Abstract:
Disclosed is a spring clip apparatus for holding one or more heat generating components, such as field effect transistors (FETs) and diodes, firmly against a heat receiving side of a finned heat radiating device having slots within or between the fins. In a finned heat sink, a moving arm of the clip slides into and makes contact with the heat sink in the slot and the confines of the slot prevent further sideways movement while another arm contact point of the clip holds the component firmly in position against the heat sink opposite the moving arm contact point. Clips may be both single and dual arm and may be configured for holding from one to multiple components in contact with the heat sink. The clip may also be used in a similar manner with a non-finned heat sink.

Description:
TECHNICAL FIELD 
   The present invention relates in general to a spring clip for quickly and securely attaching or mounting one or more electrical or other heat generating components to a heat sink or other heat dissipating device. 
   BACKGROUND 
   To remain competitive as technology advances, electronic designers must reduce required system physical space while increasing the system performance. This generally translates into increased power dissipation in a smaller space. However, as is well known, component reliability/life is related to operating temperature. Thus, the challenge is to pack the heat generating components closer together while maintaining acceptably cool temperatures. Traditionally, heat sinks are used to transfer heat from these components to the surrounding environment. 
   There are many prior art methods of attaching heat generating components, such as field effect transistors (FETs) and diodes, to heat dissipating devices. These include screws, straps, adhesives and spring clips of various types. Among the disadvantages of using screws is the time for attachment, along with the problem of electrical insulation of the component from the screw and heat sink. Straps often require some mode of securing them to the heat sink that causes an undesirable increase in space required for the combination of parts. Adhesives have disadvantages with storage and handling and some can fail with time. Further, a good adhesive may well prevent the reuse of the heat sink in the case where a failed component needs replacement. Known prior art spring clips interfere with air flow on the surface of the component(s) being cooled, some being of a design which increase the length of the path from the component to the fins of the heat sink and/or unduly increase the space required for the heat sink/component package relative nearby components. 
   As known among thermodynamic experts, having slots periodically situated in the fins of a heat sink disrupts air flow patterns and results in better heat dissipation than unslotted fins. While the slots are important to disrupt air flow patterns, the wider the slot, the less material is left to conduct and/or radiate heat to the environment. Thus most manufacturers of finned heat sinks have slots of a width just enough to provide adequate air flow disruption. For electronic circuits, these slots are typically about 1/10 inch or less in width. There are, however, many other types of finned and non-finned heat dissipating devices to which heat generating devices need to be attached. 
   It would be desirable if an attachment device could allow quick assembly of one or more components to a heat sink in a secure manner that did not substantially increase package profile dimensions, thereby allowing a higher density packaging, and still allowing replacement of components in a repair mode. It would further be desirable if such attachment device could, without major design modification, be adapted to be used on many different styles of heat dissipating devices. 
   SUMMARY OF THE INVENTION 
   The foregoing disadvantages are overcome by the present spring clip invention, which in a preferred embodiment comprises wire-like spring material of a diameter or width that does not exceed the width of slots in the fins of a heat sink and which further increases the thickness of the combined heat sink/attached component by only the thickness or diameter of the spring clip material. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, and its advantages, reference will now be made in the following Detailed Description to the accompanying drawings, in which: 
       FIG. 1  is an isometric view of a spring clip for attaching a single component to a heat sink; 
       FIG. 2  is an isometric view of the spring clip of  FIG. 1  holding a component to a heat sink using blade type fins; 
       FIG. 3  is a top view of the apparatus of  FIG. 2 ; 
       FIG. 4  is an isometric view of a version of the spring clip for holding a pair of components to a heat sink; 
       FIG. 5  is an isometric view of the spring clip of  FIG. 4  holding a pair of components to a heat sink; 
       FIG. 6  is an isometric view of the spring clip of  FIG. 4  holding a pair of components to a heat sink using pin fins; 
       FIG. 7  is an isometric view of another version of a spring clip for attaching a single component to a heat sink; 
       FIG. 8  is an isometric view of the spring clip of  FIG. 7  holding a component to a heat sink; 
       FIG. 9  is an exploded isometric view of the parts used to attach four components to a single heat sink using a pair of spring clips of slightly different configuration; 
       FIG. 10  is an isometric assembled view of  FIG. 9 ; and 
       FIGS. 11 through 20  are isometric front and back views illustrating the use of the spring clip attaching a heat generating device to various other designs of heat dissipating devices. 
   

   DETAILED DESCRIPTION 
   In  FIG. 1 , a spring clip for attaching a single component to a heat sink is generally designated as  100 . The clip  100  may be constructed from a single piece of material, such as a spring steel piece of wire. The clip  100  includes two generally curved spring length arms or slot pressure arms  102  and  104  that fit into fin slots of a heat sink. These arms  102  and  104  comprise the main moving or flexing portions of the clip although any portion of the clip may be temporarily deformed during the assembly process as long as the material is not deformed past its elasticity point. The arm  102  extends to a bit portion  106 , which bit portion conforms to an area at an edge of the heat sink. In a similar manner, the arm  104  extends to a bit portion  108 . A component holding or clamping arm  112  extends at an angle to the bit portion  106  in a direction to hold a component stationary against the non-finned side of a heat sink. A further component holding or clamping arm  110  extends at an angle to the bit portion  108  in a direction to hold the component stationary against the non-finned side of a heat sink. A further portion of the clip  100 , designated as  114 , completes an extension of the arms  110  and  112  and acts as the clip contact point for applying a substantial pressure against a component to maintain good heat transmitting contact between the component and the heat sink. As will be realized, a thermally conductive but electrically isolating insulator may need to be used between the component and the heat sink with some component packaging designs. As may be further noted, a bent portion of arm  104  is labeled  116  and a similar bent portion of arm  102  is labeled  118 . The portions  116  and  118  provide the contact points of the clip on the fin side of the heat sink. In a typical design of the clip, the vertical distance from bit portions  106  and  108  on the edge of the heat sink to contact points  118  and  116 , respectively, will be substantially the same as the vertical distance from these same bit portions  106  and  108  to the contact point  114 . In other words, the pressure applied to the component is substantially the same distance from the edge of the heat sink as the pressure applied directly to the heat sink on the fin side of the heat sink. It will be realized that this typical design is not required to practice the invention. 
   The portions  110  and  112  may be configured to enclose the component on each side to prevent sidewise movement of the component. The undesignated curved portions between contact point  114  and the portions  110  and  112  may be raised from the surface of the component being held. The raising of these portions allows the use of a fingernail or other tool to easily raise this portion of the clip  100  to facilitate the installation, removal or repositioning of a component contiguous a heat receiving portion of a heat sink. 
   In  FIGS. 2 and 3 , it may be seen that a component  200  is held in place by the spring clip  100  of  FIG. 1  to transfer heat to a heat sink  202 . A piece of electrical insulating material  204  prevents electrical contact between the component  200  and the heat sink  202 . As shown, the heat sink  202  has a plurality of fins  206 , only a few of which are specifically designated. Three slots  208  are illustrated in the fins  206  and the portions  102  and  104  of the clip  100  are inserted into two of the slots  208 . 
   In  FIG. 4 , a spring clip for attaching a pair of components to a heat sink is generally designated as  400 . The clip  400  is constructed in a manner similar to that of clip  100  and has the various portions labeled in a manner similar to that of clip  100  except that they are  400  series designators and that there are two clip contact points  414  and  415  for applying a substantial pressure against a pair of components to maintain good heat transmitting contact between the components and the heat sink. A raised portion  420  between contact points  414  and  415  allows the use of a fingernail or other tool to easily raise this portion of the clip  400  to facilitate the installation, removal or repositioning of a component contiguous a heat receiving portion of a heat sink. 
   In  FIG. 5 , an assembly having two components  500  and  501  are shown held in place against a heat sink  502  by the clip  400  of  FIG. 4 . Again, a piece of insulating material  504  prevents electrical contact between the components,  500  and  501 , and the heat sink  502 . It may be noted that pressure arms  402  and  404  will act independently and thereby accommodate the possibility of component  500  being of thickness different from that of component  501 . 
   In  FIG. 6 , a pair of components  600  and  601  are held in place against a heat sink  602  by the clip  400  of  FIG. 4 . This heat sink uses a large plurality of pin type heat dissipating fins  606  as opposed to the slotted blade type fins of the previous figures. Again, the diameter or width of the spring clip needs to fit in the slots between the pins  606 . It may be noted that heat sinks of this type may have either rectangular or round pin type fins. 
   In  FIG. 7 , a spring clip for attaching a component to a heat sink is generally designated as  700 . The clip  700  is constructed in a manner similar to that of clip  100  except that it has a single slot contact point  718 . Otherwise, it has the various portions labeled in a manner similar to that of clip  100  except that they are  700  series designators. To maintain equivalent heat transmitting contact pressure between the component and the heat sink, the spring force of such a spring needs to be about twice that required of clip  100 , which has two arms to provide force. As an aside, since clip  400  is holding two components in place, the spring force of this clip also needs to be increased over that of clip  100  in order to obtain the same heat transfer from the two components as provided by the single component clip  100 . A raised portion  712  allows the use of a fingernail or other tool to easily raise this portion of the clip  700  to facilitate the installation, removal or repositioning of a component contiguous a heat receiving portion of a heat sink. An optional projection  720  may alternatively be used for this feature when there is adequate room. 
   In  FIG. 8 , an assembly having a component  800  is shown held in place against a heat sink  802  by the clip  700  of  FIG. 7 . Again, a piece of insulating material  804  prevents electrical contact between the component  800  and the heat sink  802 . 
   In  FIG. 9 , a pair of dual component spring clips  900  and  902  are shown for attaching components  904 ,  906 ,  908  and  910  to a heat sink  912 . Increased component density can be obtained using this variation of the clip design. The clip  900  holds components  906  and  908  in place against an intervening electrical insulating material  914  in a manner shown in previous figures. The arms of clip  900  are inserted in slots  918  of fins  916 . Subsequently, the clip  902  is clipped over the components  904  and  910  using slots designated as  920 . As shown, the two clips are of different widths and lengths. The same designators are used in the assembled view of  FIG. 10 . 
   It may be noted that slots have been cut in the top of the heat sink  912  to minimize the height of the assembled product. However, unless the height of the assembly is critical, such slots are typically not necessary and are not shown in the other illustrated heat sinks. 
   In  FIGS. 11 and 12 , the spring clip of  FIG. 1  is shown used with a non-finned heat dissipating device. 
   In  FIGS. 13 ,  14 ,  15  and  16 , the spring clip of  FIG. 1  is shown used with other types of finned heat dissipating devices. 
   In  FIGS. 17 ,  18 ,  19  and  20 , the fins are not slotted and the clips of  FIGS. 1 and 7  are shown inserted between fin rows. 
   While the heat dissipating devices shown in  FIGS. 11-20  are not as efficient at dissipating heat from heat generating devices as the fin slotted heat sinks of  FIG. 2 , such less efficient heat sinks may advantageously be used for cost, space and other reasons. As may be observed, the present spring clip design need not be changed to accommodate attachment of heat generating devices to any of many different heat sink styles and designs. 
   In summary, disclosed is a clip design that does not disruptively interfere with heat dissipating air flow in the vicinity of the heat sink or component and does not increase the heat transfer path from the heat generating component to the heat sink fins. Further, the present clip requires no modification of present heat sink designs and adds minimal weight to an assembly. Even further, components may be quickly assembled or detached and replaced when necessary. Additionally, the present clip does not substantially increase the package profile. 
   Although the invention has been described with reference to specific embodiments, these descriptions are not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that the claims will cover any such modifications or embodiments that fall within the true scope and spirit of the invention.