Abstract:
A zero insertion force integrated circuit socket for receiving an integrated circuit package includes a housing, a cover, and a lever. The housing has an array of contacts arranged in a matrix. The cover is slideably attached to the housing. The lever has a crankshaft extending substantially perpendicular to an actuation shaft. The lever is rotatable between a horizontal position and a vertical position to slide the cover over an upper surface of the housing. The cover has first and second locking arms. The second locking arm has an outer arm section that extends substantially parallel to the first locking arm. The lever is received between the first locking arm and the outer arm section to lock the lever in the vertical position.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention generally relates to zero insertion force (ZIF) integrated circuit (IC) sockets and, more particularly, to a ZIF IC socket having an actuation lever for attaching or detaching an IC package.  
       BACKGROUND OF THE INVENTION  
       [0002]     Integrated circuit (IC) sockets are traditionally used to electrically connect lead pins on an IC package to wiring on a circuit board. One type of IC socket, known as a zero insertion force (ZIF) socket, facilitates the attachment and detachment of the IC package to the wiring on the circuit board.  
         [0003]     One example, of a ZIF IC socket has a lever that is actuated between a vertical and a horizontal position to attach or detach the IC package. When attaching the IC package to the IC socket, the IC package is mounted on a mounting surface of the IC socket with the lever in the vertical position. In this position, the lead pins on the IC package are accommodated in a space adjacent to a gap between a pair of resilient arms of contacts arranged in a matrix below the mounting surface. The gap has a larger diameter than the lead pins. As the lever is pushed downward toward the horizontal position, the mounting surface slides and each of the lead pins is inserted into the gap between the resilient arms to establish an electrical connection between each of the lead pins and the contacts. The distance between the resilient arms is smaller than a diameter of the lead pins. Since the arms are resilient, however, the lead pins on the IC socket can be inserted into or removed from the gaps between the resilient arms when the mounting surface slides. In this example, the IC package can be attached to the IC socket simply by mounting the IC package on the mounting surface and pushing down the lever. As a result, although the packaging density of the IC package and the number of lead pins on the IC package is large, the IC package does not require a large insertion force to insert the lead pins between the respective resilient arms of the contacts that are spaced apart by a distance smaller than the diameter of the lead pins.  
         [0004]     When detaching the IC package from the IC socket, the lever is pulled upward from the horizontal position to the vertical position to remove the lead pins on the IC socket from the respective gaps between the resilient arms into the spaces described above, thus, breaking the electrical connection. During detachment of the IC package, the lead pins can be removed from the gaps between the respective resilient arms with only the force required to pull up the lever. The IC package can then be detached from the IC socket simply by lifting the IC package off the mounting surface with the lever being kept in the vertical position. A large pulling force is therefore not required to remove the lead pins from the gaps between the respective resilient arms.  
         [0005]     Because this type of ZIF IC socket breaks the electrical connection between the lead pins and the contacts when the lever changes from the horizontal position to the vertical position, accidental breaks of the electrical connection can occur. To prevent the accidental break of the electrical connection, Japanese Utility Model Laid-Open No. 2-86088 and Japanese Utility Model Laid-Open No. 2-86089 teach an IC socket having a retaining protrusion that holds the lever in the horizontal position once the IC package is attached thereto. In the IC sockets described in the above-identified patent references, the lever may be moved to the horizontal position when the IC package is to be mounted or when the IC package is to be detached. If the lever is moved to the horizontal position, however, before the IC package is completely mounted, the lead pins on the IC package are misaligned and have to be housed in spaces which are closer to the arms and narrower than the spaces described above. As a result, a larger insertion force is required to insert the lead pins into the narrower spaces. Additionally, if the lever is moved to the horizontal position when the IC package is being removed from the mounting surface, the lead pins have to be drawn from the narrower spaces, which also requires a larger pulling force. Thus, because the lever can be accidentally moved from the vertical position to the horizontal position, the advantage of the ZIF-type IC socket cannot be taken advantage of.  
       SUMMARY OF THE INVENTION  
       [0006]     It is therefore an object of the invention is to provide an IC socket that facilitates mounting an IC package to the IC socket with an activation lever that attaches and detaches the IC package from the IC socket wherein the lever is secured in both a horizontal and a vertical position.  
         [0007]     This and other objects are achieved by a zero insertion force integrated circuit socket for receiving an integrated circuit package including a housing, a cover, and a lever. The housing has an array of contacts arranged in a matrix. The cover is slideably attached to the housing. The lever has a crankshaft extending substantially perpendicular to an actuation shaft. The lever is rotatable between a horizontal position and a vertical position to slide the cover over an upper surface of the housing. The cover has first and second locking arms. The second locking arm has an outer arm section that extends substantially parallel to the first locking arm. The lever is received between the first locking arm and the outer arm section to lock the lever in the vertical position.  
         [0008]     This and other objects are further achieved by a zero insertion force integrated circuit socket for receiving an integrated circuit package including a housing, a cover, and a lever. The housing has an array of contacts arranged in a matrix. The cover is slideably attached to the housing. A lever has a crankshaft extending substantially perpendicular to an actuation shaft. The lever is rotatable between a horizontal position and a vertical position to slide the cover over an upper surface of the housing. The cover has a first locking arm that locks the lever in the vertical position. The first locking arm is double-supported and formed to lock the actuation shaft at an end section close to the crankshaft. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a plan view of an IC socket showing a lever of the IC socket in a horizontal position;  
         [0010]      FIG. 2  is a side view of the IC socket shown in  FIG. 1 ;  
         [0011]      FIG. 3  is a plan view of the IC socket showing the lever of the IC socket in a vertical position;  
         [0012]      FIG. 4  is a side view of the IC socket shown in  FIG. 3 ;  
         [0013]      FIG. 5  is a plan view of the lever of the IC socket;  
         [0014]      FIG. 6  is a left side view of the lever shown in  FIG. 5 ;  
         [0015]      FIG. 7  is a plan view of the IC socket of  FIG. 1  shown with a cover of the IC socket removed;  
         [0016]      FIG. 8  is a plan view of the IC socket of  FIG. 3  shown with the cover of the IC socket removed;  
         [0017]      FIG. 9  is a rear view of the cover shown from a side of a crank housing member; and  
         [0018]      FIG. 10  is a partial cross sectional view of the cover taken along the line A-A′ of  FIG. 9 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]      FIG. 1  shows a ZIF IC socket  1  according to an embodiment of the invention. The IC socket  1  has a housing  20 , a cover  30 , and a lever  10 . A substantially rectangular opening  301  extends through an approximate center of the cover  30  and the housing  20 . As shown in  FIGS. 7 and 8 , an upper surface  20   a  of the housing  20  has contact receiving cavities  21  arranged in a matrix. Each of the cavities  21  houses a contact  40 . Each of the contacts  40  has a base portion  41 . A pair of resilient arms  42  extend from ends of the base portion  41 . Between the base portion  41  and distal ends of the resilient arms  42  is a space  40   a  that is large enough to accommodate the diameter of a lead pin (not shown) on an IC package (not shown). The distance between the distal ends of the resilient arms  42  is smaller than the diameter of the lead pin (not shown). The lead pin (not shown) on the IC package (not shown) is first inserted into the space  40   a  and then moved toward the distal ends of the resilient arms  42 . In this position, the resiliency of the resilient arms  42  assure an electrical connection between the lead pin (not shown) and the contact  40 .  
         [0020]     As shown in  FIGS. 2 and 4 , soldering balls  21  are provided on a bottom surface of the housing  20  in a one-to-one relationship with the contacts  40 . The IC socket  1  is soldered to a surface of a circuit board (not shown) via the soldering balls  21 . The housing  10  may be already fixed to the circuit board (not shown) when attaching or detaching the IC package (not shown).  
         [0021]     As shown in  FIGS. 7 and 8 , retaining apertures  22  are formed on the housing  20  adjacent to the contacts  40 . The retaining apertures  22  are formed to engage with a pair of retaining arms  305  on the cover  30 , to be discussed later. A crank housing member  24  is formed adjacent to the retaining apertures  22 . The crank housing member  24  has a plurality of projections  23  with varying heights.  
         [0022]     As shown in  FIGS. 1 and 3 , the cover  30  extends over the upper surface  20   a  of the housing  20 . The cover  30  has a mounting surface  302  for mounting the IC package (not shown) surrounding the rectangular opening  301 . The mounting surface  302  includes a plurality of through-holes  3021  for receiving the lead pins (not shown) of the IC package (not shown). At a right side of the mounting surface  302  is a receiving member  31  and a retaining protrusion  32 . The receiving member  31  is disposed closer to a back side of the housing  20  than the retaining protrusion  32 . As shown in  FIGS. 2 and 4 , a cover crank housing member  303  is formed at a height higher than the mounting surface  302 . As shown in  FIGS. 1 and 2 , a front surface  303   a  of the cover housing member  303  has a pictorial illustration  3031  of the operation of the lever  10  and a positioning guide  3032  for correctly orienting the IC package (not shown).  
         [0023]     As shown in  FIG. 9 , a back surface of the cover housing member  303  has crank housing grooves  3034  recessed toward the front surface  303   a  of the cover  30 . The crank housing grooves  3034  are horizontally spaced apart from each other and have end walls  3034   a  and side walls  3034   b ,  3034   c , as best shown in  FIGS. 9 and 10 . Protrusions  3035  extend downward and away from the front surface  303   a  of the cover  30  close to the crank housing grooves  3034 . Two pairs of the retaining arms  305  extend from the cover housing member  303  toward the retaining apertures  22 . The retaining arms  305  are formed to retain the cover  30  on the housing  20  in a slidable manner.  
         [0024]     As shown in  FIGS. 1 and 3 , a first locking arm  33  and a second locking arm  34  are formed on a right side of the cover housing member  303 . The first locking arm  33  and the second locking arm  34  are provided in the same plane as the front surface  303   a.  The second locking arm  34  is substantially L-shaped when viewed from above and has an outer arm section  341  and a top arm section  38 . The outer arm section  341  extends parallel to the first locking arm  33  and faces, from an outside, the first locking arm  33 . The outer arm section  341  and the first locking arm  33  extend substantially parallel to an actuation shaft  11  of the lever  10  when the lever  10  is in a horizontal position, to be described later. As shown in  FIGS. 1 and 3 , a slit  3033  is formed in the cover housing member  303  parallel to the first locking arm  33  such that the first locking arm  33  has a double-supported beam structure. A second locking arm locking protrusion  3411  extends from the outer arm section  341 . On a side opposite of the slit  3033 , a first locking arm locking protrusion  331  extends toward the second locking arm locking protrusion  3411 . The second locking arm locking protrusion  3411  is positioned lower than the first locking arm locking protrusion  331 . The distance between a tip of the first locking arm locking protrusion  331  and a tip of the second locking arm locking protrusion  3411  is smaller than the diameter of an end section  113  of the lever  10 , to be described later.  
         [0025]     As best shown in  FIGS. 2 and 4 , a vertical arm  35  extends perpendicular to the plane of the surface  303   a.  One end of the second locking arm  34  is connected to the first locking arm  33  and the other end to the vertical arm  35 . The vertical arm  35  extends substantially parallel to the actuation shaft  11  of the lever  10  when the lever  10  is in the vertical position, to be described later. The vertical arm  35  is connected to the cover housing member  303  by a linking arm  36 , which is thinner than the first locking arm  33  and the second locking arm  34 . The linking arm  36  is disposed closer to the housing  20  than a surface of the receiving member  31 .  
         [0026]     The cover  30  may be formed, for example, by resin molding. Because the difference in thickness between the cover housing member  303  and the mounting surface  302  may shrink the mounting surface  302  during resin molding, which could result in misalignment of the through-holes  3021 , grooves  304  are formed in a row between the mounting surface  302  and the cover housing member  303  to reduce the difference in thickness.  
         [0027]     As shown in  FIG. 5 , the lever  10  is substantially L-shaped and includes the actuation shaft  11  and a crankshaft  12 . The actuation shaft  11  extends substantially perpendicular to the crankshaft  12  and has an angled section  111  for facilitating the securement of a distal end section  112 . The lever  10  has a rotation axis  10   r  that corresponds to a shaft center  12   c  of the crankshaft  12 . The crankshaft  12  has first sections  121  displaced from the shaft center  12   c  and longitudinally spaced apart from each other. Between the first sections  121  and flanking the first sections  121  are second sections  122 . The first sections  121  and the second sections  122  each have centers displaced by a slight angle from the shaft center  12   c.  As shown in  FIG. 8 , the first section  121  has steps  1211 . As shown in  FIG. 6 , the second sections  122  and the first sections  121  lie in a horizontal plane h. The first sections  121  protrude to the upper right. The actuation shaft  11  extends from the end section  113  to the step  111  in the direction of the protruding first sections  121 .  
         [0028]     An operator can use the distal end section  112  to rotate the lever  10 . When the lever  10  is rotated, the cover  30  slides over the housing  20 . As the actuation shaft  11  of the lever  10  is pulled upward from the horizontal position shown in  FIG. 1 , the cover  30  slides in the upward direction in  FIG. 1  to reach the state shown in  FIG. 3 . As the actuation shaft  11  of the lever  10  is pushed-downward from the vertical position shown in  FIG. 3 , the cover  30  slides in the downward direction in  FIG. 3  to reach the state shown in  FIG. 1 .  
         [0029]     As shown in  FIGS. 1 and 3 , the receiving member  31  and the retaining protrusion  32  retain the actuation shaft  11  in the horizontal position. The retaining protrusion  32  lies in the trajectory of the lever  10  and interferes with the actuation shaft  11  when the lever  10  is about to reach the horizontal position from the vertical position. In order for the lever  10  to reach the horizontal position, the actuation shaft  11  is pushed downward while the distal end section  112  is pulled outward to bend the actuation shaft  11  outward. This operation prevents interference between the actuation shaft  11  and the retaining protrusion  32  so that the actuation shaft  11  can be positioned below the retaining protrusion  32 . Once this operation is completed, the actuation shaft  11  is received by the receiving member  31 , which holds the lever  10  in the horizontal position shown in  FIG. 1 . The lever  10  is retained in the horizontal position and is prevented from rotating further, because the retaining protrusion  32  retains the lever  10  in the horizontal position from above to prevent it from being pulled upward, and the receiving member  31  retains the lever  10  from below to prevent it from being pushed further downward. The lever  10  can be rotated upward from the horizontal position to the vertical position by pulling the distal end section  112  of the actuation shaft  11  upward while pulling it outward, thereby releasing the actuation shaft  11  from the retaining protrusion  32 .  
         [0030]     As shown in  FIGS. 7 and 8 , the crankshaft  12  is rotatably housed between the cover housing member  303  of the cover  30  and the crank housing member  24  of the housing  20 . The lever  10  can rotate about a center of the crankshaft  12  to change its position between the vertical position shown in  FIG. 4  where the actuation shaft  11  stands substantially upright with respect to the surface of the circuit board (not shown) and the horizontal position shown in  FIG. 2  where the actuation shaft  11  is substantially parallel to the surface of the circuit board (not shown).  
         [0031]     As shown in  FIG. 1 , when the lever  10  is in the horizontal position, the end section  113  of the actuation shaft  11  close to the crankshaft  12  is located between the housing  20  and the vertical arm  35 . Therefore, when the lever  10  is in the horizontal position, the vertical arm  35  faces, from the outside, the housing  20  with the end section  113  of the lever  10  interposed therebetween. Thus, the vertical arm  35  prevents the crankshaft  12  from dropping from between the housing  20  and the cover  30  with reliability when the lever  10  is in the horizontal position. Furthermore, when the lever  10  is in the vertical position as shown in  FIG. 3 , the end section  113  of the actuation shaft  11  is located between the first locking arm  33  and the outer arm section  341 . Therefore, when the lever  10  is in the vertical position, the outer arm section  341  of the second locking arm  34  faces, from the outside, the first locking arm  33  with the end section  113  of the lever  10  interposed therebetween. Thus, the outer arm section  341  prevents the crankshaft  12  from dropping from between the housing  20  and the cover  30  with reliability when the lever  10  is in the vertical position.  
         [0032]     As shown in  FIG. 3 , in the vertical position, the end section  113  of the lever  10  is retained, from both sides, by the first locking arm locking protrusion  331  on the first locking arm  33  and the second locking arm locking protrusion  3411  on the outer arm section  341 . As the actuation shaft  11  of the lever  10  is pulled upward to rotate from the horizontal position to the vertical position, the end section  113  of the lever  10  comes into contact with the first locking arm locking protrusion  331  and the second locking arm locking protrusion  3411  when the lever  10  is about to reach the vertical position. As the actuation shaft  11  is rotated further, the end section  113  of the lever  10  temporarily widens the space between the tip of the first locking arm locking protrusion  331  and the tip of the second locking arm locking protrusion  3411 . At this time, the first locking arm  33  is bent inward toward the slit  3033  and the space between the first locking arm locking protrusion  331  and the second locking arm locking protrusion  3411  is widened to reduce friction between the first locking arm locking protrusion  331  and the second locking arm locking protrusion  3411  and the end section  113  of the lever  10 . The first locking arm locking protrusion  331  and the second locking arm locking protrusion  3411  are therefore formed to have a high durability. When the end section  113  of the lever  10  passes through the space between the first locking arm locking protrusion  331  and the second locking arm locking protrusion  3411 , the lever  10  reaches the vertical position shown in  FIG. 3 . As the end section  113  of the lever  10  passes through the space between the first locking arm locking protrusion  331  and the second locking arm locking protrusion  3411 , the operator feels a positive tactile response. Owing to the tactile response, the operator can tell when the lever  10  reaches the vertical position, which improves operability. In an alternate embodiment, either the first locking arm locking protrusion  331  or the second locking arm locking protrusion  3411  may be omitted.  
         [0033]     As shown in  FIG. 7 , when the lever  10  in the horizontal position, the first sections  121  protrude toward the contacts  40 . On the other hand, when the lever  10  is in the vertical position, as shown in  FIG. 8 , the first sections  121  protrude vertically with respect to a surface of the drawing and toward the crank housing  303  of the cover  30 . The housing grooves  3034  house the first sections  121  of the lever  10  in the vertical position, as shown in  FIG. 9 .  
         [0034]     The attachment and detachment of the IC package (not shown) to the IC socket  1  will now be described with reference to  FIG. 10 . In  FIG. 10 , the circle shown by the solid line represents a cross-section of the first section  121  of the lever  10  in the vertical position where about half of the crank section  121  is housed in the housing groove  3034 . The circle shown by the alternate long and short dashed lines represents a cross-section of the first section  121  of the lever in the horizontal position.  
         [0035]     To attach the IC package (not shown) to the IC socket  1  according to this embodiment, the lever  10  is first positioned in the vertical position, as shown in  FIGS. 3 and 8 . In the vertical position, the first sections  121  of the lever  10  are positioned between the crank housing grooves  3034  in the cover  30  and the crank housing member  24  in the housing  20 . The step  1211  of the first section  121  is positioned closer to the actuation shaft, as shown in  FIG. 8 , and is engaged with the end wall  3034   a  of the housing groove  3034 , which is closer to the vertical arm  35 , as shown in  FIG. 9 , to prevent the crankshaft  12  from falling off the cover  30 . Because the step  1211  is smoothly inclined and cannot solely prevent the crankshaft  12  from falling off, the outer arm section  341  further holds the crankshaft  12  in the cover  30 . The end section  113  of the lever  10  in the vertical position is retained, from the both sides, by the first locking arm locking protrusion  331  and the second locking arm locking protrusion  3411 , so that the lever  10  is held in the vertical position.  
         [0036]     The IC package (not shown) is mounted on the mounting surface  302  of the IC socket  1  according to the positioning guide  3032 . The lead pins (not shown) on the IC package (not shown) are inserted into the through-holes  3021  in the mounting surface  302  such that the lead pins (not shown) are received in the spaces  40   a  in the contacts  40 , as shown in  FIG. 8 . Since the spaces  40   a  are large enough to accommodate the diameter of the lead pins (not shown) on the IC package (not shown), the IC socket  1  according to this embodiment does not require a great insertion force to mount the IC package (not shown). The lever  10  is then pushed downward from the vertical position. As the end section  113  of the lever  10  passes through the space between the first locking arm locking protrusion  331  and the second locking arm locking protrusion  3411 , the operator feels a positive tactile response.  
         [0037]     As the lever  10  is pushed downward, the crankshaft  12  rotates about the shaft center  12   c  and the first sections  121  move from the position shown in  FIG. 8  to the position shown in  FIG. 7 . The rotation of the crankshaft  12  and the first sections  121  when the lever is pushed downward is indicated by arrow D in  FIG. 10 . During rotation, each of the first sections  121  press against the side wall  3034   b  of the housing groove  3034  closer to the mounting surface  302 . Pressed by the first sections  121 , the cover  30  slides in a direction indicated by arrow M in  FIG. 10 , so that the lead pins (not shown) inserted in the through-holes  3021  in the mounting surface  302  move toward the respective pairs of resilient arms  42  of the contacts  40 , as shown in  FIG. 8 . When the actuation shaft  11  reaches the retaining protrusion  32 , as best shown in  FIG. 3 , the actuation shaft  11  is bent outward to avoid the retaining protrusion  32  and pushed downward to position the actuation shaft  11  between the retaining protrusion  32  and the receiving part  31 . When the actuation shaft  11  is between the retaining protrusion  32  and the receiving part  31 , the lever  10  is in the horizontal position, and each of the lead pins (not shown) on the IC package (not shown) are resiliently held by the pair of resilient arms  42  of the contacts  40 , as shown in  FIG. 8 .  
         [0038]     When the lever  10  is in the horizontal position, the first sections  121  are located out of the crank housing grooves  3034 , as indicated by the alternate long and short dashed lines in  FIG. 10 . The step  1211  of the first section  121  in the state shown in  FIG. 7  is far from the actuation shaft  11  and is engaged with the protrusion  3035  shown in  FIG. 9 . The vertical arm  35  prevents the crank shaft  12  from falling off the cover  30 . The lever  10  is prevented from rotating from the horizontal position by the retaining protrusion  32  and by the receiving part  31 .  
         [0039]     To detach the IC package (not shown) from the IC socket  1  according to this embodiment, the lever  10  is pulled upward from the horizontal position to the vertical position. To change the position of the lever  10  from the horizontal position to the vertical position, the actuation shaft  11  can be pulled upward and bent outward to avoid the retaining protrusion  32 . As the lever  10  is pulled up, the crankshaft  12  rotates about the shaft center  12   c  and the first sections  121  move from the positions shown in  FIG. 7  to the position shown in  FIG. 8 . The rotation of the crankshaft  12  and the first sections  121  during movement of the lever  10  from the horizontal position to the vertical position is indicated by arrow U in  FIG. 10 . During rotation, each of the first sections  121  press against the side wall  3034   c  of the housing groove  3034  far from the mounting surface  302 . Pressed by the crank sections  121 , the cover  30  slides in a direction indicated by arrow R in  FIG. 10 , and the lead pins (not shown) held between the respective pairs of resilient arms  42  of the contacts  40  move toward the spaces  40   a , which are large enough to accommodate the diameter of the lead pins (not shown). When the lever  10  is about to reach the vertical position, the end section  113  of the lever  10  passes through the space between the first locking arm locking protrusion  331  and the second locking arm locking protrusion  3411 . As the end section  113  of the lever  10  passes through the space between the first locking arm locking protrusion  331  and the second locking arm locking protrusion  3411 , the operator feels a positive tactile response that indicates the lever  10  is in the vertical position. Since the first locking arm  33  has a double-supported-beam structure, the slit  3033  allows the first locking arm  33  to temporarily retract when the end section  113  is engaged with the first locking arm  33 . Therefore, the first locking arm  33  pressed by the end section  113  is bent toward the slit  3033  to reduce friction between the end section  113  and the first locking arm  33 , and the durability of the first locking arm  33  is improved. Once the lever  10  reaches the vertical position, the lead pins (not shown) are positioned in the spaces  40   a  which are large enough to accommodate the diameter of the lead pins (not shown). Since the end section  113  of the lever  10  is retained by the first locking arm locking protrusion  331  and the second locking arm locking protrusion  3411  in the vertical position, the IC package (not shown) can be lifted off the mounting surface  302 . Because the lead pins (not shown) on the IC package (not shown) are released from the pairs of resilient arms  42  of the contacts  40 , removing the IC package (not shown) from the mounting surface does not require a large pulling force.