Multi-component cooling element

Abstract

The invention relates to a micro cooling element (1) with a mounting surface (2) for a component to be cooled, in particular a semiconductor component, which has within it a micro cooling structure (3) which is connected by connection channels (4) to at least one inflow opening (4a) and at least one outflow opening (4b) by means of which a cooling medium can be supplied to the micro cooling structure (3) or be discharged from the latter, and which is characterized in that it is formed from at least two different powdery and/or liquid, in particular metallic and/or ceramic, materials or material mixtures (10) while maintaining a monolithic structure, wherein regions of different stresses (I, II) of the micro cooling element (1) are built by a powdery and/or liquid, in particular metallic and/or ceramic materials or material mixtures (10) being adapted to the stress respectively. The invention further relates to an apparatus and a process for producing a micro cooling element according to the invention.

Claims

1. A micro cooling element comprising: a top surface and a bottom surface, the top surface defining a mounting area for receiving a component to be cooled; and a micro cooling structure disposed beneath the mounting area and between the top surface and the bottom surface, the micro cooling structure including a channel having an inlet and an outlet for a cooling medium to flow therethrough, the inlet and the outlet being formed through the top surface; wherein the micro cooling element is formed as a monolithic structure having a first region and a second region, the first region being a thermally stressed area and comprising one of a metallic and a ceramic material, the second region being a mechanically stressed area and comprising one of a metallic and a ceramic material different than the one of the metallic and ceramic material of the first region.

2. The micro cooling element of claim 1, wherein the component is a semiconductor.

3. The micro cooling element according to claim 1, wherein the first region comprises chromium or nickel and the second region comprises titanium.

4. The micro cooling element according to claim 1, wherein the micro cooling element includes a cross over region between the first and second regions in which a mix ratio is continuously changed such that the content of the one of the metallic and ceramic materials of the first region decreases and the content of the one of the metallic and ceramic materials of the second region increases from the first region to the second region.

5. The micro cooling element according to claim 4, wherein a mediator material is applied in the cross over region.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a diagrammatic illustration of a micro cooling element according to the invention;

(2) FIG. 2 is a diagrammatic illustration of an apparatus for producing a component by means of selective laser sintering.

DETAILED DESCRIPTION

(3) FIG. 1 diagrammatically shows a micro cooling element according to the invention which can roughly be divided into two regions I and II.

(4) In region I a mounting surface 2 for a component to be cooled, such as for example a semiconductor element, is formed on the upper side of the micro cooling element 1 in its front face side end region. Disposed beneath the mounting surface 2 within the micro cooling element 1 is a micro cooling structure 3 which by means of connection channels 4 with inflow and outflow openings 4a, 4b located in region II forms a cooling circuit through which a cooling medium, such as for example deionised water, can flow for cooling purposes. In region I, in particular in the region of the micro cooling structure 3, the requirement for optimal heat exchange comes to the fore. Correspondingly, in this region the most erosion-free material possible, expansion adapted and with good cooling properties is desirable. An example of this type of material is chromium. However, other materials such as nickel, for example, are also possible. Material properties, such as stability for example, play a less important role at this point since only small mechanical stresses occur and so are negligible here.

(5) In region II, however, it is precisely in the region of the water inlet and the water outlet that the mechanical stresses are very high. Relatively high mechanical stresses also occur in the region of the supply and discharge of the cooling water. Therefore in this region a material with a high level of resistance against electrocorrosion and with very good mechanical strength is desirable. These requirements are fulfilled by the use of titanium, for example. Materials such as stainless steel for example can also be used here. The heat conductivity and expansion adaptation which are poorer in relation to chromium are of lesser significance in this region since this region is not involved in the direct heat exchange with the component to be cooled.

(6) Between region I and region II a crossover region C is provided in which, as viewed from region I to region II, the mix ratio is continuously changed such that the chromium content decreases and the titanium content correspondingly increases the more one passes from region I towards region II. By means of the continuous mixture of the two materials a homogeneous crossover is created with which it is possible to combine the materials which can only be combined directly with one another with difficulty. In the event of incompatibility, it is if appropriate possible to incorporate a so-called mediator component between the materials.

(7) Beneath the diagrammatically illustrated micro cooling element 1 the change in the chromium and titanium content in the respective regions of the cooling element is shown diagrammatically as an illustration. As a result, one obtains a cooling element which in the region of the heat exchange is erosion-free, expansion adapted and provided with good cooling properties. In the region of the supply and discharge the cooling element has outstanding resistance against electrocorrosion and very good mechanical strength.

(8) As already mentioned above, the micro cooling element 1 is produced by means of selective laser melting. With this process the component to be produced is first of all separated virtually into sections along the Z plane of the component and the resulting CAD data in the X and Y direction are inputted into a control unit. Furthermore the component is analysed with regard to in which regions which properties are to be prioritised so as to make a material choice accordingly. The micro cooling element 1 according to the invention can now be divided into two requirement regions. As described above, region I relates to the part of the cooling element 1 for which the evacuation of heat is essential since the semiconductor to be cooled is to be fitted in this region. Therefore, the essential properties required of the material here are heat conductivity, expansion adaptation to the component to be cooled and erosion resistance. Electrocorrosion and mechanical stress only play a less important role here. The connection points 4a, 4b for the water supply are located in region II. Since the cooling element 1 is also a component part of the electrical contacting, the focus here is mechanical stability and resistance against electrocorrosion. Requirements such as heat conductivity and expansion adaptation are less important material requirements here.

(9) For the construction of the micro cooling element 1 according to the invention, upon the basis of the preceding analysis a material with good heat conductivity and heat expansion coefficients adapted to the component to be cooled is first of all selected in order to form region I, and this is introduced into a processing region of a processing chamber 6 by means of a feeder 5 shown in FIG. 2 and then distributed using a levelling device 7, free from binding agents and fluxing agents, and with a pre-specified layer height which corresponds to a penetration depth of a laser beam 8 used in the process, over a base plate 9 which can be lowered in the Z direction in the processing chamber 6. In an inert gas atmosphere the laser beam 8 corresponding to the CAD data inputted into the control unit is moved over the powder layer 10 such that the metallic material powder 10 is heated locally to the melting temperature and totally fused over its whole layer height at the respective striking point of the laser beam 8. Next the base plate 9 is lowered by an amount which corresponds to the layer thickness of the fused metal powder 10. A further layer of the metallic material powder 10 is then applied to the already present metal powder layer 10 treated with laser radiation and the layer thickness of which in turn corresponds to the penetration depth of the laser beam 8.

(10) Supply of the material powder 10 is implemented by means of the feeder 5 according to the invention in which in this exemplary embodiment three material chambers 11 are formed. The one material chamber 11 is filled here with chromium Cr for supply of region I, and the other with titanium Ti for region II, and the third material chamber 11 is provided with a chromium/titanium mixture.

(11) On the outlet side the material chambers 11 are respectively provided with a dosing unit 12 by means of which the mix ratio and the supply quantity of the individual materials 10 can be set simply by opening and closing the opening on the outlet side of the material chamber 11, the dosing units 12 for the supply of the material to the processing chamber 6 freeing the material outlet of the material chamber 11, by means of which the material powder 10 continues to move out of the material chambers 11 due to the force of gravity until the dosing units 12 close once again. In this embodiment the dosing units 12 are computer-controlled for the setting of a pre-specifiable mix ratio, and this results in very accurate setting of the composition of the material mixture 10.

(12) In order to obtain the most homogeneous possible mixing of the material mixture a mixing chamber 13, in which the sample mixture can be mixed intensively once again by means of a worm 14 prior to supply to the processing chamber, is located downstream of the dosing units 12. In order to create the most homogeneous possible crossover zone between the two different materials, the mix ratio of the materials chromium and titanium is changed step by step or continuously from layer application to layer application before supply to the processing region in the processing chamber 6. In this exemplary embodiment the feeder 5 has a further material chamber 11 which in this exemplary embodiment is provided with a chromium/titanium material mixture, but in the case of materials which are totally incompatible with one another can also be provided with a mediator component (not shown) which can then be incorporated in the crossover region for combining the materials. It is also conceivable to fill the third material chamber with a material mixture optimal for the crossover zone with a further material different from chromium and titanium which can be produced in the forefield outside of the apparatus. This is advantageous if the crossover region also requires a constant mix ratio or the mediator material is only a very small portion in an only very small field of application.

(13) In order to form the workpiece the laser beam 8 is now moved in a number of traces over the pre-specified region of the material layers 10 so that each subsequent trace of the laser beam at least partially overlaps the previous trace. By means of the overlapping the fused material of the powder 10 and the fused material of the adjacent, already solidified, solid contour which was previously fused, and beneath the subsequently applied powder layer, is fused to form a common molten pool. The molten pool then undergoes a metal melting alliance. In this way, after solidification a homogeneous grid structure with a high level of strength and density and without any grooves or other crossover points is formed.

(14) If the micro cooling element 1 with the two main regions I, II, was totally constructed in this way, it is then only necessary to remove the powder remaining in the inner structures. This can be achieved, for example, by means of compressed air or by the micro cooling element then being flushed with pressurised deionised water.

(15) Since by means of this process the most different of metallic material powders can also be processed in combination, in addition to the combination of metallic materials, a combination of metallic and ceramic materials is also conceivable. The use of liquid metallic or ceramic materials, if required also in combination with powdery materials, is also conceivable.