Abstract:
A connector includes a plurality of contacts. The connector includes an insulator having a plurality of through-holes for receiving the contacts. A pair of contacts are disposed in each of the through-holes. Since two contacts are disposed in the through-hole in the insulator, even if a fault occurs in one of the contacts, signal transmission in the same line can continuously be used. Moreover, since large areas of contact portions of the contacts are secured even in normal use, the capacity of electric current is increased.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2006-240277, filed Sep. 5, 2006, the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a connector which is used in an electronic device having a plurality of circuit boards, and which electrically connects one of the circuit boards to another. In particular, the invention relates to an arrangement of contacts for use in the connector, and a structure of each contact. 
   2. Description of the Related Art 
   With developments in functions of electronic devices and with higher complexity of electronic devices, connectors each having many contact portions have been developed in order to interconnect many electrical wiring lines. In the case of the connector for use in, e.g. an artificial satellite, it is very difficult to repair or replace the connector after the artificial satellite is launched. Thus, high reliability is required in the connector as well as in the electronic devices which are mounted. 
   The electric connector that is used in the electronic device requiring high reliability may adopt various structures. For example, as regards a signal that is transmitted with use of the electric connector, if a fault occurs in one signal path, it is necessary to protect the signal that is transmitted. For this purpose, one method may be used in which the same signal is distributed to some other electrodes, thereby to secure the signal. However, the structure in which one signal is distributed to several electrodes increases the number of electrodes of the connector to be used, and also increases the fabrication cost. The method that provides such redundancy makes the wiring and the circuit itself complex. It is not practical to adopt such a method in all devices which are mounted. 
   Defective contact of a contact portion is a major factor of the defectiveness of the connector. In many cases, defective contact occurs due to resilient fatigue of the contact member itself, and contamination or damage of the surface of an associated electrode. 
   To solve this problem, a structure shown in  FIG. 7 , for instance, may be adopted. In this structure, a contact  70  is formed of a single metallic resilient member  71  for transmitting one signal. A distal end portion of the contact  70 , which comes in contact with an associated electrode  72 , is divided into two resilient contact arms  73 , thereby effecting two-point contact. A method using this structure is adopted in order to cope with occurrence of defective contact. However, even in the case where the distal end portion of one contact is divided into two parts to effect two-point contact, as shown in  FIG. 7 , the proximal portion of the contact is a single part. Thus, if a problem occurs in the part other than the part that comes in contact with the associated electrode, there is no measure to cope with such a problem. In addition, in the structure shown in  FIG. 7 , there are some cases in which a uniform and sufficient contact pressure can hardly be secured. 
   Another method is shown in an exploded view of  FIG. 8A  to  FIG. 8G , for instance. In this method, a silicone rubber connector  75  is used. In this silicone rubber connector  75 , an electrically conductive sheet  79  as shown in part of  FIG. 8B  is used as a signal transmission member  78  which is interposed between upper and lower wiring boards  76  and  77  as shown in parts of  FIG. 8A  and  FIG. 8D . As shown in parts of  FIG. 8E  and  FIG. 8F , the electrically conductive sheet  79  can be formed by aligning, with high density, electrically conductive fibers  81  or electrically conductive rubber, or metallic particles, in a sheet-like member formed of insulative silicone rubber. A frame  83  shown in part of  FIG. 8C  has an inner wall  84 . The inner wall  84  is located around the signal transmission member  78 , for example, for the purpose of positioning of the signal transmission member  78  and structural reinforcement of the silicone rubber connector  75 . 
   Part of  FIG. 8E  is a top view, and part of  FIG. 8F  is a cross-sectional view taken along line X-X′ in part of  FIG. 8E . As shown in parts of  FIG. 8E  and  FIG. 8F , electrically conductive fibers  81 , for instance, vertically extend, and accordingly an electric current flows only in the vertical direction. Part of  FIG. 8G  shows a contact state between the electrically conductive fibers  81  and contacts  85  of the wiring board. The resistance value of the connection part is determined by the number of electrically conductive fibers  81  per contact  85 . By virtue of this structure, only the associated contacts  85  and  86  can surely be electrically connected in the stacked state in which the electrically conductive sheet  79  is disposed between the upper and lower wiring substrates  76  and  77 . 
   In the silicone rubber connector, in particular, in the case where high reliability is required as in use for an artificial satellite, gold wires are buried, in typical cases, as the electrically conductive fibers  81 , thereby to ensure the reliability. As regards the silicone rubber connector in which expensive gold wires are buried, such other problems arise that after the connector is once used, the connector cannot be recovered and used. 
   In addition, if a great load is applied to the silicone rubber connector, the silicone rubber connector cannot be re-used. Besides, with use of metal wires with excessively small diameters, it is difficult to increase a transfer speed by increasing the frequency of a signal that is transmitted. 
   An example of patent documents relating to connectors is Jpn. Pat. Appln. KOKAI Publication No. 2002-190335. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention has been made in consideration of the above-described problem, and the object of the invention is to provide a connector which can easily secure a uniform and sufficient contact pressure without making wiring and circuits complex. In addition, the object of the invention is to provide a connector which requires no use of expensive metallic material, and to provide contacts which are used in the connector. 
   In an electronic device which is used in an apparatus requiring very high reliability, such as an artificial satellite, if a fault occurs in a connector which transmits signals, the apparatus as a whole may be affected. 
   To avoid this problem, a plurality of through-holes, each receiving a pair of contacts with a narrow pitch, are formed in an insulator that constitutes a housing of a connector. Each pair of contacts of plural contacts is inserted in the associated narrow through-hole in the insulator. A pair of electric contact portions, which are formed at both end portions of each contact, are aligned with, and put in contact with, associated contact lands on two opposed wiring boards. Thus, contact engaging portions are provided in each through-hole of the insulator, in which each contact is received, and the contact engaging portions are disposed to mate with engaging portions which are formed on the contact that is composed of a resilient metallic member. 
   Specifically, according to an embodiment in the specification, there is provided a connector which includes a plurality of contacts, and an insulator having a plurality of through-holes for receiving the plurality of contacts. At least two of the plurality of contacts are disposed in each of the plurality of through-holes. 
   Further, according to another embodiment in the specification, there is provided contacts which are used in a pair. Each contact includes a resilient member on which a pair of contact portions are formed. The pair of contact portions are formed at both ends of the contact and come in electrical contact with associated electrodes on two opposed wiring boards which are used in an electronic device. 
   According to still another embodiment in the specification, there is provided an electronic device including a plurality of wiring boards which are stacked. The wiring boards are electrically connected by connectors. Each of the connector includes an insulator having a plurality of through-holes for receiving a plurality of contacts. A pair of contacts of the plurality of contacts is disposed in each of the through-holes. 
   As has been described above, at least two contacts, which are devised to be properly adaptive to each through-hole of the insulator, are disposed in the associated through-hole. Thereby, highly reliable signal processing can be performed without additionally providing a signal for ensuring contact in association with another electrode. Therefore, the size of the connector can be reduced, and accordingly the size of the electronic device can be reduced. 
   In the present invention, with use of the metallic contact, repetitive re-use of the contact after removal is realized. In addition, with use of the metallic contact, use at high signal frequencies is possible. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       FIG. 1  is a perspective view showing an embodiment of the connector according to the present invention; 
       FIG. 2A  is a plan view of the connector according to the invention shown in  FIG. 1 ; 
       FIG. 2B  is an elevation view of the connector according to the invention shown in  FIG. 1 ; 
       FIG. 2C  is a side view of the connector according to the invention shown in  FIG. 1 ; 
       FIG. 3  shows a contact state between the connector according to the invention and upper and lower wiring boards; 
       FIG. 4  shows a contact state between the lower wiring board and a pair of contacts according to the invention, which are formed by using metallic resilient members; 
       FIG. 5  shows an example of the contact according to the invention; 
       FIG. 6  is a cross-sectional view showing an assembled state of an insulator and the contact according to the invention which is disposed in a through-hole formed in the insulator; 
       FIG. 7A  and  FIG. 7B  show a contact which has two resilient contact arms that are put in two-point contact with an associated electrode; and 
       FIG. 8A  to  FIG. 8G  are an exploded view of a silicone rubber connector which electrically connects upper and lower wiring boards  76  and  77 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  and  FIGS. 2A to 2C  show an embodiment of a connector  10  according to the present invention.  FIG. 1  is a perspective view of the connector according to the embodiment of the invention.  FIG. 2A  is a plan view of the connector of the invention shown in  FIG. 1 .  FIG. 2B  is an elevation view of the connector of the invention shown in  FIG. 1 .  FIG. 2C  is a side view of the connector of the invention shown in  FIG. 1 . 
   An insulator  11  serves as a connector housing which is formed of, e.g. a synthetic resin such as plastics. A plurality of through-holes  12 , which penetrate the insulator  11  in a vertical direction in the Figures, are formed in the insulator  11  in a linear arrangement. As shown in  FIG. 2A , opening portions  24  of the through-holes  12  are arranged in a linear fashion on an upper surface  42  of the insulator  11 . 
   A pair of contacts  13  and  13 ′, which are formed of electrically conductive resilient members, are inserted and fixed in parallel in each of the through-holes  12 . Electric contact portions  14  are formed on an upper part and a lower part of each contact  13 ,  13 ′. The electric contact portions  14  come in contact with associated electrode portions (i.e. contact lands) of an upper wiring board  15  and a lower wiring board  20  (see  FIG. 3 ) (an associated lower electrode of the upper wiring board  15  is not shown). 
   As shown in  FIG. 2B , first bosses  17  each having a large diameter and projecting upward of the insulator  11  are formed at right and left end portions of the insulator  11 . The first bosses  17  can be used for alignment between the insulator  11  and the lower wiring board  20 . In addition, as shown in  FIG. 2B , second bosses  18  each having a small diameter and projecting downward of the insulator  11  are formed at the right and left end portions of the insulator  11 . The second bosses  18  can be used for alignment between the insulator  11  and the upper wiring board  15 . 
   As shown in  FIG. 2A , a small-diameter boss receiving hole  21  is formed in each of the large-diameter first bosses  17 . A small-diameter boss projecting from a lower part of another insulator (not shown), which is disposed above the insulator  11 , can be inserted in the small-diameter boss receiving hole  21 . In a case where a plurality of wiring boards are stacked via a plurality of connectors  10 , small-diameter second bosses  18  of an upper connector  10  (not shown) are inserted in the small-diameter boss receiving holes  21  of the first bosses  17  of a lower connector  10 . Thereby, the connectors  10  can precisely be aligned. Examples of the wiring boards  15  and  20  include a board having wiring on its surface, a board on which multi-layer wiring is formed, a board including circuit components such as semiconductor components, and a board including electronic modules such as a display device and a switch device. 
   In general, a frame (not shown) having an inner wall surrounding the insulator  11  can be disposed around the insulator  11 , thereby to mechanically reinforce and protect the insulator  11 . For example, refer to the frame  83  shown in  FIG. 8C . The insulator  11  can be put in resilient contact with the inner wall of the frame  83  by a plurality of springs  19  (see  FIG. 2B ) formed on both end portions of the insulator  11 , and can thus be fixed. 
     FIG. 3  shows a connection state between the connector  10  and the upper wiring board  15  and lower wiring board  20 . It is understood that  FIG. 3  shows some of the mounted components of the embodiment which includes, for example, a plurality of wiring boards and a plurality of connectors.  FIG. 3  shows two wiring boards  15  and  20  alone, but a large number (e.g. ten) of wiring boards may be stacked in actual use via a plurality of connectors  10 . 
   Electrode portions  23 , which are arranged on the upper surface of the upper wiring board  15 , are electrodes for contact with contact portions of a connector (not shown) which is disposed above the upper wiring board  15 . As shown in  FIG. 3 , boss insertion holes  22  are formed in the upper wiring board  15  and lower wiring board  20 . The boss insertion holes  22  are used for alignment between the connector  10  and the wiring board  15 ,  20 . 
     FIG. 4  shows a contact state between the lower wiring board  20  and a pair of contacts  13  which are formed by using metallic resilient members.  FIG. 4  shows the state in which the insulator  11  and other pairs of contacts are removed.  FIG. 4  shows an example of use in which a pair of contacts, which have the same shape, are disposed in opposite directions. The present invention is not limited to the use of the paired contacts having the same shape. 
   In  FIG. 4 , the paired contacts  13  and  13 ′ are disposed vertically in parallel to each other. The paired contact portions  14  at the lower parts of the contacts  13  and  13 ′ are put in resilient contact with the same electrode portion  16  formed on the surface of the lower wiring substrate  29 . Thus, even if a fault occurs in one of the contacts  13 , normal signal transmission is enabled by the other contact  13 ′. In order to keep good contact with the electrode portion  16 , the contact surfaces  14  of the contacts  13  and  13 ′ should preferably be formed as rolled surfaces, and not as broken surfaces. 
     FIG. 5  shows an example of the contact  13  that is used in this embodiment. The shape of the contact  13 , which is shown in  FIG. 5 , can be obtained by punching a thin metal plate or by subjecting it to a lithography process. The contact surface  14  is formed by bending itself in a rearward direction of the sheet surface of  FIG. 5 , for example, in a substantially U shape as shown in  FIG. 4 . This structure can increase the contact area of the contact surface  14  with the electrode portion formed on the surface of the board  15 . By adopting this structure, the contact surface  14  can be formed as a rolled surface, and not as a broken surface. 
   In this invention, the shape of the contact is not limited to the example shown in  FIG. 5 . It should suffice if the contact is formed of a resilient member and has at least two contact surfaces which come in electrical contact with associated electrode portions (contact lands) formed on the two opposed wiring boards. 
   A vertically extending columnar portion  27  of the contact  13  of the embodiment shown in  FIG. 5  includes a hook-shaped engaging portion  25  and a projection-shaped engaging portion  26  for engaging the contact  13  with the inner wall of the insulator  11 . Thereby, the contact  13  can surely be fixed on the inner wall of the insulator  11 . 
   In addition, as shown in  FIG. 5 , strip-shaped portions  28 , which extend in up-and-down directions in a meandering fashion to the upper and lower contact portions  14 , may be formed at middle parts of the columnar portion  17 . Each strip-shaped portion  28  may include a U-shaped portion  30  which extends in a horizontal direction, and a U-shaped portion  31  which extends in a vertical direction. By virtue of such meandering portions, flexible and exact contact is realized between the contact  13  and the electrode portions  16  of the wiring boards. 
     FIG. 6  shows a cross section taken along line Y-Y′ in  FIG. 2 .  FIG. 6  shows the inside of the through-hole  12  formed in the insulator  11  and the contact  13  that is inserted and fixed in the through-hole  12 . A groove portion  36 , which constitutes an engaging portion for engaging the hook-shaped engaging portion  25  of the contact  13  and restricting downward movement of the contact  13 , is formed in an upper part of the inner wall  35  of the insulator  11 . In addition, an engaging portion  40  having a projection portion  38 , which is mated with the projection-shaped engaging portion  26  of the contact  13 , is formed in the through-hole  12 . 
   The paired contacts  13  are disposed such that they are separated by a predetermined distance by a partial partition wall  41  within the through-hole  12 . In this embodiment, two contacts are disposed in the through-hole  12 . Alternatively, three contacts, for instance, may be disposed in the through-hole  12 . 
   In the present invention, at least two contacts are disposed at mutually opposed positions in each of the plural through-holes  12  of the insulator  11 . Thus, the engaging portion with the insulator can be disposed at a position separated from the contact portion, and the contact may include a resilient portion and a vertically bent portion of the contact portion which extends from that separated position. By virtue of this structure, even if the contacts are disposed at mutually opposed positions, their contact portions may be arranged in two rows on the same line. 
   The embodiment of the invention has been described above. However, the invention is not limited to the embodiment, and various modifications may be made, as needed.