Abstract:
A contact type electrical connector includes a first plunger in contact with one member; a second plunger in contact with another member and electrically connected to the first plunger, whereby the two members are electrically connected through the first plunger; a cylindrical support member for slidably and elastically supporting the first and second plungers with a connection portion of the first plunger and a connection portion of the second plunger overlapping and electrically connected; and a compression coil spring surrounding the outer peripheries of the first and second plungers with the connection portions thereof supported by the cylindrical support member and brought into contact with a spring receiving portion of each of the plungers so as to urge the plungers apart. The cylindrical support member, which may be formed as a coil spring, serves to improve electrical connection between the plungers.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims, under 35 USC 119, priority of Japanese Application No. 2009-217722 filed Sep. 18, 2009 and Japanese Application No. 2008-286981 filed Nov. 7, 2008. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a contact to be touched by an electrode provided in a wiring substrate, a semiconductor integrated circuit and the like and an electrical connecting apparatus. 
     2. Description of Related Art 
     A contact for electrically connecting electric circuits and the like of opposedly disposed wiring substrates to each other is known in general. Examples of such a contact include those described in U.S. Pat. No. 7,025,602 (Patent Document 1) and Japanese Patent Laid-Open No. 2004-152495 (Patent Document 2), for example. 
     A contact  1  in Patent Document 1 is, as shown in  FIGS. 2 and 3 , constituted by two contact pins  2  with the same shape and a coil spring  3 . 
     The contact pin  2  is mainly constituted by a locking claw  4 , a locking hole  5 , a flange portion  6 , and a pin distal end portion  2 A. The two locking claws  4  are provided to oppose each other and are supported by flexible supporting rod portions  4 A. As a result, the two locking claws  4  are brought close to and separated from each other. The locking hole  5  is a hole in which the locking claws  4  are fitted and is formed in a rectangular shape according to a width of the locking claw  4 . As a result, by fitting the two contact pins  2  opposing each other with displacement by 90 degrees, the two locking claws  4  are locked by openings of the locking hole  5 , respectively, and they will not drop off. The flange portion  6  is a portion to which the coil spring  3  is brought into contact. By fitting the two contact pins  2  with each other with displacement by 90 degrees in a state inserted into the coil spring  3 , respectively, both ends of the coil spring  3  are brought into contact with each flange portion  6 , and the contact  1  is assembled. Both end portions of the contact  1  assembled in a state where the two contact pins  2  are fitted with each other are made into the pin distal end portions  2 A to be touched by an electrode or the like and electrically connected. 
     A contact  7  in Patent Document 2 is, as shown in  FIG. 4 , constituted by a plunger  8  and a spring  9 . 
     The plunger  8  is formed in an elongate plate shape, a wide portion  8 A receiving the spring  9  is provided at an upper part thereof, and a terminal portion  8 B to be touched by an electrode is formed at an upper part of the wide portion  8 A. At a lower part of the wide portion  8 A, a core rod portion  8 C to be inserted into the spring  9  capable of vertical movement is formed. The spring  9  is formed with an inner diameter such that the core rod portion  8 C can be inserted capable of vertical movement. A lower end portion of the spring  9  is converged so as to be touched by an electrode or the like. 
     There is also a structure as in Japanese Patent Laid-Open No. 11-317270 (Patent Document 3). A socket for an electric component in Patent Document 3 has a contact member to be in contact with a terminal of an electric component, a substrate conductive member formed by a plate material having conductivity and to be connected to a print circuit substrate, and a coil spring disposed between the contact member and the substrate conductive member and having the both conducted. The contact member and the substrate conductive member are not in contact with each other but connected by the coil spring. 
     SUMMARY OF THE INVENTION 
     However, with the contact  1  in the above Patent Document 1, if the locking claws  4  repeatedly touch a peripheral edge of the locking hole  5  with expansion and contraction of the contact  1  in a state in which the locking claws  4  of one of the contact pins  2  are fitted in the locking hole  5  of the other contact pin  2 , the locking claws  4  or the supporting rod portions  4 A might be damaged by abrasion or the like, and durability is not enough. 
     Also, since with regard to each of the contact pins  2 , only the locking claws  4  are fitted in the locking hole  5  on the opposite side and their contact area is small, electrical connection is mainly performed by the coil spring  3 . However, since the portions of the locking claw  4  and the supporting rod portion  4 A need to be expanded and fitted in the locking hole  5  on the opposite side in a state inserted into the coil spring  3 , it is difficult to have an inner diameter such that the coil spring  3  tightens the contact pin  2 . Moreover, since the coil spring  3  is a compression spring and has fewer contact points with the contact pin  2 , close contact between each of the contact pins  2  and the coil spring  3  is weak. Therefore, a contact portion between the flange portion  6  of each of the contact pins  2  and the coil spring  3  becomes a major passage through which electricity flows, but a small contact area easily causes abrasion, corrosion and the like, and electrical contact is poor. Therefore, there are problems that contact failure can easily occur and durability is not enough. 
     Also, with the contact  7  in Patent Document 2, since the inner diameter of the spring  9  is set at a dimension through which the core rod portion  8 C of the plunger  8  can be inserted capable of vertical movement, the plunger  8  and the spring  9  might or might not touch each other, which is poor in electrical contact. Therefore, the plunger  8  and the spring  9  are mainly electrically connected at a contact between the wide portion  8 A of the plunger  8  and the upper end portion of the spring  9 . Therefore, there are problems that a small contact area can easily cause contact failure due to abrasion, corrosion and the like, electrical contact is poor, and durability is not enough. 
     Also, in Patent Document 3, since the plungers do not touch each other but are only electrically connected by a spring, there is a problem that electrical contact is poor. 
     The present invention was made in view of the above problems and has an object to provide a contact which solves contact failure and improves durability and an electrical connecting apparatus using the contact. 
     A contact according to the present invention was made in order to solve the above problems and is constituted by a first plunger in contact with one of members, a second plunger for having the one member and the other member electrically conducted in collaboration with the first plunger by touching the other member in a state electrically connected to the first plunger, a cylindrical support member for slidably and elastically supporting a connection portion of the first plunger and a connection portion of the second plunger in an overlapped and electrically connected state, and a compression coil spring covering outer peripheries of the first plunger and the second plunger in a state in which each of the connection portions thereof is supported by the cylindrical support member and brought into contact with spring receiving portions of the plungers so as to urge the plungers in a direction to be separated from each other. 
     In an electrical connecting apparatus for conducting a test in contact with an electrode of a specimen, a contact disposed at a position corresponding to each electrode of the specimen and brought into contact with each of the electrodes for conduction is provided, and the above-mentioned contact is used as the contact. 
     Advantageous Effects Of Invention 
     In a contact and an electrical connecting apparatus according to the present invention, since it is so constructed that the connection portion of the first plunger and the connection portion of the second plunger are supported slidably and elastically by the cylindrical support member in a state overlapped with each other and electrically connected, electric contact between the plungers is improved and durability is improved with use of the contact. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partially exploded front view illustrating a contact according to a first embodiment of the present invention. 
         FIG. 2  is a perspective view illustrating a first prior-art example. 
         FIG. 3  is an exploded perspective view illustrating the first prior-art example. 
         FIGS. 4A and 4B  are exploded perspective views illustrating a second prior-art example, and  FIG. 4C  is an assembled perspective view. 
         FIG. 5  is a sectional view on arrow of A-A line in  FIG. 1 . 
         FIG. 6  is a front view illustrating a contact according to the first embodiment of the present invention. 
         FIG. 7  is a front view illustrating a first plunger of the contact in  FIG. 6 . 
         FIG. 8  is a side view illustrating the first plunger in  FIG. 7 . 
         FIG. 9  is a front view illustrating a compression coil spring. 
         FIG. 10  is a front view illustrating a cylindrical support member. 
         FIG. 11  is a partially exploded front view illustrating a contact according to a second embodiment of the present invention. 
         FIG. 12  is a sectional view on arrow of B-B line in  FIG. 1 . 
         FIG. 13  is a partially exploded side view illustrating the contact according to the second embodiment of the present invention. 
         FIG. 14  is a front view illustrating the contact according to the second embodiment of the present invention. 
         FIG. 15  is a front view illustrating a first plunger according to the second embodiment of the present invention. 
         FIG. 16  is a side view illustrating the first plunger according to the second embodiment of the present invention. 
         FIG. 17  is a partially exploded front view illustrating a contact according to a third embodiment of the present invention. 
         FIG. 18  is a partially exploded side view illustrating the contact according to the third embodiment of the present invention. 
         FIG. 19  is a bottom view of  FIG. 18 . 
         FIG. 20  is a sectional view of a portion in which a connection portion of the first plunger and a connection portion of a second plunger of the contact according to the third embodiment of the present invention are overlapped with each other. 
         FIG. 21  is a partially exploded front view illustrating a contact according to a fourth embodiment of the present invention. 
         FIG. 22  is a partially exploded side view illustrating the contact according to the fourth embodiment of the present invention. 
         FIG. 23  is a partially exploded side view illustrating a contact according to a fifth embodiment of the present invention. 
         FIG. 24  is a planar sectional view illustrating the contact according to the fifth embodiment of the present invention. 
         FIG. 25  is a plan view illustrating an electrical connecting apparatus according to a sixth embodiment of the present invention. 
         FIG. 26  is a sectional view illustrating the electrical connecting apparatus according to the sixth embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A contact and an electrical connecting apparatus according to embodiments of the present invention will be described below referring to the attached drawings. 
     (A) First Embodiment 
     A contact according to a first embodiment will be described below.  FIG. 1  is a partially exploded front view illustrating the contact according to this embodiment,  FIG. 5  is a sectional view on arrow of A-A line in  FIG. 1 ,  FIG. 6  is a front view illustrating the contact according to this embodiment,  FIG. 7  is a front view illustrating a first plunger,  FIG. 8  is a side view illustrating first and second plungers,  FIG. 9  is a front view illustrating a compression coil spring, and  FIG. 10  is a front view illustrating a cylindrical support member. Although  FIG. 7  shows the first plunger, the second plunger has the same structure as that of the first plunger in  FIG. 7 . The contact of this embodiment electrically connects electric circuits and the like of opposing wiring substrates to each other by electrically conducting a member such as one of electrodes and the like and a member such as the other electrode or the like, similarly to the conventional contacts. This contact can be used as a spring probe, a pogo pin, and the like. Since a portion other than the contact is similar to conventional or known techniques, only the contact will be described below based on  FIGS. 1 and 5  to  10 . 
     A contact  10  of this embodiment is constituted by a first plunger  11 , a second plunger  12 , a cylindrical support member  13 , and a compression coil spring  14 . 
     The first plunger  11  is a plunger to be brought into contact with a member B 1  such as a bump electrode or the like on one side. The second plunger  12  is a plunger to be brought into contact with a member B 2  such as an electrode pad of a wiring substrate or the like on the other side in a state electrically connected to the first plunger  11  and for having the one member B 1  and the other member B 2  electrically conducted. The first plunger  11  and the second plunger  12  are constituted by plungers having the same shape. The plungers having the same shape are made as the first plunger  11  and the second plunger  12  by reversing the directions and overlapping connection portions  16 , which will be described later. Each of the plungers  11  and  12  is formed by punching a plane material with a die. At this time, both sides of connecting rod portions  16 A, which will be described later, are tapered. This taper is provided so that when the two connecting rod portions  16 A are overlapped, their sections become hexagonal. 
     Each of the plungers  11  and  12  is constituted by the connection portion  16 , a spring receiving portion  17 , and a contact piece  18 . 
     The connection portion  16  is constituted by the connecting rod portion  16 A and a flange portion  16 B. The connection portion  16  is a portion overlapped when the first plunger  11  and the second plunger  12  are connected to each other. The connecting rod portion  16 A is formed so as to have a trapezoidal sectional shape as shown in  FIG. 5  by tapering the both sides in punching work of a plane material. The portion is formed such that, in a state where the connection portions  16  of the plungers  11  and  12  are overlapped with each other, the sectional shapes become hexagonal, and six apexes are in contact with the inside of the cylindrical support member  13 , which is their circumscribed circle. 
     The flange portion  16 B is a portion for preventing drop off (removal from each other) of the plungers  11  and  12  from the cylindrical support member  13 . That is, the flange portion  16 B is formed by enlarging the connection portion  16  of the plungers  11  and  12  and is a portion for preventing the plungers  11  and  12  from dropping off the cylindrical support member  13  by being locked by both end portions of the cylindrical support member  13 . Each of the flange portions  16 B is formed with a dimension larger than the inner diameter of the cylindrical support member  13 . 
     The spring receiving portion  17  is a portion for receiving the compression coil spring  14 . The spring receiving portion  17  is formed with a distal end side of each of the plunger  11  and  12  having a dimension slightly larger than an outer diameter of the compression coil spring  14  and is brought into contact with the both end portions of the compression coil spring  14 , respectively. As a result, by means of the compression coil spring  14  in contact with each of the spring receiving portion  17 , each of the plungers  11  and  12  is urged in a direction to be separated from each other in a state in which the connection portions  16  are supported by the cylindrical support member  13  so as not to drop off. 
     The spring receiving portion  17  is constituted by a flange portion  17 A and an enlarged portion  17 B. The flange portion  17 A is a portion with which the compression coil spring  14  is brought into contact so as to receive the compression coil spring  14 . The portion is formed substantially equal to or slightly larger than the outer diameter of the compression coil spring  14  and supports the compression coil spring  14  by being brought into firm contact. When the both end portions of the compression coil spring  14  are brought into contact with the flange portion  17 A of the plungers  11  and  12 , the plungers  11  and  12  are electrically conducted through the compression coil spring  14 . The enlarged portion  17 B is a member for guiding the compression coil spring  14 . The enlarged portion  17 B is formed so as to extend from the flange portion  17 A into the compression coil spring  14 . The enlarged portion  17 B is formed substantially equal to or slightly smaller than an inner diameter of the compression coil spring  14  and supports the compression coil spring  14  so as to prevent displacement thereof. 
     The contact piece  18  is a member to be brought into contact with each of the members B 1  and B 2  for electrically connecting these members. The contact piece  18  has its distal end constituted by a plurality of projections and enters into the members B 1  and B 2  to be electrically connected. 
     The cylindrical support member  13  is a member for slidably and elastically supporting the connection portion  16  of the first plunger  11  and the connection portion  16  of the second plunger  12  by overlapping them in an electrically connected state. The cylindrical support member  13  is specifically constituted by a conductive coil spring to be brought into elastic contact with the connection portions  16  of the plungers  11  and  12  and to slidably support them by elastically varying a diameter thereof. The coil spring is constituted by a tight spring in which a wire rod is wound plural times so as to be in close contact with each other and cylindrical. The inner diameter of the cylindrical support member  13  is set slightly smaller than a diameter of the circumscribed circle of the hexagon in which the connecting rod portions  16 A are overlapped with each other. As a result, the cylindrical support member  13  can allow mutual sliding and prevents drop-off in a state in which the connecting rod portions  16 A are in close contact with each other by elastically supporting the connecting rod portions  16 A of the connection portions  16  with some tightening force and reliably maintains electrical connection. That is, even if the plungers  11  and  12  are displaced from each other due to expansion and contraction of the contact  10 , the displacement is allowed and the plungers  11  and  12  are supported so that the electrical connection between the plungers  11  and  12  is reliably maintained. A path for this electrical connection is a portion where the connecting rod portions  16 A are brought into close contact with each other in a wide area, a portion where each of the connecting rod portions  16 A is pressed into contact with the cylindrical support member  13 , and a portion where the flange portions  17 A are in contact at the both end portions of the compression coil spring  14 . Even if the plungers  11  and  12  are displaced from each other and a contact area between each of the connecting rod portions  16 A is reduced, the pressure contact between each of the connecting rod portions  16 A and the cylindrical support member  13  is reliably maintained, and the path for electrical connection is reliably maintained. 
     The compression coil spring  14  is a spring for urging each of the plungers  11  and  12  in a direction to be separated from each other. The compression coil spring  14  covers outer peripheries of the plungers  11  and  12  and the cylindrical support member  13  and is brought into contact with the flange portions  17 A of the spring receiving portions  17 , respectively, at the distal end sides of the plungers  11  and  12  for urging them in a direction to be separated from each other in a state where the connection portions  16  of the first plunger  11  and the second plunger  12  are supported by the cylindrical support member  13 . 
     The contact  10  constituted as above is used as follows. 
     The contact  10  is attached to an inspecting device or the like as a spring probe or a pogo pin. In a state in which the contact piece  18  of the second plunger  12  is in contact with the electrode member B 2  on the inspecting device side, if the contact piece  18  of the first plunger  11  is brought into contact with the member B 1  such as a bump electrode of a circuit to be inspected, the contact  10  operates as follows. 
     When the contact piece  18  of the first plunger  11  is brought into contact with the member B 1  and pressed onto the same, the first plunger  11  is pressed on the second plunger  12  side by that action. As a result, the connecting rod portion  16 A of the first plunger  11  is displaced from the connecting rod portion  16 A of the second plunger  12  in a state supported by the cylindrical support member  13 , and the compression coil spring  14  received by the spring receiving portion  17  is compressed. Then, by means of a repulsion force of the compression coil spring  14 , each of the contact pieces  18  is pressed onto and enters into each of the members B 1  and B 2 . 
     At this time, since each of the connecting rod portions  16 A of each of the plungers  11  and  12  is displaced in a state supported by the cylindrical support member  13 , a state in which each of the connecting rod portions  16 A is in contact with each other and electrically connected is reliably maintained. Moreover, even if each of the connecting rod portions  16 A is displaced from each other, as shown in  FIG. 5 , the cylindrical support member  13  and each of the connecting rod portions  16 A are brought into reliable contact through a large number of point contacts at positions between each apex of the hexagon and the inside of the cylindrical support member  13 , and the state in which each of the connecting rod portions  16 A and the cylindrical support member  13  are electrically connected is reliably maintained. Also, even if the connecting rod portion  16 A on the upper side and the connecting rod portion  16 A on the lower side are displaced from each other in a direction where shaft centers of the connecting rod portions  16 A are displaced from each other, in the horizontal direction in  FIG. 5 , for example, or even if each of the connecting rod portions  16 A is displaced in a direction to be separated from their contact faces, each of the connecting rod portions  16 A and the cylindrical support member  13  are in contact through a large number of point contacts, and the electrically connected state is reliably maintained. 
     Moreover, since the spring receiving portions  17  of the plungers  11  and  12  are pressed into contact with both end portions of the compression coil spring  14 , the electrically connected state of the plungers  11  and  12  is also reliably maintained by the compression coil spring  14 . 
     As a result, each of the members B 1  and B 2  is reliably connected to each other by a path electrically connected through each of the connecting rod portions  16 A whose electrically connected state is reliably maintained by the cylindrical support member  13  and a path electrically connected through the compression coil spring  14  brought into contact with the flange portion  17 A of each of the spring receiving portions  17 . That is, the members B 1  and B 2  are electrically connected by the contact  10  reliably. In this state, an electric signal or the like is transmitted between the members B 1  and B 2  through the contact  10 . 
     When the contact piece  18  of the first plunger  11  is separated from the member B 1  upon the end of an inspection or the like, the first plunger  11  and the second plunger  12  are urged by the compression coil spring  14  in a direction to be separated from each other. At this time, in each of the plungers  11  and  12 , the flange portion  16 B of the connecting rod portion  16 A is locked by the both end portions of the cylindrical support member  13  and drop-off is prevented. 
     In the case of the subsequent use, similarly to the above, the contact piece  18  of the first plunger  11  is brought into contact with the member B 1 , the cylindrical support member  13  allows displacement of the connecting rod portions  16 A and electrically connects them, and an inspection signal or the like is transmitted. 
     As mentioned above, since each of the connecting rod portions  16 A of the first plunger  11  and the second plunger  12  are supported by the cylindrical support member  13  slidably and elastically in a state overlapped with each other and electrically connected to each other, electrical contact between each of the plungers  11  and  12  is improved. Moreover, combined with the compression coil spring  14  in contact with each of the spring receiving portions  17 , electrical contact between each of the plungers  11  and  12  can be drastically improved. 
     Also, since each of the connecting rod portions  16 A of the first plunger  11  and the second plunger  12  is supported by the cylindrical support member  13  slidably and elastically in a state overlapped with each other and electrically connected to each other, a self cleaning action of the contact portion works by use in which the connecting rod portions  16 A are displaced from each other repeatedly and maintains electrical contact between each of the plungers  11  and  12  favorable, and durability of the contact  10  is improved. That is, even if each of the plungers  11  and  12  slides repeatedly or slides with the shaft core of each of the plungers  11  and  12  displaced, the cylindrical support member  13  elastically supports each of the plungers  11  and  12  and allows the displacement and maintains the electrical contact between the plungers  11  and  12  favorable. As a result, electrical contact is improved, and durability of the contact  10  is improved. 
     Also, since the cylindrical support member  13  is constituted by a tight spring and its diameter is elastically changed and elastically brought into contact with the connecting rod portion  16 A of each of the plungers  11  and  12  and slidably supported, displacement of the connecting rod portion  16 A is flexibly followed up, and an electrically connected state between each of the connecting rod portions  16 A and between the cylindrical support member  13  and each of the connecting rod portions  16 A can be reliably maintained. 
     Since the flange portion  16 B in each of the connection portions of each of the plungers  11  and  12  is locked by the both end portions of the cylindrical support member  13 , drop-off of the plungers  11  and  12  can be reliably prevented. 
     Since each of the connecting rod portions  16 A is formed so that the sectional shape becomes a hexagon in an overlapped state, each apex of the hexagon and the cylindrical support member  13  are brought into contact with each other. Also, since the cylindrical support member  13  is made of a tight spring, each of the connecting rod portions  16 A and the cylindrical support member  13  are in contact at a large number of points, and combined with contact between each of the connection portions  16 , electrical contact is drastically improved. 
     Since the apparatus is constituted by the plungers  11  and  12  and the like in a simple structure, the number of components is small, by which costs can be reduced. 
     Also, since the plungers  11  and  12  are formed by punching a plate material with a die, its manufacture is easy, and a manufacturing cost of the contact can be reduced. 
     (B) Second Embodiment 
     Subsequently, a second embodiment of the present invention will be described. An entire configuration of the contact according to this embodiment is substantially the same as the contact of the above-mentioned first embodiment. Thus, the same reference numerals are given to the same members, and the description will be omitted.  FIG. 11  is a partially exploded front view illustrating a contact according to this embodiment,  FIG. 12  is a sectional view on arrow of B-B line in  FIG. 1 ,  FIG. 13  is a partially exploded side view illustrating the contact according to this embodiment,  FIG. 14  is a front view illustrating the contact according to this embodiment,  FIG. 15  is a front view illustrating a first plunger, and  FIG. 16  is a side view illustrating the first plunger. 
     A characteristic of the contact in this embodiment is a connection portion  19 . The connection portion  16  in the above-mentioned first embodiment has a trapezoidal section so as to become a hexagon when two portions are overlapped, but in this embodiment, a section of the connection portion  19  is a rectangular shape so as to become a square close to a regular tetragon when two portions are overlapped. That is, as shown in  FIG. 12 , a connecting rod portion  19 A of the connection portion  19  is formed with a rectangular section. They are formed so that their sectional shape is a square close to a regular tetragon when the two connecting rod portions  19 A are overlapped. By overlapping the two connecting rod portions  19 A, a square shape is formed, and the inside of the cylindrical support member  13  is circumscribed. That is, the sectional shape of the connecting rod portion  19 A is set so that the inside of the cylindrical support member  13  becomes a circumscribed circle with respect to the square sectional shape when the two connecting rod portions  19 A are overlapped. Here, the sectional shape obtained by overlapping the two connecting rod portions  19 A is, as shown in  FIG. 12 , substantially a square. The sectional shape obtained by overlapping the two connecting rod portions  19 A may be a rectangular shape. In this case, each dimension is adjusted such that each apex of the rectangle is circumscribed by the inside of the cylindrical support member  13 . 
     As a result, the same actions and effects as those of the above-mentioned first embodiment are exerted except that the sectional shape obtained by overlapping the two connecting rod portions  19 A is circumscribed by the inside of the cylindrical support member  13  at four apexes. 
     (C) Third Embodiment 
     Subsequently, a third embodiment of the present invention will be described. 
     As for a contact of this embodiment, two contacts are provided so that one of a first plunger or a second plunger sandwiches the other from both sides. In this embodiment, two first plungers are provided, and the first plungers are configured so as to sandwich the second plunger from the both sides. 
     A contact  20  of this embodiment is, as shown in  FIGS. 17 to 20 , constituted by a first plunger  21 , a second plunger  22 , a cylindrical support member  23 , and a compression coil spring  24 . 
     The two first plungers  21  are provided so as to sandwich the second plunger  22  from the both sides. The two first plungers  21  are formed in the same shape. The first plunger is also formed by punching similarly to the first embodiment. Each of the first plungers  21  is independently supported by the cylindrical support member  23 . The compression coil spring  24  is in contact with a spring receiving portion  27  of the first plunger  21  to incline its contact portion freely and allows independent sliding of the two first plungers  21 . As a result, each of the first plungers  21  is individually displaced independently according to the shape of the member B 1  so as to be reliably brought into contact. Each of the first plungers  21  is constituted by a connection portion  26 , the spring receiving portion  27 , and the contact piece  28 . 
     The connection portion  26  is constituted by a connecting rod potion  26 A and a flange portion  26 B. The connecting rod portion  26 A is a portion to be overlapped when the first plunger  21  and the second plunger  22  are connected to each other. The connecting rod portion  26 A is formed in a strip shape narrower than a connection portion  31  of the second plunger  22 , which will be described later. As a result, a width and a thickness of the connecting rod portion  26 A is set so that, in a state where the two first plungers  21  and the single second plunger  22  are overlapped with each other, two corner portions located outside the connection portion  26  of each of the first plungers  21  (four corner portions in total) and four corner portions of the connection portion  31  of the second plunger  22  are located at apexes of an octagon (See  FIG. 20 ). The eight apex positions forming this octagon are set so that an inner diameter of the cylindrical support member  23  becomes a circumscribed circle of the eight apexes. The octagon formed by the eight apex positions may be a regular octagon or any other octagons. 
     The flange portion  26 B is a portion for preventing drop-off of the first plunger  21 . Here, since it will be understood more easily if description is made at the same time as that of a flange portion  31 B of the second plunger  22 , which will be described later, the flange portion  31 B of the second plunger  22  will be used as appropriate. The flange portion  31 B is a portion for preventing the second plunger  22  from dropping off. Each of the flange portions  26 B and  31 B is formed with a dimension larger than the inner diameter of the cylindrical support member  23  in a state where the connection portions  26  and  31  of the plungers  21  and  22  are overlapped with each other and surrounded by the cylindrical support member. 
     The spring receiving portion  27  is a portion with which the compression coil spring  24  is brought into contact and receiving a pressure of the compression coil spring  24 . The spring receiving portion  27  has a distal end side of the first plunger  21  formed with a dimension slightly larger than an outer diameter of the compression coil spring  24 . The spring receiving portion  27  of the first plunger  21  and a spring receiving portion  32  of the second plunger  22 , which will be described later, are brought into contact with the compression coil spring  24 , which urges them in a direction to be separated from each other. At this time, the connection portions  26  and  31  of the plungers  21  and  22  are supported by the cylindrical support member  23  so as not to drop off. 
     The contact piece  28  is a member to be brought into contact with the member B 1  for electrical connection. The contact piece  28  has its distal end constituted by a plurality of (two in this embodiment) projections. The contact piece  28  is provided on each of the two first plungers  21  and constitutes a large number of (four in this embodiment) contact points at one of the distal end portions of the contact  20 . Moreover, combined with the fact that the two first plungers  21  can slide independently, the electrical contact between the first plunger  21  and the member B 1  is improved. 
     The second plunger  22  is a plunger sandwiched by the two first plungers  21  and connected to each by the cylindrical support member  23 . The second plunger  22  is formed by punching a plate material similarly to the first plunger  21 . The second plunger  22  is constituted by the connection portion  31 , the spring receiving portion  32 , and a contact piece  33 . 
     The connection portion  31  is constituted by a connecting rod portion  31 A and a flange portion  31 B. The connecting rod portion  31 A is a portion where the first plunger  21  and the second plunger  22  are overlapped with each other when they are connected to each other. The connecting rod portion  31 A is formed in a plate shape with a width larger than the connecting rod portion  26 A of the first plunger  21 . The sectional dimension of this connecting rod portion  31 A is set such that the eight corner portions located outside in a state overlapped with the connecting rod portion  26 A of the above-mentioned connection portion  26  are positioned at apexes of the octagon. That is, the sectional dimension of the connecting rod portion  31 A is set such that the positions of the eight corner portions in contact with the circumscribed circle in the sectional shape in a state in which the connecting rod portion  26 A of the first plunger  21  and the connecting rod portion  31 A of the second plunger  22  are overlapped with each other are located at the apex positions of the octagon. The connecting rod portion  31 A is formed by extending its distal end to the vicinity of the spring receiving portion  27  of the first plunger  21 . As a result, a defect that the connecting rod portion  26 A of the connection portion  26  in the first plunger  21  is short and narrow is compensated and a contact area is enlarged. 
     The flange portion  31 B is a portion for preventing drop-off of the plungers  21  and  22  along with the flange portion  26 B of the first plunger  21 . A width dimension of the flange portion  31 B is formed substantially equal to or slightly larger than the outer diameter of the cylindrical support member  23 . 
     The spring receiving portion  32  is formed with a dimension larger than the outer diameter of the compression coil spring  24  and is brought into contact with an end portion of the compression coil spring  24 . As a result, the compression coil spring  24  is brought into contact with the spring receiving portion  27  of the first plunger  21  and the spring receiving portion  32  of the second plunger  22 , respectively, and urges the first plunger  21  and the second plunger  22  in a direction to be separated from each other. At the same time, the connection portions  26  and  31  of the plungers  21  and  22  are supported by the cylindrical support member  23  so that they will not drop off the other. As a result, since each of the plungers  21  and  22  is supported by the cylindrical support member  23  and urged by the compression coil spring  24 , the contact  20  is compressed by a pressure from the outside and if the pressure from the outside ceases, the contact  20  returns to the original length. 
     A contact piece  33  is a member to be brought into contact with the member B 2  for electrical connection. The contact piece  33  has its distal end constituted by a plurality of (two in this embodiment) projections. 
     An opening portion  35  is provided between the contact piece  33  and the spring receiving portion  32 . This opening portion  35  is used to insert a support rod  36  to be positioned and supported. The opening portion  35  is formed by being notched in a circular shape between the two contact pieces  33 . The support rod  36  is inserted through the opening portion  35 , and the plurality of contacts  20  are integrally held. The support rod  36  is a member for integrally holding the plurality of contacts  20  by being inserted through each of the openings  35  of the plurality of contacts  20 . The support rod  36  is formed in a shape of a circular rod. The support rod  36  is formed by an insulating elastic member such as silicon rubber and mounted on a bottom portion of a housing  38 . As a result, the plurality of contacts  20  inserted into the housing  38 , respectively, are supported in a state insulated to each other. 
     The cylindrical support member  23  is a member for slidably and elastically supporting the connection portion  31  of the second plunger  22  and the connection portions  26  of the two first plungers  21  located on both faces of the connection portion  31  of the second plunger  22  in an overlapped and electrically connected state. This cylindrical support member  23  is specifically constituted by a coil spring, similarly to the first embodiment, which varies its diameter elastically and is elastically brought into contact with the connection portions  26  and  31  of the plungers  21  and  22  so as to slidably support them. The coil spring is constituted by a tight spring. An inner diameter of the cylindrical support member  23  is, similarly to the first embodiment, set such that a lateral sectional area is slightly smaller than a diameter of a circumscribed circle circumscribed by each corner to become an apex position of the octagon in a state in which the connecting rod portions  26 A and  31 A are overlapped with each other. As a result, the cylindrical support member  23  allows mutual sliding of the connecting rod portions  26 A and  31 A in a close contact state, prevents drop-off, and reliably maintains electric connection by elastically supporting the connecting rod portions  26 A and  31 A with some tightening force. 
     The compression coil spring  24  is a spring for urging the plungers  21  and  22  in a direction to be separated from each other similarly to the first embodiment. 
     The contact  20  constituted as above is used as follows. 
     Since an entire operation of the contact  20  of this embodiment is similar to the contact  10  of the first embodiment, a difference from the first embodiment will be mainly described. The contact  20  is supported by the support rod  36 . Specifically, by inserting the support rod  36  through the opening portion  35  in the contact  20 , the plurality of contacts  20  are integrally supported and housed in the housing  38 . In this state, the member B 1  such as a bump electrode of a specimen  39  is located on an upper side of the contact  20 , and the member B 2  such as an electrode pad of a wiring substrate on a tester side is located on a lower side of the contact  20 . 
     If each of the members B 1  and B 2  is brought into contact with each of the contacts  20  and pressed thereon, the contacts  20  operate as follows. 
     If the contact piece  28  of the first plunger  21  is brought into contact with the member B 1  and pressed thereon, the first plunger  21  is pushed toward the second plunger  22  side by the action. As a result, the connecting rod portion  26 A of the first plunger  21  is displaced from the connecting rod portion  31 A of the second plunger  22  in a state supported by the cylindrical support member  23 , and the compression coil spring  24  received by the spring receiving portion  27  is compressed. By means of a repulsion force of the compression coil spring  24 , each of the contact pieces  28  and  33  is pressed onto and bitten into each of the members B 1  and B 2 . 
     As a result, similarly to the first embodiment, an electrically connected state between each of the connecting rod portions  26 A and  31 A and the compression coil spring  24  is reliably maintained. 
     Moreover, in this embodiment, since the two first plungers  21  slide independently, even if heights of contact portions of the two first plungers  21  are different such as in a case in which the member B 1  is deformed, the two first plungers  21  follow the shape with displacement and touch with the respective contact pieces  28 . Here, the member B 1  is in a semispherical shape, but even if the member B 1  is in a distorted spherical shape or any other shapes and even if the contact positions of the two first plungers  21  are displaced, the shape is followed up with displacement and touched by the respective contact pieces  28 . 
     As a result, the members B 1  and B 2  are electrically connected by the contact  20  reliably. In this state, an electric signal or the like is transmitted between the members B 1  and B 2  through the contact  20 . 
     When the contact piece  28  of the first plunger  21  is separated from the member B 1  upon the end of an inspection or the like, each of the plungers  21  and  22  is supported at the flange portions  26 B and  31 B by the both end portions of the cylindrical support member  23 , and drop-off is prevented. In the subsequent use, too, similarly to the above, the contact pieces  28  of the two first plungers  21  are brought into contact with the member B 1 , the cylindrical support member  23  allows the displacement of the connecting rod portions  26 A and  31 A and electrically connects them, and an inspection signal or the like is transmitted. 
     As mentioned above, the same effect as the first embodiment is exerted. Moreover, in this embodiment, since the first plunger  21  and the second plunger  22  are formed simply by punching a plate material, its manufacture is easy and inexpensive, and a manufacturing cost of the contact can be reduced. 
     Also, in this embodiment, since independent sliding of the two first plungers  21  is allowed, each of the first plungers  21  is individually displaced independently according to the shape of the member B 1  and is reliably brought into contact. 
     As mentioned above, by means of contact of two first plungers  21  with the member B 1  and individual and independent displacement and reliable contact of each of the first plungers  21  according to the shape of the member B 1 , reliable contact at a plurality of points is ensured regardless of a situation of deformation, damage and the like of the member B 1 , and electrical contact is drastically improved. 
     Fourth Embodiment 
     Subsequently, a contact according to the fourth embodiment of the present invention will be described. The contact of this embodiment is a Kelvin contact constituted by providing two second plungers on the contact  20  of the third embodiment. An entire configuration of the contact of this embodiment is substantially similar to the contact  20  of the third embodiment. That is, a contact  41  of this embodiment is, as shown in  FIGS. 21 and 22 , different in a second plunger  42  and a cylindrical support member  43 . The other members are the same. Therefore, the same reference numerals are given to the same members, and the description will be omitted. 
     In the contact  41  of this embodiment, two second plungers  42  are provided similarly to the first plungers  21 . The two second plungers  42  have the same shape, and an insulator  44  is provided between each of the second plungers  42 . The two second plungers  42  are integrally connected while sandwiching the insulator  44 . The insulator  44  may be a plate-shaped member that can insulate between the two second plungers  42 . By means of the insulator  44 , the two second plungers  42  and the two first plungers  21  brought into contact with each of the second plungers  42  are insulated, respectively. 
     The cylindrical support member  43  is a tight coil spring for integrally surrounding and supporting the two first plungers  21 , the two second plungers  42 , and the insulator  44  in an overlapped state. The entire configuration of the cylindrical support member  43  is similar to that of the cylindrical support member  23  in the third embodiment, but in this embodiment, the cylindrical support member  43  is constituted by an insulating material. That is, while the cylindrical support member  23  of the third embodiment is constituted by a conductive material, the cylindrical support member  43  of this embodiment is constituted by an insulating material. Since it is only necessary for the cylindrical support member  43  to have insulation, a spring material made of metal may be applied with insulating coating. The compression coil spring  24  is also constituted by an insulating material or applied with insulating coating. 
     As a result, one of the first plungers  21  and one of the second plungers  42  are electrically connected, while the other of the first plungers  21  and the other of the second plungers  42  are electrically connected, and a signal is transmitted through two systems. 
     The contact constituted as above acts similarly to the third embodiment. Since the two second plungers  42  are integrally joined while sandwiching the insulator  44 , the plunger can be considered to be substantially the same member as the second plunger  22  in the third embodiment except that the thicknesses are slightly different and acts similarly to the third embodiment. 
     As a result, similarly to the third embodiment, reliable contact at a plurality of points can be ensured regardless of a situation such as deformation, damage and the like of the member B 1 , and electrical contact is drastically improved. In this state, Kelvin contact can be reliably performed. 
     (E) Fifth Embodiment 
     Subsequently, a contact according to the fifth embodiment will be described.  FIG. 23  is a partially exploded side view illustrating the contact according to this embodiment, and  FIG. 24  is a planar sectional view of  FIG. 23 . 
     The contact of this embodiment is obtained by improving the sectional shape of the connecting rod portion  16 A of the connection portion  16  in the first embodiment. Since the contact of this embodiment is similar to the first embodiment except the connecting rod portion  46 A of the connection portion  46 , the same reference numerals are given to the same members, and the description will be omitted. 
     In this embodiment, the connecting rod portion  46 A of the connection portion  46  is formed in an arc shape along the inner diameter of the cylindrical support member  13 . 
     The connecting rod portion  46 A of the connection portion  46  is formed in a plate shape and both sides thereof are formed in an arc shape along the inner diameter of the cylindrical support member  13 . The both sides of the connecting rod portion  16 A in the first embodiment are tapered, but an arc shape is used instead of taper in this embodiment. 
     As a result, the two connecting rod portions  46 A of the connection portions  46  overlapped with each other are brought into contact with the inner diameter of the cylindrical support member  13  through a long line. 
     If the section is a hexagon in a state in which the two connecting rod portions  16 A are overlapped with each other as in the first embodiment, they are in contact with the inner diameter of the cylindrical support member  13  at six points, but in this embodiment, they are in contact through a long line. 
     As a result, the same actions and effects as those of the first embodiment are exerted, and conductivity between the connecting rod portion  16 A and the cylindrical support member  13  can be further improved. 
     (F) Sixth Embodiment 
     Subsequently, an example of an electrical connecting apparatus using the contact of each of the above embodiments will be described.  FIG. 25  is a plan view illustrating the electrical connecting apparatus, and  FIG. 26  is a sectional view illustrating the electrical connecting apparatus. 
     An electrical connecting apparatus  50  of this embodiment is used in a current test of a semiconductor device such as an integrated circuit as a specimen. A specimen  51  is formed in a plate shape, and a plurality of bump electrodes  51 A are provided on one of its faces in a matrix state. The bump electrode  51 A may be provided in a single row, plural rows or other arrangements. 
     The electrical connecting apparatus  50  is provided with a substrate  52 , a housing  53  overlapped on the substrate  52 , a frame  54  overlapped on the housing  53 , and a plurality of contacts  55  arranged in the housing  53 . As the contact  55 , the contact of each of the above embodiments is used. 
     As a result, the bump electrode  51 A of the specimen  51  is brought into contact with the contact  55  and acts similarly to each of the above embodiments and exerts the same effect. 
     Also, electrical connecting apparatuses in other configurations can be used as long as it is an electrical connecting apparatus that can use the contact of each of the above embodiments in a mode similar to the contact  55  of this embodiment. 
     (G) Variations 
     In the first embodiment, it is set such that the plungers  11  and  12  have a hexagonal sectional shape when base end sides thereof are overlapped with each other, but the sectional shape may be other polygons such as an octagon or a regular polygon. Also, it may be formed in a circular shape. Particularly, if the sectional shape is formed in a circular shape, since they are in contact with the cylindrical support member  13  through a large number of lines, and electrical contact between the cylindrical support member  13  and the base end sides of the plungers  11  and  12  is further improved. 
     In the second embodiment, the two first plungers  21  are provided, and the second plunger  22  is sandwiched by the first plungers  21  from both sides, but it may be a reversed configuration. It may be so configured that the two second plungers  22  are provided according to a use mode in which the electric contact on the second plunger  22  side should be improved or the like, and the first plunger  21  is sandwiched by the second plungers  22  from the both sides. 
     The contact of the present invention can be used in an apparatus in general to be touched by an electrode provided in a wiring substrate, a semiconductor integrated circuit and the like. 
     The electrical connecting apparatus can be applied to all the apparatuses that can use the contact of the present invention.