Abstract:
A socket connector and a contact for use in a socket connector is disclosed. The socket connector includes a plurality of contacts arranged in a grid shape and a socket body provided with the respective contacts. The contact includes a first contact piece and a second contact piece out of contact with each other in a first condition and in contact with each other in a second condition. When the first and second contact piece are in conctact with each other, the electric path length is shortened to reduce a self-inductance, thereby allowing the socket connector of the present invention to be used in high frequency application and in test and evaluation sockets.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a socket connector and a contact for use in a socket connector, and more particularly, a socket connector for use in high frequency applications and in test and evaluation sockets.  
         BACKGROUND OF THE INVENTION  
         [0002]    A socket for a semiconductor package with a plurality of solder balls arranged in a grid shape has been conventionally known in, for example, Japanese Patent Application Laid-open No. Hei 8-222335. As shown in FIGS.  13  to  15 , the socket  300  disclosed in the publication is provided with a contact  305  provided with a substantially U-shaped cross-sectional base  302  formed by punching out of a metal plate and having side walls  301  on both sides, a substantially C-shaped elastic contact piece  303  extending from the lower portion of the base  302  to the side wall  301  side, extending upwardly of the base  302  and having a contact portion  303   a  contacting in the vicinity of the tip end with a solder ball S owned by an IC package  400 , and a contact portion  304  extending from the lower end portion of the base  302  to the opposite side to the contact piece  303 .  
           [0003]    However, in the above-described conventional socket, in order that the solder ball S is in pressure contact with the contact portion  303   a , the contact piece  303  is formed as an arcuate leaf spring. For this reason, it is difficult to shorten an electric path length from the contact portion  303   a  to the contact portion  304 , it is impossible to reduce a self-inductance and it is impossible to test or evaluate the semiconductor package in a high frequency range. A socket, of the type shown in FIG. 16, provided at its upper and lower ends with contact portions and provided with a contact having a spring therebetween suffers from the same problems as described above.  
         SUMMARY OF THE INVENTION  
         [0004]    An object of the present invention is to provide a socket capable of performing a test or an evaluation of a semiconductor package in a high frequency range.  
           [0005]    Another object of the present invention is to provide a socket connector for using in a high frequency range.  
           [0006]    Another object of the present invention is to provide a socket in which the electric path length is shortened to reduce a self-inductance to thereby make it possible to perform a test or an evaluation of a semiconductor package (such as an IC package) in a high frequency range, and a contact for being mounted on the socket.  
           [0007]    In one embodiment of the present invention, the novel contact is used in a test evaluation socket for a semiconductor package, although the contact is not limited solely to test socket applications. Rather, the novel contact may be used in any application where shortened electric path length is desired.  
           [0008]    In one embodiment, the contact includes an arcuate leaf spring portion, a fixture portion for fixing said leaf spring portion to said socket connector, a contact portion provided at one end of said leaf spring portion, a conductive pattern contact portion provided at the other end of said leaf spring portion, a first contact piece provided at one end of said leaf spring, extending toward the other end of said leaf spring portion, and shiftable relative to said fixture portion, and a second contact piece provided at the other end of said leaf spring portion, extending toward one end of said leaf spring portion, and shiftable relative to said fixture portion.  
           [0009]    The first contact piece and said second contact piece are set so as to be out of contact with each other in a first condition and in contact with each other in a second position.  
           [0010]    The contact may contact with either a solder ball or a pin contact from the device being placed in contact with the contact.  
           [0011]    The first contact piece and said second contact piece may be set so as to form an electric path length substantially in a linear form under the condition that said first contact piece and said second contact piece are in contact with each other.  
           [0012]    Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS  
       [0013]    The features of this invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with its objects and the advantages thereof, may be best understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements in the figures and in which:  
         [0014]    [0014]FIG. 1 is a plan view showing a test evaluation socket in accordance with an embodiment of the present invention.  
         [0015]    [0015]FIG. 2 is a cross-sectional view showing a condition that the semiconductor package is mounted on the substrate connector in accordance with the embodiment of the present invention.  
         [0016]    [0016]FIG. 3 is a perspective view of a contact provided in the test evaluation socket in accordance with the embodiment of the present invention.  
         [0017]    [0017]FIG. 4 is a perspective view of the contact provided in the test evaluation socket in accordance with the embodiment of the present invention.  
         [0018]    [0018]FIG. 5 is a partially enlarged view of an A-A sectional view shown in FIG. 1.  
         [0019]    [0019]FIG. 6 is a partially enlarged view of a B-B sectional view of the test evaluation socket shown in FIG. 1.  
         [0020]    [0020]FIG. 7 is a partially enlarged view of a bottom surface  14  shown in FIG. 1.  
         [0021]    [0021]FIG. 8 is a plan view showing a test evaluation socket in accordance with another embodiment of the present invention.  
         [0022]    [0022]FIG. 9 is a cross-sectional view of the test evaluation socket shown in FIG. 8.  
         [0023]    [0023]FIG. 10 is a cross-sectional view of the test evaluation socket shown in FIG. 8.  
         [0024]    [0024]FIG. 11 is a cross-sectional view of the test evaluation socket shown in FIG. 8.  
         [0025]    [0025]FIG. 12 is a cross-sectional view of the test evaluation socket shown in FIG. 8.  
         [0026]    [0026]FIG. 13 is a view illustrative of a conventional socket.  
         [0027]    [0027]FIG. 14 is a frontal view of a contact provided in the conventional socket.  
         [0028]    [0028]FIG. 15 is a side view of the contact provided in the conventional socket.  
         [0029]    [0029]FIG. 16 is a view illustrative of the contact provided in the conventional socket. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]    A test evaluation socket for a semiconductor package in accordance with an embodiment of the present invention will now be described with reference to the accompanying drawings.  
         [0031]    As shown in FIGS. 1, 2 and  7 , the test evaluation socket  10  is a BGA (Ball Grid Array) test evaluation socket for a semiconductor package  50  having on its bottom surface a plurality of solder balls S arranged in a grid shape. The test evaluation socket  10  is provided with a plurality of contacts  11 , arranged in a grid shape corresponding to the arrangement of the solder balls S and a socket body  12  provided with the respective contacts  11 .  
         [0032]    As shown in FIGS. 3, 5 and  6 , each contact  11  is formed by bending a conductive metal plate. Each contact  11  is provided with an arcuate leaf spring portion  11   a , a fixture portion  11   b  press fitted in a contact receiving hole  16  formed in the socket body  12  for fixing a substantially middle portion of the leaf spring portion  11   a , a solder ball contact portion  11   c  provided outside one end of the leaf spring portion  11   a  and in pressing contact with the solder ball S, a conductive pattern contact portion  11   d  provided outside the other end of the leaf spring portion  11   a  and in pressing contact with a conductive pattern (not shown) of a substrate B, an upper contact piece  11   e  as a first contact piece provided at one end of the leaf spring portion  11   a , extending in a linear manner toward the other end of the leaf spring portion  11   a , and shiftable relative to the fixture portion  11   b , and a cantilever type lower contact piece  11   f  as a second contact piece provided at a side surface of the other end of the leaf spring portion  11   a , extending in a linear manner toward one end of the leaf spring portion  11   a , and shiftable relative to the fixture portion  11   b.    
         [0033]    Each length of the upper contact piece  11   e  and the lower contact piece  11   f  and each bending angle thereof to the leaf spring portion  11   a  are set such that the contact pieces are not brought into contact with each other under the condition that the solder ball S is not in contact with the solder ball contact portion  11   c  and the conductive pattern of the substrate B is not in contact with the conductive pattern contact portion  11   d  (see the contact  11  indicated by dotted lines in FIGS. 5 and 6).  
         [0034]    Also, each length of the upper contact piece  11   e  and the lower contact piece  11   f  and each bending angle thereof to the leaf spring portion  11   a  are set such that the contact pieces are brought into contact with each other under the condition that the solder ball S is in pressing contact with the solder ball contact portion  11   c , the conductive pattern of the substrate B is in pressing contact with the conductive pattern contact portion  11   f  and both the upper contact piece and the lower contact piece are shifted in a direction close to each other (see the contact  11  indicated by solid lines in FIGS. 5 and 6).  
         [0035]    A slant surface  11   g  with which the lower contact piece  11   f  contacts is provided on the side surface of the upper contact piece  11   e . With respect to the slant surface  11   g , the tip end of the lower contact piece  11   f  is brought into linear contact with the slant surface  11   g  and moved relative thereto and along therewith in the process that the solder ball S comes into pressing contact with the solder ball contact portion  11   c  and the conductive pattern of the substrate B comes into pressing contact with the conductive pattern contact portion  11   d  so that the upper contact piece  11   e  and the lower contact piece  11   f  are shifted in the direction close to each other. The contact  11  indicated by the dotted lines in FIGS. 5 and 6 represents a position before the shift and the contact  11  indicated by the solid lines represents a position after the shift.  
         [0036]    The upper contact piece  11   e  and the lower contact piece  11   f  are set in a linear condition so as to form the electrical path length substantially in the linear manner under the condition that they are brought into contact with each other (see FIGS. 4, 5 and  6 ).  
         [0037]    As shown in FIGS. 1 and 2, a socket body  12  is formed into a box-shape having a substantially rectangular form in plane and is provided with an opening  13  into which the semiconductor package  50  is to be inserted, and a plurality of contact receiving holes  16 , extending from the semiconductor package carrier surface  14  to a substrate facing surface  15 . Also, bosses  15   a  that are to be inserted into boss holes (not shown) formed in the substrate B are provided in the substrate facing surface  15 .  
         [0038]    Each contact receiving hole  16  is arranged in the grid shape corresponding to the arrangement of the solder balls S. As shown in FIGS. 5 and 6, solder ball receiving spaces  16   a  are located on the upper side of each contact receiving hole  16 .  
         [0039]    Each contact  11  is received in the associated receiving hole  16  with its solder ball contact portion  11   c  located in the solder ball receiving space  16   a  and its conductive pattern contact portion  11   d  projecting from the substrate facing surface  15  (i.e., the condition indicated by the dotted lines of FIGS. 5 and 6).  
         [0040]    The operation of the test evaluation socket  10  for the semiconductor package with the above-described structure will now be described with reference to the drawings.  
         [0041]    First of all, the bosses  15   a  provided, respectively, at four corners of the bottom surface of the socket body  12  are inserted into the boss holes formed in the substrate B. Then, the socket body  12  and the substrate B are fixed to each other by means of the screw fastening holes  15   b  and screws N 1  inserted in the screw holes formed in the substrate B and nuts N 2 . Under this condition, the conductive pattern contact portion  11   d  projecting from the substrate facing surface  15  of the socket body  12  is in pressing contact with the conductive pattern of the substrate B. Thus, the lower contact piece  11   f  is shifted in the direction close to the upper contact piece  11   e.    
         [0042]    Subsequently, the semiconductor package  50  is inserted into the opening  13  of the socket body  12  and pressed against the semiconductor package carrier surface  14 . Since the solder ball contact portion  11   c  of the contact  11  is located in the solder ball receiving space  16   a , when the semiconductor package  50  is depressed against the semiconductor package carrier surface, the solder ball S is brought into pressing contact with the solder ball contact portion  11   e  and the upper contact piece  11   e  is shifted in the direction close to the lower contact piece  11   f . The amount of shift thereof is limited by the contact of the lower surface (solder ball arrangement surface) of the semiconductor package  50  with the semiconductor package carrier surface  14 .  
         [0043]    Since the slant surface  11   g  with which the lower contact piece  11   f  contacts is provided on the side surface of the upper contact piece  11   e , under the process that the upper contact piece  11   e  and the lower contact piece  11   f  are shifted in the direction close to each other as described above, the slant surface  11   g  is brought into linear contact with the tip end of the lower contact piece  11   f  which is relatively moved to the slant surface  11   g . Accordingly, since the respective amounts of shift in the upper and lower directions of the upper contact piece  11   e  and the lower contact piece  11   f  may be increased, it is possible to obtain the sufficient pressing contact by the action of the leaf spring portion  11   a . The contact  11  shown by the dotted lines in FIG. 5 represents the position before the shift and the contact  11  indicated by the solid lines in FIG. 6 represents the position after the shift.  
         [0044]    Also, since the upper contact piece  11   e  and the lower contact piece  11   f  both extend in the linear manner, a new, substantially linear shortest electrical path length may be formed under the condition that the contact pieces are brought into linear contact with each other (see FIGS. 4, 5 and  6 ). Accordingly, it is possible to reduce the electrical path length to reduce the self-inductance, whereby it becomes possible to perform the test or the evaluation of the semiconductor package  50  in the high frequency range. Also, since the upper contact piece  11   e  and the lower contact piece  11   f  are brought into linear contact with each other, it is possible to ensure further stabilized and excellent contact.  
         [0045]    The semiconductor package  50  may be depressed against the semiconductor package carrier surface  14  by the well known mechanical device or by the manual work by the worker. Incidentally, the socket  10  and the contact  11  may also be used as PGA (Pin Grid Array) socket.  
         [0046]    A test evaluation socket for a semiconductor package in accordance with another embodiment of the present invention will now be described with reference to the drawings. Incidentally, the contact applied to the present socket is the same as that described above, the same reference numerals are used for explanation.  
         [0047]    [0047]FIG. 8 is a plan view of the test evaluation socket in accordance with the other embodiment of the present invention. FIGS.  9  to  12  are cross-sectional views of the test evaluation socket shown in FIG. 8.  
         [0048]    As shown in FIGS. 8 and 9, the test evaluation socket  110  is a test evaluation socket for a semiconductor package  150  having around its outer circumference a plurality of pin terminals P. The test evaluation socket  110  is provided with a plurality of contacts  11 , arranged correspondingly to the arrangement of the pin terminals P and a socket body  112  provided with the respective contacts  11 .  
         [0049]    As shown in FIGS. 3, 9 and  12 , each contact  11  is formed by means of a bending work of a conductive metal plate. Each contact  11  is provided with an arcuate leaf spring portion  11   a , a fixture portion  11   b  press fitted in a contact receiving hole  116  formed in the socket body  112  for fixing a substantially middle portion of the leaf spring portion  11   a , a pin terminal contact portion  11   c  provided outside one end of the leaf spring portion  11   a  and in pressing contact with the pin terminal P, a conductive pattern contact portion  11   d  provided outside the other end of the leaf spring portion  11   a  and in pressing contact with a conductive pattern (not shown) of the substrate B, an upper contact piece  11   e  as a first contact piece provided at one end of the leaf spring portion  11   a , extending in a linear manner toward the other end of the leaf spring portion  11   a , and shiftable relative to the fixture portion  11   b , and a cantilever type lower contact piece  11   f  as a second contact piece provided at a side surface of the other end of the leaf spring portion  11   a , extending in a linear manner toward one end of the leaf spring portion  11   a  and shiftable relative to the fixture portion  11   b.    
         [0050]    Each length of the upper contact piece  11   e  and the lower contact piece  11   f  and each bending angle thereof to the leaf spring portion  11   a  are set such that the contact pieces are not brought into contact with each other under the condition that the pin terminal P is not in contact with the pin terminal contact portion  11   c  and the conductive pattern of the substrate B is not in contact with the conductive pattern contact portion  11   d  (see the contact  11  as indicated by dotted lines in FIGS. 3 and 11).  
         [0051]    Also, each length of the upper contact piece  11   e  and the lower contact piece  11   f  and each bending angle thereof to the leaf spring portion  11   a  are set such that the contact pieces are brought into contact with each other under the condition that the pin terminal P is in pressing contact with the pin terminal contact portion  11   c , the conductive pattern of the substrate B is in pressing contact with the conductive pattern contact portion  11   f , and both the upper contact piece and the lower contact piece are shifted in a direction close to each other (see the contact  11  indicated by solid lines in FIG. 11).  
         [0052]    A slant surface  11   g  with which the lower contact piece  11   f  contacts is provided on the side surface of the upper contact piece  11   e . With respect to the slant surface  11   g , the tip end of the lower contact piece  11   f  brought into linear contact with the slant surface  11   g  and moved relative thereto and along therewith in the process that the pin terminal P comes into pressing contact with the pin terminal contact portion  11   c  and the conductive pattern of the substrate B comes into pressing contact with the conductive pattern contact portion  11   d  so that the upper contact piece  11   e  and the lower contact piece  11   f  are shifted in the direction close to each other (see FIGS. 9, 10 and  11 ). The contact  11  indicated by the dotted line in FIG. 11 represents a position before the shift and the contact  11  indicated by the solid line represents a position after the shift.  
         [0053]    The upper contact piece  11   e  and the lower contact piece  11   f  are set in a linear condition so as to form the electrical path length substantially in the linear manner under the condition that they are brought into contact with each other (see FIGS. 4, 11 and  12 ).  
         [0054]    As shown in FIG. 8, a socket body  112  is formed into a box-shape having a substantially rectangular form in plane and is provided with an opening  113  into which the semiconductor package  150  is to be inserted. The semiconductor package  150  includes a semiconductor package carrier plate  114  mounted on a bottom surface  113   a  of the opening  113  of the socket body  112  through springs SP and is reciprocatingly movable between a first position (upper end position) and a second position (lower end position) within the opening  113 .  
         [0055]    The upper end position is a position where the semiconductor package  150  is laid on the semiconductor package carrier plate  114  with its pin terminals P projected from a circumferential edge of the semiconductor package carrier plate  114  (see FIG. 9). The lower end position is a position where the projected pin terminals P comes into pressing contact with the pin terminal contact portions  11   c  (see FIG. 11).  
         [0056]    Also, the socket body  112  is provided with a substrate facing surface  115  opposite to the bottom surface  113   a  and a plurality of contact receiving holes  116 , bored through from the bottom surface  113   a  to the substrate facing surface  115 . Also, bosses  115   a  to be inserted into the boss holes (not shown) formed in the substrate B are provided in the substrate facing surface  115 .  
         [0057]    Each contact receiving hole  16  is arranged correspondingly to the arrangement of the pin terminals P. Each contact  11  is received in the associated contact receiving hole  116  with its pin terminal contact portion  11   c  projected from the bottom surface  113  and its conductive pattern contact portion  11   d  projected from the substrate facing surface  115  (i.e., the condition indicated by dotted line of FIG. 11).  
         [0058]    The operation of the test evaluation socket  110  for the semiconductor package with the above-described structure will now be described with reference to the drawings.  
         [0059]    First of all, the bosses  115   a  provided, respectively, at four corners of the bottom surface of the socket body  112  are inserted into the boss holes formed in the substrate B. Then, the socket body  112  and the substrate B are fixed to each other by means of the screw fastening holes  115   b  and screws N 1  inserted in the screw holes formed in the substrate B and nuts N 2 . Under this condition, the conductive pattern contact portion  11   d  projecting from the substrate facing surface  115  of the socket body  112  is brought into pressing contact with the conductive pattern of the substrate B. Thus, the lower contact piece  11   f  is shifted in the direction close to the upper contact piece  11   e.    
         [0060]    Subsequently, the semiconductor package  150  is inserted into the opening  113  of the socket body  112  and pressed against the semiconductor package carrier plate  114 . Since the semiconductor package carrier plate  114  is mounted on the bottom surface  113   a  of the opening  113  of the socket body  112  through the springs SP, when the semiconductor package  150  is depressed against the semiconductor package carrier plate  114 , the pin terminal contact portion  11   e  is brought into pressing contact with the pin terminal contact portion  11   c  and the upper contact piece  11   e  is shifted in the direction close to the lower contact piece  11   f . The amount of shift thereof is limited by the contact of the lower surface of the semiconductor package carrier plate  114  with the bottom surface  113   a  of the opening  113 .  
         [0061]    Since the slant surface  11   g  with which the lower contact piece  11   f  contacts is provided on the side surface of the upper contact piece  11   e , under the process that the upper contact piece  11   e  and the lower contact piece  111   f  are shifted in the direction close to each other as described above, the slant surface  11   g  is brought into linear contact with the tip end of the lower contact piece  11   f  which is relatively moved to the slant surface  11   g . Accordingly, since the respective amounts of shift in the upper and lower directions of the upper contact piece  11   e  and the lower contact piece  11   f  may be increased, it is possible to obtain the sufficient pressing contact by the action of the leaf spring portion  11   a . The contact  11  shown by the dotted line in FIG. 11 represents the position before the shift and the contact  11  indicated by the solid line represents the position after the shift.  
         [0062]    Also, since the upper contact piece  11   e  the lower contact piece  11   f  both extend in the linear manner, a new, substantially linear shortest electrical path length may be formed under the condition that the contact pieces are brought into contact with each other (FIGS. 4, 11 and  12 ). Accordingly, it is possible to reduce the electrical path length to reduce the self-inductance, whereby it becomes possible to perform the test or the evaluation of the semiconductor package  50  in the high frequency range. Also, since the upper contact piece  11   e  and the lower contact piece  11   f  are brought into linear contact with each other, it is possible to ensure further stabilized and excellent contact.  
         [0063]    The semiconductor package  150  may be gripped by the well known mechanical device M or depressed against the semiconductor package carrier surface  14  by the manual work by the worker.  
         [0064]    It will be understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.