Patent Publication Number: US-2013233099-A1

Title: Probe assembly

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a probe card of a prober unit used in a process for manufacturing electronic devices including LSI for inspecting circuits of multiple semiconductor chips that are formed on a semiconductor wafer. More particularly, the present invention relates to a probe card used in a wafer-level probing test. In the probing test, probes are made to touch circuit terminals (“pads”) arranged on the semiconductor chips to perform collective measurement of electrical conductivity of the semiconductor chips. 
     2. Description of Prior Art 
     With the advance of semiconductor technology, integration of electronic devices is increasing and the number of electrode terminals (“pads”) formed on each semiconductor chip is also increasing. Then, finer pad arrangements are becoming predominant with, for example, reduced pad areas and finer pad pitches. 
     Today, the LSI having the finest pitches and the largest number of electrodes is the LSI used mainly for driving liquid crystal panels (hereinafter, “LCD-driving LSI”). Pad arrangements vary in the number of electrode terminals, i.e., the number of liquid crystal pixels to be driven: in  FIG. 9A , pads are arranged only on two opposite sides; in  FIG. 9B , pads are arranged along the periphery; and in  FIG. 9C , pads are arranged along the periphery and, on one side, two lines of pads are arranged alternately to support multi-pin arrangements. 
     Regarding especially the alternate pad arrangement illustrated in  FIG. 9C , LSIs having pitches as fine as 15 micrometers or less between adjoining electrode pads have been developed. There is a demand to reduce inspection cost by simultaneous measuring of two to eight of these fine-pitch LSIs. 
     An exemplary probe card which addresses such a demand is described in Japanese Unexamined Patent Application Publication No. 2010-91541. In the described probe card, as illustrated in  FIG. 10 , thin plate-shaped probes  80  are arranged at fine pitches; a tip of each probe  80  is placed in each of guide holes  83  formed on a guide plate  82  in accordance with position of pads of a to-be-inspected LSI; and the guide plate  82  is fixed at a predetermined position. In this structure, tip positions of all the probes are fixed precisely. 
     The probe card as described in Japanese Unexamined Patent Application Publication No. 2010-91541, however, has the following problem: in an even finer (e.g., 15 micrometers or less) pad pitch structure, it is necessary to machine the guide holes on the guide plate in a finer and more precise manner; and an assembly process in which all the probe tips are made to be placed in the guide holes is very complicated, whereby the assembly cost increases. Fine-pitch structures have the following problem: it is necessary to reduce the thickness of the probe to prevent interference between adjoining probes and, as a result, deformation of the probes at vertical probe portions thereof due to buckling or twisting occurs relatively easily. 
     The present invention has been devised to overcome these problems and provides the following probe card used for inspection of semiconductor chips having fine-pitch pad arrangements, such as LCD-driving LSIs: the probe card is capable of touching electrode pads including continuous fine-pitch pads in a precise and reliable manner; and thereby performing electrical property inspection of all the semiconductor chips and, at the same time, providing a probe card of lower cost. 
     SUMMARY OF THE INVENTION 
     In order to overcome the problems described above, the present invention is a probe assembly including: a vertical probe which is formed by etching metal foil, and touches a to-be-inspected semiconductor chip electrode; an output terminal which projects from a side opposite to the side of the vertical probe and touches a wiring board; and a thin plate-shaped probe which has a substantially rectangular cross section at a part thereof and includes an opening which engages a support rod, wherein the support rod includes a first guide groove which guides the opening, a second guide groove which guides the vertical probe, and a third guide groove which guides the output terminal. This structure has an effect that, since the probes constitute a probe assembly, even thin plate-shaped probes are not easily deformed due to buckling, twisting or other causes. 
     In an aspect of the present invention, a projection is provided on a side of the vertical probe which faces a guide groove thereof and a projection is provided on a side of the output terminal which faces a guide groove thereof; the projection of the vertical probe is placed in the guide groove thereof and the projection of the output terminal is placed in the guide groove thereof; and phase difference is provided between relative positions of the projections of adjoining vertical probes and between the relative positions of the projections of adjoining output terminals. It is therefore possible to form the guide grooves easily even in fine pitch arrangements. 
     In another aspect of the present invention, the Z direction length of the guide groove of the vertical probe equals to the sum total of at least a displacement amount of the vertical probe in the Z direction and the Z-direction length of the projection. It is therefore possible to easily form the guide grooves corresponding to adjoining projections. 
     With the structures described above, the probe card according to the present invention is, the following probe card used for inspection of semiconductor chips having fine-pitch pad arrangements, such as LCD-driving LSIs: the probe card is capable of touching electrode pads including continuous fine-pitch pads in a precise and reliable manner; and, at the same time, providing a probe card of lower cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a first embodiment of the present invention. 
         FIG. 2  illustrates an operation of the first embodiment of the present invention. 
         FIGS. 3A and 3B  illustrate an operation of the first embodiment of the present invention. 
         FIG. 4  illustrates a second embodiment of the present invention. 
         FIGS. 5A to 5D  illustrate the second embodiment of the present invention. 
         FIGS. 6A and 6B  illustrate the second embodiment of the present invention. 
         FIGS. 7A and 7B  illustrate an operation of the second embodiment of the present invention. 
         FIGS. 8A and 8B  illustrate the second embodiment of the present invention. 
         FIGS. 9A to 9C  illustrate several kinds of pad arrangements of existing LSIs. 
         FIG. 10  illustrates an example of a related art probe assembly. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     An embodiment of the present invention will be described in detail with reference to the drawings.  FIG. 1  is a perspective view of a first embodiment of the present invention, illustrating an entire structure of a fine-pitch probe assembly.  FIGS. 2 ,  3 A and  3 B illustrate an operation of the probe assembly. 
     Probe Structure 
     A probe assembly  1  and thin plate-shaped probes  10  which constitute the probe assembly  1  are illustrated in  FIGS. 1 ,  3 A and  3 B. Each probe  10  includes parallel spring sections  12  and  15  formed by etching metal foil  11 . The parallel spring section  12  carries out a probing function. The parallel spring section  15  is formed on the side opposite to that of the parallel spring section  12 . Each probe  10  includes an output terminal  16  for the output to a wiring board, and an opening  18  in which a support rod  20  which is a part of the probe assembly  1  is placed and fixed. 
     The parallel spring section  12 , which touches an electrode pad  100  and carries out a probing function, forms a parallelogram spring constituted by a vertical probe  13 , two parallel beams  12   a  and  12   b  and a fixing section  17 . When the electrode pad  100  starts touching a tip  14  of the vertical probe  13  and moves in the Z direction by predetermined distance (“overdrive”) Od 11  due to increased pressing force as illustrated in  FIG. 3A , the vertical probe  13  produces spring force in the vertical direction (i.e., Z direction) to establish electrical conduction between the vertical probe  13  and the electrode pad  100  as illustrated in  FIG. 3B . 
     Similarly, the output terminal  16  is a part of the parallel spring section  15  which is constituted by parallel beams  15   a  and  15   b . Electrical conduction between the output terminal  16  and a wiring board  110  is established in the following manner: as illustrated in  FIG. 3A , an amount of change Od 12  is applied to the output terminal  16  to produce spring force in the Z direction when the output terminal  16  is fixed to a pad  111  of the wiring board  110 ; and the output terminal  16  touches the pad  111  of the wiring board  110  with reaction force of the spring. The spring load to the pad  111  of the wiring board  110  of the output terminal  16  is applied all the time after the probe assembly  1  is fixed to the wiring board  110  in the state illustrated in  FIG. 3B . 
     Structure of Support Rod 
     The support rod  20  is constituted by a first holding unit  21 , a second holding unit  22  and a third holding unit  23 . The first holding unit  21  has a substantially rectangular cross section and holds the probe  10 . The second holding unit  22  extends in the Z direction from the first holding unit  21  along the vertical probe  13 . The third holding unit  23  extends in the Z direction from the first holding unit  21  toward a tip of the output terminal  16 . 
     Holding Probes 
     First guide grooves  24  are formed at predetermined positions on side surfaces  211  and  212  of the first holding unit  21 . Each first guide groove  24  guides sides  181  and  182  of the opening  18  of the probe  10  to determine the position of the probe  10 . As illustrated in the drawings, the sides  181  and  182  of the opening  18  may include saw-shaped projections  183   a  to  183   d  which may engage the side surfaces  211  and  212  of the first holding unit  21  to prevent the probes  10  from being disassembled easily. 
     Guiding Vertical Probe 
     Second guide grooves  25  are formed on a side surface  221  of the second holding unit  22  at the positions corresponding to those of the first guide grooves  24  in the Y direction. Each second guide groove  25  guides a side edge of the vertical probe  13  to determine the position of the vertical probe  13 . The X direction (described below) herein corresponds to the length direction of the probe. The Y direction is perpendicular to the X direction on the same plane. The Z direction is the vertical direction which is perpendicular to both the X and Y directions. 
     Guiding Output Terminal 
     Third guide grooves  26  are formed on a side surface  231  of the third holding unit  23  at the positions corresponding to those of the first guide grooves  24  in the Y direction. The output terminal  16  includes an extended portion  161  which extends in the Z direction. The extended portion  161  is guided by the third guide groove  26 , whereby the output terminal  16  is positioned. 
     In the structure described above, the probes  10  are supported by and fixed to the support rod  20  and the vertical probes  13  and the output terminals  16  are guided by the guide grooves provided in the support rod  20 . There is therefore an effect that the vertical probes  13  and the output terminals  16  of adjoining probes  10  are arranged at precise pitches and that even thin plate-shaped probes are not easily deformed due to buckling, twisting or other causes. 
     Second Embodiment 
     Next, a second embodiment of the present invention will be described in detail with reference to the drawings. 
     Probe Structure 
     A thin plate-shaped probe  30  is illustrated in  FIGS. 4 to 7B . Each probe  30  includes parallel spring sections  32  and  35  which are formed by etching metal foil  31 . The parallel spring section  32  carries a probing function. The parallel spring section  35  is formed on the side opposite to that of the parallel spring section  32 . Each probe  30  includes an output terminal  36  for the output to a wiring board, and an opening  38  in which a support rod  40  is placed and fixed. 
     The parallel spring section  32 , which touches an electrode pad  100  and carries out a probing function, forms a parallelogram spring constituted by a vertical probe  33 , two parallel beams  32   a  and  32   b  and a fixing section  37 . As illustrated in  FIG. 7A , when the electrode pad  100  starts touching a tip  34  of the vertical probe  33 , and pressing force is increased, spring force is produced in the vertical direction (i.e., Z direction) by the vertical probe  33  as illustrated in  FIG. 7B , whereby electrical conduction is established between the tip  34  of the vertical probe  33  and the electrode pad  100 . 
     Similarly, the output terminal  36  is a part of the parallel spring section  35  which is constituted by parallel beams  35   a  and  35   b . Electrical conduction between the output terminal  36  and a wiring board  110  is established in the following manner: as illustrated in  FIG. 7A , when the output terminal  36  is fixed to the wiring board  110 , spring force is produced in the vertical direction (i.e., Z direction); and the output terminal  36  touches a pad  111  of the wiring board  110  with reaction force of the spring. The spring load to the pad  111  of the wiring board  110  of the output terminal  36  is applied all the time after a probe assembly  1  is fixed to the wiring board  110  in the state illustrated in  FIG. 7B . 
     Projections of Probe 
     As illustrated in the drawings, saw-shaped projections  383   a  to  383   d  are formed on sides  381  and  382  of the opening  38 , and a projection  331  is formed at an edge of the vertical probe  33 . The output terminal  36  includes an extended portion  361  and a projection  362 . The extended portion  361  extends in the Z direction. The projection  362  is formed at an edge of the extended portion  361 . 
     Structure of Support Rod 
     The support rod  40  is constituted by a first holding unit  41 , a second holding unit  42  and a third holding unit  43 . The first holding unit  41  has a substantially rectangular cross section and holds the probe  30 . The second holding unit  42  extends in the Z direction from the first holding unit  41  along the vertical probe  33 . The third holding unit  43  extends in the Z direction from the first holding unit  41  toward a tip of the output terminal  36 . 
     Holding Structure of Opening 
     First guide grooves  44   a  to  44   d  ( 44   c  and  44   d  are not illustrated) are provided on side surfaces  411  and  412  of the first holding unit  41  at the position corresponding to those of the projections  383   a  to  383   d . The first guide grooves  44   a  to  44   d  may engage the projections  383   a  to  383   d  to prevent the probes  30  from being disassembled easily. 
     X-Direction Phase of Opening Projections 
     A relationship between the projections  383  of adjoining probes and the first guide grooves  44  will be illustrated in  FIGS. 5A to 6B . In adjoining probes  300   a  and  300   d , opening projections  383   a  to  383   d  of the probe  300   a  and opening projections  383   e  to  383   h  of the probe  300   d  are in a positional relationship illustrated in  FIGS. 5A and 5D  and having phase difference delta P 1  in the X direction. Corresponding thereto, the first guide grooves are in a positional relationship illustrated in  FIG. 6A . With this structure, as illustrated in  FIG. 6A , it is possible to arrange adjoining probes even at fine pitches without interference between adjoining guide grooves. Since the probes illustrated in  FIGS. 5A to 5D  are the same in structure as the probe illustrated in  FIG. 4 , some reference numerals are omitted in  FIGS. 5A to 5D . 
     Guide Structure of Vertical Probe 
     As illustrated in  FIG. 4 , second guide grooves  45  are formed on a side surface  421  of the second holding unit  42  at positions corresponding to those of projections  331  of the vertical probes  33 . The second guide grooves  45  guide the projections  331  to determine the positions of the vertical probes  33 . 
     Operation of Vertical Probe and Z-direction Length of Guide 
     Here, an operation of the probe  30  will be described with reference to  FIGS. 6A to 7B .  FIG. 7A  illustrates a state in which the probe tip  34  has started touching the electrode pad  100  and  FIG. 7B  illustrates a state in which the probe tip  34  is pressed against the electrode pad  100  by a predetermined displacement amount (“overdrive”) Od 21  in the Z direction. In this process, the projection  331  is also moved by the overdrive amount in the second guide groove  45 . Thus, the necessary length L 2  of the guide groove  45  in the Z direction is the sum total of the overdrive amount Od 21  and the Z-direction length d 2  of the projection  331 . 
     Z-direction Phase of Vertical Probe Projection 
     A relationship between the projections  331  of adjoining vertical probes and the second guide grooves  45  will be illustrated in  FIGS. 5A to 6B . In adjoining probes  300   a  to  300   c , a relative positional relationship among projections  331   a  to  331   c  of vertical probes of the probes  300   a  to  300   c  is illustrated in  FIGS. 5A to 5C  and having phase difference delta P 2  in the Z direction. Corresponding thereto, the second guide grooves are in a positional relationship illustrated in  FIG. 6B . With this structure, as illustrated in  FIG. 6B , it is possible to arrange adjoining probes even at fine pitches without interference between adjoining guide grooves. 
     Guide Structure of Output Terminal 
     Similarly, as illustrated in  FIG. 4 , third guide grooves  46  are formed on a side surface  431  of the third holding unit  43  at the same position as those of the first guide grooves  44  in the Y direction. The output terminal  36  includes an extended portion  361  which extends in the Z direction. The extended portion  361  is guided by the third guide groove  46 , whereby the output terminal  36  is positioned. 
     Z-Direction Phase of Projection in Output Terminal 
     A relationship between the projections  362  of adjoining output terminals and the third guide grooves  46  will be illustrated in  FIGS. 5A to 6B . In adjoining probes  300   a  to  300   c , a relative positional relationship among projections  362   a  to  362   c  of output terminals of the probes  300   a  to  300   c  is illustrated in  FIGS. 5A to 5C  and having phase difference delta P 3  in the Z direction. Corresponding thereto, the third guide grooves are in a positional relationship similar to that illustrated in  FIG. 6B . With this structure, as illustrated in  FIG. 6B , it is possible to arrange adjoining probes even at fine pitches without interference between adjoining guide grooves. 
     Operation of Output Terminal and Z-direction Length of Guide 
     An operation of the output terminal  36  will be described with reference to  FIGS. 6A to 7B .  FIG. 7A  illustrates a state before the output terminal  36  touches the pad  111  of the wiring board  110  and  FIG. 7B  illustrates a state in which the output terminal  36  is pressed against the pad  111  in the Z direction by a predetermined displacement amount Od 22 . In this process, the projection  362  is also moved in the Z direction by the displacement amount Od 22  in the third guide groove  46 . Thus, the necessary length L 3  of the guide groove  46  in the Z direction is the sum total of the Z-direction displacement amount Od 22  and the Z-direction length d 3  of the projection  362 . 
     Exemplary Method of Forming Guide Grooves 
     It is at least necessary that the guide grooves  44  to  46  are made of an electrically insulating material. An implementable method is to form desired guide grooves in, for example, non-conductive plastic resin and then attach the resin to the side surfaces  411 ,  412 ,  421  and  431  of the support rod  40 . Another method is to apply thermosetting resin, such as silicon, or ultraviolet curing resin (hereinafter, “resin”), to the side surfaces  411 ,  412 ,  421  and  431 , arrange the probes  30  in predetermined positions before the resin cures, and then let the resin cure. In this process, desired guide grooves  45  and  46  are formed by letting the projections  331  of the vertical probes  33  and the projections  362  of the output terminals  36  reciprocate in the Z direction by a necessary displacement amount at the time of curing of resin. 
     Probes for Alternate Arrangements 
       FIGS. 8A and 8B  illustrates an exemplary configuration to correspond to the fine-pitch pad arrangement which includes an alternate arrangement illustrated in  FIG. 9C . As illustrated in  FIG. 8A , there is phase difference delta Pr between the position of a probe tip  341  of a probe  301  in the X direction and the position of the probe tip  34  of the probe  30  in the X direction. As illustrated in  FIG. 8B , these probes  30  and  301  may be arranged adjacent to each other to correspond to alternate fine-pitch pad arrangements. Since the probe illustrated in  FIG. 8A  is the same in structure as the probe illustrated in  FIG. 8B , some reference numerals are omitted in  FIG. 8A . 
     In the structure described above, the probes  30  are supported by and fixed to the support rod  40  and, at the same time, are guided by the guide grooves formed in the support rod  40  while keeping phase difference in the Z direction between the projections  331  of adjoining vertical probes  33  and the projections  362  of adjoining output terminals  36 . There is therefore an effect that the probes  30  can be arranged even at fine pitches and that even thin plate-shaped probes are not easily deformed due to buckling, twisting or other causes. 
     As described above, according to the present invention, in a probe card used for inspection of semiconductor chips having fine-pitch pad arrangements, such as LCD-driving LSIs, it is possible to achieve a probe card which is capable of touching electrode pads including continuous fine-pitch pads in a precise and reliable manner and, at the same time, is manufactured with lower cost. 
     The invention has been described with reference to the preferred embodiments illustrated in the drawings. However, it is apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. The invention includes those modifications.