Abstract:
A cooling chamber for computers and for electronic components includes a conductive chamber containing a low boiling point fluid. The components are mounted in the chamber to be bathed by the fluid. The heat energy developed by the components causes the fluid to reach a temperature above the boiling point thus forming bubbles. Bubble guide tubes guide the bubbles upwardly, and fluid confined in the tubes between the bubbles is moved (pushed) upwardly. The cumulative action of the bubbles will cause circulation of the fluid in the chamber thus circulating fluid flow around the electronic components and flow around the chamber. Cooling fins mounted on the exterior of the chamber dissipate the heat generated by the components.

Description:
[0001]    This application claims the benefit of the earlier filing date of the provisional application Ser. No. 61/516,212, filed on Mar. 31, 2011 of the same title and of the same inventor, Troy W. Livingston. 
     
    
     BACKGROUND OF INVENTION 
       [0002]    The present invention relates to system for removing heat from heat generating components, and more particularly to a method and system for removing heat from electronic circuit boards and electronic chips. 
         [0003]    As is well known in the electronics industry, that the heat created by circuit boards and electronic chips during operation is a serious problem. Heat build-up may cause a circuit board or electronic chip to malfunction and cause the entire system to also malfunction or to shut down. The problem has become even more acute due to the fact that circuit boards have become smaller and/or more highly populated with components thus causing the source of heat to become more intense. Accordingly, the heat build-up in circuit boards and IC chips must be efficiently dissipated. 
         [0004]    There are many existing method of heat dissipation from electronic circuit boards, IC chips and electronic systems. These include providing layers of exotic metals, forced gas and liquid cooling, heat convection, pulsating heat pipes, coolant baths and heat transfer directly to the system housing. Liquid cooling systems mentioned above, which are generally the most effective, require a pump to move a coolant from the heat source to a remote heat sink where the heat is dissipated. These latter systems are voluminous and heavy. 
         [0005]    There is a need for providing a method and system for a circuit board and IC chip cooling system which will enable designers and engineers to create and operate electronic systems that are smaller in size and lighter in weight. It is thus an object and purpose of the present invention to address the foregoing problem and to provide a system and method for efficiently removing heat from circuit boards and IC chips which system is itself small and of light weight. 
       SUMMARY OF THE INVENTION 
       [0006]    A cooling chamber for computers and for electronic components is disclosed. The cooling chamber comprises an enclosed heat conductive chamber for containing a fluid having a selected low boiling point. The electronic components that are to be cooled are operatively mounted in the chamber to be bathed by the fluid. The heat energy developed by the electronic components causes the fluid immediately adjacent the component to reach a temperature above the boiling point, and bubbles are created. Fluid turbulence will be induced adjacent to the electronic component. Fluid will circulate, whirl and rotate in the immediate vicinity of the component. The bubbles will rise and cause the fluid to be moved as the bubble rises toward the top level of the fluid. There are of course a large number of bubbles formed and the cumulative action of the bubbles will cause circulation of the fluid in the chamber thus provide circulating fluid flow around the electronic components and around the chamber. Cooling radiators and fins are mounted on the exterior of the chamber to dissipate the heat generated by the components and conveyed by the fluid to the radiators and fins. 
         [0007]    The foregoing features and advantages of the present invention will be apparent from the following more particular description of the invention. The accompanying drawings, listed herein below, are useful in explaining the invention. 
     
    
     
       DRAWINGS 
         [0008]      FIG. 1  is an isometric view to show the environment in which the present invention is utilized; 
           [0009]      FIG. 2  is an end view partially in cross section of the inventive cooling chamber; 
           [0010]      FIG. 3  is an isometric view of the chamber of  FIG. 2 ; 
           [0011]      FIG. 4  is a top view of the cooling chamber; 
           [0012]      FIG. 5  is a relatively enlarged view depicting the whiskers formed by the electro deposition of copper; 
           [0013]      FIGS. 6A ,  6 B, and  6 C show three means for forming sharp points to enhance the formation of methane chloride bubbles; 
           [0014]      FIG. 7  shows a modification of the bubble guide tubes wherein the tubes are tapered; 
           [0015]      FIG. 8  show the mounting of the chamber at an angle relative to the horizontal; and, 
           [0016]      FIG. 9  shows the positioning of an IC chip at an angle to enhance the production of bubbles. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0017]      FIG. 1  is an isometric view of printed circuit board  14 , with discrete components  15  and IC chips  12 , all being of well known types, to show the environment in which the present invention is utilized. 
         [0018]      FIG. 2  depicts one embodiment of inventive system  10  comprising a fluid cooling chamber  11  for integrated circuit (IC) chips  12  and discrete components  15  mounted on an electronic circuit board indicated at  14 .  FIG. 3  is an isometric view of the inventive system  10  and  FIG. 4  is a top view of the chamber  11  which in combination with  FIG. 1  clearly show the structure of the chamber  11 . 
         [0019]      FIG. 2  is a front cut-a-way section which depicts the internal structure of the chamber  11 . Chamber  11  is enclosed in a metal housing  24  and spaced metal fins  25  to provide cooling additional structure are affixed around the housing. Chamber  11  is sealably mounted on printed circuit board (PC)  14 . A number of electrical conductive pins  16  extend from chips and from electronic components  15  and are affixed to PC board  14 . As is known, in operation certain of the chips  12  and electronic components  15  can become undesirable very hot and adversely affect the operation of all the components on the IC chip, as well as the overall electronic system. 
         [0020]    Cooling chamber  11  comprises an enclosed fluid container  16  having a fill port  17  (see  FIG. 3 ) with a suitable plug. A fluid expansion space  18  is provided at the top of the container  16 . In the embodiment of  FIG. 1 , container  16  is filled as (indicated in  FIG. 2 ) with a fluid  19  which is methylene chloride (dichloromethane). The fluid level is indicated by the wavy line  19 C. Methylene chloride is a volatile chemical and will boil at about one hundred three (104) degrees Fahrenheit. Other fluids that have a low boiling point could likewise be used; however, methylene chloride is readily available, effective and inexpensive. As will be explained further herein below, a basic principal of the invention is the concept of generating bubbles  20  in the hot fluid  19  to provide movement and turbulence to the fluid from a source of heat and provide a fluid flow from the heat source to heat dissipaters/sinks to dissipate the heat energy. 
         [0021]    It is known that in the electro deposition of copper whisker growth will occur and normally these phenomenon of whisker growth is an undesired result. However, refer now also to  FIG. 5 , in one embodiment of the present invention, copper electro deposits indicated by the line  21  are made on the PC board  14  to purposefully enhance whisker growth indicated at  22 .  FIG. 5  which is relatively enlarged drawing of the IC chip  12 , clearly depicts the whiskers  22  and bubbles  20 A formed on the whiskers. The whiskers formed on the copper electro deposits  22  provide multiple sharp points that function to provide multiple initiating points for formation of the bubbles  20 A. Note that as shown in  FIG. 5 , a copper electro deposit  22  may be applied to both sides of the IC chip  12  to provide bubbles from both sides of the PC board  14 . 
         [0022]    Referring back to  FIG. 2 , as the methylene chloride fluid  19  is heated above its boiling point, bubbles  20  of methylene chloride will form and rise to the top of the fluid, as depicted in  FIG. 2 . As the bubbles  20  form and rise, the fluid  19  around the bubbles will be disturbed and moved about. Also as depicted in  FIG. 2  the initial bubbles  20 A formed adjacent the whiskers will tend to be small bubbles. As multiple bubbles  20 A continue to be formed adjacent the heat source, the bubbles will tend to coalesce (come together) and form larger bubbles  20 . The bubbles  20  will rise toward the top of the container  16 , fluid flow moving upwardly will result. As the fluid  19  is heated it will expand somewhat and fluid expansion space  18  is provided at the top of container  16 . 
         [0023]    A number of bubble guide tubes  27  are mounted in positions above the IC chip(s)  12  and components  15 . The lower ends of the tubes are formed in a funnel shape  28  to provide an enlarged opening to intercept the upwardly moving bubbles  20 . Thus when the IC chip components  15  become hot and heat the methylene chloride adjacent the hot component to its boiling point of 39.6 degrees C. (104 F), bubbles  20 A will be produced and will coalesce into bigger bubbles  20 . As the bubbles rise up, the funnel shape  28  shape of the guide tubes will intercept and guide the bubbles  10  up the bubble guide tubes  27 . 
         [0024]    After the initially small bubbles  20 A coalesce into larger bubbles  20  the resulting bubbles are approximately 4 mm in diameter. Bubble guide tubes  27  through which the bubbles move also have an internal diameter of 4 mm. As the fluid  19  continues to boil, more bubbles  20  are formed adjacent the hot IC chips components  15  and rise up the tube  27 . The hot fluid  19 A above the bubbles  20  is confined in tube  27  in the spacing between the bubbles. It has been found that the bubbles  10  push (carry) the hot fluid  19 A confined between the bubbles upwardly through the guide tubes  27  (as depicted by the arrow lines generally labeled  29 ). The rising bubbles  10  thus provide a positive pumping, pushing and driving action to move the hot fluid  19 A. When the bubbles  20  are of the same diameter of the guide tubes  27 , the bubbles will also tend to siphon the fluid  19  immediately beneath the bubbles upwardly as the bubbles  20  move upwardly. 
         [0025]    The hot methylene chloride fluid  19 A is thus pumped and moved up tubes  27  by the rising bubbles  20 , and as the hot fluid moves up the bubble guide tubes, the fluid movesheat energy away from the hot IC chips and components. Thus the hot fluid  19 A is moved up the tubes  27  and flows out of the tops of the tubes. Liquid  19 B then returns down around the outside of the tubes  27 . 
         [0026]    The returning fluid  19 B, flows down the inside surfaces of housing  24  and the cooling fins  25  affixed thereto. The metal housing  24  and cooling fins  25  function as heat sinks/heat receptors to remove heat from the fluid  19 . The housing  24  is configured to have some thicker wall areas at  24 A and then tapers to thinner wall at  24 B. The thicker wall area will more effectively absorb the heat energy from the hot fluid  19 . The bottom of wall  24 B can be thinner and lighter since the liquid  19  is cooler at the bottom of the housing  24 . The fins  25  are likewise configured in the same tapered manner to better absorb and dissipate the heat from the hotter fluid  19  at the top of the container  16 . 
         [0027]    Thus heat energy is absorbed from the fluid  19  and conveyed to the housing  24  and the fins  25  and other external heat dissipating structure. The cooled fluid  19  returns down to the PC board  21  and the cycle is repeated. The apparatus of  FIG. 1  thus comprises a heat transfer chamber powered by a passive heat pump. 
         [0028]    Heat receptors or radiator fins  25  are affixed to container  18  which is formed of a copper metal (or other good heat conducting metal) and as the fluid  19  flows down the sides of the container  18 , the container and the radiator fins  25  will remove heat energy from the hot fluid. This action will continue as long as the temperature of the fluid is above the fluid boiling point and bubbles  20  continue to be formed. 
         [0029]    As the fluid  19  is cooled down, and/or as the bubbles get near the top of the chamber and condense, the bubbles break up as the fluid becomes cooler and as heat is extracted from the moving fluid. The bubbles  20  thus provide the pushing or driving force to move the hot fluid in a recirculating loop. 
         [0030]    Also, the bubbles  20  developed by the hot components  15  on the circuit board or IC chip are utilized to generate turbulence and movement in the fluid  19  to cause the fluid to move about or circulate in the container  16 . As the bubbles  20  move the hot fluid  19  upwardly to the top level of the fluid, the heat receptors absorb the heat energy from the fluid, thus cooling the hot fluid and causing the now cooled fluid to circulate or move back down toward the lower levels of the fluid as the heat transfer cycle repeats. 
         [0031]      FIGS. 5A ,  5 B, and  5 C show three modification of the concept of providing sharp points for initiating the formation of bubbles  20 A.  FIG. 5A  show the electro deposition of a copper layer as described above that provide whiskers  22  to provide the sharp points for the bubble formation.  FIG. 6B  depicts the provision of glass bristles or shavings  32  spread on a thin layer of glue  33  to provide the sharp points for bubble formation.  FIG. 5C  depicts forming sharp triangular points  34  by shaping/forming the sharp points on the IC chip  12 . 
         [0032]      FIG. 8  depicts the positioning of the chamber  11  at a 45 degree angle with a horizontal axis. It has been found that the bubbles  10  will form and rise at an angle of approximately eight degrees to the horizontal, hence the chamber  11  may be mounted in a wide range of orientations.  FIG. 8  shows that the bubbles  20  and the hot fluid  19  will move (flow) to the top of the container  16 , and the cooler fluid will return downwardly, as previously described. 
         [0033]      FIG. 7  shows an embodiment of the bubble guide tubes  27 A wherein the tubes are tapered from a wider diameter at the lower end to a smaller diameter at the top of the tube. As stated above, the small bubbles  10 A which are initially formed, coalesce to form the bigger bubbles  10 . As the bubbles  10  move up the bubble guide tubes  27 , they may tend to become smaller in diameter. To assure each of the bubbles  10  continues to fill the tube, the diameter of the tubes may be reduced. This enables each of the bubbles  10  and thus continue to push the fluid  19  upwardly and not let the fluid slide down past the bubble even though the bubble may have become smaller. 
         [0034]      FIG. 9  is a modification of the embodiment shown in  FIG. 1  wherein the IC chip  12  is mounted at a slightly inclined upward angle. The purpose of this construction is to allow bubbles  10 A formed on the bottom of IC chip  12  to more freely move upwardly through fluid  19 . This provides enhanced cooling to both the bottom and the top of the IC chips  12 . 
         [0035]    While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.