Patent Publication Number: US-2010123476-A1

Title: Conductive contact

Description:
TECHNICAL FIELD 
     The present invention relates to a conductive contact that performs input and output of a signal in an electrical characteristics test on a semiconductor integrated circuit or the like. 
     BACKGROUND ART 
     In an electrical characteristics test for a semiconductor integrated circuit such as an IC chip, a conductive contact unit is used that houses a plurality of conductive contacts at predetermined positions corresponding to an arrangement pattern of external connection electrodes included in the semiconductor integrated circuit. In such a conductive contact unit, both end portions of the conductive contact are brought into contact with a spherical electrode of the semiconductor integrated circuit and an electrode on a circuit substrate for the test, respectively, to establish an electrical connection at the test (see Patent Document 1, for example). 
     Patent Document 1: Japanese Patent Application Laid-open No. 2002-107377 
     DISCLOSURE OF INVENTION 
     Problem to be Solved by the Invention 
     In recent years, a demand is growing for a semiconductor capable of coping with a high frequency of 1 GHz or more. For performing the electrical characteristics test on such a semiconductor, the inductance or the resistance of the conductive contact needs to be lowered. In view of this, it is preferable that the diameter of the conductive contact is made large and the length of the conductive contact is shortened. Although machining the conductive contact having a large diameter is relatively easy, machining the conductive contact, of which entire length is made short, is difficult. In the case of the conductive contact having a configuration in which two plungers positioned at both ends are coupled with a spring member, for example, the pitch of the winding of the spring member is sometimes changed in the middle and two plungers are brought into contact with each other at a tightly wound portion in order to ensure desired spring characteristics and realize an effective conductive path. In order to shorten the entire length of the conductive contact, the distance between the two plungers needs to be shortened by shortening the tightly wound portion of the spring member, so that the stroke required for the conductive contact may not be ensured. 
     The present invention has been made in view of the above, and it is an object of the present invention to provide a conductive contact that is capable of performing transmission and reception of a signal with high frequency of 1 GHz of more and can be machined easily. 
     Means for Solving Problem 
     To solve the problem described above and achieve the object, a conductive contact according to the present invention includes a first plunger which is formed approximately in a needle-shape and is formed of conductive material and of which tip portion has an axisymmetric shape; a second plunger which is formed approximately in a needle-shape and is formed of conductive material, of which tip portion is oriented in a direction opposite to the tip portion of the first plunger, and of which tip portion has an axisymmetric shape with respect to an axis line same as that of the tip portion of the first plunger; and a spring member which is formed of conductive material, of which one end is in contact with the first plunger and another end is in contact with the second plunger, and which is extendable in a longitudinal direction, wherein a base end portion of the first plunger and a base end portion of the second plunger are slidably in contact with each other. 
     In the conductive contact according to the present invention as set forth in the invention described above, the base end portion of the first plunger and the base end portion of the second plunger have same cross sectional shape. 
     In the conductive contact according to the present invention as set forth in the invention described above, the base end portion of the first plunger and the base end portion of the second plunger have a shape engagable with each other. 
     In the conductive contact according to the present invention as set forth in the invention described above, the first plunger and the second plunger have same shape. 
     In the conductive contact according to the present invention as set forth in the invention described above, the spring member is such that a pitch of a winding is same except for end portions at which the first plunger and the second plunger are attached. 
     In the conductive contact according to the present invention as set forth in the invention described above, the spring member is such that a pitch of a winding changes along the longitudinal direction and a portion positioned near an outer periphery of a position at which the base end portion of the first plunger and the base end portion of the second plunger are in contact with each other in a state where the spring member is not stroked is tightly wound. 
     In the conductive contact according to the present invention as set forth in the invention described above, the spring member is such that a diameter of a winding changes along the longitudinal direction and the diameter of the winding is maximum at a portion positioned near an outer periphery of a position at which the base end portion of the first plunger and the base end portion of the second plunger are in contact with each other in a state where the spring member is not stroked. 
     EFFECT OF THE INVENTION 
     According to the present invention, it is possible to provide a conductive contact which includes the first plunger which is formed approximately in a needle-shape and is formed of conductive material and of which tip portion has an axisymmetric shape, the second plunger which is formed approximately in a needle-shape and is formed of conductive material, of which tip portion is oriented in a direction opposite to the tip portion of the first plunger, and of which tip portion has an axisymmetric shape with respect to the axis line same as that of the tip portion of the first plunger, and a spring member which is formed of conductive material, of which one end is in contact with the first plunger and the other end is in contact with the second plunger, and which is extendable in the longitudinal direction. The conductive contact is capable of transmitting and receiving a signal with high frequency of 1 GHz or more by bringing the base end portion of the first plunger into slidably contact with the base end portion of the second plunger. The conductive contact can be easily machined. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration of a conductive contact according to a first embodiment of the present invention. 
         FIG. 2  is a diagram illustrating a contact form of a base end portion of a first plunger and a base end portion of a second plunger. 
         FIG. 3  is a diagram illustrating a configuration of a relevant portion of a conductive contact holder that houses the conductive contact according to the first embodiment of the present invention. 
         FIG. 4  is a diagram explaining an effect caused by the conductive contact according to the first embodiment of the present invention. 
         FIG. 5  is a diagram illustrating a configuration of a conductive contact according to a first modified example of the first embodiment of the present invention. 
         FIG. 6  is a diagram illustrating a contact form of a base end portion of a first plunger and a base end portion of a second plunger of a conductive contact according to a second modified example of the first embodiment of the present invention. 
         FIG. 7  is a diagram illustrating a contact form of a base end portion of a first plunger and a base end portion of a second plunger of a conductive contact according to a third modified example of the first embodiment of the present invention. 
         FIG. 8  is a diagram illustrating a configuration of a conductive contact according to a second embodiment of the present invention. 
         FIG. 9  is a diagram illustrating a configuration of a conductive contact according to a modified example of the second embodiment of the present invention. 
         FIG. 10  is a diagram illustrating a configuration of a conductive contact according to another embodiment of the present invention. 
         FIG. 11  is a diagram illustrating a configuration of a conductive contact according to still another embodiment of the present invention. 
     
    
    
     EXPLANATIONS OF LETTERS OR NUMERALS 
     
         
         
           
               1 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8  conductive contact conductive contact holder 
               11 ,  31 ,  51 ,  61  first plunger 
               12 ,  32 ,  52 ,  62  second plunger 
               11   a ,  12   a ,  31   a ,  32   a ,  51   a ,  52   a ,  61   a ,  62   a  tip portion 
               11   b ,  12   b ,  31   b ,  32   b ,  51   b ,  52   b ,  61   b ,  62   b  flange portion 
               11   c ,  12   c ,  31   c ,  32   c ,  51   c ,  52   c ,  61   c ,  62   c  boss portion 
               11   d ,  11 - 2   d ,  11 - 3   d ,  12   d ,  12 - 2   d ,  12 - 3   d ,  31   d ,  32   d ,  51   d ,  52   d ,  61   d ,  62   d  base end portion 
               13 ,  33 ,  71 ,  81  spring member 
               21  first substrate 
               22  second substrate 
               33   a ,  81   a ,  81   b  loosely wound portion 
               33   b ,  81   c  tightly wound portion 
               100  circuit substrate 
               101 ,  201  electrode 
               200  test object 
               211 ,  221  hole portion 
               211   a ,  221   a  small diameter hole 
               211   b ,  221   b  large diameter hole 
           
         
       
    
     BEST MODE(S) FOR CARRYING OUT THE INVENTION 
     Preferred embodiments (hereinafter, “embodiments”) of the present invention will be described below with reference to the accompanying drawings. It should be noted that the drawings are schematic and a relation between the thickness and the width of each portion, a ratio of the thicknesses of the respective portions, and the like may be different from realistic ones. It goes without saying that the drawings may depict some portion as having different relations and ratios of dimensions. 
     First Embodiment 
       FIG. 1  is a diagram illustrating a configuration of a conductive contact according to a first embodiment of the present invention. A conductive contact  1  shown in  FIG. 1  is formed of conductive material, and includes a first plunger  11  having a sharp tip end, a second plunger  12  having a crown-shaped tip that projects in a direction opposite to the first plunger  11 , and a spring member  13  that is in contact with the first plunger  11  at one end and with the second plunger  12  at the other end and is extensible in a longitudinal direction. 
     The first plunger  11  includes a tip portion  11   a  having the sharp tip end, a flange portion  11   b  having a diameter larger than the diameter of the tip portion  11   a , a boss portion  11   c  which projects in an opposite direction of the tip portion  11   a  via the flange portion lib, which has a cylindrical shape with a diameter that is smaller than the diameter of the flange portion  11   b  and is slightly larger than the inner diameter of the spring member  13 , and onto which the end portion of the spring member  13  is press fitted, and a base end portion  11   d  that extends on the opposite side of the flange portion  11   b  from the boss portion  11   c . The tip portion  11   a , the flange portion  11   b , and the boss portion  11   c  have an axisymmetric shape with respect to the central axis parallel to the longitudinal direction. The base end portion  11   d  has a shape that is formed by cutting out a part from a cylinder having a diameter smaller than the diameter of the boss portion  11   c  and the inner diameter of the spring member  13 . The cut-out part includes an end portion of the base end portion  11   d  on a side that is not in contact with the boss portion  11   c . The cut-out part is cut along the longitudinal direction and has a semi-cylindrical shape. 
     The second plunger  12  includes a tip portion  12   a  having a crown shape, a flange portion  12   b  having a diameter larger than the diameter of the tip portion  12   a , a boss portion  12   c  which projects in an opposite direction of the tip portion  12   a  via the flange portion  12   b , which has a cylindrical shape with a diameter that is smaller than the diameter of the flange portion  12   b  and is slightly larger than the inner diameter of the spring member  13 , and onto which the end portion of the spring member  13  is press fitted, and a base end portion  12   d  that extends on the opposite side of the flange portion  12   b  from the boss portion  12   c . The tip portion  12   a , the flange portion  12   b , and the boss portion  12   c  have an axisymmetric shape with respect to the central axis parallel to the longitudinal direction. The base end portion  12   d  has a shape same as the base end portion  11   d  of the first plunger  11 . 
     The base end portion  11   d  of the first plunger  11  and the base end portion  12   d  of the second plunger  12  are slidably in contact with each other near each end portion thereof.  FIG. 2  is a diagram illustrating a contact form of the base end portions  11   d  and  12   d  and is a diagram corresponding to a cross section taken along line A-A in  FIG. 1 . The cross sections of parts of the base end portions  11   d  and  12   d  that are in contact with each other have the same semi-circular shape, and the side surfaces that pass the center of each semicircle and extend in the longitudinal direction are in contact with each other. The first plunger  11  and the second plunger  12  are slidably in contact with each other as described above, so that a conductive path directly reaching the base end portion  12   d  from the base end portion  11   d  can be ensured. 
     The first plunger  11  and the second plunger  12  are formed, for example, by lathe machining. This is applicable to the following embodiments and the others. The length of the base end portion  11   d  of the first plunger  11  and the length of the base end portion  12   d  of the second plunger  12  can be appropriately changed and can be different from each other. 
     The spring member  13  is a coil spring having a uniform diameter, and both end portions thereof are press fitted onto the boss portion  11   c  of the first plunger  11  and the boss portion  12   c  of the second plunger  12 , respectively. The pitch of the winding of the spring member  13  is uniform except for the both end portions that are press fitted onto the first plunger  11  and the second plunger  12 . The axis line of the spring member  13  coincides with the axis line of part of the first plunger  11  excluding the base end portion  11   d  and the axis line of part of the second plunger  12  excluding the base end portion  12   d.    
     In the conductive contact  1  having the above configuration, the parts of the base end portion  11   d  and the base end portion  12   d  that are in contact with each other do not separate even when a load is applied to the conductive contact  1  and the spring member  13  is stroked while meandering. Consequently, reliable slide friction can be ensured. 
       FIG. 3  is a diagram illustrating a configuration of a relevant portion of a conductive contact holder that houses the conductive contacts  1  and a configuration of contact target bodies that are in contact with the both end portions of the conductive contacts  1 . A conductive contact holder  2  shown in  FIG. 3  is formed by stacking a first substrate  21  and a second substrate  22  in a plate thickness direction. In the first substrate  21 , hole portions  211  in which a plurality of the conductive contacts  1  is individually housed are formed. The hole portion  211  has a stepped-hole shape that includes a small diameter portion  211   a  having a diameter slightly larger than the diameter of the tip portion  11   a  of the first plunger  11  and a large diameter portion  211   b  having a diameter slightly larger than the diameter of the flange portion  11   b.    
     In the second substrate  22 , hole portions  221  in which a plurality of the conductive contacts  1  is individually housed are formed. The hole portion  221  has a stepped-hole shape that includes a small diameter portion  221   a  having a diameter slightly larger than the diameter of the tip portion  12   a  of the second plunger  12  and a large diameter portion  221   b  having a diameter slightly larger than the diameter of the flange portion  12   b . The diameter of the large diameter portion  221   b  is equal to the diameter of the large diameter portion  211   b.    
     When the conductive contacts  1  are housed and the first substrate  21  and the second substrate  22  are stacked, the hole portion  211  and the hole portion  221  that correspond to each other communicate in the axis direction. 
     The tip portion  11   a  of the first plunger  11  of the conductive contact  1  that the conductive contact holder  2  houses is in contact with an electrode  101  provided on a circuit substrate  100  that outputs a signal for a test. In contrast, the tip portion  12   a  of the second plunger  12  of the conductive contact  1  that the conductive contact holder  2  houses is in contact with an electrode  201  of a test object  200  such as a semiconductor integrated circuit. In the case shown in  FIG. 3 , the surface of the electrode  101  is flat, whereas the surface of the electrode  201  is spherical. The tip portion  11   a  of the first plunger  11  forms a sharp tip end, whereas the tip portion  12   a  of the second plunger  12  forms a crown shape, to ensure a suitable contact state in accordance with the shape of the electrodes  101  and  201 . In this manner, the shape of the tip portion of each plunger can be defined in accordance with the shape of the electrode that is in contact therewith. 
     The first substrate  21  and the second substrate  22  that construct the conductive contact holder  2  are formed by using insulating material such as resin, machinable ceramic, and silicone. The hole portion  211  and the hole portion  221  formed in the first substrate  21  and the second substrate  22 , respectively, are formed by performing drilling, etching, or punching, or performing a process using a laser, an electron beam, an ion beam, a wire electrical discharge, or the like. 
       FIG. 4  is a diagram explaining an effect of the conductive contact  1  according to the first embodiment of the present invention. A conductive contact  3  shown in  FIG. 4  is a conventional conductive contact. The conductive contact  3  includes a first plunger  31  having a sharp tip end, a second plunger  32  having a crown-shaped tip that projects in a direction opposite to the first plunger  31 , and a spring member  33  that couples the first plunger  31  and the second plunger  32 . 
     The first plunger  31  includes a tip portion  31   a , a flange portion  31   b  having a diameter larger than the diameter of the tip portion  31   a , a boss portion  31   c  which projects in an opposite direction of the tip portion  31   a  via the flange portion  31   b , which has a cylindrical shape with a diameter that is smaller than the diameter of the flange portion  31   b  and is slightly larger than the inner diameter of the spring member  33 , and onto which the end portion of the spring member  33  is press fitted, and a base end portion  31   d  that has a cylindrical shape with a diameter that is smaller than the diameter of the boss portion  31   c  and is smaller than the inner diameter of the spring member  33 . The second plunger  32  includes a tip portion  32   a  having a crown shape, a flange portion  32   b  having a diameter larger than the diameter of the tip portion  32   a , a boss portion  32   c  which projects in an opposite direction of the tip portion  32   a  via the flange portion  32   b , which has a cylindrical shape with a diameter that is smaller than the diameter of the flange portion  32   b  and is slightly larger than the inner diameter of the spring member  33 , and onto which the end portion of the spring member  33  is press fitted, and a base end portion  32   d  that has a cylindrical shape with a diameter that is smaller than the diameter of the boss portion  32   c  and is smaller than the inner diameter of the spring member  33 . The first plunger  31  side of the spring member  33  is a loosely wound portion  33   a , while the second plunger  32  side thereof is a tightly wound portion  33   b . The end portion of the loosely wound portion  33   a  is press fitted onto the boss portion  31   c  of the first plunger  31 , while the end portion of the tightly wound portion  33   b  is press fitted onto the boss portion  32   c  of the second plunger  32 . The conductive contact  3  is configured so that the base end portion  31   d  is in contact with the tightly wound portion  33   b , and the shortest conductive path in an order of the first plunger  31 , the tightly wound portion  33   b , and the second plunger  32  is formed. 
     Contrary to the conductive contact  3  having the above configuration, in the conductive contact  1  according to the first embodiment, the base end portion  11   d  of the first plunger  11  and the base end portion  12   d  of the second plunger  12  are slidably in contact with each other, so that the conductive path directly reaching the base end portion  12   d  from the base end portion  11   d  without via the spring member  13  can be ensured. Thus, there is no need to provide a tightly wound portion in the spring member. 
     In the case shown in  FIG. 4 , in order to cause the conductive contact  1  and the conductive contact  3  to have the same spring characteristics, the length of the loosely wound portion  33   a  and the length of the spring member  13  are made equal to LP, and the pitch of the winding of the loosely wound portion  33   a  and the pitch of the winding of the spring member  13  are made equal to ΔP. In this case, in the conductive contact  1 , the tightly-wound portion does not need to be provided as described above, so that the entire length L 1  thereof can be made shorter than the entire length L 3  of the conductive contact  3  (L 1 -L 3 =ΔL). Consequently, the inductance or the resistance of the conductive contact can be reduced compared with the conventional type, enabling to realize excellent high frequency characteristics. 
     According to the first embodiment of the present invention described above, it is possible to provide the conductive contact which includes the first plunger which is formed approximately in a needle-shape and is formed of conductive material and of which tip portion has an axisymmetric shape, the second plunger which is formed approximately in a needle-shape and is formed of conductive material, of which tip portion is oriented in a direction opposite to the tip portion of the first plunger, and of which tip portion has an axisymmetric shape with respect to the axis line same as that of the tip portion of the first plunger, and a spring member which is formed of conductive material, of which one end is in contact with the first plunger and the other end is in contact with the second plunger, and which is extendable in the longitudinal direction. The conductive contact is capable of transmitting and receiving a signal with high frequency of 1 GHz or more by bringing the base end portion of the first plunger into slidably contact with the base end portion of the second plunger, and the conductive contact can be easily machined. 
     As a first modified example of the first embodiment, as shown in  FIG. 5 , it is possible to configure a conductive contact  4  in which the second plunger has the same shape as the first plunger. In this case, the base end portions  11   d  of the respective plungers are slidably in contact with each other as a matter of course. 
     Moreover, as a second modified example of the first embodiment, it is possible to form cross sections (the cross section corresponding to  FIG. 2 ) of the contact portions of the base end portions of the two plungers that are vertical to the longitudinal direction into an asymmetrical shape. For example, as shown in  FIG. 6 , a cross-section area of a base end portion  11 - 2   d  of the first plunger can be made smaller than a cross-section area of a base end portion  12 - 2   d  of the second plunger, and the cross section combining the two base end portions  11 - 2   d  and  12 - 2   d  can have a circular shape. 
     Furthermore, as a third modified example of the first embodiment, as shown in  FIG. 7 , it is possible to configure such that a cross section of a contact portion of a base end portion  11 - 3   d  of the first plunger and a base end portion  12 - 3   d  of the second plunger has a clearance. 
     Second Embodiment 
       FIG. 8  is a diagram illustrating a configuration of a conductive contact according to the second embodiment of the present invention. A conductive contact  5  shown in  FIG. 8  includes a first plunger  51 , a second plunger  52 , and the spring member  13  that is in contact with the first plunger  51  at one end and with the second plunger  52  at the other end and is extensible in the longitudinal direction. 
     The first plunger  51  includes a tip portion  51   a  having a sharp tip end, a flange portion  51   b  having a diameter larger than the diameter of the tip portion  51   a , a boss portion  51   c  that projects in an opposite direction of the tip portion  51   a  via the flange portion  51   b , has a cylindrical shape with a diameter that is smaller than the diameter of the flange portion  51   b  and is slightly smaller than the inner diameter of the spring member  13 , and suppresses the movement of the end portion of the spring member  13  in a radial direction, and a base end portion  51   d  that extends on the opposite side of the flange portion  51   b  from the boss portion  51   c . The base end portion  51   d  is configured such that the end portion on the side that is in contact with the boss portion  51   c  has a cylindrical shape with a diameter smaller than the diameter of the boss portion  51   c  and the inner diameter of the spring member  13  and the end portion on the side that is not in contact with the boss portion  51   c  has a hook shape. The middle portion of the base end portion  51   d  has a shape that is formed by cutting out part of a cylinder along the longitudinal direction. The cylinder is formed by the end portion on a side that is in contact with the boss portion  51   c.    
     The second plunger  52  includes a tip portion  52   a  having a crown shape, a flange portion  52   b  having a diameter larger than the diameter of the tip portion  52   a , a boss portion  52   c  that projects in an opposite direction of the tip portion  52   a  via the flange portion  52   b , has a cylindrical shape with a diameter that is smaller than the diameter of the flange portion  52   b  and is slightly smaller than the inner diameter of the spring member  13 , and suppresses the movement of the end portion of the spring member  13  in the radial direction, and a base end portion  52   d  that extends on the opposite side of the flange portion  52   b  from the boss portion  52   c . The base end portion  52   d  has the same shape as the base end portion  51   d  of the first plunger  51 , and the end portion of the base end portion  52   d  having a hook shape can be engaged with the end portion of the base end portion  51   d  having a hook shape. 
     The base end portion  51   d  of the first plunger  51  and the base end portion  52   d  of the second plunger  52  are configured to be engagable with each other, so that an initial load can be applied in a state where the conductive contact  5  is assembled. Therefore, the both end portions of the spring member  13  do not need to be pressed and fixed to the first plunger  51  and the second plunger  52 , so that the assembling work of a probe can be made easier. Moreover, regarding the hole portion in the conductive contact holder, there is no need to form both ends thereof into a stepped-hole shape and apply an initial load, so that warping of the conductive contact holder due to the load can be eliminated. Furthermore, if only the lower end of the hole portion is formed into a stepped-hole shape to prevent the conductive contact  5  from coming off, the conductive contact holder can be formed from one substrate, thus enabling to reduce the number of components and man-hours and realize a low cost. Moreover, when the conductive contact  5  is inserted into the conductive contact holder having the similar configuration to that shown in  FIG. 3  and two substrates are combined, a load of the conductive contact  5  is not applied to each substrate, so that assembling becomes easy. 
     The shape of the base end portions  51   d  and  52   d  shown in  FIG. 8  is just an example. For example, as a conductive contact  6  shown in  FIG. 9 , the shape can be such that a base end portion  61   d  of a first plunger  61  and a base end portion  62   d  of a second plunger  62  are engaged with each other and are slidably in contact with each other in the longitudinal direction. In the conductive contact  6 , a tip portion  61   a , a flange portion  61   b , and a boss portion  61   c  of the first plunger  61  have the similar shape to the tip portion  51   a , the flange portion  51   b , and the boss portion  51   c  of the first plunger  51  of the conductive contact  5 , respectively. A tip portion  62   a , a flange portion  62   b , and a boss portion  62   c  of the second plunger  62  have the similar shape to the tip portion  52   a , the flange portion  52   b , and the boss portion  52   c  of the second plunger  52  of the conductive contact  5 , respectively. 
     According to the second embodiment of the present invention described above, it is possible to provide the conductive contact which includes the first plunger which is formed approximately in a needle-shape and is formed of conductive material and of which tip portion has an axisymmetric shape, the second plunger which is formed approximately in a needle-shape and is formed of conductive material, of which tip portion is oriented in a direction opposite to the tip portion of the first plunger, and of which tip portion has an axisymmetric shape with respect to the axis line same as that of the tip portion of the first plunger, and a spring member which is formed of conductive material, of which one end is in contact with the first plunger and the other end is in contact with the second plunger, and which is extendable in the longitudinal direction. The conductive contact is capable of transmitting and receiving a signal with high frequency of 1 GHz or more by bringing the base end portion of the first plunger into slidably contact with the base end portion of the second plunger, and the conductive contact can be easily machined. 
     Moreover, according to the second embodiment, the base end portion of the first plunger and the base end portion of the second plunger have a shape engagable with each other, so that an initial load can be applied to the conductive contact by the engagement. Consequently, the both end portions of the spring member do not need to be pressed and fixed to the first plunger and the second plunger, respectively, so that manufacturing of the conductive contact becomes easy. Moreover, the conductive contact holder can be formed from one substrate, and thus the configuration of the hole portion in which the conductive contact is housed can be made simple, enabling to make manufacturing easy. Consequently, the manufacturing cost for the conductive contact and the conductive contact holder can be reduced. 
     Furthermore, according to the second embodiment, because the conductive contact holder needs not apply a load on the conductive contact, warping of the conductive contact holder due to a reaction force of the spring member does not occur, so that the movement of the conductive contact can be made smooth and the positional accuracy of the tip of the conductive contact can be improved. In addition, assembling of the conductive contact holder in which the conductive contact is housed becomes easy. 
     In the second embodiment, the configuration can be such that the diameter of the boss portion of each plunger is made slightly larger than the inner diameter of the spring member and the end portions of the spring member are press fitted onto the boss portions in the similar manner to the above first embodiment. 
     Other Embodiments 
     The first and second embodiments are described in detail as preferred embodiments of the present invention; however, the present invention should not be limited to these two embodiments. For example, as described below, regarding the spring member, the shape thereof can be changed in accordance with various conditions such as the material of the first plunger and the second plunger, the contact area of the base end portions of both plungers, and the entire length of the contact portion. 
       FIG. 10  is a diagram illustrating a configuration of a conductive contact according to another embodiment of the present invention. A conductive contact  7  shown in  FIG. 10  includes the first plunger  11 , the second plunger  12 , and a spring member  71  that couples the first plunger  11  and the second plunger  12 . The spring member  71  changes its diameter of the winding along the longitudinal direction, and has the maximum diameter of the winding at a portion positioned near the outer periphery of the position at which the base end portion  11   d  of the first plunger  11  and the base end portion  12   d  of the second plunger  12  are in contact with each other in a state where the spring member  71  is not stroked (a state shown in  FIG. 10 ). Both end portions of the spring member  71  are press fitted onto the first plunger  11  and the second plunger  12 , respectively. 
     According to the conductive contact  7  having the above configuration, smooth sliding between the base end portions  11   d  and  12   d  can be realized at the time of contact with a test object. 
     In the case shown in  FIG. 10 , because the diameter of the winding of the spring member  71  is smaller at the end portion in the longitudinal direction than at the center portion in the longitudinal direction, the contact pressure at the sliding portion between the base end portions  11   d  and  12   d  increases as the stroke of each plunger increases. However, because a load increases as the stroke increase, the stroke is not affected. 
       FIG. 11  is a diagram illustrating a configuration of a conductive contact according to still another embodiment of the present invention. A conductive contact  8  shown in  FIG. 11  includes the first plunger  11 , the second plunger  12 , and a spring member  81  that couples the first plunger  11  and the second plunger  12 . The spring member  81  changes its pitch of the winding along the longitudinal direction. Specifically, the first plunger  11  side of the spring member  81  is a loosely wound portion  81   a  and the second plunger  12  side thereof is a loosely wound portion  81   b , and a tightly wound portion  81   c  that is tightly wound is provided between the loosely wound portion  81   a  and the loosely wound portion  81   b . The tightly wound portion  81   c  is positioned near the outer periphery of the position at which the base end portion  11   d  of the first plunger  11  and the base end portion  12   d  of the second plunger  12  are in contact with each other in a state where the spring member  81  is not stroked. Both ends of the spring member  81  are press fitted onto the first plunger  11  and the second plunger  12 , respectively. 
     According to the conductive contact  8  having the above configuration, contact between the base end portions  11   d  and  12   d  can be ensured. 
     The spring member described above can be applied regardless of the shape of the base end portion of each plunger. Accordingly, the spring member  71  or  81  can be applied instead of the spring member  13  of the above described conductive contacts  4  to  6 . 
     As described above, the present invention can include various embodiments and the like not described here, and various design changes and the like can be made in the range without departing from the technical idea as specified by the claims. 
     INDUSTRIAL APPLICABILITY 
     As described above, the conductive contact according to the present invention is useful when performing an electrical characteristics test on such as a semiconductor integrated circuit, and is particularly suitable for performing transmission and reception of a signal with high frequency of 1 GHz or more.