Shielded thin flat cable and method for manufacturing same

Abstract

In the present invention, obtained is a shielded thin flat cable in which there is sufficient adhesive force between a film-like insulator and a conductor, and an inner-layer electrode and another insulator, by heating to at least the melting point of the film-like insulator but no higher than the melting point of the another insulator, without melting the another insulator,　The present invention is a shielded thin flat cable comprising: a metal conductor; an insulator that grips the conductor and envelops the conductor except for a conductor electrode that is continuous with the conductor and exposed to the surface; and a metal film that connects to the surface of the insulator except around the conductor electrode. The melting point of a second film-like insulator that is affixed to the conductor at a surface of a first film-like insulator in which an inner-layer electrode continuous with the conductor and the conductor electrode is formed, the inner-layer electrode, and the first film-like insulator, is at least 10°C lower than the melting point of the first film-like insulator.

Description

Shielded thin flat cable and its manufacturing method

[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 method for manufacturing the same.

[0002] Coaxial cables, whose core material is 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, such as RF circuits inside electronic devices and their surrounding areas.

[0003] Coaxial cables generally have a core wire made of copper or other materials wrapped in an insulator such as polyethylene, which is then wrapped in a shielding layer called a braided wire made of a mesh of thin conductors, and finally covered with a protective coating such as vinyl chloride. The braided wire blocks electromagnetic waves from the outside, suppressing noise and attenuation and reducing electromagnetic wave leakage from the inside. It has a wide transmission frequency range, 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 substrates made of thermoplastic resin, such as flexible wiring boards for high-density packaging 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 line conductors and ground conductors are provided on a wiring board, with ground conductors that are wider than the line conductors facing both sides of the line conductors (see Patent Documents 1 and 2). Because the triplate line has ground conductors on both sides, it has the advantage of suppressing external noise and making it less likely to produce a phenomenon known as unwanted radiation or unwanted emission.

[0005] It has been proposed to provide a wiring board that is easy to bend even when a triplate line is provided, and that is less likely to experience deterioration in transmission characteristics even when 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 insulator of such a flat cable is exposed to the outside air along its short sides, and the exposed insulator is exposed to water vapor, which penetrates into the interior of the insulator and causes it to absorb moisture. The absorbed water affects the transmission characteristics. Insulators with high moisture absorption rates are easily affected by water vapor, and this effect is particularly noticeable in the high-frequency range, causing changes in transmission characteristics.

[0007] One method for strengthening longitudinal shielding is to wrap shielding tape (see Patent Documents 5 and 6), but this involves wrapping shielding film as a shielding layer, which creates gaps and contact resistance where the shielding film overlaps or contacts, making it impossible to achieve complete shielding. Furthermore, overlapping shielding films make the flat cable thicker. Furthermore, organic substances such as adhesive and bonding layers are exposed to the air at the contact points, which causes the insulators to absorb moisture.

[0008] The moisture absorption mentioned above changes the electrical properties of the insulator, which in turn changes the transmission characteristics of the cable. The effect of moisture absorption on transmission characteristics 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, because the cable is cut into individual pieces along the transverse direction, the cross section is not plated, leaving the conductor and insulator exposed. This means that the transverse end faces are affected by humidity and allow water vapor to penetrate. Therefore, in this case, for flat cables that require stable transmission characteristics, there are restrictions on the use of highly hygroscopic resins as insulators. Furthermore, in order to connect to other components, new terminals must be formed.

[0010] The recent trend toward higher communication frequencies, such as 5G communications, and faster transmission speeds in semiconductors has created a demand for lower transmission loss in transmission lines. This demand requires insulators with low transmission loss. For example, general-purpose hydrocarbon resins such as polyethylene, polystyrene, and polypropylene have low transmission loss, good processability, 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 mobile devices and in-vehicle devices, which require these properties.

[0011] In flat cables with a structure in which the resin insulator is exposed to the outside, the temperature reaches about 250°C during the reflow soldering process, so using a general-purpose hydrocarbon resin for the insulator can cause defects such as peeling of the shielding metal film and the insulator during heating, and resin flow out from the end face of the flat cable.For this reason, currently, highly heat-resistant resins such as fluororesin and liquid crystal polymer are used as insulators for applications involving high-speed transmission of high frequencies.

[0012] Furthermore, flat cables that use copper wires as conductors can only be formed in a uniform shape along the length, and flat cables with multiple conductors have difficulty forming bent shapes while maintaining flatness. Furthermore, the ends of the copper wires are exposed through the insulating resin.

[0013] To address this phenomenon, thin wiring boards with triplate lines or microstrip lines made of low-transmission-loss resins, such as liquid crystal polymers, have been proposed (see Patent Document 3). These wiring boards allow for the formation of circuits similar to flexible wiring boards, allowing multiple signal lines to be formed on a single wiring board, and are 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 limits to ground stability because the top and bottom grounds are connected by vias. As we move toward even higher frequencies and speeds, 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 its high moisture absorption rate means that 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 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. As the use of high-frequency bands increases in the future, further stabilization of transmission characteristics will be required, making it necessary to minimize the effects of water vapor from the outside air.

[0016] Polyimide and air-containing resins absorb moisture due to the penetration of water vapor in the air, causing significant changes in their electrical properties. This makes them difficult to use in current FFC (Flat Flexible Cable), and fluororesins such as PTFE or liquid crystal polymers are used instead. However, these resins are expensive, require high-temperature processing, and have poor adhesive properties, making them difficult to produce and limiting their range of use.

[0017] In addition to the inherent flat cable characteristics of thin and flexible flat cables, flat cables for high-speed and high-frequency transmission are required to be transmission lines with stable transmission characteristics that are not affected by moisture absorption from the outside air, to have high electromagnetic wave shielding effects, to have heat resistance to withstand soldering and other processes, to be flame retardant, and to be easily manufacturable and use inexpensive materials.

[0018] In response to the above requirements, a shielded thin flat cable and its manufacturing method have been proposed that has stable transmission characteristics unaffected 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 (see Patent Document 8). Figure 1 is a diagram explaining Patent Document 8, showing the structure of a shielded thin flat cable that is unaffected 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 used to accommodate complex shapes.

[0020] Currently widely used FFCs that use polyimide as an insulator have poor alkali resistance, limiting their use around lithium-ion batteries, for example. Liquid crystal polymers have better alkali resistance than polyimide, but it is still not sufficient. Furthermore, lamination is difficult with PTFE, a representative fluororesin, making it difficult to create a multilayer structure like the one shown in Figure 1. Therefore, flat cables that use an insulator with excellent alkali resistance are desired.

[0021] JP 2011-71403 A JP 2017-188307 A International Publication WO2014 / 156422 JP 2010-182576 A JP 5-242736 A International Publication WO2016 / 104066 JP 61-131306 A International Publication WO2020 / 195784

[0022] Diatrend Co., Ltd., Glossary, Coaxial Cable

[0023] Currently, flexible wiring boards are widely used to connect components such as cameras and displays inside mobile devices, including smartphones, to the main board. Meanwhile, coaxial cables are generally used for RF components. Display-equipped devices, such as smartphones, tend to be larger, so reducing the thickness of the cable is crucial to making the smartphone smaller and lighter. However, it is difficult to make coaxial cables thinner, and recently, their thickness has become an obstacle to the packaging design of devices. In other words, thinner cables are necessary for packaging in devices with thickness limitations.

[0024] In mobile devices such as smartphones, the functionality of cameras and displays is becoming more sophisticated, the circuit scale of application processors is increasing as applications evolve, and batteries are becoming larger as transmission speeds become faster, making it difficult to fit all of these functions and components into the limited space inside the housing.On the other hand, the number of wireless types used by smartphones is also increasing, and the number of wires connecting antennas to devices and wires connecting components to 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, has a high electromagnetic wave shielding effect, can be soldered even when a general-purpose thermoplastic resin with low heat resistance is used for the insulator, and can be used to accommodate complex shapes, by covering the insulator surrounding the conductor with a metal film.

[0026] When a general-purpose thermoplastic resin with low heat resistance is used as an insulator in the manufacture of a shielded thin flat cable, the resin flows out from the end faces during the lamination process using thermocompression bonding, 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 signal lines with low transmission loss, it is important to match the characteristic impedance of the signal line, via land, and conductor electrode 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 prone to dimensional changes and deformation due to thermal and mechanical stress. Therefore, compared to highly heat-resistant thermosetting resins such as polyimide and epoxy resin, the accuracy of layer alignment during processing is poor, resulting in larger diameters of the signal line and via land.

[0028] As described in Patent Document 8, when forming grooves in an insulator, if the laser processing machine that forms the grooves has extremely low absorption of laser light, the laser will pass through a general-purpose thermoplastic resin that has 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 best formed using laser light, especially infrared light. When using ultraviolet or visible light lasers, the processing speed is slow and the lifespan 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 carbon dioxide laser processing efficiently, the processing wavelength is mainly around 10 μm, so the insulator must be able 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 undergo shape changes 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 and via lands, the conductor electrodes, and the 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.

[0034] The shielded thin flat cable according to the present disclosure is a shielded thin flat cable comprising: a conductor made of metal; an insulator sandwiching the conductor and encasing the conductor except for conductor electrodes that are conductive to the conductor and exposed on the surface; and a metal film that is continuous on the surface of the insulator except for around the conductor electrodes, wherein the melting point of a second film-like insulator bonded to the conductor, the inner-layer electrodes, and the first film-like insulator on a first film-like insulator surface on which the conductor and inner-layer electrodes that are conductive to the conductor electrodes are formed is 10°C or more lower than the melting point of the first film-like insulator; and a third film-like insulator having a melting point equal to or higher than the melting point of the first film-like insulator on the surface of the second film-like insulator opposite the surface sandwiching the conductor. Furthermore, 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 encases 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 on the surface of the insulator other than around the conductor electrodes, wherein 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 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.

[0035] In addition, in 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.

[0036] In the shielded thin flat cable according to another embodiment of the present disclosure, the first and second film-like insulators preferably contain 30% by weight or more of a polymer containing 80 mol% 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 mol% 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 another embodiment of 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 by 10°C or more.

[0038] In addition, in 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 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 laser light 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 continuously formed on the outer surface of the insulator enclosing the conductor are integrally formed.

[0041] In addition, 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 the shielded thin flat cable according to the present disclosure, it is preferable that when the first film-shaped insulator is homopolypropylene or block polypropylene, the second film-shaped insulator is random copolymer polypropylene of propylene and ethylene. In the shielded thin flat cable according to the present disclosure, it is preferable that when the first film-shaped insulator is high-density polyethylene, the second film-shaped insulator is linear low-density polyethylene. 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 electrodes.

[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, forming a circuit 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 forming a circuit on the metal film on the other side to form an opening for drilling a via hole, and then laminating a second film-like insulator having a melting point 10° C. or more lower than the melting point of the first film-like insulator on the conductor and the inner layer electrode formed on one side of the first film-like insulator, a metal film formed on the end surface of the shielded thin flat cable by laminating a metal film on the second film-like insulator, removing the metal film on the other side of the first film-like insulator, the first film-like insulator, and the second film-like insulator, or breaking 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 second film-like insulator, and forming a metal film on the end surface. Another embodiment of a method for manufacturing a shielded thin flat cable according to the present disclosure includes sandwiching a metal conductor, providing an insulator that surrounds the conductor except for conductor electrodes that are conductive with the conductor and exposed on the surface, and providing a metal film continuously on the insulator surface except for around the conductor electrodes, the insulator containing 30 wt % or more of a polymer containing 80 mol % or more of an alkene and a laser light absorber, and when the insulator is 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 the method for producing a shielded thin flat cable according to the present disclosure, it 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 the conductor side of the second film-like insulator.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 and second film-like insulators contain 30% by weight or more of a polymer containing 80 mol% 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 mol% 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 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.

[0048] In the method for manufacturing a shielded thin flat cable according to the present disclosure, it is preferable that when the first film-like insulator is homopolypropylene or block polypropylene, the second film-like insulator is random copolymer polypropylene of propylene and ethylene. In the method for manufacturing 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 manufacturing 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 manufacturing a shielded thin flat cable according to another embodiment of the present disclosure, it is preferable that the thin flat cables each sandwiching a plurality of the conductors are vertically integrated, the metal film on one of the upper and lower surfaces of the integrated shielded thin flat cable is removed, the insulator from which the metal film has been removed is irradiated with the laser light, the insulator is removed down to the metal film on the other shielded thin flat cable, and the metal film is formed on the wall surface of the groove formed by removing the insulator.

[0050] In a method for manufacturing a shielded thin flat cable according to another embodiment of 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 inner layer electrodes conductive to the conductors and electrodes continuous with the conductors, and perform a circuit formation process on the metal film on the other side to form openings for via holes, and then bond a second film-like insulator, a metal film, another second film-like insulator, and the conductors of another shielded thin flat cable intermediate product to the other second film-like insulator side of the first film-like insulator of a shielded thin flat cable intermediate product, and irradiate the upper and lower insulators of the shielded thin flat cable in which multiple shielded thin flat cable intermediate products are integrated vertically with laser light to remove the insulator down 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 a method for manufacturing a shielded thin flat cable according to another embodiment of the present disclosure, it is preferable to form the metal film continuously over the entire surface of the insulator except for around the conductors.

[0051] In a method for manufacturing a shielded thin flat cable according to another embodiment of the present disclosure, the method preferably includes: forming a circuit on the metal film on one side of the first film-like insulator to form an inner layer electrode electrically connected to a conductor and an electrode continuous with the conductor; forming a circuit on the metal film on the other side to form openings for via holes; bonding a second film-like insulator, a metal film, another second film-like insulator, and the conductor of another shielded thin flat cable intermediate product to the conductor side of the first film-like insulator; breaking the upper and lower metal films and insulators along the outer shape of a shielded thin flat cable formed by vertically integrating a plurality of the shielded thin flat cable intermediate products; and forming the metal film on an end face of the shielded thin flat cable. In a method for manufacturing a shielded thin flat cable according to another embodiment of the present disclosure, the groove is preferably formed by laser light; and forming the metal film 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 plurality of shielded thin flat cables is formed continuously. In the method for manufacturing a shielded thin flat cable according to another embodiment of the present disclosure, it is preferable that the insulator is provided to enclose the plurality of conductors except for the plurality of conductor electrodes that are conductive from the plurality of conductors and exposed on the surface, and the metal film is formed in multiple rows parallel to the conductors on the surface of the insulator except around the conductor electrodes, and then the insulator is cut into individual pieces parallel to the conductors.

[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.

[0054] 1 shows a shielded thin flat cable according to a first embodiment of the present disclosure, where (A) is a perspective view. (B) shows an enlarged perspective view of a terminal portion of the shielded thin flat cable. (C) shows 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) show plan views of the terminal portion of the exposed terminal 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. 1 shows a manufacturing process for the shielded thin flat cable according to the first embodiment of the present disclosure. 1 shows a manufacturing process for a conventional shielded thin flat cable. 1 shows a manufacturing process for a shielded thin flat cable according to a second embodiment of the present disclosure. 1 shows the inner layer wiring structure of the shielded thin flat cable according to an embodiment of the present disclosure. 1 shows the step of cutting the insulator in the manufacturing process for a conventional shielded thin flat cable. 1 shows the structure of a thin flat cable according to a conventional configuration. 1 shows a portion of the manufacturing process for the shielded thin flat cable according to a third embodiment of the present disclosure. 1 shows the structure of a shielded, thin flat cable in which a plurality of thin flat cables are integrated horizontally according to a fourth embodiment of the present disclosure. 2 shows the structure of a shielded, thin flat cable in which a plurality of thin flat cables are integrated horizontally and vertically according to a fifth embodiment of the present disclosure. 3 shows a manufacturing process for a shielded, thin flat cable in which a plurality of thin flat cables are integrated horizontally according to the fourth embodiment of the present disclosure. 4 shows a manufacturing process for a shielded, thin flat cable in which a plurality of thin flat cables are integrated horizontally and vertically according to the fifth embodiment of the present disclosure. 5 shows a shielded, thin flat cable in which a conductor electrode is provided on an end surface of the thin flat cable in a sixth embodiment of the present disclosure. 6 shows a manufacturing process for a shielded, thin flat cable in which a conductor electrode of the thin flat cable is provided on an end surface of the thin flat cable in a sixth embodiment of the present disclosure. 7 shows a shielded, thin flat cable in which a conductor electrode is provided on an end surface of the thin flat cable in a case where the thin flat cable has two conductors according to the sixth embodiment of the present disclosure.

[0055] 1 shows a shielded thin flat cable 101 according to a first embodiment of the present disclosure, where (A) is 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 where 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, where (B-1) is a plan view of B, and (B-2) and (B-3) show other terminal portions 103.

[0056] In addition to the inherent characteristics of flat cables, such as thinness and flexibility, and low transmission loss, flat cables are required to have the following characteristics: a transmission line that is resistant to the effects of external factors such as moisture absorption and has stable physical and electrical properties, a high electromagnetic wave shielding effect, heat resistance that can withstand soldering and other processes, flame retardancy, excellent chemical resistance, good processability, high productivity, and the ability to use 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 according to the present disclosure comprises a conductor 204 made of metal, an insulator 106 that sandwiches the conductor 204 and encases the conductor 204 except for 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 except around the conductor electrode 105.

[0058] 1A, a shielded thin flat cable 101 is composed of a terminal portion 103 having a conductor electrode 105 to 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 to 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 surrounding the conductor 204, and the metal film 202 provided continuously on the surface of the insulator 106.

[0059] 1B, the short end faces of the shielded thin flat cable 101 also have metal films 202. As shown in Fig. 1C, 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 through which the conductors 204 are conductive, and has a metal film 202 that extends continuously over the surface of the insulator 106 except for the periphery of 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 thermal deformation of the insulator 106, defects due to peeling, and the intrusion of water vapor from the outside air on the electrical properties of the conductor 204. It is acceptable for the metal film 202 to be absent from part of the surface of the insulator 106 to the extent that this does not result in damage to the shielding properties of the conductor 204, damage to electrical properties, deformation of the insulator 106, or peeling between the insulator 106 and the metal film 202.

[0061] To improve the shielding properties 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 area surrounding the conductor electrode 105. The metal film 202 is not provided around the conductor electrode 105. The area surrounding the conductor electrode 105 must be large enough to ensure that the conductor electrode 105 and the metal film 202 are not 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. Furthermore, because heat reduces the adhesive strength between the metal film 202 and the insulator 106, making them prone to peeling, it is desirable that the longitudinal and lateral end faces of the shielded thin flat cable 101 be covered with the metal film 202 without exposing the insulator 106. The longitudinal and lateral end faces are covered with the metal film 202, and it is preferable that the metal film 202 be provided on at least 95% of the surface of the insulator 106.

[0062] The exposed portion of the insulator 106 around the conductor electrode 105 where the metal film 202 is not provided 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, which may affect the transmission characteristics.

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

[0064] A conventional flat cable is shown in Figure 7. The flat cable does not have a metal film 202 on its longitudinal or lateral end faces. In such a flat cable, the insulator 106 may absorb moisture due to water vapor in the ambient air, which can degrade transmission characteristics. Furthermore, moisture absorption can reduce the adhesive strength between the metal film 202 and the insulator 106 due to heat from soldering reflow, which can lead to 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 in this distance. If the distance is less than 10 μm, there is a risk of electrical continuity between the end of the conductor electrode 105 and the end of the metal film 202. If the distance exceeds 1000 μm, there is a risk of water vapor from the outside air penetrating into the insulator 106, deteriorating transmission characteristics and heat resistance. There is also a risk of the shielding properties of the conductor 204 being impaired. Furthermore, there is a risk of the insulator 106 melting and changing 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 may vary around the periphery of 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 multiple rectangular conductor electrodes 105 are provided at the longitudinal ends of the shielded, thin flat cable 101. The metal film 202 is not provided around the conductor electrode 105, following the shape of the conductor electrode 105. The conductor electrode 105 may have any shape. Furthermore, multiple conductor electrodes 105 may be provided on a single conductor 204. The metal film 202 is used as ground.

[0067] As shown in FIG. 2(G), in the terminal portion 103, the conductor 204 is connected to the conductor electrode 105 via an inner layer electrode 214 and a via hole 208. The conductor electrode 105 is for connection to an external element, etc., and is used as a connector connection terminal, an SMT soldering electrode, a soldering terminal for connector fixation, a terminal for ACF (Anisotropic Conducting Film) connection, etc. 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 needed. The periphery of the conductor electrode 105 is configured to prevent electrical continuity between the metal film 202 and the conductor electrode 105 by an 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] The metal film 202, which is provided continuously on the surface of the insulator 106 except around the conductor electrode 105, prevents external water vapor and chemical solutions from penetrating into the insulator 106. Furthermore, when a flame is directed from the outside at the shielded thin flat cable 101, the metal film 202 prevents the flame from directly contacting the insulator 106, thereby improving the flame retardancy of the insulator 106.

[0070] The insulator 106 contains 30% by weight or more of a polymer containing 80 mol% or more of an alkene and a laser light absorber. When the insulator 106 is 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. 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. The insulator 106 may also be a styrene-based resin. A styrene-based resin is a polymer containing styrene as a monomer, and examples of styrene homopolymers include isotactic polystyrene, syndiotactic polystyrene, and attack polystyrene. Syndiotactic polystyrene, which has high heat resistance, is preferred. The insulator 106 may also be a copolymer of styrene and an alkene, a copolymer of styrene and a diene such as butadiene or isoprene, or a hydrogenated copolymer of styrene and a diene such as butadiene or isoprene. Mixtures of these resins are also acceptable.

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

[0074] The polymer preferably contains, as a monomer other than an alkene, 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, or SBS.

[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] Furthermore, 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, carbon black, carbon nanotubes, and titanium black are more suitable 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 also contain additives such as fillers, viscosity modifiers, lubricants, and flame retardants as appropriate, to the extent that the dielectric properties are not deteriorated.

[0078] The thickness of the insulator 106 is preferably 10 μm to 1000 μm, and more preferably 30 μm to 500 μm. If the thickness 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 the thickness is thicker than 1000 μm, the speed of laser processing to form grooves in the insulator 106 using a laser, as described below, becomes extremely slow.

[0079] By including 30% by weight or more of a polymer containing 80% by mole or more of an alkene in the insulator 106, it is possible to inexpensively manufacture a thin, shielded flat cable 101. However, polymers containing 80% by mole or more of an alkene have poor absorption properties for laser light with wavelengths of 0.8 μm or more and 11.0 μm or less, making it difficult to form grooves on the surface of the insulator 106 by irradiating the laser light. However, by including a laser light absorber in the insulator 106, it is possible to form grooves by irradiating the laser light. The laser light absorber is included in the insulator 106 so that, when the insulator 106 is 50 μm thick, the minimum transmittance of light with wavelengths of 0.8 μm or more and 11.0 μm or less is 85% or less. If the transmittance is 85% or more, forming grooves by irradiating the laser light becomes difficult or takes a long time.

[0080] The conductor 204 is preferably made of a material with good electrical conductivity, and is particularly preferably made of gold, silver, copper, or aluminum. Considering flexibility and 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 precision of the finished dimensional width of the conductor 204. This makes impedance matching difficult, making it undesirable as a conductor. Furthermore, if the width of the conductor 204 is less than 0.01 mm, the conductor loss increases, making it undesirable as a transmission line. Conversely, if the width of the conductor 204 exceeds 10 mm, the thickness of the insulator 106 required to obtain the desired characteristic impedance becomes too thick, making it unsuitable for a shielded thin flat cable 101 that pursues thinness.

[0082] The width of the conductor 204 has a significant impact on transmission characteristics, so the width must be precisely controlled. Furthermore, to improve the line width precision of the conductor 204, the MSAP (Modified Semi-Additive Process) method can be used. Furthermore, to improve transmission characteristics, if the conductor 204 is not gold or silver, it may be gold- or silver-plated. Since the shielded thin flat cable 101 according to the present disclosure has a stripline 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. To obtain the 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 will be difficult to achieve precision in width when manufacturing the conductor 204, and the insulator 106 used to encase the conductor 204 will become thick, making it unsuitable for a shielded thin flat cable 101 that pursues thinness.

[0084] The metal film 202 of the shielded thin flat cable 101 is made of a metal with good electrical conductivity, preferably gold, silver, copper, or aluminum, with copper being preferred. Considering flexibility and electrical conductivity, copper is most preferred. 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 and lateral end surfaces of the shielded thin flat cable 101 are preferably copper plated. The electrical resistivity of the metal film 202 is preferably 1 μΩ·m or less. To add functions such as oxidation prevention and noise reduction, the metal film 202 may be made of a combination of different metals; for example, nickel, zinc, chromium, or an iron-based alloy may 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 will occur, making it impossible to maintain the internal barrier properties, and the metal film 202 will melt during laser processing, making it impossible to form the linear grooves 206. Furthermore, the expansion of the insulator 106 during heating will cause cracks in the metal film 202. Furthermore, if the thickness exceeds 100 μm, the processing to form the linear grooves 206 and the holes 207 as via holes will become complicated and take a long time. If the metal film 202 is formed by plating, the plating time will be long, causing 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. Furthermore, 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 laser.

[0087] 2(G), in the terminal portion 103, the conductor 204 is connected to the conductor electrode 105 via an inner layer electrode 214 and a 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. 5A, the inner layer electrode 214 is formed continuously from the conductor 204. Therefore, its thickness and material are the same as those of the conductor 204. 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. 5B. The shape of the inner layer electrode 214 is preferably circular, but any shape may be used as long as it is equal to or larger than the cross section of the via hole 208. A secondary shape such as a teardrop shape may also be added. When the inner layer electrode 214 is circular, its diameter is typically 50 μm or more and 2 mm or less. A diameter of 100 μm or more and 800 μm or less is even more preferable. If the diameter is less than 50 μm, it is difficult to align the inner layer electrode 214 with the via hole 208. If the diameter exceeds 2 mm, it is difficult to match the characteristic impedance. The characteristic impedance of the signal line must be matched, and it is difficult to match the characteristic impedance of the inner layer electrode 214 and the conductor 204. Therefore, it is necessary to achieve characteristic impedance matching by making the diameter of the inner layer electrode 214 as small as possible.

[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 laser light, and then plating the hole 207 as a via hole formed by removing the insulator 106. Therefore, the cross section has a shape that is approximately circular. The plating is preferably performed with copper.

[0090] 2 shows a manufacturing method of the shielded thin flat cable 101 according to the present disclosure. The shielded thin flat cable 101 sandwiches a conductor 204 made of metal, and is provided with an insulator 106 that encases the conductor 204 except for the conductor electrodes 105 that are electrically connected to the conductor 204 and exposed on the surface. A metal film 202 is provided continuously on the surface of the insulator 106 except for the periphery of the conductor electrodes 105.

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

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

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

[0094] When bonding the metal films 202A and 202B 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 films 202A and 202B to enhance adhesive strength. The adhesive strength between the copolymer of a monomer having a carboxyl group and an alkene and the metal is increased by thermocompression bonding. In particular, when using polyethylene, which uses ethylene as the alkene, or polypropylene, which uses propylene as the alkene, as the polymer, it is preferable to use a resin obtained by graft-polymerizing maleic anhydride with polyethylene or polypropylene. It is preferable for the polymer to contain less than 20 mol %, and even more preferably less than 10 mol %, of a monomer having a carboxyl group. Less than 10 mol % minimizes the impact on transmission characteristics.

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

[0097] 2(C) shows the process of laminating a film-shaped insulator 106B and a metal film 202C in this 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, an insulator made of a different material may be used. The film-shaped insulators 106A and 106B are laminated together by thermocompression bonding. The conductor 204 and the inner layer electrode 214 are sandwiched between the film-shaped insulators 106A and 106B. Thermocompression bonding is preferably performed in a vacuum.

[0098] When laminating the conductor 204 and inner layer electrode 214 formed on the surface of the film-like insulator 106A to the film-like insulator 106B and the film-like insulator 106B to the metal film 202C by thermocompression bonding, it is preferable to provide a layer of a copolymer of a monomer having a carboxyl group and an alkene on both sides of the film-like insulator 106B to enhance adhesive strength. The adhesive strength between the copolymer of a monomer having a carboxyl group and an alkene and the 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 polymerizing maleic anhydride onto polyethylene or polypropylene.

[0099] It is preferable that the metal film 202C uses the same metal as the metal film 202A. The metal film 202C may be formed by laminating the film-shaped insulator 106B to the film-shaped insulator 106A and then laminating the metal film 202C sequentially, or by laminating the film-shaped insulator 106B and the metal film 202C simultaneously to the film-shaped insulator 106A. Alternatively, the film-shaped insulator 106B and the metal film 202C may be laminated together, and then the film-shaped insulator 106B may be laminated to the film-shaped insulator 106A. Figure 2D shows a stack 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. The linear grooves 206 are formed by removing the insulator 106 exposed in the groove-forming openings 212. 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] The hole 207 serving as a via hole is formed by removing the insulator 106 exposed at the opening 209 for drilling the via hole down to the inner layer electrode 214 without penetrating the metal film 202A.

[0102] The linear grooves 206 and the holes 207 serving as via holes are formed using, for example, a laser processing machine, a plasma processing machine, a sandblaster, or other device. A laser processing machine is preferred because of its fast processing speed. By forming the linear grooves 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 / visible light lasers. In this disclosure, deep engraving of the insulator 106 is required to form linear grooves 206 in the insulator 106. The deep engraving speed is significantly slow with UV / visible light lasers. Near-infrared and far-infrared lasers have fast processing speeds, making their use preferable.

[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 lasers, fiber lasers, and carbon dioxide laser processing machines are widely used due to their fast resin processing speed, and are preferred laser processing machines in this disclosure. The laser processing machine according to this disclosure preferably uses a UV / visible laser with a wavelength of 0.25 μm to 0.6 μm, a near-infrared laser with a wavelength of around 1 μm, or a far-infrared laser with a wavelength of around 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 this does not affect the electrical properties.

[0106] When the insulator 106 is 50 μm or thicker, the processing speed rapidly slows down due to the principles of UV / visible lasers, resulting in reduced productivity. Processing with UV / visible lasers is excellent for insulators 106 up to a thickness of 50 μm, but is unsuitable for thicknesses greater than that. UV / visible lasers can be used for insulators 106 less than 50 μm. By adding a coloring pigment, insulators 106 can be used even when the thickness exceeds 50 μm. The amount of coloring pigment added can be increased to increase 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] Examples of color pigments include cyanine blue, cyanine green, yellow ochre, 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 for wavelengths of 0.2 μm or more and less than 0.8 μm.

[0109] Processing with UV and visible light lasers involves long and short pulse processing, which results in 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 in the range of 0.8 μm to 11 μm, and therefore cannot form linear grooves 206 using 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 using near-infrared laser light and far-infrared laser light.

[0111] The insulator 106 contains 30% by weight or more of a polymer containing 80 mol% or more of an alkene, making the insulator 106 inexpensive, and the insulator 106 contains a laser light absorber, which increases the speed at which linear grooves 206 are formed by near-infrared laser light and far-infrared laser light, and improves the smoothness and dimensional accuracy of the machined surface. The insulator 106 containing the laser light absorber, when 50 μm thick, must 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 area where the conductor electrode 105 is formed. Fig. 6(A) is a top view of Fig. 2(E) and shows the general 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 the present disclosure because it determines the outer shape of the shielded thin flat cable 101 and forms all end faces, including the long and short sides.

[0113] FIG. 6B shows the linear grooves 206 formed by laser cutting using a combination of laser processing and a blade or router bit. The white portions of the linear grooves 206 indicate the areas that were cut. FIG. 6A shows all of the linear grooves 206 formed by laser processing. FIG. 6A-a is a cross-sectional view taken along the a-axis in FIG. 6A. The metal film 202C does not penetrate through the grooves. This is the same as FIG. 2E. FIGS. 6B-b and 6B-c are cross-sectional views taken along the b-axis and c-axis in FIG. 6B. Cutting the linear grooves 206 with a blade also fractures the metal film 202C. Slicing at this stage complicates the subsequent metal plating process. Furthermore, it becomes impossible to manufacture a shielded thin flat cable 101 as an assembly, which impairs productivity. Therefore, it is necessary to leave at least a portion of the metal film 202C in order to fix the individual pieces, and laser processing is suitable for leaving the metal film 202C.

[0114] 2(F) shows the process of forming a metal film 202D in the linear groove 206 in the state shown in FIG. 2(E) and the process of forming a metal body in the hole 207 serving as a via hole to provide a via hole 208 for conducting electrical current 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. Furthermore, the metal body of the via hole 208 is formed by coating the via hole 208 with metal. Metal plating is suitable for forming the metal film 202D and the metal body of the via hole 208. Typically, the exposed portion of the inner layer electrode 214 serving as the metal film 202A and the bottom of the hole 207 serving as a via hole is cleaned, and the surface other than the insulator 106 is made conductive, followed by metal plating. The metal plating to form the metal film 202D forms a metal film 202 that continuously covers the entire outer surface of the shielded thin flat cable 101 of the present disclosure.

[0115] Typically, metal plating involves the sequential steps of desmearing, catalyst formation, electroless plating, and electrolytic plating. Desmearing is necessary when smeared foreign matter remains on the metal film surface; it is not necessary if the metal film surface is clean. Desmearing can be performed using dry methods using plasma or wet methods using an oxidizing agent such as permanganate. In this disclosure, however, 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 from, for example, ATOTECH, JCU Corporation, DOW CHEMICAL, Uemura Industries, Ltd., Okuno Pharmaceutical Industries, Ltd., and MacDermid Enthon. To minimize moisture absorption, a continuous metal film 202 may be formed on the surface of the insulator 106 using a dry method such as sputtering, instead of wet catalyst formation. Furthermore, as a method for making the metal film conductive, the Black Hole system from Japan MacDermid can also be used instead of catalyst formation and electroless plating.

[0116] 2(G) shows a step of removing a portion of the metal film 202A shown in FIG. 2(F). This is a step of removing a portion of the metal film 202A to form a gap 218 between the conductor electrode 105 and the metal film 202A. The metal film 202A is removed from the periphery of the portion that will become the conductor electrode 105, thereby forming the gap 218. The area to be removed is such that no current flows between the edge of the conductor electrode 105 formed by the removal and the edge of the metal film 202A that will become the metal film 202.

[0117] The metal film 202A can be removed in the same circuit formation process as that used to form the conductor 204 in Fig. 2B. That is, unnecessary portions of the metal film 202A can be removed by a procedure including etching mask formation, resist layer formation, exposure, development, etching, and etching mask peeling, thereby forming a desired shape.

[0118] FIG. 2(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. 2(G), and then cutting the metal film 202C into individual pieces. The solder mask 211 can have openings, as needed, to expose the conductor electrodes 105. The solder mask can be formed using methods commonly used in the manufacture of printed wiring boards. Specifically, methods such as forming a solder mask ink using photography or silkscreen printing, or forming a film-type solder mask using a printing method can be used. Examples of solder mask inks include the PSR series manufactured by Taiyo Ink Mfg. Co., Ltd., the PAF series and DSR series manufactured by Tamura Corporation, and the SPSR series manufactured by Sanwa Chemical Industry Co., Ltd. Examples of film-type solder masks that can be used include Raytec manufactured by Hitachi Chemical Co., Ltd. and the PSR series manufactured by Taiyo Ink Mfg. Co., Ltd. Alternatively, a solder mask can be formed on the exposed surface of the insulator 106. Alternatively, the subsequent cutting process can be performed without forming the solder mask 211.

[0119] The shielded thin flat cable 101 is separated into individual pieces by cutting the metal film 202C along the linear grooves 206. The cutting to separate the shielded thin flat cable 101 can be performed using a cutting method for flexible wiring boards, and generally, cutting using a mold, a router, or a laser processing machine. The present disclosure provides high work efficiency by manufacturing the shielded thin flat cable 101 as an assembly and then separating it into individual pieces.

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

[0121] 2(J) during the process of Fig. 2(B), it is conceivable to form a gap 218 as shown in Fig. 2(J), but in the process of forming a metal film 202D on the wall surface 205 of the linear groove 206 of Fig. 2(F) and in the plating process of forming a metal body in the hole 207 serving as a via hole, the gap 218 will also be plated with metal. Therefore, it is inconvenient to form the 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 that shown in FIG. 2. In FIG. 3(A), similar to FIG. 2(A), metal films 202A and 202B are bonded to both sides of a film-like insulator 106A. In FIG. 3(B), a conductor 204 and an inner layer electrode 214 are formed, but unlike FIG. 2(B), groove-forming openings 212 and via-hole drilling openings 209 are not formed. In FIG. 3(C), a film-like insulator 106B and a metal film 202C are sequentially bonded onto 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 shown in FIG. 3(C). In FIG. 3(E), a circuit-forming opening 212 and a via-hole drilling opening 209 are formed in the metal film 202C by a circuit formation process. In FIG. 3(F), a linear groove 206 and a hole 207 serving as a via hole are formed. 3G 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. In FIG. 3H, a gap 218 is formed.

[0123] The process shown in Figure 3 appears to produce a shielded thin flat cable 101 similar to that shown in Figure 2. By simultaneously forming circuits on the front and back of a single laminate, as shown in Figure 2(B), the front and back positions can be accurately aligned. The inner layer electrodes 214 and the via hole openings 209 must be accurately aligned. If the inner layer electrodes 214 and the via hole openings 209 are not aligned, electrical continuity between the inner layer electrodes 214 and the conductor electrodes 105 will not occur. In the method shown in Figure 3, the inner layer electrodes 214 and the via hole openings 209 are formed on separate laminates. When the lamination shown in Figure 3(C) is performed by thermocompression bonding, heat is applied to the insulator 106. This process may cause the insulator 106 to flow due to heat, resulting in a shift in the position of the inner layer electrodes 214. As a result, the positions of the inner layer electrode 214 and the opening 209 for drilling the via hole may not be aligned, and there is a risk that the inner layer electrode 214 and the via hole 208 may not be electrically connected.

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

[0125] When a polymer with a relatively low melting point is used for the insulator 106 of the shielded thin flat cable 101 according to 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 FIG. 2(B), and to accurately align the inner layer electrodes 214 with the openings 209 for drilling via holes, in order to obtain a shielded thin flat cable 101 of excellent quality.

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

[0127] The distance between the end of the parallel-conductor metal film 215 and the ends of the conductor 204 and the inner-layer electrode 214 is 10 μm or more. If the distance is less than 10 μm, there is a risk of short-circuiting between the parallel-conductor 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 parallel-conductor metal film 215 is provided along the shapes of the conductor 204 and the inner-layer electrode 214.

[0128] By providing the spacing 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. Since the conductor-parallel metal film 215 is electrically connected to the metal film 202, the potential of the conductor-parallel metal film 215 needs to be the same as the potential of the metal film 202. Therefore, 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 on the longitudinal and lateral end faces 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 Figure 7, the connection between metal film 202A and metal film 202C is made by through-hole 108. In the shielded thin flat cable 101 of the present disclosure, metal film 202 is provided continuously on the surface of insulator 106, and the metal films 202 above and below the flat surface are electrically connected by metal films 202 provided on the longitudinal and lateral end faces of shielded thin flat cable 101, eliminating the need for through-hole 108. Furthermore, by connecting the end of conductor parallel metal film 215 to the end face of shielded thin flat cable 101, the potential is more stable than in conventional flat cables with through-holes 108, the ground can be strengthened, and transmission characteristics can be stabilized.

[0131] 4(H) and 4(I) are provided on both sides of the conductor 204 and the inner-layer electrode 214, but they may be provided on only one side. They may also be provided partially along the conductor 204 and the inner-layer electrode 214. Providing them around 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 the provision of the conductor parallel metal film 215.

[0133] In Fig. 4(A), metal films 202A and 202B are bonded to 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 conductors 204, inner layer electrodes 214, and conductor-parallel metal films 215. In Fig. 202A, a circuit formation process is performed to form groove formation openings 212 and via hole drilling openings 209. In Fig. 4(C), a film-like insulator 106B and a metal film 202C are bonded in this order on the film-like insulator 106A and the formed conductors 204, inner layer electrodes 214, and conductor-parallel metal films 215. Fig. 4(D) shows the resulting laminate.

[0134] 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] 4F, 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. The end of the conductor parallel metal layer 215 and the metal film 202D come into contact with each other to allow electrical conduction.

[0136] In Fig. 4(G), a portion 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 the gap 218. Fig. 4(H) shows a process of forming a solder mask 211 that serves as an insulating layer on the surface of the metal film 202 of the laminate shown in Fig. 4(G), and cutting the metal film 202C into individual pieces. As in the first embodiment, a thin flat cable 101 that is shielded by an assembly may be manufactured.

[0137] 2C of the first embodiment and FIG. 4C 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 lower by 10° C. or more than the melting point of film-shaped insulator 106A. That is, in the 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 film-type insulator 106A and the film-type insulator 106B on the side that is bonded to the conductor 204, inner electrode 214, or parallel metal film 215 provided on the surface of the film-type insulator 106A are at least 10°C lower in melting point than the film-type insulator 106A; otherwise, embodiment 3 is the same as embodiment 1 and embodiment 2.

[0139] By setting the melting point of the film-shaped insulator 106B at least 10°C lower than the melting point of the film-shaped insulator 106A, it is possible to relax the heating conditions when bonding the film-shaped insulator 106A and the film-shaped insulator 106B together by thermocompression bonding. Since the insulator 106A does not melt, the relative positions of the conductor 204, the inner electrode 214, or the parallel metal film 215 do not change, and damage to the conductor 204, the inner electrode 214, or the parallel metal film 215 can be prevented. Furthermore, the adhesive strength of the bonding can be increased. If the temperature is lower 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, thereby achieving sufficient adhesive strength by thermocompression bonding to 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 with similar or identical melting points are used for the film-shaped insulators 106A and 106B, the heating temperature, amount of pressure, and timing of lamination must be strictly controlled. If the conditions are not appropriate, the molten polymer will flow out from the edges during lamination, resulting in uneven thickness of the insulator 106. Furthermore, since the molten polymer will flow into the groove formation opening 212 and the via hole drilling opening 209, an inflow prevention film is required.

[0141] To prevent this, a bonding sheet can be inserted between the film-shaped insulators 106A and 106B and bonded together at a low temperature. However, inserting a bonding sheet requires a complicated processing step, 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 at least 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-shaped insulator 106B is melted and bonded to the film-shaped insulator 106A, the conductor 204, or the parallel metal film 215. The film-shaped insulator 106B is preferably thin to prevent melting from causing the polymer to flow out of the ends and into the groove formation opening 212 and the via hole drilling opening 209. The thickness of the film-shaped insulator 106B is 20 μm or more and 700 μm or less. While a thinner adhesive layer is better, a thickness of 20 μm or more and 700 μm or less is preferable in consideration of transmission characteristics.

[0144] As shown in FIG. 8 , the film-shaped insulator 106B can be two layers, insulator 106C and insulator 106D. Three or more layers are also acceptable. The film-shaped insulator 106B is made up of at least two layers, insulator 106C and insulator 106D. The melting point of the film-shaped insulator 106A and the insulator 106D that contacts and is bonded to the conductor 204 is at least 10° C. 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. The insulator 106B and the metal film 202C may be bonded together in advance, and then the insulator 106D and the film-shaped insulator 106A may be bonded together by thermocompression bonding.

[0145] The film-like insulator 106B, which is composed of two layers of insulators 106C and 106D, is formed by co-extrusion, thereby ensuring sufficient adhesion between the insulators 106C and 106D. The film-like insulator 106B, which is composed of at least the insulators 106C and 106D, may be obtained by other processing methods, such as extrusion lamination or dry lamination, instead of co-extrusion. Since the insulator 106D is melted and bonded to the film-like insulator 106A, the conductor 204, or the parallel metal film 215, it is preferably thin to prevent melting from flowing out of the edges and to prevent molten polymer from flowing into the groove formation opening 212 and the via hole drilling opening 209. The thickness of the insulator 106D is 10 μm or less, more preferably 5 μm or less.

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

[0147] When both the film-shaped insulator 106A and the film-shaped insulator 106B are polypropylene, any combination of polypropylenes may be used as long as the melting point of the film-shaped insulator 106B is at least 10°C lower than the melting point of the film-shaped insulator 106A. For example, 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, linear low-density polyethylene is suitable for the film-shaped insulator 106B. If the melting point of high-density polyethylene is, for example, 140°C, the melting point of linear low-density polyethylene can be 100°C to 120°C. Furthermore, when the film-shaped insulator 106A is linear low-density polyethylene, linear low-density polyethylene with an even lower melting point is suitable for the film-shaped insulator 106B. If the melting point of linear low-density polyethylene is, for example, 120°C, the melting point of 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 made of high-density polyethylene, the film-shaped insulator 106D is suitably made of linear low-density polyethylene. If the melting point of the high-density polyethylene is, for example, 140°C, the melting point of the linear low-density polyethylene can be 100°C to 120°C. Furthermore, when the film-shaped insulators 106A and 106C are made of linear low-density polyethylene, the insulator 106D is suitably made of linear low-density polyethylene with an even lower melting point. If 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 between 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 the insulator 106D as a layer on the surface that will be bonded to the conductor 204 and the inner layer electrode 214.

[0152] Fourth Embodiment A shielded thin flat cable 101 according to a fourth embodiment is a shielded thin flat cable 101 formed by integrating a plurality of shielded thin flat cables in the 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. 9A, multiple conductors 204 can be provided in one shielded, thin flat cable 101. Also, the shielded, thin flat cable 101 can be formed by integrating, in a planar direction, multiple shielded, thin flat cables wrapped in multiple insulators 106 isolated by metal films 202D. This is the same as the first and second embodiments except that multiple shielded, thin flat cables are integrated in a planar direction.

[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 electrodes 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 electrodes 105. The multiple shielded thin flat cables, the shielded thin flat cable on the right and the shielded thin flat cable on the left, 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] 9A shows a cross section of the conductor portion 102, and FIG. 9B shows a cross section of the terminal portion 103. This embodiment 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 of Figure 9(A) is 5 μm or more and 10,000 μm or less. Distances less than 5 μm raise concerns about crosstalk and short circuits. Distances greater than 10,000 μm are impractical because they result in a larger product and fewer wires per area. The spacing between the multiple inner electrodes 214 is determined by the packaging design and is not particularly limited, but is preferably 10 μm or more. Distances less than 10 μm raise the risk of short circuits during processing or soldering. In Figure 9(A), the multiple inner electrodes 214 are located at the same longitudinal position of the shielded thin flat cable 101. However, the positions of the multiple inner electrodes 214 may be changed to change the lengths of the multiple conductors 204. The same applies to the shielded thin flat cable on the left of Figure 9(A), and the lengths of the conductors 204 may be different from those of the shielded thin flat cable on the right.

[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 a metal film 202A and a metal film 202B are attached to both sides of a film-like insulator 106A, which is obtained by the same process as in the first embodiment.

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

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

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

[0163] 11(E) shows a process for forming a plurality of linear grooves 206 and holes 207 serving as via holes 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 using an apparatus that can form the linear grooves 206 and holes 207 serving 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 preferred because of its fast processing speed.

[0164] 11(F) shows a process for forming a metal film 202D in the plurality of linear grooves 206 in the state of FIG. 11(E) and a process for forming a metal body in the holes 207 as via holes to provide via holes 208 for drawing 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, resulting in a configuration in which the plurality of shielded thin flat cables are integrated.

[0165] 11(G) shows the process of removing a portion of the metal film 202A. This process removes a portion of the metal film 202A to form the 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 needed.

[0166] 11(H) shows a step of cutting the metal film 202C into individual pieces. The metal film 202C is cut along the linear grooves 206 to form the outline 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 pieces. The individual shielded thin flat cable 101 and the integrated shielded thin flat cable 101 may be simultaneously formed and then divided into individual pieces.

[0168] Fifth Embodiment A shielded thin flat cable 101 according to a fifth embodiment is a shielded thin flat cable 101 formed by integrating a plurality of shielded thin flat cables in the planar direction and the vertical direction. The cables may be integrated only in the vertical direction without being integrated in the horizontal direction.

[0169] In the first and second embodiments, one conductor 204 is formed in one shielded thin flat cable 101. As shown in Fig. 10A, a shielded thin flat cable 101 can be formed by integrating a plurality of shielded thin flat cables in the horizontal and vertical directions. Except for 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 upper left of Figure 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 embodiment 2. The upper right shows a shielded thin flat cable with a single conductor 204. The lower left shows a shielded thin flat cable with a single conductor 204. The lower right shows a shielded thin flat cable with multiple conductors 204. The shielded thin flat cable 101 in Figure 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 differs from the fourth embodiment in that multiple 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. If three or more shielded thin flat cables are integrated, the middle shielded thin flat cable must have a conductor electrode 105 on its end face, resulting in a complex 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 vertically integrating a plurality of shielded thin flat cables, 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 shielded thin flat cables shown in FIG. 10 are integrated in the horizontal and vertical directions.

[0176] 12A 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 laminates 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 necessary openings 209 for drilling via holes, openings 212 for forming grooves, conductors 204, inner layer electrodes 214, and conductor parallel metal films 215 are formed.

[0178] 10(A) , a plurality of openings 209 for drilling via holes and openings 212 for forming grooves 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. A plurality of openings 209 for drilling via holes and openings 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] 12(C) shows the process of sandwiching a metal film 202E between two film-like insulators 106, and laminating a laminate constituting the upper part of the shielded thin flat cable 101 onto the upper film-like insulator 106 and a laminate constituting the lower part of the shielded thin flat cable 101 below 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 that encases a conductor 204, an inner electrode 214, and a conductor-parallel metal film 215, a metal film 202E, the insulator 106 that 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 in the insulator 106 above and below the metal film 202E, along both side surfaces of the conductor 204 and the inner-layer electrode 214, which are required to be parallel to the conductor 204. The linear grooves 206 are formed by removing linear portions of the insulator 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] 12(F) shows a process for forming a metal film 202D in the plurality of linear grooves 206 shown in FIG. 12(E) and a process for forming a metal body in the holes 207 serving as a plurality of via holes to provide via holes 208 for providing 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. The wall surface 205 of the linear groove 206 formed between one conductor 204 and a 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 shown at the top of FIG. 10(A) that are separated by the metal film 202D and the metal film 202E. Furthermore, by metal plating the wall surfaces 205 of the linear grooves 206 formed between one conductor 204 and three conductors 204 to form metal films 202D, the two shielded thin flat cables at the bottom of Fig. 10(A) are formed, which are separated by metal films 202D and 202E. A configuration can be formed in which multiple shielded thin flat cables are integrated in the horizontal and vertical directions.

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

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

[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 pieces. The individual shielded thin flat cable 101 and the integrated shielded thin flat cable 101 may be simultaneously formed and then divided into individual pieces.

[0186] 1B, 1B-1, 1B-2, and 1B-3, conductor electrodes 105, which are terminals for drawing electrical continuity from conductors 204 and transmitting and receiving signals, are typically provided on the flat surface of a shielded thin flat cable 101. The shielded thin flat cable 101 according to the sixth embodiment 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 the end surface of a shielded, thin, flat cable 101. FIG. 13(A) shows a left side view, FIG. 13(B) shows a plan view, FIG. 13(C) shows a right side view, and FIG. 13(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 above and below 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 the conductor 204 provided inside the shielded, thin, flat cable 101. In FIG. 13, the conductor electrode 105 is provided on the longitudinal end surface of the shielded, thin, flat cable 101, but it may also be provided on the lateral end surface.

[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 made of the same material and have the same shape as those in embodiments 1 and 2.

[0189] 14 shows the manufacturing process of a shielded thin flat cable 101 provided with a conductor electrode 105 on its end surface. 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 surface of the shielded thin flat cable 101. However, since the conductor electrode 105 on the end surface is continuous with the conductor 204, there is no need to provide a via hole 208.

[0190] In Fig. 14A, metal films 202A and 202B are bonded to both sides of film-like insulator 106A. In Fig. 14B, a circuit formation process is performed on metal film 202B to provide conductor 204 and groove-forming opening 212. Conductor 204 is provided so as to be continuously drawn out from a location that will become the end face of 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 longitudinal end face of the shielded thin flat cable 101. The conductor 204 may also 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 be wider than the width of the conductor 204 along the end face at the end face. By widening the width, it is possible to ensure a connection with the metal plating 202D provided on the wall surface 205 of the end face.

[0192] In Fig. 14C, 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. 14D shows the resulting laminate.

[0193] 14(E), a linear groove 206 is formed by removing the insulator 106 from the groove forming opening 212 using laser processing. A wall surface 205 of the linear groove 206 is provided in contact with the end of the conductor 204 at a location that will become the end face of the shielded thin flat cable 101. This is to connect 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. 14F, a metal film 202D is formed on the wall surface 205 of the linear groove 206 by metal plating, and the metal film 202D provided on the wall surface 205 of the linear groove 206 and the end of the 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 portions of the metal films 202A, 202C, and 202D shown in Fig. 14(F) to form gaps 218. In the circuit formation process, the metal film 202 around the portion that will become the conductor electrode 105 is removed 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 the end surface of the shielded thin flat cable 101, continuing from the gaps 218 provided on the flat surface.

[0196] 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 conductor electrodes 105 provided on the end surface. FIG. 15(A) is a plan view corresponding to the process shown in FIG. 14(B-1). In the circuit formation process, two conductors 204 are formed from a 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 that they extend to different longitudinal end faces 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 along the end face at the end face. By making the width wider, connection with the metal plating 202D provided on the wall surface 205 of the end face can be ensured.

[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, it will not be possible to reliably connect it to the metal plating on the end wall surface 205, and it will be prone to breakage. If it exceeds 100 μm, the processing precision of the width of the conductor 204 will be significantly reduced.

[0199] FIG. 15(B) shows a shielded thin flat cable 101 in which conductor electrodes 105 are provided on both end surfaces. FIG. 15(B) shows a case in which a gap 218 is formed by a circuit formation process. The end of the gap 218 can be made straight. Removing the metal film 202D formed on the wall surface 205 of the linear groove 206 by the circuit formation process would complicate the resist film curing process because the surface is not flat. To form circuits on the end surfaces, the etching resist is not a dry film, but a liquid etching resist, which is applied to the end surfaces by electrostatic coating or roll coating. Furthermore, exposure is also performed to the end surfaces, using a method such as laser light. Because circuit formation on the end surfaces differs from conventional printed wiring board processing methods, conditions must be managed.

[0200] The step of removing a portion 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 can be performed using a drill bit or a router bit. Figure 15(C) shows the metal film 202D formed on the wall surface 205 removed by cutting, with the removed end surface being curved.

[0201] By providing the conductor electrode 105 on the end surface, the conductor 204 is drawn out to the conductor electrode 105 using the end surface, so there is no need to form an opening 209 for drilling a via hole. In addition, the metal film 202 above and below the end surface and 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 devices that require high-density mounting, devices that use high-frequency and high-speed signals, devices that require EMI countermeasures, devices that require chemical resistance, and more specifically, smartphones, IoT devices, communication base station peripheral devices, automobile-related devices such as ADAS, lithium-ion battery peripheral devices, and the like.

[0203] 101: Shielded thin flat cable 102: Conductor portion 103: Terminal portion 105: Conductor electrode 106: Insulator 108: Through hole 202: Metal film 204: Conductor 205: Wall surface 206: Linear groove 207: Hole as via hole 208: Via hole 209: Opening for drilling via hole 211: Solder mask 212: Opening for forming groove 214: Inner layer electrode 215: Conductor parallel metal film 218: Gap

Claims

1. A shielded thin flat cable having a conductor made of metal, an insulator sandwiching the conductor and encasing the conductor except for the conductor electrodes that are conductive to the conductor and exposed on the surface, and a continuous metal film on the surface of the insulator except for the periphery of the conductor electrodes, wherein the melting point of a second film insulator bonded to the conductor, the inner layer electrodes, and the first film insulator on the surface of the first film insulator on which the conductor and inner layer electrodes that are conductive to the conductor electrodes are formed is 10°C or more lower than the melting point of the first film insulator, and a third film insulator having a melting point equal to or higher than the melting point of the first film insulator on the surface of the second film insulator opposite the surface that sandwiches the conductor.

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

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

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

5. A shielded thin flat cable according to claim 1, 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. A shielded thin flat cable according to claim 1, characterized in that when the first film-like insulator is high-density polyethylene, the second film-like insulator is linear low-density polyethylene.

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

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

9. A method for manufacturing a shielded thin flat cable, comprising: laminating metal films on both sides of a first film-like insulator; forming a conductor and an inner layer electrode connected to an electrode continuous with the conductor by performing a circuit formation process on the metal film on one side of the first film-like insulator; forming an opening for drilling a via hole by performing a circuit formation process on the metal film on the other side; laminating a second film-like insulator having a melting point 10°C or more lower than the melting point of the first film-like insulator on the conductor and inner layer electrode formed on one side of the first film-like insulator, and a metal film on the second film-like insulator; removing the metal film, the first film-like insulator, and the second film-like insulator on the other side of the first film-like insulator, or breaking the metal film on the metal film, the first film-like insulator, the second film-like insulator, and the second film-like insulator on the other side of the first film-like 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, characterized in that a metal film is formed on the end surface.

10. A method for manufacturing a shielded thin flat cable as described in claim 9, characterized in 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 second film-like insulator.

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

12. A method for manufacturing a shielded thin flat cable according to claim 9 or 10, characterized in that the second film-like insulator contains a copolymer of an alkene and a monomer having a carboxyl group.

13. A method for manufacturing a shielded thin flat cable according to claim 9 or 10, characterized in that the first film-like insulator contains a copolymer of an alkene and a monomer having a carboxyl group.

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

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

16. A method for manufacturing a shielded thin flat cable as defined in claim 9, comprising: forming a circuit on the metal film on one side of the first film-like insulator to form an inner layer electrode that is conductive to a conductor and an electrode continuous with the conductor; forming a circuit on the metal film on the other side to form an opening for drilling a via hole; bonding a second film-like insulator, a metal film, another second film-like insulator, and the conductor of another shielded thin flat cable intermediate product to the other second film-like insulator side; irradiating the insulators on the top and bottom of a shielded thin flat cable in which a plurality of shielded thin flat cable intermediate products are integrated vertically with laser light to remove the insulator down to the metal film of the other shielded thin flat cable; and forming the metal film on the wall surface of a groove formed by removing the insulator.

17. A method for manufacturing a shielded thin flat cable as defined in claim 9, characterized in that a circuit formation process is carried out on the metal film on one side of the first film-like insulator to form an inner layer electrode that is conductive to a conductor and an electrode continuous with the conductor, a circuit formation process is carried out on the metal film on the other side to form openings for via holes, a second film-like insulator, a metal film, another second film-like insulator, and the conductor of another shielded thin flat cable intermediate product are bonded to the other second film-like insulator side of the first film-like insulator of a shielded thin flat cable intermediate product, and the upper and lower metal films and insulators are broken 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 the metal film is formed on the end face of the formed shielded thin flat cable.

18. A method for manufacturing a shielded thin flat cable according to claim 16 or 17, characterized in that the metal film between a plurality of integrated shielded thin flat cables is formed continuously.

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