Cam-type retainer clip for heat sinks for electronic integrated circuits

Abstract

A heat sink assembly comprises a heat sink and a retainer clip for attachment to an electronic package or semiconductor device so as to dissipate heat from such device. The heat sink may comprise a flat base with a plurality of upwardly extending fins. The fins will define at least one channel. The retainer clip includes two parts. One part is an elongated, resilient, metal strap that has holding means at each end for engaging a semiconductor socket, or a semiconductor module, so as to secure the retainer clip and heat sink to the device or module. The retainer clip also includes a cam-type latch which is pivotally positioned in the middle of the elongated strap and includes an arm and a cam. The cam has a bearing surface which is spaced from the axis of the elongated member a distance greater than the distance between the elongated member and the upper surface of the heat sink base when in the initially assembled position. When the arm is rotated, the bearing surface of the cam is forced against the upper surface of the heat sink which causes the strap to be displaced upwardly placing pressure on the strap and thereby forcing the heat sink into heat conducting engagement with the electronic device or module.

What is claimed is:  
     
       1. In a heat sink assembly providing cooling to an electronic semiconductor device wherein the device is mounted in a module, the module having means for engagement with a retainer clip, and the heat sink having a generally flat bottom surface and heat conducting engagement with the semiconductor device upper surface and a plurality of fins on the upper surface defining at least one channel, the improvement comprising a heat sink retainer clip including: 
       an elongated, resilient metal strap received in one of the channels of the heat sink having holding means at each end engaging the engagement means on the module, the center portion of the strap spaced a pre-determined distance above the upper surface of the heat sink base when the strap is not in tension; and  
       a cam-type latch pivotally mounted in the center portion of the strap and including a cam with a bearing surface, the distance from the pivot access to the bearing surface of the cam being greater than the distance between the pivot access and the upper surface of the base of the heat sink when said strap is not in tension, and an arm fixedly mounted to said cam, said arm, when rotated, causing said bearing surface of said cam to be forced against the surface of the base of the heat sink placing the strap in tension so as to force the heat sink into heat conducting engagement with the module.  
     
     
       2. The improved retainer clip set forth in  claim 1  when said cam-type latch comprises a single piece of metal stamped to form a channel. 
     
     
       3. The improved retainer clip of  claim 2  wherein said latch arm includes means for retaining the arm in engagement with the strap so that tension is applied to the strap. 
     
     
       4. The improved retainer clip of  claim 3  wherein said strap is provided in the center portion with stub axles projecting laterally outward, said cam-type latch having an opening in each wall of the channel midway between the arm and cam and receiving the stub axles so as to pivotally mount the latch on the elongated strap. 
     
     
       5. A heat sink assembly including a heat sink and a spring retainer clip providing cooling to an electronic integrated circuit device, the device being mounted in a housing, such as a socket or a module, the housing having engagement means for the spring retainer clip, said heat sink assembly comprising: 
       a heat sink including a metallic plate with a plurality of fins projecting upwardly from the  
       top surface of the plate defining a series of channels; and  
       such spring retainer clip comprising two members:  
       an elongated, resilient metal strap received in one of said channels and holding means at each end of said strap engaging the engagement means on the housing, said strap having a length such that when it is in engagement with the housing, the center portion of the strap is spaced a pre-determined distance above the upper surface of the heat sink base when the strap is not in tension; and  
       a cam-type latch pivotally mounted in the center portion of the strap and including a cam with a bearing surface, the distance from the pivot access to the bearing surface being greater than the distance between the pivot access and the upper surface of the base of the heat sink when said strap is not in tension, and an arm fixedly mounted to said cam, said arm when rotated causing said cam to bear against the surface of the base of the heat sink placing the strap in tension so as to force the heat sink into heat conducting engagement with the housing.  
     
     
       6. The heat sink assembly of  claim 5  wherein when said arm is rotated, placing the strap in tension, the inner surfaces of the strap adjacent the edge of the housing traps said heat sink to prevent inadvertent lateral movement. 
     
     
       7. A combination heat sink and heat sink retainer clip, for attachment to a rectangular electronic module wherein the rectangular electronic module contains a printed circuit board and at least one semiconductor device, has at least one major wall which is substantially flat and made of a heat conducting material such as metal, and includes at least two spaced apart openings each adjacent one of the longer edges of the wall, 
       said heat sink having a rectangular base substantially the same size as the electronic module major wall and a plurality of cooling fins defining at least one channel, said at least one channel aligned transversely between the at least two spaced apart openings in the electronic module wall; and  
       said retainer clip comprising:  
       an elongated, resilient, metal strap received in said at least one channel and holding means at each end engaging one of the openings in the module wall, said strap having a length such that with each end in engagement with one of the module wall openings, the center portion of the strap is spaced a predetermined distance above the upper surface of the heat sink base when the strap is not in tension; and  
       a cam-type latch is pivotally mounted in the center portion of the strap and including a cam with a bearing surface, the distance from the pivot axis to the cam bearing surface being greater than the distance between the pivot axis and the upper surface of the base of the heat sink when said strap is not in tension, and an arm fixedly mounted to said cam, said arm when rotated causing said cam to bear against the surface of the base of the heat sink and placing the strap in tension so as to force the heat sink into heat conducting engagement with the module wall.  
     
     
       8. The assembly of  claim 1  wherein said strap holding means comprises hook-shaped portions at each free end of the strap, the hook-shaped portions being received in the module wall openings to engage the lower surface of the module wall adjacent the opening when the strap is placed in tension. 
     
     
       9. The heat sink assembly of  claim 1  wherein said strap is of generally rectangular configuration and is formed by stamping. 
     
     
       10. The heat sink assembly of  claim 1  wherein said cam-type latch comprises a single piece of metal formed into a channel, said center portion of the strap is provided with transversely projecting tabs defining a pivot axle, the latch having openings receiving the tab axles, said cam-type latch being formed by a stamping operation. 
     
     
       11. The heat sink assembly of  claim 10  wherein the arm of said cam-type latch includes detent means for retaining the latch arm in the fully engaged position to prevent inadvertent pivoting of the arm into a relaxed position. 
     
     
       12. In a heat sink assembly providing cooling to an electronic semiconductor device wherein the device is mounted in a module, the module having means for engagement with a retainer clip, and the heat sink having a generally flat bottom surface and heat conducting engagement with the semiconductor device upper surface and a plurality of fins on the upper surface defining at least one channel, the improvement comprising a heat sink retainer clip including: 
         an elongated, resilient strap received in one of the channels of the heat sink having holding means at each end for engaging the engagement means on the module, the center portion of the strap space a pre - determined distance above the upper surface of the heat sink base when the strap is not in tension; and    
         a cam - type latch pivotally mounted in the center portion of the strap and including a cam with a bearing surface, the distance from the pivot access to the bearing surface of the cam being greater than the distance between the pivot access and the upper surface of the base of the heat sink when said strap is not in tension, and an arm fixedly mounted to said cam, said arm, when rotated, causing said bearing surface of said cam to be forced against the surface of the base of the heat sink placing the strap in tension so as to force the heat sink into heat conducting engagement with the module.    
     
     
       13. The improved retainer clip set forth in  claim 12  when said cam- type latch comprises a single piece of metal stamped to form a channel.    
     
     
       14. The improved retainer clip of  claim 13  wherein said latch arm includes means for retaining the arm in engagement with the strap so that tension is applied to the strap.  
     
     
       15. The improved retainer clip of  claim 14  wherein said strap is provided in the center portion with stub axles projecting laterally outward, said cam- type latch having an opening in each wall of the channel midway between the arm and cam and receiving the stub axles so as to pivotally mount the latch on the elongated strap.    
     
     
       16. A heat sink assembly including a heat sink and a spring retainer clip providing cooling to an electronic integrated circuit device, the device being mounted in a housing, such as a socket or a module, the housing having engagement means for the spring retainer clip, said heat sink assembly comprising: 
       
         a heat sink including a metallic plate with a plurality of fins projecting upwardly from the top surface of the plate defining a series of channels; and  
       
       
         such spring retainer clip comprising two members:  
       
         an elongated, resilient strap received in one of said channels and holding means at each end of said strap for engaging the engagement means on the housing, said resilient strap having a length such that when it is in engagement with the housing, the center portion of said strap is good a pre - determined distance above the upper surface of the heat sink base when the strap is not in tension; and    
         a cam - type latch pivotally mounted in the center portion of said strap and including a cam with a bearing surface, the distance from the pivot access to the bearing surface being greater than the distance between the pivot access and the upper surface of the base of the heat sink when said strap is not in tension, and an arm fixedly mounted to said cam, said arm when rotated causing said cam to bear against the surface of the base of the heat sink placing the strap in tension so as to force the heat sink into heat conducting engagement with the housing.    
     
     
       17. The heat sink assembly of  claim 16  wherein when said arm is rotated, placing the strap in tension, the inner surfaces of the strap adjacent the edge of the housing traps said heat sink to prevent inadvertent lateral movement.  
     
     
       18. A combination heat sink and heat sink retainer clip, for attachment to a rectangular electronic module wherein the rectangular electronic module contains a printed circuit board and at least one semiconductor device, has at least one major wall which is substantially flat and made of a heat conducting material, and includes at least two spaced apart openings each adjacent one of the longer edges of the wall, 
       
         said heat sink having a rectangular base substantially the same size as the electronic module major wall and a plurality of cooling fins defining at least one channel, said at least one channel aligned transversely between the at least two spaced apart openings in the electronic module wall; and  
       
       
         said retainer clip comprising:  
       
       
         an elongated, resilient strap received in said at least one channel and holding means at each end engaging one of the openings in the module wall, said resilient strap having a length such that with each end in engagement with one of the module wall openings, a center portion of said strap is spaced a predetermined distance above the upper surface of the heat sink base when the strap is not in tension; and  
       
         a cam - type latch is pivotally mounted in the center portion of said strap and including a cam with a bearing surface, the distance from the pivot axis to the cam bearing surface being greater than the distance between the pivot axis and the upper surface of the base of the heat sink when said strap is not in tension, and an arm fixedly mounted to said cam, said arm when rotated causing said cam to bear against the surface of the base of the heat sink and placing the strap in tension so as to force the heat sink into heat conducting engagement with the module wall.    
     
     
       19. The assembly of  claim 18  wherein said strap holding means comprises hook- shaped portions at each free end of the strap, the hook - shaped portions being received in the module wall openings to engage the lower surface of the module wall adjacent the opening when the strap is placed in tension.    
     
     
       20. The heat sink assembly of  claim 18  wherein said strap is of generally rectangular configuration and is formed by metal stamping.  
     
     
       21. The heat sink assembly of  claim 18  wherein said cam- type latch comprises a single piece of material formed into a channel, said center portion of the strap is provided with transversely projecting tabs defining a pivot axle, the latch having openings receiving the tab axles.    
     
     
       22. The heat sink assembly of  claim 21  wherein the arm of said cam- type latch includes detent means for retaining the latch arm in the fully engaged position to prevent inadvertent pivoting of the arm into a relaxed position.