In order to adjust the posture of the wiring substrate in the inspection apparatus for bringing a plurality of probe pins into uniform and individual contact with the large number of electronic components, the wiring substrate has studs, each having a bolt, joined to its back surface opposite its front surface having pads for probe into which the probe pins are to be implanted, in such a manner that the bolts become perpendicular to the back surface. For example, regarding the case where via conductors (conductors for connection between adjacent layers) are located on the back surface to which the studs are joined, at positions around the studs, in order for the substrate to be less susceptible to occurrence of cracking in the vicinity of the via conductors even in the event of application of a large external force to the studs, there have been proposed a multilayer ceramic substrate for which various dimensions such as the distance between the center axis of the via conductor and the circumcircle of a brazing material layer used to join the stud to a surface metal layer formed on the back surface are specified as appropriate, as well as a method of manufacturing the multilayer ceramic substrate (see, for example, Patent Document 1).
However, the multilayer ceramic substrate and the method of manufacturing the same have involved the following potential problem in an attempt to meet a request for implementation of fine pitch: a short circuit may be accidentally formed between an external connection terminal connected to the back surface of the via conductor and the circumcircle (outer circumferential edge) of the brazing material layer used to join the stud to the surface metal layer formed on the back surface of the substrate.
Also, the use of a resin adhesive for joining the stud has involved the following potential problem: since the length of protrusion of the resin adhesive from the stud cannot be sufficiently controlled, the protruding resin adhesive may possibly cover a portion of the external connection terminal, potentially resulting in a failure to electrically connect the external connection terminal to an external electrode or the like.
Further, in the case where the wiring substrate for electronic component inspection apparatus has a structure in which a plurality of resin insulation layers are laminated with a plurality of pads for probe provided on the front surface of the laminate, and a plurality of ceramic layers are laminated on the back side of the laminate of the resin insulation layers, the following potential problem has been involved: when the studs are joined by brazing to respective metal layers provided on the back surface of the outermost ceramic layer, resin of the resin insulation layers may possibly deform as a result of softening or melting.