JP2008300343A - Cable for signal transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin cable for signal transmission high in flexibility, and capable of suppressing increase of transmission loss in a transmission frequency band of a high-frequency signal over 2 GHz. <P>SOLUTION: This cable for signal transmission is composed of: a flat signal conductor 1; flat grounding conductors 2 and 3 arranged on both sides of the signal conductor 1 and on the same plane as that of the signal conductor 1; electric insulation layers 4 and 5 covering the signal conductor 1 and the grounding conductors 2 and 3 to catch them from the upper and lower sides; a metal shielding layer 15 formed by collectively surrounding the signal conductor 1, the grounding conductors 2 and 3 and the electric insulation layers 4 and 5; and a protective covering layer 16 covering the metal shielding layer 15. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is thin, flexible, and has excellent electrical characteristics. Particularly suitable for high-frequency signal transmission in electronic devices such as mobile phones, PCs (Personal Computers), and PDAs (Personal Digital Assistance). The present invention relates to a cable for signal transmission.

  Conventionally, in an electronic device such as a mobile phone, a PC, and a PDA, a coaxial cable has been used as an antenna feeding line from an attached antenna to a main board.

  In recent years, mobile phones and notebook PCs have been widely folded, and have been reduced in size and thickness. Flexibility for inserting a hinge part to be folded in the antenna feed line. Therefore, it is required to reduce the thickness for wiring in a narrow space.

  However, since the coaxial cable is round and has a large outer diameter, it cannot satisfy the above-described requirements as an antenna feed line.

In order to improve such a drawback of the coaxial cable, a signal transmission cable as shown in FIG. 7 has been proposed (Patent Document 1).
JP 2006-202714 A (FIG. 2, paragraphs 0016 to 0032)

  The signal transmission cable includes a flat signal conductor 101 made of a metal foil such as a copper foil, a flat signal conductor 101 arranged on both sides of the signal conductor 101 and on the same plane as the signal conductor 101, and made of a metal foil such as a copper foil. -Shaped ground conductors 102 and 103, electrical insulating layers 104 and 105 made of an electrically insulating thin film covering the signal conductor 101 and the ground conductors 102 and 103 from above and below, and covering the electrical insulating layers 104 and 105 from above and below The flat shielding layers 106 and 107 made of a metal foil such as copper foil and the protective coating layers 108 and 109 made of an electrically insulating thin film covering the shielding layers 106 and 107 are formed.

  When the signal conductor 101 and the ground conductors 102 and 103 are copper conductors, a nickel base plating and a gold plating layer 110, 111, 112 are formed on these surfaces to improve solderability, and the connector with the connector at the terminal The connectivity is good.

  In addition, conductive adhesive layers 113 and 114 are provided on the inner side surfaces of the shielding layers 106 and 107, respectively. The conductive adhesive layer 113 and the conductive adhesive layer 114 are arranged so as to face each other, and heat sealing or the like is performed. The signal conductor 101 is electrically shielded by the shielding layers 106 and 107 by bonding the conductive adhesive layer 113 and the conductive adhesive layer 114 by a method.

  When the signal transmission cable described above is used as an antenna feed line for an electronic device such as a mobile phone, a PC, or a PDA, a high-frequency signal exceeding 2 GHz is transmitted to the signal transmission cable.

  In such high-frequency signal transmission exceeding 2 GHz, a current is concentrated on the surface layer of several microns due to a so-called skin effect, and the conductivity of the signal conductor 101 and the ground conductors 102 and 103 is relatively low. Since current concentrates on the plating layers 110, 111, and 112 made of nickel (which has a relatively large electrical resistance), transmission loss occurs, which is a major factor in increasing the transmission loss of the signal transmission cable.

  In addition, regarding the shielding layers 106 and 107, current is concentrated on the conductive adhesive layers 113 and 114 having relatively low conductivity (relatively high electrical resistance), and transmission loss is generated. This is a major factor in increasing transmission loss.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a signal transmission cable that is thin and flexible and that can suppress an increase in transmission loss in a transmission frequency band of a high frequency signal exceeding 2 GHz.

  In order to achieve the object, the invention of claim 1 includes a flat signal conductor, flat ground conductors formed on both sides of the signal conductor and substantially on the same plane as the signal conductor, and the signal conductor. And a signal transmission cable comprising an electric insulation layer formed to cover the ground conductor and a metal shielding layer formed to cover the electric insulation layer, wherein the signal conductor and the ground conductor are highly conductive. Characterized by a signal transmission cable made of a conductive metal and formed without forming a metal layer having a conductivity lower than that of the good conductive metal on the surface of the signal conductor and the ground conductor made of the good conductive metal Yes.

  According to a second aspect of the present invention, there is provided a flat signal conductor, a flat ground conductor formed on both sides of the signal conductor and substantially on the same plane as the signal conductor, the signal conductor and the ground conductor. A signal transmission cable comprising an electrically insulating layer formed to cover and a metal shielding layer formed to cover the electrical insulating layer, wherein the metal shielding layer is a single metal layer in the cable cross section And a signal transmission cable configured to collectively surround the signal conductor, the ground conductor, and the electrical insulating layer.

  In the first aspect of the invention, since the metal layer having a conductivity lower than that of the highly conductive metal is not formed on the surface of the signal conductor and the ground conductor made of the highly conductive metal, the high frequency exceeding 2 GHz is used. An increase in transmission loss due to the skin effect in signal transmission can be minimized.

  In the second aspect of the invention, the metal shielding layer is made of a single metal layer in the cable cross section and surrounds the signal conductor, the ground conductor and the electrical insulating layer at the same time. It is not necessary to form the conductive adhesive layers 113 and 114 on the inner side surfaces of the shielding layers 106 and 107 (which has a relatively large electrical resistance), and transmission loss can be increased due to the skin effect in the transmission of high-frequency signals exceeding 2 GHz. It can be kept as small as possible.

  As described above, according to the first and second aspects of the invention, it is thin and flexible, and for signal transmission that can suppress an increase in transmission loss in a transmission frequency band of a high frequency signal exceeding 2 GHz. A cable can be realized.

  The best mode of a signal transmission cable according to the present invention will be described below with reference to the accompanying drawings.

  As shown in FIG. 1, the signal transmission cable according to the first embodiment includes a flat signal conductor 1 and flat ground conductors 2 arranged on both sides of the signal conductor 1 and on the same plane as the signal conductor 1. , 3, electric insulating layers 4 and 5 made of an electric insulating thin film covering the signal conductor 1 and the ground conductors 2 and 3 from above and below, and a flat metal covering the electric insulating layers 4 and 5 from above and below The shielding layers 6 and 7 and the protective coating layers 8 and 9 that cover the metal shielding layers 6 and 7 so as to be sandwiched from above and below are configured.

  Conductive adhesive layers 13 and 14 are provided on the inner side surfaces of the metal shielding layers 6 and 7, respectively. The conductive adhesive layer 13 and the conductive adhesive layer 14 are disposed so as to face each other, and a method such as heat fusion is performed. By adhering the conductive adhesive layer 13 and the conductive adhesive layer 14 to each other, the signal conductor 1 is electrically shielded by the metal shielding layers 6 and 7.

The signal conductor 1 and the ground conductors 2 and 3 are both formed of a highly conductive metal, and specifically, copper (conductivity: 5.76 × 10) which is commonly used as a highly conductive metal in the industry. ⁷ Siemens / m) processed into a foil shape is preferably laminated on the electrical insulating layers 4 and 5, or copper is deposited or plated on the electrical insulating layers 4 and 5, except for copper. Examples of the metal include aluminum (conductivity: 3.96 × 10 ⁷ Siemens / m).

  The metal shielding layers 6 and 7 are preferably formed of a highly conductive metal such as copper or aluminum in the same manner as the signal conductor 1 and the ground conductors 2 and 3, and these metals are processed into a foil shape. It is preferable that the protective coating layers 8 and 9 are laminated or formed by depositing or coating the protective coating layers 8 and 9 with these metals.

  The electric insulating layers 4 and 5 are preferably formed of an electric insulating thin film made of plastic. Examples of such plastic include polyimide, polyethylene terephthalate (PET), liquid crystal polymer (LCP), and polytetrafluoroethylene (PTFE). Etc.

  The protective coating layers 8 and 9 are preferably formed of a plastic thin film such as polyethylene terephthalate (PET), polyethylene, or polyvinyl chloride.

The signal transmission cable of the first embodiment is a layer having a low conductivity such as a plating layer made of nickel (conductivity: 1.45 × 10 ⁷ Siemens / m) on the surface of the signal conductor 1 and the ground conductors 2 and 3. The difference in transmission loss from the case where the nickel plating layer is formed, that is, the difference in transmission loss due to the presence or absence of the nickel plating layer [(with nickel plating layer) − (without nickel plating layer)] = − It was 2.1 dB.

  Note that the transmission loss is a signal transmission cable using a copper foil having a thickness of 18 μm as the signal conductor 1 and the ground conductors 2 and 3 and a liquid crystal polymer (LCP) thin film having a thickness of 150 μm as the electrical insulating layers 4 and 5 (long Is a result of measurement at a frequency of 2 GHz.

  As shown in FIG. 2, the signal transmission cable according to the second embodiment includes a flat signal conductor 1 and flat ground conductors 2 arranged on both sides of the signal conductor 1 and on the same plane as the signal conductor 1. , 3, electric insulating layers 4 and 5 made of an electric insulating thin film covering the signal conductor 1 and the ground conductors 2 and 3 so as to be sandwiched from above and below, and the signal conductor 1, the ground conductors 2 and 3, and the electric insulating layers 4 and 5 The protective covering layer 16 formed so as to surround the package and the metal shielding layer 15 integrated therewith are constituted.

On the surfaces of the signal conductor 1 and the ground conductors 2 and 3, nickel base plating and gold plating layers 10, 11, and 12 are formed (gold conductivity: 4.1 × 10 ⁷ Siemens / m).

  The metal shielding layer 15 is formed of a single metal layer (copper foil) in the cross section of the cable, and the signal conductor 1, the ground conductors 2, 3 and the electric insulation are formed by overlapping the end portions 15a, 15b of the metal layer. Layers 4 and 5 are enclosed.

  The other configuration of the signal transmission cable of the second embodiment is the same as that of the first embodiment.

  In the signal transmission cable of the second embodiment, the conductive adhesive layer is not provided inside the metal shielding layer 15, and the difference in transmission loss from the case where the conductive adhesive layer is provided, that is, the conductive adhesive layer. Difference in transmission loss due to presence or absence of [(with conductive adhesive layer) − (without conductive adhesive layer)] = − 0.6 dB.

  Note that the transmission loss is a signal transmission cable using a copper foil having a thickness of 18 μm as the signal conductor 1 and the ground conductors 2 and 3 and a liquid crystal polymer (LCP) thin film having a thickness of 150 μm as the electrical insulating layers 4 and 5 (long Is a result of measurement at a frequency of 2 GHz.

  As shown in FIG. 3, the signal transmission cable according to the third embodiment includes a flat signal conductor 1 and flat ground conductors 2 arranged on both sides of the signal conductor 1 and on the same plane as the signal conductor 1. , 3, electric insulating layers 4 and 5 made of an electric insulating thin film covering the signal conductor 1 and the ground conductors 2 and 3 so as to be sandwiched from above and below, and the signal conductor 1, the ground conductors 2 and 3, and the electric insulating layers 4 and 5 The protective covering layer 16 formed so as to surround the package and the metal shielding layer 15 integrated therewith are constituted.

  A high electric resistance layer such as a nickel plating layer is not formed on the surfaces of the signal conductor 1 and the ground conductors 2 and 3, and the metal shielding layer 15 is a single metal layer (copper foil) in the cable cross section. The signal conductor 1, the ground conductors 2 and 3, and the electrical insulating layers 4 and 5 are collectively surrounded by overlapping the end portions 15a and 15b of the metal layer.

  The other configuration of the signal transmission cable of the third embodiment is the same as that of the first embodiment.

  In the signal transmission cable according to the third embodiment, a high electrical resistance layer such as a nickel plating layer is not formed on the surfaces of the signal conductor 1 and the ground conductors 2 and 3, and a conductive adhesive layer is formed inside the metal shielding layer 15. The increase in transmission loss in the transmission frequency band of high-frequency signals exceeding 2 GHz can be more effectively suppressed.

  FIG. 5 is an explanatory diagram of a method for manufacturing a signal transmission cable according to the third embodiment. First, as shown in FIG. The copper-clad laminate 51 is produced, and then the signal conductor 1 and the ground conductors 2 and 3 are formed by etching the copper foil 50 as shown in FIG.

  Next, as shown in FIG. 5 (c), an electrical insulating thin film (electrical insulating layer) 4 is laminated on the signal conductor 1 and the ground conductors 2 and 3, and as shown in FIG. 5 (d), A metal shielding layer 15 integrated with a protective multi-layer (not shown) is provided around the electrically insulating thin films (electrically insulating layers) 4 and 5 so that the end portions 15a and 15b are overlapped, and the signal conductor 1 and the ground conductor 2 , 3 and the electric insulating layers 4 and 5 are collectively enclosed to manufacture a signal transmission cable.

  As shown in FIG. 4, the signal transmission cable of the fourth embodiment includes a flat signal conductor 1 and flat ground conductors 2 arranged on both sides of the signal conductor 1 and on the same plane as the signal conductor 1. , 3, and a metal shielding layer 15 integrated with a protective covering layer 16 formed so as to surround the signal conductor 1, the ground conductors 2, 3 and the electrical insulating layers 4, 5 together.

  A high electric resistance layer such as a nickel plating layer is not formed on the surfaces of the signal conductor 1 and the ground conductors 2 and 3, and the metal shielding layer 15 is a single metal layer (copper foil) in the cable cross section. The signal conductor 1, the ground conductors 2 and 3, and the electrical insulating layers 4 and 5 are collectively surrounded by overlapping the end portions 15a and 15b of the metal layer.

  The electrical insulating layer 44 provided on the signal conductor 1 and the ground conductors 2 and 3 is formed so as to expose both side portions of the ground conductors 2 and 3. And the metal shielding layer 15 are brought into contact with each other over the entire length of the cable and a good electrical conduction state is ensured between the two, so that an excellent shielding effect is exhibited.

  Other configurations of the signal transmission cable of the fourth embodiment are the same as those of the first embodiment.

  In the signal transmission cable according to the fourth embodiment, a high electrical resistance layer such as a nickel plating layer is not formed on the surfaces of the signal conductor 1 and the ground conductors 2 and 3, and a conductive adhesive layer is formed inside the metal shielding layer 15. The increase in transmission loss in the transmission frequency band of high-frequency signals exceeding 2 GHz can be more effectively suppressed.

  FIG. 6 is an explanatory diagram of a method for manufacturing a signal transmission cable according to the fourth embodiment. First, as shown in FIG. The copper clad laminate 51 is prepared, and then the signal conductor 1 and the ground conductors 2 and 3 are formed by etching the copper foil 50 as shown in FIG.

  Next, as shown in FIG. 6 (c), an electrical insulating thin film (electrical insulating layer) 44 is laminated on the signal conductor 1 and the ground conductors 2 and 3, and as shown in FIG. 6 (d), A metal shielding layer 15 integrated with a protective multi-layer (not shown) is provided around the electrical insulating thin films (electrical insulating layers) 44 and 5 so that the end portions 15a and 15b are overlapped, and the signal conductor 1 and the ground conductor 2 , 3 and the electric insulating layers 4 and 5 are collectively enclosed to manufacture a signal transmission cable.

  The metal shielding layer 15 is formed so as to be in contact with the exposed portions on both sides of the ground conductors 2 and 3.

  Although the best embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes that do not depart from the gist of the present invention are possible. Are included in the present invention.

  It is a cross-sectional view of Example 1 which is the best mode of the signal transmission cable of the present invention.   It is a cross-sectional view of Example 2 which is the best mode of the signal transmission cable of the present invention.   It is a cross-sectional view of Example 3 which is the best mode of the signal transmission cable of the present invention.   It is a cross-sectional view of Example 4 which is the best mode of the signal transmission cable of the present invention.   6 is an explanatory diagram of a method for manufacturing a signal transmission cable according to Embodiment 3. FIG.   10 is an explanatory diagram of a method for manufacturing a signal transmission cable according to Embodiment 4. FIG.   It is a cross-sectional view of a conventional signal transmission cable.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Signal conductor 2, 3 Ground conductor 4, 5 Electrical insulation layer 6, 7 Metal shielding layer 15 Metal shielding layer 44 Electrical insulation layer

Claims (2)

  A flat signal conductor, a flat ground conductor formed on both sides of the signal conductor and substantially on the same plane as the signal conductor, and an electric insulation layer formed to cover the signal conductor and the ground conductor The signal conductor and the grounding conductor are made of a highly conductive metal, and the signal conductor is made of the highly conductive metal. And a signal transmission cable comprising a surface of the ground conductor without forming a metal layer having a conductivity lower than that of the highly conductive metal.   A flat signal conductor, a flat ground conductor formed on both sides of the signal conductor and substantially on the same plane as the signal conductor, and an electric insulation layer formed to cover the signal conductor and the ground conductor And a metal transmission layer comprising a metal shielding layer formed to cover the electrical insulation layer, wherein the metal shielding layer is a single metal layer in a cable cross section, and the signal conductor, the ground A signal transmission cable comprising a conductor and the electric insulation layer surrounded together.

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