Abstract:
A cable assembly includes: a plurality of cables; a cable fixing member that fixes the cables together; and conductor layers, wherein the cable assembly is formed with a connecting end surface that includes thereon connecting ends of the cables, and the conductor layers are provided to cover surfaces of the connecting ends that are on the connecting end surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of PCT international application Ser. No. PCT/JP2010/061207 filed on Jun. 30, 2010 which designates the United States, incorporated herein by reference, and which claims the benefit of priority from Japanese Patent Application No. 2009-164883, filed on Jul. 13, 2009, incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a cable assembly that can set a plurality of cables in contact as one bundle. 
     2. Description of the Related Art 
     Conventionally, a cable assembly is used in a distal-end circuit of an endoscope to set two or more cables in contact as one bundle. A small-sized cable assembly is implemented by shortening the length of a hard section that functions as a connecting terminal section. Cable assemblies have a plurality of cables, with the cables being fixed together by using an array block that forms a hard section, and they have a cable connecting end surface that is formed by polishing the distal ends of the fixed cables in such a manner that the distal ends together form the same plane. The cables are set in contact by using an anisotropic conductive adhesive film (ACF: Anisotropic Conductive Adhesive Film) or an anisotropic conductive adhesive paste (ACP: Anisotropic Conductive Adhesive Paste), which is applied to the cable connecting end surface. Thereby, the cables are set in contact as one bundle and the length of the hard section is set short. 
     SUMMARY OF THE INVENTION 
     A cable assembly according to an aspect of the present invention includes: a plurality of cables; a cable fixing member that fixes the cables together; and conductor layers, wherein the cable assembly is formed with a connecting end surface that includes thereon connecting ends of the cables, and the conductor layers are provided to cover surfaces of the connecting ends that are on the connecting end surface. 
     The above and other features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an explanatory diagram that explains production of a cable assembly according to an embodiment of the present invention; 
         FIG. 2  is an explanatory diagram that explains a process of connecting the cable assembly to an external substrate; 
         FIG. 3  is a cross-sectional view of a state of a conductor layer that is near the cable-assembly end surface; 
         FIG. 4  is a cross-sectional view of a modification of the conductor layer; 
         FIG. 5  is a cross-sectional view of a modification of the conductor layer; 
         FIG. 6  is a cross-sectional view of a modification of the conductor layer that covers a shield wire; 
         FIG. 7  is a cross-sectional view of a modification of the conductor layer that covers a shield wire; 
         FIG. 8  is a cross-sectional view of a modification in which a connecting conductive member is provided; 
         FIG. 9  is a cross-sectional view of a modification in which a connecting conductive member and an insulating film are provided; and 
         FIG. 10  is a cross-sectional view of a modification in which a conductive projection and an insulator film are provided. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Exemplary embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited to these exemplary embodiments. 
       FIG. 1  is an explanatory diagram that explains production of a cable assembly according to an embodiment of the present invention.  FIG. 2  is an explanatory diagram that illustrates an application of the produced cable assembly. As illustrated in  FIG. 1 , in a cable assembly, a plurality of cables  11  are bound together, thereby forming a cable group  10 , and the cables  11  of the cable group  10  are fixed to each other by using a fixing member  20  that is made of a resin, etc. In this fixed state, in order to form a cable-assembly end surface S that is a connecting end surface of the cable assembly, part of the fixing member  20  is cut along a cutting plane  21 . In the cut surface, a connecting end surface, which leads to the cable group  10  is, is then polished so that the formed connecting end surface includes the connecting end of each of the cables  11  on the same plane. 
     Each of the cables  11  is a coaxial cable having the same diameter. A shield wire  14  is formed on an internal insulator  13 , surrounding the outer circumference of a cable core  12 . An external insulator  15  is formed on the outer circumference of the shield wire  14 . Although, in  FIG. 1 , nine (3×3) cables  11  are adjacently arranged in parallel in such a manner that the cross section is substantially a rectangular, it is allowable to use an array block in which cable insertion holes are formed in advance. If so, the cables  11  are not adjacently arranged. It is preferable to perform cutting and polishing involving the array block. 
     When the cable-assembly end surface S is formed by the polishing process, corresponding conductor layers  32  and  34  in a conductor layer pattern  30  are formed on the connecting end surfaces, which are cross sections of the cable core  12  and the shield wire  14  of each cable  11 . The conductor layers  32  and  34  are implemented by metallic films, and the conductor layer pattern  30  is formed by electrolytic plating, non-electrolytic plating, or spattering. The conductor layers  32  and  34  can have either a single-layer structure or a multilayer structure. A multilayer structure having a Ni/Au multilayer film, in which an Au layer is top layer and a Ni layer is under layer, is preferable because a strong bonding to a connecting end surface is formed. By using the Ni/Au multilayer film, various bonding methods become applicable, not only ACF and ACP bonding but also solder bump bonding and Au bump bonding, thereby increasing the flexibility in bonding. 
     A thus formed cable assembly  1  is connected, as illustrated in  FIG. 2 , to a substrate  40  on which a substrate pattern  41  is formed that corresponds to the conductor layer pattern  30  of the cable-assembly end surface S of the cable assembly  1 . An anisotropic conductive resin material, such as an ACF  50 , is inserted between the cable assembly  1  and the substrate  40 . By thermal compression bonding using the anisotropic conductive resin material, a conductive section  51  is formed on a compressed area, and the cable assembly  1  and the substrate  40  are bonded together. Because the areas where the conductor layers  32  and  34  are formed are convex and are protruding outward from the cable-assembly end surface S, the areas are under a high pressure and thus the conductive section  51  is formed via a dense filler, etc., within the ACF  50 . 
     In the present embodiment, the shapes of the conductor layers  32  and  34  are the same as the shapes of the cross sections of the cable core  12  and the shield wire  14 , respectively. As illustrated in  FIG. 3 , the actual cables  11  have a gap  12   a  between the cable core  12  and the internal insulator  13  and a gap  14   a  between the shield wire  14  and either the internal insulator  13  or the external insulator  15 . The conductor layers  32  and  34  are formed to be inserted in the gaps  12   a  and  14   a , respectively, near the cable-assembly end surface S. In other words, the conductor layers  32  and  34  are formed to be inserted in the gaps  12   a  and  14   a , respectively, like wedges. With a stress that occurs in a line-width direction near the cable-assembly end surface S, the cable core  12  and the internal insulator  13 , the shield wire  14  and the internal insulator  13 , and the shield wire  14  and the external insulator  15  are fixed together. In general, there is a concern that, due to a bending of the cables  11 , which are not fixed together by the fixing member  20 , or a change in temperature, etc., the cable core  12  and the shield wire  14  are pulled toward a direction indicated by an arrow A 1 ; however, the above-mentioned fixing prevents the above problem, and connecting end surfaces are reliably formed on the cable-assembly end surface S. In other words, the conductor layers  32  and  34  function as stoppers that prevent the cable core  12  and the shield wire  14  from moving inwardly in the direction indicated by the arrow A 1 . If the cable core  12  and the shield wire  14  are formed by a plurality of wires, such as twisted wires, the conductor layers  32  and  34  are inserted between wires like wedges near the cable-assembly end surface S. A stress occurring in the line-width direction makes them function as stoppers. 
     As illustrated in  FIG. 4 , overlapping conductor layers  52  and  54  may be applied, the widths of which exceed the width W 12  of the cable core  12  and the width W 14  of the shield wire  14 , respectively. That is, a width W 52  of the conductor layer  52  satisfies W52&gt;W12 and a width W 54  of the conductor layer  54  satisfies W54&gt;W14. In this case, parts of the conductor layers that protrude from the areas of the cable core  12  and the shield wire  14  prevent the cable core  12  and the shield wire  14  from moving inwardly in the A 1  direction, and at the same time, the conductor layers  52  and  54  are conductively connected to the cable core  12  and the shield wire  14 , respectively, on the cable-assembly end surface S. 
     Also, as illustrated in  FIG. 5 , ring-like shaped conductor layers  62 ,  63 ,  64  may be applied, which are only formed near an area at which the cable core  12  and the internal insulator  13  are in contact, near an area at which the shield wire  14  and the internal insulator  13  are in contact, and near an area at which the shield wire  14  and the external insulator  15  are in contact. Although the conductor area is reduced with this arrangement, inward movement of the cable core  12  and the shield wire  14  is prevented. 
     Furthermore, as illustrated in  FIG. 6 , in the case in which the shield wire  14  of each of the cables  11  is a shield wire having a common potential, it is preferable to connect the conductor layers  34  to each other via a conductor layer  35 . This facilitates connection of the shield wires  14  and reduces contact noises more effectively. This, especially, allows a shield area on the side of an external connecting terminal to be formed at one position. 
     Similarly, as illustrated in  FIG. 7 , the areas between the adjacent shield wires  14  may be covered with a conductor layer  38 . In other words, the entire area on the cable-assembly end surface S other than the areas of the cable core  12  and the internal insulator  13  may be covered with the conductor layer  38 . 
     Also, as illustrated in  FIG. 8 , connecting conductive members  72  and  74 , which are solder projections, may be further formed on the conductor layers  32  and  34 , respectively. The solder projections are formed by applying solder pastes or solder powders to the surfaces of the connecting ends of the cable core  12  and the shield wire  14 , and then fusing the solder by reflow. Because the solder projections can be directly used as connecting members that connect the cable assembly  1  to the external substrate  40 , this simplifies a connecting-material supplying process in connecting the cable assembly  1  to the substrate  40 . 
     Furthermore, as illustrated in  FIG. 9 , a resist may be applied between the connecting conductive members  72 ,  74  and the conductor films  32 ,  34  as an insulating film  80 . In this case, the thickness of the insulating film  80  is such that the distal ends of the connecting conductive members  72  and  74  are exposed. With this, a short-circuit between the cable core  12  and the shield wire  14  can be prevented. 
     Also, as illustrated in  FIG. 10 , conductive projections  92  and  94  may be formed on the conductor layers  32  and  34  of the connecting end surfaces of the cable core  12  and the shield wire  14 , respectively, by supplying an Ag paste to form projections and then hardening the projections by a heat. Furthermore, the cable-assembly end surface S is covered with an insulator film  90  and cause the conductive projections  92  and  94  to pierce through the insulator film  90  so that the distal ends of the conductive projections  92  and  94  are exposed on the surface of the insulator film  90 . With this, a short-circuit between the conductive projections  92  and  94  is prevented. Because the insulator film  90  is especially used in this case, an applying process of insulator, etc., is unnecessary; therefore, an insulating process can be performed easily. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.