JP2006049185A - Flat cable and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat cable with high reliability in which the conductor portion of the cable has flexibility and is prevented from the occurrence of migration and the conductor portion of a connecting terminal is applied with gold plating effectively, and its manufacturing method. <P>SOLUTION: This flat cable has plurality of flat copper conductors 7 applied with tin plating 7b arranged in parallel and covered with an insulating film 8, and a connecting terminal 3 for being connected to an electric connector 6 formed at least at one end. The flat copper conductor 7 of the connecting terminal 3 to become a contact conductor 4 is removed in tin plating 7b and gold plating is applied to the portion removed of tin plating by nickel plating. Furthermore, the connecting terminal 3 is exposed from the insulating film 8 on both sides of the flat copper conductor 7 and reinforced by jointing a reinforcement plate 5 on one side, or exposed from the insulating film 8 on one side of the flat copper conductor 7 and reinforced by jointing the reinforcement plate 5 on the insulating film face on the side not exposed in the flat copper conductor 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a flat cable in which a plurality of flat copper conductors are arranged in parallel and covered with an insulating film, and a connection terminal portion is formed on at least one end, and a method for manufacturing the same.

  As communication devices and electronic devices become smaller and lighter, electronic components and wiring components mounted on these devices are becoming smaller. In particular, wiring members for electrical wiring are required to be mounted with high density and high reliability within a limited space. As such a wiring member, there is a flexible flat cable in which a plurality of flat copper conductors are arranged in parallel and covered with an insulating film, and connection terminal portions for electrical connection are formed at both ends.

  This type of flat cable uses flat copper conductors with excellent flexibility and conductivity, but when used with bare copper, migration tends to occur at high temperatures and high humidity, and insulation between adjacent conductors Reduces resistance and easily causes electrical short circuit. Bare copper is easily oxidized, and if the flat copper conductor is oxidized before being covered with the insulating film, the adhesiveness with the insulating film is lowered. In order to eliminate such problems and improve corrosion resistance and solderability, a flat copper conductor surface with tin plating is used (for example, see Patent Document 1).

  However, although tin plating is usually formed by electroplating, it is known that acicular crystals (hereinafter referred to as whiskers) are generated on the surface of this electrotin plating. This is because, when tin plating is applied to a copper-based metal material, copper atoms diffuse into the tin plating film to form a copper-tin intermetallic compound. Since this intermetallic compound has a crystal structure different from that of tin and can be distorted in the lattice spacing, compressive stress is generated in the tin plating film. Since this compressive stress is a driving force for whisker growth, it is said that whisker is likely to occur when tin plating is applied to a copper-based material.

  Although it is well known that whisker generation is suppressed by adding lead to tin plating, lead compounds are toxic and are not preferable due to environmental problems. A wiring member is desired. It is possible to suppress the generation of whiskers to some extent by performing lead-free tin plating on the electrical connection portion and heat-treating the tin plating (see, for example, Patent Document 2). However, when used for connection with an insertion / extraction type electrical connector, whiskers are likely to occur at the contact portion, causing a short circuit between the electrodes. This is considered to be caused by the external stress applied to the surface of the tin plating by the contact piece of the electrical connector.

Further, it is known that a flat cable using a flat copper conductor is subjected to nickel plating instead of tin plating, and gold plating is applied only to the connection terminal portion from the top to improve high reliability (for example, patents) Reference 3). The reason why nickel plating is applied to the entire flat copper conductor is that the gold plating directly on the copper conductor or tin plating copper conductor cannot withstand long-term use. It is complicated and impractical.
Japanese Unexamined Patent Publication No. 7-99012 JP 2001-73186 A JP-A-8-293214

  As disclosed in Patent Document 3, when nickel plating is applied to the entire copper conductor, nickel is harder than copper, so that flexibility as a flat cable is reduced and cable characteristics are deteriorated. Nickel plating also has poor adhesion to insulators and covering tapes, resulting in poor adhesion to flat copper conductors. Furthermore, nickel is easily oxidized and an oxide film is formed on the plating surface, making gold plating difficult. There's a problem. From this point, it is more suitable to use a tin-plated flat copper conductor as a flat cable, but from the point of whisker generation at the connection terminal part and high reliability, at least the connection terminal part is gold-plated. It is requested that it is given.

However, when gold plating is applied directly to a tin-plated flat copper conductor, electrolytic corrosion due to contact between different metals of gold plating and tin plating occurs. Therefore, it is conceivable to perform gold plating through nickel plating that is usually used as a base metal for gold plating. However, when nickel plating is applied on tin plating, there is a problem that cracks occur between the plating layers.
The present invention has been made in view of the above-described circumstances. The conductor portion of the cable portion is flexible so that no migration occurs, and the conductor portion of the connection terminal portion is effectively plated with gold. It is an object to provide a highly reliable flat cable and a manufacturing method thereof.

  A flat cable according to the present invention is a flat cable in which a plurality of flat copper conductors plated with tin are arranged in parallel and covered with an insulating film, and a connection terminal portion connected to an electrical connector is formed on at least one end portion. is there. The flat copper conductor portion used as the contact conductor of the connection terminal portion is removed from the tin plating, and the portion from which the tin plating is removed is subjected to gold plating via nickel plating. Further, the connection terminal portion is reinforced by exposing both sides of the flat copper conductor from the insulating film and joining one side to the reinforcing plate, or by exposing one side of the flat copper conductor from the insulating film. A reinforcing plate is joined to the insulating film surface of the copper conductor that is not exposed to reinforce.

  The flat cable manufacturing method according to the present invention includes a plurality of tin-plated flat copper conductors arranged in parallel and covered with an insulating film, and at least one end thereof has a connection terminal portion connected to an electrical connector. It is a manufacturing method of the flat cable to form. The tin plating of the flat copper conductor portion, which is the contact conductor of the connection terminal portion, is removed, nickel plating is applied to the portion from which the tin plating has been removed, and gold plating is subsequently performed. The plating bath used for gold plating has a pH of 9 or less.

  According to the present invention, since the conventional tin-plated flat copper conductor is used as it is, no short circuit between the conductors due to migration occurs, and the flexibility of the flat cable and the adhesive force with the insulating tape can be ensured as usual. Since the nickel plating as the base of the gold plating is applied to the surface of the copper conductor from which the tin plating is removed, the portion that becomes the contact conductor of the connection terminal portion does not cause a crack between the tin plating and the nickel plating, It can be set as the connection terminal part gold-plated in a favorable state. As a result, whisker is not generated in connection with the insertion / extraction type connector, and it can be electrically excellent in long-term reliability.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 (A) is a diagram for explaining the outline of a flat cable according to the present invention, FIG. 1 (B) is a diagram showing a cross section of the cable part aa, and FIG. 1 (C) is a cross section of part b of the connection terminal part. FIG. In the figure, 1 is a flat cable, 2 is a cable part, 3 is a connection terminal part, 4 is a contact conductor, 5 is a reinforcing plate, 6 is an electrical connector, 6a is a connector contact piece, 7 is a flat copper conductor, and 7a is copper. Conductor, 7b is tin-plated, 8 is an insulating film, 8a is a film material, and 8b is an adhesive layer.

  As shown in FIG. 1A, a flat cable 1 according to the present invention is attached to and detached from a pluggable electrical connector 6 or the like at both ends of a cable portion 2 in which a plurality of flat copper conductors are arranged in parallel and covered with an insulating film. A connection terminal unit 3 that can be connected is provided. The connection terminal portion 3 is formed by gold plating the flat copper conductor portion exposed from the cable end portion to form a contact conductor 4, and a reinforcing plate 5 is joined to the opposite side.

  As shown in FIG. 1 (B), the cable portion 2 is formed by arranging flat copper conductors 7 formed by applying tin plating 7b on the surface of a copper conductor 7a having a flat cross section in a parallel row, and insulating film from both sides. 8 is formed by being bonded and integrated. Hereinafter, the state in which the tin plating 7b is applied to the copper conductor 7a is referred to as a flat copper conductor 7. As the flat copper conductor 7, for example, a round conductor is subjected to tin plating by electroplating, and then stretched and rolled to form a flat shape.

  The insulating film 8 sandwiches the flat copper conductors 7 from both sides and presses or melts the adhesive layer 8b to bond and integrate them, thereby electrically insulating the flat copper conductors 7 arranged at high density. As the insulating film 8, for example, a polyester resin film material 8a and a thermoplastic resin or thermosetting resin adhesive layer 8b formed on the inner surface of the film and laminated and integrated are used. Hereinafter, the film material 8a and the adhesive layer 8b are referred to as an insulating film 8. The reinforcing plate 5 can also be a polyester resin film material. In this case, for example, a film about 5 times thicker than the insulating film 8 is used.

  As shown in FIG. 1 (C), at least one insulating film 8 on one side of the flat copper conductor 7 is removed from the connection terminal portion 3 at the end of the cable portion 2 to expose the conductor surface. As will be described later, the exposed conductor surface is formed by removing the tin plating applied to the surface of the copper conductor, and the contact conductor 4 is gold-plated via nickel plating on the copper conductor surface from which the tin plating has been removed. . On the opposite side of the contact conductor 4, the reinforcing plate 5 is joined to form a rigid substrate, and the shape is detachable from the insertion / removal type electrical connector 6. The electrical connector 6 is, for example, a jack type or a female type into which an edge of a printed circuit board is inserted, and the connector contact piece 6a is pressed against the surface of the contact conductor 4 to form an electrical connection. The

  FIG. 2 is a diagram illustrating a configuration example of a connection terminal portion in which one side of the flat copper conductor 7 is directly joined to the reinforcing plate 5. 2A is a diagram showing the entire cable, and FIG. 2B is a diagram showing a cross section of the connection terminal portion taken along the line cc. In the figure, reference numeral 3a denotes a connection terminal portion, 5a denotes a reinforcing plate, 9 denotes nickel plating, 10 denotes gold plating, and the other reference numerals are the same as those used in FIG.

  In the embodiment shown in FIG. 2A, with respect to the connection terminal portion 3a at both ends of the cable portion 2, the insulating film 8 covering the end portion of the flat copper conductor 7 is peeled off to expose both surfaces of the flat copper conductor 7. Let One side of the flat copper conductor 7 exposed on both sides is directly joined to a reinforcing plate 5a made of an insulating material to fix the arrangement of the flat copper conductors 7 and is rigid so that it can be attached to and removed from an insertion / removal type electrical connector. The connection terminal unit. Note that it is only necessary that at least one end portion of the cable portion 2 be a connection terminal portion that can be attached to and detached from the electrical connector, and the other end portion is, for example, a connection terminal portion that can be connected by soldering (no gold plating is required) ).

  Next, as shown in FIG. 2B, after the flat copper conductor 7 exposed on the reinforcing plate 5a is adhered and fixed, the tin plating 7b on the exposed surface side is removed by etching or the like. The tin plating 7b on the side bonded to the reinforcing plate 5a remains without being removed. However, the tin plating on both sides can be removed by performing the tin plating removal process before bonding the reinforcing plate 5a. The copper conductor 7a after the tin plating 7b is removed is subjected to gold plating 10 via nickel plating 9. Thereby, the cable part 2 is formed by covering a plurality of flat copper conductors 7 plated with tin with the insulating film 8, and the connection terminal part 3 a is connected to the copper conductor 7 a via the nickel plating 9. A flat cable having a contact conductor 4 provided with gold plating 10 is obtained.

  FIG. 3 is a diagram illustrating a configuration example of a connection terminal portion in which a reinforcing plate is bonded to an insulating film surface of a flat copper conductor that is not exposed. FIG. 3A is a diagram illustrating the entire cable, and FIG. 3B is a diagram illustrating a cross section of the connection terminal portion taken along line dd. In the figure, 3b represents a connection terminal portion, 5b represents a reinforcing plate, and the other reference numerals are the same as those used in FIGS.

  In the embodiment shown in FIG. 3A, with respect to the connection terminal portion 3b at both ends of the cable portion 2, the insulating film 8 covering the end portion of the flat copper conductor 7 is peeled only on one side (the upper surface side in the figure), The upper surface of the flat copper conductor 7 is exposed. On the surface side (the lower surface side in the figure) where the flat copper conductor 7 on the opposite side is not exposed, the reinforcing plate 5b is joined from above the insulating film 8 which remains without being peeled off, and is attached to and detached from the pluggable electrical connector. Possible rigid connection terminal. In this case, the reinforcing plate 5b may be formed of metal since a plurality of flat copper conductors 7 are arranged on the insulating film 8 and electrically insulated. In this embodiment, as in FIG. 2A, one end may be, for example, a connection terminal portion (no gold plating is required) capable of soldering connection.

  Next, as shown in FIG. 3B, the exposed tin plating 7b of the flat copper conductor 7 on one side is removed by etching or the like. The tin plating 7b on the side bonded to the reinforcing plate 5b remains without being removed. The copper conductor 7a from which the tin plating 7b has been removed is subjected to a gold plating 10 via a nickel plating 9. As a result, the cable portion 2 is formed by covering a plurality of flat copper conductors 7 plated with tin with the insulating film 8, and the connection terminal portion 3 b is formed on the copper conductor 7 a via the nickel plating 9. A flat cable having a contact conductor 4 provided with gold plating 10 is obtained. In this embodiment, since the flat copper conductor 7 is held in alignment with the insulating film 8 adhered to one side, the removal of the tin plating 7b, nickel plating 9 and Gold plating 10 may be applied.

  According to the configuration of FIGS. 1 to 3 described above, the cable portion of the flat cable is secured to the surface of the copper conductor having a flat cross section, so that the flexibility of the cable can be ensured. . Moreover, even when flat copper conductors are arranged at a high density, the occurrence of migration between copper conductors can be suppressed, and the deterioration of the electrical insulation characteristics due to this can be prevented. Furthermore, the flat copper conductor can prevent the oxidation from being suppressed and the adhesiveness with the insulating film from being lowered.

  The connection terminal is plated with gold through the underlying nickel plating on the copper conductor from which the tin plating has been removed, so there is no crack between the tin plating and nickel plating layers, and the tin plating and gold plating. There is no generation of electrolytic corrosion due to contact with different metals. Moreover, even if it receives the contact pressure by an electrical connector, since tin plating is removed and nickel plating and gold plating are performed, whisker generation is suppressed and a highly reliable flat cable can be obtained.

  FIG. 4 is a diagram illustrating an example of the flat cable manufacturing method described above. In the figure, 11a and 11b are tape-like films, 12a and 12b are openings, 13 is a wide laminated tape, 14 is a laminated thin tape, 15 is a laminating roller, 16 is a slitter, and 17 is a cutter. Description of other reference numerals is omitted by using the same reference numerals as those used in FIG.

  The flat cable described with reference to FIGS. 1 to 3 is manufactured by a method as shown in FIG. 4, for example. As shown in FIG. 4A, the insulating film of the cable portion 2 is continuously supplied in the form of tape-like films 11a and 11b having an adhesive layer on the inside. On one tape-like film 11a, for example, openings 12a are formed in advance at predetermined intervals. In the other tape-shaped film 11b, when the opening 12b is formed so as to coincide with the opening 12a of the tape-shaped film 11a (in the case of the embodiment of FIG. 2), when the opening 12b is not formed (implementation of FIG. 3) In the case of form). Further, the reinforcing plate 5 may be bonded to the tape-shaped film 11b in advance so as to block the portion of the opening 12b when the opening 12b is formed.

  A large number of flat copper conductors 7 are sandwiched from upper and lower surfaces by tape-like films 11 a and 11 b, bonded and integrated by a laminating roller 15, and partially laminated at a portion of the opening 12. Is done. The laminating roller 15 can also be a heating roller depending on the type of adhesive layer applied to the tape-like films 11a and 11b. Next, the laminated wide laminated tape 13 is divided along the longitudinal direction by a slitter 16 to form a laminated thin tape 14 having a predetermined number of conductors, and is wound up once to be a wound body.

  Next, as shown in FIG. 4 (B), the winding body of the laminated thin tape 14 is rewound, and if the reinforcing plate 5 is not joined in the manufacturing process of FIG. The plate 5 is joined and the opening is reinforced. Next, the laminated narrow tape 14 is cut with a cutter 17 at the center of the opening 12a so that the flat copper conductor is exposed at both ends. Thereafter, as described with reference to FIGS. 1 to 3, the tin plating on the surface of the flat copper conductor in the portion exposed from both ends of the cable portion 2 is removed. Next, nickel plating and gold plating are applied to form a contact conductor 4 and a flat cable having a connection terminal portion 3 reinforced by a reinforcing plate 5 is obtained.

  FIG. 5 is a flowchart of the above-described flat cable manufacturing method. As described above, a large number of flat copper conductors tin-plated in step S1 are arranged in parallel, laminated and adhered and integrated by being sandwiched from both sides by a tape-like film with an adhesive. The tape-like film is provided with an opening that exposes at least one surface of the flat copper conductor at a portion to be a connection terminal portion. In the next step S2, a reinforcing plate is joined to the opposite portion where the opening is provided, and when this portion is hardened and both sides of the flat copper conductor are opened, one side is used as the reinforcing plate. Bond and fix the flat copper conductor.

  In step S3, the flat copper conductor portion exposed at the opened portion is cut into two portions to form a flat cable having connection terminal portions at both ends. Next, in step S4, the tin-plated portions of the flat copper conductor exposed at both ends of the flat cable are removed. For removing the tin plating, a physical method such as sand blasting or polishing, or a chemical method such as etching can be used.

  In step S5, nickel plating as a base metal is applied to the copper conductor portion from which the tin plating has been removed. If the nickel plating is left for a long time after the nickel plating, an oxide film is formed on the nickel plating and the performance as a base metal deteriorates. Therefore, in the next step S6, it is desirable to perform gold plating immediately after nickel plating. If the plating bath at this time is alkaline, the adhesiveness between the insulating film and the flat copper conductor is lowered. For this reason, in the present invention, it is desirable to perform the plating process in a weakly alkaline to acidic (pH 9 or less, preferably pH 7 or less) plating bath.

  The example of the manufacturing method shown in FIGS. 4 and 5 is a form in which the tin plating is removed, the nickel plating, and the gold plating are performed after cutting into the respective flat cables, but before the cutting into the flat cables. These processes may be performed. That is, the thin laminated tape 14 having the predetermined number of conductors shown in FIG. 4 is immersed in an etching solution in a wound state, and the tin plating on the flat copper conductor exposed from the openings 12a and 12b is removed. To do. Next, it is immersed in a nickel plating bath to perform nickel plating, and subsequently immersed in a gold plating bath for gold plating, and then cut into a predetermined flat cable. In this case, the laminated narrow tape 14 is wound in a form having a sufficient gap so that the plating solution or the like can easily penetrate between the winding layers.

It is a figure explaining the outline of the flat cable by this invention. It is a figure which shows the structural example of the connection terminal part by this invention. It is a figure which shows the other structural example of the connection terminal part by this invention. It is a figure explaining an example of the manufacturing method of the flat cable by this invention. It is a figure explaining an example of the manufacturing flow of the flat cable by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Flat cable, 2 ... Cable part, 3, 3a, 3b ... Connection terminal part, 4 ... Contact conductor, 5, 5a, 5b ... Reinforcement plate, 6 ... Electrical connector, 6a ... Connector contact piece, 7 ... Flat copper Conductor, 7a ... Copper conductor, 7b ... Tin plating, 8 ... Insulating film, 8a ... Film material, 8b ... Adhesive layer, 9 ... Nickel plating, 10 ... Gold plating, 11a, 11b ... Tape-like film, 12a, 12b ... Opening , 13 ... Laminated wide tape, 14 ... Laminated thin tape, 15 ... Laminated roller, 16 ... Slitter, 17 ... Cutter.

Claims (5)

A flat cable in which a plurality of flat copper conductors plated with tin are arranged in parallel and covered with an insulating film, and a connection terminal portion connected to an electrical connector is formed on at least one end,
The flat copper conductor portion used as the contact conductor of the connection terminal portion is a flat cable in which tin plating is removed and gold plating is applied to the portion from which the tin plating is removed through nickel plating. .   2. The flat cable according to claim 1, wherein the connection terminal portion is reinforced by exposing both sides of the flat copper conductor from the insulating film and directly joining one side to a reinforcing plate.   The connection terminal portion is reinforced by bonding one side of the flat copper conductor from the insulating film and bonding a reinforcing plate to the insulating film surface on the side where the flat copper conductor is not exposed. The flat cable according to claim 1. A method for producing a flat cable in which a plurality of flat copper conductors subjected to tin plating are arranged in parallel and covered with an insulating film to form a connection terminal portion connected to an electric connector at least at one end portion,
Removing the tin plating of the flat copper conductor portion to be the contact conductor of the connection terminal portion, applying nickel plating to the portion from which the tin plating has been removed, and subsequently performing gold plating after the nickel plating; Flat cable manufacturing method.   The flat cable manufacturing method according to claim 4, wherein a pH of the gold plating bath is 9 or less.

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