Patent Publication Number: US-2011057664-A1

Title: Device-dependent replaceable unit and manufacturing method

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a device-dependent replaceable unit and a manufacturing method. More specifically, the present invention relates to a device-dependent replaceable unit that is provided in a test apparatus for establishing electrical connection with a device under test and a manufacturing method for manufacturing the device-dependent replaceable unit. 
     2. Related Art 
     A semiconductor test apparatus is structured such that some of its components are replaceable, and can thus perform a variety of tests by changing the replaceable components. One of the replaceable components is a device-dependent replaceable unit that serves as an electrical interface between the test apparatus and a device under test. 
     The device-dependent replaceable unit is constituted by a device socket that is structured in accordance with the shape of the device under test and the arrangement of the connection terminals of the device under test, a connector that connects the device socket to the main body of the test apparatus, and the like. The test apparatus can deal with a variety of devices under test by changing the device-dependent replaceable unit through insertion and extraction of the connector. 
     Japanese Patent Application Publication No. 11-094896 discloses a socket board that is mounted on a performance board. The socket board has inter-layer interconnections, and electrically connects an IC socket that is mounted on its upper surface to a coaxial cable that is connected to its lower surface. The socket board also physically supports the IC socket. 
     Japanese Patent Application Publication No. 2000-235061 discloses a socket board that has a plurality of sockets mounted thereon. Similarly to the socket board disclosed in Patent Document 1, this socket board also physically supports the sockets, and is provided with socket interconnections to provide part of the electrical connection with the sockets. 
     Here, devices under test are required to process signals the speed of which increases on the every day basis. This accordingly increases the speed of the test signals produced by semiconductor test apparatuses, and the test signal speed has recently reached as high as the gigahertz range. Such high-frequency signals are susceptible to the distributed constant of the electrical interconnections, and suffer from enormous transmission loss, mismatch-induced reflection, stub-induced reflection and the like. The signal deterioration in the test apparatuses makes it difficult to accurately evaluate the devices under test. Therefore, there is a demand for effective measures. 
     SUMMARY 
     Therefore, it is an object of an aspect of the innovations herein to provide a device-dependent replaceable unit and a manufacturing method, which are capable of overcoming the above drawbacks accompanying the related art. The above and other objects can be achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the innovations herein. 
     An aspect of the innovations herein may include a device-dependent replaceable unit that is selected depending on a type of a device under test. The device-dependent replaceable unit is to be mounted on a test apparatus to form a signal path between the device under test and the test apparatus. The device-dependent replaceable unit includes a socket board that has a front surface and a back surface, where the device under test is to be moved close to or away from the front surface of the socket board, and a plurality of spring pins that are positioned in a same manner as a plurality of connection terminals of the device under test, where the spring pins are supported by the socket board in such a manner that upper ends of the spring pins protrude from the front surface of the socket board and come into contact with the connection terminals of the device under test. 
     A different aspect of the innovations herein may include a device-dependent replaceable unit that is selected depending on a type of a device under test. The device-dependent replaceable unit is to be mounted on a test apparatus to form a signal path between the device under test and the test apparatus. The device-dependent replaceable unit includes a socket board that includes a plurality of vias penetrating therethrough, where the vias are positioned in a same manner as connection terminals on a back surface of a device socket that has on a front surface thereof connection terminals for the device under test, and the device socket is to be mounted on a front surface of the socket board, a block that is secured onto a back surface of the socket board, a spring pin that is embedded in the block in such a manner that an upper end of the spring pin protrudes from inside of the block to the back surface of the socket board and comes into contact with end surfaces of the vias at the back surface of the socket board, and a coaxial cable whose one end is connected to a lower end of the spring pin, where the coaxial cable extends from a back surface of the block toward the test apparatus. 
     A further different aspect of the innovations herein may include a device-dependent replaceable unit that is selected depending on a type of a device under test. The device-dependent replaceable unit is to be mounted on a test apparatus to form a signal path between the device under test and the test apparatus. The device-dependent replaceable unit includes a socket board that has a front surface to or from which the device under test is moved close or away, a connection member an upper end of which is, at the front surface of the socket board, electrically connected to a connection terminal of the device under test, a coaxial cable one end of which is connected to a lower end of the connection member, where the coaxial cable extends from a back surface of the socket board toward the test apparatus, and a conductor block that is secured onto the back surface of the socket board. Here, the conductor block is electrically coupled to a shield line of the coaxial cable and mechanically supports the coaxial cable. 
     A yet different aspect of the innovations herein may include a manufacturing method of manufacturing a device-dependent replaceable unit that is selected depending on a type of a device under test. The device-dependent replaceable unit is to be mounted on a test apparatus to form a signal path between the device under test and the test apparatus. The device-dependent replaceable unit includes a support that has a front surface and a back surface, a spring pin that is embedded in the support in such a manner that an upper end of the spring pin protrudes from inside of the support to the front surface of the support, and a coaxial cable one end of which is connected to a lower end of the spring pin, where the coaxial cable extends from the back surface of the support toward the test apparatus. Here, the manufacturing method includes inserting the spring pin into the support from the front surface, inserting the one end of the coaxial cable into the support from the back surface, and electrically coupling the spring pin and the coaxial cable to each other. 
     A different aspect of the innovations herein may include a test apparatus including a test head that performs a test on a device under test, and a device-dependent replaceable unit that is selected depending on a type of the device under test. The device-dependent replaceable unit is mounted on the test head to form a signal path between the device under test and the test apparatus. Here, the device-dependent replaceable unit includes a socket board that has a front surface and a back surface, where the device under test is to be moved close to or away from the front surface of the socket board, and a plurality of spring pins that are positioned in a same manner as a plurality of connection terminals of the device under test, where the spring pins are supported by the socket board in such a manner that upper ends of the spring pins protrude from the front surface of the socket board and come into contact with the connection terminals of the device under test. 
     A further different aspect of the innovations herein may include a test apparatus including a test head that performs a test on a device under test, and a device-dependent replaceable unit that is selected depending on a type of the device under test. The device-dependent replaceable unit is mounted on the test head to form a signal path between the device under test and the test apparatus. The device-dependent replaceable unit includes a socket board that includes a plurality of vias penetrating therethrough, where the vias are positioned in a same manner as connection terminals on a back surface of a device socket that has on a front surface thereof connection terminals for the device under test, and the device socket is to be mounted on a front surface of the socket board, a block that is secured onto a back surface of the socket board, a spring pin that is embedded in the block in such a manner that an upper end of the spring pin protrudes from inside of the block to the back surface of the socket board and comes into contact with end surfaces of the vias at the back surface of the socket board, and a coaxial cable one end of which is connected to a lower end of the spring pin, where the coaxial cable extends from a back surface of the block toward the test apparatus. 
     A yet different aspect of the innovations herein may include a test apparatus including a test head that performs a test on a device under test, and a device-dependent replaceable unit that is selected depending on a type of the device under test. The device-dependent replaceable unit is mounted on the test head to form a signal path between the device under test and the test apparatus. The device-dependent replaceable unit includes a socket board that has a front surface on which the device under test is to be mounted, a connection member an upper end of which is, at the front surface of the socket board, electrically connected to a connection terminal of the device under test, a coaxial cable one end of which is connected to a lower end of the connection member, where the coaxial cable extends from a back surface of the socket board toward the test apparatus, and a conductor block that is secured onto the back surface of the socket board. Here, the conductor block is electrically coupled to a shield line of the coaxial cable and mechanically supports the coaxial cable. 
     Here, all the necessary features of the present invention are not listed in the summary. The sub-combinations of the features may become the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically illustrates the entire structure of a test apparatus  100 . 
         FIG. 2  is a vertical sectional view illustrating the configuration of a device-dependent replaceable unit  200 . 
         FIG. 3  illustrates a bottom surface of a socket board  220 . 
         FIG. 4  illustrates a connection structure  201  in the device-dependent replaceable unit  200 . 
         FIG. 5  is a vertical sectional view illustrating the configuration of the device-dependent replaceable unit  200 . 
         FIG. 6  illustrates the bottom surface of the socket board  220 . 
         FIG. 7  illustrates an upper surface of a conductor block  240 . 
         FIG. 8  is a horizontal sectional view illustrating a bottom surface of the conductor block  240 . 
         FIG. 9  illustrates the connection structure  201  in the device-dependent replaceable unit  200 . 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, an aspect of the present invention will be described based on some embodiments. The embodiments do not limit the invention according to the claims, and all the combinations of the features described in the embodiments are not necessarily essential to means provided by aspects of the invention. 
       FIG. 1  schematically illustrates the entire structure of a test apparatus  100 . The test apparatus  100  includes a handler  110 , a test head  120 , and a mainframe  130 . 
     The handler  110  stores therein devices under test  112 , and transports any required number of devices under test  112  each time requested to the test head  120  for tests. In this manner, a plurality of devices under test  112 , for example, 512 memories under test, can be sequentially tested automatically. 
     The test head  120  houses therein a plurality of pin electronics circuits  122 . A pin electronics circuit  122  generates a test signal to be sent to a device under test  112 , in response to an instruction issued by the mainframe  130 . The pin electronics circuit  122  sends the test signal to the device under test  112  and also receives the test signal that has been processed by the device under test  112  in order to evaluate the functions and characteristics of the device under test  112 . 
     The pin electronics circuits  122  are connected to a motherboard  124 . 
     On the upper surface of the test head  120 , a device-dependent replaceable unit  200  is attached. Here, the attached device-dependent replaceable unit  200  is selected from among a plurality of different device-dependent replaceable units  200 , and the connection portion of the attached device-dependent replaceable unit  200  needs to be shaped in the same manner as the connection portion of the device under test  112  that has been transported by the handler  110 . The device-dependent replaceable unit  200  enables the device under test  112  to send/receive electrical signals to/from the test head  120 . 
     The mainframe  130  is connected to the handler  110  and the test head  120  via connection cables  140  to comprehensively control the respective components. 
     When the test apparatus  100  including the above-described test head  120  is requested to test a different type of devices under test  112  or to perform a different type of tests, both or either of the device-dependent replaceable unit  200  and the pin electronics circuit  122  is changed. In this manner, the same test head  120  can continue to be used, and the expensive test apparatus  100  can be more efficiently used. 
       FIG. 2  is a vertical sectional view illustrating the configuration of the device-dependent replaceable unit  200 . The device-dependent replaceable unit  200  is structured by sequentially layering a socket board  220 , a spacer  230 , a conductor block  240 , and a housing  290 . 
     The socket board  220  includes inter-layer interconnections  224  and inter-layer vias  226  that are integrated together within an insulation layer  222 , and spring pins  260 . Some of the inter-layer interconnections  224  are formed on the lower surface of the socket board  220 . The inter-layer interconnections  224  are electrically connected to each other by means of the inter-layer vias  226 . 
     On the upper surface of the socket board  220 , a device socket  214  and a socket guide  212  are mounted. The device socket  214  has a plurality of through holes  211  that are positioned in the same manner as a plurality of connection terminals  111  of a device under test  112 . The connection terminals  111  are, for example, formed in compatible with Ball Grid Array (BGA). 
     The device socket  214  also has members that guide the pins of the handler  110 , which holds the device under test  112 . Thus, the connection terminals  111  of the device under test  112  held by the handler  110  are positioned to oppose the through holes  211 . 
     The spring pins  260  are embedded in the socket board  220  so as to penetrate the socket board  220  in the thickness direction. The spring pins  260  are guided and positioned in the same manner as the through holes  211  of the device socket  214 . 
     The upper ends of the spring pins  260  protrude from the upper surface of the socket board  220 , to extend into the through holes  211 . In other words, the device socket  214  serves to house the spring pins  260  therein. Thus, when the device under test  112  is pressed by the handler  110 , the connection terminals  111  come into contact with the upper ends of the spring pins  260 . 
     The conductor block  240  is fastened to the lower surface of the socket board  220  in the region in which the spring pins  260  are arranged. The conductor block  240  is formed from a conductive material such as metal, and in contact with the inter-layer interconnections  224  formed on the lower surface of the socket board  220  to have the same potential as the inter-layer interconnections  224  formed on the lower surface of the socket board  220 . 
     The spacer  230  surrounds the conductor block  240  to align the conductor block  240 , and serves to flatten the lower surface of the assembly including the socket board  220 , the conductor block  240 , and the spacer  230 . The spacer  230  is electrically conductive, and electrically connected to the inter-layer interconnections  224  formed on the bottom surface of the socket board  220 . On the upper surface of the spacer  230 , a depression  329  is provided to receive a capacitor  229  that is arranged on the lower surface of the socket board  220 . 
     The housing  290  supports the above-described assembly from below, and houses therein connectors  280  and coaxial cables  270 . The connectors  280  are attached to the bottom surface of the housing  290 . When the device-dependent replaceable unit  200  is mounted onto the motherboard  124 , the connectors  280  establish electrical connection with the circuits of the motherboard  124 . 
     The coaxial cables  270  penetrate the conductor block  240 , and electrically connect the lower ends of the spring pins  260  to the connectors  280 . Furthermore, a power supply line  371  and a ground line  372  also electrically connect the inter-layer interconnections  224  to the connectors  280 . Thus, when the device under test  112  is pressed by the handler  110 , the connection terminals  111  are connected to the motherboard  124  via the spring pins  260 , the coaxial cables  270 , and the connectors  280 . 
     Thus, there is provided the device-dependent replaceable unit  200  that is selected depending on the type of the device under test  112 . The device-dependent replaceable unit  200  is to be mounted on the test apparatus  100  to form a signal path between the device under test  112  and the test apparatus  100 . The device-dependent replaceable unit  200  includes the socket board  220  that has a front surface and a back surface, where the device under test  112  is to be moved by the handler  110  close to or away from the front surface of the socket board  220 , and the plurality of spring pins  260  that are positioned in the same manner as the plurality of connection terminals  111  of the device under test  112 , where the spring pins  260  are supported by the socket board  220  in such a manner that upper ends of the spring pins  260  protrude from the front surface of the socket board  220  and come into contact with the connection terminals  111  of the device under test  112 . The device-dependent replaceable unit  200  further includes a socket guide  212  that guides the handler  110 , which holds the device under test  112 , so that the connection terminals  111  of the device under test  112  come into contact with the upper ends of the spring pins  260 . 
       FIG. 3  illustrates the bottom surface of the socket board  220 . The position of this bottom surface in the device-dependent replaceable unit  200  is indicated by the arrow Pin  FIG. 2 . 
     On the bottom surface of the socket board  220 , some of the inter-layer interconnections  224  and the lower ends of the spring pins  260  are externally exposed. On the lower surface of the socket board  220 , the capacitor  229  is also arranged. 
     The inter-layer interconnections  224  are formed on the entire bottom surface of the socket board  20 , excluding the regions immediately adjacent to the spring pins  260 . The lower ends of the spring pins  260  are spaced away from the inter-layer interconnections  224 . Thus, when the spring pins  260  serve as signal paths, the spring pins  260  work together with the inter-layer interconnections  224  to form a distributed constant circuit at least within the plane containing the bottom surface of the socket board  220 . 
       FIG. 4  illustrates a connection structure  201  forming the signal paths in the device-dependent replaceable unit  200 . The signal paths from the device under test  112  mounted on the socket board  220  to the coaxial cables  270  are established by the spring pins  260 . 
     Each spring pin  260  includes a sleeve  264  that is embedded in the socket board  220  so as to penetrate the socket board  220  in the thickness direction, and a contact pin  262  that extends from inside the sleeve  264  to above the socket board  220 . The contact pin  262  can slide in the longitudinal direction within the sleeve  264  and is energized upwards by an energizing member provided in the sleeve  264 . Thus, the contact pin  262  can absorb the height-direction dimensional errors of the device under test  112  and the connection terminals  111 , and be reliably brought into contact with the connection terminals to establish electrical conduction therebetween. 
     The sleeve  264  of the spring pin  260  has an integrally-formed flange  261  at the upper end thereof. Thus, when the sleeve pin is inserted into a through hole formed in the socket board  220  so as to penetrate the socket board  220  in the thickness direction, the spring pin  260  does not go into the socket board  220  more than a certain depth. Furthermore, the flange  261  receives the reaction force that may occur when the connection terminals  111  come into contact with the upper ends of the contact pins  262 , to contribute to form reliable electrical connection between the connection terminals  111  and the contact pins  262 . 
     The flange  261  is pressed against the upper surface of the socket board  220  by the lower surface of the device socket  214 . In this manner, the spring pin  260  is prevented from falling out from the socket board  220 . 
     The lower end of the spring pin  260  slightly protrudes downward from the lower surface of the socket board  220 , and is surrounded and fastened by a fastening member  263 . The fastening member  263  is attached to the spring pin  260  immediately after the spring pin  260  is inserted into the socket board  220 , and temporarily fastens the spring pin  260  until the device socket  214  is mounted on the socket board  220 . 
     The socket board  220  has the inter-layer interconnections  224  that extend in parallel to the front and back surfaces of the socket board  220 , and most of the inter-layer interconnections  224  are arranged within the socket board  220 . The inter-layer interconnections  224  are arranged around the spring pins  260  penetrating the socket board  220 , without contacting the spring pins  260 . The inter-layer interconnections  224  are connected to each other by means of the inter-layer vias  226  that are embedded in the socket board  220  so as to extend in the thickness direction of the socket board  220 . 
     The inter-layer interconnections  224  that are formed on the bottom surface of the socket board  220  are in contact with the conductor block  240 . Thus, within the socket board  220 , the spring pins  260  are each enclosed by a shield that is formed by the inter-layer interconnections  224  and the inter-layer vias  226  at the same potential as the conductor block  240 , to form a coaxial transmission line. 
     The inter-layer interconnections  224  that are arranged within the socket board  220  and forms the shield do not need to be formed all over the socket board  220 . In this case, some of the spring pins  260  may be used for supplying power or the like, and such spring pins  260  may be electrically connected to the inter-layer interconnections  224 . In other words, some of the spring pins  260  and some of the inter-layer interconnections  224  may serve as low-speed signal lines that propagate low-speed signals such as power to be supplied to the device under test  112 . In this case, the spring pins  260  that are electrically connected to the inter-layer interconnections  224  may not need to be connected at the bottom ends thereof to the coaxial cables. 
     Each coaxial cable  270  is constituted by a core line  272  that is positioned at the center in the radial direction of the coaxial cable  270 , a shield line  276  that surrounds the core line  272  with a dielectric  274  therebetween, and an insulator  278  that externally surrounds the shield line  276 . In the portion of the coaxial cable  270  adjacent to the upper end of the coaxial cable  270 , the shield line  276  and the dielectrics  274  and  278  are removed so that the core line  272  is externally exposed. The exposed core line  272  is coupled to the lower end of the spring pin  260 . Stated differently, the exposed core line  272  is pressed into the spring pin  260  through the lower end of the sleeve  264  of the spring pin  260 , so that the coaxial cable  270  is electrically connected to the spring pin  260 . 
     A portion of the coaxial cable  270  that is adjacent to the exposed core line  272  is inserted into the conductor block  240 . This portion of the coaxial cable  270  does not have the outer insulator  278 , so that the shield line  276  is in direct contact with the conductor block  240 . Thus, the coaxial cable  270  is mechanically supported and secured by the conductor block  240 , and the shield line  276  is at the same potential as the conductor block  240 . 
     As already mentioned in the above, the conductor block  240  is connected to the inter-layer interconnections  224 . Furthermore, the inter-layer interconnections  224  and the spring pins  260  together form coaxial structures. Accordingly, coaxial transmission lines extend from the coaxial cables  270  to the upper surface of the socket board  220 . 
     Referring to the above-described connection structure  201 , the portion of the coaxial cable  270  adjacent to the upper end decreases in outer diameter toward the upper end since more materials are removed. Therefore, when the respective components of the device-dependent replaceable unit  200  are assembled together, the coaxial cable  270  can be inserted into the assembly of the socket board  220  and the conductor block  240  from below. 
     Thus, a manufacturing method including inserting the spring pin  260  into the socket board  220  from the front surface, inserting the one end of the coaxial cable  270  into the socket board  220  from the back surface, and electrically coupling the spring pin  260  and the coaxial cable  270  to each other can manufacture the device-dependent replaceable unit  200  that is selected depending on the type of the device under test  112 . The device-dependent replaceable unit  200  is to be mounted on the test apparatus  100  to form a signal path between the device under test  112  and the test apparatus  100 . The device-dependent replaceable unit  200  includes the socket board  220  that has a front surface and a back surface, the spring pin  260  that is embedded in the socket board  220  in such a manner that the upper end of the spring pin  260  protrudes from inside of the socket board  220  to the front surface of the socket board  220 , and the coaxial cable  270  one end of which is connected to the lower end of the spring pin  260 , where the coaxial cable  270  extending from the back surface of the socket board  220  to the motherboard  124 . 
       FIG. 5  is a vertical sectional view illustrating the configuration of a different embodiment of the device-dependent replaceable unit  200 . The device-dependent replaceable unit  200  is structured by sequentially layering a socket board  220 , a spacer  230 , a conductor block  240 , and a housing  290 . Some of the constituents are shared between the present embodiment and the embodiment described with reference to  FIGS. 1 to 4 . Such constituents are designated by the same reference numbers and are not redundantly explained here. 
     The socket board  220  includes an insulation layer  222 , inter-layer interconnections  224  and inter-layer vias  226 , and through vias  228 . On the upper surface of the socket board  220 , a socket guide  212  and a device socket  214  are mounted. 
     The device socket  214  has therein a plurality of through holes  211  that are positioned in the same manner as connection terminals  111  of a device under test  112 . In the through holes  211 , connection members  213  are placed which have elasticity in the direction in which the through holes  211  extend. The connection members  213  are, for example, contact pins. 
     The socket guide  212  has members that guide the pins of the handler  110 , which holds the device under test  112 . Thus, the connection terminals  111  of the device under test  112  that is held by the handler  110  are brought into contact with the upper ends of the connection members  214  within the through holes  211 . 
     Some of the inter-layer interconnections  224  are formed on the lower surface of the socket board  220 . The inter-layer interconnections  224  are electrically connected to each other by means of the inter-layer vias  226 . 
     The through vias  228  penetrate the socket board  220  in the thickness direction. At the respective ends of each through via  228 , flat pads  227  are provided. The through vias  228  are electrically isolated from the inter-layer interconnections  224  and the inter-layer vias  226 . On the upper surface of the socket board  220 , the pads  227  are positioned in the same manner as the connection members of the device socket  210 . 
     The conductor block  240  is secured to the lower surface of the socket board  220  in the region in which the through vias  228  are arranged. The conductor block  240  is formed from a conductive material such as metal, and has the same potential as the inter-layer interconnections  224  formed on the lower surface of the socket board  220  by contacting the inter-layer interconnections  224  formed on the lower surface of the socket board  220 . 
     Spring pins  260  are embedded in the conductor block  240  and surrounded by dielectrics  250 . The spring pins  260  are positioned in the same manner as the pads  227  arranged on the lower surface of the socket board  220 . The upper ends of the spring pins  260  are in contact with the lower end surfaces of the through vias  228 . 
     The spacer  230  surrounds the conductor block  240  to align the conductor block  240 , and serves to flatten the lower surface of the assembly including the socket board  220 , the conductor block  240 , and the spacer  230 . 
     The housing  290  supports the above-described assembly from below, and houses therein connectors  280  and coaxial cables  270 . The connectors  280  are attached to the bottom surface of the housing  290 . When the device-dependent replaceable unit  200  is mounted onto the motherboard  124 , the connectors  280  establish electrical connection with the circuits of the motherboard  124 . 
     The coaxial cables  270  are coupled to the lower ends of the spring pins  260  within the conductor block  240 . Thus, the connection terminals  111  of the device under test  112 , which is mounted on the device socket  210 , are connected to the motherboard  124  through the connection members  214 , the through vias  228 , the spring pins  260 , the coaxial cables  270  and the connectors  280 . 
     Thus, there is provided the device-dependent replaceable unit  200  that is selected depending on the type of the device under test  112 . The device-dependent replaceable unit  200  is to be mounted on the test apparatus  100  to form a signal path between the device under test  112  and the test apparatus  100 . The device-dependent replaceable unit  200  includes the socket board  220  that includes the plurality of through vias  228  penetrating therethrough, where the through vias  228  are positioned in the same manner as the connection terminals on the back surface of the device socket  210  that has the connection members  214  for the device under test  112 , and the device socket  210  is to be mounted on the front surface of the socket board  220 , the conductor block  240  that is secured onto the back surface of the socket board  220 , the spring pin  260  that is embedded in the conductor block  240  in such a manner that the upper end of the spring pin  260  protrudes from inside of the conductor block  240  to the back surface of the socket board  220  and comes into contact with the end surfaces of the through vias  228  at the back surface of the socket board  220 , and the coaxial cable one end of which is connected to the lower end of the spring pin  260 , where the coaxial cable extends from the back surface of the conductor block  240  toward the test apparatus. 
       FIG. 6  illustrates the bottom surface of the socket board  220 . The position of the bottom surface in the device-dependent replaceable unit  200  is indicated by the arrow P in  FIG. 5 . The arrow A in  FIG. 5  indicates the direction in which the bottom surface is looked up. 
     On the bottom surface of the socket board  220 , the undermost inter-layer interconnections  224 , the pads  227  formed at the lower ends of the through vias  228 , and the lower ends of the inter-layer vias  226  are seen. The inter-layer interconnections  224  are formed on the entire bottom surface of the socket board  220 , excluding the regions immediately adjacent to the pads  227 . The end surfaces of the inter-layer vias  226  are seen in the region in which the inter-layer interconnections  224  are formed. 
     The pads  227  formed on the lower ends of the through vias  228  are spaced away from the inter-layer interconnections  224 . Thus, when the through vias  228  serve as signal paths, the pads  227  work together with the inter-layer interconnections  224  to form a distributed constant circuit at least within the plane containing the bottom surface of the socket board  220 . 
       FIG. 7  illustrates the upper surface of the conductor block  240 . The position of the upper surface is indicated by the arrow Pin  FIG. 5 . The arrow B in  FIG. 5  indicates the direction in which the upper surface is looked down. 
     When the upper surface of the conductor block  240  is looked down, the spring pins  260  are seen which are embedded in the conductor block  240 . Also, the dielectrics  250  are seen which are provided between the conductor block  240  and the spring pins  260 . Thus, when the spring pins  260  serve as signal paths, the spring pins  260  work together with the conductor block  240  to form a distributed constant circuit at least within the plane containing the upper surface of the conductor block  240 . The distributed constant is maintained over substantially the entire length of the spring pins  260 . 
       FIG. 8  is a horizontal sectional view illustrating the bottom surface of the conductor block  240 . The position of the bottom surface in the device-dependent replaceable unit  200  is indicated by the arrow R in  FIG. 5 . The arrow C in  FIG. 5  indicates the direction in which the bottom surface is looked up. 
     On the bottom surface of the conductor block  240 , the transverse sectional surfaces of the coaxial cables  270 , which are inserted into the conductor block  240 , are seen. It is also seen that the outer insulators  278  are removed from the coaxial cables  270  and the shield lines  276  are thus in contact with the conductor block  240 . This indicates that the shield lines  276  of the coaxial cables  270  are at the same potential as the conductor block  240 . This state is always maintained as long as the shield lines  276  are in contact with the conductor block  240 . 
       FIG. 9  illustrates an electrical connection structure  201  between the socket board  220  and the coaxial cables  270  in the device-dependent replaceable unit  200 . Some of the constituents are shared between the present embodiment and different embodiments shown in different drawings, and such constituents are designated by the same reference numerals and not redundantly explained here. 
     The socket board  220  has the inter-layer interconnections  224  that are formed in parallel to the front and back surfaces of the socket board  220 . The inter-layer interconnections  224  are connected to each other by means of the inter-layer vias  226  that extend in the thickness direction of the socket board  220 . Note that, however, the inter-layer interconnections  224  are not in contact with through vias  228 . Thus, within the socket board  220 , the through vias  228  are each enclosed by a shield that is formed by the inter-layer interconnections  224  and the inter-layer vias  226 , to form a coaxial transmission line. 
     The inter-layer interconnections  224  that are arranged within the socket board  220  and form the shield may not need to be formed all over the socket board  220 . In this case, some of the through vias  228  may be used for supplying power or the like, and such through vias  228  may be electrically connected to the inter-layer interconnections  224 . In other words, some of the through vias  228  and some of the inter-layer interconnections  224  may serve as low-speed signal lines that propagate low-speed signals such as power to be supplied to the device under test  112 . In this case, the through vias  228  that are electrically connected to the inter-layer interconnections  224  may not need to be connected at the bottom ends thereof to the spring pins  260 . 
     The inter-layer interconnections  224  that are formed on the bottom surface of the socket board  220  are in contact with the conductor block  240 . The spring pins  260 , which are embedded in the conductor block  240 , are energized upwards so that the upper ends of the spring pins  260  are pressed against the pads  227 . In this manner, electrical connection is established between the through vias  228  of the socket board  220  and the spring pins  260 . 
     The dielectrics  250  are provided between the spring pins  260  and the conductor block  240 , in which the spring pins  260  are embedded. The dielectrics  250  also cover the lower surfaces of the spring pins  260  and block electrical conduction between the spring pins  260  and the conductor block  240 . Thus, the conductor block  240  and the spring pins  260  form coaxial structures. Since the dielectrics  250  are open at the upper ends, the spring pins  260  can be inserted from above. 
     In the portion of each coaxial cable  270  adjacent to the upper end of the coaxial cable  270 , the shield line  276  and the dielectrics  274  and  278  are removed, so that the core line  272  is externally exposed. The exposed core line  272  is pressed into the spring pin  260  through the lower end of the sleeve  264  of the spring pin  260 , so that electrical connection is established between the coaxial cable  270  and the spring pin  260 . 
     A portion of the coaxial cable  270  that is adjacent to the exposed core line  272  is inserted into the conductor block  240 . This portion of the coaxial cable  270  does not have the outer insulator  278 , so that the shield line  276  is in direct contact with the conductor block  240 . Thus, the coaxial cable  270  is mechanically supported and secured by the conductor block  240 , and the shield line  276  is at the same potential as the conductor block  240  and the inter-layer interconnections  224 . Thus, a coaxial transmission line is formed from the coaxial cable  270  to the upper surface of the socket board  220 . 
     Referring to the above-described connection structure  201 , the portion of the coaxial cable  270  adjacent to the upper end of the coaxial cable  270  decreases in outer diameter toward the upper end since more materials are removed. Therefore, when the respective components of the device-dependent replaceable unit  200  are assembled together, the coaxial cable  270  can be inserted into the conductor block  240  from below. 
     Thus, a manufacturing method including inserting the spring pin  260  into the conductor block  240  from the front surface, inserting the one end of the coaxial cable  270  into the conductor block  240  from the back surface, and electrically coupling the spring pin  260  and the coaxial cable  270  to each other can be used to manufacture the device-dependent replaceable unit  200  that is selected depending on the type of the device under test  112 . The device-dependent replaceable unit is to be mounted on the test apparatus  100  to form a signal path between the device under test  112  and the test apparatus  100 . The device-dependent replaceable unit includes the conductor block  240 , the spring pin  260  that is embedded in the conductor block  240  in such a manner that the upper end of the spring pin  260  protrudes from inside of the conductor block  240  to the front surface of the conductor block  240 , and the coaxial cable  270  one end of which is connected to the lower end of the spring pin  260 , the coaxial cable  270  extending from the back surface of the conductor block  240  to the motherboard  124 . 
     As described above, the signal path extending from the motherboard  124  to the device under test  112  largely has a coaxial structure due to the device-dependent replaceable unit  200 . This can achieve impedance match in the signal path and reduce the attenuation of the transferred signal. In addition, unnecessary electromagnetic radiation and crosstalk caused by the transferred signal is suppressed. Therefore, the device-dependent replaceable unit  200  can be advantageously used, in particular, in a test apparatus for testing a high-frequency semiconductor device. When the connection terminals  111  of the device under test  112  are arranged at extremely small intervals and the coaxial cables  270  cannot be arranged at the same intervals as the connection terminals  111 , each pair of adjacent lines may be combined to form a twin-lead balanced transmission line. 
     While an aspect of the present invention has been described based on some embodiments, the technical scope of the invention is not limited to the above described embodiments. It is apparent to persons skilled in the art that various alterations and improvements can be added to the above-described embodiments. It is also apparent from the scope of the claims that the embodiments added with such alternations or improvements can be included in the technical scope of the invention. 
     The operations, procedures, steps, and stages of each process performed by an apparatus, system, program, and method shown in the claims, embodiments, or diagrams can be performed in any order as long as the order is not indicated by “prior to,” “before,” or the like and as long as the output from a previous process is not used in a later process. Even if the process flow is described using phrases such as “first” or “next” in the claims, embodiments, or diagrams, it does not necessarily mean that the process must be performed in this order.