Patent Publication Number: US-6981322-B2

Title: Cooling apparatus having low profile extrusion and method of manufacture therefor

Description:
RELATED APPLICATIONS 
   This application is a Continuation-In-Part of prior parent application Ser. No. 09/328,183 filed on Jun. 8, 1999, now U.S. Pat. No. 6,935,409. 

   BACKGROUND 
   The present invention generally pertains to cooling apparatus, and more particularly, but not by way of limitation, to cooling apparatus using “glow profile extrusions”. As is explained in greater detail hereinbelow, such apparatus are extremely useful in printed circuit board (PCB) level cooling of electronic components, and for use as heat exchangers in applications where space is limited and/or low weight is critical. The present invention also pertains to an improved, high volume apparatus and method for manufacturing extruded hollow tubes for heat exchangers and heat pipes, including “low profile extrusions”. 
   As used in this document, the term “low profile extrusion” refers to a heat exchange apparatus comprising an integral piece of metal having a series of micro extruded hollow tubes formed therein for containing a fluid. The low profile extrusions preferably have multi-void micro extruded tubes designed to operate under the pressures and temperatures required by modern environmentally safe refrigeration gases and to resist corrosion. 
   The micro extruded tubes are preferably interconnected at their ends so as to provide fluid communication between each tube. Such low profile extrusions are preferably formed from aluminum, although other conventional metals or metal alloys may also be used. The micro tubes can have a diameter from about 0.0625 inches to about 0.5 inches, but can also have significantly smaller diameters. 
   Such low profile extrusions can currently be manufactured with a profile, or height, as low as about 0.05 inches and with tubes of varying inner diameters. Of course, future advances may allow such low profile extrusions to be manufactured with an even smaller profile. Such low profile extrusions have been conventionally used in heat exchanger applications in the automotive industry, and are commercially available in strip form (having a generally rectangular geometry) or coil form (a continuous strip coiled for efficient transport). Preferred low profile extrusions are sold by Thermalex, Inc. of Montgomery, Ala. A brochure entitled “Thermalex, Inc.—Setting A Higher Standard in Aluminum Extrusions” (hereinafter the “Thermalex Brochure”) provides additional detail regarding the Thermalex low profile extrusions and is incorporated herein by reference. U.S. Pat. No. 5,342,189, which is incorporated herein by reference, provides additional detail regarding an extrusion die for making such low profile extrusions. U.S. Pat. No. 5,353,639, which is incorporated herein by reference, provides additional detail regarding a method and apparatus for sizing a plurality of micro extruded tubes used in such low profile extrusions. 
   SUMMARY 
   In one embodiment, the present invention generally comprises a low profile extrusion, an inlet end cap, an inlet tube, an outlet end cap, an outlet tube, a heat transfer fluid, a means for circulating the heat transfer fluid, end means for removing heat from the heat transfer fluid. The low profile extrusion has a plurality of micro tubes with micro tube inlets and micro tube outlets, and an extrusion surface adapted for receiving heat from at least one heat generating component. The inlet end cap interconnects the micro tube inlets in fluid communication and connects the micro tube inlets in fluid communication with the inlet tube. The outlet end cap interconnects the micro tube outlets in fluid communication and connects the micro tube outlets in fluid communication with the outlet tube. The means for circulating the heat transfer fluid circulates the fluid through the inlet tube, inlet end cap, the plurality of micro tubes in the low profile extrusion, the outlet end cap, and the outlet tube. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the method and apparatus of the present invention may be obtained by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings wherein: 
       FIG. 1  is a schematic illustration of the present invention, shown as a circulation cooling apparatus for removal of heat from certain heat generating components; 
       FIGS. 2 and 3  are schematic illustrations of another embodiment of the present invention, shown as the heat pipe type cooling apparatus for removal of heat from certain heat generating components; 
       FIG. 4  is a schematic illustration of another embodiment of the present invention, shown as heat transfer component of a recirculatory system; 
       FIG. 5A  is a schematic illustration of another embodiment of the present invention, shown as a liquid to liquid manifold cooling apparatus; 
       FIG. 5B  is a schematic illustration of another embodiment of the present invention, shown as a liquid to air manifold cooling apparatus; 
       FIG. 5C  is a schematic illustration of another embodiment of the present invention, shown as an air to air manifold cooling apparatus; 
       FIG. 6  is a is a schematic illustration of a method and apparatus for manufacturing heat pipes according to an embodiment of the present invention; 
       FIG. 7  is a schematic illustration of another embodiment of the present invention, shown as heat pipe base/fin cooling apparatus; and 
       FIG. 8  is a schematic illustration of another embodiment of the present invention, shown as a base/heat pipe fin cooling apparatus. 
   

   DETAILED DESCRIPTION 
   The preferred embodiments of the present invention and their advantages are best understood by referring to  FIGS. 1–8  of the drawings, like numerals being used for like and corresponding parts of the various drawings. The present invention is illustrated herein by example, and various modifications may be made by a person of ordinary skill in the art. 
     FIG. 1  is a schematic illustration of a first preferred embodiment of the present invention showing a cooling apparatus  10  used for removing heat from certain heat generating components  12  mounted on a printed circuit board  14 . The printed circuit board  14  may be housed in a host electronic device (not shown) such as computer, a laptop or notebook computer, or other electronic equipment. Due to the ongoing miniaturization of such host electronic devices, the heat generating components  12  are often located in an area of the printed circuit board  14  and of the host electronic device where space is extremely limited, especially in the “z”, or height dimension. 
   The cooling apparatus  10  generally includes a conventional liquid-to-air heat exchanger  16 , an inlet tube  18 , a low profile extrusion  20 , an outlet tube  22 , a conventional pump  24 , and tubing  26 . The low profile extrusion  20  has a plurality of micro tubes  21 , each micro tube  21  having a micro tube inlet  21   a  and a micro tube outlet  21   b.    
   Micro tubes  21  are formed by a plurality of longitudinal members. The longitudinal members may be vertical or may be offset from vertical. A preferred offset from vertical is between about 5° and 60°. More preferably, longitudinal members are offset from vertical by 30°. Furthermore, longitudinal members may be provided with a capillary groove. The capillary groove may be positioned on an external surface or on the longitudinal members. Further, the capillary grooves may be provided in groups of one, two, three or more. 
   Referring again to  FIG. 1 , the extrusion  20  is preferably formed with a flat surface on its underside  20   a  for contacting heat generating components  12 , and may be formed with external fins on its top side  20   b  to maximize heat transfer, if space allows. It is notable that the micro tubes  21  formed in the extrusion  20  may be of nearly any geometry and that shapes with flattened heat transfer surfaces are generally preferred, but tubes of any shape could be used with varying degrees of efficiency. This is best illustrated in  FIGS. 7 and 8 , where flat extrusions  20  with rectangular micro tubes  21  are shown. Extrusion  20  is also preferably formed with at least one solid channel (not shown) for mounting to printed circuit board  14 . Conventional thermal interface material (not shown) is preferably provided between low profile extrusion  20  and heat generating components  12 . 
   The micro tube inlets  21   a  of the micro tubes  21  in the extrusion  20  are interconnected in fluid communication, and to the inlet tube  18 , by an inlet end cap  28   a . Similarly, the micro tube outlets  21   b  of the micro tubes  21  in the extrusion  20  are interconnected in fluid communication, and to the outlet tube  22 , by an outlet end cap  28   b . Alternatively, micro tube outlets  21   a  and/or  21  may be sealed by crimping the extrusion  20 . Micro tubes outlets  21   a  and/or  21   b  may be individually sealed or connected in fluid communication. The heat exchanger  16  may contain a fluid reservoir (not shown) therein for housing a fluid such as water, glycol, alcohol, or other conventional refrigerants. 
   In addition, a wick, such as screen may be provided within one or all of micro tubes  21 . In this case, fluid from the heat exchanger  16  is circulated through the inlet tube  18 , the low profile extrusion  20 , the outlet tube  22 , and the tubing  26  via the pump  24 . Alternatively, the entire cooling apparatus  10  may be evacuated and charged with fluid which is then circulated via the pump  24 . 
   During operation of the host electronic device, heat generated by heat generating components  12  is transferred from heat generating components  12  to an evaporator section of low profile extrusion  20 , to the fluid circulating within low profile extrusion  20 , and then to heat exchanger  16  from a condenser section of low profile extrusion  20 . Heat exchanger  16  removes the heat from the fluid in a conventional manner. Preferably, an airflow  30  is passed over heat exchanger  16  to aid in such heat removal. Cooling apparatus  10  thus efficiently removes heat from a limited space, low profile area within the host electronic device (the location of low profile extrusion  20 ) to an area where it can be removed at a more convenient location and envelope (the location of heat exchanger  16 ). 
     FIGS. 2 and 3  are schematic illustrations of a second preferred embodiment of the present invention showing a cooling apparatus  40  used for removing heat from heat generating components  12  on printed circuit board  14 . Referring first to  FIG. 2 , cooling apparatus  40  generally comprises a low profile extrusion  42  manufactured as a heat pipe capable of phase change heat transfer. A preferred method of making a low profile heat pipe extrusion  42  is described in greater detail hereinbelow. The low profile heat pipe extrusion  42  is preferably formed with micro tubes  41 , each micro tube  41  having a conventional wick structure such as internal fins, grooved inner sidewalls, or metal screens, so as to maximize their heat transfer capability via capillary action. 
   To form a heat pipe, the micro tubes  41  of the low profile heat pipe extrusion  42  are evacuated and then charged with a fluid such as water, glycol, alcohol, or other conventional refrigerants before sealing the ends  41   a  and  41   b  of the micro tubes  41 . The ends may be sealed by crimping. By providing vertically offset longitudinal members, longitudinal members tend to lay over during crimping rather than buckling. Therefore, vertically offset members may be advantageous. As is known in the art, a heat pipe generally has an effective thermal conductivity of several multiples higher than that of a solid rod. This increase in efficiency is due to the fact that the phase change heat transfer coefficients are high compared to the thermal conductivity of conventional materials. 
   The low profile heat pipe extrusion  42  is preferably formed into an evaporator section or first portion  44  for contacting heat generating components  12  and a raised or condenser section second portion  46 . First portion  44  and second portion  46  are preferably substantially similar in construction to low profile extrusion  20  of  FIG. 1 , except end caps  28  are not required. First portion  44  acts as the evaporator section of the heat pipe, and second portion  46  acts as the condenser section of the heat pipe. 
   During operation of the host electronic device, heat generated by heat generating components  12  is transferred from heat generating components  12  to first portion  44 . This heat causes the liquid within the micro tubes  41  in first portion  44  to change to vapor, consuming some of the generated heat. Because the vapor is less dense than the surrounding liquid, the vapor and associated heat rise into the micro tubes  41  in second portion  46 . Of course, heated liquid may also be transferred from first portion  44  to second portion  46  via the capillary action of the wick structures of the micro extruded tubes therein. In second portion  46 , the vapor condenses into liquid onto the inner side walls of the micro extruded tubes  41 . The heat generated by the condensation reaction, as well as any heat transferred via capillary action of the wick structure, is then transferred to air flow  48 . Cooling apparatus  40  thus efficiently removes heat from a limited space, low profile area within the host electronic device (the location of first portion  44 ) to an area where it can be removed at a more convenient location and envelope (the location of second portion  46 ). Of course, if low profile heat pipe extrusion  42  is formed with internal wick structures, it is not necessary that second portion  44  be raised from, or higher than, first portion  42 . 
   Referring now to  FIG. 3 , low profile heat pipe extrusion  42  is shown in operation with a conventional thermoelectric cooler (TEC)  50  in contact with one of heat generating components  12 . A preferred TEC is sold by Marlow Industries, Inc. of Dallas, Tex. TEC  50  facilitates the heat transfer between the heat generating component  12  and first portion  44  of low profile heat pipe extrusion  42 , and thus is preferred for use with heat generating components  12  that have high power densities. 
     FIG. 4  is a schematic illustration of a third preferred embodiment of the present invention showing a cooling apparatus  60  used for removing heat from a fluid  62 , such as water, glycol, alcohol, or other conventional refrigerants. Fluid  62  is then used to cool conventional heat generating components, such as heat generating components  12  of printed circuit board  14 . By way of example, cooling apparatus  60  may be used in place of conventional heat exchanger  16  in  FIG. 1 . 
   Cooling apparatus  60  generally comprises a low profile extrusion  64 , an inlet end cap  63   a,  an inlet tube  66 , an outlet end cap (not shown), an outlet tube (not shown), thermoelectric coolers  52 , and conventional bonded fin heat sinks  68  and  70 . The low profile extrusion  64  is preferably substantially similar in construction to low profile extrusion  20  of  FIG. 1 , with a plurality of micro tubes (not shown) having a micro tube inlet and a micro tube outlet (not shown). The micro tube inlets of the micro tubes in the extrusion  64  are interconnected in fluid communication, and to the inlet tube  66 , by the inlet end cap  63   a.  Similarly, the micro tube outlets of the micro tubes in the extrusion  64  are interconnected in fluid communication, and to the outlet tube, by an outlet end cap. 
   The low profile extrusion  64  preferably has generally flat bottom and top surfaces for contact with thermoelectric coolers (TEC)  52 . The conventional bonded fin heat sink  68  is coupled to TECs  52  on the top surface of low profile extrusion  64 , and the conventional bonded fin heat sink  70  is coupled to TECs  52  on the bottom surface of low profile extrusion  64 . 
   In operation, the low profile extrusion  64  serves as a manifold, and the TECs  52  remove heat from fluid  62  flowing through the micro tubes of the low profile extrusion  64 . This removed heat is transferred from TECs  52  to bonded fin heat sinks  68  and  70 , which dissipate the heat to atmosphere in a conventional manner. Preferably, airflows  72  and  74  pass over and through heat sinks  68  and  70  to facilitate such heat dissipation. 
   Low profile extrusion  64  has a smaller size and mass than conventional heat exchanger manifolds. For example, a conventional manifold has a minimum profile, or height, in the “z” direction of about 0.75 inches, and low profile extrusion  64  may have a profile as low as about 0.1 inches. The reduced mass of low profile extrusion  64  is believed to produce a cooling apparatus  60  with a near zero time constant, increasing startup performance and temperature control. Therefore, cooling apparatus  60  is especially advantageous in applications involving lasers. The wavelength of a laser beam, and thus beam properties, is strongly influenced by temperature, and the tighter temperature control believed to be provided by cooling apparatus  60  is extremely beneficial. 
     FIGS. 5A ,  5 B, and  5 C are schematic illustrations of fourth, fifth, and sixth preferred embodiments of present invention.  FIG. 5A  shows a cooling apparatus  80  having a plurality of low profile extrusions  64  and TECs  52  arranged in a serial fashion. A TEC  52  is disposed between, and is in contact with, each of the extrusions  64 . Only one low profile extrusion  64  and one TEC  52  is numbered in  FIG. 5A  for clarity of illustration. Fluid  62  enters each extrusion  64  via inlet  66  and exits each extrusion  64  via an outlet  82 . In operation, TECs  52  remove heat from fluid  62  flowing through low profile extrusions  64 . This removed heat is transferred to airflow  84  passing over cooling apparatus  80 . 
     FIG. 5B  shows a cooling apparatus  90  having a plurality of low profile extrusions  64 , TECs  52 , and low profile heat pipe extrusions  92  arranged in a serial fashion. More specifically, a TEC  52  is disposed between, and is in contact with, each low profile extrusion  64  and low profile heat pipe extrusion  92 . Only one low profile extrusion  64 , one TEC  52 , and one low profile heat pipe extrusion  92  are numbered in  FIG. 5B  for clarity of illustration. Each low profile heat pipe extrusion  92  is preferably substantially similar in construction to low profile heat pipe extrusion  42  o  FIG. 1 , excluding raised portion  46 . Fluid  62  enters each extrusion  64  via inlet  66  and exits each extrusion  64  via outlet  82 . In operation, each TEC  52  removes heat from fluid  62  flowing through an adjacent low profile extrusion  64 . This removed heat is transferred to the evaporator portion  92   a  of the adjacent low profile heat pipe extrusion  92 . The heat is then transferred to the condenser portion  92   b  of the low profile heat pipe extrusion  92 , as is explained hereinabove in connection with low profile heat pipe extrusion  42  of  FIGS. 2 and 3 . An airflow  84  passing over cooling apparatus  90  dissipates heat from each condenser portion  92   b  of each low profile heat pipe extrusion  92 . 
     FIG. 5C  shows a cooling apparatus  100  having a plurality of TECs  52  and low profile heat pipe extrusions  92  arranged in a serial fashion. More specifically, a TEC  52  is disposed between, and is in contact with, each low profile heat pipe extrusion  92 , and the “free end” of adjacent low profile heat pipe extrusions  92  extend in opposite directions. Only one TEC  52  and two low profile heat pipe extrusions,  92 ′ and  92 ″, are numbered in  FIG. 5C  for clarity of illustration. In operation, a hot airflow  102  flows over each evaporator portion  92   a  of low profile heat pipe extrusions  92 ′. This heat is transferred from evaporator portion  92   a  to condenser portion  92   b  of extrusion  92 ′, as is explained hereinabove in connection with low profile heat pipe extrusion  42  of  FIGS. 2 and 3 . Condenser portion  92   b  of extrusion  92 ′ is in contact with TEC  52 . The TEC  52  removes heat from condenser portion  92   b  of extrusion  92 ′ and transfers it to evaporator portion  92   a  of low profile heat pipe extrusion  92 ″. This heat is then transferred from evaporator portion  92   a  to condenser portion  92   b  of extrusion  92 ″. Cold airflow  104  passing over condenser portions  92   b  of each extrusion  92 ″ dissipates heat from cooling apparatus  100 . 
   Cooling apparatus  80 ,  90 , and  100  have the same applications and advantages of cooling apparatus  60  described hereinabove. As will be appreciated by one skilled in the art, cooling apparatus  60 ,  80 , and  90  may also be operated as heating apparatus by using thermoelectric coolers (TECs)  52  to heat, rather than to cool, a fluid. 
     FIG. 6  is a schematic illustration of a method and apparatus for manufacturing heat pipes according to a seventh preferred embodiment of the present invention. As noted hereinabove, the preferred apparatus and method may be utilized to make low profile heat pipe extrusions  42  and  92  of  FIGS. 2 ,  3 ,  5 B, and  5 C. However, the preferred apparatus and method may also be utilized to make extruded hollow tubes for other heat exchangers and heat pipes. 
   Apparatus  110  generally includes an oven  112  having an insulated housing. A vacuum station  114  and a fluid charging station  116  are in fluid communication with oven  112 . Alternatively, stations  114  and  116  may be separate from oven  112 . A coil  118  is disposed within a portion of oven  112  on a conventional automatic feed system. Coil  118  may be a coil of hollow tubing, a coil of low profile extrusion, or a coil of other conventional extrusion having a series of extruded hollow tubes therein. Furthermore, coil  118  comprises any material that can be formed and welded with any fluid fill. This includes, but is not limited to aluminum, stainless steel, carbon steel, copper, and titanium alloys. An ultrasonic welder/sealer is also provided. One model of ultrasonic welder/sealer is the Ultraseal® series sold by American Technology, Inc. of Shelton, Conn. A brochure entitled “Ultraseal®-20 20 kHz. Portable Ultrasonic Metal Tube Sealer” (hereinafter the “Amtech Brochure”) provides additional information regarding the Ultraseal® series of ultrasonic welder/sealers and is incorporated herein by reference. A preferred ultrasonic welder/sealer is the Stapla Ultrasonic gantry style seam welder. 
   In a conventional process, the first step is actually forming and cutting the heat exchanger, heat pipe, or extruded tubes into the desired configuration. Next, this preformed system is evacuated and charged with a fluid such as water, glycol, alcohol, or other conventional refrigerants. The system is then sealed, completing the process. Conventional processes are expensive because they are labor intensive and require long setup times for different configurations of heat exchangers, heat pipes, or extruded tubes. 
   However, apparatus  110  may be used to efficiently and economically produce heat exchangers, heat pipes, and extruded tubes, including low profile extrusions, according to the following preferred process. First, coil  118  is placed within a heat producing device such as oven  112  on the automatic feed system. Second, coil  118  is evacuated using vacuum station  114 . Preferably, coil  118  is pulled down to a vacuum of about 10 −7  torr for a period lasting approximately twenty four hours to many weeks depending on performance requirements. Third, coil  118  is charged with a known amount of fluid, such as water, glycol, alcohol, acetone or other conventional refrigerants, using charging station  116 . Acetone is the preferred fluid. Alternatively, coil  118  may be evacuated and charged outside oven  112 . Fourth, oven  112  heats coil  118  until at least some of the fluid is in the vapor phase, and the vapor fills the interior of coil  118  evenly. Fifth, using the automatic feed system, the heated and charged coil  118  is reeled out. Preferably the fluid exits the oven  112  at approximately 40° C. to 60° C. allowing enough thermal inertia to draw vapor into the extrusion external to the oven. A temperature sender container may be provided to ensure that the fluid exit temperature is maintained at a desired level. The coil is then processed by crimping, sealing, and cutting the coil  118  into desired lengths. The temperature difference between the oven  118  and the ambient air (or air-conditioned air) temperature condenses the charging fluid in each pipe before it is crimped. These temperatures and flows are used to control the individual heat pipe fills via a weight analysis. A computer and scale monitor the weight of each part and adjust the oven temperatures accordingly. 
   Subsequent steps comprise crimping, sealing and cutting the coil  118 . A hydraulic press, pneumatic or mechanical means may be used for crimping. An ultrasonic welder/sealer, or another standard welding method such as laser electron beam, resistive, TIG, or MIG welding may be used during the sealing stage. Ultrasonic welding is the preferred process. A plasma cutter, or other standard welding method mentioned herein may be used in the cutting stage. However, the plasma cutter is the preferred method. Finished product is collected within container  122 . In this manner, heat exchangers, heat pipes, and extruded tubes, including low profile extrusions, are formed while charged with fluid, significantly reducing the setup time and vacuum expense over conventional processes. 
   In addition, by separating the coil side of the process from the crimping, sealing and welding process steps, the temperatures for the process steps can be adjusted so as to be in the fluid range for the working fluid. Thus, if a cryogenic heat pipe (charging fluid is typically a gas at normal room temperature) is to be manufactured, the temperature of the process steps would be adjusted such that the charging fluid is a liquid. In a similar manner, high temperature heat pipes, where the charging fluid is typically a solid at room temperatures, can be manufactured. 
     FIG. 7  illustrates another embodiment of the present invention, showing a cooling apparatus  210  used for removing heat from heat generating components  12  on printed circuit board  14 . The cooling apparatus  210  comprises a low profile extrusion  220  manufactured as a heat pipe capable of phase change heat transfer. The low profile heat pipe extrusion  220  is formed having a plurality of micro tubes  230 , preferably having therein conventional wick structure inside such as internal fins, grooved inner side walls, or metal screens, so as to maximize there heat transfer capability via capillary action. The micro tubes  223  of the low profile heat pipe extrusion  220  are evacuated and then charged with a fluid such as water, glycol, alcohol, or other conventional refrigerants, before the ends of the micro tubes are sealed. 
   The low profile heat pipe extrusion  220  has a first surface  221  for engaging the heat generating components  12  and receiving heat transfer therefrom. On a second surface  222  of the low profile extrusion  220 , a conventional bonded fin heat sink  230  or plurality of cooling fins are mounted to the low profile extrusion  220 . Preferably, the micro tubes  223  are disposed in a direction perpendicular to the fins  230  for transfer of heat between each of the individual fins  230 . The heat transfer between the individual fins  230  promotes the even distribution of heat across each of the individual fins  230 . However, the micro tubes  223  can be oriented for the transfer of heat along the length of the fins  230 . Additionally, in one preferred embodiment, the micro extruded hollow tubes  223  in the low profile extrusion  220  are oriented for disbursing heat from the heat generating components  12  to areas of the low profile extrusion  220  which are not in contact with a heat generating components  12 . 
   The use of the low profile extrusion  220  for transferring heat in the cooling apparatus  200  increases the effective surface area that heat is transferred from the heat generating components to the cooling fins  230 . The resulting cooling apparatus is therefore smaller in size and lighter in weight for the same effective cooling attributes. In some embodiments, the present invention can decrease the weight of an apparatus for cooling a heat generating component by as much as 50% over traditional fins mounted via a metal plate. 
     FIG. 8  illustrates another embodiment of the present invention, showing a cooling apparatus  250  used for removing heat from heat generating components  12  on printed circuit board  14 . The cooling apparatus generally comprises a base  260  and a plurality of low profile extrusion fins  270 . The base  260  has a first side  261  for heat transfer between the cooling apparatus  250  and heat generating components  12 . The base  260  also has a second surface  262  for mounting the low profile extrusion fins  270 . 
   The low profile extrusion fins  270  are low profile extrusions manufactured as a heat pipe capable of phase change heat transfer. The low profile extrusion heat piping  270  are preferably formed with a plurality of micro tubes  273  each preferably having a conventional wick structure such as internal fins, grooved inner side walls, or metal screens, so as to maximize the heat transfer capability via capillary action. The micro tubes  273  of the low profile extrusion heat piping  270  are evacuated and then charged with a fluid such as water, glycol, alcohol, or other conventional refrigerants, before the micro tubes  273  are sealed. 
   A first end  271  of the low profile extrusion fins  270  is mounted to the second surface  262  of the base  260  with a second end  272  extending outwardly therefrom. The plurality of low profile extrusion fins  270  are preferably mounted in rows for convection heat transfer to the surrounding environment. In one embodiment, the base  260  can also be formed from a low profile extrusion similar to the low profile extrusion  220  in  FIG. 7 . 
   The use of the heat pipe type low profile extrusion fins  270  in the cooling apparatus  250  increases the effective surface area in which heat is transferred from the heat generating components to the surrounding environment via the base  260 . The resulting cooling apparatus is therefore smaller in size and lighter in weight for the same effective cooling attributes. 
   In operation, the present invention is useful in applications, such as notebook computers, computer network servers, desktop computers, power supplies, chillers/heaters, and telecommunication applications. 
   The present invention is particularly well suited for applications requiring a heat removal apparatus that has minimal spacial area, such as notebook computer applications. A heat pipe according to the principles of the present invention may be extruded with various twists and turns to maximize heat removal ability in a minimal amount of space. 
   For applications involving high performance microprocessors, a heat pipe with fins attached opposite one another on the top and bottom surfaces of heat pipe may be used. This configuration allows improved heat removal characteristics. 
   It is believed that the operation and construction of the present invention will be apparent from the foregoing description of a preferred embodiment. While the device shown is described as being preferred, it will be obvious to a person of ordinary skill in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined in the following claims. Therefore, the spirit and the scope of the appended claims should not be limited to the description of the preferred embodiments contained herein.