Abstract:
A snap-in heat sink assembly that has an injection molded one piece frame having a plurality of spring members extending outwardly with protrusions at the free ends thereof. The assembly has a spring located against the frame and an electronic component is located atop of the spring. A heat sink has lateral surfaces with elongated grooves formed along those lateral surfaces. The sink is affixed to the frame by a simple step of inserting the heat sink into the space between the spring members such that the protrusions of the spring members snap into the grooves when the heat sink is in the desired location. By sandwiching the spring between the frame and the electronic component, the spring creates a bias to force the electronic component against the heat sink to assure good conductivity of heat from the electronic component through the heat sink.

Description:
BACKGROUND OF INVENTION 
     The present invention relates to a heat sink for use with an electronic component, and, more particularly, to an assembly of an electronic component and a heat sink that can be readily manufactured and assembled. 
     There are, of course, many types and construction of heat sinks that are used to conduct heat away from electronic components. The heat sinks are normally provided in the form of heat sink assemblies that combine the heat sink itself with the heat generating electronic component. The main purpose of the heat sink assembly is to locate, secure and protect all of the heat sinks in a particular machine. As examples, all welding power sources have heat generating electronic components, and some of those components require an additional means of dissipating the heat produced. Thus, with such electronic components, heat sinks are used to dissipate that heat and such electronic components can include diodes, IGBTs, resistors or any other of the electronic components used in various differing type of apparatus. 
     With present electronic components used in welding apparatus, the heat generating electronic component can be assembled individually into a standard package or can be assembled into a module type of package that may house a plurality of the electronic components and either the single mounting or module type of mounting can be obtained commercially. However, with the individual package, while the cost is relatively inexpensive to the user, there is a need to purchase many of the devices to assemble a welding power source and the sheer number of individual devices make it very difficult to assemble the overall power source with the traditional types of assembly methods. On the other hand, with the modular package, the assembly of the multiple electronic component is simplified since there are less devices to assembly, however the module form of heat sink assembly is more expensive than the purchase of many individual devices. 
     As such, there is also a need to make the manufacturability of the heat sink devices to be as inexpensive as possible and to use mass production techniques in the assembly of the heat sink to the electronic component. Traditionally, one means of attaching the heat generating electronic component to the heat sink is by means of a threaded mounting, such as screws, and then the heat sink and the device assembly is mounted to the frame of the power source with additional screws or other mounting means. If there are a large number of such devices, the assembly can become considerably time consuming and difficult to assemble with conventional methods. 
     Also, with the use of threaded devices, there may also be a need for a lock washer, drilling and tapping of the heat sink and all of such operations and additional mounting hardware contributes to the cost of the manufacture. The screws used to attach the heat sink must also be torqued down precisely. If the screws are torqued too loosely, there is not sufficient heat conducting contact between the electronic component and the heat sink. On the other hand, if the torquing is too tight, there may be breakage or damage to the device. 
     In other heat sink assemblies, spring clips have been used to attach the heat sink to a frame having the electronic component in contact with the heat sink. 
     BRIEF DESCRIPTION OF INVENTION 
     Accordingly, the present invention relates to an assembly for affixing a heat sink in a good heat conducting position to an electronic component that is readily manufacturable and assembled with mass production techniques. With the present invention, the need for mounting hardware is eliminated as is the requirement that there be any additional modifications made to the heat sink to mate it to the electronic component in a good heat conducting relationship. In addition, the present heat sink assemblies of this invention can be made in large quantity, mass produced modules easily and inexpensively and are adapted to be manufactured as various individual assemblies or module type of assemblies with multiple heat sinks. 
     Thus, the heat sink assembly of the present invention comprises a frame that has a bottom surface that is generally a flat surface and which has a plurality of guides that extend upwardly from the flat surface. As will be seen, therefore, there are preferably four guides that combine to form the corners of a rectangle and are dimensioned so that a rectangular electronic component can be placed in the space between the guides and moved toward the bottom surface of the frame and the inwardly narrowing space serves to accurately position the electronic component as it reaches the bottom surface. The frame also has a plurality of spring members that also extend outwardly from the bottom surface of the frame in the same direction as the guides and the spring members have a inwardly facing projections at the free ends thereof. Another preferred feature of the frame is that there may be a plurality of spring guides, also preferably molded into the frame and which project outwardly from the bottom surface to position a spring with respect to the frame as will later be explained. Also the frame may have an indexing protrusion extending outwardly from the bottom surface that interfits with the electronic component to guide that electronic component in the desired position in the heat sink when assembled and again, will be later explained. 
     As can be seen, all of the aforementioned features can be injection molded into a one piece construction and therefore can be produced relatively inexpensively in large quantities. 
     A spring is positioned on the bottom surface of the frame and within the space between the guides. The spring can be a generally central outwardly arched shape with the ends of the spring guided into the desired position against the bottom surface of the frame by means of the spring guides such that the spring can be easily and rapidly inserted into the proper position and be assured of being correctly located. The spring itself is preferably constructed of a metal material. 
     The electronic component is positioned atop of the spring in contact therewith and the electronic component preferably has an aperture that receives the indexing protrusion so that the electronic component can be inserted into the space between the guides where the indexing protrusion enters the aperture and guides the electronic component into its proper position. 
     Finally, there is a heat sink that is affixed to the frame in accordance with the present invention. The heat sink is basically a metal block having a generally planar surface and having a plurality of heat radiating fins that extend outwardly. In one preferred embodiment, the heat sink is extruded of aluminum and has two lateral exterior surfaces with the heat radiating fins being elongated in the same orientation as the lateral exterior surfaces as would be a result of the extrusion process. Each of the lateral exterior surfaces has an elongated ridge formed thereabout and which runs the entire length of each lateral exterior surface. 
     The heat sink is affixed to the frame by means of the interfitting of the inward projections at the free ends of the spring members that snap fit into the ridges formed about the lateral exterior sides of the heat sink and the location of the grooves and the designed length of the spring members is, of course, predetermined so that the heat sink is positioned at a desired location affixed to the frame and the planar surface of the heat sink is fully abutted against the surface of the electronic component so that the heat from the heat generating electronic component can be efficiently transferred to and dissipated through the heat sink. The heat sink is also guided in its seating within the frame as the heat sink enters the space between the guides. 
     The electronic component is forced or biased against the planar surface of the heat sink by means of the spring that is sandwiched between the bottom surface of the frame and the lower surface of the electronic component automatically creating the desired force of the electronic component against the heat sink. 
     As such, the present heat sink assembly is easily assembled and the force of the electronic component that holds it against the heat sink is predetermined and a known force is automatically established for good heat conductivity with no need for an assembler to take any action to set or adjust that force. The assembly of the present heat sink assembly is carried out by a simple one-step operation and therefore is conducive to mass production techniques that are relatively inexpensive and no additional physical alteration, such as drilling, tapping or the like of the heat sink is required that could add to the overall time to construct the heat sink assembly. 
    
    
     These and other features and advantages of the present invention will become more readily apparent during the following detailed description taken in conjunction with the drawings herein. 
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is an exploded view of a heat sink assembly constructed in accordance with the present invention. 
     FIG. 2 is a perspective view of heat sink assembly of the present invention. 
     FIG. 3 is a side view of the heat sink assembly of FIG.  1 . 
     FIG. 4 is cross sectional view of the heat sink assembly taken along the lines  4 — 4  of FIG.  3 . 
     FIG. 5 is an exploded view of a plurality of heat sink assemblies utilizing the present invention. 
     FIG. 6 is an exploded view of a heat sink assembly constructed in accordance with another embodiment of the present invention. 
     FIG. 7 is a perspective view of the heat sink assembly of FIG.  6 . 
     FIG. 8 is a side view of the heat sink assembly of FIG.  6 . 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1, there is shown an exploded view of the heat sink assembly  10  constructed in accordance with the present invention. As can be seen, the heat sink assembly  10  includes a frame  12  having a generally planar upper surface  14  and having downwardly displaced bottom surface  16  that is formed in the frame  12 . Surrounding the bottom surface  16  are a plurality of guides  18  that extend outwardly with respect to the bottom surface  16 . The guides  18  are shown as extending outwardly from the upper surface  14 , however, the guides  18  may also extend outwardly directly from the bottom surface  16 , it only being of importance that the guides extend outwardly with respect to the bottom surface  16 . 
     In the preferred embodiment of FIG. 1, there are four guides  18  and which define a space  20  therebetween with the guides  18  being located at each corner of a rectangular space  20 . Each of the guides  18  is preferably shaped so as to have free ends  22  and an inner surface  24  that is tapered inwardly in the direction toward the bottom surface  16 , that is, the rectangular space  20  narrows in the direction towards the bottom surface  16  so that a rectangular object placed into the space  20  will pass along a narrowing space  20  and be fully guided to its ultimate location at the inner ends of the guides  18 . 
     Also extending outwardly with respect to the bottom surface  16  are a plurality of spring members  26  that are configured so as to have a generally downwardly and inwardly sloping free end  28  leading to an inwardly directed projections  30  formed therein. Again, as shown in the preferred embodiment of FIG. 1, there are two of such spring members  26 . However, more spring members could be used as the width of the heat sink increases. There are also a plurality of holes  32  formed in the bottom surface  16  and the purpose and use of such holes  32  will later become apparent. 
     Accordingly, the frame  12  includes a number of features, and may also include an indexing protrusion (not shown in FIG. 1) that extends outwardly from the bottom surface  16  as well as various spring guides (not shown in FIG. 1) that are also formed in the bottom surface  16 . A preferred plastic material that can be used for the injection molded frame  12  is highly ordered syndiotactic molecular structure based on the polystyrene monomer and marketed under the name Questra 533. Other fabricating materials may also be used. 
     A spring  34  is provided and has a generally upwardly curved or arched upper surface  36  and has upturned outer ends  38 . The spring  34  is preferably constructed of a metal, such as stainless steel, and has dimensions and configuration designed so as to provide a predetermined upward springing action when the upper surface  36  is compressed. In the assembly of the present heat sink assembly  10 , the spring  34  is placed onto the bottom surface  16  of the frame  12  and is guided into the desired position on that bottom surface  16  by means of the spring guides (not shown in FIG.  1 ). 
     As a further component of the heat sink assembly  10  there is an electronic component  40  and which may be any of a number of typical heat generating electronic devices such as diodes, IGBTs, resistors and the like. The electronic component  40  has a plurality of conductive leads  42  that extend outwardly and downwardly toward the frame  12 . 
     As can be seen, the conductive leads  42  extend through the holes  32  when the electronic component  40  is mounted to the bottom surface  16  of the frame and the conductive leads  42  can be wave soldered to a circuit board located on the downward side of the frame  12  as seen in FIG.  1 . Preferably the electronic component  40  also has an opening  44  that mates with the indexing protrusion (not shown in FIG. 1) formed in the bottom surface  16  of the frame  12  to guide the electronic component into the desired location within the frame  12 . The electronic component  40  has a flat upper surface  46  and a lower surface  48 . 
     Finally a heat sink  50  is provided and which is preferably formed of a metal and, in the preferred embodiment, is extruded of aluminum. The heat sink  50  has lateral external surfaces  52 , oppositely disposed, a lower planar surface  54  and a plurality of heat radiating fins  56 . As can be seen the heat radiating fins  56  are elongated or oriented along an axis identified along the centerline A which is basically determined by the extrusion process itself and the external lateral surfaces  52  are generally elongated along that same orientation. An elongated groove or ridge  58  is formed along that same orientation in each of the external lateral surfaces  52 . The elongated grooves  58  are formed along the entire length of each of the lateral external sides  52 . 
     With the foregoing, the basic method of assembly of the heat sink assembly  10  can now be described. Initially the frame  12  is secured to a PC board. The spring  34  is then placed into the frame  12  to rest upon the bottom surface  14  of the frame  12  aided in its location by the use of spring guides (not shown in FIG.  1 ). The electronic component  40  is then placed upon the upper surface  36  of the spring  34  guided by the indexing protrusion (not shown in FIG. 1) that enters into the opening  44  in the electronic component  40  to align and position the electronic component  40  in the desired location. 
     The heat sink  50  is then inserted into the space  20  between the guides  18  and is progressed downwardly until the lower planar surface  54  of the heat sink  50  seats on the upper surface  46  of the electronic component  40  so that there is good heat conductivity therebetween. A silicone based thermal grease is applied to upper surface  46  and heat sink  50  to effect more efficient heat transfer. As the heat sink SO continues to move downwardly, the spring  34  is compressed and exerts a force against the lower surface  48  of the electronic component  40  to cause the electronic component  40  to more forceful contact the heat sink  50 . 
     At the culmination of the predetermined downward movement of the heat sink  50 , the inwardly directed projections  30  of the spring members  26  enter and snap fit into the elongated grooves  58  to secure the heat sink  50  in position locked to the frame  12 , thus completing the assembly of the heat sink assembly  10 . 
     Turning now to FIG. 2, there is shown a perspective view of the heat sink assembly  10  of the present invention with the heat sink  50  affixed to the frame  12  and, as can be seen, the heat sink  50  has become centered within the guides  18  so that it is fitted into the correct position atop of the frame  12 . In the assembled status as shown in FIG. 2, the spring member  26  has become snap fitted into the elongated groove  58  due to the relative flexible nature of the spring member  26  so that the heat sink  50  is tightly held to the frame  12 . As also can be see, the heat radiating fins  56  are all aligned along the center line A in a generally parallel relationship and which is due to the extrusion process used to manufacture the heat sink  50 . 
     The extrusion process makes the manufacturing of the heat sink  50  relatively easy and cost effective and the process also allows considerable flexibility in the ability to manufacture heat sinks of differing sizes, that is, once extruded into long lengths, the individual heat sink is simply cut from the extruded material according to the desired length of any particular heat sink. Accordingly, to manufacture heat sinks of at different size, the cut can be relocated by the manufacturer to whatever length of the lateral external surfaces  52  is desired, it also being seen that the elongated groove  58  will already be formed in the extrusion and thus, the heat sink to be produced only needs to be cut to the size desired and burred. No other physical alterations are needed to the heat sink. 
     Turning now to FIG. 3, there is shown a side view of the heat sink assembly  10 , that is, taken along the extruded direction. In FIG. 3, the frame  12  is affixed to a PC board  60  and the conductive leads  42  extend downwardly to be connected to the PC board  60  by means such as wave soldering. FIG. 3 also illustrates the interconnection of the inwardly directed projections  30  formed at the free ends of the spring members  26  interfitting into the elongated grooves  58  to hold the heat sink  50  fast to the frame  12 . 
     Turning now to FIG. 4, there is shown a cross sectional view of the heat sink assembly  10  taken along the line  4 — 4  of FIG.  3 . Again, as shown, the heat sink  50  is in its assembled position within guides  18  with the electronic component  40  beneath the heat sink  50  with its upper surface  46  held tightly against the lower planar surface  54  of the heat sink  50  in a good heat transfer relationship. The electronic component  40  is forced against the lower planar surface  54  by means of spring  34  that has its arched upper surface  36  exerting a force against the lower surface  48  of the electronic component  40 . As such, since the heat sink  50  has been snapped into the position shown, by design of the spring  34 , the amount of force to create the good heat conducting relationship between the electronic component  40  and the heat sink  50  can be predetermined and there is no need during the assembly process to make any adjustment or modify the force that forces the electronic component  40  and the heat sink  50  together. 
     Again the PC board  60  is also illustrated and can be simply affixed. to the bottom of the frame  12  by means of screws (not shown) that pass through holes in the PC board  60  to thread into holes created in the frame  12  during the injection molding process. 
     Turning finally to FIG. 5, there is shown an exploded view showing the use of multiple heat sink assemblies  10  utilizing the present invention. In FIG. 5, there can be seen an injection molded plastic multiple frame  62  having a plurality of individual sites  64  where an electronic component  40  can be assembled to the multiple frame  62 . Accordingly, each site  64  has a localized bottom surface  16  such that there are a plurality of bottom surfaces  16  at the individual localized sites  64  formed in the multiple frame  62 , each site  64  intended to receive an electronic component  40  in the manner previously described and, of course, for each mounting of an electronic component  40  there are corresponding guides  18  forming spaces  20  between the guides  18  for mounting those electronic components  40  at each of the individual sites  64 . 
     In FIG. 5, there can also be seen the indexing protrusions  66  that extend outwardly from each of the bottom surfaces  16  of the individual sites  64  of the multiple frame  62  and which enter the openings  44  in the electronic components  40  in order to properly and quickly align the electronic components  40  into the desired site  64  within the multiple frame  62  during the assembly process. In addition there are spring guides  66  that also extend outwardly from the bottom surfaces  16  of each of the sites  64  formed within the multiple frame  62  to enable the assembly of the springs  34  easily and to insure that the springs  34  are correctly positioned in each of the desired sites  64  within the multiple frame  62 . 
     With the use of a multiple frame  62 , there are formed rows  68 ,  70 ,  72  of inwardly displaced bottom surfaces  16  so that the electronic components  40  can be assembled in the rows  68 ,  70 ,  72  to mount a plurality of electronic components inexpensively and conveniently for a specific installation. In addition, as can be seen, the individual sites  64  for the electronic components  40  can be staggered horizontally along the vertical rows  68 ,  70 ,  72  so that the individual electronic components  40  can be staggered with respect to an electronic component in any adjacent row, that is, the sites  64  to receive the electronic components  40  in row  68  are displaced away from adjacent spaces in row  70  and the same is true between the rows  70  and  72 . 
     In such manner, the staggering of the individual sites  64  of adjacent electronic components  40  can insure that electrically hot heat sinks  50  are not adjacent to each other but can be physically separated to the extent necessary to prevent electrical problems. Also, the staggered spacing of the heat sinks  50  allows more efficient use of the cooling air that passes across the rows of heat sinks  50  since the air can pass in between the heat sinks  50  more easily and with better flow distribution. 
     Referring now to FIG. 6, there is shown an exploded view of a heat sink assembly  10  constructed in accordance with another embodiment of the present invention. As can be seen, the heat sink assembly  10 ( a ) is similar to the heat sink assembly of FIG.  1  and includes a frame  12 ( a ) having a generally planar upper surface  14 ( a ) and having downwardly displaced bottom surface  16 ( a ) that is formed in the frame  12 ( a ). Extending upwardly from surface  14 ( a ) are guides  18 ( a ). 
     The heat sink assembly  10 ( a ) includes four guides  18 ( a ) which define a space therebetween. Guides  18 ( a ) are located at each corner of the rectangular space. Each of the guides  18 ( a ) is preferably shaped so as to have free ends  22 ( a ) and an inner surface that is tapered inwardly in the direction toward the bottom surface  16 ( a ). That is, the rectangular space narrows in the direction towards the bottom surface  16 ( a ) so that a rectangular object placed into the space will pass along a narrowing space and be fully guided to its ultimate location at the inner ends of the guides  18 ( a ). 
     Also extending outwardly with respect to the bottom surface  16 ( a ) are a plurality of spring members  26 ( a ) that are configured so as to have a generally downwardly and inwardly sloping free end  28 ( a ) leading to an inwardly directed projection  30 ( a ) formed therein. There are two of such spring members  26 . However, more spring members could be used as the width of the heat sink increases. 
     Additionally, the frame  12 ( a ) includes a number of features, and may also include an indexing protrusion that extends outwardly from the bottom surface  16 ( a ) as well as various spring guides that are also formed in the bottom surface  16 ( a ). A spring  34 ( a ) is provided and has a generally upwardly curved surface and has upturned outer ends  38 ( a ). The spring  34 ( a ) is preferably constructed of a metal, such as stainless steel, and has dimensions and configuration designed so as to provide a predetermined upward springing action when its upper surface is compressed. In the assembly of the present heat sink assembly  10 ( a ), the spring  34 ( a ) is placed onto the bottom surface  16 ( a ) of the frame  12 ( a ) and is guided into the desired position on that bottom surface  16 ( a ) by means of the spring guides. 
     Similar to the heat sink assembly of FIG. 1, heat sink assembly  10 ( a ) includes an electronic component  40 ( a ) which may be any of a number of typical heat generating electronic devices such as diodes, IGBTS, resistors, and the like. The electronic component  40 ( a ) has a plurality of conductive leads  42 ( a ) that extend outwardly and downwardly toward the frame  12 ( a ). The electronic component  40  also has an opening  44  that mates with an indexing protrusion formed in the bottom surface  16 ( a ) of the frame  12 ( a ) to guide the electronic component into the desired location within the frame  12 . Electronic component  40 ( a ) has a flat upper surface  46 ( a ) and a lower surface  48 ( a ). 
     Finally, a heat sink  50 ( a ) is provided and which is preferably formed of a metal and, in the preferred embodiment, is extruded of aluminum. The heat sink  50 ( a ) has lateral external surfaces  52 ( a ), oppositely disposed, a lower planar surface  54 ( a ) and a plurality of heat radiating fins  56 ( a ). As can be seen the heat radiating fins  56 ( a ) are elongated or oriented along an axis which is basically determined by the extrusion process itself and the external lateral surfaces  52 ( a ) are generally elongated along that same orientation. Each lateral surface  52 ( a ) includes an upper end defined by a ridge  58 ( a ). The ridge  58 ( a ) defines the top surface or edge of lateral surface  52 ( a ) such that surface  52 ( a ) has a height of approximately half of fins  56 ( a ). 
     Turning now to FIG. 7, there is shown a perspective view of the heat sink assembly  10 ( a ) with the heat sink  50 ( a ) affixed to the frame  12 ( a ) and, as can be seen, the heat sink  50 ( a ) has become centered within the guides  18 ( a ) so that it is fitted into the correct position atop of the frame  12 ( a ). As assembled, spring member  26 ( a ) has become snap fitted due to the relative flexible nature of the spring member  26 ( a ) so that the heat sink  50 ( a ) is tightly held to the frame  12 ( a ). As also can be seen, the heat radiating fins  56 ( a ) are all aligned in a generally parallel relationship and which is due to the extrusion process used to manufacture the heat sink  50 ( a ). 
     Turning now to FIG. 8, there is shown a side view of the heat sink assembly  10 ( a ), that is, taken along the extruded direction. In FIG. 8, the frame  12 ( a ) is affixed to a PC board  60 ( a ) and the conductive leads  42 ( a ) extend downwardly to be connected to the PC board  60 ( a ) by means such as wave soldering. FIG. 8 also illustrates the interconnection of the inwardly directed projections  30 ( a ) formed at the free ends of the spring members  26 ( a ) tightly positioned over the elongated ridges  58 ( a ) to hold the heat sink  50 ( a ) fast to the frame  12 ( a ). 
     Those skilled in the art will readily recognize numerous adaptations and modifications which can be made to the heat sink assembly and method of assembling the same of the present invention which will result in an improved process and apparatus, yet all of which will fall within the scope and spirit of the present invention as defined in the following claims. Accordingly, the invention is to be limited only by the following claims and their equivalents.