Abstract:
An electrical connecting device includes a supporting substrate, a plate spring arranged on the supporting substrate, an assembling device for assembling the plate spring to the supporting substrate, a block having a mounting surface facing down, and a flexible circuit board whereupon a plurality of contacts are formed. The block has the mounting surface which protrudes downward from the supporting substrate, for mounting the circuit board. The plate spring is applied with an initial load to be in a status where at least a center region whereupon the block is mounted is urged upward. Thus, excellent electric contact status can be obtained without increasing an over drive quantity.

Description:
PRIORITY CLAIM 
       [0001]    The present application is a United States national phase application filed pursuant to 35 USC §371 of International Patent Application Serial No. PCT/JP2007/065787, entitled ELECTRICAL CONNECTING DEVICE, filed Aug. 6, 2007; which application claims priority to Japanese Patent Application Serial No. 2006-263811, filed Sep. 28, 2006; which foregoing applications are incorporated herein by reference in their entireties. 
       CROSS REFERENCE TO RELATED APPLICATIONS 
       [0002]    This application is related to U.S. patent application Ser. No. 12/296,430 entitled ELECTRICAL CONNECTING APPARATUS, filed Oct. 7, 2008, and U.S. application Ser. No. 12/297,214 entitled FLEXIBLE WIRING BOARD AND ELECTRICAL CONNECTING APPARATUS, filed Oct. 14, 2008 and application Ser. No. 12/297,215 entitled PROBE SHEET AND ELECTRICAL CONNECTING APPARATUS, filed Oct. 14, 2008 and application Ser. No. 12/297,216 entitled METHOD FOR MANUFACTURING PROBE SHEET, filed Oct. 14, 2008 and which are incorporated herein by reference in their entireties. 
     
    
     TECHNICAL FIELD 
       [0003]    An embodiment of the present invention relates to an electrical connecting apparatus for use in an electrical test of a flat-plate-shaped device under test such as an integrated circuit or a board for a display. 
       BACKGROUND 
       [0004]    A flat-plate-shaped device under test such as an integrated circuit or a display board undergoes an electrical test with use of an electrical connecting apparatus such as a probe card. In the electrical test, the device under test is thrust by contactors of the electrical connecting apparatus at its electrodes and is powered in such a state. 
         [0005]    As one of the electrical connecting apparatuses of this kind, there is an art of using a flexible circuit board having a flexible sheet-like member such as an FPC in which a flexible electrical insulating sheet is provided with a plurality of wires, and a plurality of contactors soldered to the respective wires of this sheet-like member (Patent Document 1). 
         [0006]    Patent Document 1: Japanese Unexamined Patent Publication No. 2002-311049, which is incorporated by reference. 
         [0007]    In the above conventional art, each contactor comprises a pedestal portion coupled with the wire at one end portion, an arm portion extending from the other end of the pedestal portion in the longitudinal direction of the wire, and a probe tip portion protruded from the tip end of the arm portion to a side opposite the pedestal portion. The arm portion and the probe tip portion act as a main body portion that is elastically deformed substantially at the arm portion when the tip end of the probe tip portion, that is, the probe tip, is thrust to an electrode of a device under test. 
         [0008]    The circuit board using such contactors is attached to a support board such as a wiring board by an attachment device so that the probe tip portions can be directed to the device under test, thus to be assembled into an electrical connecting apparatus. 
         [0009]    The attachment device comprises a plate-shaped member arranged on the upper surface of the support board, a ring-shaped member arranged in a step portion directing downward provided at the center of the support board so as to be located at the step portion, a plate spring screwed on the lower side of the ring-shaped member, and a block having at least an attachment surface on the lower side, located on the lower side of the plate spring in a state where the attachment surface is protruded in the downward direction of the support board, and screwed in the ring-shaped member. 
         [0010]    The plate-shaped member is attached to the support board by a plurality of attachment screws penetrating the plate-shaped member and the support board in the up-down direction and screwed in the ring-shaped member and attaches the ring-shaped member to the support board. The plate spring is kept in parallel with the support board. 
         [0011]    The aforementioned circuit board is bonded to the attachment surface of the block at a contactor area at which the contactors are arranged and is attached to the lower surface of the support board by a ring-shaped spring holder and a plurality of locking screws at an outermost circumferential portion of an outer area surrounding this contactor area. 
         [0012]    After the above electrical connecting apparatus is attached to a testing apparatus such as a prober, the probe tip of each contactor is thrust to the electrode of the device under test so that predetermined probe pressure acts on the electrode and the probe tip, and a desired contactor is powered in a state where predetermined overdriving acts on each contactor. By doing so, an electrical test is conducted. 
         [0013]    When an imaginal probe tip surface formed by all the probe tips is inclined to the support board or the testing apparatus (device under test), the arm portion of each contactor and the plate spring are elastically deformed since the probe tip is thrust to the device under test. Accordingly, the contactor area and the probe tip surface are automatically compensated to be parallel to the support board. 
         [0014]    However, in the conventional electrical connecting apparatus, since the plate spring is kept in parallel with the support board in a state where the probe tip of each contactor is not thrust to the electrode of the device under test, the probe pressure and the overdriving amount are proportional to each other. 
         [0015]    Thus, in the conventional electrical connecting apparatus, the damage given to the contactor and the electrode increases when the overdriving amount is large, while the probe pressure may be too small to obtain a good electrical contacting state between the probe tip and the electrode when the overdriving amount is small. 
       SUMMARY 
       [0016]    An embodiment of the present invention obtains a good electrical contacting state without increasing the overdriving amount. 
         [0017]    An electrical connecting apparatus according to an embodiment of the present invention comprises a support board having an upper surface and a lower surface, a plate spring arranged on the support board, an attachment device for attaching the plate spring to the support board, a block having an attachment surface directed downward and attached to the lower side of the plate spring in a state where at least the attachment surface is protruded further to the lower side than the support board, and a flexible circuit board having a contactor area in which a plurality of contactors are arranged and an outside area around the contactor area and attached at part of the outside area to the lower surface of the support board in a state where at least the contactor area is opposed to the attachment surface of the block. 
         [0018]    The plate spring has a center area to which the block is attached, and receives initial load to bring a state where at least the center area is biased toward the upper side of the support board. 
         [0019]    The plate spring may further have a plurality of extending areas integrally continuing to the center area and extending from the center area in the radial direction of an imaginal circle to be spaced in the circumferential direction of the imaginal circle, and a circumferential area integrally continuing around the extending areas and supported to the attachment device. 
         [0020]    The attachment device may have a ring-shaped member arranged on the support board so that at least its part is opposed to part of the plate spring, and a spring holder attached to the ring-shaped member so as to sandwich part of the plate spring in collaboration with the ring-shaped member. 
         [0021]    The spring holder may have an annular portion screwed on the ring-shaped member so as to sandwich a part of the plate spring in collaboration with the ring-shaped member and an inward flange portion extending from the lower end portion of the annular portion to the center side of the annular portion, and the block may have a lower block portion having the attachment surface, an upper block portion protruded upward from the lower block portion and attached to the plate spring, and an outward flange portion extending outward in the radial direction from the upper block portion and located on the upper side of the inward flange portion. 
         [0022]    The distance dimension from the upper end of the annular portion to the upper end of the inward flange portion may be shorter than the distance dimension from the upper end of the upper block portion to the lower end of the outward flange portion. 
         [0023]    The attachment device may further have an attachment plate attached to the upper side of the upper block portion via the plate spring so as to sandwich the center area of the plate spring in collaboration with the upper block portion. 
         [0024]    The support board may have a through hole at the center, and the plate spring may be attached to the support board so as to be located within the through hole or to be opposed to the through hole. 
         [0025]    The attachment device may further have a plate-shaped member attached to the upper side of the support board so as to close the through hole, and the ring-shaped member may be attached to the lower side of the plate-shaped member. 
         [0026]    The electrical connecting apparatus may further comprise a thrusting ring for attaching the outside area of the circuit board to the lower surface of the support board. 
         [0027]    The spring constant of the plate spring may be smaller than the total sum of the spring constant of the contactors. 
         [0028]    According to an embodiment of the present invention, since the plate spring receives initial load to bring a state where at least the center area is biased toward the upper surface side of the support board, the probe pressure acting on the probe tip of each contactor and the electrode of the device under test comes under the influence of not only reactive force by elastic deformation of the contactor and the plate spring when the probe tip is thrust to the electrode of the device under test but also reactive force based on elastic deformation of the plate spring by the initial load. Thus, according to an embodiment of the present invention, a good electrical contacting state can be obtained without increasing the overdriving amount. 
         [0029]    In a case where the plate spring further has a plurality of extending areas integrally continuing to the center area and extending from the center area in the radial direction of an imaginal circle to be spaced in the circumferential direction of the imaginal circle and a circumferential area integrally continuing around the extending areas and supported to the attachment device, the plate spring is elastically deformed at the extending areas reliably when the probe tips are thrust to the electrodes, and thus irregular flexure of the plate spring is prevented reliably. 
         [0030]    In a case where the spring holder has an inward flange portion extending from the lower end portion of an annular portion to the center side of the annular portion screwed on the ring-shaped member so as to sandwich part of the plate spring in collaboration with the ring-shaped member, where the block has an outward flange portion extending outward in the radial direction from an upper block portion protruded upward from its lower block portion and attached to the plate spring, and where the outward flange portion of the block is located on the upper side of the inward flange portion of the spring holder, the plate spring can receive the initial load reliably without preventing displacement of the block in the up-down direction when the probe tips are thrust to the electrodes. 
         [0031]    In a case where the distance dimension from the upper end of the annular portion to the upper end of the inward flange portion of the spring holder is shorter than the distance dimension from the upper end of the upper block portion to the lower end of the outward flange portion of the block, the plate spring is kept in a state of receiving the initial load reliably. 
         [0032]    In a case where the attachment device further has an attachment plate attached to the upper side of the upper block portion via the plate spring so as to sandwich the center area of the plate spring in collaboration with the upper block portion, the block is attached to the plate spring reliably. 
         [0033]    In a case where the attachment device further has a plate-shaped member attached to the upper side of the support board so as to close the through hole, and where the ring-shaped member is attached to the lower side of the plate-shaped member, the plate spring is supported on the support board in a stable state. 
         [0034]    In a case where the electrical connecting apparatus further comprises a thrusting ring for attaching the outside area of the circuit board to the lower surface of the support board, the circuit board is supported on the support board at its outside area. 
         [0035]    In a case where the spring constant of the plate spring is smaller than the total sum of the spring constant of all the contactors, when the overdriving acts on the contactors, only the contactors are elastically deformed until the overdriving amount is one in which the initial load by the preload acting on the plate spring and the total sum of the spring constant of all the contactors are at equilibrium, and thereafter the plate spring is elastically deformed mainly although the contactors are also elastically deformed. Thus, the probe pressure increases significantly in reaction to the overdriving in a state where only the contactors are elastically deformed (in a state of the initial load) and thereafter increases moderately. Consequently, variation of the probe pressure by the overdriving is small, and stable electrical contact can be obtained. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0036]      FIG. 1  is an exploded perspective view showing an embodiment of an electrical connecting apparatus according to an embodiment of the present invention. 
           [0037]      FIG. 2  is a plan view of the electrical connecting apparatus shown in  FIG. 1 . 
           [0038]      FIG. 3  is a cross-sectional view obtained along the line  3 - 3  in  FIG. 2 . 
           [0039]      FIG. 4  is a bottom view of the electrical connecting apparatus shown in  FIG. 1 . 
           [0040]      FIG. 5  is a bottom view of the electrical connecting apparatus shown in  FIG. 1  in a state where a circuit board and a thrusting plate have been removed. 
           [0041]      FIG. 6  is an exploded perspective view showing an embodiment of a ring-shaped member, a plate spring, and a spring holder. 
           [0042]      FIG. 7  is a perspective view showing an embodiment of a block. 
           [0043]      FIG. 8  is a perspective view showing a state where the circuit board has been attached to the block. 
           [0044]      FIG. 9  is an enlarged bottom view of the contactor area of the circuit board and its perimeter. 
           [0045]      FIG. 10  is a plan view showing an embodiment of the circuit board. 
           [0046]      FIG. 11  is a cross-sectional view obtained along the line  11 - 11  in  FIG. 9 . 
           [0047]      FIG. 12  is an enlarged cross-sectional view showing an attachment state of the circuit board to a support board. 
           [0048]      FIG. 13  is an enlarged cross-sectional view showing a joining relationship between a flange portion of the block and a flange portion of the spring holder. 
           [0049]      FIG. 14  shows variation of the probe pressure per contactor when overdriving acts on the contactor. 
       
    
    
     DESCRIPTION OF THE SYMBOLS 
       [0000]    
       
           10 : electrical connecting apparatus 
           12 : support board 
           14 : plate-shaped member 
           16 : ring-shaped member 
           18 : plate spring 
           20 : block 
           22 : circuit board 
           24 : reference mark member 
           26 : adjustment screw 
           28 : through hole 
           30 : tester land 
           32 : connection land 
           34 : screw member 
           36 : attachment screw 
           38 : center area of the plate spring 
           39 : extending area of the plate spring 
           40 : circumferential area of the plate spring 
           42 : spring holder 
           44 : screw member 
           46 : holding piece 
           46 : a arc portion forming an annular portion 
           46   b : extending portion forming an inward flange portion 
           48 : flat area 
           50 : attachment surface of the block 
           51 : intermediate surface of the block 
           52 : slope of the block 
           54 : lower block portion 
           56 : attached surface of the block 
           58 : upper block portion 
           59 : outward flange portion 
           60 : attachment plate 
           62 : screw member 
           64 : recess of the block 
           66 : groove of the block 
           70 : sheet 
           70   a ,  70   b ,  70   c : sheet members 
           72 : conductive path 
           74 : contactor 
           76 : contactor area of the circuit board 
           78 : outside area of the circuit board 
           80 : intermediate area of the circuit board 
           82 : extending portion of the circuit board 
           84 : connection bump 
           86 : plate 
           88 : pedestal portion of the contactor 
           88   a ,  88   b : first and second seat portions 
           90 : main body portion of the contactor 
           90   a : arm portion 
           90   b : probe tip portion 
           92 : adhesive 
           94 : rubber ring 
           96 : thrusting ring 
           100 : positioning pin 
           102 : reference mark 
       
     
       DETAILED DESCRIPTION 
       [0104]    In an embodiment of the present invention, in  FIG. 1 , the right-left direction is referred to as an X direction or a right-left direction, the front-back direction is referred to as a front-back direction or a Y direction, and the up-down direction is referred to as an up-down direction or a Z direction. However, these directions differ depending on the posture in which a device under test is arranged in a testing apparatus, that is, the posture of the device under test arranged in the testing apparatus. 
         [0105]    Accordingly, as for the above directions, the X direction and the Y direction may be determined to be within any one plane of a horizontal plane, an inclined surface inclined to the horizontal plane, and a vertical plane vertical to the horizontal plane or may be determined to be a combination of these planes in accordance with an actual testing apparatus. 
         [0106]    An embodiment of an electrical connecting apparatus  10  is used in an electrical test of a rectangular integrated circuit (not shown) in a similar manner as a probe card. The integrated circuit has a plurality of electrodes. These electrodes are arrayed in two lines to be spaced in the right-left direction (or the front-back direction) in the example of a test performed in the connecting apparatus shown in  FIG. 9 . 
         [0107]    Referring to  FIGS. 1 to 12 , the electrical connecting apparatus  10  includes a disk-shaped support board  12 , a plate-shaped member  14  attached to the upper surface of the support board  12 , a plate-shaped ring-shaped member  16  arranged on the lower side of the plate-shaped member  14 , a plate spring  18  arranged on the lower side of the ring-shaped member  16 , a table or a block  20  attached to the lower surface of the plate spring  18 , a film-shaped board or a circuit board  22  arranged on the lower side of the block  20 , plural reference mark members  24  attached to the block  20 , and a plurality of adjustment screws  26  (refer to  FIGS. 2 and 3 ) penetrating the plate-shaped member  14  in its thickness direction and fitting to the aforementioned ring-shaped member  16 . 
         [0108]    The support board  12  has a through hole  28  passing through its center in the thickness direction (up-down direction), has at the circumferential portion on the upper surface a plurality of tester lands  30  (refer to  FIG. 2 ) connected to a tester, and has on the lower surface in an area between the through hole  28  and the outer portion a plurality of connection lands  32  (refer to  FIGS. 5 and 12 ) to be spaced in the circumferential direction. The through hole  28  has a circular flat plane shape. 
         [0109]    The support board  12  also has inside a plurality of wires (conductive paths) respectively connecting the tester lands  30  and the connection lands  32  in one-to-one relationship. Such a support board  12  may be a wiring board made of epoxy resin containing glass or a ceramic material. 
         [0110]    The plate-shaped member  14  is formed in a disk shape larger than the through hole  28  and is attached to the upper surface of the support board  12  by a plurality of screw members  34  penetrating the plate-shaped member  14  and screwed in the support board  12  in a state of blocking the through hole  28 , that is, in parallel with the support board  12 . 
         [0111]    The plate-shaped member  14  is made of a metal material such as stainless steel so as to act as a reinforcing plate for the support board  12 . Thus, the plate-shaped member  14  does not need to be a complete plate but may be one formed in a plate shape consisting of a flat center portion, a plurality of extending portions extending from this center portion in the radial direction of an imaginal circle to be spaced in the circumferential direction of the imaginal circle, and an outer portion connected to the tip ends of these extending portions and extending in the circumferential direction of the imaginal circle, as the plate spring  18  described later. 
         [0112]    As shown in  FIG. 6 , the ring-shaped member  16  is also formed in a plate-shaped ring shape made of a metal material such as stainless steel, especially a metal material having a small thermal expansion coefficient, and having a slightly smaller outer dimension than the diameter dimension of the through hole  28 , and is located in the through hole  28  of the support board  12 . 
         [0113]    The ring-shaped member  16  is attached to the lower surface of the plate-shaped member  14  in parallel with the support board  12  and the plate-shaped member  14  by a plurality of attachment screws  36  penetrating the plate-shaped member  14  in its thickness direction and screwed in the ring-shaped member  16 . 
         [0114]    As shown in  FIG. 6 , the plate spring  18  has a flat center area  38 , a plurality of plate-shaped extending areas  39  extending from the center area  38  in the radial direction of an imaginal circle to be spaced in the circumferential direction of the imaginal circle, and a ring-shaped circumferential area  40  integrally continuing around the extending areas  39 . 
         [0115]    The center area  38  and the extending areas  39  are formed in a star (*) shape. The number of the extending areas  39  may be an appropriate value such as four, six, eight, or the like. In the example shown in the figures, the number of the extending areas  39  is four, and thus the center area  38  and the extending areas  39  are in a cross shape crossing at the center area  38 . 
         [0116]    The plate spring  18  is made of a material selected from a group including tungsten, molybdenum, their alloy, and a ceramic material, having a smaller thermal expansion coefficient than that of stainless steel. 
         [0117]    The plate spring  18  is attached at the circumferential area  40  to the lower surface of the ring-shaped member  16  by a spring holder  42  and a plurality of screw members  44  penetrating the plate spring  18  and the spring holder  42  from the lower side and screwed in the ring-shaped member  16 . 
         [0118]    Accordingly, the plate spring  18  is supported on the support board  12  via the plate-shaped member  14  in a stable state so as to close the through hole  28  of the support board  12  in a state of being sandwiched between the ring-shaped member  16  and the spring holder  42 . 
         [0119]    In the example shown in the figures, the spring holder  42  consists of a plurality of holding pieces  46 . These holding pieces  46  are combined to one another so as to collaboratively form an annular portion screwed on the ring-shaped member  16  to bring a state of being thrust to the circumferential area  40  of the plate spring  18  and a rectangular (or circular) inward flange portion extending from the lower end portion of this annular portion to the center side of the annular portion. 
         [0120]    Thus, each holding piece  46  has an arc portion  46   a  forming the aforementioned annular portion and an extending portion  46   b  forming the aforementioned flange portion in collaboration with the other holding pieces  46 . However, the spring holder  42  may be formed by a ring-shaped single member or halved member having the aforementioned annular portion and the aforementioned flange portion. 
         [0121]    As shown in  FIGS. 6 and 11 , as for the inner surfaces of the ring-shaped member  16  and the annular portion of the spring holder  42 , portions corresponding to the boundaries between the extending areas  39  and the circumferential area  40  of the plate spring  18  are a plurality of flat areas  48  extending in the tangential direction of the outer circumference surface of the plate spring  18  and in the up-down direction. 
         [0122]    At least the plate-shaped member  14 , the ring-shaped member  16 , and the spring holder  42  act as an attachment device for attaching the plate spring  18  to the support board  12 . 
         [0123]    As shown in  FIG. 7 , the block  20  comprises a lower block portion  54  having a truncated polygonal pyramidal downward surface formed by an attachment surface  50  to which the circuit board  22  is to be attached, an intermediate surface  51  continuing into the perimeter of the attachment surface  50 , and a plurality of slopes  52  continuing into the perimeter of the intermediate surface  51 , a prismatic upper block portion  58  whose upper end surface is an attached surface  56  to the plate spring  18 , and an outward flange portion  59  extending outward in the radial direction from the upper block portion  58 . 
         [0124]    In the example shown in the figures, the shape of the upper block  58  is a quadrangular prism, and the shape of the attached surface  56  is a quadrangle. Also, the attachment surface  50 , the intermediate surface  51 , and the attached surface  56  are parallel surfaces, and the downward surface of the lower block portion  54  is formed in a truncated octagonal pyramidal shape. The flange portion  59  is formed in a rectangular (or circular) shape opposed to the inward flange portion consisting of the extending portions  46   b  of the spring holder  42 . 
         [0125]    The block  20  is attached to the lower surface of the center area  38  of the plate spring  18  at the upper block portion  58  by a plurality of screw members  62  in a state where the center area  38  of the plate spring  18  is sandwiched between a rectangular attachment plate  60  and the upper block portion  58  and in a state where at least the attachment surface  50  is protruded in the downward direction of the support board  12 . By doing so, the block  20  is kept in a state of being attached to the plate spring  18 . 
         [0126]    As shown in  FIG. 11 , as for the lower end portion of the lower block portion  54 , the attachment surface  50  is slightly protruded downward more than the intermediate surface  51  around the attachment surface  50 . At the lower end portion of the lower block portion  54  are formed a recess  64  opened at the attachment surface  50  and a downward groove  66  extending around the recess  64 . 
         [0127]    As shown in  FIGS. 8 to 13 , the circuit board  22  has an electrical insulating sheet  70  such as polyimide in which a plurality of stripped wires or conductive paths  72  is formed inside thereof, and a contactor  74  equipped to each conductive path  72 . Thus, the circuit board  22  has flexibility. The sheet  70  is constituted by three sheet members  70   a ,  70   b , and  70   c.    
         [0128]    The circuit board  22  has a rectangular contactor area  76  in which the contactors  74  are arranged and an outside area  78  around the contactor area  76 . The outside area  78  comprises an intermediate area  80  integrally continuing into the perimeter of the contactor area  76  and a plurality of extending portions  82  extending from the intermediate area  80  in the radial direction of an imaginal circle centering around the contactor area  76  to be spaced around the intermediate area  80 . 
         [0129]    Each conductive path  72  extends from the inside of the contactor area  76  in which the contactors  74  are arranged to the outside area  78  outward in the radial direction of the aforementioned imaginal circle. At the outside end portion of each conductive path  72  is provided connection bumps  84  (refer to  FIG. 12 ) penetrating the sheet members  70   b  and  70   c  and protruded upward. In the example shown in the figures, each conductive path  72  is in a three-layered structure of copper, nickel, and copper. 
         [0130]    As shown in  FIG. 11 , a plate  86  is buried in a position corresponding to the contactor area  76  so as to maintain planarity of the contactor area  76 . Accordingly, the contactor area  76  is protruded downward from the intermediate surface  51  as much as the sum of the thickness of the plate  86  and the amount of protrusion of the attachment surface  50  relative to the intermediate surface  51 . The plate  86  is made of an appropriate material such as a ceramic plate, a stainless steel plate, or the like. 
         [0131]    The sheet members  70   a  and  70   b  cooperatively sandwich the conductive paths  72  there between, and the sheet members  70   b  and  70   c  cooperatively envelop the plate  86  therein. 
         [0132]    The above sheet  70 , conductive paths  72 , and plate  86  may be manufactured with use of a photolithographic technique, an electroplating technique, a resin application technique, an electroforming technique, etc. by forming a plurality of conductive paths  72  on one surface of the sheet member  70   a , subsequently forming the sheet member  70   b  on a conductive paths  72  side of the sheet member  70   a , arranging the plate  86  on a position of the sheet member  70   b  corresponding to the contactor area  76 , and forming the sheet member  70   c  on a plate side of the sheet member  70   b.    
         [0133]    Each contactor  74  includes a pedestal portion  88  joined to a corresponding conductive path  72  and protruded in the downward direction of the sheet member  70   a  and a main body portion  90  integrally continuing into the lower end of the pedestal portion  88 . 
         [0134]    The pedestal portion  88  comprises a first seat portion  88   a  made of a metal material of the same kind (e.g., copper) as that of the junction portion of the corresponding conductive path  72  and a second seat portion  88   b  joined to the lower end of the first seat portion  88   a.    
         [0135]    The first seat portion  88   a  is joined to the corresponding conductive path  72  at its upper end surface. The second seat portion  88   b  is made of the same metal material (e.g., nickel) as the main body portion  90  integrally with the main body portion  90  and is joined to the first seat body portion  88   a.    
         [0136]    The main body portion  90  comprises an arm portion  90   a  extending horizontally from the lower end of the second seat portion  88   b  and a probe tip portion  90   b  protruded downward from the tip end of the arm portion  90   a.    
         [0137]    The above contactor  74  may be manufactured with use of a photolithographic technique, an electroplating technique, an electroforming technique, etc. by sequentially forming the first seat portion  88   a , the second seat portion  88   b , the arm portion  90   a , and the probe tip portion  90   b  in this order or reverse order. 
         [0138]    After a part of the sheet member  70   a  is removed, the contactor  74  manufactured as above is joined to the corresponding conductive path  72  at the upper end surface of the first seat portion  88   a  by conductive adhesive. Thus, each contactor  74  is supported on the sheet  70  in a cantilevered manner in a state where the main body portion  90  is distanced downward from the sheet  70 . 
         [0139]    However, the sheet  70 , the conductive paths  72 , and the contactors  74  may be manufactured consecutively with use of a photolithographic technique, an electroplating technique, a resin application technique, an electroforming technique, etc. By doing so as well, each contactor is supported on the sheet  70  in a cantilevered manner. 
         [0140]    In the above case, they may be manufactured in order of the probe tip portions  90   b , the arm portions  90   a , the second seat portions  88   b , the sheet member  70   a , the first seat portions  88   a , the conductive paths  72 , the sheet member  70   b , and the sheet member  70   c . The plate  86  is arranged on the sheet member  70   b  prior to formation of the sheet member  70   c.    
         [0141]    If the circuit board  22  is manufactured as above, the respective coupling strengths between the conductive path  72  and the first seat portion  88   a , between the first seat portion  88   a  and the second seat portion  88   b , between the second seat portion  88   b  and the arm portion  90   a , and between the arm portion  90   a  and the probe tip portion  90   b  are increased. 
         [0142]    Also, when the first seat portion  88   a  is the same metal material as the junction portion of the conductive path  72 , and the second seat portion  88   b  is the same metal material as the main body portion  90 , the coupling strengths between the first seat portion  88   a  and the conductive path  72  and between the second seat portion  88   b  and the main body portion  90  are further increased. 
         [0143]    The junction surface between the first and second seat portions  88   a  and  88   b  is within the sheet member  70   a  as shown in  FIG. 11 . Accordingly, since the junction surface between both the seat portions  88   a  and  88   b  is closed in the sheet member  70   a , even when a bending moment acts on the pedestal portion  88 , separation of the first and second seat portions  88   a  and  88   b  caused by the bending moment is prevented. 
         [0144]    As shown in  FIG. 11 , the circuit board  22  is bonded to the attachment surface  50  at least contactor area  76  by adhesive  92  stored in the recess  64  in a state where the contactor area  76  and the intermediate area  80  are opposed to the attachment surface  50 , and where part of each extending portion  82  is opposed to each slope  52 . 
         [0145]    The contactor area  76  and the intermediate area  80  around it are respectively thrust to the attachment surface  50  and the intermediate surface  51  around it at the time of being bonded to the block  20 . Thus, since excessive adhesive in the recess  64  is pushed out to an area around the contactor area  76  (at least part of the intermediate area  80 ), the circuit board  22  is bonded to an area around the attachment surface  50  (at least part of the intermediate surface  51 ) at the area around the contactor area  76  as well. As a result, the circuit board  22  is maintained in a state where the contactor area  76  is protruded further downward than a portion around it. 
         [0146]    When the contactor area  76  and the area around it are bonded to the attachment surface  50  and the area around it as above, the contactor area  76  and the area around it are supported on the block  20  in a stable manner, and thus the contactors  74  are stable against the support board  12 . 
         [0147]    The circuit board  22  is also attached at the tip ends of the extending portions  82  to the lower surface of the support board  12  by an elastic plate-shaped rubber ring  94  such as a silicone rubber, a plate-shaped thrusting ring  96  having certain hardness such as stainless steel, and a plurality of screw members  98  in a state where the connection bumps  84  are thrust to the connection lands  32  as shown in  FIG. 12 . 
         [0148]    Positioning of the circuit board  22  against the support board  12  is performed by a plurality of positioning pins  100  extending downward from the support board  12  and penetrating the extending portions  82  of the circuit board  22 , the rubber ring  94 , and the thrusting ring  96  to be protruded downward. Each positioning pin is held in the support board  12  in a stable manner. 
         [0149]    In a state where the circuit board  22  is attached to the block  20  and the support board  12  as above, each contactor  74  is aligned so that its probe tip  90   b  is opposed to a corresponding electrode of a device under test and is electrically connected to the tester land  30  of the support board  12  via the conductive path  72 , the connection bumps  84 , the connection lands  32 , the wires in the support board  12 , etc. 
         [0150]    Each reference mark member  24  is a pin member protruded downward from the slope  52  of the lower block portion  54  and is supported in the lower block portion  54  at its upper portion in a stable manner. In the example shown in the figures, three pairs of reference mark members  24  are provided. The reference mark members  24  of each pair are opposed to each other with the contactor area  76  and the intermediate area  80  in between. 
         [0151]    The lower end surface of each reference mark member  24  is a surface parallel to the attachment surface  50 , and the height position of the lower end surface of each reference mark member  24  is set back further upward than the height position of the contactors  74 . 
         [0152]    The lower portion of each reference mark member  24  is protruded in the downward direction of the circuit board  22  at the extending portion  82  of the circuit board  22 , passing between the adjacent conductive paths  72 . Since the pitch of the adjacent conductive paths  72  at the extending portion  82  is wider than that at the intermediate area  80 , the reference mark member  24  does not influence the formation position of the conductive paths  72 . 
         [0153]    As shown in  FIG. 9 , each reference mark member  24  has a reference mark  102  on the lower end surface. Each reference mark  102  cooperates with a reference mark  102  of an opposed reference mark member  24  with the contactor area  76  in between to represent the positions of the tip ends of the probe tip portions  90   b  or the probe tips located between both the reference marks  102  in the electrical connecting apparatus  10 . 
         [0154]    Each reference mark  102  has different optical characteristics from those of the periphery. Although the reference mark  102  is a round mark at the center in the example shown in the figures, it may be a dot, a crosshair intersection, etc. 
         [0155]    Each reference mark  102  may be formed by forming a mark layer on the lower surface of the reference mark member  24  in advance by an appropriate technique such as electroplating or paint application, after completion of the electrical connecting apparatus  10 , measuring the positions of the probe tip portions  90   a , and removing by laser beam corresponding positions in the mark layer based on the measurement result. By doing so, the reference mark  102  may be formed accurately without depending on the assembling accuracy of the electrical connecting apparatus  10 . 
         [0156]    The block  20 , the reference mark members  24 , the spring holder  42 , the attachment plate  60 , and the positioning pins  100  are made of appropriate materials, for example electrical insulating metal materials. 
         [0157]    As shown in  FIG. 13 , the distance dimension L 1  from the upper end of the annular portion formed by the arc portions  46   a  of the spring holder  42  to the upper end of the inward flange portion formed by the extending portions  46   b  is shorter than the distance dimension L 2  from the upper end of the upper block portion  56  to the lower end of the outward flange portion  59 . Also, in a state where the block  20  is attached to the plate spring  18 , the flange portion  59  is located on the upper side of the inward flange portion. 
         [0158]    As a result of the above, the plate spring  18  receives initial load to bring a state where at least the center area  38  is biased toward the upper side of the support board  12  and is elastically deformed by the preload. 
         [0159]    In a state where the electrical connecting apparatus  10  is assembled as above, planarity of the contactor area  76  against the support board  12  is adjusted. 
         [0160]    This planarity adjustment may be performed by adjusting the screwing amount of the adjustment screws  26  in the plate-shaped member  14  in a state that the contactor area  76  is parallel to the support board such that the screwing amount of the attachment screws  36  in the ring-shaped member  16  is small and thereafter screwing the attachment screws  36  in the ring-shaped member  16  to reach a state where the adjustment screws  26  abut to the upper surface of the ring-shaped member  16 . Accordingly, planarity of the contactor area  76  against the support board  12  may be adjusted easily. 
         [0161]    Since the contactor area  76  is bonded to the attachment surface  50 , it is reliably displaced against the support board  12  in conformity with the block  20  at the time of the aforementioned planarity adjustment. 
         [0162]    The electrical connecting apparatus  10  is incorporated in the testing apparatus in a state where the contactor area  76  is above the arrangement area of the device under test, and where the probe tip portion  90   b  of each contactor  74  is opposed to an electrode of the device under test, and the tester lands  30  of the support board  12  are connected to electrical circuits for an electrical test. In this manner, each contactor  74  is electrically connected to the electrical circuits for the electrical test. 
         [0163]    In the electrical connecting apparatus  10 , the reference marks  102  are measured for positioning of the probe tips of the contactors  74  against the testing apparatus in a state where the electrical connecting apparatus  10  is mounted in the testing apparatus. 
         [0164]    At the time of this measurement, since the reference marks  102  are formed on the lower end surfaces of the reference mark members  24  other than the contactors  74 , the probe tip positions may be measured highly accurately and reliably regardless of whether or not foreign matters remain on the probe tip portions  90   b  and without being influenced by optical characteristics in the vicinity of the reference marks  102 . 
         [0165]    As for the reference marks  102 , the reference marks  102  of at least one pair of reference mark members  24  whose lower end surfaces are distanced with the contactor area  76  in between only need to be measured. Accordingly, the two-dimensional positions of the contactors  74  on the coordinates in the testing apparatus may be measured accurately. 
         [0166]    However, if the reference marks  102  of the three pairs of reference mark members  24  whose lower end surfaces are distanced with the contactor area  76  in between are measured, the two-dimensional positions of the contactors  74  on the coordinates in the testing apparatus may be measured more accurately. 
         [0167]    At the time of the electrical test, the electrical connecting apparatus  10  and the device under test are moved relatively in directions in which they approach to each other. By doing so, the probe tip  90   b  of each contactor  74  is thrust to a corresponding electrode of the device under test, and overdriving acts on the contactor  74 . 
         [0168]    When the probe tip  90   b  of each contactor  74  is thrust to the electrode of the device under test, the cantilevered contactor  74  is elastically deformed slightly in an arc shape at the arm portion  90   a , and the plate spring  18  is elastically deformed due to the overdriving. 
         [0169]    At this time, since the plate spring  18  receives initial load to bring a state where at least the center area  38  is biased toward the upper surface side of the support board  12  and is elastically deformed by the preload, the probe pressure acting on the probe tip of each contactor  74  and the electrode of the device under test comes under the influence of not only reactive force by elastic deformation of the contactor  74  and the plate spring  18  when the probe tip is thrust to the electrode of the device under test but also reactive force based on elastic deformation of the plate spring  18  by the initial load. Accordingly, a good electrical contacting state may be obtained without increasing the overdriving amount. 
         [0170]    Also, since the center area  38  of the plate spring  18  is integrally connected to the circumferential area  40  by the extending areas  39 , the plate spring  18  is elastically deformed at the extending areas  39  reliably when the probe tips of the contactors  74  are thrust to the electrodes of the device under test. Consequently, irregular flexure of the plate spring  18  is prevented reliably. 
         [0171]    Further, since the outward flange portion  59  of the block  20  is located on the upper side of the inward flange portion  46   b  of the spring holder  42 , the plate spring  18  is kept in a state of receiving the initial load without preventing displacement of the block  20  in the up-down direction when the probe tips of the contactors  74  are thrust to the electrodes of the device under test. 
         [0172]    When the overdriving acts on the contactor  74 , the electrical connecting apparatus  10  takes the following technical merits. 
         [0173]    Since the contactor area  76 , the intermediate area  80 , and part of each extending portion  82  of the circuit board  22  are opposed to the attachment surface  50 , the intermediate surface  51 , and part of each slope  52  of the block  20 , respectively, and moreover the height position of the lower end surface of each reference mark member  24  is higher than the height position of the contactors  74 , the reference mark member  24  does not contact the device under test when the probe tips  90   b  are thrust to the electrodes of the device under test. 
         [0174]    When the contactors  74  are thrust to the electrodes, the plate spring  18  acts as a reaction force body for the center area of the circuit board  22 , which is the arrangement area of the contactors  74 . Consequently, the plate spring  18  is elastically deformed slightly by the circuit board  22  and the block  20  and allows the contactor area  76  to be displaced upward in parallel by the overdriving. This leads to a uniform thrusting force of the contactors  74  to the electrodes. 
         [0175]    The block  20  reliably transmits the deformation of the contactor area  76  of the circuit board  22  to the plate spring  18 , and the through hole  28  allows the plate spring  18  to be elastically deformed easily to the ring-shaped member  16  side. This stabilizes the elastic deformation of the plate spring  18  and the circuit board  22  and leads to easier contact of each contactor  74  with, the electrode. 
         [0176]    Irregular flexibility of the plate spring  18  when the overdriving acts on the contactors  74  is reliably prevented by the fact that the block  20  is attached to the star-shaped or cross-shaped intersection of the plate spring  18  and the fact that the inner surfaces of the ring-shaped member  16  and the spring holder  42  have the flat areas  48  and  48  extending in the tangential direction of the outer circumference surface of the plate spring  18  and in the up-down direction at the respective portions corresponding to the boundaries between the center area  38  and the circumferential area  40  of the plate spring  18 , and the thrusting force of the contactors  74  to the electrodes is more uniform. 
         [0177]    Since the coupling portion between both the seat portions  88   a  and  88   b  is located within the sheet  70 , that is, the coupling portion is located within the thickness dimension of the sheet  70 , a part of the bending moment acting on the pedestal portion  88  is received in the sheet  70 , and the coupling portion is protected by the sheet  70 . As a result, separation of the contactor  74  from the sheet  70  caused by the overdriving is prevented while the coupling force between the conductive path  72  and the pedestal portion  88  is large. 
         [0178]    The pedestal portion  88  distances the main body portion  90 , particularly the tip end of the contactor  74 , from the sheet  70  significantly. Accordingly, the main body portion  90  is hard to come into contact with the sheet  70 , and the sheet  70  is hard to contact the device under test by the overdriving, as a result of which the contactor  74  reliably contacts the electrode of the device under test. 
         [0179]    When the plate spring  18  made of a material having a smaller thermal expansion coefficient than that of stainless steel is used, thermal expansion and contraction of the plate spring  18  and displacement of the probe tip positions in reaction to heating or cooling of the device under test are small. Consequently, breakage of the probe tips and contact failure of the probe tips to the electrodes of the device under test are prevented. 
         [0180]    The spring constant of the plate spring  18  may be smaller than the total sum of the spring constant of all the contactors  74 . By doing so, as variation of the probe pressure per contactor is shown in  FIG. 14 , when the overdriving acts on the contactors  74 , only the contactors  74  are elastically deformed until the overdriving amount is one (approximately 10 micrometers) in which the initial load by the preload acted on the plate spring  18  and the total sum of the spring constant of all the contactors  74  are at equilibrium, and thereafter the plate spring  18  is elastically deformed mainly although the contactors  74  are also elastically deformed. 
         [0181]    As a result of the above, the probe pressure acting between the probe tips of the contactors  74  and the electrodes of the device under test increases significantly in reaction to the overdriving in a state where only the contactors  74  are elastically deformed (in a state of the initial load) and thereafter increases moderately. Thus, variation of the probe pressure by the overdriving is small, and stable electrical contact may be obtained. 
         [0182]    In the variation of the probe pressure shown in  FIG. 14 , the plate spring  18  is a molybdenum plate having a thickness of 0.1 mm and having spring constant of about 3.8 N/mm,  1550  contactors  74  have been used, the total sum of the spring constant of the contactors  74  is about 380 N/mm, and initial load (preload) of 3.8 N/mm has been applied to the plate spring  18 , in which state overdriving OD has acted on each contactor  74 . 
         [0183]    In a case where the mechanical strength of the support board  12  is high, the plate-shaped member  14  may not be provided. Also, the plate spring  18  may be attached to the support board  12  so as to be opposed to the through hole  28 . Further, instead of providing the plate spring  18  in the through hole  28 , the ring-shaped member  16  may be attached to the lower surface of the support board  12 , and the plate-shaped member  14  and the through hole  28  may be omitted. 
         [0184]    The present disclosure is not limited to the above embodiments but may be altered in various ways without departing from the spirit and scope of the present invention.