Abstract:
A socket for an electrical part comprises: a socket body on which an accommodation surface portion for accommodating the electrical part is provided; a plurality of contact pins provided on the socket body to be capable of contacting and separating from a terminal of the electrical part; and a movable plate relatively movable with respect to the socket body, the contact pin comprising an elastic piece which is elastically deformable and a contact portion provided on the front end portion of the elastic piece; the contact portion being displaced with the deformation of the elastic piece so as to separate the contact portion from the solder ball of the electrical part, wherein the solder ball is separated from the contact portion, when the solder ball is stuck to the contact portion, by abutting the solder ball against a back surface of the contact portion of another contact pin adjacent to the contact pin to which the solder ball is stuck.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a socket for electrical parts for detachably accommodating and holding an electrical part such as a semiconductor device (called as “IC package” hereinlater), and more particularly, the present invention relates to a socket for electrical parts that prevents a solder ball as a terminal of electrical parts from sticking to contact portions of contact pins. 
     2. Related Art of the Invention 
     As a conventional “socket for electrical parts” of this kind, there is provided an IC socket for detachably accommodating an IC package as an “electrical part”. 
     The IC package includes, for example, a BGA (Ball Grid Array) type of IC package in which solder balls as a number of terminals are provided to the lower surface of the package body so as to protrude downward in a grid (lattice) arrangement. 
     The IC socket is provided with a contact pin having a pair of elastic pieces (paired elastic pieces), on each tip portion of which a contact portion is formed to contact and separate from a side surface portion of the solder ball of the IC package. And one of the elastic pieces is designed to be elastically deformed by being pushed with a movable plate that can slide laterally (transversely). 
     With making the movable plate slide, one of the paired elastic pieces of the contact pin is elastically deformed so as to widen the distance between a pair of contact portions (paired contact portions). Next, the solder ball is inserted into the widened space between the paired contact portions. Then the movable plate moves back to its original position, so that the contact portion of the one of the elastic pieces goes back toward its original position, thereby the solder ball is clamped by the paired contact portions to electrically connect the solder ball and the contact pin. 
     In this state described above, such performance test as a burn-in test is carried out. After the testing, the movable plate is slid, as described above, to displace the contact portion of the one of the elastic pieces so as to widen the distance between both contact portions of the contact pin. The paired contact portions are to be separated from the solder ball. Then the IC package is drawn off from the IC socket using, for example, an automated machine. 
     According to the above-mentioned structure, the IC package is designed to be able to be inserted in and drawn off from the IC socket, without applying extra force, by only sliding the movable plate, aiming to improve the operation efficiency significantly. 
     However, in such conventional IC packages as mentioned above, the solder balls often stick to some contact portions of the contact pins, because the solder balls are softened by the heat applied to the IC package of up to about 125° C. during the burn-in test. Under these conditions, the solder ball often remains stuck to one of the paired contact portions and do not separate from the contact portion even when the distance of both contact portions are widened by displacing the contact portion of one of the elastic pieces. In these situations, it is often the case that the IC package can not be drawn off from the IC socket without applying extra force on the IC package. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to substantially eliminate defects or drawbacks encountered in the related art mentioned above and to provide a socket for electrical parts capable of drawing off the electrical parts from the socket without substantially applying extra force and preventing the contact portion of the contact pin from sticking to the solder balls. 
     This and other objects can be achieved according to the present invention by providing a socket for electrical parts of the present invention described hereunder. 
     A first aspect of the present invention is characterized in that, a socket for an electrical part which comprises:
         a socket body on which an accommodation surface portion is provided for accommodating the electrical part;   a plurality of contact pins provided on the socket body to be able to contact and separate from a terminal of the electrical part; and   a movable plate relatively movable with respect to the socket body,   the contact pin comprising an elastic piece which is elastically deformable and a contact portion provided on the elastic piece;   the contact portion being displaced with the elastic piece of the contact pin being elastically deformed by moving the movable plate, thereby separating the contact portion from the terminal of the electrical part,   wherein the terminal is separated from the contact portion, in a case when the contact pin is elastically deformed in an opened direction of the elastic portion and the terminal is stuck to the contact portion, by abutting the terminal against another elastic portion of another contact pin adjacent to the contact pin to which the terminal is stuck.       

     Another aspect of the present invention is characterized in that said contact pin has a pair of elastic pieces, and a first elastic piece of the pair of elastic pieces is elastically deformed, by moving the movable plate laterally in a parallel manner with respect to the accommodation surface portion, to displace the contact portion of the first elastic piece. 
     Still another aspect of the present invention is characterized in that said contact pin has a pair of elastic pieces, both of the elastic pieces are elastically deformed, by moving vertically the movable plate, to displace each of the contact portions of the elastic pieces. 
     Further aspect of the present invention is characterized in that both contact portions of the pair of elastic pieces of said contact pin are each disposed at an opposite side to each other with respect to a center line which is extended along a displacement direction of the elastic pieces. 
     Further aspect of the present invention is characterized in that said contact pin has one elastic piece, the elastic piece is elastically deformed, by moving vertically the movable plate, to displace the contact portion of the elastic piece. 
     Further aspect of the present invention is characterized in that said electrical part is a BGA package. 
     According to the aspects of the present invention described above, the terminal of the electrical part which is likely to stick to the contact portion can be separated from the contact portion at the time the contact portion of the contact pin is displaced, because the elastic piece of another contact pin adjacent to the contact pin that sticks to the terminal is designed to abut against the terminal that sticks to the contact portion. 
     Therefore, the electrical part can be drawn off from the socket for electrical parts without applying extra force, and the terminal can be surely separated from the contact portion because the elastic piece is designed to directly push the terminal in order to separate the terminal from the contact portion. Furthermore the amount of the opening of the contact portion can be ensured larger even in a case when the pitch between one contact pin and another contact pin adjacent to the one contact pin becomes narrower, because the contact portion of the one contact pin is designed to pass by another contact portion of the another contact pin when contact portions are opened to their fullest extent. 
     The nature and further characteristic features of the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a plan view of an IC socket according to the first embodiment of the present invention; 
         FIG. 2  is a sectional view taken along the line II—II of  FIG. 1 ; 
         FIG. 3  is a sectional view taken along the line III—III of  FIG. 1 ; 
         FIG. 4A  is a front view of an IC package used for the embodiment of the present invention; 
         FIG. 4B  is a bottom view of the IC package of  FIG. 4A ; 
         FIG. 5A  is a front view of a contact pin according to the first embodiment of the present invention; 
         FIG. 5B  is a sectional view taken along the line VB—VB of  FIG. 5A ; 
         FIG. 6A  is a sectional view of  FIG. 1 , showing an operation of the first embodiment, in which a solder ball is clamped by a pair of contact portions of the contact pin; 
         FIG. 6B  is a sectional view of  FIG. 1 , showing an operation of the first embodiment, in which the pair of contact portion of the contact pin is in a process of opening; 
         FIG. 6C  is a sectional view of  FIG. 1 , showing an operation of the first embodiment, in which the solder ball is separated from the contact portion of the contact pin; 
         FIG. 7  is an explanatory sectional view showing an operation of X-shape link of the first embodiment; 
         FIG. 8  is a sectional view showing a state where an operation member of the first embodiment is depressed; 
         FIG. 9  is a plan view of the IC socket of a second embodiment of the present invention; 
         FIG. 10  is a sectional view taken along the line X—X of  FIG. 9 ; 
         FIG. 11  is a sectional view taken along the line XI—XI of  FIG. 9 ; 
         FIG. 12  is a perspective view of the contact pin of the second embodiment; 
         FIG. 13A  is a sectional view showing an operation of the second embodiment in which a pair of contact portions of the contact pin are in a closed position; 
         FIG. 13B  is a sectional view showing an operation of the second embodiment in which the pair of contact portions of the contact pin are in an opened position; 
         FIG. 13C  is a sectional view showing an operation of the second embodiment in which the solder ball is in a state clamped by the contact portions of the contact pin; 
         FIG. 14A  is a sectional view showing an operation of the second embodiment in which the solder ball is in a state clamped by the contact portions of the contact pin; 
         FIG. 14B  is a sectional view showing an operation of the second embodiment in which the solder ball is in a state separated from the contact portions of the contact pin; 
         FIG. 15  is a sectional view showing a state an operation member of the second embodiment is depressed; 
         FIG. 16A  is a sectional view showing an operation of the second embodiment in which the operation member is in an elevated position; 
         FIG. 16B  is a sectional view showing an operation of the second embodiment in which the operation member is in a depressing position; 
         FIG. 17A  is a sectional view showing an operation of a third embodiment in which the contact portion of the contact pin is in a state contacted with the solder ball; 
         FIG. 17B  is a sectional view showing an operation of the third embodiment in which the solder ball is in a state separated from the contact portion of the contact pin. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A preferred embodiment of the present invention will be described hereunder with reference to the accompanying drawings. 
     Further, it is to be noted that the terms “upper”, “lower”, “vertical”, “horizontal” and like described herein are used in the illustrated state or usable state of the socket or members associated herewith and also that a number of contact pins and terminals are actually arranged, though the description may be made with reference to single one thereof for the sake of easy understanding of the present invention. 
     First Embodiment of the Present Invention 
       FIGS. 1  to  8  show the first embodiment of the present invention. 
     An IC socket as a “socket for electrical parts” is totally designated by reference numeral  11 , which is a device for establishing an electrical connection between a solder ball  12   b  as a “terminal” of an IC package  12  as an “electrical part” and a printed circuit board, not shown, of a tester, for example, for a performance test of the IC package  12 . 
     The IC package  12  is, for example, what is called a BGA (Ball Grid Array) type as shown in  FIGS. 4A and 4B , in which a number of spherical-shape solder balls  12   b  are arranged to the lower surface of a rectangular package body  12   a  in a manner projecting in matrix arrangement. 
     On the other hand, the IC socket  11  is generally including, as shown in  FIG. 2 , a socket body  13  to be mounted on the printed circuit board. A number of contact pins  15  to be contacted to or separated from the solder balls  12   b , respectively, are provided for the socket body  13 , and a slide plate  17  as a “movable plate” and a top plate  18  are layer-built in this order on the upper side of the socket body  13 . In addition, on the upper side of the top plate  18  an operation member  19  is provided so as to slide the slide plate  17  in a lateral (transverse) direction. 
     Each contact pin  15  is formed, through press working, of a plate member having a good electrical conductivity and elastic property so as to provide a shape shown in  FIGS. 5A and 5B . 
     More in detail, the contact pin  15  is composed of a fixed-side elastic piece  15   h  and a movable side elastic piece  15   i  (a pair of elastic pieces or a paired elastic pieces) at its upper portion, and a solder tail portion  15   b  at its lower portion. Each elastic piece  15   h  and  15   i  have a common base portion  15   c  at the lower portions thereof, as viewed in  FIG. 5B , and the base portion  15   c  has substantially a U-shape so that the paired elastic pieces  15   h  and  15   i  are opposed to each other. A fixed-side contact portion  15   d  and a movable side contact portion  15   e  are further formed at each upper end (front end) portions of elastic pieces  15   h  and  15   i  so as to be contacted with and separated from the side portions of the solder ball  12   b , and the solder ball  12   b  is clamped between the contact portions  15   d  and  15   e.    
     Both contact portions (or paired contact portions)  15   d  and  15   e , as shown in  FIGS. 6A ,  6 B and  6 C, in plan view, are each disposed at an opposite side to each other with respect to a center line O which passes through the center of the solder ball  12   b  and is parallel to a deformation direction of the movable side elastic piece  15   i.    
     The solder tail portion  15   b  and the base portion  15   c  of the contact pin  15  of the structure mentioned above are press-fitted into a press-fit hole  13   a  formed in the socket body  13 . The solder tail portion  15   b  projecting downward from the socket body  13  further extends downward through a location board  21 , and then is inserted into a through hole formed in the printed circuit board (not shown) and soldered thereto, thus being connected thereto. 
     The slide plate  17  is provided slidably in the right and left direction in  FIG. 2 ,  FIGS. 6A ,  6 B,  6 C and  FIG. 7  (approximately parallel direction to the accommodation surface portion  18   a  of the top plate, which will be explained later). When the slide plate  17  is moved to slide, the movable side elastic piece  15   i  of the contact pin  15  provided in the socket body  13  is elastically deformed, thereby the movable side contact portion  15   e  being displaced in a predetermined distance. 
     In a case where the solder ball  12   b  of the IC package  12  sticks to the fixed-side contact portion  15   d  or the movable side contact portion  15   e  during displacing the movable side contact portion  15   e  of the contact pin  15 , the solder ball  12   b  stuck to the fixed-side contact portion  15   d  or the movable side contact portion  15   e  is designed to be separated from the solder ball-stuck contact portion, by pushing the solder ball  12   b  with a back surface portion  15   f ,  15   g  of the fixed-side or movable side contact portion of another contact pin  15  adjacent to the solder ball-stuck contact pin  15 . 
     In order to realize the mechanism mentioned above, the movable side contact portion  15   e  is designed to be able to move to a place where the movable side contact portion  15   e  passes over the fixed-side contact portion  15   d  of the another contact pin  15  adjacent to the solder ball-stuck contact pin  15 , when the movable side contact portion  15   e  is opened to its fullest extent. 
     The slide plate  17  is designed to slide in concert with the movement of an X-shaped link  22 , as shown in FIG.  2  and  FIG. 7 , by vertically moving the operation member  19 . On the slide plate  17 , a pressing portion  17   a  is formed in order to push and elastically deform the movable side elastic piece  15   i  (see  FIGS. 6A ,  6 B and  6 C). 
     The X-shaped link  22  is provided on the both side surface portion which are provided along a slide direction of the quadrangular-shaped slide plate  17 . 
     More specifically, the X-shaped link  22  has, as shown in FIG.  2  and  FIG. 7 , a first link member  23  and a second link member  25 . These two link members have the same length and are connected rotatably by a central link pin  27 . 
     A lower end portion  23   a  of the first link member  23  is connected rotatably to the socket body  13  by a lower end link pin  29 . A lower end portion  25   a  of the second link member  25  is connected rotatably to one end portion of the side surface portion provided along the slide direction of the slide plate  17 , by a lower end link pin  30 . In addition, upper end portions  23   b ,  25   b  of the first and the second link members  23 ,  25  is connected rotatably to the operation member  19  by upper link pins  33 ,  34 . An ellipsoidal opening  23   c  is formed at the upper end portion  23   b  of the first link member  23  that is connected to the operation member  17  through the ellipsoidal opening  23   c  by the upper link pin  33 . 
     Further, the top plate  18  has the accommodation surface portion  18   a  on which the IC package  12  is accommodated and a guide portion  18   b , for guiding the IC package  12  to a predetermined position, at a place corresponding to each corner portion of a package body  12   a , as shown in FIG.  1  and FIG.  8 . 
     Further, the top plate  18  has a positioning portion  18   c  which is inserted between the pair of the contact portions  15   d  of each contact pin  15 . When no external force is applied on both elastic pieces  15   h ,  15   i  of the contact pin  15  (two contact portions  15   d  are in a closed state), the positioning portion  18   c  is clamped by both elastic pieces  15   h ,  15   i.    
     Further, as shown in  FIGS. 1 and 2 , the operation member  19  has an opening  19   a  having a size capable of inserting the IC package  12 . Through the opening  19   a , the IC package  12  is inserted and accommodated, at a predetermined position, on the accommodation surface portion  18   a  of the top plate  18 . The operation member  19 , as shown in  FIG. 3 , is provided vertically movable with respect to the socket body  13  and urged upward by a spring  36 , and is further provided with an operational projecting portion  19   b  for rotating a latch  38 . 
     As shown in  FIG. 8  etc., the latch  38  is attached to the socket body  13  to be rotatable around an axis  38   a  and urged by a spring  39  toward the center of the socket body  13  in  FIG. 8 , being designed to push down a peripheral portion  12   c  of the IC package body  12   a  with a pressing portion  38   b  formed at a tip end portion of the latch. 
     Furthermore, the latch  38  has a pressed portion  38   c  which is designed to be pressed by the operational projecting portion  19   b  of the operation member  19 . When the operation member  19  is depressed, the pressed portion  38   c  is pressed by the operational projecting portion  19   b , and the latch  38  is rotated toward outside from the socket  13  in  FIG. 8 , thereby the pressing portion  38   b  being retracted from a position where the IC package  12  is accommodated. 
     Next, operation of the socket for electrical parts will be explained hereunder. 
     In order to accommodate the IC package  12 , using an automated machine, on each IC socket  11  many of which are previously arranged on the printed circuit board, at first the operation member  19  is depressed. With this operation, the slide plate  17  is slid toward the right side by way of the X-shaped link  22  as shown by the chain double dashed line in FIG.  7 . And the movable side elastic piece  15   i  of the contact pin  15  is pressed, by the pressing portion  17   a  of the slide plate  17 , to be elastically deformed. On the other hand, the fixed-side elastic piece  15   h  is remained at a predetermined position by the positioning portion  18   c  of the top plate  18 . 
     According to the operation mentioned above, the pair of contact portions  15   d ,  15   e  of the contact pin  15  are made opened. 
     In the above mentioned structure, the fixed-side contact portion  15   d  is positioned at a side opposite to the movable side contact portion  15   e  with respect to the center line O (as shown in  FIGS. 6A ,  6 B and  6 C, in plan view). In a state where the movable side elastic piece  15   i  is fully opened, the movable side contact portion  15   e  is designed to pass by another fixed-side contact portion  15   d  of another contact pin  15  adjacent to the contact pin  15  so that the amount of opening of the movable elastic piece  15   i  (moving distance of the movable elastic piece  15   i ) can be larger than that of the conventional contact pin. 
     At the same time, the pressed portion  38   c  of the latch  38  is pressed by the operational projecting portion  19   b  of the operation member  19 , to be rotated anti-clockwise in  FIG. 2  against the urging force of the spring  39 . Thereby the pressing portion  38   b  is displaced to the recess position (see FIG.  8 ). 
     In this state, the IC package  12  carried by the automated machine is guided by the guide portion  18   b  and accommodated at a predetermined position on the accommodation surface portion  18   a  of the top plate  18 . And each solder ball  12   b  of the IC package  12  is inserted in non-contact manner into an opened space between the pair of contact portions  15   d  of each contact pin  15 . 
     Next, when force applied downward on the operation member  19  is released, the operation member  19  is moved upward by the urging force of the spring  36 . Then the slide plate  17  is slid toward the left side in  FIGS. 6A ,  6 B and  6 C through the X-shaped link  22  so that the latch  38  is rotated clockwise in  FIG. 2  by the urging force of the spring  39 . 
     When the slide plate  17  is slid toward left side in  FIGS. 6A ,  6 B and  6 C, the pressing force toward the movable side elastic piece  15   i  of the contact pin  15  is released so that the movable side elastic piece  15   i  can return back toward its original position. Accordingly the solder ball  12   b  is clamped between the contact portion  15   d  of the movable side elastic piece  15   i  and the contact portion  15   d  of the fixed-side elastic piece  15   h  (see FIG.  6 A). When the solder ball  12   b  is clamped, the fixed-side elastic piece  15   h  is elastically deformed slightly and slightly displaced toward a direction in which the contact portion  15   d  of the fixed-side elastic piece  15   h  is widened. 
     According to the movement of the socket mentioned above, each solder ball  12   b  of the IC package  12  is electrically connected to the printed circuit board through the contact pin  15 . 
     The IC package  12  thus accommodated on the IC socket  11  which is mounted on the printed circuit board is set up in a burn-in bath. Then the burn-in test of the IC package  12  is carried out by increasing the temperature in the bath to, for example, about 125° C. With increasing the temperature in the bath, the solder ball  12  is softened so that the side surface portion of the solder ball  12   b  often sticks to the movable side contact portion  15   e  or the fixed-side contact portion  15   d.    
     After the burn-in test, the IC package  12  is taken out from its accommodated position by depressing the operation member  19 . In concert with the move of the operation member  19 , as mentioned above, the slide plate  17  is slid toward right side from the position shown in  FIG. 6A , to a position in  FIG. 6B , to a position in FIG.  6 C. Accordingly the movable side elastic piece  15   i  is elastically deformed toward right side and the contact portion  15   e  of the movable side elastic piece  15   i  is displaced toward right side in these Figures. At this moment, if the solder ball  12   b  sticks to the movable side contact portion  15   e , the IC package  12  is moved to slide toward right side in Figures, with the movement of contact portion  15   e , so that the solder ball  12   b  is separated from the fixed-side contact portion  15   d  of the fixed-side elastic piece  15   h  (see FIG.  6 B). 
     Then each solder ball  12   b  abuts against the back surface portion  15   f  of the fixed-side contact portion  15   d  of another contact pin  15  which is adjacent to the contact pin  15 , on which the solder ball is sticking. 
     The movable side contact portion  15   e  of the movable side elastic piece  15   i  is designed to be further displaced beyond the position where the solder ball  12   b  is in the abutting condition against the back surface portion  15   f  mentioned above. Therefore if the movable side contact portion  15   e  of the movable side elastic piece  15   i  is further displaced toward right side in  FIGS. 6A ,  6 B and  6 C, by elastically displacing the movable side elastic piece  15   i , the solder ball  12   b  is pressed by the back surface portion of the fixed-side contact portion  15   d . Accordingly, the solder ball  12   b  is separated from the movable side contact portion  15   e  (see FIG.  6 C). 
     On the contrary, when the solder ball  12   b  sticks to the fixed-side contact portion  15   d  of one contact pin, the back surface portion of another movable side contact portion  15   e  of another contact pin, which is adjacent to the one contact pin, abuts against the solder ball  12   b . From this state, by further displacing another movable side contact portion  15   e  toward the opening direction thereof, another movable side contact portion  15   e  presses the solder ball  12   b . Accordingly, the solder ball  12   b  is separated from the fixed-side contact portion  15   d.    
     From the foregoing structure mentioned above, the solder ball  12   b  can be separated from the fixed-side contact portion  15   d  or the movable side contact portion  15   e  even if the solder ball  12   b  sticks to either of the fixed-side contact portion  15   d  or the movable side contact portion  15   e.    
     Especially, the solder ball  12   b  can be surely separated (detached) from the contact portion  15   d ,  15   e , because the back surface portion  15   f ,  15   g  of each contact portion  15   d ,  15   e  directly press each solder ball  12   b.    
     As mentioned above, the pair of contact portions  15   d ,  15   e  are separated from the solder ball  12   b  of the IC package  12  so that the IC package  12  can be drawn off from the IC socket  11  without applying any extra force using an automated machine. 
     Second Embodiment of the Present Invention 
       FIGS. 9  to  16 B show the second embodiment of the present invention. 
     In the first embodiment described above, the present invention is applied to what is called a single swing type contact pin (only one elastic piece of the contact pin (only one elastic piece of the paired elastic pieces) is deformed elastically by transverse (lateral) slide of the slide plate  17 ). But the second embodiment is applied to what is called a two swing type contact pin (both elastic pieces of the contact pins are deformed elastically by vertical moving of the slide plate). 
     Specifically, the IC socket  51  of the second embodiment has a socket body  53  mounted on a printed circuit board. The socket body  53  has a contact pin  55  which contacts and separates from each solder ball  12   b  and a movable plate  57  which displaces the contact pin  55 . Further, on the upper side of the movable plate  57 , an upper plate  59  is fixed to the socket body  53 . Still further an operation member  61  is provided which is designed to move the movable plate  57  vertically. 
     The contact pin  55  is formed from a plate having an elastic springy property and electric conductivity through press working and has a shape as shown in  FIG. 12  etc. 
     More specifically, a piece of elastic pieces  55   a  are formed in an approximately upper half portion of the contact pin  55 , and a solder tail portion  55   b  is formed in an approximately lower half portion thereof. The pair of elastic pieces (the paired elastic pieces)  55   a  are formed to be positioned opposite to each other by folding a base portion  55   c  of a lower end portion thereof to have approximately U shape. And at each upper end portion (upper tip end portion), a contact portion  55   d  is formed which contacts and separates from a side surface portion of the solder ball  12   b  of the IC package  12 , so that the solder ball  12   b  is clamped by the two contact portions (the paired contact portions). As shown in  FIGS. 14A and 14B , the paired contact portions  55   d  are each positioned opposite to each other with respect to a center line O which passes through the center of the solder ball  12   b  and is parallel to a deformation direction of the elastic pieces  55   a.    
     Each elastic piece of the paired elastic pieces  55   a  of the contact pin  55  has a bent portion  55   e  which is bent approximately in the shape of “&lt;” and these bent portions of the contact pin are positioned opposite to and crossed with each other as shown in  FIG. 12 , as will be described later, these bent portions  55   e  are designed to be pressed by a cam portion  57   a  so that the two contact portions  55   d  can be moved away from each other. 
     The distance between the paired contact portions  55   d , when the paired contact portions are opened to their fullest extent, is designed to make the solder ball  12   b  separate (detach) from the contact portions  55   d , by making one contact portion of one contact pin pass by another contact portion of another contact pin which is adjacent to the one contact pin  55  and by making a back surface portion  55   g  of the another contact portion  55   d  of the another contact pin  55  push the solder ball  12   b  which sticks to the contact portion  55   d.    
     The base portion  55   c  and the solder tail portion  55   b  of the contact pin  55  is press-fitted into a press fit hole  53   a  formed in the socket body  53  and the portion  55   f  formed at the base portion  55   c  is bitten into the socket body  53 , so that the contact pin  55  is prevented from dropping out upwards from the socket body. The solder tail portion  55   b  projecting downward from the socket body  53  is further projecting downward through a locate board  66  and inserted into each through hole of the printed circuit board (not shown) and connected by soldering thereto. 
     Further, the movable plate  57 , as shown in  FIG. 11 , is provided on the socket body  53  to be vertically movable and urged upward by a spring  62 . A pair of arms  63  for moving the movable plate  57  vertically is also provided (one of the paired arms  63  is not shown in FIG.  11 ). The arm  63  is attached to the socket body  53  by an axis  64  and also rotatably attached to the movable plate  57  by an axis  65 . An upper end portion  63   a  of the arm  63  is slidably engaging with a cam surface  61   a  of the operation member  61 . According to the structure mentioned above, when the operation member  61  is depressed, the arm  63  is rotated around the axis  64  anti-clockwise in  FIG. 11  by being pressed with the cam surface  61   a , thereby the movable plate  57  is moved downward. 
     As shown in  FIGS. 13A ,  13 B,  13 C and  14 A and  14 B, the movable plate  57  has cam portions  57   a  which are disposed between each contact pin  55 . At both side portions of the cam portions  57   a , sliding surfaces  57   b  are provided and are designed to press the bent portions  55   e  of the elastic pieces  55   a  of the contact pins  55  adjacent to each other on both sides of the cam portion. In other words, one cam portion  57   a  is designed to press the bent portions  55   e  of the elastic pieces  55   a  of both adjacent contact pins  55 . Both bent portions  55   e  of the paired elastic pieces  55   a  of the contact pin  55  are designed to be pressed, by a pair of cam portions  57   a  positioned each at both sides of the contact pin  55 , to come close to each other, so that the paired contact portions  55   d  can be made opened (or the distance between the paired contact portions can be made longer). 
     The upper plate  59  has an accommodation surface portion  59   a  on which the IC package  12  is accommodated and a guide portion  59   b  for guiding the IC package  12  to a predetermined position. The guide portion  59   b  is provided at a place corresponding to each corner portion of the package body  12   a  as shown in FIG.  9 . Furthermore, the upper plate  59  has a positioning rib  59   c  which is inserted between the paired contact portions  55   d  of each contact pin  55 . The positioning rib  59   c  is clamped between the paired elastic pieces  55   a  when no external force is applied on the paired elastic pieces  55   a  of the contact pin  55  (the paired contact potions  55   d  is in a closed state). 
     Further, the operation member  61 , as shown in Figures, has an opening  61   b  wide enough to insert the IC package  12 . Through the opening  61   b , the IC package  12  is inserted and accommodated at a predetermined position on the accommodation surface portion  59   a  of the upper plate  59 . The operation member  61  is, as shown in  FIGS. 10 and 11 , is provided to be vertically movable with respect to the socket body  53  and urged upward by a spring  67 . An engaging claw  61   d  is engaged with an engaged portion of the socket body  53  at its maximum elevated position of the operation member  61 , so that the operation member  61  can be prevented from coming off. 
     Further the operation member  61  has a cam surface  61   a  for rotating the arm  63  and an operation portion  61   c  for rotating a latch  68  as well, as shown in  FIGS. 16A and 16B . 
     The latch  68 , as shown in  FIGS. 16A and 16B  etc., is attached to the socket body  53  by an axis  68   a  and can move around the axis  68   a . The latch  68  is urged by a spring  69  anti-clockwise and designed to hold a peripheral portion of the IC package  12  with a pressing portion  68   b  formed at a tip end portion thereof. 
     Further, the latch  68  has a pressed portion  68   c  on which the operation portion  61   c  of the operation member  61  slides. When the operation member  61  is depressed, the pressed portion  68   c  slides on the operation portion  61   c , to rotate the latch  68  clockwise as shown in FIG.  16 B. Thus the pressing portion  68   b  retracts (moves) from the accommodation position of the IC package  12 . 
     Next, the operation of the second embodiment will be explained. 
     In order to accommodate the IC package  12  on the IC socket  51 , the operation member  61  is first depressed. With this operation, the arm  63  is rotated anti-clockwise, as shown in  FIG. 15 , by the cam surface  61   a  of the operation member  61 , so that the movable plate  57  is depressed. With the downward movement of the movable plate  57 , from the state shown in  FIG. 13A  to the state shown in  FIG. 13B , the cam portion  57   a  is also depressed to push (press) the bent portion  55   e  of one contact pin  55  by the sliding surface  57   b  of the cam portion  57   a . Thus the paired contact portions (a pair of contact portions of the contact pin)  55   d  are opened as shown in FIG.  13 B. 
     At this moment, each contact portion  55   d  of the one contact pin  55  passes by each contact portion of another contact pin which is adjacent to the one contact pin, to crisscross with each other, so that a necessary distance between the paired contact portion (the amount of opening of the paired contact portion)  55   d  of the contact pin, at the time the paired contact portions are opened, can be ensured even in a case when the pitch of the contact pin arrangement is made narrower. 
     In addition, the operation portion  61   c  of the operation member  61  pushes the pressed portion  68   c  of the latch  68  so that the latch  68  is rotated clockwise against the urging force of the spring  69 , from the state shown in  FIG. 16A  to the state shown in FIG.  16 B. Thereby the pressing portion  68   b  is retracted to a recess position. 
     At this stage, the IC package  12  is guided along the guide portion  59   b  and accommodated to a predetermined position on the accommodation surface portion  59   a  of the upper plate  59 . And each solder ball  12   b  of the IC package  12  is inserted between the opened paired contact portions  55   d  of each contact pin  55  without contacting the paired contact portions. 
     Thereafter, with releasing the downward pressing force applied to the operation member  61 , the operation member  61  is moved upward by the urging force of the spring  67  etc. and the movable plate  57  is moved upward by the spring  62 . Then the latch  68  is rotated anti-clockwise in  FIGS. 16A and 16B  by the urging force of the spring  69 . 
     When the movable plate  57  is moved upward, the pressing force applied on the bent portion  55   e  of the contact pin  55  by the cam portion  57   a  is removed so that the paired contact portions  55   d  moves to a closing (narrowing) direction, thereby the solder ball  12   b  is clamped by the paired contact portions  55   d  (see FIG.  13 C). 
     Thus, each solder ball  12   b  of the IC package  12  and the printed circuit board are electrically connected through the contact pin  55 . 
     When the IC package  12  is taken out from the accommodation state, the operation member  61  is depressed to open the paired contact portions  55   d  of the contact pin  55 . At this stage, if a solder ball  12   b  sticks to either side of the paired contact portions, the IC package  12  is moved together with the contact portion  55   d  which sticks to the solder balls  12   b.    
     When the paired contact portions  55   d  are further opened from the above mentioned state, the solder ball  12   b  is pushed by the back surface portion of the contact portion  55   d  of the adjacent contact pin  55  as shown in FIG.  14 B. Thus the solder ball  12   b  is separated from the contact portion  55   d  to which the solder ball  12   b  sticks. 
     In this state the IC package  12  can be taken out easily with weaker force than the conventional state where the solder ball  12   b  is clamped by the paired contact portion  55   d.    
     Accordingly, even in a case that a solder ball  12   b  sticks to a contact portion, the solder ball  12   b  can be separated from the contact portion  55   d  without increasing the number of parts for the socket, because the back surface portion of another contact portion  55   d  of another contact pin  55  adjacent to the contact pin to which the solder ball  12   b  sticks is designed to push the solder ball  12   b.    
     Third Embodiment of the Present Invention 
       FIGS. 17A and 17B  show the third embodiment of the present invention. 
     In the second embodiment mentioned above, a pair of elastic pieces  55   a  are formed on each contact pin  55 , but in the third embodiment only one elastic piece  55   a  is formed on each contact pin  55 . 
     In the third embodiment, the solder ball  12   b  can be separated (detached) from one contact portion  55   d  to which the solder ball  12   b  sticks, because the back surface portion of another contact portion  55   d  of another contact pin  55  adjacent to the one contact pin, is designed to push the solder ball  12   b  (see FIG.  17 B). 
     The embodiment mentioned above can all be used for an IC socket  11  as a “socket for electrical parts”, the present invention however is not limited to such an IC socket and can also be applicable to other devices or like.