Patent Publication Number: US-2005121172-A1

Title: Composite heatsink for cooling of heat-generating element

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      The present application claims the benefit of priority of U.S. Provisional Patent Application No. 60/526,917, filed Dec. 3, 2003 for Edward Lopatinsky the entire content of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates generally to heat-exchanging equipments, and more particularly, to the heatsinks with heat-exchanging means made as fins and/or pins. The present invention is particularly, but not exclusively, useful for cooling systems for regulating the temperature of electronic components.  
     BACKGROUND OF THE INVENTION  
      There are known many types of heatsinks have been known in prior arts. One type of them is the heatsinks comprising a base and heat-exchanging means made as fins and/or pins-fins structures. The most of such heatsinks made as a whole. For example, U.S. Pat. No. 6,667,884 “Heat Dissipating Assembly” comprises the heatsink made as a whole of fins and a base. The base providing thermal contact with the surface of a heat-generating element. These heatsinks are made by using the following types of manufacturing like extrusion, forging or die casting technologies. These types of technologies are the most productive and comparatively least expensive methods.  
      But, according to these technologies there are some limitations in respect to the distance between fins. The last circumstance becomes critical for further sufficient increasing of heat exchange surface and therefore increasing thermal efficiency of known heatsinks.  
      Such types of heatsinks with assisted blowers are often used to remove heat from the heat-generating elements like electronic devices. Cooling is important because if left unchecked, heat can cause electronic devices to malfunction during use or lead to premature device failure. As improvements in processor speed occur, the amount of heat generated by the faster processors also increases. The trend toward smaller electronic devices demanding smaller coolers and having larger, faster processors renders the traditional heat removal cooling systems less effective or inadequate. The heatsink of said systems also should be small. According to the modern requirements the heatsinks should have higher heat exchange efficiency at relative small volume.  
      As well known, the heat exchange efficiency is proportional to the heat exchange surface at all other equal conditions. Therefore, one of the most effective ways for the significant increasing of heat exchange surface of the heatsinks is the increasing of the number of fins by decreasing the fins spacing. These could be realized by the separate manufacturing of fins and base with the following assembling in one for example, by soldering or using the folded fins technology.  
      For example, U.S. Pat. No. 6,698,500 “Heat Sink with Fins” and No. 6,742,581 “Heat Sink and Fin Module” comprise a group of heat dissipating fins and a base plate. The fins are inserted into grooves formed in the base. Such technology allows decreasing the distance between fins and, consequently, increasing the heat exchange surface at the same volume of the heatsink.  
      But, such junction of the fins with the base leads to arising additional thermal resistance between the base and the fins and, therefore, to some decreasing of heat exchange efficiency of the heatsink. And more, such known heatsink design requires more expensive technologies.  
      It would be desirable to provide more thermal efficient design of a heatsink for cooling of heat-generating element with a relative simple and inexpensive fabrication of it. A proposed heatsink would overcome these problems associated with the contradiction between the tendency of further enhancement of the cooling efficiency by decreasing of the distance between the fins and excluding arising additional thermal resistance.  
     SUMMARY OF THE INVENTION  
      According to the present invention the general idea is to increase the heat-exchanging surface at the same volume of the heatsink due to the smaller spacing between heat-exchanging means without arising additional thermal resistance.  
      In order to achieve these objectives, a composite heatsink for cooling of heat-generating element comprises upper and lower components. The upper component comprises a cover plate and a first set of heat-exchanging means thermally connected with one side of the cover plate. The lower component comprises a base and a second set of heat-exchanging means thermally connected with one side of the base while the other side of the base thermally connected with the heat-generating element. The first set of heat-exchanging means located in alternate order in respect to the second set of heat-exchanging means and thermally connected with the base from a side opposite to the heat-generating element, thus forming a plurality of heat exchange channels.  
      According to the preferred embodiment each of the upper and lower components is made as a whole of high heat conductive material. The upper and lower components could be made using the extrusion, forging or die casting technologies. The first and second sets of heat-exchanging means could be made like parallel fins with the same equal spacing located perpendicularly to the cover plate and the base, correspondingly. According to another variant of the heat-exchanging means manufacturing the first and second sets of heat-exchanging means could be made like pins-fins structures with the same equal spacing located perpendicularly to the base and the cover plate, correspondingly.  
      For more even temperature distribution the second set of heat-exchanging means could be thermally connected with the cover plate. The cover plate in this case will serve as a heat spreader.  
      The thermal connection between the first set of heat-exchanging means and the base could be made by soldering. According to the preferred embodiment there is a set of grooves to increase the contact surface between the first set of the parallel fins and the base. These grooves made on the base from the side opposite to the heat-generating element and located between the parallel fins of the second set of heat-exchanging means and spaced apart from each other by the same equal spacing. The grooves have a width and a depth equal to at least the thickness of the parallel fins, thus the grooves are matched with tips of the parallel fins of the first set of heat-exchanging means. In this case the thermal resistance between the base and the first set of the parallel fins will be negligible.  
      The foregoing and other objectives, features and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a top perspective view showing the composite heatsink for cooling of heat-generating element.  
       FIG. 2  is a front view showing the composite heatsink for cooling of heat-generating element.  
       FIG. 2A  is an enlarged A view from  FIG. 2 .  
       FIG. 3  is a top perspective view showing the upper component.  
       FIG. 4  is a top perspective view showing the lower component. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
      Preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.  FIGS. 1-4  show embodiment of the present invention.  
      A composite heatsink  1  ( FIG. 1-2 ) for cooling of heat-generating element  2  comprises upper  3  and lower  4  components. The upper component  3  ( FIG. 3 ) comprises a cover plate  5  and a first set  6  of heat-exchanging means thermally connected with one side  7  of the cover plate  5 .  
      The lower component  4  ( FIG. 4 ) comprises a base  8  and a second set  9  of heat-exchanging means thermally connected with one side  10  of the base  8  while the other side  11  of the base  8  thermally connected with the heat-generating element  2 . The first set  6  of heat-exchanging means located in alternate order in respect to the second set  9  of heat-exchanging means and thermally connected with the base  8  from a side  10  opposite to the heat-generating element  2 , thus forming a plurality of heat exchange channels  12 .  
      According to the preferred embodiment each of the upper  3  and lower  4  components is made of high heat conductive material as upper  13  and lower  14  wholes. These upper  13  and lower  14  wholes could be made using the extrusion, forging or die casting technologies. The first  6  and second  9  sets of heat-exchanging means could be made like parallel fins  15  with the same equal spacing located perpendicularly to the cover plate  5  and the base  8 , correspondingly. According to another variant of the heat-exchanging means manufacturing the first  6  and second  9  sets of heat-exchanging means could be made like pins-fins structures (not shown on Figs.) with the same equal spacing located perpendicularly to the base  8  and the cover plate  5 , correspondingly.  
      For more even temperature distribution the second set  9  of heat-exchanging means could be thermally connected with the cover plate  5  for example by soldering. The cover plate  5  in this case will be serves like a heat spreader.  
      The thermal connection between the first set  6  of heat-exchanging means and the base  8  could be made by soldering. According to the preferred embodiment for increasing of the contact surface between the parallel fins  15  and the base  8 , the base  8  from the side  10  opposite to the heat-generating element  2  further comprising grooves  18 . The grooves  18  are located between the parallel fins  15  of the second set  9  of heat-exchanging means and spaced apart from each other by the equal spacing. The grooves  18  have a width and a depth equal to at least the thickness of the parallel fins  15 , thus the grooves  18  are matched with tips  19  of the parallel fins  15  of the first set  6  of heat-exchanging means. In this case the thermal resistance between the base  8  and the first set  6  of the parallel fins  15  will be negligible.  
      The composite heatsink  1  according to the preferred embodiment of the present invention could be manufacturing by the following way. At the first step the upper  13  and lower  14  wholes being made separately by extrusion of high heat conductive material, for example from copper. For both wholes  13  and  14  the heat-exchanging means being made like the parallel fins  15  with the same equal spacing located perpendicularly to the cover plate  5  and the base  8 , correspondingly. During the same extrusion process for the lower wholes  14  the grooves  18  being formed at the base  8  from the side  10  and located between the parallel fins  15  of the second set  9  of heat-exchanging means and spaced apart from each other by the same equal spacing.  
      At the second step a solder material being placed along the surfaces of the grooves  18  and both upper  13  and lower  14  wholes being disposed one to respect another, thus the tips  19  of the parallel fins  15  of the first set  6  matched with the grooves  18 .  
      And, at the last step, the assembly loaded by weight from the upper side of the upper wholes  13  and being placed inside the heat chamber at the temperature above the melting temperature of the corresponding solder material.  
      The composite heatsink  1  according to the present invention allows to forms relative narrow heat exchange channels while the components  3  and  4  made as wholes. Therefore, such design provides the larger heat exchange surface at the same volume in comparison with known heatsinks without arising additional thermal resistance. Therefore, the composite heatsink  1  has increased heat exchange efficiency and could be manufacturing by using the inexpensive well-known technology.