Heat sink assembly and connecting device

Abstract

A heat sink assembly includes a heat sink with a base plate having a top surface with fins for dissipating heat and an opposed bottom surface for placing against an electronic device mounted on a printed circuit board, and at least one connecting device for loading the heat sink against the electronic device. The connector includes a mechanical fastener such as a push pin having an end which engages the circuit board, a compression spring received against a shoulder on the fastener, and a cup member which is installed in an aperture in the base plate so that a floor of the cup member provides a bearing surface for the spring which is below the bottom surface of the base plate. An alternative connector utilizes a conical spring received through the base plate and receiving the fastener therein to load the spring in tension against the electronic device.

1 . A heat sink assembly for connecting to an electronic device mounted on a printed circuit board, said assembly comprising: 
 a heat sink comprising a base plate having a top surface and an opposed bottom surface for placing against an electronic device;    a bearing surface which is fixed with respect to said heat sink;    a mechanical fastener having a first end, a second end for fixing said fastener to a printed circuit board, a shank extending between said first end and said second end, and a shoulder on said shank, said shoulder facing said second end; and    a spring having a first portion received against said bearing surface and a second portion received against said shoulder, one of said first and second portions being located below said bottom surface of said base plate, said spring loading said heat sink toward said printed circuit board when said second end of said fastener is fixed to the printed circuit board.    
   
   
       2 . The assembly of  claim 1  wherein said bearing surface is located below said bottom surface of said base plate, said spring being a compression spring which loads the first end of the fastener away from said bearing surface.  
   
   
       3 . The assembly of  claim 2  wherein said spring is a coil spring through which said shank passes, said coil spring having a first end forming said first portion and a second end forming said second portion.  
   
   
       4 . The assembly of  claim 3  further comprising a cup member having a lip, a floor, and a wall extending between said lip and said floor, said lip being positively positioned with respect to said base plate, said floor forming said bearing surface and having a central aperture through which said shank passes.  
   
   
       5 . The assembly of  claim 4  wherein said wall is substantially cylindrical.  
   
   
       6 . The assembly of  claim 4  wherein said lip is formed by a flange extending radially outward from said wall, said flange being received against said top surface of said heat sink base plate, said base plate having an aperture through which said wall passes.  
   
   
       7 . The assembly of  claim 4  wherein said base plate comprises a recess in said bottom surface, said lip being fixed in said recess.  
   
   
       8 . The assembly of  claim 7  wherein said lip is fixed in said recess by one of a press fit, threads, brazing, solder, and glue.  
   
   
       9 . The assembly of  claim 7  wherein said recess is countersunk around an opening in said base plate, said head of said fastener being received in said opening.  
   
   
       10 . The assembly of  claim 9  wherein said head of said fastener does not extend above said top surface of said base plate, said opening being constricyed to prevent passage of said head.  
   
   
       11 . The assembly of  claim 4  further comprising a retainer fitted to said shank below said cup member, said retainer preventing withdrawing of said fastener from said cup member prior to fixing said second end of said fastener to said printed circuit board.  
   
   
       12 . The assembly of  claim 1  wherein said fastener is formed with a head at said first end, said head forming said shoulder.  
   
   
       13 . The assembly of  claim 1  wherein said bearing surface is located at said top surface of said base plate, said spring being a tension spring which loads said shoulder toward said bearing surface.  
   
   
       14 . The assembly of  claim 13  wherein said spring is a coil spring having a coil which forms said bearing surface.  
   
   
       15 . The assembly of  claim 14  wherein said coil spring is a substantially conical spring.  
   
   
       16 . A device for connecting a heat sink to an electronic device mounted on a printed circuit board, said device comprising: 
 a mechanical fastener having a first end, a second end for fixing said fastener to a printed circuit board, a shank extending between said first end and said second end, and a shoulder on said shank, said shoulder facing said second end;    a cup member having a lip, a floor, and a wall extending between said lip and said floor, said floor forming a bearing surface and having a central aperture through which said shank passes; and    a compression spring having a first portion received against said bearing surface and a second portion received against said shoulder, said spring loading said shoulder away from said bearing surface.    
   
   
       17 . The device of  claim 16  wherein said compression spring is a coil spring having a first end forming said first portion and a second end forming said second portion, said shank being received through said coil spring.  
   
   
       18 . The device of  claim 16  wherein said lip is formed by a flange extending radially outward from said wall.  
   
   
       19 . The device of  claim 16  further comprising a retainer fitted to said shank below said cup member, said retainer preventing withdrawing of said fastener from said cup member prior to fixing said second end of said fastener to said printed circuit board.  
   
   
       20 . The device of  claim 16  wherein said fastener is formed with a head at said first end, said head forming said shoulder.