Abstract:
A heat sink assembly for a circuit board component is provided. that includes a heat sink base, a frame coupled to the base, and a cam positionable relative to the base to lock the heat base to the circuit board component. The frame includes an actuator that has a first post and a second post. Each post has an upper end, a lower end, and a shaft portion therebetween. The lower end includes a retention lug. A cross beam interconnects the shaft portions of the posts. The frame further includes a board lock and the cam includes a lever coupled to the cam. The cam engages the actuator to move the actuator relative to the frame from a first position to a second position to lock the heat sink base to the circuit board component. The heat sink remains in the locked position when the lever is rotated from the second position to the first position.

Description:
BACKGROUND OF THE INVENTION 
   The invention relates generally to heat sinks for electronic devices, and more specifically, to mounting and retention systems for heat sinks. 
   The use of heat sinks on electronic components is well known. Typically, a heat sink is arranged in close contact with a heat generating electronic component, such as a Central Processing Unit (CPU). As the power density of such components increases, heat transfer from the heat generating component to the surrounding environment becomes more and more critical to the proper operation of the component. Heat generated by the component is transferred to the heat sink and then dissipated from the heat sink to the surrounding air. One type of heat sink includes a metallic core in the form of a base plate. Heat dissipating fins extend from the base plate to increase the surface area of the heat sink. Heat transferred from the component to the base plate is spread throughout the base plate and to the fins fixed to the base plate. To further facilitate the dissipation of heat from the electronic component, a fan can be used to circulate air about outer surfaces of the fins and the base of the heat sink. 
   In the case of a CPU, current circuit board designs typically provide for the heat sink to be mounted directly on top of the CPU in a retention module that is in turn mounted on the circuit board. A spring clip or other fastening mechanism is used to retain the heat sink in the retention module. Thus, the installation of the heat sink is a multi-step process that involves multiple components with both assembly time and component costs adding to the cost of the product. 
   BRIEF DESCRIPTION OF THE INVENTION 
   In one embodiment of the invention, a heat sink assembly for a circuit board component is provided. The assembly includes a heat sink base, a frame coupled to the base, and a cam positionable relative to the base to lock the heat sink base to the circuit board component. 
   Optionally, the frame includes an actuator that has a first post and a second post. Each post has an upper end, a lower end, and a shaft portion therebetween. The lower end includes a retention lug. A cross beam interconnects the shaft portions of the posts. The frame further includes a board lock and the cam includes a lever coupled to the cam. The cam engages the actuator to move the actuator relative to the frame from a first position to a second position to lock the heat sink base to the circuit board component. The heat sink remains in the locked position when the lever is rotated from the second position to the first position. 
   In another embodiment, a heat sink assembly for a circuit board component is provided that includes a heat sink base, an actuator coupled to the base, and a board lock for coupling the base to the circuit board in heat transfer relationship to the circuit board component. The board lock includes a pair of retention barbs, and the actuator is configured to spread the pair of retention barbs and apply a normal force to a surface of the circuit board component when the actuator is moved from a first position to a second position. 
   In another embodiment, a heat sink retention assembly is provided that includes a heat sink base and a frame. The frame includes a board lock that is configured to be received in a circuit board. An actuator is received in the flame and is movable with respect to the frame from an open position to a locked position wherein the board lock is activated to retain the retention assembly on the circuit board. A cam is disposed between the frame and the actuator. The cam is rotatable from a first position to a second position to move the actuator between the open position and the locked position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a heat sink integrated retention system in accordance with an exemplary embodiment of the present invention. 
       FIG. 2  is a perspective view of a frame assembly used in the system of FIG.  1 . 
       FIG. 3  is a perspective view of the frame member of FIG.  2 . 
       FIG. 4  is a perspective view of the actuator of FIG.  2 . 
       FIG. 5  is a perspective view of a cam lever in accordance with an exemplary embodiment of the present invention. 
       FIG. 6  is a partial front elevational view of the cam lever of  FIG. 5  taken along sight line  6 — 6 . 
       FIG. 7  is a perspective view of the heat sink assembly of FIG.  1 . 
       FIG. 8  is a schematic view of an assembled heat sink integrated retention system in an unlocked state. 
       FIG. 9  is a schematic view of the heat sink integrated retention system of  FIG. 8  in a locked state. 
       FIG. 10  is a perspective view of an alternative embodiment of a heat sink integrated retention system in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  illustrates a perspective view of an integrated retention system  10  for a heat sink assembly in accordance with an exemplary embodiment of the present invention. The integrated retention system  10  includes a heat sink assembly  20 , a fan  22 , and a housing  24 . The heat sink assembly  20  includes a heat sink base  26  with a plurality of cooling fins  28  extending upwardly from the base  26 . The heat sink base  26  and the fins  28  are typically fabricated from metal such as aluminum or copper, and further, the heat sink base  26  and the fins  28  may be fabricated from the same or different metals. For instance, in one embodiment the heat sink base  26  may be made of copper while the fins  28  may be made of aluminum. 
   The fan  22  is mounted above the cooling fins  28  for circulating air about the cooling fins  28  and the heat sink base  26  to facilitate the transfer of heat from a heat generating component (not shown). When in use, the heat sink base  26  is positioned in contact with the heat generating component such that heat generated by the component is transferred to the heat sink base  26  and the cooling fins  28  and then to the surrounding air. 
   The housing  24  holds and mounts the heat sink assembly  20  and the fan  22  to a circuit board  30  so that the heat sink base  26  is in contact with the heat generating component, and applies a compressive load to produce a normal contact force between the heat sink base  26  and the heat generating component. The housing  24  includes a pair of frame assemblies  34  and a cam lever  36 . 
     FIG. 2  illustrates one of the frame assemblies  34  which are identical to each other. The frame assembly  34  includes a frame member  40  and an actuator  42 . The frame member  40  includes a pair of legs  44  that each include a channel  46  that receives the actuator  42 . The actuator  42  is slidable within the channel  46  between an upper stop  48  and a lower stop  50  on each leg  44 . The frame member  40  and the actuator  42  are fabricated from a resilient material that exhibits some degree of flexibility. In one embodiment, the material is nylon 66™. 
     FIG. 3  illustrates the frame member  40  in detail. The frame member  40  includes upper and lower cross members  54  and  56  respectively. Cross members  54  and  56  are substantially parallel to each other and interconnect the legs  44 . Each leg  44  includes a slot  60  at an upper end  64  which extends downward to a ledge  68 . The ledges  68  at each of the four legs  44  cooperate to define a platform for the fan  22  (shown in FIG.  1 ). The upper end  64  of each leg  44  includes a pair of tabs  70  that retain the fan  22  when the integrated system  10  is assembled. The legs  44  each include a cut out  72  that defines the upper and lower actuator stops  48  and  50  respectively. Each leg  44  includes an attachment end  74  for connecting the frame member to the circuit board  30 . Each attachment end  74  includes a board lock  78  for attachment to a mounting hole (not shown) on the circuit board  30 . The board lock  78  comprises a pair of retention barbs  79  positioned one on each side of the channel  46  extending through the leg  44  such that the retention barbs  79  are separable relative to each other. The retention barbs  79  include a retaining groove  80  on an outer surface thereof and a recess  82  within the channel  46  on an inner surface  83  of the retention barbs  79 . The retaining groove  80  and the recess  82  cooperate to lock the legs  44  to the circuit board  30  as will be described below. 
     FIG. 4  is a perspective view illustrating the actuator  42  in detail. In one embodiment, the actuator  42  is in the shape of an H beam and includes a pair of posts  84  that are interconnected by a substantially horizontal cross beam  86 . The posts  84  are slidably received in the channels  46  (shown in  FIG. 3 ) of the legs  44 . The cross beam  86  is received in the cut out  72  (shown in  FIG. 2 ) in the legs  44 . The upper and lower stops  48  and  50  (shown in  FIG. 3 ) in the cutout  72  interfere with the cross beam  86  to define a range of movement of the actuator  42  within the legs  44 . The posts  84  have an upper end  88  and a lower end  90 . The lower end  90  of each post  84  includes a serrated retention lug  92  that spreads the attachment ends  74  (shown in  FIG. 3 ) of the legs  44  when the actuator posts  84  are drawn upward through the channel  46 . The retaining groove  80  (shown in  FIG. 3 ) on the board locks  78  are sized to receive a thickness of the circuit board  30  (shown in  FIG. 1 ) to lock the legs  44  onto the circuit board  30  when the board lock retention barbs  79  on the attachment ends  74  of the legs  44  are separated. The retention lugs  92  are configured to be retained in the pockets  82  in the retention barbs  79  to hold the board locks  78  in a separated position. Once the board locks  78  are in the locked position, manual thumb pressure is required to be applied to the upper ends  88  of the posts  84  to drive the retention lugs  92  from the pockets  82  to release the integrated retention system  10  from the circuit board  30 . 
     FIG. 5  illustrates a perspective view of the cam lever  36 .  FIG. 6  illustrates a frontal view of the cam lever  36 . The cam lever  36  includes a handle  100  and a pair of lever arms  102 . A cam  104  is provided at the end of each lever arm  102 . Each cam  104  has an outer periphery  105  that includes an open flat section  106  positioned between smaller raised locking flat sections  108 . A disc  110  is also provided adjacent to cams  104  to provide a bearing surface  112  for rotating the cam lever  36 . A short pivot shaft  114  displaces the cam  104  from the disk  110 . 
   When installed in the integrated system  10 , the cams  104  are positioned to engage the cross beam  86  of the actuator  42 . The cam lever  36  is rotatable from a released position to a locked position. In the released position, the open flat section  106  of the cam  104  faces upward and is adjacent to cross beam  86  of the actuator  42 . In the locked position, one of the raised locking flat sections  108  engages the cross beam  86  to operate the actuator  42 . The locking flat section  108  provide a detent position so that the cam lever  36  will remain in the locked position once rotated to the locked position. 
     FIG. 7  is a perspective view of the heat sink assembly  20 . The heat sink assembly  20  includes cam guides  122  formed in fins  127  and  128  and channels  124  formed between fins  128  and  129 . The cam guides  122  are sized to receive the cam lever pivot shaft  114 . The channels  124  are provided to receive the cams  104 . The heat sink base also includes clearance notches  126  that receive the frame legs  44  when the integrated system  10  is assembled. 
   In assembling the integrated system  10 , the upper ends  88  of the actuator posts  84  (shown in  FIG. 4 ) are inserted through the mounting holes  23  (see  FIG. 1 ) in the fan  22 . The actuator  42  is then joined with the frame member  40  by inserting the posts  84  of the actuator  42  into the channels  46  of the legs  44  so that the cross beam  86  is positioned within the cutout  72  in the legs  44  and with the lower end  90  of the actuator posts  84  extended from the board locks  78 . 
   The cam lever  36  is placed over the frame assemblies  34  such that the upper cross members  54  is positioned between the lever arms  102  while the cam  104  is positioned between the lower cross members  56 . The cam lever  36  is then rotated to a position where the open flat section  106  is facing upward. Finally, the fan  22  is held in place between the ledges  68  and the tabs  70  on the legs  44  while the frame assemblies  34  are placed onto the heat sink assembly  20  with the cams  104  and the actuator cross beams  86  received in the heat sink channels  124 . The integrated system  10  can now be mounted on the circuit board  30  and locked into place by rotation of the cam lever  36 . 
     FIGS. 8 and 9  are schematic views of an assembled integrated retention system  10  illustrating the operation of the cam  104  and actuator  42  in mounting the integrated system  10  for cooling a heat generating component  140 . In  FIG. 8 , the cam  104  is positioned in the heat sink channel  124 . The actuator cross beam  86  is engaged with the cam  104  at the open flat section  106 . The integrated system  10  is positioned on the circuit board  30  with the heat sink base  26  in contact with the heat generating component  140 . The upper ends  88  of the actuator posts  84  are depressed such that the board lock retention barbs  79  are not separated and pass unrestricted through the circuit board mounting holes  130 . In this condition, the integrated retention system  10  is not locked on the circuit board  30 . From this position, rotation of the cam lever  36  in the direction of arrow A drives the actuator  42  upward which causes the retention barbs  79  to separate to engage and retain the circuit board  30  in the retaining groove  80  (shown in  FIG. 3 ) to lock the system  10  to the circuit board  30 . 
   In  FIG. 9 , the cam lever  36  has been rotated in the direction of arrow A to lock the integrated retention system  10  to the circuit board  30 . When the cam lever  36  is rotated, the locking flat section  108  on the cam  104  engages the actuator cross beam  86  driving the actuator posts  84  upward. The upward movement of the actuator posts  84  brings the retention lugs  92  (shown in  FIG. 4 ) into engagement with the attachment ends  74 , and the retention barbs  79  of board locks  78  (shown in FIG.  3 ). The retention lugs  92  separate the retention barbs  79  into the circuit board mounting holes  130  such that the retention groove  80  (shown in  FIG. 3 ) retains the circuit board  30  locking the integrated system  10  to the circuit board  30 . The lugs  92  are received in the pockets  82  (shown in  FIG. 3 ) of the retention barbs  79  so that the integrated system  10  remains locked onto the circuit board  30  even if the cam lever  36  is rotated in the direction of arrow B to release the actuator  42 . When it is desired to unlock the integrated system  10 , physical thumb pressure is applied to the upper ends  88  of the actuator posts  84  to drive the actuator posts  84  downward, disengaging the lugs  92  from the pockets  82  of the retention barbs  79 . The retention barbs  79  then return to their unseparated position allowing removal of the integrated system  10  from the circuit board  30 . 
   As shown in  FIG. 9 , when the cam lever  36  is rotated in the direction of arrow A to lock the integrated system  10  to the circuit board  30 , the actuator cross beam  86  is elastically deflected in an upward direction by the cam  104 . The combined rotation of the cam lever  36  and the deflection of the cross beam  86  generate a downward compressive force resulting in a normal contact force between the heat sink base  26  and a heat generating component  140 . 
     FIG. 10  illustrates an integrated heat sink and retention system  150 . The integrated heat sink and retention system  150  is similar to the integrated system  10  and corresponding elements between the integrated systems  150  and  10  are given the same reference numbers in FIG.  10 . In the integrated system  150 , the heat sink base  26  is without fins. The integrated system  150  includes the heat sink base  26 , a fan  22  and a housing  24 . The system is mounted to the circuit board  30 . The cam lever  36  drives from the heat sink base  26  to rotate cams  104 . The cams  104  engage the cross beams  86  to operate the actuator  42  within the frame members  40  to lock the integrated system  150  to the circuit board  30  as previously described. The cams  104  engage the actuator cross beam  86  which elastically deforms to generate a downward compressive force from the heat sink base  26  the heat generating component (not shown in FIG.  10 ). 
   The embodiments thus described provide a heat sink and housing integrated into a single unit. The integrated system provides a cost effective alternative to attachment mechanisms requiring clips and other hardware. Having no hardware requirement, use of the integrated retention system also reduces product assembly time. 
   While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.