Abstract:
The invention relates to a novel design of a cooler in the form of a heat pipe, with a housing in which an interior space closed to the outside is formed to hold a liquid, vaporizable coolant or heat-transport medium.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a cooler, in particular, a cooler for electrical components, in the form of a heat pipe. 
     Coolers of this type are fundamentally known and are based on the principle of vaporization and condensation of a coolant, or heat transport medium, housed in the closed interior of the cooler. Generally these coolers have a round structure (U.S. Pat. No. 3,537,514). Lengthwise grooves are used as the capillary structure. These round coolers must be connected to a flat carrier on which the components to be cooled are located. These carriers yield additional heat transfer or thermal resistance. 
     Furthermore, it is also known to have a flat design for this cooler (U.S. Pat. No. 5,642,775). These known coolers consist of a block in which tubular channels are formed. Production is complex and expensive. 
     Furthermore, it is also known to have a cuboidal cooler (U.S. Pat. No. 4,957,803); its housing consists of a plurality of metal layers stacked on top of one another and connected superficially to one another, which are structured and arranged such that within the body, slots yield crossing channels which are joined to one another at the crossing points. This known design is only suited as a thermal spreader. There are no differing vapor channel and capillary structures. In addition, heat transport over long distances is necessary. 
     The object of the invention is to devise a cooler with improved properties. 
     SUMMARY OF THE INVENTION 
     The cooler as claimed in the invention is characterized by a simple and economical production. Transmission of heat energy from the outside, into the vaporization area, into the cooler, or from the condensation area to the outside over a short distance is possible by posts which are located in the area of the capillary structure and which are formed by the metal layers. Furthermore, the cooler has a vapor channel area or a vapor channel structure with a large flow cross section, yielding optimum cooling output. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is detailed below using the following figures: 
         FIG. 1  shows, in a simplified perspective view, a cooler in the form of a flat, plate-shaped or cuboidal heat pipe; 
         FIG. 2  shows a section along line I—I of  FIG. 1 ; 
         FIGS. 3 and 4  show other possible embodiments of the cooler of the invention; 
         FIG. 5  shows in an enlarged partial representation, and in a side view, the heat pipe, as claimed in the invention, formed by a stack of several metal layers; 
         FIGS. 6 and 7  each show in a simplified view, and in an overhead view, two individual or metal layers for example of copper for the capillary area ( FIG. 6 ) and the vapor channel area ( FIG. 7 ); 
         FIG. 8  shows, in a partial schematic, a section through the capillary area, or through the vapor area, of  FIGS. 6 and 7 ; 
         FIGS. 9 and 10  show, in an overhead view, structured metal layers for the capillary area, or the capillary structure, ( FIG. 9 ) or for the vapor channel area or the vapor channel structure ( FIG. 10 ) in another possible embodiment of the invention; 
         FIGS. 11 and 12  each show, in a partial representation, the two stacked metal layers of  FIG. 9  for the capillary area; 
         FIG. 13 , in a partial representation, shows an overhead view of a partial structure of the capillary area formed by two successive metal layers of  FIGS. 11 and 12 ; 
         FIGS. 14 ,  15  and  16  show representations similar to  FIGS. 11 ,  12  and  13  for the vapor channel area; 
         FIGS. 17 and 18  show, in an enlarged partial representation, and in an overhead view, similar to  FIGS. 11 and 12 , individual metal layers for the capillary area of another possible embodiment; 
         FIG. 19  shows, in a partial representation, an overhead view of a partial structure of the capillary area formed by two successive metal layers of  FIGS. 17 and 18 ; 
         FIGS. 20 ,  21  and  22  show representations similar to  FIGS. 17 ,  18  and  19 , but for the vapor channel area; 
         FIG. 22  shows the two layers of  FIGS. 20 and 21  on top of one another for forming the vapor channel area; 
         FIG. 23  shows, in the representation of  FIG. 1 , another possible embodiment of the invention; 
         FIG. 24  shows a section along line II—II of  FIG. 23 , for the sake of simplicity only, the capillary area, or the capillary structure being shown; 
         FIG. 25  shows a section along line III—III or IV—IV of  FIG. 23 , for the sake of simplicity only the capillary area or the capillary structure being shown; 
         FIG. 26  shows, in a simplified representation, and in an overhead view, one metal layer for the capillary area; 
         FIGS. 27 and 28  each show, in a simplified representation, and in an overhead view, two additional embodiments of one metal layer for the vapor channel area; and 
         FIG. 29  shows, a representation similar to  FIG. 24 , another possible embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIGS. 1–22 , a heat sink or cooler for dissipating the heat of a heat source is labeled  1 . The cooler  1  is built as a heat pipe, but in contrast to the known heat pipe arrangements, the cooler  1  has a very flat plate-shape with flat surfaces on the top and bottom. In the embodiment shown in  FIG. 1 , the cooler  1  is shown in an overhead view with a rectangular peripheral line, or with the shape of a very flat cuboid, which is rectangular in an overhead view. 
     Generally the cooling or vaporizer area (first area) is labeled  2 , and the second area for heat dissipation, or the condenser area, is labelled  3 . The two areas are offset against one another in the lengthwise direction L, of the plate-shaped cooler  1 , and on either side of a center plane M, which inter sects the cooler  1 , and its lengthwise sides vertically. The heat dissipated on the area  2 , to the cooler  1  is labelled with an arrow P 1 , and the heat dissipated by the cooler  1 , on area  3 , is labelled by an arrow P 2 . The heat source is formed by the semiconductor power components which are provided on the closed flat top and/or bottom of the cooler  1 , on area  2 , the flat top and/or bottom being formed by one metal layer  7  (metal foil or plate). 
     In  FIG. 2 , these semiconductor power components, or chips, which produce heat loss, are labelled  4 – 6 . For electrical insulation on the top and/or bottom of the cooler  1 , there is provided, at least in the area of chips  4 – 6 , one ceramic layer  7 ′, which is connected in a suitable manner to the closed metal layer  7 , which forms the top and bottom of the cooler. 
     The inner structure of the cooler  1 , and how it works, in general, follow from  FIG. 2 . The inner structure consists of three areas which each extend over the entire cooler, and which are stacked on top of one another, between the top and bottom metal layer  7 , more specifically it consists of two outer capillary structures or areas  8 , and a middle vapor channel, or vapor channel area, or vapor channel structure  9 . The capillary areas  8  are formed by a host of channels which extend between the two areas  2  and  3  and are connected, in at least these areas to the vapor channel or the vapor channel area  9 . The vapor channel is a continuous channel which extends over the entire length and width of the cooler  1 , or is formed, in the manner detailed below, by a structure of several individual channels, the entire cross section of the vapor channel being much larger compared to the overall cross section of the capillary areas  8 . 
     The interior of the cooler  1  is partially filled with a coolant which vaporizes when heated. In the simplest case water, also in mixture with an additive, for example, methanol, is suited as the coolant. 
     How the cooler  1  works is based on the fact that the heat which has flowed onto the area  2  vaporizes the coolant there within the cooler and the vapor then flows in the vapor channel  9  from the area  2  in the direction to the area  3 , i.e. in the direction of the arrow A of  FIG. 2 . On the area  3 , the heat is dissipated to the outside according to arrow P 2 . This leads to condensation of the coolant, which as condensate travels into the capillary areas  8 , and from there under capillary action flows back opposite the arrow A of  FIG. 2  on the area  2 , where then again vaporization of the medium takes place by the absorbed heat P 1 , etc. The cooler  1 , with reference to the vaporizable coolant provided in the interior of this cooler, forms a closed system, as is inherently known of heat pipe systems. 
       FIG. 3  shows again in a simplified representation, the cooler  1 , and on the area  3 , cooling elements, or cooling sheets  10 , being provided on the outside, which with a large surface cause dissipation of the heat to the outside according to arrow P 2 , and through or around, by an air stream generated by fan flows. 
       FIG. 4  shows in a similar representation to  FIG. 3 , an auxiliary cooler  11  which is located on the area  3  and through which a coolant or heat-transporting medium of an external cooling system flows, for example, cooling water of an external cooling circuit. This auxiliary cooler  11  can be formed directly on the area  3  of the cooler  1  by several metal layers which are stacked on top of one another and which are joined superficially to one another and in the housing of the auxiliary cooler  11  form internal, closed cooling channels through which the external coolant flows. In particular, it is possible to form the auxiliary cooler  11  as a so-called microcooler, as is described for example in DE 197 10 783. 
     As is indicated in  FIG. 5  with  12  and  13 , the cooler  1  is formed by a plurality of metal layers, for example copper layers or plates, or cutouts from a copper foil, which are structured such that within the cooler  1  between these layers, and/or through these layers, the capillary structures  8  through the metal layers  12 , and vapor structures  9  through the metal layers  13 , with the corresponding channels which extend at least in the lengthwise direction L result. 
       FIGS. 6–22  show different embodiments for the cooler  1  which differ essentially only by the different structuring of the metal layers  12  and  13 . 
     According to the embodiment of  FIGS. 6–8 , to form the capillary structures  8  metal layers  12   a  and  12   b  are used which are each provided with a plurality of continuous parallel slots, the slots  14   a  in the metal layers  12   a  extending transversely to the lengthwise direction L and the slots  14   b  in the metal layers  12   b  extending in the lengthwise direction L. 
     For the vapor area, or the vapor channel structure  9 , there are metal layers  13   a  and  13   b , which in turn have slots  15   a  and  15   b , which correspond to slots  14 , and slots  15   a  in the metal layer  13   a  perpendicular to the lengthwise axis L and slots  15   b  in the metal layer  13   b  in the lengthwise direction L. The design is such that the axial distance of two adjacent slots  14   a  and  14   b  is the same not only on the metal layers  12   a  and  12   b , but is also equal to the axial distance of two slots  15   a  and  15   b  on the metal layers  13   a  and  13   b . In any case, the width of the slots  15   a  and  15   b  is roughly 1.5–10 times greater than the width of the slots  14   a  and  14   b . Furthermore, the thickness of the metal layers  13   a  and  13   b , is roughly 1–3 times the thickness of the metal layers  12   a  and  12   b.    
     The stacking of the metal layers  12   a  and  12   b  forms capillary structures  8  with crossing channels, which are connected to one another, at the crossing points, and which are formed by the slots  14   a  and  14   b . Likewise, by stacking the metal layers  13   a  and  13   b  on top of one another, a vapor structure  9  is achieved with crossing channels, which are connected to one another at the crossing points, formed by the slots  15   a  and  15   b . This approach results in that after joining the metal layers by the latter within the body of the cooler  1  produced in this way, continuous post-like areas  16  are formed, which extend from the top metal layer  7 , which tightly seals the upper capillary area  8 , as far as the lower metal layer  7 , which tightly seals the lower capillary area  8 , and which deliver the necessary strength for the cooler  1 , and also ensure optimum heat conduction into and out of the cooler  1 . These post-like structures  16  are indicated in  FIG. 5  with a broken line. 
     The metal layers  12  and  13 , can also be structured differently to form structures  8  and  9 . Another example is shown in  FIGS. 9–16 .  FIG. 9  shows a structured metal layer  12   c  for the capillary structures  8 . This metal layer  12   c  is provided in its middle area, i.e. within a closed edge area  17 , in the manner of screen with a plurality of openings  18  which are each made hexagonal and which adjoin one another similarly to a honeycomb structure. These openings  18  are each formed by crosspieces  19 , which pass into one another and which surround each opening  18  in the form of a hexagonal ring structure. On the edge area  17  the openings  18  are only partially formed. 
     On three corners of the hexagonal ring structure of each opening  18 , the crosspieces  19  form an island  20  with an enlarged area, i.e. in the embodiment shown with a circular surface. The islands  20  are distributed such that on each opening  18 , in an assumed peripheral direction one corner with an island  20 , follows one corner without one such island  20 . Furthermore, the structuring is chosen such that two crosspieces  19  of each opening  18 , lie parallel to the lengthwise axis L, of the rectangular metal layer  12   c , and in one axial direction parallel to the lengthwise axis L one island  20 , is followed by an opening  18 , one corner point without an island, one crosspiece  19  which extends in the direction of the lengthwise axis L, and then a new island  20 , etc. 
     Furthermore, structuring of the metal layer  12   c  is not completely symmetrical to a center axis which runs perpendicularly to the lengthwise axis L, but the openings  18  are offset relative to the center axis such that it does not intersect the crosspieces  19 , which run parallel to the lengthwise axis L, but intersects the islands. In this way, to form the capillary structures  8 , it is possible to provide in alternation, one metal layer  12   c  in the form shown in  FIG. 9 , as a layer N ( FIG. 11 ), and as the subsequent layer N+1, one metal layer  12   c  in a layer turned around the center axis ( FIG. 12 ), following one another in order to obtain the structure shown in  FIG. 13  in which the islands  20  of these layers N and (N+1) lie on one another, while in the middle of each opening  18 , of one layer, there is an area of the adjacent layer on which three crosspieces  19  meet one another without an island  20 , as is shown in  FIG. 13 . With the described structuring of the metal layers  12   c  therefore using the same metal layers, very finely structured capillary areas  8  with channels widely branched in all three solid axes can be produced simply by turning every other layer. 
       FIG. 10  shows a representation like  FIG. 9 , with a metal layer  13   c  for producing the vapor channel structure  9 . The metal layer  13   c  in its structuring corresponds to the metal layer  12   c , and differs from it simply in that some of the crosspieces  19 , which run transversely to the lengthwise axis L, were omitted, such that the remaining crosspieces  19 , together with the islands  20 , form zig-zag band-like structures  21 ′, which extend in the lengthwise direction L, with passages  21 , which lie in between and which extend in the lengthwise direction. According to  FIG. 16 , the vapor channel area  9  is formed by at least two metal layers  13   c  being stacked on top of one another, and connected to one another, such that every other metal layer  13   c  is turned around the center axis so that also in the vapor area  9 , the islands  20  of the individual layers  13   c , come to rest on one another and in this way form continuous, post-like structures  16 . The passages  21  yield flow channels with larger effective flow cross section for the vapor area  9 . 
       FIGS. 17–22  show as further embodiments, metal layers  12   d  for forming the capillary structures  8 , and the metal layers  13   d , for forming the vapor channel structure  9 .  FIGS. 17 and 18  in turn show the same metal layer  12   d , but  FIG. 18  in a layer turned around the center axis relative to  FIG. 17 . Likewise,  FIGS. 20 and 21  show the same metal layer  13   d , but in  FIG. 21  in a layer turned around the center axis relative to  FIG. 20 . 
     The metal layer  12   d  is structured in the manner of the screen within the closed edge area  17 , with a plurality of angled openings  22  which are oriented with the angle bisector of their angle segments parallel to the lengthwise axis L. 
     To form the respective capillary structure  8 , at least one metal layer  12  in an unturned form and one metal layer  12  in a turned form, are placed on top of one another, and are connected to one another, such that then the partially overlap ping openings yield passages  23 , via which the channels formed by the openings  22 , in the individual layer, are joined to one another, into a widely branched channel structure, and in addition, post-like areas  16  result. 
     As  FIGS. 17 and 18  show, the openings  22  are each located in several rows which follow one another in the direction of this lengthwise axis and which run perpendicular to the lengthwise axis L, the openings  22  each being offset from row to row on gaps. 
     The metal layer  13   d , shown in  FIGS. 20 and 22 , differs from the metal layers  12   d , simply in that, in addition to the openings  22 , there are continuous openings which are bordered on the end by the edge area  17 , and which extend in the lengthwise direction L, such that in turn band-like structures  24 ′ result, which extend in the lengthwise direction and which also have openings  22 . By placing one unturned metal layer  13   d , and one turned metal layer  13   d , on top of one another on the band-like structures, additional channels are formed which are connected to one another via the passages  23 , and also the post like areas  16 , which adjoin the areas  16  in the capillary areas  8  and are added to the continuous posts  16  between the metal layers  7 . 
       FIG. 23  is another representation according to  FIG. 1 .  FIG. 23  shows a cooler  1   a  in the form of a heat pipe. In this embodiment, the cooler  1   a , or its body, is in turn formed from several copper or metal layers which are joined to one another lying stacked one top of one another to the cooler  1   a . The metal layers  12   e  for the capillary areas  8  are made such that they are each provided on one surface side with several groove-like depressions  25  which extend in the lengthwise direction and which are produced by etching, stamping, or by machining which removes material or shavings, or in some other way. The depressions  25  each end in a continuous opening  26 , which is provided at a distance from a closed edge area. The metal layers  12   e  are then turned alternatingly to form the capillary areas  8 , and are placed unturned on top of one another such that each depression  25  of one layer  12   e  is added to one depression  25  of the adjacent layer  12   e  to form a channel, as is shown in  FIG. 24 . On the two ends, or areas  2  and  3 , these channels then empty according to  FIG. 25 , into spaces which are formed by openings  26  in the metal layers  12   e  and via which the channels are connected to the vapor channel  9 . 
     The metal layers  13   e , which form the vapor area, or the vapor structure, are made, for example, according to  FIG. 27 , similarly to layers  12   e , simply with depressions  27  of greater width and/or depth, or by the fact that according to  FIG. 28 , in the metal layers  13   e  there is one opening  28  with a large area each. 
       FIG. 29  shows a representation similar to  FIG. 24 . The cooler  1   a  is disclosed in which the metal layers  12   e  for forming the capillary structure, are not turned alternatingly, but are each in the same orientation so that the depressions  25  form especially fine channels. 
     In the above described embodiments it was assumed that the channels which form the capillary structures are free channels. It is also possible to place an auxiliary material which supports and/or causes a capillary effect in these or other structured or shaped channels, also in channels with large effective cross sections, for example, in the form of a powder, for example in the form of a powder consisting of at least one metal and/or metal oxide, for example copper and/or aluminum and/or copper oxide and/or aluminum oxide, and/or in the form of a powder consisting of at least one ceramic, and/or in the form of a powder from mixtures of the aforementioned substances, as is indicated by  29  in  FIG. 24 . 
     Copper is suited for the metal layers, the metal layers being joined superficially to one another using DCB technology or active soldering. Aluminum or an aluminum alloy is also suited for the metal layers. In this case, the metal layers are connected to one another by vacuum soldering. The thickness of the metal layers can roughly be between 100 and 1000 microns and the structure widths in the area are between 50 and 1000 microns. 
     REFERENCE NUMBER LIST 
     
         
           1 ,  1   a  cooler 
           2 ,  3  area 
           4 – 6  component 
           7  metal layer 
           7 ′ ceramic layer 
           8  capillary area 
           9  vapor channel area 
           10  cooling element 
           11  auxiliary cooler 
           12 ,  12   a ,  12   b  metal layer 
           12   c ,  12   d ,  12   e  metal layer 
           13 ,  13   a ,  13   b  metal layer 
           13   c ,  13   d ,  13   e  metal layer 
           14   a ,  14   b  slot 
           15   a ,  15   b  slot 
           16  posts 
           17  edge area 
           18  opening 
           19  crosspiece 
           20  island 
           21  opening 
           21 ′ structure 
           22  opening 
           23  passage 
           24  opening 
           24 ′ structure 
           25  depression 
           26  opening 
           27  depression 
           28  opening 
           29  auxiliary material