Patent Publication Number: US-2010128442-A1

Title: Heat sink assembly

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a heat sink assembly, and more particularly to a heat sink assembly which effectively protects a computer chip socket. 
     2. Description of Related Art 
     With developments in microelectronics technology, electronic devices process data at unprecedented high speeds, producing large amounts of heat. To keep the systems stable and undamaged by the heat, the heat must be efficiently removed. Therefore, heat sinks are frequently used to dissipate heat from these electronic devices. 
     Conventionally, a heat sink is attached to an electronic device such as a central processing unit (CPU) by a clip. The clip is usually formed from steel. A commonly used heat sink clip assembly includes a clip having a pair of legs spaced apart at their first ends by a contiguous connecting member which is pressed against the heat sink. Because of environmental considerations, solder often used to solder the CPU socket is lead-free, although the lead-free solder is more frangible than that solder including lead. Upon receiving an external force, the lead-free solder on the CPU socket can be easily damaged. Further, the CPU socket under the heat sink receives considerable pressure from the clip pressing the heat sink, which may destabilize the CPU socket. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the embodiments can be better understood with references to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is an exploded, isometric view of a first embodiment of a heat sink assembly. 
         FIG. 2  is a sectional view of the heat sink assembly of  FIG. 1 . 
         FIG. 3  is an exploded, isometric view of a second embodiment of a heat sink assembly. 
         FIG. 4  is a sectional view of the heat sink assembly of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 and 2 , a heat sink assembly of a first embodiment comprises a PCB  20 , a socket  30  attached on the PCB  20 , a chip  40  received in the socket  30 , and a heat sink  10  contacting a top surface of the chip  40 . 
     The heat sink  10  comprises a base  11 , a plurality of fins  12  extending up from the base  11 , and four legs  110  extending down from four corners of the base  11 . Each leg  110  is laddered, including a supporting portion  111  with a large cross section, and a received portion  112  with a small cross section, which extends down from the supporting portion  111 . The PCB  20  defines four holes  21  corresponding to the four legs  110  of the heat sink  10 . A cross section of each of the holes  21  is larger than that of the received portion  112  but smaller than that of the supporting portion  111  to stop the supporting portion  111  from passing through the holes  21 . The socket  30  is attached on the PCB  20  among the four holes  21 , with the four legs  31  extending down from four corners of the socket  30 . An upright length of the supporting portion  112  exceeds a thickness of the socket  30 . A layer of solder  50  is disposed between the socket  30  and the PCB  20 . The chip  40  is received in the socket  30  being slightly taller than the socket  30 . A layer of a heat-conduction medium (not labeled) is disposed on a top surface of the chip  40 . 
     In assembly of the heat sink  10  onto the PCB  20 , the received portions  112  of the heat sink  10  are received in the holes  21  of the PCB  20  respectively until the supporting portions  111  resist the top surface of the PCB  20 , and the heat sink  10  compresses the layer of heat-conduction medium. Because the supporting portions  111  contact the PCB  20 , pressure from the heat sink  10  is distributed between the chip  40  and the PCB  20 . The chip  40  is protected from damage. The parts of the received portions  112  that pass through the holes  21  may be fastened to the bottom surface of the PCB  20 , by soldering, gluing, or other means. The legs  31  contact the PCB  20 , and between the solder layer  50  and the legs  31 , pressure from the socket  30  and the chip  40  is further distributed. The solder layer  50  is protected from damage, and the socket  30  stably meets the PCB  20 . 
     Referring to  FIGS. 3 and 4 , a heat sink  10 ′ in a second embodiment provides heat dissipation of a chip  40 ′ received in a socket  30 ′ attached on a PCB  20 ′. In this embodiment, a heat sink clip  50 ′ fastens the heat sink  10 ′ on the PCB  20 ′. 
     The heat sink  10 ′ comprises a base  11 ′, a plurality of fins  12 ′ extending up from the base  11 ′, and four legs  110 ′ extending down from the base  11 ′. The upright length of the leg  110 ′ exceeds that of the socket  30 ′. The socket  30 ′ is attached on the PCB  20 ′, four legs  31 ′ extend down from four corners of the socket  30 ′. A layer of solder  60 ′ is disposed between the socket  30 ′ and the PCB  20 ′. The chip  40 ′ is received in the socket  30 ′ and is positioned slightly higher than the socket  30 ′. A layer of heat-conduction medium (not labeled) is disposed on a top surface of the chip  40 ′. The heat sink clip  50 ′ defines two latching members  51 ′ at the end of the heat sink clip  50 ′. The PCB  20 ′ defines two latching elements  21 ′ corresponding to the latching members  51 ′. 
     In assembling the heat sink  10 ′ onto the PCB  20 ′, the heat sink  10 ′ is laid on the PCB  20 ′, compressing the layer of heat-conduction medium. Distal ends of the legs  110 ′ away from the base  11 ′ contact the top surface of the PCB  20 ′. Because the legs  110 ′ contact the PCB  20 ′, pressure from the heat sink  10 ′ is distributed between the chip  40 ′ and the PCB  20 ′, and chip  40 ′ is protected from damage. The legs  31 ′ contact the PCB  20 ′, between the solder layer  60 ′ and which pressure from the socket  30 ′ and the chip  40 ′ is further distributed. The solder layer  60 ′ is protected from damage, and the socket  30 ′ stably meets the PCB  20 ′. Heat sink clip  50 ′ is mounted on the base  11 ′ of the heat sink  10 ′ and the latching members  51 ′ clasp the latching elements  21 ′ of the PCB  20 ′. Thus, the heat sink  10 ′ is fastened on the PCB  20 ′, as shown in  FIG. 4 . 
     It is to be understood, however, that even though numerous characteristics and advantages of the embodiments have been set forth in the foregoing description, together with details of the structure and function of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.