Abstract:
An IC socket is disclosed which facilitates automatic mounting of an IC package without a fear of lead terminal deformation and reduces the number of steps of assembling contacts into a socket body. The IC socket is an open top type IC socket which includes a socket body; and a cover member mounted vertically movable to the socket body to open and close contacts, wherein the socket body has a mounting portion on which to support an IC package mounted on the socket, and the cover member has a square opening facing the mounting portion and inclined guide wall surfaces leading to the opening and adapted to guide the mounted IC package onto the mounting portion.

Description:
This application is based on Patent Application No. 2001-063994 filed Mar. 7, 2001 in Japan, the content of which is incorporated hereinto by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an IC socket used for inspecting IC packages in a semiconductor device manufacturing process and more particularly to an open top type IC socket which has a socket body and a cover member attached vertically movable to the socket body to open and close contacts. 
     2. Description of the Related Art 
     In this kind of conventional IC sockets, to efficiently mount and position mass-produced IC packages in an IC socket by using a robot, it is conventional practice to provide a socket body with inclined guide walls that restrict and guide movement of an IC package or to form guide posts projecting at corners of the socket body and guide the IC package with its lead terminals being in contact with the guide posts. 
     In the conventional IC socket of a type having the inclined guide walls on the socket body, however, the assembly into the socket body of a plurality of contacts, which are to be connected with the lead terminals of an IC package, is not easy as it is hindered by the inclined guide wall rising above the contacts, thus increasing the number of assembly steps. 
     On the other hand, in a type having guide posts projecting at corners of the socket body, since the lead terminals contacting the guide posts are limited to those present at the corners of the IC package, a load bears on only the contacting lead terminals, giving rise to a possibility of these lead terminals being deformed. 
     Another drawback is that the projecting guide posts become a hindrance and limit the moving path of the robot when the robot holds the IC package by suction and mounts it on the IC socket. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an IC socket which can solve the above-described problem and which can facilitate automatic mounting of an IC package without fear of lead terminal deformation and reduce the number of steps in assembling the contacts into the socket body. 
     In the first aspect of the present invention, there is provided an open top type IC socket comprising: 
     a socket body; and 
     a cover member mounted vertically movable to the socket body to open and close contacts; 
     wherein the socket body has a mounting portion to support an IC package mounted on the socket, and the cover member has a square opening facing the mounting portion and inclined guide wall surfaces leading to the opening and adapted to guide the IC package to be mounted onto the mounting portion. 
     Here, at least two opposing sides of the opening substantially may match with an envelope joining tips of lead terminals extending from the IC package to be mounted. 
     The inclined guide wall surfaces may be arranged symmetrical with respect to longitudinal and lateral center lines of the square opening and each may comprise a first inclined guide wall surface traversing each of the center lines, a second inclined guide wall surface provided at each corner portion and having an inclination angle larger than an inclination angle of the first inclined guide wall surface, and a third inclined guide wall surface connecting to the first and second inclined guide wall surfaces. 
     A plurality of fixed contacts may be arranged around the mounting portion and two opposing sides of the opening substantially may match with an envelope joining outer ends of the fixed contacts. 
     In the second aspect of the present invention, there is provided an IC socket comprising: 
     a socket body having a mounting portion for supporting an IC package and a plurality of contacts arranged around the mounting portion to come into contact with tips of lead terminals extending from the IC package; and 
     a cover member having an opening at a center thereof and mounted vertically movable to the socket body to open and close the contacts; 
     wherein the opening has its lower edge formed into a square facing the mounting portion and has inclined guide wall surfaces for guiding the IC package onto the mounting portion. 
     Here, the contacts each may have a base portion embedded in the socket body, a first arm extending from the base portion and having a first contact at its tip, and a second arm extending from the base portion and having a second contact at its tip and a curved elastic portion at its intermediate portion. 
     The first contacts at the tips of the first arms may be secured to the socket body. 
     Two opposing sides of the opening may almost match with an envelope joining outer ends of the first contacts of the first arms of the contacts. 
     At least two opposing sides of the opening may almost match with an envelope joining tips of lead terminals extending from the IC package. 
     The inclined guide wall surfaces may be arranged symmetrical with respect to longitudinal and lateral center lines of the square opening and each may comprise a first inclined guide wall surface crossing each of the center lines, a second inclined guide wall surface provided at each corner portion and having an inclination angle larger than an inclination angle of the first inclined guide wall surface, and a third inclined guide wall surface connecting to the first and second inclined guide wall surfaces. 
     The contacts each may have a base portion embedded in the socket body, a first arm extending from the base portion and having a first contact at its tip, and a second arm extending from the base portion and having a second contact at its tip and a curved elastic portion at its intermediate portion. 
     The first contacts at the tips of the first arms may be secured to the socket body. 
     Two opposing sides of the opening may almost match with an envelope joining outer ends of the first contacts of the first arms of the contacts. 
     At least two opposing sides of the opening may almost match with an envelope joining tips of lead terminals extending from the IC package. 
    
    
     The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view showing one embodiment of an IC socket according to the present invention; 
     FIG. 2 is a cross section of the IC socket taken along the center line Xo of FIG. 1; 
     FIG. 3 is a cross section of a cover member of the IC socket according to the present invention taken along the center line Xo of FIG. 1; 
     FIG. 4 is an enlarged partial perspective view of the cover member of the IC socket according to the present invention; and 
     FIG. 5 is the same plan view as FIG. 1 of the IC socket according to the present invention, showing an example of how an IC package is guided. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Now, a preferred embodiment of the present invention will be described by referring to the accompanying drawings. 
     As shown in FIG. 1 to FIG. 4, an IC socket  10  according to one embodiment of this invention is a so-called open top type IC socket which generally has a socket body  100  and a cover member  200  mounted vertically movable on the socket body  100  to open and close contacts described later. 
     The socket body  100  includes a socket base  110  formed from an insulating substrate, square in plan view, in which a plurality of contacts  120  are arrayed along each of its four sides. A mount  130 , square in plan view, is positioned at a central portion of the socket base  110  and press-fitted to it. A positioning seat  140 , also square in plan view but slightly smaller than the mount  130 , is removably provided on the top of the mount  130 . The positioning seat  140  constitutes a mounting portion for supporting an IC package  300  mounted on the IC socket  10  and supports a resin body  310  of the IC package  300  with positioning projections  142  protruding from the positioning seat  140  at its four corners. More specifically, at each corner paired positioning projections  142  are arranged perpendicular to each other and engage perpendicularly intersecting corner inclined surfaces of the body  310  of the IC package  300  to support the IC package  300 . 
     The contacts  120  in this embodiment are of a so-called two-contact type having two contacts each. The contacts  120  are each formed of a conductive material and have a base portion  122  embedded in the socket base  110 , a first arm  124  and a second arm  126  extending from the base portion  122 , and an operation lever  128  connected to the second arm  126 , all integrally formed by punching. The first arm  124  integrally has a first contact  125  at its end and the second arm  126  integrally has a second contact  127  at its end. The second arm  126  has its intermediate portion formed into a curved elastic portion  129 . The first contacts  125  are arranged on an upper surface periphery of the mount  130  along the sides of the positioning seat  140 . 
     The socket base  110  has arranged outside the periphery of the mounting portion a large number of slits, which are the same in number and pitch as the contacts  120  and lead terminals  320  of the IC package  300 . The slits receive the first and second arms  124 ,  126  and guide the second arm  126  as it moves. 
     Next, the cover member  200  has an opening  210  square in plan view and facing the mounting portion and inclined guide wall surfaces  220  leading to the opening  210  and adapted to guide the IC package  300  onto the mounting portion. The opening  210  is so sized that two opposing sides of the opening  210  almost match with an envelope  321  joining tips of the lead terminals  320  extending from the two opposing sides of the IC package  300 . An example of envelope  321  is shown in FIG.  5 . In this embodiment, the lead terminals  320  extend from four sides of the IC package  300  and thus the lower edges of the four sides of the opening  210  almost match with envelope  321  joining the tips of the lead terminals  320 . For an IC package with its lead terminals extending from only two opposing sides, the size of the opening need only be set so that the lower edges of the corresponding two opposing sides of the opening almost match with the envelope  321  joining the tips of the lead terminals  320 . 
     Further, on the outer periphery of the positioning seat  140  that constitutes the mounting portion, a plurality of first contacts  125  as fixed contacts are arranged. The size of the opening is also set so that the lower edges of the two opposing sides of the opening  210  almost match with envelope  321  joining outer ends of the first contacts  125 . 
     The inclined guide wall surfaces  220  in the cover member  200  are arranged symmetrical with respect to the longitudinal and lateral center lines Xo and Yo of the square opening  210 . The inclined guide wall surfaces  220  traverse the center line Xo or Yo and each have a first inclined guide wall surface  222  inclined at an angle θ1 to a vertical surface containing a center line Zo perpendicular to the longitudinal and lateral center lines Xo and Yo and one of the longitudinal and lateral center lines Xo and Yo, a second inclined guide wall surface  224  provided at each corner portion and having an inclination angle θ2 larger than the inclination angle θ1 of the first inclined guide wall surface, and a third inclined guide wall surface  226  connecting to the first and second inclined guide wall surfaces  222  and  224 . Since the third inclined guide wall surface  226  connects to both of the first and second inclined guide wall surfaces  222  and  224  having different inclination angles, it forms a composite inclined surface which recedes from θ1 to θ2 in inclination angle with respect to the vertical surface with a predetermined escape angle β as the viewing point moves from the center line Xo or Yo toward each corner. 
     An underside of the cover member  200  is formed with inclined cam surfaces  230  that engage with the operation lever  128 . Guide claws  240  extend downward from the cover member  200 , as shown in FIG. 3, to allow the cover member  200  to be vertically movably mounted on the socket body  100 . 
     In the IC socket  10  of the embodiment above, when the cover member  200  is pressed against the socket body  100  from above by a robot arm not shown, the operation levers  128  engaging with the inclined cam surfaces  230  are moved against the spring force of the curved elastic portions  129  of the second arms  126 , parting the second contacts  127  of the second arms  126  from the first contacts  125  of the first arms  124 . In that state, when the IC package  300  that was held by suction with a robot arm or the like is released, the IC package  300  falls onto the IC socket  10 , as indicated by arrow of FIG.  2 . 
     When during the fall the IC package  300  is deviated to one side or inclined with respect to the center line Zo of the IC socket  10 , the tips of the lead terminals  320  of the IC package  300  first abut with and are guided by the first inclined guide wall surface  222  of the inclined guide wall surface  220  on that side toward which the IC package  300  is deviated. Then, the tips of the lead terminals  320  on the opposite side abut with and are guided by the first inclined guide wall surface  222  on the opposite side. As a result, the IC package  300  is supported on the positioning seat  140 , with the corner inclined surfaces of the IC package body  310  abutting against the positioning projections  142 . 
     The inclined guide wall surfaces  220  lead to the opening  210 , and each side of the opening  210  almost agrees with envelope  321  joining the tips of the lead terminals  320  extending from the IC package  300  to be mounted on the socket and also with envelope  321  joining the outer ends of the first contacts  125 . Hence, the IC package  300  that has been engaged and guided by the first inclined guide wall surfaces  222  is now supported on the positioning seat  140  with the corner inclined surfaces of its body  310  abutting against the positioning projections  142  and with the lead terminals  320  precisely positioned on the first contacts  125 . 
     When on the other hand the IC package  300  is about to be fitted onto the positioning seat  140  in a deviated and rotated state with respect to the center line Zo but with no inclination to the horizontal plane, as shown in FIG. 5, the tips of the lead terminals  320  of the IC package  300  at the corner portions abut with the third inclined guide wall surfaces  226  and are guided diagonally downward along the third inclined guide wall surfaces  226  toward the center line Zo, causing the IC package  300  to rotate in the horizontal plane. As a result, the IC package  300  is now guided by the first inclined guide wall surfaces  222  in a manner described above until it is supported on the positioning seat  140  with the corner inclined surfaces of the IC package body  310  abutting against the positioning projections  142  and with the lead terminals  320  precisely positioned on the first contacts  125 . 
     Then, when the robot arm is retracted upward to free the cover member  200  from the pressing force, the spring force of the curved elastic portions  129  of the second arms  126  pushes up the cover member  200  and at the same time causes the second contacts  127  of the second arms  126  to bear against, from above, the lead terminals  320  of the IC package  300  on the first contacts  125  of the first arms  124  thereby clamping the lead terminals  320  between the first contacts  125  and the second contacts  127 . 
     Although in the above embodiment the IC package is positioned by using the guiding action between the tips of the lead terminals extending from the four sides of the IC package and the inclined guide wall surfaces, it is needless to say that in the IC packages having the lead terminals on only two sides, the guiding action on the two sides having no lead terminals need only be produced by the engagement between the side surfaces of the IC package body and the inclined guide wall surfaces. 
     Further, while the two-contact type IC socket having the first and second contact arms have been described above, the present invention is also applicable to a so-called one-contact type IC socket having only one arm for each contact. 
     As can be seen from the above description, because in this invention the cover member has the square opening facing the mounting portion and the inclined guide wall surfaces leading to the opening and guiding the IC package onto the mounting portion, there are no inclined guide walls extending above the contacts, which in turn facilitates the assembly of the contacts into the socket body. Further, since there is no need to provide projecting guide posts at the corners of the socket body, it is possible to prevent deformations of the lead terminals that would otherwise be caused by a load bearing on only those lead terminals present at the corners of the IC package. Further, because there are no guide posts, the moving path of the robot is not limited, allowing the mounting of the IC package to be performed with ease and in a short time. 
     The present invention has been described in detail with respect to preferred embodiments, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and it is the intention, therefore, in the appended claims to cover all such changes and modifications as fall within the true spirit of the invention.