the conductor 204, the opposite inner layer electrode 214, the opposite via hole 208, and the opposite conductor electrode 105, and is transmitted to another.

[0088] As shown in FIG. 5(A), the inner layer electrode 214 is formed continuously from the conductor 204. Therefore, the thickness and material are the same as those of the conductor 204. In order to connect the conductor electrode 105 to the via hole 208, the inner layer electrode 214 is made equal to or larger than the diameter of the cylindrical via hole 208 as shown in FIG. 5(B). The shape of the inner layer electrode 214 is preferably a circle, but any shape may be used as long as it is equal to or larger than the cross section of the via hole 208. Also, an auxiliary shape such as a teardrop may be added. In the case of a circle, the diameter is usually 50 μm or more and 2 mm or less. It is more preferable that the diameter is 100 μm or more and 800 μm or less. If it is less than 50 μm, it is difficult to align the inner layer electrode 214 and the via hole 208, and if it exceeds 2 mm, it is difficult to match the characteristic impedance. The characteristic impedance of the signal line must be matched, but matching the characteristic impedance of the inner layer electrode 214 and the conductor 204 is difficult, so the diameter of the inner layer electrode 214 must be made as small as possible to achieve characteristic impedance matching.

[0089] The via hole 208 is formed by removing the insulator 106 from the portion where the conductor electrode 105 is to be formed to the inner layer electrode 214 by irradiating it with a laser beam, and plating the hole 207 as a via hole formed by removing the insulator 106. Therefore, the cross section has a shape that is approximately a circle. The plating is preferably performed with copper.

[0090] A manufacturing method of the shielded thin flat cable 101 according to the present disclosure is shown in Fig. 2. The shielded thin flat cable 101 sandwiches a conductor 204 made of metal, provides an insulator 106 that encases the conductor 204 except for the conductor electrode 105 that is conductive from the conductor 204 and exposed on the surface, and provides a metal film 202 continuously on the surface of the insulator 106 except around the conductor electrode 105.

[0091] FIG. 2 illustrates a manufacturing process for the thin shielded flat cable according to the first embodiment of the present disclosure.

[0092] FIG. 2(A) shows a laminated sheet of the metal film 202 and the insulator 106, in which the metal film 202A and the metal film 202B are laminated on both sides of the film-like insulator 106A. The film-like insulator 106A and the metal film 202A and the metal film 202B are laminated by heat and pressure bonding, but before the lamination, pretreatment may be performed to improve the adhesion strength. For example, the film-like insulator 106A is subjected to plasma treatment, corona treatment, or UV treatment, and the lamination side of the metal film 202A and the metal film 202B is subjected to primer treatment or plasma treatment. Lamination is also possible by a dry lamination method using an adhesive. It is also possible to laminate the film-like insulator 106A and the metal film 202 of the metal film 202A and the metal film 202B by inserting a bonding sheet between them and pressing them together. Furthermore, it is also possible to laminate one metal film 202 by pressing the other metal film 202 while extruding molten film-like insulator 106A onto the other metal film 202.

[0093] Metal foil is used for the metal film 202A and the metal film 202B, and it is preferable that the metal film 202 used for bonding is made of metal foil, particularly copper foil.

[0094] When the metal film 202A and the metal film 202B are bonded to both sides of the film-like insulator 106A by thermocompression bonding, it is preferable to provide a layer of a copolymer of a monomer having a carboxyl group and an alkene on the side of the film-like insulator 106A that contacts the metal film 202A and the metal film 202B in order to increase the adhesive strength. The adhesive strength between the copolymer of a monomer having a carboxyl group and an alkene and a metal is increased by thermocompression bonding. In particular, when polyethylene using ethylene as the alkene or polypropylene using propylene as the alkene is used as the polymer, it is preferable to use a resin obtained by graft-polymerizing maleic anhydride with polyethylene or polypropylene. It is preferable that the polymer contains less than 20 mol % of a monomer having a carboxyl group, and more preferably less than 10 mol %. If it is less than 10 mol %, the effect on the transmission characteristics can be kept small.

[0095] 2(B) shows a circuit formation process in which the metal film 202B is the conductor 204 and the inner layer electrode 214, and the metal film 202A is the metal film 202 formed on the outer surface of the conductor electrode 105 and the insulator 106. Here, by removing a part of the metal film 202A, an opening 209 for drilling a via hole and an opening 212 for forming a groove are formed.

[0096] The circuit formation process can use a method commonly used in the manufacture of printed wiring boards. For example, by using a procedure such as forming an etching mask, exposing, developing, etching, and peeling off the etching mask, the conductor 204 and the inner layer electrode 214 are formed by leaving only the necessary metal film 202B, and the metal film 202 is formed on the surface of the conductor electrode 105 and the insulator 106 by leaving only the metal film 202A. By removing a part of the metal film 202A, an opening 209 for drilling a via hole and an opening 212 for forming a groove are formed.

[0097] FIG. 2(C) shows a process of laminating a film-shaped insulator 106B and a metal film 202C in order onto the film-shaped insulator 106A, the formed conductor 204, and the inner layer electrode 214. The material of the film-shaped insulator 106B may be the same as that of the film-shaped insulator 106A. Alternatively, insulators of different materials may be used. The film-shaped insulator 106A and the film-shaped insulator 106B are laminated by thermocompression bonding. The conductor 204 and the inner layer electrode 214 are sandwiched between the film-shaped insulator 106A and the film-shaped insulator 106B. Thermocompression bonding is preferably performed in a vacuum state.

[0098] When laminating the conductor 204 and the inner layer electrode 214 formed on the surface of the film-like insulator 106A to the film-like insulator 106B, and laminating the film-like insulator 106B to the metal film 202C by thermocompression bonding, it is preferable to provide a copolymer of a monomer having a carboxyl group and an alkene as a layer on both sides of the film-like insulator 106B in order to increase the adhesive strength. The adhesive strength between the copolymer of a monomer having a carboxyl group and an alkene and a metal is increased by thermocompression bonding. In particular, when using polyethylene using ethylene as the alkene or polypropylene using propylene as the alkene as the polymer, it is preferable to use a polymer obtained by graft polymerization of maleic anhydride to polyethylene or polypropylene.

[0099] It is preferable that the metal film 202C uses the same metal as the metal film 202A. The method of forming the metal film 202C may be to laminate the film-shaped insulator 106B to the film-shaped insulator 106A, and then laminate the metal film 202C, or to laminate the film-shaped insulator 106B and the metal film 202C to the film-shaped insulator 106A at the same time. It may be possible to laminate the film-shaped insulator 106B and the metal film 202C to the film-shaped insulator 106A, and then laminate the film-shaped insulator 106B to the film-shaped insulator 106A. FIG. 2(D) shows a laminate formed by laminating the film-shaped insulator 106A, the film-shaped insulator 106B, and the metal film 202C.

[0100] 2(E) shows a process of forming linear grooves 206 and holes 207 as via holes parallel to the conductor 204 along both side surfaces of the conductor 204 and the inner layer electrode 214. To form the linear grooves 206, the insulator 106 exposed in the groove formation openings 212 is removed. The linear grooves 206 are formed by removing the insulator 106 linearly without penetrating the metal film 202A on one surface that contacts the insulator 106, while leaving the metal film 202C on the other surface.

[0101] When forming the hole 207 as a via hole, the insulator 106 exposed at the opening 209 for drilling the via hole is removed down to the inner layer electrode 214 without penetrating the metal film 202A.

[0102] The linear groove 206 and the hole 207 as a via hole are formed by, for example, a device equipped with a laser processing machine, a plasma processing machine, a sandblaster, etc. A laser processing machine is preferable because of its fast processing speed. By forming the linear groove 206, the insulator 106 is exposed on the wall surface 205.

[0103] The wavelengths of laser light used in laser processing machines are 0.248 μm for excimer lasers, 0.355 μm for UV lasers, 0.532 μm for green lasers, 1.064 μm for near-infrared lasers around 1 μm, such as YAG lasers and fiber lasers, and 9.4 μm and 10.6 μm for far-infrared lasers around 10 μm, such as carbon dioxide lasers. Excimer lasers, UV lasers, and green lasers ranging from 0.25 μm to 0.60 μm are collectively referred to as UV and visible light lasers. In this disclosure, in order to form linear grooves 206 in the insulator 106, deep engraving of the insulator 106 is necessary. The speed of deep engraving is extremely slow with UV and visible light lasers. Near-infrared and far-infrared lasers have a high processing speed, and their use is preferred.

[0104] When selecting a laser processing machine, consideration must be given to matching it with the absorption wavelength of the insulator 106. In particular, YAG laser, fiber laser, and carbon dioxide gas laser processing machines are widely used due to their fast resin processing speed, and are preferred laser processing machines in the present disclosure. The laser processing machine according to the present disclosure is preferably a UV / visible light laser with a wavelength of 0.25 μm to 0.6 μm, a near-infrared laser with a wavelength of about 1 μm, or a far-infrared laser with a wavelength of about 10 μm.

[0105] Many resins absorb UV and visible laser light, so there is no need to use a laser light absorber. However, if the absorbance is low, it is possible to add a small amount of coloring pigment to increase the absorbance and speed up the processing speed. The amount added is preferably 10 weight percent or less, as it does not affect the electrical properties.

[0106] If the insulator 106 is 50 μm or thicker, the processing speed drops rapidly and productivity decreases due to the principle of UV / visible laser. Processing with UV / visible laser is excellent for insulator 106 up to a thickness of 50 μm, but is not suitable for thicknesses greater than that. If the insulator 106 is less than 50 μm, UV / visible laser can be used. By adding color pigments, it can be used even if the insulator 106 is more than 50 μm thick. The amount of coloring added can be increased to speed up the processing speed.

[0107] The insulator 106 preferably contains 30% by weight or more of a polymer containing 80 mol% or more of an alkene, and a laser light absorber, and when the insulator 106 has a thickness of 50 μm, the minimum transmittance of light having a wavelength of 0.2 μm or more and less than 0.8 μm is 85% or less. A color pigment can be used as the laser light absorber for the wavelength of 0.2 μm or more and less than 0.8 μm.

[0108] Color pigments include cyanine blue, cyanine green, yellow ocher, red iron oxide, permanent red, carbon black, titanium oxide, and zinc oxide. In addition, organic compounds such as benzotriazoles, benzophenones, and cyanoacrylates are also suitable as laser light absorbers with wavelengths of 0.2 μm or more and less than 0.8 μm.

[0109] Processing with UV and visible light lasers uses long and short pulse processing, which produces a smooth processed surface with a clean shape, resulting in a good finish.

[0110] Near-infrared lasers, such as YAG lasers or fiber lasers, and far-infrared lasers, such as carbon dioxide lasers, have high processing speeds and excellent productivity even when the insulator 106 is thick. However, polymers containing 80 mol % or more of alkenes hardly absorb light with wavelengths of around 0.8 μm to 11 μm, so linear grooves 206 cannot be formed with far-infrared lasers. To achieve this, it is necessary to blend a laser light absorber into the insulator 106. When the insulator 106 contains 30 wt % or more of a polymer containing 80 mol % or more of alkenes and contains a laser light absorber, linear grooves 206 can be formed with near-infrared laser light and far-infrared laser light.

[0111] By having the insulator 106 contain 30% by weight or more of a polymer containing 80% by mole or more of an alkene, the insulator 106 can be made inexpensive, and by having the insulator contain a laser light absorber, the speed at which the linear grooves 206 are formed by the near-infrared laser light and the far-infrared laser light can be increased, and the smoothness and dimensional accuracy of the machined surface can be improved. When the insulator 106 contains a laser light absorber and has a thickness of 50 μm, the insulator 106 needs to have a minimum transmittance of 85% or less for light with a wavelength of 0.8 μm or more and 11.0 μm or less.

[0112] Fig. 2(E) is a cross-sectional view of the portion where the conductor electrode 105 is formed. Fig. 6(A) is a top view of Fig. 2(E) and shows an outline of the positional relationship when forming the linear groove 206 and the hole 207 as a via hole. The formation of the linear groove 206 is an important step in this disclosure because it determines the outer peripheral shape of the shielded thin flat cable 101 and forms all end faces including the long and short sides.

[0113] FIG. 6(B) shows the state where the linear grooves 206 are formed by cutting using a combination of laser processing and a blade or a router bit. The white parts of the linear grooves 206 are the parts where cutting processing has been performed. FIG. 6(A) shows the state where all the linear grooves 206 are formed by laser processing. FIG. 6(Aa) is a cross-sectional view in the a direction of FIG. 6(A). The metal film 202C does not penetrate. This is the same as FIG. 2(E). FIG. 6(Bb) and (Bc) are cross-sectional views in the b direction and c direction of FIG. 6(B). When the linear grooves 206 are cut using a blade, the metal film 202C is also broken. If the cable is divided into individual pieces at this stage, the metal plating process in the subsequent process becomes complicated. In addition, it is impossible to manufacture the thin flat cable 101 shielded as an assembly, which impairs productivity. Therefore, the metal film 202C needs to be at least partially left in order to fix the individual pieces, and laser processing is suitable for leaving the metal film 202C.

[0114] FIG. 2(F) shows a process of forming a metal film 202D in the linear groove 206 in the state of FIG. 2(E), and a process of forming a metal body in the hole 207 as a via hole to provide a via hole 208 for drawing out conduction from the conductor 204. In the process of forming the metal film 202D in the linear groove 206, the metal film 202D is formed on the wall surface 205 of the linear groove 206. In addition, the metal body of the via hole 208 is formed by covering the via hole 208 with a metal. The metal film 202D and the metal body of the via hole 208 are suitably formed by a metal plating method. Usually, the exposed part of the inner layer electrode 214 as the metal film 202A and the bottom of the hole 207 as a via hole are cleaned, the surface other than the insulator 106 is made conductive, and then metal plating is performed. The metal film 202 that continuously covers the entire outer circumferential surface of the shielded thin flat cable 101 of the present disclosure is formed by metal plating to form the metal film 202D.

[0115] Metal plating is usually performed in the order of desmear treatment, catalyst formation, electroless plating, and electrolytic plating. Desmear treatment is necessary when foreign matter such as smear remains on the metal film surface, and is not necessary when the metal film surface is clean. Desmear treatment can be performed in a dry method using plasma or a wet method using an oxidizing agent such as permanganic acid, but in this disclosure, the dry method is superior in terms of preventing water absorption. The catalyst formation, electroless plating, and electrolytic plating methods can be performed using chemical systems such as those of ATOTECH, JCU, DOW CHEMICAL, Uemura Kogyo Co., Ltd., Okuno Pharmaceutical Industries Co., Ltd., and MacDermid Enthon Co., Ltd. In order to minimize moisture absorption, instead of the wet catalyst formation, the metal film 202 may be continuously formed on the surface of the insulator 106 by a dry method such as sputtering. As a method for making the metal film conductive, instead of the catalyst formation and electroless plating, the black hole system of Japan MacDermid Co., Ltd. can also be used.

[0116] Fig. 2(G) shows a process of removing a portion of metal film 202A shown in Fig. 2(F). This is a process of removing a portion of metal film 202A to form gap 218 between conductor electrode 105 and metal film 202A. Metal film 202A around the portion that will become conductor electrode 105 is removed to form gap 218. The range of removal is such that no current flows between the edge of conductor electrode 105 formed by the removal and the edge of metal film 202A that will become metal film 202.

[0117] The metal film 202A can be removed in a circuit formation process similar to that for forming the conductor 204 in Fig. 2(B). That is, the unnecessary parts of the metal film 202A can be removed by a procedure such as forming an etching mask, forming a resist layer, exposing, developing, etching, and peeling off the etching mask, to form a desired shape.

[0118] FIG. 2(H) shows a process of forming a solder mask 211 as an insulating layer on the surface of the metal film 202 of the laminate shown in FIG. 2(G), and cutting the metal film 202C to separate it. The solder mask 211 can be provided with an opening as necessary to expose the conductor electrode 105. The method of forming the solder mask can be a method commonly used in the manufacture of printed wiring boards. Specifically, a method of forming a solder mask ink by a photographic method or silk screen printing, a method of forming a film-like solder mask by a printing method, etc. can be used. Examples of solder mask ink include the PSR series made by Taiyo Ink Mfg. Co., Ltd., the PAF series and DSR series made by Tamura Mfg. Co., Ltd., and the SPSR series made by Sanwa Chemical Industry Co., Ltd. As film-like solder masks, Raytec made by Hitachi Chemical Co., Ltd., the PSR series made by Taiyo Ink Mfg. Co., Ltd., etc. can be used. It is also possible to form a solder mask on the surface of the exposed insulator 106. It is also possible to perform the next cutting step without forming the solder mask 211.

[0119] The shielded thin flat cable 101 is divided into individual pieces by cutting the metal film 202C along the linear grooves 206. The cutting for dividing into individual pieces can be performed using a cutting method for flexible wiring boards, and generally, cutting is performed using a die, a router, or a laser processing machine. The present disclosure produces the shielded thin flat cable 101 as an assembly, and can finally divide it into individual pieces, resulting in good work efficiency.

[0120] Manufacturing the shielded thin flat cable 101 as an assembly means forming multiple rows of the shielded thin flat cables 101 in parallel in the longitudinal direction as shown in Fig. 2 and finally dividing them into individual pieces to simultaneously obtain multiple shielded thin flat cables 101. Also, the shielded thin flat cables 101 in the longitudinal direction may be formed in multiple rows in series.

[0121] It is also possible to form gap 218 as shown in Fig. 2(J) during the process of Fig. 2(B), but gap 218 will also be plated with metal in the process of forming metal film 202D on wall surface 205 of linear groove 206 in Fig. 2(F) and in the plating process of forming a metal body in hole 207 as a via hole. Therefore, it is inconvenient to form gap 218 as shown in Fig. 2(J) during the circuit formation process of Fig. 2(B).

[0122] FIG. 3 shows a process different from FIG. 2. In FIG. 3(A), similarly to FIG. 2(A), a metal film 202A and a metal film 202B are laminated on both sides of a film-like insulator 106A. In FIG. 3(B), a conductor 204 and an inner layer electrode 214 are formed, and unlike FIG. 2(B), a groove forming opening 212 and a via hole drilling opening 209 are not formed. In FIG. 3(C), a film-like insulator 106B and a metal film 202C are laminated in order on the film-like insulator 106A and the formed conductor 204 and inner layer electrode 214. FIG. 3(D) shows a laminate obtained by the process of FIG. 3(C). In FIG. 3(E), a groove forming opening 212 and a via hole drilling opening 209 are provided in the metal film 202C by a circuit forming process. In FIG. 3(F), a linear groove 206 and a hole 207 as a via hole are formed. Fig. 3(G) shows a process of forming a metal film 202D on the wall surface 205 of the linear groove 206, and a process of forming a metal body in the hole 207 serving as a via hole. Fig. 3(H) shows a gap 218 being formed.

[0123] It seems that the process of FIG. 3 can also produce a shielded thin flat cable 101 similar to that of FIG. 2. As shown in FIG. 2(B), the front and back of one laminate are simultaneously subjected to a circuit formation process, so that the front and back positions can be accurately aligned. The inner layer electrode 214 and the opening 209 for drilling a via hole must be accurately aligned. If the inner layer electrode 214 and the opening 209 for drilling a via hole are not aligned, the inner layer electrode 214 and the conductor electrode 105 will not conduct electricity. In the method of FIG. 3, the inner layer electrode 214 and the opening 209 for drilling a via hole are formed on laminates in different states. When the lamination of FIG. 3(C) is performed by thermocompression, heat is applied to the insulator 106. This process may cause the insulator 106 to flow due to heat, resulting in a change in the position of the inner layer electrode 214. As a result, the positions of the inner layer electrode 214 and the opening 209 for drilling a via hole may not be aligned, and electricity may not flow between the inner layer electrode 214 and the via hole 208.

[0124] Polyimide, which is currently commonly used as an insulator, has high heat resistance and hardly deforms or shrinks during thermocompression bonding, so the positions of the inner layer electrode 214 and the opening 209 for drilling the via hole can be accurately aligned even in the process of Figure 3.

[0125] When a polymer with a relatively low melting point is used for the insulator 106 of the shielded thin flat cable 101 of the present disclosure, it is necessary to perform the circuit formation process simultaneously on the front and back of a single laminate, as shown in Figure 2 (B), and to accurately align the inner layer electrode 214 with the opening 209 for drilling a via hole in order to obtain a shielded thin flat cable 101 of excellent quality.

[0126] (Embodiment 2) Shielded thin flat cable 101 according to embodiment 2 is shown in Figures 4(H) and (I). Figure 4(H) shows a cross section of terminal portion 103. Figure 4(I) shows a cross section of conductor portion 102. Embodiment 2 has conductor-parallel metal film 215 in parallel with conductor 204 and inner layer electrode 214. Conductor-parallel metal film 215 is formed from metal film 202B, which is the same as conductor 204 and inner layer electrode 214. Therefore, the material and thickness are the same as conductor 204 and inner layer electrode 214. Conductor-parallel metal film 215 is electrically connected to metal film 202, which continuously covers the outer surface of shielded thin flat cable 101, and serves as ground.

[0127] The distance between the end of the conductor parallel metal film 215 and the ends of the conductor 204 and the inner layer electrode 214 is 10 μm or more. If it is less than 10 μm, there is a concern that a short circuit may occur between the conductor parallel metal film 215 and the conductor 204 and the inner layer electrode 214. Within this range, the distance between the conductor 204 and the inner layer electrode 214 may vary depending on the location. It is preferable that the distance between the conductor 204 and the inner layer electrode 214 is the same at all locations. In this case, as shown in FIG. 4(J), the end of the conductor parallel metal film 215 is provided along the shapes of the conductor 204 and the inner layer electrode 214.

[0128] By providing the intervals as described above, the ends of the conductor-parallel metal film 215 do not have to be provided along the conductor 204 and the inner layer electrode 214. The conductor-parallel metal film 215 is electrically connected to the metal film 202, and therefore the potential of the conductor-parallel metal film 215 needs to be the same as that of the metal film 202. For this reason, it is preferable that the ends of the conductor-parallel metal film 215 that are not on the conductor 204 and inner layer electrode 214 side are connected to the metal film 202 at the end faces in the longitudinal and lateral directions of the thin flat cable 101 that is shielded all around.

[0129] The conductor parallel metal film 215 can stabilize the signal transmission of the conductor 204 and improve the transmission characteristics of the shielded thin flat cable 101.

[0130] In the conventional flat cable shown in Fig. 7, the metal film 202A and the metal film 202C are connected by the through hole 108. In the shielded thin flat cable 101 of the present disclosure, the metal film 202 is provided continuously on the surface of the insulator 106, and the metal films 202 above and below the flat surface are conductive via the metal films 202 provided on the end faces in the longitudinal and lateral directions of the shielded thin flat cable 101, and there is no need to provide the through hole 108. Furthermore, by connecting the end of the conductor parallel metal film 215 to the end face of the shielded thin flat cable 101, the potential is more stable than in the conventional flat cable provided with the through hole 108, the ground can be strengthened, and the transmission characteristics can be stabilized.

[0131] 4(H) and (I) are provided on both sides of the conductor 204 and the inner layer electrode 214, but may be provided on only one side. Also, may be provided partially along the conductor 204 and the inner layer electrode 214. Providing it over the entire circumference is more preferable because it improves the transmission characteristics of the shielded thin flat cable 101.

[0132] 4 shows a manufacturing process of the shielded thin flat cable 101 having the conductor parallel metal film 215. This manufacturing process is the same as the manufacturing process of the shielded thin flat cable 101 shown in FIG. 2, except for providing the conductor parallel metal film 215.

[0133] In Fig. 4(A), a metal film 202A and a metal film 202B are laminated on both sides of a film-like insulator 106A. In Fig. 4(B), a circuit formation process is performed on the metal film 202B to form a conductor 204, an inner layer electrode 214, and a conductor parallel metal film 215. A circuit formation process is performed on 202A to form an opening 212 for forming a groove and an opening 209 for drilling a via hole. In Fig. 4(C), a film-like insulator 106B and a metal film 202C are laminated in this order on the film-like insulator 106A and the formed conductor 204, inner layer electrode 214, and conductor parallel metal film 215. Fig. 4(D) shows the obtained laminate.

[0134] In Fig. 4(E), the insulator 106 is removed by laser processing to form linear grooves 206 and holes 207 as via holes. At this time, the linear grooves 206 are formed so that the ends of the conductor-parallel metal film 215 that are not on the conductor 204 and inner layer electrode 214 side are exposed. Therefore, the ends of the conductor-parallel metal film 215 that are not on the conductor 204 and inner layer electrode 214 side must be shaped to follow the linear grooves 206. A straight line is preferable.

[0135] 4(F), a metal film 202D is formed on the wall surface 205 of the linear groove 206, and a metal body is formed in the hole 207 serving as a via hole. An end of the conductor parallel metal layer 215 and the metal film 202D come into contact with each other to enable electrical conduction.

[0136] Fig. 4(G) shows a process in which a part of the metal film 202A shown in Fig. 4(F) is removed to form a gap 218. The metal film 202A around the portion that will become the conductor electrode 105 is removed to form a gap 218. Fig. 4(H) shows a process in which a solder mask 211 that serves as an insulating layer is formed on the surface of the metal film 202 of the laminate shown in Fig. 4(G) and the metal film 202C is cut into individual pieces. As in the first embodiment, a thin flat cable 101 that is shielded by an assembly may be manufactured.

[0137] (Embodiment 3) As shown in Fig. 2(C) of the first embodiment and Fig. 4(C) of the second embodiment, film-shaped insulator 106B is bonded to and in contact with film-shaped insulator 106A and conductor 204. In the third embodiment, the melting point of film-shaped insulator 106B bonded to film-shaped insulator 106A is 10°C lower than the melting point of film-shaped insulator 106A. That is, in shielded thin flat cable 101, the melting points of insulators 106 sandwiching conductor 204 differ by 10°C or more.

[0138] The difference between embodiment 3 and embodiments 1 and 2 is that the melting point of film-type insulator 106A and film-type insulator 106B on the side that is bonded to conductor 204, inner electrode 214, or parallel metal film 215 provided on the surface of film-type insulator 106A is 10°C lower than the melting point of film-type insulator 106A, and other than this, embodiment 3 is the same as embodiment 1 and embodiment 2.

[0139] By making the melting point of the film-shaped insulator 106B 10°C or more lower than that of the film-shaped insulator 106A, it is possible to ease the heating conditions when laminating the film-shaped insulator 106A and the film-shaped insulator 106B by thermocompression bonding, and since the insulator 106A does not melt, the positional relationship between the conductor 204, the inner electrode 214, or the parallel metal film 215 does not change, and it is possible to prevent the conductor 204, the inner electrode 214, or the parallel metal film 215 from being destroyed. In addition, the adhesive strength by lamination can be increased. If the temperature is less than 10°C, it is difficult to control the heating conditions, and it is difficult to melt the film-shaped insulator 106B without melting the film-shaped insulator 106A and obtain sufficient adhesive strength by thermocompression bonding with the film-shaped insulator 106A.

[0140] The insulator 106 contains 30% by weight or more of a polymer containing 80% by mole or more of an alkene. If polymers having similar or identical melting points are used as the polymers contained in the film-shaped insulator 106A and the film-shaped insulator 106B, it is necessary to strictly manage the heating temperature, the amount of pressure, and the timing of lamination. If the conditions are not appropriate, the molten polymer will flow out from the ends during lamination, causing unevenness in the thickness of the insulator 106. In addition, the molten polymer will flow into the groove formation opening 212 and the via hole drilling opening 209, so an inflow prevention film is required.

[0141] To prevent this, a bonding sheet can be inserted between film-shaped insulator 106A and film-shaped insulator 106B and bonded together at a low temperature. However, inserting a bonding sheet requires complicated processing steps, and considering the increased cost of using a bonding sheet, it is preferable not to use one. According to the method of embodiment 3, there is no need to use a bonding sheet.

[0142] By setting the melting point of film-shaped insulator 106B 10°C lower than the melting point of film-shaped insulator 106A and heating it to a temperature above the melting point of film-shaped insulator 106B and below the melting point of insulator 106A, sufficient adhesive strength can be obtained between film-shaped insulator 106A, conductor 204, inner layer electrode 214 or parallel metal film 215 and insulator 106B, which are necessary for shielded thin flat cable 101, without melting insulator 106A.

[0143] The film-like insulator 106B is melted and bonded to the film-like insulator 106A, the conductor 204, or the parallel metal film 215. It is preferable that the film-like insulator 106B is thin in order to suppress outflow from the ends due to melting and inflow of molten polymer into the groove formation opening 212 and the via hole drilling opening 209. The thickness of the film-like insulator 106B is 20 μm or more and 700 μm or less. As an adhesive layer, a thinner thickness is better, but a thickness of 20 μm or more and 700 μm or less is preferable in consideration of the transmission characteristics.

[0144] As shown in FIG. 8, the film-shaped insulator 106B can be two layers of the insulator 106C and the insulator 106D. It may be three or more layers. The film-shaped insulator 106B is made of at least two layers of the insulator 106C and the insulator 106D. The insulator 106D on the side that is in contact with the film-shaped insulator 106A and the conductor 204 and is bonded together has a melting point that is 10° C. or more lower than the melting point of the film-shaped insulator 106A that sandwiches the conductor 204. The melting point of the insulator 106C may be higher than the melting point of the insulator 106D. It may be equal to or higher than the melting point of the film-shaped insulator 106A. It may be possible to bond the insulator 106B and the metal film 202C together in advance, and then bond the insulator 106D and the film-shaped insulator 106A together by thermocompression bonding.

[0145] The film-like insulator 106B, which is made up of two layers of the insulator 106C and the insulator 106D, is formed by co-extrusion, so that sufficient adhesion can be obtained between the insulator 106C and the insulator 106D. The film-like insulator 106B, which is made up of at least the insulator 106C and the insulator 106D, may be obtained by other processing methods such as extrusion lamination and dry lamination, instead of co-extrusion. Since the insulator 106D is melted and laminated with the film-like insulator 106A, the conductor 204, or the parallel metal film 215, it is preferable that the insulator 106D is thin in order to suppress the outflow from the end due to melting and the inflow of the molten polymer into the groove forming opening 212 and the via hole drilling opening 209. The insulator 106D is 10 μm or less, more preferably 5 μm or less.

[0146] By thinning insulator 106D and adjusting insulator 106C to a thickness that satisfies electrical characteristics, it is possible to form a shielded thin flat cable 101 with stable dimensions and adhesion. The combined thickness of insulators 106C and 106D is preferably 20 μm or more and 700 μm or less.

[0147] When the film-shaped insulator 106A is homopolypropylene or block polypropylene, the film-shaped insulator 106B is suitably a random copolymer polypropylene of propylene and ethylene. If the melting point of the homopolypropylene or block polypropylene is, for example, 160°C, the melting point of the random copolymer polypropylene can be 130°C.

[0148] When the film-shaped insulator 106A is high-density polyethylene, the film-shaped insulator 106B is suitably linear low-density polyethylene. The melting point of the high-density polyethylene is, for example, 140°C, and the melting point of the linear low-density polyethylene can be 100°C to 120°C. When the film-shaped insulator 106A is linear low-density polyethylene, the film-shaped insulator 106B is suitably linear low-density polyethylene with an even lower melting point. When the melting point of the linear low-density polyethylene is, for example, 120°C, the melting point of the linear low-density polyethylene or low-density polyethylene with a lower melting point can be 100°C.

[0149] When the film-like insulators 106A and 106C are homopolypropylene or block polypropylene, the insulator 106D is suitably a random copolymer polypropylene of propylene and ethylene. If the melting point of the homopolypropylene or block polypropylene is, for example, 160°C, the melting point of the random copolymer polypropylene can be 130°C.

[0150] When the film-shaped insulators 106A and 106C are high-density polyethylene, the film-shaped insulator 106D is suitably linear low-density polyethylene. The melting point of the high-density polyethylene is, for example, 140°C, and the melting point of the linear low-density polyethylene can be 100°C to 120°C. When the film-shaped insulators 106A and 106C are linear low-density polyethylene, the insulator 106D is suitably linear low-density polyethylene with an even lower melting point. When the melting point of the linear low-density polyethylene is, for example, 120°C, the melting point of the linear low-density polyethylene or low-density polyethylene with a lower melting point can be 100°C.

[0151] The insulator 106D is preferably a copolymer of an alkene and a monomer having a carboxyl group. This can increase the adhesive strength with the conductor 204 and the inner layer electrode 214. The same applies to the parallel metal film 215. It is not necessary for the entire insulator 106D to be a copolymer of an alkene and a monomer having a carboxyl group. It is sufficient to provide it as a layer on the surface to be bonded to the conductor 204 and the inner layer electrode 214.

[0152] (Embodiment 4) The shielded thin flat cable 101 according to the fourth embodiment is formed by integrating a plurality of shielded thin flat cables in a planar direction.

[0153] In the first and second embodiments, one conductor 204 is formed in one shielded, thin, flat cable 101. As shown in Fig. 9(A), multiple conductors 204 can be provided in one shielded, thin, flat cable 101. Also, a shielded, thin, flat cable 101 can be formed by integrating multiple shielded, thin, flat cables wrapped in multiple insulators 106 isolated by metal films 202D in a planar direction. Other than integrating multiple shielded, thin, flat cables in a planar direction, this is the same as the first and second embodiments.

[0154] The right side of Fig. 9(A) shows a shielded thin flat cable in which multiple conductors 204 are wrapped in insulator 106 isolated by metal films 202D, and metal film 202 is continuously formed on the surface of insulator 106 except for the periphery of conductor electrode 105. The left side of Fig. 9(A) shows a shielded thin flat cable in which conductors 204 are wrapped in insulator 106 isolated by metal films 202D, and metal film 202 is continuously formed on the surface of insulator 106 except for the periphery of conductor electrode 105 of insulator 106. The multiple shielded thin flat cables, the shielded thin flat cable on the right side and the shielded thin flat cable on the left side, constitute an integrated shielded thin flat cable 101.

[0155] By integrating a plurality of shielded thin flat cables in the horizontal direction, it is possible to achieve the effect of wiring a plurality of shielded lines in a lightweight, thin, and high-density manner.

[0156] Fig. 9(A) shows a cross section of the conductor portion 102, and Fig. 9(B) shows a cross section of the terminal portion 103. This is the same as the first embodiment, except that a plurality of conductors 204 is provided in the shielded thin flat cable 101, and a plurality of shielded thin flat cables are integrated in the planar direction.

[0157] The distance between the multiple conductors 204 of the shielded thin flat cable shown on the right side of FIG. 9(A) is 5 μm or more and 10,000 μm or less. If it is less than 5 μm, there is a concern of crosstalk and short circuit. If it exceeds 10,000 μm, the product becomes large and the number of pieces per area is reduced, which is not practical. The interval between the multiple inner electrodes 214 is determined by the mounting design and is not particularly limited, but the interval is 10 μm or more. If it is less than 10 μm, there is a risk of short circuit during processing or soldering. In FIG. 9(A), the multiple inner electrodes 214 are provided at the same position in the longitudinal direction of the shielded thin flat cable 101, but the positions of the multiple inner electrodes 214 may be changed to change the length of the multiple conductors 204. The same applies to the shielded thin flat cable on the left side of FIG. 9(A), and the length may be different from that of the conductors 204 of the shielded thin flat cable on the right side.

[0158] FIG. 11 shows a manufacturing process for the shielded thin flat cable 101 in which a plurality of the shielded thin flat cables shown in FIG. 9 are integrated.

[0159] 11A shows a laminate in which metal films 202A and 202B are laminated on both sides of a film-like insulator 106A. This is obtained by the same process as in the first embodiment.

[0160] 11(B) shows a circuit formation process in which the metal film 202B is made into a plurality of necessary conductors 204 and inner layer electrodes 214, and the metal film 202A is made into a metal film 202 that is continuously formed on the surfaces of a plurality of necessary conductor electrodes 105 and insulators 106. Here, by removing a portion of the metal film 202A, a plurality of necessary openings 209 for drilling via holes and an opening 212 for forming a groove are formed.

[0161] 11(C) shows a process of laminating a film-shaped insulator 106B and a metal film 202C in that order onto the film-shaped insulator 106A, the formed plurality of conductors 204, and the inner layer electrode 214. The film-shaped insulator 106A and the film-shaped insulator 106B are laminated together by thermocompression bonding. The plurality of conductors 204 and the inner layer electrode 214 are sandwiched between the film-shaped insulator 106A and the film-shaped insulator 106B.

[0162] FIG. 11D shows a laminate formed by laminating a film-like insulator 106, a film-like insulator 106B, and a metal film 202C.

[0163] 11(E) shows a process of forming a plurality of linear grooves 206 and holes 207 as via holes, which are required parallel to the conductor 204 along both side surfaces of the conductor 204 and the inner layer electrode 214. The linear grooves 206 are formed by an apparatus capable of forming the linear grooves 206 and holes 207 as via holes by removing the insulator 106 without penetrating the metal film 202A on one side of the insulator 106, while leaving the metal film 202C on the other side. The apparatus is, for example, an apparatus equipped with a laser processing machine, a plasma chemical processing machine, a sandblaster, or the like. A laser processing machine is preferable because of its fast processing speed.

[0164] 11(F) shows a process of forming a metal film 202D in the multiple linear grooves 206 in the state of FIG. 11(E), and a process of forming a metal body in holes 207 as multiple via holes to provide via holes 208 for drawing out electrical continuity from the conductors 204. Metal plating is suitable for forming the metal film 202D and the metal body of the via holes 208. By metal plating the linear grooves 206 formed between one conductor 204 and three conductors 204, the shielded thin flat cable on the left side of FIG. 9(A) and the shielded thin flat cable on the right side can be isolated by the metal film 202D, and a configuration in which multiple shielded thin flat cables are integrated can be achieved.

[0165] 11(G) shows a process of removing a portion of the metal film 202A. This is a process of removing a portion of the metal film 202A to form a plurality of necessary gaps 218 between the conductor electrodes 105 and the metal film 202. Although not shown in the figure, a solder mask 211 serving as an insulating layer is formed on the outer surface of the shielded thin flat cable 101 as necessary.

[0166] 11(H) shows a process of cutting the metal film 202C into individual pieces. The metal film 202C is cut along the linear grooves 206 so as to have the outer shape of the integrated shielded thin flat cable 101, thereby dividing the shielded thin flat cable 101 into individual pieces.

[0167] As described in the first embodiment, the production efficiency can be improved by manufacturing the shielded thin flat cable 101 as an assembly and then dividing it into individual cables. The individual shielded thin flat cable 101 and the integrated shielded thin flat cable 101 may be formed at the same time and then divided into individual cables.

[0168] (Embodiment 5) The shielded thin flat cable 101 according to the fifth embodiment is formed by integrating a plurality of shielded thin flat cables in the planar direction and the vertical direction. The cables may not be integrated in the horizontal direction, but may be integrated only in the vertical direction.

[0169] In the first and second embodiments, one conductor 204 is formed in one shielded thin flat cable 101. As shown in Fig. 10(A), a shielded thin flat cable 101 can be formed by integrating a plurality of shielded thin flat cables in the horizontal and vertical directions. Other than the fact that a plurality of shielded thin flat cables 101 are integrated in the horizontal and vertical directions, this embodiment is the same as the first, second and fourth embodiments.

[0170] The top left of FIG. 10(A) shows a shielded thin flat cable in which a conductor parallel metal layer 215 is provided along the conductor 204 and the inner layer electrode 214, as in the second embodiment. The top right shows a shielded thin flat cable having a single conductor 204. The bottom left shows a shielded thin flat cable having a single conductor 204. The bottom right shows a shielded thin flat cable having multiple conductors 204. The shielded thin flat cable 101 in FIG. 10(A) is configured by integrating four shielded thin flat cables. These four shielded thin flat cables are isolated by metal films 202D and 202E.

[0171] The shielded thin flat cable 101 integrated in the vertical direction may have any configuration. The conductor 204 may be singular or plural. A conductor parallel metal film 215 may be provided in parallel with the conductor 204.

[0172] The fifth embodiment is different from the fourth embodiment in that a plurality of shielded thin flat cables are integrated in the vertical direction. Two or more shielded thin flat cables can be integrated in the horizontal direction, but it is appropriate to integrate two shielded thin flat cables in the vertical direction. When three or more shielded thin flat cables are integrated, the intermediate shielded thin flat cable must have a conductor electrode 105 on its end face, which complicates the configuration. It is also possible to provide a conductor electrode 105 on its end face and integrate three or more shielded thin flat cables in the vertical direction.

[0173] By integrating a plurality of shielded thin flat cables in the vertical direction, it is possible to obtain a shielded thin flat cable 101 that is smaller, lighter, and denser than when integrated on a plane.

[0174] 10A shows a cross section of the conductor portion 102, and FIG. 10B shows a cross section of the terminal portion 103. As shown in FIG.

[0175] FIG. 12 shows a manufacturing process for a shielded thin flat cable 101 in which a plurality of the shielded thin flat cables shown in FIG. 10 are integrated in the horizontal and vertical directions.

[0176] 12(A) shows two laminates in which metal films 202A and 202B are bonded to both sides of a film-like insulator 106A. The manufacturing process of the laminate is the same as that of embodiment 1. By using two laminates, two shielded thin flat cables can be integrated in the perpendicular direction.

[0177] FIG. 12B shows a circuit formation process in which openings 209 for drilling necessary via holes, openings 212 for forming grooves, conductors 204, inner layer electrodes 214, and conductor parallel metal films 215 are formed.

[0178] 10(A) are formed in the upper metal film 202 of the laminate constituting a plurality of shielded thin flat cables, and a plurality of conductors 204 and inner layer electrodes 214 are formed in the lower metal film 202 of the laminate. At the lower part in the vertical direction, a plurality of openings 209 for drilling via holes and an opening 212 for forming grooves are formed in the lower metal film 202 of the laminate constituting a plurality of shielded thin flat cables, and a plurality of conductors 204, inner layer electrodes 214 and conductor parallel metals 215 are formed in the upper metal film 202 of the laminate.

[0179] Fig. 12(C) shows the process of sandwiching metal film 202E between two film-like insulators 106, and laminating a laminate constituting the upper part of shielded thin flat cable 101 onto the upper film-like insulator 106 and a laminate constituting the lower part of shielded thin flat cable 101 beneath the lower film-like insulator 106. As shown in Fig. 12(C), five constituent materials are laminated together. Thermocompression bonding is an appropriate method for laminating them together.

[0180] FIG. 12(D) shows a laminate formed by bonding together a metal film 202 in which an opening 209 for drilling a via hole and an opening 212 for forming a groove are formed, an insulator 106 which encases a conductor 204, an inner electrode 214, and a conductor parallel metal film 215, a metal film 202E, the insulator 106 which encases the conductor 204 and the inner electrode 214, and a metal film 202 in which an opening 209 for drilling a via hole and an opening 212 for forming a groove are formed.

[0181] 12(E) shows a process of forming a plurality of linear grooves 206 and holes 207 as via holes, which are required in parallel to the conductor 204, in the insulators 106 above and below the metal film 202E along both side surfaces of the conductor 204 and the inner layer electrode 214. The linear grooves 206 are formed by linearly removing the insulators 106 above and below the metal film 202E by laser processing, leaving the metal film 202E, without penetrating the metal film 202 above the insulator 106 or penetrating the metal film 202 below the insulator 106, to form the linear grooves 206 and the holes 207 as via holes.

[0182] Fig. 12(F) shows a process of forming a metal film 202D in the linear grooves 206 of Fig. 12(E) and a process of forming a metal body in the holes 207 as via holes to provide via holes 208 for drawing out electrical continuity from the conductors 204. Metal plating is suitable for forming the metal body of the metal film 202D and the via holes 208. The wall surface 205 of the linear groove 206 formed between one conductor 204 and the conductor parallel metal film 215 provided along the inner electrode 214 is metal plated to form the metal film 202D, thereby forming the two shielded thin flat cables in the upper part of Fig. 10(A) isolated by the metal film 202D and the metal film 202E. Furthermore, by metal plating the wall surface 205 of the linear groove 206 formed between one conductor 204 and three conductors 204 to form a metal film 202D, two shielded thin flat cables at the bottom of Fig. 10(A) are formed, which are separated by the metal film 202D and the metal film 202E. A configuration can be formed in which a plurality of shielded thin flat cables are integrated in the horizontal and vertical directions.

[0183] FIG. 12(G) shows a process of removing a part of the metal film 202 to form a plurality of gaps 218 required between the conductor electrodes 105 and the metal film 202 .

[0184] 12(H) shows a process of removing an unnecessary portion of the metal film 202E. Although not shown in the figure, a solder mask 211 that serves as an insulating layer is formed on the outer surface of the shielded thin flat cable 101 as necessary.

[0185] As described in the first embodiment, the production efficiency can be improved by manufacturing the shielded thin flat cable 101 as an assembly and then dividing it into individual cables. The individual shielded thin flat cable 101 and the integrated shielded thin flat cable 101 may be formed at the same time and then divided into individual cables.

[0186] (Embodiment 6) 1(B), (B-1), (B-2) and (B-3), normally, conductor electrodes 105 that draw electrical continuity from conductor 204 and serve as terminals for transmitting and receiving signals are provided on the flat surface of shielded thin flat cable 101. Shielded thin flat cable 101 according to embodiment 6 is a shielded thin flat cable 101 having conductor electrodes 105 provided on its end surfaces as shown in FIG.

[0187] FIG. 13 shows a conductor electrode 105 provided on an end surface of a shielded thin flat cable 101. FIG. 13(A) shows a left side view, (B) shows a plan view, (C) shows a right side view, and (D) shows a bottom view. The conductor electrode 105 is provided on the end surface of the shielded thin flat cable 101 and on parts of the upper and lower sides of the flat surface. The metal film 202 and the conductor electrode 105 are separated by a gap 218 and do not conduct electricity. The conductor electrode 105 is a metal film that is continuous with a conductor 204 provided inside the shielded thin flat cable 101. In FIG. 13, the conductor electrode 105 is provided on the end surface in the longitudinal direction of the shielded thin flat cable 101, but it may be provided on the end surface in the transverse direction.

[0188] The conductor 204, conductor parallel metal film 215, conductor electrode 105, gap 218, insulator 106 and metal film 202 of the shielded thin flat 101 having a conductor electrode 105 on its end face in embodiment 6 are of the same material and shape as those in embodiments 1 and 2.

[0189] 14 shows the manufacturing process of the shielded thin flat cable 101 with the conductor electrode 105 on the end face. This manufacturing process is the same as that shown in FIG. 2 showing the manufacturing process of the first embodiment, except that the conductor electrode 105 is provided on the end face of the shielded thin flat cable 101. However, since the conductor electrode 105 on the end face is continuous with the conductor 204, there is no need to provide the via hole 208.

[0190] In Fig. 14(A), metal films 202A and 202B are attached to both sides of a film-like insulator 106A. In Fig. 14(B), a circuit formation process is performed on the metal film 202B to provide a conductor 204 and a groove forming opening 212. The conductor 204 is provided so as to be continuously drawn out from a portion that will become the end face of the shielded thin flat cable 101.

[0191] FIG. 14(B) shows a cross section of the conductor portion 102. FIG. 14(B-1) shows a plan view of FIG. 14(B). As shown in FIG. 14(B-1), the conductor 204 is bent so as to be drawn out to the portion that will become the longitudinal end face of the shielded thin flat cable 101. The conductor 204 may be drawn out linearly to the lateral end face of the shielded thin flat cable 101. As shown in FIG. 14(B-1), it is preferable that the conductor 204 is made wider than the width of the conductor 204 along the end face at the portion that will become the end face. By making the width wider, it is possible to reliably connect the conductor 204 to the metal plating 202D provided on the wall surface 205 of the end face.

[0192] In Fig. 14(C), a film-shaped insulator 106B and a metal film 202C are laminated in this order on the film-shaped insulator 106A and the formed conductor 204. Fig. 14(D) shows the resulting laminate.

[0193] 14(E), a linear groove 206 is formed by removing the insulator 106 from the groove forming opening 212 by laser processing. A wall surface 205 of the linear groove 206 is provided in contact with an end of the conductor 204 at a location that will become the end face of the shielded thin flat cable 101. This is for connecting the metal film 202D provided on the wall surface 205 of the linear groove 206 to the end of the conductor 204. The linear groove 206 may be formed by a combination of laser processing and router processing.

[0194] In FIG. 14(F), a metal film 202D is formed on wall surface 205 of linear groove 206 by metal plating, and the metal film 202D provided on wall surface 205 of linear groove 206 and the end of conductor 204 are connected.

[0195] Fig. 14(G) shows a cross section of the terminal portion 103 of the shielded thin flat cable 101. Fig. 14(G) shows a process of removing parts of the metal films 202A, 202C, and 202D shown in Fig. 14(F) to form gaps 218. The circuit formation process removes the metal film 202 around the portion that will become the conductor electrode 105 to form gaps 218 between the conductor electrode 105 and the metal film 202. The gaps 218 are provided in two places: on both sides of the flat surface of the shielded thin flat cable 101, and at an end surface of the shielded thin flat cable 101 that is continuous from the gaps 218 provided on the flat surface.

[0196] Fig. 14(H) shows a process of forming a solder mask 211, which serves as an insulating layer, on the surface of the metal film 202 of the laminate shown in Fig. 14(G), and cutting the metal film 202C into individual pieces. As in the first embodiment, a thin flat cable 101 shielded by an assembly may be manufactured.

[0197] FIG. 15 shows a shielded thin flat cable 101 having two conductors and a conductor electrode 105 provided on the end surface. FIG. 15(A) is a plan view corresponding to the process of FIG. 14(B-1). In the circuit formation process, two conductors 204 are formed from the metal film 202A and a conductor parallel metal 215 is provided on the outside of the two conductors 204. The two conductors 204 are bent so as to be drawn out to different end surfaces in the longitudinal direction of the shielded thin flat cable 101. As shown in FIG. 15(A), it is preferable to make the width of the conductor 204 wider than the width of the conductor 204 along the end surface at the end surface. By making the width wider, it is possible to reliably connect the conductor 204 to the metal plating 202D provided on the wall surface 205 of the end surface.

[0198] The thickness of the conductor 204 is preferably 9 μm or more and 100 μm or less. If it is less than 9 μm, the connection with the metal plating provided on the wall surface 205 of the end face cannot be securely made, and the wire is likely to break. If it exceeds 100 μm, the processing precision of the width of the conductor 204 becomes significantly poor.

[0199] FIG. 15(B) shows a shielded thin flat cable 101 in which conductor electrodes 105 are provided on both end faces. FIG. 15(B) shows a case in which gap 218 is formed by a circuit formation process. The end of gap 218 can be made straight. Removal of metal film 202D formed on wall surface 205 of linear groove 206 by a circuit formation process would make the resist film hardening process complicated because the surface is not flat. In order to form a circuit on the end face, the etching resist is not a dry film but a liquid etching resist is applied to the end face by electrostatic coating or roll coating. In addition, exposure is also performed to the end face, so it is performed by a method such as laser light. Since the circuit formation on the end face is different from the usual printed wiring board processing method, it is necessary to manage the conditions.

[0200] The step of removing a part of the metal film 202D formed on the wall surface 205 of the linear groove 206 to form the gap 218 may be performed by cutting. Specifically, cutting may be performed with a drill bit or a router bit. Fig. 15(C) shows the metal film 202D formed on the wall surface 205 removed by cutting, and the removed end surface is curved.

[0201] By providing the conductor electrode 105 on the end face, the conductor 204 is led out to the conductor electrode 105 using the end face, so there is no need to form an opening 209 for drilling a via hole. In addition, the end face and the metal film 202 above and below the flat surface can be used as part of the conductor electrode 105, so a fillet is formed during soldering, improving the soldering strength.

[0202] The shielded thin flat cable according to the present disclosure can be used in communication equipment that requires high-density mounting, equipment that uses high frequency and high speed signals, equipment that requires EMI countermeasures, equipment that requires chemical resistance, and the like, specifically, smartphones, IoT devices, communication base station peripheral equipment, automotive-related equipment such as ADAS, lithium-ion battery peripheral equipment, and the like. [Explanation of symbols]

[0203] 101··Shielded thin flat cable 102 Conductor section 103...Terminal section 105 Conductor electrode 106 Insulator 108··Through hole 202 Metal film 204 Conductor 205··Wall 206 Linear groove 207...Hole as via hole 208··Beer Hall 209 ··Opening for via hole drilling 211 Solder mask 212...Groove formation opening 214 Inner layer electrode 215··Conductor Parallel Metal Film 218··Gap

Claims

1. A conductor made of a metal, an insulator that sandwiches the conductor and encases the conductor other than a conductor electrode that is conductive with the conductor and exposed on a surface; and A shielded thin flat cable having a continuous metal film on the surface of the insulator other than around the conductor electrodes, a second film-shaped insulator attached to the conductor, the inner layer electrode and the first film-shaped insulator on a first film-shaped insulator surface on which an inner layer electrode conductive to the conductor electrode is formed, has a melting point that is 10°C or more lower than the melting point of the first film-shaped insulator, and a third film-shaped insulator having a melting point equal to or higher than the melting point of the first film-shaped insulator on the side opposite to the side of the second film-shaped insulator that sandwiches the conductor.

2. 2. The shielded thin flat cable according to claim 1, A shielded thin flat cable, characterized in that the first film-like insulation and the second film-like insulation contain 30% by weight or more of a polymer containing 80 mol % or more of an alkene.

3. 2. The shielded thin flat cable according to claim 1, 13. A shielded thin flat cable, wherein the second film-like insulator contains a copolymer of a monomer having a carboxyl group and an alkene.

4. 2. The shielded thin flat cable according to claim 1, 1. A shielded thin flat cable, wherein the first film-like insulator contains a copolymer of a monomer having a carboxyl group and an alkene.

5. 2. The shielded thin flat cable according to claim 1, A shielded thin flat cable, characterized in that when the first film-like insulation is homopolypropylene or block polypropylene, the second film-like insulation is a random copolymer polypropylene of propylene and ethylene.

6. 2. The shielded thin flat cable according to claim 1, 1. A shielded thin flat cable, wherein the first film-like insulation is high density polyethylene and the second film-like insulation is linear low density polyethylene.

7. 2. The shielded thin flat cable according to claim 1, A shielded thin flat cable, characterized in that a plurality of shielded thin flat cables each having a metal film continuously formed on the outer surface of the insulator encasing the conductor are integrally formed.

8. 8. The shielded thin flat cable according to claim 7, A shielded thin flat cable, characterized in that the metal film between a plurality of integrated shielded thin flat cables is continuous.

9. A metal film is attached to both sides of a first film-like insulator, a circuit forming step is performed on the metal film on one surface of the first film-like insulator to form a conductor and an inner layer electrode that is conductive to an electrode continuous with the conductor; forming a circuit on the metal film on the other surface to form an opening for a via hole; a second film-shaped insulator having a melting point 10° C. or more lower than the melting point of the first film-shaped insulator is laminated on the conductor and the inner layer electrode formed on one surface of the first film-shaped insulator, and a metal film is laminated on the second film-shaped insulator; removing the metal film on the other surface of the first film-shaped insulator, the first film-shaped insulator, and the second film-shaped insulator, or breaking the metal film on the other surface of the first film-shaped insulator, the first film-shaped insulator, the second film-shaped insulator, and the metal film on the second film-shaped insulator, thereby forming an end face of the shielded thin flat cable to have an outer peripheral shape of the shielded thin flat cable; A method for manufacturing a shielded thin flat cable, comprising forming a metal film on the end surface.

10. 10. The method for producing a shielded thin flat cable according to claim 9, A method for manufacturing a shielded thin flat cable, characterized in that a third film-shaped insulator having a melting point equal to or higher than that of the first film-shaped insulator is provided on the side opposite to the conductor side of the second film-shaped insulator.

11. 11. The method for producing a shielded thin flat cable according to claim 9 or 10, A method for producing a shielded thin flat cable, characterized in that the first film-like insulation and the second film-like insulation contain 30% by weight or more of a polymer containing 80 mol % or more of an alkene.

12. 11. The method for producing a shielded thin flat cable according to claim 9 or 10, A method for producing a shielded thin flat cable, comprising the steps of: making the second film-like insulator contain a copolymer of an alkene and a monomer having a carboxyl group.

13. 11. The method for producing a shielded thin flat cable according to claim 9 or 10, A method for producing a shielded thin flat cable, comprising the steps of: making the first film-like insulator contain a copolymer of an alkene and a monomer having a carboxyl group.

14. 11. The method for producing a shielded thin flat cable according to claim 9 or 10, A method for manufacturing a shielded thin flat cable, characterized in that when the first film-shaped insulation is homopolypropylene or block polypropylene, the second film-shaped insulation is a random copolymer polypropylene of propylene and ethylene.

15. 11. The shielded thin flat cable according to claim 9 or 10, A method for manufacturing a shielded thin flat cable, characterized in that when the first film-shaped insulator is high-density polyethylene, the second film-shaped insulator is linear low-density polyethylene.

16. 10. The method for producing a shielded thin flat cable according to claim 9, a circuit forming step is performed on the metal film on one surface of the first film-like insulator to form a conductor and an inner layer electrode that is conductive to an electrode continuous with the conductor; a circuit forming process is performed on the metal film on the other side, and a second film-like insulator, a metal film, another second film-like insulator, and the conductor of another intermediate product of the shielded thin flat cable are bonded to the conductor side of the first film-like insulator of the intermediate product of the shielded thin flat cable, the other second film-like insulator side being bonded to the conductor side of the first film-like insulator of the intermediate product of the shielded thin flat cable, the other second film-like insulator side being bonded to the conductor side of the first film-like insulator of the intermediate product of the shielded thin flat cable, A method for manufacturing a shielded thin flat cable, characterized in that a laser beam is irradiated onto the insulators above and below a shielded thin flat cable in which multiple shielded thin flat cable intermediate products are integrated vertically, the insulators are removed down to the metal film of the other shielded thin flat cable, and the metal film is formed on the wall surface of a groove formed by removing the insulators.

17. 10. The method for producing a shielded thin flat cable according to claim 9, a circuit forming step is performed on the metal film on one surface of the first film-like insulator to form a conductor and an inner layer electrode that is conductive to an electrode continuous with the conductor; a circuit forming process is performed on the metal film on the other side, and a second film-like insulator, a metal film, another second film-like insulator, and the conductor of another intermediate product of the shielded thin flat cable are bonded to the conductor side of the first film-like insulator of the intermediate product of the shielded thin flat cable, the other second film-like insulator side being bonded to the conductor side of the first film-like insulator of the intermediate product of the shielded thin flat cable, the other second film-like insulator side being bonded to the conductor side of the first film-like insulator of the intermediate product of the shielded thin flat cable, A method for manufacturing a shielded thin flat cable, comprising breaking the upper and lower metal films and the insulators along the outer shape of a shielded thin flat cable in which a plurality of shielded thin flat cable intermediate products are integrated vertically, and forming the metal film on the end face of the formed shielded thin flat cable.

18. 18. The method for producing a shielded thin flat cable according to claim 16 or 17, A method for manufacturing a shielded thin flat cable, comprising the steps of: forming the metal film between a plurality of integrated shielded thin flat cables in a continuous manner;

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