Abstract:
An electrical connecting apparatus comprising: a circuit board on which a reinforcing plate is mounted and a plurality of first electric connections are provided; a probe board on which second electric connections corresponding to the first electric connections are provided, with a plurality of probes electrically connected to the corresponding second electric connections; an elastic connector having plural pairs of both contacts capable of contacting the first and second electric connections corresponding to each other of both boards therebetween and receiving a biasing force in directions for both contacts to separate from each other; screw members for integrally combining them; and a spacer member for holding the probe tips substantially on the same plane by tightening of the screw members. Between the reinforcing plate and the probe board, a spacer plate is inserted for adjusting a distance from the other surface of the probe board to the probe tips.

Description:
TECHNICAL FIELD 
   The present invention relates to an electrical connecting apparatus such as a probe card for use in electrical connection of, for example, an integrated circuit which is a device under test and a tester which conducts electrical inspection for electrical test of an electric circuit. 
   BACKGROUND 
   A conventional electrical connecting apparatus of this type comprises: a circuit board having, for example, a printed circuit board (PCB); and a probe board disposed at a distance from the underside of the circuit board and provided with a plurality of probes on the underside opposing the surface which faces the circuit board (see, e.g., Patent Document 1). Between the circuit board and the probe board, there is placed an interposer including an elastic connector such as a pogo pin assembly, and through the interposer, each probe of the probe board is electrically connected to a socket provided on the circuit board. The electrical connecting apparatus is connected to a tester body by the socket. On the upside of the above-mentioned circuit board is provided a reinforcing plate for restraining warping of the circuit board. These reinforcing plate, circuit board, interposer and probe board are combined integrally by tightening screw members such as bolts to be inserted from the reinforcing plate side. 
   More specifically, the front end of a bolt inserted from the upside of the reinforcing plate is screwed into an anchor portion provided on the probe board and tightened. A cylindrical spacer member is mounted on each bolt. The spacer member has its one end brought into contact with the underside of the reinforcing plate and its lower end brought into contact with the top of the anchor portion. When the bolt is tightened, the spacer member keeps the distance from the underside of the reinforcing plate to the tip of each probe approximately constant in cooperation with the anchor portion into which the front end of the bolt is screwed. Thus, unless any deformation in the thickness direction such as warping or wave-like deformation is introduced to the probe board where the probes are provided, the probe tips can be held on an imaginary plane. 
   However, a deformation in the thickness direction is generally introduced to the probe board, and it is hard to correct this deformation sufficiently by the spacer member. This sometimes causes difference in height of the positions of the probe tips with the deformation of the probe board. 
   Thus, the applicant of this application proposed to form each probe on the probe board in International Application No. PCT/JP2005/009812 and International Application No. PCT/JP2005/019850 to place each probe so that the tip of the probe may be positioned on an imaginary plane with the deformation of the probe board held as it is. In the PCT/JP2005/009812, it was proposed to change the height of the respective anchor portions according to the deformation of the probe board so that the top surfaces of the respective anchor portions are located on the same plane in order to maintain the deformation of the probe board, thereby aligning the tips of the probes on the same plane. Also, in the foregoing PCT/JP2005/019850, in order to maintain the deformation of the probe board, the spacer members having different lengths according to the deformation of the probe board are applied, thereby aligning the probe tips on an imaginary plane. 
   Thus, by selecting the height dimension of the anchor portion according to the deformation of the probe board, or by selecting the length dimension of the spacer member whose one end contacts the anchor portion, it is possible to locate the respective tips substantially on the same plane in spite of the deformation of the probe board. Thereby, in spite of the above-mentioned deformation of the probe board, in an electrical test of the tester with a plurality of IC circuits incorporated on a semiconductor wafer, it is possible to make the tips of the respective probes contact the corresponding electrodes with substantially uniform pressing force. 
   Patent Document 1: International Publication No. 2005/106504 
   BRIEF SUMMARY 
   These electrical connecting apparatus are, however, used with the underside edge portion of the circuit board mounted on an edge of an annular card holder of a tester head. Therefore, the underside of the circuit board to be mounted on the card holder becomes a surface to be disposed on the holder, so that in a state where the electrical connecting apparatus are mounted on the card holder, dispersion is caused in the height positions of the imaginary plane of the probe tips, namely, the height positions of the general probe tips because of dispersion in thickness due to error in production of the circuit board. Since this dispersion causes dispersion in general needle pressure of the probes of each electrical connecting apparatus, it has been desired to restrain dispersion in probe pressure of each electrical connecting apparatus for conducting a stable electrical test. 
   An object of the present invention is, therefore, to provide an electrical connecting apparatus capable of keeping the general height position of the probe tips from a surface to dispose the circuit board to the probe card holder at a predetermined height position in spite of the dispersion in thickness dimension of the circuit board. 
   The present invention is characterized basically by inserting a spacer plate for compensating dispersion in thickness dimension of a circuit board between a reinforcing plate and a circuit board. 
   In other words, the electrical connecting apparatus according to the present invention is characterized by comprising: a circuit board on one surface of which a reinforcing plate is mounted and on the other surface of which a plurality of first electric connections are provided; a probe board, on one surface of which disposed at a distance from the other surface of the circuit board and opposing the circuit board, second electric connections corresponding to the first electric connections are provided and on the other surface of which a plurality of probes respectively electrically connected to the corresponding second electric connections are provided; an elastic connector disposed between the circuit board and the probe board and having plural pairs of both contact points capable of contacting the first and second electric connections corresponding to each other of both boards correspond wherein both contact points of each pair receive biasing force toward separating directions from each other; screw members for integrally combining the reinforcing plate, circuit board, elastic connector and probe board; and a spacer member for holding the probe tips substantially on an imaginary plane by tightening the screw members; and between the reinforcing plate and the circuit board, a spacer plate for adjusting the distance from the other surface of the circuit board to the imaginary plane where the probe tips are located is inserted. 
   It is conceivable that such a spacer plate is disposed between the circuit board and the card holder which receives the edge portion of the circuit board and between the circuit board and an interposer or between the interposer and the probe board, etc. When the spacer plate is disposed between the circuit board and the card holder, however, it is necessary to replace the spacer plate with an adequate one in each electrical connecting apparatus every time the electrical connecting apparatus is replaced, which complicates an attachment work of the electrical connecting apparatus to the card holder. 
   Also, when the spacer plate is disposed between the circuit board and the interposer or between the interposer and the probe board, the distance between the circuit board where the interposer is to be disposed and the probe board, namely, the distance between the opposing electric connections of each board changes. Therefore, if an elastic connector such as a pogo pin assembly is used as the interposer, contact pressure of the elastic connector to be pressed against mutually opposing electric connections of both boards will change. 
   More particularly, the pogo pin assembly, for example, includes pogo pins each having a pair of pogo pin contacts and a spring member between the pogo pin contacts. Each pogo pin is accommodated in a pogo pin block, and both ends of each pogo pin, namely, the front ends of a pair of pogo pin contacts are accommodated so as to be able to project from the pogo pin block at a predetermined stroke. Each pair of pogo pin contacts are pressed against the electric connections opposite to each other of the circuit board and the probe board by the biasing force of the spring member. The distance between both boards increases when the spacer plate is inserted between the circuit board and the pogo pin block of the pogo pin assembly or between the pogo pin block and the probe board. Also, when this distance increases, the contact pressure of each pogo pin contact against each electric connection of both boards lowers. Thus, when the distance between both boards surpasses a predetermined value due to insertion of the spacer board, it is feared that a stable electrical connection by the elastic connector between the circuit board and the probe board might be damaged. 
   On the other hand, it is not necessary in the present invention to replace the spacer plates every time the electrical connecting apparatus is replaced, because the spacer plate selected according to error in production of the circuit board to compensate dispersion in thickness dimension of the circuit board is inserted between the reinforcing plate and the circuit board, and the spacer plate is combined integrally with the reinforcing plate, circuit board, elastic connector and probe board by screw members such as bolts. 
   Also, since there is no relation in electrical connection between the reinforcing plate where the spacer plate is disposed and the circuit board, there is no influence. Further, the spacer plate does not cause any change in the distance between the circuit board and the probe board, so that no damage is caused to the stable electrical connecting feature by the elastic connector due to the insertion of the spacer plate. 
   Thus, according to the present invention, the distance from the other surface of the circuit board to each probe tip from the other surface can be adequately set in spite of dispersion in thickness dimension of each circuit board due to error in production of the circuit board, without damaging the feature of the stable electrical connection of the elastic connector. Accordingly, it becomes possible to prevent change in general needle pressure of the probes due to dispersion in thickness dimension of the circuit board to ensure an electrical inspection. 
   The spacer member can be disposed so as to penetrate at least the reinforcing plate and the circuit board in the thickness direction with its end portion in contact with the one surface of the probe board and to provide an anchor portion into which the front end portion of the screw member is screwed. 
   The tip of each probe to be provided on the probe board can be formed to be located on an imaginary plane in a state that deformation in the thickness direction of the probe board is introduced. In such a case, by adequately selecting the length dimension of the spacer member and height dimension of the anchor portion, the probe board can be assembled without correcting warping or wave-like deformation of the probe board and with such deformation kept as it is, whereby the height positions of the probes can be aligned on the imaginary plane. 
   It is possible to use the circuit board with the edge portion of the other surface of the circuit board mounted on the upside of the edge portion of an annular card holder of the test head, and to select the spacer plate so as to adjust the distance from the upside of the card holder to the imaginary plane where the probe tip is located. 
   The spacer plate can be made by overlapping a plurality of spacer plates of the same thickness dimension, and the number of the spacer plates to be used can be selected according to the thickness dimension of the circuit board. 
   Each spacer plate can be made of a metal plate or an insulating plate. 
   As the elastic connector can be used a well-known pogo pin connector which is provided with a pair of contacts disposed in pairs so as to make the respective axes coincide, the pogo pins receiving an elastic biasing force in a direction to be separated from each other and electrically connected to each other, and a pogo pin block which holds the pogo pins. 
   Also, if necessary, a well-known wire connector which is provided with a plurality of elastic wires disposed between respectively corresponding electric connections of the circuit board and the probe board can be used as the elastic connector. In this wire connector, both ends of each elastic wire are adapted to be both contact points thereof. 
   The present invention can provide an electrical connecting apparatus capable of keeping the whole height positions of probe tips at a predetermined height position in a state of being attached to the probe card holder, despite dispersion in the thickness dimension of a circuit board. Therefore, despite the dispersion in the thickness dimension due to the error in production of a circuit board, the probe tips can contact the corresponding electrodes by a predetermined pressing force, thereby increasing reliability of an electrical inspection. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a plan view of the electrical connecting apparatus according to the present invention. 
       FIG. 2  is a section obtained along the line II-II shown in  FIG. 1 . 
       FIG. 3  is a partly enlarged section of the elastic connector shown in  FIG. 2 . 
   

   DETAILED DESCRIPTION 
   The electrical connecting apparatus  10  according to the present invention is shown in  FIGS. 1 and 2 . As shown in  FIG. 2 , the electrical connecting apparatus  10  is used, for instance, for an electrical inspection of a semiconductor wafer  14  on a well-known vacuum chuck  12  which constitutes a sample table of a tester. In the semiconductor wafer  14 , a plurality of IC circuits (not shown) are incorporated, and for an electrical inspection of those IC circuits, the electrical connecting apparatus is used to connect each connection pad to an electric circuit of a tester body (not shown). 
   The electrical connecting apparatus  10  comprises, as shown in  FIG. 2 : a circular flat plate-like circuit board  18  having an underside  18   a  as an attaching surface to an annular card holder  16  to be provided at a tester head of the tester; a circular flat plate-like reinforcing plate  20  to be mounted on the upside  18   b  of the circuit board; a probe board  22  to be disposed at a distance from the underside  18   a  of the circuit board  18 ; and an elastic connector  24  disposed between the underside  18   a  of the circuit board  18  and the upside  22   a  of the probe board opposing the underside. 
   The circuit board  18  includes a printed circuit board (PCB) such as the conventional one, and as shown in  FIG. 1 , at an edge portion exposed from the reinforcing plate  20  of its upside  18   b , a plurality of sockets  26  for electric connections to the tester are annularly arranged. In  FIG. 2 , the sockets  26  are omitted to simplify the view. 
   On the underside  18   a  of the circuit board  18  is formed a first electric connection  28  corresponding to each contact point of each socket  26 . Each electric connection  28  is connected to one of the contact points, to which each socket  26  corresponds, through a well-known electrically conducting path (not shown). 
   In the example shown in  FIG. 2 , a probe board  22  has a ceramic plate  30  disposed to oppose to the circuit board  18  and a flexible wiring plate  32  joined to the ceramic plate. The upside  30   a  of the ceramic plate  30  is disposed to oppose the underside  18   a  of the circuit board  18 , thereby forming the upside of the probe board  22  which opposes to the circuit board  18 . On this upside  30   a  is formed a second electric connection  34  corresponding to the electric connection  28  of the circuit board  18 . 
   The upside  32   a  of a wiring plate  32  is joined to the underside  30   b  of the ceramic plate  30 , so that the underside  32   b  constitutes the underside of the probe board  22 . On the underside of the probe board  22 , namely, the underside  32   b  of the wiring plate  32 , are provided a plurality of probes  36  corresponding to the connection pads of the semiconductor wafer  14 . 
   On the ceramic plate  30  and wiring plate  32  constituting the probe board  22 , is formed an electrically conducting path (not shown) such as the conventional one, and each probe  36  is connected to the corresponding second electric connection  34  through the electrically conducting path. 
   Since thermal or mechanical distortion stress is applied to the probe board  22  during a formation process of the electrically conducting path and other processes, warping in the thickness direction or wave-like deformation in the thickness direction is generally introduced to the probe board  22 . A part of this deformation remains in a state that no load acts on the probe board  22 . The tips  36   a  of the respective probes  36  are formed, as shown in  FIG. 2 , to align on an imaginary plane P, with the remaining non-load deformation of the probe board  22  kept as it is. 
   The elastic connector  24  disposed between the circuit board  18  and the probe board  22  is, in the example shown in  FIG. 2 , a well-known pogo pin assembly. This pogo pin assembly  24  is provided with a pogo pin block  24   a  to be inserted between the circuit board  18  and the probe board  22 , and a plurality of pogo pins  24   b  to be assembled into the pogo pin block. 
     FIG. 3  shows region A which is enclosed with an oval in  FIG. 2  partially enlarged. As shown clearly in  FIG. 3 , in the pogo pin block  24   a  of the pogo pin assembly  24 , holes  38  penetrating in the thickness direction at the positions corresponding to the electric connections  28  and  34  of the circuit board  18  and the probe board  22 . In the respective holes  38 , the pogo pins  24   b  are held, making their axis directions coincident. Each pogo pin  24   b  is provided, as is well known, with a cylindrical member  42  to be received into the hole  38 , a pair of rod-like contacts  44  to be aligned in the axial direction spaced apart from each other in the axial direction of the cylindrical member within the cylindrical member, with their longitudinal directions aligned; and a cylindrical compression coil spring  46  to be disposed within the cylindrical member  42 . 
   At the opposing inner ends of the pair of contacts  44 , engaging portions  44   a  for preventing falling of each contact  44  from the cylindrical member  42  are provided and disposed between the engaging portions  44   a  with the end portions brought into contact with the respective engaging portions  44   a . The coil spring  46  electrically connects the contacts  44  and gives the biasing force to the contacts  44  in a direction for its outer ends to be apart from each other so that the outer ends of both contacts  44  may project from the end portion of the cylindrical member  42 . Each outer end of both contacts  44  becomes a contact of the pogo pin  24   b . The pogo pin  24   b  of each pogo pin assembly  24  presses both contacts which are the outer ends of the contact  44  against the corresponding electric connections  28  and  34  by the biasing force of the coil spring  46 . The pogo pin assembly  24  of this type is set such that each contact  44  contacts the corresponding electric connection  28 ,  34  by the adequate biasing force so far as, for example, the amount of displacement by the extension and contraction between both outer ends of both contacts  44  is within about 300 μm. 
   The elastic connector  24  formed by this pogo pin assembly  24  is, as mentioned above, disposed between the ceramic plate  30  defining the upside  30   a  of the probe board  22  and the under side  18   a  of the circuit board  18  opposing thereto, thereby electrically connecting the opposite second electric connection  34  of the probe board  22 . By this electrical connecting action of the elastic connector  24 , each probe  36  is connected to the corresponding each contact of the socket  26 , and to the tester body. 
   Also, as shown in  FIG. 2 , a spacer plate  48  made of a plate member having a uniform thickness dimension is inserted between the upside  18   b  of the circuit board  18  and the reinforcing plate  20 . As mentioned later, this spacer plate  48  can be used alone or with plural plate members of equal thickness layered according to the difference in thickness of the circuit board  18  due to error in production of the circuit board  18 . For such a spacer plate  48 , it is possible to use an electrically conducting plate member like a stainless plate having a thickness, for example, of 100 μm, or like a polyimide film. Also, a layer with plural spacer plates  48  of different thicknesses combined can be used. 
   The reinforcing plate  20 , spacer plate  48 , circuit board  18 , elastic connector  24  and probe board  22  are integrally combined by screw members  50  such as bolts. For this combination, the screw members  50  are inserted from the upside  20   a  of the reinforcing plate  20  into the reinforcing plate  20 , spacer plate  48 , circuit board  18  and elastic connector  24 . Also, an anchor portion  52  having a female screw hole  52   a  into which the end for insertion of the screw member  50  is screwed is formed on a surface opposing the circuit board  18  of the probe board  22 , namely, the upside  30   a  of the ceramic plate  30 . The female screw hole  52   a  opens on the top surface of each anchor portion  52 . A generally cylindrical spacer member  54  is mounted on the screw member  50  whose front end portion is screwed into the female screw hole  52   a.    
   A flange portion  54   a  is formed at the upper end portion of each spacer member  54  to stretch radially outward. In the reinforcing plate  20  are formed holes  56  to allow a part excluding the flange  54   a  of the spacer member  54  to be inserted in the plate thickness direction. At the upper end of the hole  56  is formed an increased diameter portion  56   a  for receiving the flange portion  54   a , so that the flange portion  54   a  is received in the increased diameter portion  56   a  such that an end surface of the hole  56  which is the upper end of the spacer member  54  coincides with the upper surface  20   a  of the reinforcing plate  20 . The lower end of each spacer member  54  is disposed to abut the upper surface of the corresponding anchor portion  52 . 
   In case where the tips  36   a  of the probes  36  are aligned on the same imaginary plane P in a state that warping or wave-like deformation is introduced to the probe board, the sum of the length dimension L 1  of each spacer member  54  and the height L 2  of the corresponding anchor portion  52  is set for each spacer member  54 , basically to retain the warping or wavelike deformation of the probe board  22  with the underside  20   b  of the reinforcing plate  20  as a reference plane. 
   As regards this spacer member  54  and anchor portion  52 , it is desirable to make the top surfaces of the anchor portions  52  align on the same plane in spite of the deformation of the base plate  22 . In other words, by increasing or decreasing the length dimension  12  of the anchor portion  52  according to the deformation of the probe board  22 , the top surfaces of the anchor portions  52  can be aligned on the same plane in spite of the deformation of the probe board  22 , it is possible to combine the probe board  22  with the circuit board  18 , reinforcing plate  20  and the like by using the spacer members  54  having the same length dimension L 1  with the deformation of the probe board  22  kept. 
   In any case, by adequately selecting the sum of the length dimension L 1  of the spacer member  54  and the height L 2  of the anchor portion  52 , the probe board can be assembled with the deformation of the probe board  22  kept as it is, thereby aligning the tips  36   a  of the probes  36  on an imaginary plane P parallel to the underside  20   b  of the reinforcing plate  20 . The electrical connecting apparatus  10  is, however, attached to the card holder  16  such that the underside  18   a  of the circuit board  18  is mounted on the upside  16   a  of the annular edge portion of the card holder  16 , so that dispersion is caused according to production error in the thickness dimension L 4  of the reinforcing plate  20  to the distance L 3  from the upside  16   a  which is to be an attachment plane of the card holder  16  to the imaginary plane P where the tips  36   a  of the probes  36  are positioned, as shown in  FIG. 2 . 
   Since the distance between the mounting surface of the card holder  16 , i.e., the upside  16 , and the chuck surface of the vacuum chuck  12  is kept constant at the time of inspection of the semiconductor wafer  14 , dispersion in the distance L 3  causes difference in needle pressure when the tips  36   a  of the probes  36  are pressed against the corresponding electrodes. 
   For instance, the circuit board  18 , when formed with an allowable error of 6.2 mm±0.3 mm in thickness dimension, causes dispersion between 5.9 mm and 6.5 mm. Without using the spacer plate  48 , therefore, there are caused differences to the pressing force of the tips  36   a  of the probes  36 , i.e., the needle pressures of the probes  36  of the electrical connecting apparatus  10 , in correspondence to differences of 0.6 mm at a maximum. 
   In the electrical connecting apparatus  10  according to the present invention, in spite of dispersion due to production error in the plate thickness dimension L 4  of the reinforcing plate  20 , the number of the spacer plates  48  selected to correspond to the plate thickness of the reinforcing plate  20  is selected so that the distance L 3  from the mounting surface  16   a  of the card holder  16  to imaginary plate P where the tips of the probes  36  may be aligned can be kept at a proper value. 
   Therefore, in the electrical connecting apparatus  10  according to the present invention, where each spacer plate  48  has a thickness dimension, for example, of 100 μm, six spacer plates  48  at a maximum are laminated between the reinforcing plate  20  and the circuit board  18 , and by selecting the number of proper spacer plates  48  to be inserted, thereby enabling to conduct an electrical inspection of the semiconductor wafer  14  with substantial difference in needle pressure kept almost at zero. 
   By the insertion of the spacer plates  48 , the distance between the reinforcing plate  20  and the circuit board  18  is increased by the total thickness dimension corresponding to the number of the spacer plates  48 . According to the increase in distance, however, spacer members  54  for example can be replaced with those having the proper length dimension L 1 . 
   In the electrical connecting apparatus  10  according to the present invention, the spacer plates  48  selected to compensate the dispersion in the thickness dimension of the circuit board  18  are inserted between the reinforcing plate  20  and the circuit board  28 . Since the spacer plate  48  is united with the reinforcing plate  20 , circuit board  18 , elastic connector  24  and probe board  22  by the screw member  50 , there is no need to replace the spacer plate  48  every time the electrical connecting apparatus  10  is replaced. 
   Since there is no relation in electrical connection between the reinforcing plate  20  and the circuit board  18  where the spacer plate  48  is disposed, no influence is given thereto. Further, there is caused no change in the distance between the circuit board  18  and the probe board  22  by the spacer plate  48 . Consequently, there is no change in contact pressure of the pogo pin  24   b  of the elastic connector  24  by the insertion of the spacer plate  48 , and no contact failure due to shortage in the contact pressure. Thus, the insertion of the spacer plate  48  does not cause damage to the feature of the stable electrical connection by the pogo pin assembly  24 . 
   As a result, according to the present invention, there is no damage to the feature of the stable electrical connection of the elastic connector  24 , and in spite of dispersion in thickness dimension of the circuit boards  18  due to production error of the circuit boards  18 , the distance L 3  from the underside  18   a  of the circuit board to the tips  36   a  of the probes  36  can be properly set. Thus, any change in general contact pressure of the probes  36  due to the dispersion in thickness dimension of the circuit boards  18  can be prevented, and an electrical inspection of the device under test  14  such as a semiconductor wafer is ensured. 
   In the foregoing, an example is shown that, in spite of the deformation of the probe board  22 , the probes  36  are formed to align on the same imaginary plane P with the deformation introduced to the probe board  22  to make the tips  36   a  of the probes  36  align on the same imaginary plane P, and that the probe board is combined with the circuit board  18  and the reinforcing plate  20  and the like by the anchor portion  52  and the spacer member  54  so that the probe board  22  may maintain the deformation. 
   The present invention can be applied to an electrical connecting apparatus using, in place of this, a flat probe board without deformation and the probe tips  36   a  formed to align on the same imaginary plane with deformation introduced to the probe board. In this case, spacer members and anchor portions having the same length dimensions (L 1 , L 2 ) are adopted as spacer members  54  and anchor portions  52 . 
   Further, for the elastic connector  24  provided as an interposer, another elastic connector such as a well-known wire connector provided with an elastic wire can be used in place of the pogo pin assembly. 
   The present invention is not limited to the foregoing embodiments but can be varied without departing from its purport.