Abstract:
The invention provides a load distributed heat sink system for securing a heat sink to a heat-generating electronic component while distributing the load on the circuit board. Provided is a heat sink system having heat sink, a heat sink clip, and a circuit board. The heat sink is generally disposed on one side of the circuit board over a component, and the heat sink clip is generally disposed on the opposing side of the circuit board. The ends of heat sink clip reach to the other side and attach onto the heat sink on. The heat sink clip further includes a load spreader, which is urged onto the circuit board by the heat sink clip, both retaining the heat sink system in place and distributing load on the circuit board.

Description:
BACKGROUND 
     The invention relates generally to heat sink systems. More specifically, the invention relates heat sink attachment systems. 
     Heat sinks are commonly attached to heat-generating components on circuit boards to help dissipate heat more effectively. These components include various processors, digital circuits, power electronic switching devices, and so forth, that generate heat during operation. Heat sinks effectively transfer heat from these components to the air, or other surrounding medium. As heat sinks are designed to provide a much larger air-contacting surface area than the component, the component is able to more effectively dissipate heat when thermally coupled to a heat sink. This helps to prevent overheating of components, which may cause system malfunction and possible eventual failure. 
     Heat sinks can be attached to components and circuit boards through several methods, such as adhesive methods and mechanical methods. Adhesives include thermal tapes, glues, and epoxy, and are appropriate for less massive heat sinks and for use with components with lower power dissipation. Conversely, mechanical attachment methods are more common for heftier heat sinks and components with higher power dissipation. 
     Mechanical methods of attaching heat sinks generally involve securing a heat sink directly to a component or circuit board to be cooled. This is typically done by either screwing the heat sink onto the component or circuit board or clamping the heat sink onto the circuit board. In the case of circuit boards or thinner components, these attachment methods can impart uneven pressure and bend the circuit board, causing damage to solder joints. Damaged solder joints adversely affect the integrity of the circuit, which can cause problems from operational errors to whole system failures. 
     There is need for a means to mechanically attach heat sinks to heat-generating components and circuit boards so that the heat sink is in sturdy contact with the component while evenly distributing pressure, preserving the physical integrity of the circuit board and solder joints connecting to other components. 
     BRIEF DESCRIPTION 
     In an exemplary embodiment, a load distributed heat sink system includes a circuit board comprising an electronic circuit to be cooled disposed on a first side of the circuit board with a heat sink disposed adjacent to the electronic circuit and thermally coupled to the electronic circuit to extract heat from the electronic circuit during operation. The system also includes a clip disposed on a second side of the circuit board opposite the first side, which contacts the heat sink to retain the heat sink in place adjacent to the electronic circuit. There is a load spreader disposed adjacent to the clip, in which the clip urges the load spreader towards the second side of the circuit board to create a force to retain the heat sink in place adjacent to the electronic circuit. 
     In another embodiment, a heat sink system includes a heat sink configured to be disposed adjacent to an electronic circuit disposed on a circuit board and configured to be thermally coupled to an electronic circuit to extract heat from the electronic circuit during operation. The system also includes a clip configured to be disposed on a second side of the circuit board opposite the first side, in which the clip is configured to contact the heat sink to retain the heat sink in place adjacent to the electronic circuit. There is also a load spreader configured to be disposed adjacent to the clip, so that when installed, the clip urges the load spreader towards the second side of the circuit board to create a force to retain the heat sink in place adjacent to the electronic circuit. 
     In another embodiment, a heat sink system includes a clip configured to be disposed on a second side of a circuit board opposite from a first side on which a electronic circuit is disposed that is to be cooled, in which the clip is configured to contact a heat sink disposed adjacent to the electronic circuit to retain the heat sink in place adjacent to the electronic circuit. There is also a load spreader configured to be disposed adjacent to the clip, such that when installed, the clip urges the load spreader towards the second side of the circuit board to create a force to retain the heat sink in place adjacent to the electronic circuit. 
    
    
     
       DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is an exemplary perspective view of a load distributed heat sink system in use; 
         FIG. 2  is an exploded perspective view of a load distributed heat sink system showing a first side of an electronic circuit board and a first side of a load distribution plate; 
         FIG. 3  is an exploded perspective view of a load distributed heat sink system showing a underside of a heat sink, a second side of a circuit board, and a second side of a heat sink clip assembly; 
         FIG. 4  is a side view of a fully assembled load distributed heat sink system; 
         FIG. 5  is a detailed perspective view of a heat sink and a first side of a heat sink clip assembly; and 
         FIG. 6  is a detailed perspective view of a heat sink and a second side of a heat sink clip assembly. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows one embodiment of a load distributed heat sink system, designated generally here as a heat sink assembly  10 . The heat sink assembly  10  comprises a heat sink  12 , an electronic circuit board  14 , wherein the heat sink  12  is usually situated in contact with a heat-generating component on a first side  16  of the electronic circuit board  14 , and a heat sink clip assembly  18  (visible in  FIG. 2 ). The heat sink  12  shown in  FIG. 1  is one example of a variety of heat sinks that may be used with the heat sink assembly  10 . One purpose of one or more embodiments of the heat sink assembly  10  is generally to attach a heat sink to an electronic circuit board without imparting potentially harmful pressure on the electronic circuit board. The electronic circuit board  14  of the heat sink assembly  10  is generally made from fiberglass or any conventional fiber-reinforced resin, and may comprise a plurality of various electronic components. The electronic circuit board  14  may be configured to carry out any desired function, and the invention is not intended to be limited to any particular circuit configuration or operation. Thus, applications of the heat sink assembly  10  may span a wide range of industries and applications. 
       FIGS. 2 and 3  are exploded top and bottom views, respectively, of the heat sink assembly  10  including the heat sink clip assembly  18 . In most embodiments, the heat sink clip assembly  18  is used to attach the heat sink  12  to the electronic circuit board  14 .  FIGS. 2 and 3  also show how the heat sink  12 , electronic circuit board  14  and heat sink clip assembly  18  are generally assembled together to form a heat sink assembly  10  and carry out the function of attaching the heat sink  12 . 
       FIG. 3  shows an embodiment of the heat sink clip assembly  18  comprising a load distribution plate  20  and a clip  22 . The illustrated embodiment shows the load distribution plate  20  to be of comparable length and width to the heat sink  12 , and having a relatively low profile. Generally, the load distribution plate  20  acts as a secondary support which distributes the load applied to the electronic circuit board  14  in order to decrease or eliminate potentially damaging concentrations of stress. The load distribution plate  20  may be made from various materials and can be configured in different shapes and sizes as needed. The clip  22  of the heat sink clip assembly further comprises a set of elbows  24  and a set of hooks  26  at opposing ends. As shown, the clip is generally horizontally attached underneath the load distribution plate  20 , extending past the load distribution plate and bent upward at the elbows  24  towards the electronic circuit board  14 , and ending with the hooks  26 . In some embodiments, the clip  22  comprises a tensile material capable of being deformed with a natural tendency to return to its neutral position. 
     As illustrated in  FIG. 2 , the load distribution plate  20  may include a plurality of standoffs  28  attached to a first side  30  of the load distribution plate  20 . The standoffs  28  may vary in number and can be molded or otherwise manufactured as one entity with the load distribution plate  20 , or they may be attached separately. The standoffs  28  are generally small and short in size, but may take on many configurations. The standoffs  28  may or may not be identical to each other, depending on the configuration of the electronic circuit board  14  and components in the area. 
     As shown in  FIG. 3 , there may be slots  32  formed in the electronic circuit board  14  such that the hooks  26  of the clip  22  can be disposed through the slots  32 , reaching from one side of one side of the electronic circuit board  14  to the opposing side, as shown with dashed lines. The heat sink  12  is placed on the first side  16  of the electronic circuit board  14  generally on top of a heat-generating component  34 , as shown in  FIG. 2 . When the hooks of the heat sink clip assembly are fully disposed through the slots  32 , they may engage the heat sink. The hooks  26  are said to be fully disposed when the load distribution plate  20 , which is generally in between the clip  22  and the electronic circuit board  14 , makes contact with the electronic circuit board  14 . This fully disposed position can be seen in  FIG. 4 . Thus, the heat sink is secured to the first side  16  of the electronic circuit board  14  via the heat-generating component  34  and the heat sink clip assembly is secured to the second side  36  of the electronic circuit board via the standoffs  28 . The heat-generating component  34  mentioned above may be any component that could generally be cooled with a heat sink, including processors, circuit components, switching components, and so forth. 
     The slots  32  formed through the electronic circuit board  14  may be oblong-shaped as shown in  FIG. 2 . However, some embodiments may comprise slots  32  of other shapes and sizes. The purpose of the slots  32  is to provide a means for the hooks  26  of the clip  22  to be able to extend through the electronic circuit board  14  and engage the heat sink  12  while the heat sink clip assembly  18  remains on the opposing side of the electronic circuit board  14 . Alternatively, some embodiments may not include slots  32  at all. For example, in some embodiments, the clips  22  and/or the heat sink clip assembly  18  may be configured such that the hooks  26  of the clip  22  are disposed around the electronic circuit board  14  and engage the corresponding edges of the heat sink  12 , instead of being disposed through the electronic circuit board via slots. 
     Referring now to  FIG. 3 , an embodiment of the second side  38  of load distribution plate  20 , in which the clip  22  is attached to the load distribution plate  20  at a clip joint  40  is shown. It can also be seen in this embodiment that the second side  36  of the electronic circuit board  14  comprises a plurality of components  42  attached to the surface. Here again, components  42  can be various sorts of electronic components such as resistors, capacitors, amplifiers, multiplexors, and so forth. The standoffs  28  attached to the load distribution plate  20  transfer force from the electronic circuit board  14  to the load distribution plate  20  while avoiding contact with any components  42 . The standoffs  28  are strategically mapped on the load distribution plate  20  according to the configuration of components  42  so that no components are present at locations where the standoffs  28  contact the electronic circuit board  14 . This way, the load distribution plate  20  is in contact with the electronic circuit board  14  via the standoffs while components  42  populating the region are not disturbed. 
       FIG. 4  is a side view of one embodiment of the assembled heat sink assembly  10 . It can be seen here how the main parts (e.g. heat sink  12 , electronic circuit board  14 , and heat sink clip assembly  18 ) of the embodied heat sink assembly  10  interact when fully assembled. As shown, the heat sink clip assembly  18  is in contact with the second side  36  of the electronic circuit board  14  and the heat sink  12  is in contact with the first side  16  of the electronic circuit board  14  such that the edges are aligned with the hooks  26  of the heat sink clip assembly  18 . As the hooks  26  engage the heat sink  12 , a biasing force caused by the heat sink clip assembly causes the heat sink  12  and the heat sink clip assembly  18  to be mutually stabilized onto respective sides of the electronic circuit board. In the illustrated embodiment, the heat sink includes lipped flanges  44  for the hooks  26  to hook onto. This is one example of several embodiments in which the clip  22  engages the heat sink  12 . It can be also seen in  FIG. 4  that the clip  22  and heat sink clip assembly  18  of the present embodiment are configured so that the hooks  26  travel through the slots  32  just enough so that a little upward deformation of the clip  22 , generally caused by a small pushing force to the elbows  24  of the clip  22 , allows the hooks  6  to hook onto the lipped flanges  44  of the heat sink  12 . Then, as the clip  22  returns to its neutral position, the spring force of the clip  22  exerts a pulling force on the heat sink onto the first side  16  of the electronic circuit board via the heat-generating component, and a corresponding pushing force on the load distribution plate  20  onto the second side  36  of the electronic circuit board. This increased normal force applied to both the heat sink  12  and the load distribution plate  20  increases the static friction between the heat sink  12  and the heat-generating component  34  as well as between the standoffs  28  of the load distribution plate  20 . In some embodiments, this allows the heat sink  12  and the heat sink clip assembly to become attached to the electronic circuit board. 
       FIGS. 5 and 6  are detailed perspective views of the heat sink  12  and the heat sink clip assembly  18  without the electronic circuit board  14 . One skilled in the art will appreciate that each of these elements can be embodied in different ways, including but not limited to the embodiments discussed below. 
       FIG. 5  shows one embodiment of the heat sink  12 , which includes parallel vertically oriented ridges. Some other embodiments may comprise heat sinks  12  with different configurations and various heat dissipating structures, including existing and newly developed configurations. In some embodiments, the heat sink  12  may have general shapes other than a square. As previously mentioned, the edges of the heat sink  12  may comprise lipped flanges  44  for the hooks  26  of the clip  22  to engage with. The illustrated embodiment shows the heat sink  12  as having these lipped flanges  44  on two opposing edges of a four-sided heat sink  12 . Other embodiments may have lipped flanges  44  on all sides of a heat sink  12 . This may be advantageous as the heat sink  12  may be attached in several orientations. Alternatively, in some embodiments, other hook-receiving elements may replace the lipped flanges  44 . Some embodiments may include a recessed portion of an edge, or there may be slots in the heat sink  12  similar to and aligned with the slots  32  in the electronic circuit board  14 . Accordingly, some embodiments may forego having hooks  26  at the ends of the clip  22 . Instead, some embodiments may employ other engaging mechanisms as a means of stabilizing the heat sink  12  and heat sink clip assembly  18  about the electronic circuit board  14 . This may include one-way inserts and corresponding one-way insert receivers integrated into the heat sink  12 , with or without release mechanisms. There are numerous ways for the heat sink clip assembly  18  to engage the heat sink  12  so that both the heat sink  12  and the heat sink clip assembly  18  are secured to opposing sides of the electronic circuit board  14  that maintain the essence of the present disclosure. 
     The illustrated embodiment shows the clip  22  as a separate entity positioned diagonally across the second side  38  of the load distribution plate  20  and heat staked onto the load distribution plate at the clip joint  40 . The diagonal orientation of the clip  22  may be advantageous in some embodiments, but the clip  22  may be positioned about the load distribution plate  20  in various ways, including laterally. Furthermore, some embodiments may utilize more than one clip  22  or more than two hooks  26 . Some embodiments may comprise two clips positioned perpendicularly to each other such that hooks  26  engage the heat sink  12  at each of the four sides of a four-sided heat sink. Some embodiments may include heat sinks  12  of other shapes as mentioned above, requiring clips  12  of corresponding configurations. Correspondingly, the slots  32  formed in the electronic circuit board  14  may be positioned and configured in various ways to be compatible with the heat sink clip assembly  18  and heat sink  12 . 
     The coupling of the load distribution plate  20  and the clip  22  or clips may be made in a number of ways as well. The clip  12  in the present embodiment comprises outwardly bending elbows  24  that aid in exerting a pulling force on the heat sink  12  when it is engaged with the heat sink  12 . The clip  12  may be positioned in other ways, including remaining flush against the load distribution plate  20 , having a plurality of clip joints  40 , or separated into multiple segments and attached separately with each segment having one hook  26 .  FIG. 6  shows the clip  12  of the present embodiment as being attached to the second side  38  of the load distribution plate  20 . Others ways of situating the clip  12  about the load distribution plate  20  include being molded into the load distribution plate  20  or various other ways of fixing the clip  22  or clips about the load distribution plate  20  or not attached at all. 
     As the heat sink assembly is in use, the heat sink  12  is generally urged onto the heat-generating component by the heat sink clip assembly. Some embodiments may utilize a thermally conductive agent applied between the heat sink underside  46  and the heat-generating component to further facilitate heat transfer and dissipation through the heat sink  12 . 
     While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.