Abstract:
A heat sink absorbs heat from a chip or other component ( 32 ) and transfers the heat to a cooling fluid ( 36 ). The sink has a shaped part ( 22 ″) on which are formed at least one element ( 56 ″) for supplying cooling fluid ( 36 ) and at least one element ( 62 ″) for removing cooling fluid ( 36 ). The heat sink has a heat absorber ( 68 ″) with a heat-absorption side ( 112   u ) that absorbs heat during operation and a heat-transfer side ( 78 ) in contact with the cooling fluid ( 36 ) during operation. The absorber has a depression ( 118 ) in which are arranged a plurality of elongated thermally conductive elements ( 84 ″) which are each connected at a first end to the depression ( 118 ), and each have a free end ( 78 ) projecting away from the depression ( 118 ). Optionally, the heat sink can be coupled to a radiating or cooling unit ( 38 ), a fluid-circulating pump ( 39 ) and a fan ( 40 ) for directing air over the cooling unit, in order to quickly dissipate the heat transferred to the cooling fluid ( 36 ).

Description:
CROSS-REFERENCE  
       [0000]     to related German patent applications, the disclosures of which are incorporated by reference: DE 20 2004 005 241, filed 26 MAR. 2004; DE 20 2004 019 084, filed 27 NOV. 2004; and DE 20 2004 019 852.5, filed 15 DEC. 2004.  
       FIELD OF THE INVENTION  
       [0001]     The invention relates to a heat sink for absorbing and removing heat from a power component, e.g. a microprocessor, a microcontroller, an ASIC (Application-Specific Integrated Circuit), a laser, or the like. The invention is similarly suitable for the cooling of power components having a high heat flux density.  
       BACKGROUND  
       [0002]     Power electronics components that require cooling must not heat up above specific limit temperatures. Because reduced conductor widths also mean that the surface area of processors or other components is becoming ever smaller, the result is a sharp increase in the density of the heat flux to be discharged, i.e. the heat flux density. This makes it more difficult to apply the principle of so-called heat spreading, since regions inside a heat sink that are remote from the component that is to be cooled can contribute effectively to heat transfer only if their temperature is significantly higher than the temperature of the cooling fluid flowing past them. The flow velocities must also be sufficiently high, and the thermal boundary layers consequently sufficiently thin, to allow heat to be discharged effectively.  
       SUMMARY OF THE INVENTION  
       [0003]     It is an object of the invention to provide a novel heat sink.  
         [0004]     The invention provides a heat sink through which a cooling fluid flows during operation, and which offers a large surface area. In the heat sink, cold cooling fluid initially encounters regions having high absolute temperatures. Advantageously, it is possible largely to prevent mixing between cooling fluid that has already heated up and fresh, cold cooling fluid, before the latter encounters regions having the highest absolute temperatures. The regions having the highest absolute temperatures can also experience high incident flow velocities of the cooling fluid, so that turbulent flow, and consequently optimum heat transfer, can be obtained there.  
         [0005]     For that purpose, there are arranged, in a depression or cavity, a plurality of thermally conductive elements that project from the bottom of that depression into the path of the cooling fluid, so that the latter thereby flows around them during operation. This yields a corresponding enlargement of the heat-transferring surfaces. The thermally conductive elements and their interstices preferably have dimensions that can be produced using economical methods, e.g. by milling, electrodischarge machining methods, casting methods, forming, stamping, pressing, etc. It has also been found that heat transfer to the cooling fluid can be favorably influenced by a suitable surface treatment, preferably by sandblasting.  
         [0006]     The contour of the depression, which can also be referred to as a concave configuration, basin, or cavity, can be adapted to the requirements of a substrate that is to be cooled. A cavity in the shape of a part of a sphere (calotte), for example, can easily be manufactured by milling. Rotational conic sections can alternatively be used, for example a cavity in the shape of a rotational paraboloid or the like.  
         [0007]     The housing of a heat sink of this kind can comprise attachment capabilities, with which the housing can be mounted onto existing attachment points.  
         [0008]     The inlet element preferably has at its outlet a nozzle field that can comprise, for example, round nozzles or slit nozzles. The cooling fluid is accelerated as it flows through such a nozzle field. As a result, the cold cooling fluid has a high velocity when it encounters regions having high absolute temperatures.  
         [0009]     The nozzle field can also cause a portion of the cooling fluid to be deflected as it flows through the nozzle field, which can be considered a result of the so-called Coanda effect (named for Henry Coanda, 1886-1972). By exploiting this effect, portions of the cold cooling fluid can be directed in controlled fashion onto regions of the thermally conductive elements located farther out, thus improving heat transfer. 
     
    
     BRIEF FIGURE DESCRIPTION  
       [0010]     Further details and advantageous refinements of the invention are evident from the exemplifying embodiments, not to be understood as a limitation of the invention, that are described below and depicted in the drawings, in which:  
         [0011]      FIG. 1  is a section through a first embodiment of a heat sink according to the present invention, viewed along line I-I of  FIG. 4 ;  
         [0012]      FIG. 2  is a plan view looking in the direction of line II-II of  FIG. 1 ;  
         [0013]      FIG. 3  is a three-dimensional depiction analogous to  FIG. 1 , the section plane corresponding to  FIG. 1 ;  
         [0014]      FIG. 4  is a plan view looking in the direction of arrow IV of  FIG. 1 ;  
         [0015]      FIG. 5  is a depiction of the heat sink in the closed state;  
         [0016]      FIG. 6  is a depiction analogous to  FIG. 5 , but in which the four pressure springs and the associated bolts are depicted;  
         [0017]      FIG. 7  is a depiction analogous to  FIG. 1  in which the route of the cooling fluid flow is schematically indicated;  
         [0018]      FIG. 8  is a depiction analogous to  FIGS. 1, 3 , and  7  in which a substrate, e.g. the so-called “die” of a microprocessor, and the heat flux proceeding from it are schematically indicated;  
         [0019]      FIG. 9  is a three-dimensional depiction viewed from the lower side of the heat sink, cooling plate  68  having been removed;  
         [0020]      FIG. 10  is a greatly enlarged depiction of a nozzle plate having nine round nozzle openings  58 ;  
         [0021]      FIG. 11  is a depiction analogous to  FIG. 10  in which, in contrast to  FIG. 10 , five slit-like nozzle openings are used;  
         [0022]      FIG. 12  is a three-dimensional depiction of a variant of  FIG. 9  in which cooling plate  68  has likewise been removed;  
         [0023]      FIG. 13  is a depiction analogous to  FIG. 6 , but viewed in longitudinal section through the two front spikes  24  and  30 ;  
         [0024]      FIG. 14  is a section through a variant in which the section plane extends analogously to  FIG. 1 ;  
         [0025]      FIG. 15  is an enlarged sectional depiction of the central portion of a heat sink analogous to the depiction of  FIG. 14 , nozzle plate  59 ″ and cooling element  84 ″ not being depicted to scale because of their small dimensions;  
         [0026]      FIG. 16  is a very greatly enlarged section viewed in the direction of arrow XVI of  FIG. 17  in which the size relationships, among the dimensions of the parts depicted, correspond to those of an embodiment optimized by comparative tests;  
         [0027]      FIG. 17  is a section viewed along line XVII-XVII of  FIG. 16 ;  
         [0028]      FIG. 18  is an enlarged depiction of detail XVIII of  FIG. 17 ;  
         [0029]      FIG. 19  is a three-dimensional depiction of the heat sink of  FIGS. 16 through 18 , viewed from the side of the cooling element and its retaining plate  114 ; and  
         [0030]      FIG. 20  is a plan view of the heat sink, approximately analogous to  FIG. 19 .  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]     As depicted e.g. in  FIG. 1  and  FIG. 3 , a preferred embodiment of a heat sink  20  according to the present invention has an upper part  22  that is manufactured as a shaped part from a suitable material, preferably as an injection-molded part from a plastic or a suitable metal. Upper part  22  here has four tube-like projections (“spikes”)  24 ,  26 ,  28 ,  30 , whose shape is best understood from  FIGS. 3 through 6  and  13  and which serve to press upper part  22  toward a substrate  32  to be cooled, which is indicated in  FIG. 8  with dashed lines. Substrate  32  can be, for example, the so-called “die” of a microcomputer (CPU) which usually has a square or rectangular shape, in which it generates over a small area a high thermal output that results in a corresponding heat flux, which is indicated symbolically by arrows  34  in  FIG. 8 .  
         [0032]     This heat flux  34  must be absorbed by heat sink  20  and transferred via a cooling fluid  36  ( FIGS. 1 and 7 ) to a cooling unit  38  ( FIG. 7 ) of arbitrary design, where it is discharged to the ambient air e.g. by means of a fan  40  that is equipped with a motor  42 , as indicated in  FIG. 7 . Cooling unit  38  can advantageously contain a circulation pump  39  for cooling liquid  36 .  
         [0033]     Cooling unit  38 , the nature of cooling fluid  36 , and the further manner in which heat is removed (whether via air or a different fluid) are not part of the present invention and are therefore indicated here only to the extent that appears useful for an understanding of the invention and its context.  
         [0034]     Upper part  22  ( FIGS. 3-6 ) has at the bottom a cylindrical recess  46  ( FIG. 9 ) in a downwardly projecting extension  48 . Recess  46  is open toward the bottom and is delimited toward the top by lower side  50  of upper part  22 . Located on this lower side  50  is a downwardly projecting tube-like protrusion  52  that, in plan view from below, can have the shape of a ring or tube (cf.  FIG. 9 ), and is arranged approximately concentrically with nozzle field  59  at outlet  54  of a supply fitting  56  for cooling fluid  36 . Nozzle field  59 , e.g. in the form of nine holes  58  as depicted in  FIGS. 4, 9 , and  10 , is arranged in the region of outlet opening  54 .  
         [0035]     As  FIG. 9  shows, protrusion  52  can advantageously have, on its inner side and on its side facing away from an outlet opening  61 , a bevel  53  that preferably continuously decreases toward that outlet opening  61  in the manner depicted and that extends, in this example, over approximately three-quarters of the circumference of protrusion  52 . The result is that the flow resistance constituted by protrusion  52  is not the same in all directions, but rather increases toward opening  61 .  
         [0036]     At its left (in  FIG. 1 ) edge, recess  46  transitions via this outlet opening  61  into the outlet conduit  60  of an outlet fitting  62 . The heated cooling fluid  64  flows through fitting  62  back to cooling unit  38  (cf.  FIG. 7 ).  
         [0037]      FIG. 6  schematically shows the manner of attachment of a heat sink  20  according to the present invention. The latter has four spikes  24 ,  26 ,  28 ,  30 , and into each of these a respective compression spring  25 ,  27 ,  29 ,  31  is inserted in such a way that it rests on an inwardly projecting flange  24   a ,  26   a ,  28   a ,  30   a , respectively, of the relevant spike (cf.  FIG. 13 ).  
         [0038]     According to  FIG. 6  and  FIG. 13 , a respective bolt  25   a ,  27   a ,  29   a ,  31   a  is inserted into each spring, and these bolts are screwed into a countermember (not depicted), thereby loading springs  25  through  31  with a predetermined force. Heat sink  20  is pressed with this force against die  32  ( FIG. 8 ) in order to achieve good thermal transfer and thereby good cooling of die  32 .  
         [0039]     Cylindrical opening  46  ( FIG. 1 ) has an annular groove  66  or at least an annular shoulder. A heat absorption part  68  ( FIG. 2 ) has a cylindrical periphery  70 , and located in this is an annular groove  72  ( FIG. 3 ) complementary to annular groove  66 . Located between annular grooves  66  and  72 , as depicted, is a sealing ring  74  that seals heat absorption part  68  against upper part  22 . Any desired sealing means can be used for this seal, as is self-evident to one skilled in the art. Also possible, where applicable, is a permanent join between upper part  22  and heat absorption part  68 , e.g. by adhesive bonding or welding.  
         [0040]     Part  68  is manufactured from a material having good thermal conductivity, e.g. copper, aluminum, or silver. The nature of the material used depends, inter alia, on the application and on requirements in terms of service life and operating reliability. As is evident from the various figures, in this example part  68  generally has the shape of a round plate having a flat lower side  76  and an upper side  78 , parallel thereto, into which is recessed a depression whose general three-dimensional contour corresponds to the shape of a trough or basin. Lower side  76  is precision-machined to produce optimum thermal contact with substrate  32 , a thermoconductive paste  80  usually being arranged between lower side  76  and substrate  32  in order to optimize heat transfer. Experiments have shown that, for high heat flux densities, the thickness of the bottom of part  68  should be as thin as is compatible with mechanical stability.  
         [0041]     The trough-shaped depression  82  is arranged so that, in use, its center is located substantially above the center of substrate  32 . Depression  82  here has approximately the shape of a part of a sphere or “calotte” but other shapes for this concave structure are also possible, e.g. a rotational paraboloid, or the shape of a flat bowl having a substantially flat bottom.  
         [0042]     As is best shown by  FIGS. 2 and 3 , columnar cooling elements or thermal conduction elements  84  project upward from the bottom of depression  82  as far as upper side  78  of heat absorption part  68 . Because of their needle-like appearance, these cooling elements  84  can also be referred to as “pins.” Conduits  86  are located between them, i.e. cooling elements  84  are preferably produced by the fact that corresponding conduits or channels  86  are recessed in crisscross fashion into upper side  78  of part  68 , as is clearly evident, from the depictions, to one skilled in the art. Cooling elements  84  are preferably roughened by sandblasting after they are produced, in order further to facilitate heat transfer at their surface.  
         [0043]     There are of course different ways to produce columnar cooling elements  84  of this kind, e.g. also by means of suitable electrodischarge machining tools, with which it is possible to achieve an irregular profile for conduits  86  and thereby to influence the flow conditions in a controlled manner so that heat discharge occurs in largely symmetrical and therefore optimized fashion.  
         [0044]     As already described, the depression  82  represents an enveloping body that is interrupted by pins  84 . In this embodiment, depression  82  ends before the cylindrical periphery  70  of cooling plate  68 , so that a flat rim segment  90  is created there. Together with lower side  50  of upper part  22 , cylindrical recess  46 , and protrusion  52 , it forms an annular conduit  92  that intersects at the left (in  FIG. 1 ) with outlet conduit  60 , since the center axis of outlet conduit  60  coincides approximately with the outer rim of conduit  92 , so that the heated cooling fluid  64 , which flows in an approximately radial direction out of conduits  86  ( FIG. 3 ) of part  68 , is collected in this annular conduit  92  and flows through it and through outlet opening  61  to outlet conduit  60 .  
         [0045]     As a result, heated cooling fluid  64  is directed around the central portion of cooling plate  68  and consequently cannot mix with cold cooling fluid  36  that is supplied through supply fitting  56  to the central portion (inside ring  52 ). There consequently exists, inside ring  52 , a zone with very cold cooling fluid  36  which serves to provide the most intense cooling of substrate  32  ( FIG. 8 ) at the point where it evolves the most heat. Outside ring  52 , mixing-in of heated cooling fluid  64  takes place in annular conduit  92 , and the heat removal there is consequently less intense.  
         [0046]      FIGS. 1, 3 ,  9 , and  14  through  16  show that a plate  59  having the previously described nozzle openings  58  is provided on the lower side of inlet conduit  54 . This plate  59  is also depicted in greatly enlarged fashion in  FIG. 10 , and constitutes a nozzle field.  
         [0047]     Different kinds of nozzles can, of course, be used.  FIG. 11 , for example, shows a nozzle field  59 ′ in which parallel slit-shaped nozzles  58 ′ are present.  
         [0048]     During operation, under specific flow conditions that are easy to ascertain empirically, nozzles  58 ,  58 ′ cause a constriction of the inflowing cooling fluid  36 . The latter flows more quickly as a result, and upon encountering cooling elements (pins)  84  brings about intense turbulence and consequently better heat transfer.  
         [0000]     Mode of Operation  
         [0049]     During operation, cooled cooling fluid  36  is supplied from cooling unit  38  to supply fitting  56  and sprayed at high velocity through nozzle field  59  ( FIGS. 3, 4 ,  7 ,  9 ,  10 ,  14  through  16 ) inside ring  52  onto heat absorption part  68 , preferably (as indicated in  FIG. 7 ) being spread out by the so-called Coanda effect and thereby causing homogeneous, turbulent cooling of this central region (inside ring  52 ). The Coanda effect occurs at the nozzles that are located at the edges of the nozzle field, for example the topmost and bottommost nozzles  58 ″ in  FIG. 16 .  
         [0050]     The cooling fluid flows outward through conduits  86  ( FIG. 2 ) in an approximately radial direction, since the annular stopper  52  rests on cooling elements  84  and therefore forces cooling fluid  36  to flow through conduits  86  (and not past them), also cooling the radially outer region  90  of heat absorption part  68 .  
         [0051]     From conduits  86 , heated cooling fluid  64  travels into annular conduit  92 , and through the latter via outlet opening  61  to outflow conduit  60  and back to cooling device  38  where it discharges its heat, for example, to the ambient air, as indicated by fan  40 .  
         [0052]     It should be noted that it is also possible to use as the cooling fluid, for example, a boiling cooling fluid which evaporates at a temperature that is below the maximum temperature of substrate  32  that is to be cooled.  
         [0053]     The trough-shaped depression  82  yields the additional advantage that heat sink  20  is insensitive to the slightly oblique positions that often occur in practical use, for example, in a computer; this is because, as indicated by arrows  34  in  FIG. 8 , a certain forced convection does occur in heat sink  20  and depends little on its position.  
         [0054]     What is obtained, by means of the present invention, is thus a heat sink  20  through which a cooling fluid flows, which offers a large surface area, and in which cold cooling fluid first encounters regions having high absolute temperatures. The invention prevents already-heated cooling fluid  64  from mixing with fresh, cold fluid  36 , before the latter encounters the regions having the highest absolute temperatures. This means, conversely, that already-heated fluid is withdrawn as quickly as possible from areas having the highest absolute temperatures. In addition, the regions having the highest absolute temperatures also experience an incident flow of cooling fluid  36  at high flow velocities.  
         [0055]     As one skilled in the art may gather from  FIGS. 1, 3 , and  4 , without ring  52 , the cooling fluid  36  that is supplied would flow in a direct path from inlet fitting  56  to outlet fitting  62  and intensively cool only the left portion of heat absorption part  68 , so that substrate  34  ( FIG. 8 ) would also be cooled more intensely on its left side than on its right.  
         [0056]     Ring  52 , acting as a stopper, counteracts this and forces cooling fluid  36  to flow in all directions and thereby to cool cooling plate  68  more homogeneously. If ring  52  has the same dimensions everywhere as depicted in  FIG. 1 , however, asymmetrical cooling can nevertheless occur because cooling fluid  36  always takes the path of least resistance, i.e. in  FIG. 1  from inflow  56  for the most part directly to the left to outlet  62 .  
         [0057]     For this reason, in  FIG. 9 , ring  52  is provided with bevel or chamfer  53 , which is greatest where it is located opposite to outlet opening  61 . This bevel  53  could also be arranged on the outer side of ring  52 . The bevel creates, for cooling fluid  36  that flows in via nozzles  58 , a relatively high flow resistance for a direct flow (labeled  90  in  FIG. 9 ) to outlet  61 , whereas the flow resistance for flows  92 ,  94 , which proceed via points having a large bevel  53 , is less. The result is that the cooling of part  68  ( FIG. 2 ) is altogether more homogeneous, i.e. that large temperature gradients in cooling plate  68  are avoided.  
         [0058]      FIG. 12  shows a variant of this. Here base  52 B of ring  52  is of solid configuration and has the same height h everywhere. Protrusions  100  of various lengths project upward in  FIG. 12  from this base  52 B in the manner depicted. They are separated from one another by valleys or conduits  98 . These conduits are labeled  98 L on the left in  FIG. 12 , and  98 R on the right in the vicinity of outlet opening  61 . It is thus evident that protrusions  100  are low on the left side in  FIG. 12 , and high on the right side.  
         [0059]     Protrusions  100  are so configured that they project, in  FIG. 2 , into interstices  86  between cooling elements  84  and act there, depending on their length, as orifices or restrictions of varying intensity. As a result, in  FIG. 12 , direct cooling fluid flow  102  from nozzle field  58  to outlet  61  is greatly restricted, whereas cooling fluid flows  104 ,  106  from the left side in  FIG. 12  to outlet  61  are restricted only slightly or not at all, so that overall, cooling plate  68  is as a whole cooled symmetrically and not one-sidedly.  
         [0060]     As described with reference to  FIG. 6 , housing  22  has attachment capabilities with which heat sink  20  can be mounted onto previously existing attachment points that are located in the system of which component  32  to be cooled is a part. Attachment to the base of substrate  32 , to the associated main circuit board, or to another component, using so-called “clip” technology, is alternatively possible.  
         [0061]     A heat sink  20  of this kind can be manufactured on the whole very inexpensively, since upper housing part  22  with its complicated shape can be manufactured inexpensively as an injection-molded part, and can be optimized for the requirements of a specific processor type. Pins  84  of cooling plate  68 , and their interstices  86 , preferably have dimensions that can be manufactured using economical production methods, e.g. a width for pins  84  on the order of less than 2 mm. The same is true analogously for the arrangement according to  FIG. 12 . With reference to  FIG. 16 , dimensions will be described below that may be regarded as optimum, based on present knowledge.  
         [0062]     The inserted cooling plate  68  has a shoulder or annular groove  72  that makes available some of the sealing edges for fluid-tight sealing between upper part  22  and cooling plate  68 . At least one other sealing edge (annular groove  66 ) is made available by upper part  22 . Upper part  22  has at least one inlet fitting  56  and at least one outlet fitting  62 . Inlet fitting  56  is located at the center, and outlet fitting  62  intersects with its center axis approximately the outer rim of annular conduit  92 . The interpenetration of the elements resulting therefrom yields a rectangular outlet  61  out of annular conduit  92 , and this outlet has a large cross section and consequently a low flow resistance. The corner edges of the interpenetration can be rounded off for further reduction of the flow resistance.  
         [0063]     Inlet fitting  56  preferably has, at its inner end, a diaphragm  59 , in which round nozzles  58  or slit-shaped nozzles  58 ′ can be provided, so as to define a nozzle field. Cooling fluid  36  is accelerated as it flows through this nozzle field  59  or  59 ′, and the fluid stream is in fact constricted even further after exiting from the nozzle field (Coanda effect), resulting in a further increase in flow velocity. Cold cooling fluid  36  thus has a high velocity when it encounters regions having high absolute temperatures. In addition, the surfaces are enlarged in a balanced relationship by way of pins  84 . Corresponding ribs could also be used instead of pins  84 ; this is not depicted.  
         [0064]     Ring  52  forces cooling fluid  36  to flow through at the foot of pins  84 , and only small flow resistances are subsequently imposed on the fluid in outer annular conduit  92 , so that backflow and mixing with cold cooling fluid  36  is made additionally difficult. Upper part  22  can also possess, for this purpose, an outlet cross section that is larger than the inlet cross section.  
         [0065]      FIG. 13  is a depiction analogous to  FIG. 6  but in section. The reference characters are the same as in  FIG. 6 . It is evident that parts  25   a ,  31   a  have internal threads  25   a ′,  31   a ′, and that springs  25  and  31  are loaded when parts  25   a ,  31   a  are pulled downward, for example by screw threads (not shown) that serve for attachment to a circuit board.  
         [0066]      FIG. 14  shows a variant that is constructed very similarly to  FIG. 1  but, in contrast to  FIG. 1 , has two outflow fittings  62 ,  63 .  
         [0067]     The left half of  FIG. 14  corresponds to the left half of  FIG. 1 , likewise cooling or heat absorption plate  68 ; the same reference characters are therefore used for these parts. An outflow fitting is located on that side, as in  FIG. 1 .  
         [0068]     Additionally present in the right half of  FIG. 14  is a second outflow fitting  63  that is located symmetrically opposite first outflow fitting  62 . Cooling fluid  36  thus flows in centrally through inflow fitting  56 , flows through nozzle field  59  onto impact plate  68  where it absorbs heat from the latter, and then splits, i.e. one half flows to the left to outflow fitting  62 , and the other half to the right to outflow fitting  63 . A flow  64 ′ therefore exists in fitting  62  and a flow  64 ″ in fitting  63 , and these fluid flows are then combined into one outflow  64  by means of connections that are indicated merely schematically.  
         [0069]     The advantage in the context of  FIG. 14  is that cooling plate  68  is cooled more symmetrically than in the context of  FIG. 1  since, in the context of  FIG. 1 , the left half can be cooled somewhat better than the right because of the geometry of the arrangement.  
         [0070]     In  FIG. 14 , as in  FIG. 1 , ring  52  is used to prevent mixing of cold fluid  36  with already-heated fluid  64 ′,  64 ″, and this ring can once again be formed with bevels or protrusions which are so configured that a slightly elevated flow resistance for the cooling fluid is created in the vicinity of outlet fittings  62 ,  63 .  
         [0071]      FIG. 16  shows a portion of a practical exemplifying embodiment of the invention that has proven particularly successful in comparative tests. This depiction corresponds to section XVI-XVI of  FIG. 15 , but contains details that cannot be graphically depicted in  FIG. 15 .  
         [0072]     The lower (in  FIG. 16 ) portion of nozzle field  59 ″ is shown cut away in order to improve comprehension of the location and size, in relation to the location of openings  58 ″ of nozzle field  59 ″, of cooling elements  84 ″ that are used there. The location of openings  58 ″ in the lower part of  FIG. 16  is indicated by dot-dash lines.  
         [0073]     As  FIG. 15  schematically shows, openings  58 ″ are arranged, in relation to the columnar cooling elements  84 ″ and conduits  82 ″ produced between them, so that a stream  36 ″ of cooling liquid  36  that exits from an opening  58 ″ during operation is aimed at the intersection of a conduit  82 ″ h  extending horizontally in  FIG. 16  and a conduit  82 ″ v  extending vertically in  FIG. 16 . As depicted in  FIG. 16 , a conduit crossing  82 ″ cr  of this kind is therefore visible through each nozzle opening  58 ″, i.e. a stream  36 ″ is aimed at the deepest point of a conduit  82 ″, namely the point at which the temperature generated by electronic component  32  ( FIG. 15 ) is highest.  
         [0074]     The arrangement of nozzles  58 ″ is selected so that heat is removed from cooling elements  84 ″ as homogeneously as possible. In  FIG. 16 , a central vertical row  96  of four evenly distributed nozzle openings  58 ″ is provided and, parallel thereto but at a lateral offset, a left row  98  and a right row  100  each having three nozzles  58 ″. Good results in tests have been obtained with this arrangement. Dimensions a, d, D, h, and L are noted in  FIGS. 15 and 16 ; d denotes the (usually identical) inside widths of conduits  82 ″ h  and  82 ″ v . The cross section of cooling elements  84 ″ is preferably approximately square, and one such square has a side length L. Tests have shown that the cross section of cooling elements  84 ,  84 ′,  84 ″ should be approximately proportional to width d of conduits  82 ″, and that the best results are obtained when 
 
 L =(1.4 . . . 2.0)* d   (1), 
 
 where L and d are measured in mm. For a dimension d=0.3 mm, for example, a value L of 0.4 to 0.6 mm has proven particularly favorable, i.e. a cross section of approximately 0.1 to approximately 0.4 mm 2 . 
 
         [0075]     Cooling elements  84 ″ preferably have a square cross section for ease of manufacture. If a different cross section is selected, e.g. a cylindrical cross section, the average cross section is taken as the starting point, i.e. the weighted average of the cross sections of the individual cooling elements, referred to as Q. This is usually in the range from 0.1 to 0.4 mm 2 . The relationship between this value and the inside width d of conduits  82 ″ between cooling elements  84 ″ is preferably constrained as follows: 
 
 d =(0.25 . . . 0.5)* exp (0.5 *lnQ )  (2), 
 
 where d is measured in mm and Q in mm 2 , and lnQ is the natural logarithm of Q. 
 
         [0076]     This therefore yields, based on present knowledge, a preferred value range for the value d when Q is known.  
         [0077]     As the size of an electronic power component  32  to be cooled decreases, its heat flux density usually increases, and it is then necessary to adapt the size of cooling elements  84 ″, i.e. parts  84 ″ become even smaller and, according to equation (1), the width of conduits  82 ″ also becomes even smaller. Diameter D of nozzles  58 ″ also decreases correspondingly in this case.  
         [0078]     Round nozzles  58 ″ have a preferred diameter D of approximately 1 to approximately 1.2 mm. The distance h noted in  FIG. 15  between nozzle plate  59  and the bottom of conduits  82 ″ at their deepest point has, based on present knowledge, an optimum when the following is true: 
 
 h =(2 . . . 3)* D   ( 3 ), 
 
 i.e. for optimum results, this distance h is approximately two to three times the diameter D of a nozzle  58 ″. This distance h is in any case greater than D. (Diameter D is normally approximately the same for all nozzles  58 ″, in the interest of simple manufacture. The depiction in  FIG. 15  is schematic, and therefore cannot show these dimensional relationships, to which reference is made.) 
 
         [0079]     The preferred vertical center-to-center spacing a between two adjacent nozzles is obtained from the dimensions indicated, i.e. 
 
 a=n*L+n*d   (4) 
 
 where n=2, 3, . . . 
 
         [0080]     If n=2 (as depicted), then 
 
 a= 2*0.6+2*0.3=1.8  mm   (5). 
 
 In comparative tests, these dimensions resulted in very good heat removal from component  32  indicated schematically in  FIG. 15 . A structure of this kind is particularly well suited for components  32  having small dimensions and a high heat flux density, e.g. for processors. 
 
         [0081]     Each two adjacent nozzles  58 ″ of center row  96  form an isosceles triangle with one adjacent nozzle of row  98  or row  100 , the length s of the sides being 
 
 s= 1.12 *a   (6). 
 
         [0082]     In comparative tests, an arrangement of this kind has proven effective for removing the quantity of heat that is produced in such a way that local temperature peaks do not occur.  
         [0083]      FIG. 17  shows heat sink  20 ″ of  FIG. 16  in the assembled state. It has an upper part  22 ″ (shaped part) made of plastic, on which are provided an inlet fitting  56 ″ in the center and an outlet fitting  62 ″ laterally, the latter leading obliquely upward at an angle alpha of preferably approximately 70 degrees.  
         [0084]     Located at the lower (in  FIG. 17 ) end of inlet  56 ″ is nozzle plate  59 ″, whose shape is most apparent from  FIG. 16 . Upper part  22 ″ has at the bottom a cylindrical recess  46 ″ in which heat absorption part  68 ″, sealed by means of an O-ring  74 ″, is arranged.  
         [0085]     Heat absorption part  68 ″ preferably has approximately the shape of a disk, and has on its lower side a cylindrical protrusion  110  on which is located a rectangular protrusion  112  that, during use, rests with a surface  112   u  against a heat-emitting part, e.g. against an IC or a microprocessor, as depicted in  FIG. 8  for heat-emitting component  32 .  
         [0086]     Heat absorption part  68 ″ is retained by a supporting part, here in the shape of a retaining plate  114  ( FIGS. 17, 19 , and  20 ) made of steel or the like. Retaining plate  114  has, at its center, a hole  115  through which protrusion  110  extends. For clarification, those parts that belong to heat absorption part  68 ″ are highlighted in gray in  FIG. 20 . The configuration is very clearly evident from  FIG. 19 . Retaining plate  114  is retained on upper part  22 ″ by four bolts  116 .  
         [0087]     Upper part  22 ″ has, at its four corners, four attachment holes  117 , each of which has a hollow-cylindrical extension  117 A that, as shown in  FIG. 17 , is elevated above bolts  116 . Holes  117  are located on radial enlargements  119  of housing part  22 ″ that project outward from the latter in the form of lugs, as shown best by  FIGS. 19 and 20 .  
         [0088]     Heat absorption part  68 ″ is thereby largely relieved of load-bearing functions, and in its central part, i.e. in the region of rectangular protrusion  112 , can be very thin, having for example, as depicted, a thickness of less than 1 mm in the central region; this is very advantageous in terms of good cooling, since excellent heat transfer is obtained as a result.  
         [0089]     Heat absorption part  68 ″ has, on its upper (in  FIGS. 17-18 ) side, a basin- or trough-shaped recess  118 , in the form of a spherical cavity or “calotte” in the present exemplifying embodiment. Upper part  22 ″ has an annular recess  120  that is located opposite the outer portion of recess  118  and forms, together with that portion, an annular conduit  122  whose cross section is approximately lens-shaped and which is in direct liquid communication with outflow fitting  62 ″.  
         [0090]     Located at the deepest point of spherical cavity  118  in  FIG. 18  are cooling elements  84 ″, which are shown greatly enlarged in  FIGS. 16 and 18 . Some of cooling elements  84 ″ are located, in  FIG. 18 , directly beneath nozzle plate  59 ″. As shown in  FIG. 18 , the distance from nozzle plate  59 ″ to bottom  82 ″ of spherical cavity  118  has a value h whose optimum magnitude is obtained from equation (3) and is preferably less than 5 mm. In the exemplifying embodiment, h has an optimized value of approximately 2.5 mm.  
         [0091]     Longitudinal axes  126  of nozzles  58 ″ preferably extend through the center planes of valleys  82 ″ h  (cf.  FIGS. 16 and 18 ). This allows particularly good cooling, since the cooling fluid can then flow from above directly into these valleys and, at the bottom of them, can effect impact cooling with a high heat transfer coefficient.  
         [0092]     Radially outside those cooling elements  84 ″ that are located directly beneath nozzle plate  59 ″, an annular protrusion  128  of upper part  22 ″ is in contact against cooling elements  84 ″ there, so that during operation, the cooling fluid cannot flow away over the cooling elements  84 ″ there but instead must flow between them through valleys  82 ″. This prevents cold and hot cooling fluid from mixing, which would reduce the cooling efficiency.  
         [0093]     Located radially outside annular protrusion  128  are cooling elements  84 ″ x  whose height increases toward the outside, additionally improving heat transfer there.  
         [0094]     As is particularly apparent from  FIG. 17 , annular conduit  122  has a large cross section, so that the flow resistance for the cooling fluid that flows in through inflow  56 ″ in the direction of arrow  36  ( FIG. 17 ) differs little over all the cardinal directions. Cooling at the center, i.e. beneath nozzle plate  59 ″, is particularly good, since the cooling fluid is coldest there and flows along lines  126  ( FIG. 18 ) directly between cooling elements  84 ″ and directly cools the bottom of spherical cavity  118 , which optimizes cooling at the center of the object ( 32  in  FIG. 15 ) that is to be cooled.  
         [0095]     Reinforcing ribs  130  are provided on the upper side of upper part  22 ″, partly in order to enhance the mechanical stiffness of upper part  22 ″ and partly to give it a pleasant appearance that identifies its origin.  
         [0096]     As  FIG. 17  shows particularly well, spherical cavity  118  extends both into cylindrical protrusion  110  and into rectangular protrusion  112 , i.e. spherical cavity  118  extends through opening  115  of plate  114  to a point very close to the lower (in  FIGS. 17 and 18 ) end surface  112   u  of protrusion  112 ; this is highly advantageous in terms of heat transfer from this protrusion  112  to the cooling fluid in spherical cavity  118 .  
         [0097]     Many variants and modifications are possible within the scope of the present invention. For example, the cooling fluid can also flow through the heat sink in the opposite direction, for example when substrate  34  to be cooled requires more intense cooling in its outer regions than in its central regions. These and similar modifications are embraced within the capabilities of one skilled in the art.