Patent Publication Number: US-2023138105-A1

Title: Probe unit

Description:
FIELD 
     The present invention relates to a probe unit that accommodates a contact probe that performs signal input and output with respect to a predetermined circuit structure. 
     BACKGROUND 
     Conventionally, when conducting state inspection or operating characteristic inspection of an inspection target such as a semiconductor integrated circuit or a liquid crystal panel is performed, a probe unit including a contact probe that electrically connects the inspection target and a signal processing device that outputs an inspection signal and a probe holder that accommodates a plurality of the contact probes is used. 
     In general, when a high-frequency electric signal is input and output, a loss of a signal called an insertion loss (insertion loss) occurs. In order to operate the probe unit at high speed with high accuracy, it is important to reduce the insertion loss in the frequency domain to be used. For example, Patent Literature 1 discloses a technique of providing an air layer around a contact probe to perform characteristic impedance matching. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 2012-98219 A 
     SUMMARY 
     Technical Problem 
     However, in the technique disclosed in Patent Literature 1, although the impedance at the central portion of the contact probe can be adjusted, the characteristic impedance at the distal end portion and the proximal end portion cannot be adjusted. 
     The present invention has been made in view of the above, and an object thereof is to provide a probe unit capable of adjusting the characteristic impedance of the entire contact probe. 
     Solution to Problem 
     To solve the above-described problem and achieve the object, a probe unit according to the present invention includes: a plurality of first contact probes each coming into contact with an electrode to be contacted on one end side in a longitudinal direction; a second contact probe connected to an external ground; and a probe holder configured to hold the first and second contact probes, the probe holder including a first hollow portion configured to allow the first contact probes to be inserted therethrough and hold the first contact probes, a second hollow portion configured to allow the second contact probe to be inserted therethrough and hold the second contact probe, and a through-hole provided around the first hollow portion, wherein the probe holder includes a conductive portion that constitutes the through-hole and electrically connects the through-hole and the second contact probe. 
     Moreover, in the above-described probe unit according to the present invention, the conductive portion is provided in the through-hole and on a surface forming an opening end of the through-hole. 
     Moreover, in the above-described probe unit according to the present invention, the through-hole has a stepped hole shape having a partially different diameter. 
     Moreover, in the above-described probe unit according to the present invention, the through-hole has a stepped hole shape in which central axis positions are different from each other. 
     Moreover, in the above-described probe unit according to the present invention, the probe holder is formed of one member. 
     Moreover, in the above-described probe unit according to the present invention, the probe holder is formed by laminating a plurality of members in a penetrating direction of the first hollow portion. 
     Moreover, in the above-described probe unit according to the present invention, the through-hole is formed by penetration holes formed in the plurality of members, respectively, and has a stepped hole shape in which diameters of the penetration holes are partially different in at least one member. 
     Moreover, in the above-described probe unit according to the present invention, the through-hole is formed by penetration holes formed in the plurality of members, respectively, and has a stepped hole shape in which central axis positions of the penetration holes are different from each other in at least one member. 
     Moreover, in the above-described probe unit according to the present invention, in the plurality of members, penetration holes constituting the through-hole are formed, respectively, and in the through-hole, penetration holes formed in members adjacent to each other in a laminating direction of the members at least partially overlap with each other when viewed from a penetrating direction of the penetration holes. 
     Moreover, in the above-described probe unit according to the present invention, in the through-hole, an opening has an elongated hole shape when viewed from a penetrating direction. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to adjust the characteristic impedance of the entire contact probe. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a partial cross-sectional view illustrating a configuration of a main portion of a probe unit according to a first embodiment of the present invention. 
         FIG.  2    is a view for explaining an arrangement of through-holes of the probe unit according to the first embodiment of the present invention. 
         FIG.  3    is a view illustrating a state at the time of inspection of a semiconductor integrated circuit using a probe holder according to the first embodiment of the present invention. 
         FIG.  4    is a view for explaining an arrangement of through-holes of a probe unit according to a first modification of the first embodiment of the present invention. 
         FIG.  5    is a view for explaining an arrangement of through-holes of a probe unit according to a second modification of the first embodiment of the present invention. 
         FIG.  6    is a view for explaining an arrangement of through-holes of a probe unit according to a third modification of the first embodiment of the present invention. 
         FIG.  7    is a cross-sectional view for explaining a configuration of a main portion of a through-hole of a probe unit according to a fourth modification of the first embodiment of the present invention. 
         FIG.  8    is a cross-sectional view for explaining a configuration of a main portion of a through-hole of a probe unit according to a fifth modification of the first embodiment of the present invention. 
         FIG.  9    is a cross-sectional view for explaining a configuration of a main portion of a through-hole of a probe unit according to a sixth modification of the first embodiment of the present invention. 
         FIG.  10    is a partial cross-sectional view illustrating a configuration of a main portion of a probe unit according to a second embodiment of the present invention. 
         FIG.  11    is a partial cross-sectional view illustrating a configuration of a main portion of a probe unit according to a third embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited by the following embodiments. In addition, each drawing referred to in the following description merely schematically illustrates a shape, a size, and a positional relationship to such an extent that the contents of the present invention can be understood, and thus the present invention is not limited only to the shape, the size, and the positional relationship illustrated in each drawing. 
     First Embodiment 
       FIG.  1    is a partial cross-sectional view illustrating a configuration of a main portion of a probe unit according to a first embodiment of the present invention. A probe unit  1  illustrated in  FIG.  1    is a device used when an electrical characteristic inspection is performed on a semiconductor integrated circuit as an inspection target, and is a device that electrically connects a semiconductor integrated circuit (a semiconductor integrated circuit  100  to be described later) and a circuit board (a circuit board  200  to be described later) that outputs an inspection signal to the semiconductor integrated circuit. 
     The probe unit  1  includes a conductive signal contact probe  2 A (hereinafter, simply referred to as a “signal probe  2 A”) that comes into contact with the semiconductor integrated circuit  100  and the circuit board  200 , which are two contact objects different from each other, at each end in a longitudinal direction and conducts a signal for inspection, a ground contact probe  2 B (hereinafter, simply referred to as a “ground probe  2 B”) that is connected to an external ground electrode, and a probe holder  3  that accommodates and holds the signal probe  2 A and the ground probe  2 B according to a predetermined pattern. Note that the probe unit  1  may include a holder member that is provided around the probe holder  3  and suppresses positional displacement of the semiconductor integrated circuit from occurring at the time of inspection. 
     The signal probe  2 A is formed using a conductive material, and includes a first plunger  21  that comes into contact with an electrode to which an inspection signal of a semiconductor integrated circuit is input when the semiconductor integrated circuit is inspected, a second plunger  22  that comes into contact with an electrode that outputs an inspection signal of a circuit board including an inspection circuit, and a spring member  23  that is provided between the first plunger  21  and the second plunger  22  and stretchably couples the first plunger  21  and the second plunger  22 . The first plunger  21 , the second plunger  22 , and the spring member  23  constituting the signal probe  2 A have the same axis. In the signal probe  2 A illustrated in  FIG.  1   , the longitudinal axes (central axes) of the first plunger  21 , the second plunger  22 , and the spring member  23  coincide with an axis N P . 
     When the semiconductor integrated circuit is brought into contact with the signal probe  2 A, the spring member  23  expands and contracts to soften impact on a connection electrode of the semiconductor integrated circuit, and applies a load to the semiconductor integrated circuit and the circuit board. Note that in the following description, in the signal probe  2 A, a side that comes into contact with the electrode of the semiconductor integrated circuit is defined as a distal end side, and the side opposite to the semiconductor integrated circuit side in the axial direction is defined as a proximal end side. In addition, when the distal end side and the proximal end side are defined by a plunger alone, in the plunger that comes into contact with the semiconductor integrated circuit, the semiconductor integrated circuit side is defined as a distal end side, and the side opposite to the semiconductor integrated circuit side in the axial direction is defined as a proximal end side. In addition, in a plunger that comes into contact with the circuit board, the circuit board side is defined as a distal end side, and the side opposite to the circuit board side in the axial direction is defined as a proximal end side. 
     The first plunger  21  can move in the axial direction by the expansion and contraction action of the spring member  23 , is biased in a direction approaching the semiconductor integrated circuit by an elastic force of the spring member  23  at the time of inspection, and comes into contact with the electrode of the semiconductor integrated circuit. In addition, the second plunger  22  can move in the axial direction by the expansion and contraction action of the spring member  23 , is biased in a direction approaching the circuit board by the elastic force of the spring member  23 , and comes into contact with the electrode of the circuit board. 
     In the spring member  23 , the first plunger  21  side is a dense wound portion  23   a , and the second plunger  22  side is a rough wound portion  23   b . An end of the dense wound portion  23   a  is connected to the first plunger  21 . On the other hand, an end of the rough wound portion  23   b  is connected to the second plunger  22 . The first plunger  21  and the second plunger  22  are joined to the spring member  23  by fitting and/or soldering by a winding force of the spring. 
     The ground probe  2 B has the same configuration as that of the signal probe  2 A. Specifically, the ground probe  2 B is formed using a conductive material, and includes the first plunger  21  that comes into contact with a grounding electrode of a semiconductor integrated circuit when the semiconductor integrated circuit is inspected, the second plunger  22  that comes into contact with a grounding electrode of a circuit board, and the spring member  23  that is provided between the first plunger  21  and the second plunger  22  and stretchably couples the first plunger  21  and the second plunger  22 . The first plunger  21 , the second plunger  22 , and the spring member  23  constituting the ground probe  2 B have the same axis. In the ground probe  2 B illustrated in  FIG.  1   , the longitudinal axes (central axes) of the first plunger  21 , the second plunger  22 , and the spring member  23  coincide with the axis N P . 
     The probe holder  3  is formed by laminating a first member  31 , a second member  32 , a third member  33 , and a fourth member  34  formed using an insulating material such as resin, machinable ceramic, or silicon. In the probe holder  3  illustrated in  FIG.  1   , the third member  33 , the first member  31 , the second member  32 , and the fourth member  34  are laminated in this order from the upper side of the figure. The first member  31  to the fourth member  34  are fixed by a known method such as screwing or bonding. 
     In the probe holder  3 , a hollow portion  35  forming a space for accommodating a plurality of the signal probes  2 A and a hollow portion  36  forming a space for accommodating a plurality of the ground probes  2 B are formed. In addition, in the probe holder  3 , a plurality of through-holes  37  is formed around each signal probe  2 A. 
     In the first member  31 , a surface forming a surface of the first member  31  is subjected to plating treatment. A conductive material is used for the plating treatment. Therefore, a first conductive film  31   a  and a second conductive film  31   b  are formed on the surface of the first member  31 . Note that the first conductive film  31   a  is formed on a surface of a portion, other than the hollow portion  35 , including a portion where each through-hole  37  is formed. In addition, the second conductive film  31   b  is formed on a surface of a portion where the hollow portion  35  is formed. The first conductive film  31   a  and the second conductive film  31   b  are separated from each other, and insulation is secured. In the example illustrated in  FIG.  1   , the film is separated by cutting a part of the film. 
     Similarly to the first member  31 , surfaces of the second member  32  to the fourth member  34  except for a portion forming the inner peripheral surface of the hollow portion  35  are subjected to plating treatment. A first conductive film  32   a  and a second conductive film  32   b  are formed on the surfaces of the second member  32 . A first conductive film  33   a  and a second conductive film  33   b  are formed on the surface of the third member  33 . A first conductive film  34   a  and a second conductive film  34   b  are formed on the surface of the fourth member  34 . The first conductive films  32   a  to  34   a  are formed on surfaces of portions, other than the hollow portion  35 , including the portions where the through-hole  37  is formed. In addition, the second conductive films  32   b  to  34   b  are formed on surfaces of portions where the hollow portion  35  is formed. At least some of the first conductive films  31   a  to  34   a  constitute a conductive portion. 
     Therefore, in the probe holder  3  formed by laminating the first member  31  to the fourth member  34 , a conductive film exists at the boundary between the members and on the outer surface. 
     The hollow portion  35  is formed such that axes of penetration holes formed in the first member  31  to the fourth member  34  coincide with each other. In the hollow portion  35 , the second conductive films  31   b  to  34   b  are formed on the inner peripheral surface, and a conductive inner peripheral surface is formed. The hollow portion  35  extends in the laminating direction of the first member  31  to the fourth member  34 . 
     The hollow portion  36  is formed such that axes of penetration holes formed in the first member  31  to the fourth member  34  coincide with each other. In the hollow portion  36 , the first conductive films  31   a  to  34   a  are formed on the inner peripheral surface, and a conductive inner peripheral surface is formed. 
     The formation positions of the hollow portions  35  and  36  are determined according to the wiring pattern of the semiconductor integrated circuit. The hollow portions  35  and  36  each have a stepped hole shape having different diameters along the penetrating direction. That is, each holder hole includes a small diameter portion having an opening on an end surface of the probe holder  3  and a large diameter portion having a diameter larger than that of the small diameter portion. In the probe holder  3  illustrated in  FIG.  1   , step portions are formed at the boundary between the first member  31  and the third member  33  and the boundary between the second member  32  and the fourth member  34 , respectively. The shape of each holder hole is determined according to the configurations of the signal probe  2 A and the ground probe  2 B to be accommodated. 
     The first plunger  21  of the signal probe  2 A has a function of preventing the signal probe  2 A from coming off the probe holder  3  by a flange abutting on the wall surface of the third member  33 . In addition, the second plunger  22  has a function of preventing the signal probe  2 A from coming off the probe holder  3  by a flange abutting on the wall surface of the fourth member  34 . 
     The first plunger  21  of the ground probe  2 B has a function of preventing the ground probe  2 B from coming off the probe holder  3  by a flange abutting on the wall surface of the third member  33 . In addition, the second plunger  22  has a function of preventing the ground probe  2 B from coming off the probe holder  3  by a flange abutting on the wall surface of the fourth member  34 . 
     The through-hole  37  is formed such that axes of penetration holes formed in the first member  31  to the fourth member  34  coincide with each other. That is, the through-hole  37  is provided from a surface on the distal end side to a surface on the proximal end side of the signal probe  2 A in the probe holder  3 . In the through-hole  37  illustrated in  FIG.  1   , the central axis of each penetration hole overlaps with an axis N T . In the through-hole  37 , the shape of an opening in a direction orthogonal to the penetrating direction forms a circle. In the through-hole  37 , the first conductive films  31   a  to  34   a  are formed on the inner peripheral surface, and a conductive inner peripheral surface is formed. 
     The through-hole  37  forms a cylindrical hollow space, and one or a plurality of the through-holes  37  is formed around the signal probe  2 A. In the first embodiment, an example in which eight through-holes  37  are formed around one signal probe  2 A will be described.  FIG.  2    is a view for explaining an arrangement of through-holes of the probe unit according to the first embodiment of the present invention. For example, the eight through-holes  37  are provided at equal intervals around the arrangement position (axis N P ) of the signal probe  2 A. In  FIG.  2   , the diameters of the penetration holes of the through-holes  37  are the same, and the shortest distance between the through-holes  37  and the axis N P  is a same distance d 1 . That is, the center of a circle (broken line in  FIG.  2   ) passing through the centers of all the through-holes  37  overlaps with the center (axis N P ) of the signal probe  2 A. A through-hole group including all the through-holes  37  has a coaxial structure with respect to the signal probe  2 A. 
     In the first embodiment, the arrangement position and the number of the through-holes  37 , the size of each penetration hole formed by each through-hole  37 , and the like are determined such that the characteristic impedance when the signal probe  2 A and the ground probe  2 B are viewed as one transmission path becomes a preset value (for example, 50Ω). 
       FIG.  3    is a view illustrating a state at the time of inspection of the semiconductor integrated circuit  100  in the probe unit  1 . At the time of inspection, in the signal probe  2 A, the first plunger  21  comes into contact with an inspection signal electrode  101  of the semiconductor integrated circuit  100 , and the second plunger  22  comes into contact with an inspection signal electrode  201  of the circuit board  200 . On the other hand, in the ground probe  2 B, the first plunger  21  comes into contact with a grounding electrode  102  of the semiconductor integrated circuit  100 , and the second plunger  22  comes into contact with a grounding electrode  202  of the circuit board  200 . At the time of inspection of the semiconductor integrated circuit  100 , the spring member  23  is compressed by a contact load from the semiconductor integrated circuit  100 . 
     For example, an inspection signal supplied from the circuit board  200  to the semiconductor integrated circuit  100  at the time of inspection reaches the electrode  101  of the semiconductor integrated circuit  100  from the electrode  201  of the circuit board  200  via the second plunger  22 , the dense wound portion  23   a  (or the second conductive film), and the first plunger  21  of the signal probe  2 A. As described above, in the signal probe  2 A, the first plunger  21  and the second plunger  22  are electrically connected via the dense wound portion  23   a , so that the conduction path of the electric signal can be minimized. Therefore, it is possible to prevent a signal from flowing to the rough wound portion  23   b  at the time of inspection and to reduce resistance and inductance. At this time, a path passing through the second plunger  22 , the second conductive film, and the first plunger  21  can transmit a signal not through the spring member  23 . 
     In addition, the first plunger  21  of the ground probe  2 B comes into contact with the first conductive film  33   a  or  31   a . On the other hand, the second plunger  22  of the ground probe  2 B comes into contact with the first conductive film  34   a  or  32   a . Moreover, the spring member  23  of the ground probe  2 B comes into contact with the first conductive film  31   a  or  32   a.    
     In general, in an electronic circuit that handles an AC signal, it is known that a signal is reflected by an amount corresponding to a ratio between different impedances at a portion where wirings having different impedances are connected, and propagation of the signal is hindered. The same applies to the relationship between the semiconductor integrated circuit  100  and the signal probe  2 A to be used, and in a case where the characteristic impedance of the semiconductor integrated circuit  100  and the characteristic impedance in the signal probe  2 A have greatly different values, the loss of the electric signal occurs and the waveform of the electric signal is distorted. 
     In addition, the ratio of signal reflection occurring in the connection portion due to the difference in characteristic impedance increases as the speed of the semiconductor integrated circuit  100  increases, that is, as the frequency increases. Therefore, when the probe unit  1  corresponding to the semiconductor integrated circuit  100  driven at a high frequency is manufactured, it is important to accurately perform impedance adjustment in which the value of the characteristic impedance of the signal probe  2 A matches that of the semiconductor integrated circuit  100 . 
     However, it is not easy to change the shape and the like of the signal probe  2 A from the viewpoint of performing impedance matching. This is because the outer diameter of the signal probe  2 A is suppressed to 1 mm or less, and the signal probe  2 A is originally limited to having a complicated shape including the first plunger  21 , the second plunger  22 , and the spring member  23 , and thus it is difficult to change the shape to a shape suitable for impedance matching from the viewpoint of design and manufacturing. 
     Therefore, in the present embodiment, instead of changing the structure of the signal probe  2 A, a configuration is adopted in which the value of the characteristic impedance is adjusted by arranging the through-hole  37  around the first plunger  21 , the second plunger  22 , and the spring member  23 . By adopting such a configuration, a conventional structure can be used as the structure of the signal probe  2 A. For example, the same probe as the conventional ground probe  2 B can be used as the signal probe  2 A. 
     In addition, in the present embodiment, since the shape of the signal probe  2 A does not need to be changed to a shape suitable for impedance matching, the degree of freedom of the probe shape to be used can be improved. 
     Furthermore, in the first embodiment, by providing, around the signal probe  2 A, the through-hole  37  extending from the surface on the distal end side to the surface on the proximal end side of the signal probe  2 A in the probe holder  3 , the value of the characteristic impedance of the distal end portion and the proximal end portion of the signal probe  2 A can be adjusted. Specifically, the value of the characteristic impedance can be adjusted by adjusting the number of through-holes to be arranged, the diameters of the penetration holes of the through-holes, and the arrangement of the through-holes (distance to the signal probe  2 A). Moreover, by surrounding the signal probe  2 A with a plurality of the through-holes  37 , it is possible to make the signal probe  2 A less susceptible to external factors such as noise and to reduce energy loss due to energy outflow to the outside. 
     In the first embodiment described above, the through-holes  37  are arranged around the signal probe  2 A, and are connected to an external ground via the ground probe  2 B. According to the first embodiment, the characteristic impedance of the distal end portion and the proximal end portion of the signal probe  2 A can be adjusted by the through-holes  37  indirectly connected to an external ground. According to the first embodiment, it is possible to perform the overall characteristic impedance adjustment including ends of the signal probe  2 A. In addition, according to the first embodiment, the ground position in a direction orthogonal to an axial direction with respect to the signal probe  2 A can be adjusted by adjusting the position of the through-holes. 
     In addition, according to the first embodiment described above, since the outer surface of the probe holder  3  is covered with the conductive film, the high frequency characteristics are excellent as compared with the case where the plating treatment is not performed. 
     In addition, according to the first embodiment described above, since the characteristic impedance can be adjusted by the through-holes, the degree of freedom in the arrangement of the ground probe  2 B can be improved. 
     Note that in the first embodiment described above, the first conductive films  33   a  and  34   a  may be connected to an external ground. 
     In addition, in the first embodiment described above, an example has been described in which a plurality of through-holes is arranged symmetrically with respect to the axis N P  of the signal probe, but the through-holes may be arranged asymmetrically. 
     In addition, in the above-described first embodiment, an example has been described in which a plurality of through-holes is evenly arranged for one signal probe, but the through-holes may be arranged unevenly. In this case, the term “uneven” may be uneven in that the circumferential distance of the circle centered on one point on the axis N P  of the signal probe is different, may be uneven in that the shortest distance (distance d 1  described above) from the axis N P  is different, or may be both. 
     In addition, in the first embodiment described above, an example has been described in which a conductive film is formed on each member of the probe holder  3 , but instead of the film, a conductive plate, a sheet, a film, or the like that is sufficiently thin compared to the thickness of the member may be used. 
     In addition, in the first embodiment described above, it has been described that the second conductive films  31   b  to  34   b  are formed on the surface of the hollow portion  35  to form conductive penetration holes, but an insulating inner peripheral surface may be formed without forming the second conductive film. 
     (First Modification) 
       FIG.  4    is a view for explaining an arrangement of through-holes of a probe unit according to a first modification of the first embodiment of the present invention. In the probe unit according to the first modification, the sizes of some through-holes in the probe holder  3  described above are different. Other configurations are the same as those of the probe unit  1 , and thus the description thereof will be omitted. 
     In a probe holder according to the first modification, six through-holes  37  and two through-holes  37 A are formed around the signal probe  2 A.  FIG.  4    illustrates an example in which three sets of the through-holes  37  are arranged to face each other with the axis N P  interposed therebetween, and the through-holes  37 A are arranged to face each other with the axis N P  interposed therebetween. 
     Each through-hole  37 A is formed such that the axes of penetration holes formed in the first member  31  to the fourth member  34  coincide with each other. The through-hole  37 A forms a cylindrical hollow space. In the through-hole  37 A, the shape of an opening in a direction orthogonal to the penetrating direction forms a circle. A conductive film (for example, the first conductive films  31   a  to  34   a  described above) is formed on an inner peripheral surface of the through-hole  37 A, and the inner peripheral surface has conductivity. The diameters of the penetration holes of the through-hole  37 A are larger than the diameters of the penetration holes of each through-hole  37 . 
     The through-holes  37  and  37 A are arranged at positions where the center of each penetration hole passes through a circle (broken line in  FIG.  4   ) centered on the axis N P  of the signal probe  2 A. In addition, a shortest distance d 2  between the through-hole  37 A and the axis N P  is shorter than the shortest distance d 1  between the through-hole  37  and the axis N P . 
     As in the first modification, the through-holes  37  and  37 A having different sizes are arranged around the signal probe  2 A, and are connected to an external ground via the ground probe  2 B. In the first modification, as in the first embodiment, the characteristic impedances of the distal end portion and the proximal end portion of the signal probe  2 A can be adjusted by the through-holes  37  and  37 A indirectly connected to an external ground. 
     (Second Modification) 
       FIG.  5    is a view for explaining an arrangement of through-holes of a probe unit according to a second modification of the first embodiment of the present invention. In the probe unit according to the second modification, the sizes and arrangement of some through-holes in the probe holder  3  described above are different. Other configurations are the same as those of the probe unit  1 , and thus the description thereof will be omitted. 
     In the probe holder according to the second modification, six through-holes  37  and two through-holes  37 A are formed around the signal probes  2 A.  FIG.  5    illustrates an example in which three sets of the through-holes  37  are arranged to face each other with the axis N P  interposed therebetween, and the through-holes  37 A are arranged to face each other with the axis N P  interposed therebetween. 
     The through-holes  37  and  37 A are arranged at positions where the shortest distance between each through-hole  37  and the axis N P  and the shortest distance between each through-hole  37 A and the axis N P  become the same distance d 1 . 
     As in the second modification, the through-holes  37  and  37 A having different sizes are arranged around the signal probe  2 A, and are connected to an external ground via the ground probe  2 B. In the second modification, as in the first embodiment, the characteristic impedances of the distal end portion and the proximal end portion of the signal probe  2 A can be adjusted by the through-holes  37  and  37 A indirectly connected to an external ground. 
     (Third Modification) 
       FIG.  6    is a view for explaining an arrangement of through-holes of a probe unit according to a third modification of the first embodiment of the present invention. In the probe unit according to the third modification, the sizes and arrangement of some through-holes in the probe holder  3  described above are different. Other configurations are the same as those of the probe unit  1 , and thus the description thereof will be omitted. 
     In the probe holder according to the third modification, eight through-holes  37 B are formed around the signal probe  2 A.  FIG.  6    illustrates an example in which four sets of the through-holes  37 B are arranged to face each other with the axis N P  interposed therebetween. 
     In each through-hole  37 B, an opening has an elongated hole shape when viewed from the penetrating direction. The through-holes  37 B are arranged at positions where the center of gravity of each penetration hole passes through a circle (broken line in  FIG.  6   ) centered on the axis N P  of the signal probe  2 A. In each through-hole  37 B, a conductive film (for example, the first conductive films  31   a  to  34   a  described above) is formed on an inner peripheral surface, and the inner peripheral surface has conductivity. 
     As in the third modification, a plurality of the through-holes  37 B is arranged around the signal probe  2 A, and is connected to an external ground via the ground probe  2 B. In the third modification, as in the first embodiment, the characteristic impedances of the distal end portion and the proximal end portion of the signal probe  2 A can be adjusted by the through-holes  37 B indirectly connected to an external ground. 
     In addition, in the third modification, since the opening shape of the penetration hole of each through-hole  37 B is an elongated hole, a range surrounding the signal probe  2 A by the through-holes  37 B is made larger than that of the through-holes  37  and  37  A. As described above, by forming the shape of the through-hole into a shape other than a circle, the degree of freedom in adjusting the characteristic impedance increases, and as a result, the high frequency characteristics of the probe unit can be improved. In addition, by increasing the surrounding range, energy loss due to energy outflow to the outside can be further reduced. 
     (Fourth Modification) 
       FIG.  7    is a cross-sectional view for explaining a configuration of a main portion of a through-hole of a probe unit according to a fourth modification of the first embodiment of the present invention. In the probe unit according to the fourth modification, the shape of a through-hole in the probe holder  3  described above is different. Other configurations are the same as those of the probe unit  1 , and thus the description thereof will be omitted. 
     The through-hole according to the fourth modification is formed by allowing the penetration holes formed in the first member  31  to the fourth member  34  to communicate with each other. In the through-hole, conductive films (for example, the first conductive films  31   a  to  34   a  described above) are formed on the inner peripheral surface, and a conductive inner peripheral surface is formed. The through-hole is partially different in diameter. Specifically, for example, a diameter Q 1  of a penetration hole  37   a  formed in the third member  33  is different from a diameter Q 2  of a penetration hole  37   b  formed in the first member  31 . A central axis N 1  of the penetration hole  37   a  and a central axis N 2  of the penetration hole  37   b  are linearly continuous. 
     As in the fourth modification, by arranging a through-hole having a stepped hole shape around the signal probe  2 A, and connecting the through-hole to an external ground via the ground probe  2 B, the same effects as those of the first embodiment can be obtained, and characteristic impedance adjustment according to the shape of the signal probe  2 A can be performed. 
     (Fifth Modification) 
       FIG.  8    is a cross-sectional view for explaining a configuration of a main portion of a through-hole of a probe unit according to a fifth modification of the first embodiment of the present invention. In the probe unit according to the fifth modification, the shape of a through-hole in the probe holder  3  described above is different. Other configurations are the same as those of the probe unit  1 , and thus the description thereof will be omitted. 
     The through-hole according to the fifth modification is formed by allowing the penetration holes formed in the first member  31  to the fourth member  34  to communicate with each other. In the through-hole, conductive films (for example, the first conductive films  31   a  to  34   a  described above) are formed on the inner peripheral surface, and a conductive inner peripheral surface is formed. The through-hole is a partially different in axis position. Specifically, for example, the central axis N 1  of a penetration hole  37   c  formed in the third member  33  and the central axis N 2  of a penetration hole  37   d  formed in the first member  31  are different in position. In addition, a diameter Q 3  of the penetration hole  37   c  and a diameter Q 4  of the penetration hole  37   d  are the same diameter. As described above, the through-hole according to the fifth modification is formed by the penetration holes in which the position of the central axis is partially different. At this time, when the through-hole is viewed from the laminating direction of the first member  31  to the fourth member  34 , the penetration holes formed in the members adjacent to each other in the laminating direction of the members at least partially overlap with each other. The through-hole is formed by the penetration holes formed in the respective members at least partially communicating with each other. 
     As in the fifth modification, by arranging a through-hole, around the signal probe  2 A, having a stepped hole shape in which the axes of some penetration holes are misaligned, and connecting the through-hole to an external ground via the ground probe  2 B, the same effects as those of the first embodiment can be obtained, and characteristic impedance adjustment according to the shape of the signal probe  2 A can be performed. 
     (Sixth Modification) 
       FIG.  9    is a cross-sectional view for explaining a configuration of a main portion of a through-hole of a probe unit according to a sixth modification of the first embodiment of the present invention. In the probe unit according to the sixth modification, the shape of a through-hole in the probe holder  3  described above is different. Other configurations are the same as those of the probe unit  1 , and thus the description thereof will be omitted. 
     The through-hole according to the sixth modification is formed by allowing the penetration holes formed in the first member  31  to the fourth member  34  to communicate with each other. In the through-hole, conductive films (for example, the first conductive films  31   a  to  34   a  described above) are formed on the inner peripheral surface, and a conductive inner peripheral surface is formed. The through-hole is a partially different in diameter and axis position. Specifically, for example, a diameter Q 5  of a penetration hole  37   e  formed in the third member  33  is different from a diameter Q 6  of a penetration hole  37   f  formed in the first member  31 . In addition, the central axis N 1  of the penetration hole  37   e  and the central axis N 2  of the penetration hole  37   f  are different in position. 
     As in the sixth modification, by arranging, around the signal probe  2 A, a through-hole having a stepped hole shape in which diameters of some penetration holes are different and axes are further shifted, and connecting the through-hole to an external ground via the ground probe  2 B, the same effects as those of the first embodiment can be obtained, and characteristic impedance adjustment according to the shape of the signal probe  2 A can be performed. 
     The configurations of the through-holes according to the first to the sixth modifications may be appropriately combined. For example, each signal probe arranged in the same probe holder may be partially different in shape or arrangement. 
     Second Embodiment 
     Next, a second embodiment will be described with reference to  FIG.  10   .  FIG.  10    is a partial cross-sectional view illustrating a configuration of a main portion of a probe unit according to a second embodiment of the present invention. The probe unit according to the second embodiment includes a probe holder  3 A instead of the probe holder  3  described above. Other configurations are the same as those of the probe unit  1 , and thus the description thereof will be omitted. 
     The probe holder  3 A includes one member formed using an insulating material such as resin, machinable ceramic, or silicon. In the probe holder  3 A, the hollow portion  35  forming a space for accommodating a plurality of the signal probes  2 A and a hollow portion (the hollow portion  36  described above) forming a space for accommodating a plurality of the ground probes  2 B are formed. The hollow portions  35  and  36  each have a hole shape with a diameter that allows a contact probe to be inserted and removed and prevents the contact probe from coming off. In addition, in the probe holder  3 A, a plurality of through-holes  38  is formed around each signal probe  2 A. 
     In the probe holder  3 A, a surface of the probe holder  3 A is subjected to plating treatment. A conductive material is used for the plating treatment. Therefore, a first conductive film  3   a  and a second conductive film  3   b  are formed on the surface of the probe holder  3 A. The first conductive film  3   a  is formed on the surface of a portion, other than the hollow portion  35 , including a portion where each through-hole  38  is formed. In addition, the second conductive film  3   b  is formed on a surface of a portion where the hollow portion  35  is formed. The first conductive film  3   a  and the second conductive film  3   b  are separated from each other, and insulation is secured. 
     The through-hole  38  is a penetration hole in which the shape of an opening in a direction orthogonal to the penetrating direction forms a circle and the diameter is partially different. Specifically, the through-hole  38  includes a first hole  38   a  formed on one surface side (the side on which the first plunger  21  extends in  FIG.  10   ), a second hole  38   b  formed on another surface side (the side on which the second plunger  22  extends in  FIG.  10   ), and a third hole  38   c  provided between the first hole  38   a  and the second hole  38   b . The diameters of the openings of the first hole  38   a  and the second hole  38   b  are larger than the diameter of the opening of the third hole  38   c . In the through-hole  38 , the first conductive films  3   a  is formed on the inner peripheral surface, and a conductive inner peripheral surface is formed. Note that the central axes of the first hole  38   a , the second hole  38   b , and the third hole  38   c  are linearly continuous. 
     The through-hole  38  forms a cylindrical hollow space having a stepped shape having a partially different diameter, and a plurality of the through-holes  38  is formed around the signal probe  2 A. For example, as in the first embodiment, eight through-holes  38  are formed around one signal probe  2 A. 
     In the second embodiment described above, the through-holes  38  are arranged around the signal probe  2 A, and are connected to an external ground via the ground probe  2 B. As a result, according to the second embodiment, the characteristic impedance of the distal end portion and the proximal end portion of the signal probe  2 A can be adjusted by the through-holes  38  indirectly connected to the external ground. According to the second embodiment, it is possible to perform the overall characteristic impedance adjustment including ends of the signal probe  2 A. In addition, according to the second embodiment, the ground position in a direction orthogonal to an axial direction with respect to the signal probe  2 A can be adjusted by adjusting the position of the through-holes. 
     In addition, in the second embodiment, since the diameter of the penetration hole of each through-hole  38  is made partially different, characteristic impedance adjustment according to the shape of the signal probe  2 A can be performed. 
     Third Embodiment 
     Next, a third embodiment will be described with reference to  FIG.  11   .  FIG.  11    is a partial cross-sectional view illustrating a configuration of a main portion of a probe unit according to a third embodiment of the present invention. The probe unit according to the third embodiment includes a probe holder  4  instead of the probe holder  3  described above. Other configurations are the same as those of the probe unit  1 , and thus the description thereof will be omitted. 
     The probe holder  4  is formed by laminating a first member  41  and a second member  42  formed using an insulating material such as resin, machinable ceramic, or silicon. In the probe holder  4  illustrated in  FIG.  11   , the first member  41  and the second member  42  are laminated in this order from the upper side of the figure. The first member  41  and the second member  42  are fixed by a known method such as screwing or bonding. 
     In the probe holder  4 , the hollow portion  35  forming a space for accommodating a plurality of the signal probe  2 A and a hollow portion (not illustrated) forming a space for accommodating a plurality of the ground probes  2 B are formed. In addition, in the probe holder  4 , a plurality of through-holes  43  is formed around each signal probe  2 A. 
     In the first member  41 , a surface forming a surface of the first member  41  is subjected to plating treatment. A conductive material is used for the plating treatment. Therefore, a first conductive film  41   a  and a second conductive film  41   b  are formed on the surface of the first member  41 . Note that the first conductive film  41   a  is formed on the surface of a portion, other than the hollow portion  35 , including a portion where each through-hole  43  is formed. In addition, the second conductive film  41   b  is formed on a surface of a portion where the hollow portion  35  is formed. The first conductive film  41   a  and the second conductive film  41   b  are separated from each other, and insulation is secured. 
     Similarly to the first member  41 , in the second member  42 , a surface forming a surface of the second member  42  is subjected to plating treatment. A first conductive film  42   a  and a second conductive film  42   b  are formed on the surface of the second member  42 . Note that the first conductive film  42   a  is formed on the surface of a portion, other than the hollow portion  35 , including a portion where each through-hole  43  is formed. In addition, the second conductive film  42   b  is formed on a surface of a portion where the hollow portion  35  is formed. The first conductive film  42   a  and the second conductive film  42   b  are separated from each other, and insulation is secured. 
     Therefore, in the probe holder  4  formed by laminating the first member  41  and the second member  42 , a conductive film exists at the boundary between the members and on the outer surface. 
     The hollow portion  35  is formed such that axes of penetration holes formed in the first member  41  and the second member  42  coincide with each other. In the hollow portion  35 , the second conductive films  41   b  and  42   b  are formed on the inner peripheral surface, and a conductive inner peripheral surface is formed. 
     The through-hole  43  is a penetration hole having a stepped shape in which the shape of an opening in a direction orthogonal to the penetrating direction forms a circle and the position of the central axis is partially different. Specifically, the through-hole  43  includes a first hole  43   a  formed on one surface side (the side on which the first plunger  21  extends in  FIG.  11   ) of the probe holder  4 , a second hole  43   b  formed on another surface side (the side on which the second plunger  22  extends in  FIG.  11   ), and a third hole  43   c  provided between the first hole  43   a  and the second hole  43   b . The diameters of the openings of the first hole  43   a , the second hole  43   b , and the third hole  43   c  are the same. In addition, central axes N T1  and N T2  of the first hole  43   a  and the second hole  43   b  and a central axis N T3  of the third hole  43   c  are different from each other in position within a range where adjacent holes communicate with each other. In the through-hole  43 , the first conductive films  41   a  and  42   a  are formed on the inner peripheral surface, and a conductive inner peripheral surface is formed. 
     The through-hole  43  forms a cylindrical hollow space having a stepped shape, and a plurality of the through-holes  43  is formed around the signal probe  2 A. For example, as in the first embodiment, eight through-holes  43  are formed around one signal probe  2 A. 
     In the third embodiment described above, the through-holes  43  are arranged around the signal probe  2 A, and are connected to an external ground via the ground probe  2 B. As a result, according to the third embodiment, the characteristic impedance of the distal end portion and the proximal end portion of the signal probe  2 A can be adjusted by the through-holes  43  indirectly connected to the external ground. According to the third embodiment, it is possible to perform the overall characteristic impedance adjustment including ends of the signal probe  2 A. In addition, according to the third embodiment, the ground position in a direction orthogonal to an axial direction with respect to the signal probe  2 A can be adjusted by adjusting the position of the through-holes. 
     In addition, in the third embodiment, since the position of the central axis is made partially different in each penetration hole of each through-hole  43 , characteristic impedance adjustment according to the shape of the signal probe  2 A can be performed. 
     The first to the third embodiments and the modifications thereof described above can be appropriately combined. It is also possible to individually select and adopt the configuration of each contact probe from the arrangement or shape of the through-holes of the embodiments and the first to the third modifications. 
     Note that the configurations of the contact probe described here are merely examples, and various types of conventionally known probes can be applied. For example, the probe is not limited to including the plunger and the coil spring described above, and may be a probe including a pipe member, a wire probe that bends a pogo pin, a solid conductive member, a conductive pipe, or a wire in an arch shape to obtain a load, a connection terminal (connector) that connects electrical contacts, or a combination of these probes as appropriate. 
     In addition, the probe holder according to the first to the third embodiments and the modifications thereof described above is configured by laminating four or two members or configured by one member, but may be configured by laminating three members or five or more members. 
     In addition, in the first to the third embodiments and the modifications thereof described above, the conductive film may be partially pattern-formed without being formed on the entire member surface of the probe holder  3  as long as the through-hole and the ground probe  2 B can be electrically connected. For example, the conductive film may be formed on a portion constituting the through-hole and an outer surface of a member constituting an opening end of the through-hole (for example, the third member  33  and the fourth member  34  illustrated in  FIG.  1   ). At this time, the conductive film is electrically connected to the ground probe  2 B at least at the time of inspection. 
     As described above, the present invention can include various embodiments and the like not described herein, and various design changes and the like can be made without departing from the technical idea specified by the claims. 
     INDUSTRIAL APPLICABILITY 
     As described above, the probe unit according to the present invention is suitable for adjusting the characteristic impedance of the entire contact probe. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  PROBE UNIT 
               2 A CONTACT PROBE (SIGNAL PROBE) 
               2 B CONTACT PROBE (GROUND PROBE) 
               3 ,  3 A,  3 B PROBE HOLDER 
               3   a ,  31   a  to  34   a ,  41   a ,  42   a  FIRST CONDUCTIVE FILM 
               3   b ,  31   b  to  34   b ,  41   b ,  42   b  SECOND CONDUCTIVE FILM 
               21  FIRST PLUNGER 
               22  SECOND PLUNGER 
               23  SPRING MEMBER 
               23   a  DENSE WOUND PORTION 
               23   b  ROUGH WOUND PORTION 
               31 ,  41  FIRST MEMBER 
               32 ,  42  SECOND MEMBER 
               33  THIRD MEMBER 
               34  FOURTH MEMBER 
               35 ,  36  HOLLOW PORTION 
               37 ,  37 A,  37 B,  38 ,  43  THROUGH-HOLE 
               100  SEMICONDUCTOR INTEGRATED CIRCUIT 
               101 ,  102 ,  201 ,  202  ELECTRODE 
               200  CIRCUIT BOARD