EP1992015A2

EP1992015A2 - Composite material and method for production thereof

Info

Publication number: EP1992015A2
Application number: EP07701341A
Authority: EP
Inventors: Erich Neubauer; Paul Angerer; Réne NAGEL
Original assignee: Austrian Research Centers GmbH ARC
Current assignee: AIT Austrian Institute of Technology GmbH
Priority date: 2006-03-09
Filing date: 2007-02-28
Publication date: 2008-11-19
Also published as: WO2007101282A3; AT503270A1; WO2007101282A2; AT503270B1

Abstract

The invention relates to a material, comprising: a metal matrix A, the material of which has a thermal expansion coefficient in the range of 16 to 20 ppm/K in at least one direction, formed from copper or a copper alloy and representing 10 to 75 vol. % of the material, at least one metal or ceramic filler B, with a thermal expansion coefficient in the range 4 to 6 ppm/K in at least one direction, formed from Cu2O and/or Al2O3 and/or AlN and/or Mo and/or Cr and/or W and/or B and/or Ta, present in the material in an amount of 1 to 40 vol. % and a least one filler C based on carbon, characterised by a thermal expansion coefficient of - 2 to +2 ppm/K in at least one direction, having high thermal conductivity and being formed from graphite and/or carbon fibres and/or carbon nanofibres and/or carbon nanotubes and/or diamond and present in an amount of 5 to 65 vol. %.

Description

Composite material and process for its production

The invention relates to a material according to the preamble of claim 1, especially a composite material composed of several components and thus offers the possibility of the coefficient of thermal expansion in a range of 4 to 12 ppm / K by the choice of composition and by the manufacturing conditions adjust. In addition, the material should be characterized by a high thermal conductivity and thermal conductivity.

The invention further relates to the production process for such a material using rapid sintering processes or a process according to the preamble of claim 15.

In many cases, more and more growing demands on materials used to cool electronic components require tailored material properties. In particular, a high thermal conductivity or thermal conductivity is required together with a low expansion coefficient. A low coefficient of thermal expansion is required because Si or SiC based chips are usually "bonded" to an AIN or Al 2 O 3 substrate, and thermal cycling leads to stress between the substrate and the cooling plate In addition, the material should have a high thermal conductivity or thermal conductivity, According to the invention, a material of the type mentioned above is characterized by the features recited in the characterizing part of claim 1 A method of the type mentioned above is characterized according to the invention with the features of claim 15.

The material according to the invention comprises a matrix A with a high thermal conductivity or thermal diffusivity: here, copper comes into consideration or copper-based materials or alloys. A pure copper matrix or a copper-based matrix has a coefficient of expansion in the range of 16-20 ppm / K. For this reason, the matrix content should be kept as low as possible.

The material further comprises a metallic and / or ceramic filler B, with the thermal expansion in the range of 4 to 6 ppm / K, which either has a thermal conductivity of about 50-200 W / mK (in the case of the metallic

Filler) and / or the thermal conductivity of the matrix A is not disproportionately deteriorated (in the case of a ceramic filler).

The material further comprises a thermally highly conductive filler C, which has a low coefficient of thermal expansion. Here is a filler on Carbon base selected, such as graphite, carbon fibers, carbon / nanofibers, carbon nanotubes and / or diamond. All of these fillers have a coefficient of expansion (at least in one spatial direction) that ranges from about -2 to +2 ppm / K. The filler C may optionally be coated with a functional layer D, which allows a good connection to the matrix A and / or the filler B.

Finally, it can be provided that in the material in addition to the material of the metal matrix A and the fillers B and C amorphous and / or intermediate substances or compounds in the extent of <5 vol,% are included. To ensure a better cohesion of the matrix, the

Features of claim 2 are provided.

The properties of the material are improved if a homogeneous distribution of the fillers B and C in the metal matrix A is present in the material.

For certain applications, it is advantageous if the features of claims 3 to 7 are met.

The material according to the invention obtains an advantageous microstructure by the features of claims 8 to 11. Good strength properties are achieved with the features of claim 12.

An inventive material is advantageously characterized in that the material has an expansion coefficient of 4 to 12 (.10 ^"6 K ^'1 ) in a temperature range of 2O ⁰ C to 5O ⁰ C.

In order to achieve a uniform structure without interference, the features of claims 17 to 19 are advantageous.

Good structural properties arise with the features of claims 20 and 21.

The material properties of the material are optimized when the features of claims 25 and 26 are provided.

The figures serve to illustrate the invention. Show it:

Figure 1: Basic structure of the composite material: Metallic matrix filler A, with metallic or ceramic fillers B and thermally highly conductive carbon-based filler C. Optionally, the filler C may be coated with a coating D.

Figure 2: Theoretical dependence of the thermal

Coefficient of expansion (calculated by mixing rule) of a composite consists of matrix A and filler C as a function of the volume fraction of filler C. The

Matrix A consists of pure copper or a copper alloy. To one Coefficient of expansion below 8 ppm / K, a volume fraction of 55 vol.% Filler C is provided.

Figure 3: Theoretical dependence of the thermal expansion coefficient of a composite material (calculated by mixing rule) consists of matrix A with 50 vol.% Filler C with variation of the volume content of filler B. The matrix A consists of pure copper or a copper alloy. The filler B is characterized by a thermal expansion coefficient of 4 ppm / K.

Figure 4: Thermal expansion coefficient of a Cu-Cu2O-diamond composite as a function of temperature

Figure 5: XRD measurement on Cu-Cu2O-diamond composite material

Figure 6: XRD measurement on Cu-Cu2O carbon fiber composite material

Figure 7; Thermal expansion coefficient of various composites with a copper matrix and diamond as filler C or Mo, Cr or Cu2O as filler B

Figure 1 shows the structure of the material.

A direct mixture of copper or copper-based matrices with the carbon-based filler poses three problems: a) Generally, a poor thermal transition between copper and carbon is observed. This is partly due to the lack of

Wetting of carbon by copper or also by the different heat conduction mechanisms (metal = electron conductor while, for example, diamond conducts heat via phonons) b) The strong difference between the coefficient of thermal expansion of copper or copper based

Matrices and that of the carbon-based filler causes thermal stress to interfacial stresses. In addition, a pure combination of copper-based matrix with carbon-based fillers causes problems in the following ways, as shown in Figure 2: To obtain a coefficient of expansion of 8 ppm / K or 7 ppm / K or less, a filler content of at least 55 vol.% or 65 vol.% required. This is on the one hand manufacturing technology difficult (pores, sinterability, ..), but also leads to a subsequent processing of the material is not easy. Likewise, the suffers

Surface quality below. Figure 2 shows the expansion properties as a function of filler content C. c) Especially in the case of diamond must in the selection of the

Process parameters for consolidation are handled very carefully. Diamond transforms at temperatures of 900 to 1000 ° C

Graphite around. In order to obtain a compact, dense body, the sintering conditions must be carefully selected.

In order to obtain a material with a thermal expansion of 4 to 12 ppm / K, the following procedure is advantageously carried out as follows: a) In order to obtain a corresponding heat transfer between the metallic matrix and the carbon-based filler, coated fillers can be used. The fillers are made with a layer of one

Coefficient of low expansion material with good affinity to the carbon filler such as Mo, W, Cr, Ta, AIN coated. The thickness of the coating may be in the range of a few 10 nm to a few 100 nm, or the proportion of the total material at about 0.1 to 5 vol.%. Optionally, an improvement in the thermal transition but also by skillful

Selection of a metallic filler B can be achieved. b) In order to achieve a coefficient of thermal expansion in the composite that is as close as possible to that of Al 2 O 3 or AlN, the copper-based matrix with an expansion coefficient of 16-20 ppm / K can be modified accordingly, so that the expansion coefficient is reduced.

Suitable components for reducing the coefficient of expansion of the copper-based matrix are: ceramic fillers which have a low coefficient of thermal expansion in the range of 4 to 6 ppm / K and which do not disproportionately deteriorate (as would be the case with Ti, for example) cause thermal conductivity. By this is meant that the ceramic filler does not significantly affect the thermal conductivity of the copper-based matrix (through an approximate linear relationship corresponding to the

Mixture rule) deteriorates. Suitable representatives of such a filler are Cu.sub.2O or Al.sub.2O, metallic fillers which have a thermal conductivity of at least 50 W / mK and an expansion coefficient of between 4 and 6 ppm / K, as in the case of Mo, Cr or W. In order to achieve a significant reduction in the thermal expansion coefficient, a ceramic and / or metallic filler content in the amount of at least 5 vol.% Is used. A particularly effective reduction of the expansion coefficient becomes possible when the ceramic filler Cu 2 O is generated in situ. This can be achieved by using copper

Starting powders are achieved with a particle size <1 micron under special (non-reducing) sintering atmospheres. c) To achieve a compact body, it is advantageous to correspondingly high

Use sintering temperatures and / or correspondingly long sintering times. As stated above, it may be e.g. in the case of diamond, come to conversions. Process control, which is based on high sintering temperatures in combination with high heating and cooling rates and short sintering times, helps to avoid unwanted transformations. The use of inductively or conductively heated hot-pressing technology or of innovative sintering processes, such as spark plasma sintering or their modified forms, allows the production of a

Material with appropriate properties while suppressing unwanted transformations.

The present invention describes materials which are composed essentially of three components: metallic matrix A, ceramic and / or metallic filler B, on

Carbon-based filler C, the latter may optionally be provided with a coating D.

The special choice of the metallic and / or ceramic filler B has the following reason: The filler should on the one hand have a very low coefficient of thermal expansion and at the same time either have a high thermal conductivity and / or not disturb the thermal conductivity of the copper-based matrix sensitively.

Copper oxide (cuprite, Cu2O) is a ceramic filler characterized by a low thermal expansion coefficient of about 4-6 ppm / K. At the same time, the Cu2O content in a copper matrix negatively affects them only in an approximately linear context. Via the so-called rule of mixtures, the thermal conductivity can λ and also the thermal expansion coefficient α of a matrix-Inclusion mixture from the volume fractions of the individual components is calculated (VMatπx V | _n ki _US j _On.): A = V _Matrιx • λ _Uatrιx + V _1Musιnn • λ _hΛlmwn

^{a =} "matrix ^'a matrix ⁺ ^ inclusion ^{' a} inclusion It follows that at a volume ratio of 50vol. % Copper matrix too

50 vol.% Non-thermally conductive inclusion the thermal conductivity of the

Composite is still at about 200 VWmK, while the

Expansion coefficient was reduced to a value of about 10 ppm / K (originally 16 ppm / K).

If one now chooses a Cu-Cu2O mixture as a matrix, which is reinforced with a carbon-based filler such as diamond, e.g. 50 vol.% Cu-Cu 2 O matrix (= 25 vol.% Cu + 25 vol.% Cu 2 O) and 50 vol.% Diamond, then results (with a thermal conductivity of the diamond of 1000 W / mK and an expansion coefficient of 1 ppm / K) has a thermal conductivity of 600 W / mK and an expansion coefficient of about 5.5 ppm / K. In the case of the ceramic filler Cu 2 O or a pure copper matrix, however, the thermal transition between the matrix and the carbon-based filler must not be neglected. For this reason, it is expedient to use coated fillers (for example with Mo or Cr layer) in order to allow a corresponding thermal transition between the matrix and the thermally highly conductive filler. In this case, if the proportion of these coatings is kept low, there is only an insignificant deterioration in the thermal conductivity of the copper-based matrix. Figure 3 shows the possibility of varying the coefficient of expansion B by the variation of the filler content B, as with a constant filler content C of 50% by volume.

To obtain Cu2O in the final product, this can be mixed as a filler directly in the form of Cu2O or CuO particles with the matrix or with the thermally highly conductive filler C or as an alternative method, the Cu2O also in-situ during the preparation of Composite are formed directly. This is achieved either by a corresponding process control (no reducing atmosphere) and / or by the use of very fine-grained copper powders in the submicron grain size range with a high specific surface area. Especially with the use of copper nanopowders it is possible to produce finely divided Cu2O oxides in a high proportion due to the high oxygen affinity of these powders.

A composite with reduced thermal expansion can be achieved even if special metallic fillers are selected which have a low coefficient of thermal expansion of 4-6 ppm / K and additionally have a positive influence on the thermal contact between matrix and carbon-based fillers, even if they are used in a large amount (> 5 vol.%). In addition, a large amount of the metallic fillers makes it possible to dispense with the coating of the carbon-based filler optionally can be, without causing a significant deterioration of the thermal properties. A high metallic filler content and / or a coating of the filler in combination with a high sintering temperature (in some cases already above the temperature at which diamond is thermally unstable and converted into graphite) allows the use of extremely short sintering times. Due to the high metal filler content, only short diffusion distances to the carbon-based filler C are traceable.

Materials with a low thermal expansion coefficient and a thermal conductivity of 200 W / m K and more are popular materials in the field of electronics, either as a carrier plate or as a heat sink. The increasing demands of the electronics industry require materials with thermal conductivities of more than 300 W / mK and an expansion coefficient in the range of 6-10 ppm / K. In many cases, these requirements can not even be met by composite materials such as Cu-Mo, Cu-W or AISiC. Although AIN and SiC can be used as a heat sink, they are expensive. The thermal properties are about 270 W / mK for SiC and 250 W / mK for AIN.

Heat sinks for laser applications are already made of diamond or CBN is used in laser diodes. Diamond can be produced by CVD or by high-temperature high-pressure process. CBN is produced by the latter method. Both are just as expensive, and limited in size. The coefficient of expansion of CVD diamond is 2.3 ppm / K, of cBN 3.7 ppm / K and is therefore lower than that of GaAs (5.9ppm / K) or InP (4.5ppm / K). This suffers from the reliability during operation but also during the soldering process. Diamond-based composites such as Cu-diamond, Al-diamond or Ag-diamond represent a promising alternative. Since both the pure Cu or AI matrix are characterized by a high thermal expansion coefficient of 17 and 22 ppm / K respectively Although a reduction in the coefficient of expansion by the diamond filler can be achieved here, volume fractions of more than 55 vol.% are required in order to obtain an expansion coefficient of 8 or more than 65 vol.% and an expansion coefficient of 7 ppm / K. This means that often complex, time-consuming and cost-intensive processes must be used for this.

Patents US 6,171,691 and EP 0898310 A2 describe a material consisting of a metal such as Cu, Ag, Au, Al, Mg or Zn, a carbide formed from the metals of the Periodic Table 4a and 5a and Cr and a Diamantfüllstoff. The diamond filler is covered by a carbide layer. The preparation of the material takes place via the liquid phase of the metal matrix.

Patent WO 2004/044950 A3 describes a material consisting in

Essentially from a copper matrix and diamond, which can be used for the production of coated diamonds. The process of preparation is multi-stage and uses reducing hydrogen atmosphere to the formation of

To avoid copper oxides. These are described as disturbing components.

Patent WO 2004/080913 A1 describes a method for producing a

Diamond-based material using Cu, Ag, Au or their alloys. Here also wetting-promoting alloying elements <3 at.% Like

Ni, Cr, Ti, V, Mo, W, Nb, Ta, Co, Fe used and additionally at least one element from the group Si, Y, Sc.

Patent US 2004 / 0183172A1 describes a material consisting of a metal based on copper or silver, wherein the attachment to the diamond takes place via a metal carbide.

Patent EP 1160860 A1 describes a material which consists of Cu, Al or Ag, wherein various elements are used to improve the wetting in order to improve the wettability of graphite or carbon in the liquid-phase infiltration process of a porous preform. Patent US 2005/0051891 A1 describes a material with 60-90 vol.%

Diamond. The matrix used here is copper. With this method it is possible to obtain a material with a coefficient of expansion below 6 ppm / K. In order to obtain a dense compact body, however, pressures of 1 to 6 GPa are used here. Such a process is costly (required Sintreranlageri), also the production is limited to simple geometries. Appropriate measures are taken to avoid the formation of copper oxides. The oxygen content is less than 0.07 wt.%.

Patents US 5,783,316 and US 6,264,882 describe a material of the

Liquid phase infiltration of a porous preform is produced. Coated diamonds are also used, e.g. with W, Zr, Re, Cr and Ti layers. The matrix used here is Cu, Ag or Cu-Ag. The porous preform is in a second

Step infiltrated.

In principle, two-stage processes (pressing a preform and sintering or

Infiltration) secondarily and require an exact control of sintering and infiltration conditions. A pore-free body is only achieved if appropriate porosity is present, which leads via capillary forces that a complete infiltration takes place. To make this possible must be coated Diamond particles and / or alloying elements are used. The proportion of coated elements or coatings used is usually less than 3 vol.% And thus has little effect on a reduction of the thermal expansion coefficient of the metal matrix. For the production of a composite material with adapted thermal

Expansion properties is thus a method that works especially quickly and therefore cost-effective. The production takes place while applying mechanical pressure in combination with a suitable temperature control. For this purpose, the corresponding powder mixture is filled in a die, for example made of graphite, and optionally precompressed at a pressure of a few MPa. The precompressed press die is inserted into a corresponding conductive or induction heated hot press and then evacuated.

The efficient production is achieved by a high heating / cooling rate in combination with a short sintering time. By deliberately avoiding a reducing sintering atmosphere, it is not only possible to use simply constructed and therefore cost-effective systems, but also to achieve in situ oxidation to form Cu 2 O in order to reduce the coefficient of expansion of the matrix. This in-situ oxidation can be controlled both by the grain size of the starting copper powder and / or by the process conditions used. High heating rates (of a few 100 K / min) can be achieved by processes such as induction or conductively heated hot presses. Modified methods are, for example, spark plasma sintering or field assisted sintering. By using high heating rates and short sintering times, it is possible on the one hand to deliberately suppress the conversion of diamond into carbon even when high sintering temperatures of 1000 ^° C. or more are used. After the holding time at the desired temperature, the template is cooled together with the sample, the vacuum chamber is vented and the sample is removed and shaped.

The procedure according to the invention for the production of materials according to the invention will be explained below with reference to examples.

Example 1 :

11, 04 g synthetic diamond powder with a grain size of 300 microns were coated with a layer of about 200 nm Mo via a PVD process and were mixed with 28.05 g of Cu with a particle size of ~ 100 nm for 12 hours in isopropanol in a Turbulamischer and then dried. From the powder mixture 7.5 g were filled into a 20 mm diameter graphite die and precompacted at a pressure of 5 MPa. The filled and pre-compacted graphite die was set in a induction-heated hot press and evacuated to a pressure of 10 mbar ^{'. 2} At the same time, the mechanical pressure was increased to 50 MPa and a heating rate of 150 ° C / min realized by means of an induction coil.

After reaching a temperature of 900 ⁰ C and a holding time of 2 minutes, the sample was cooled at a cooling rate of about 200 ° C / min to about 400 ⁰ C; after a temperature of about 100 ⁰ C was reached, the vacuum vessel was vented. By using Cu nanopowder under non-reducing conditions, in situ formation of Cu 2 O in the copper matrix occurred. The proportion of Cu2O was determined to be about 14.2 vol.% Via XRD. To measure the thermal expansion coefficient, the samples were examined by means of a dilatometer in a temperature range from RT to 300 ^° C. A mean expansion coefficient of 8.6 ppm / K in this range was determined, at 50 ⁰ C this was 7.6 ppm / K. according to figure 4.

Example 2: 8.84 g of synthetic diamond powder having a particle size of 300 μm were coated with a layer of about 200 nm Mo via a PVD process and dried with 33.66 g of Cu having a particle size <15 μm for 2 hours in a turbulam mixer mixed. Of these, 8 g were filled into a 20 mm diameter graphite die and precompressed at a pressure of 5 MPa. The filled and pre-compacted graphite die was placed in an induction heated hot press and evacuated to a pressure of 10 ^"2 mbar, simultaneously increasing the mechanical pressure to 50 MPa and a heating rate of 150 ° C / min by means of an induction coil.

After reaching a temperature of 900 ⁰ C and a holding time of 2 minutes, the sample was cooled at a cooling rate of about 200 ° C / min to about 400 ⁰ C; after a temperature of about 100 ⁰ C was reached, the vacuum vessel was vented. By using non-reducing conditions, in situ formation of Cu2O in the copper matrix occurred. The proportion of Cu2O was determined to be about 8.2% by volume over XRD (Figure 5). The measurement of the coefficient of thermal expansion was carried out by means of dilatometer in a temperature range from RT to 300 ⁰ C measured. An average expansion coefficient of 10.8 ppm / K in this range was determined, at 50 ° C this was 9.6 ppm / K.

Example 3

11, 04 g of synthetic diamond powder with a grain size of 300 microns were coated in a thickness of about 200 nm Mo via a PVD process and were with 16.8 g of Cu with a particle size <50 microns and 7.7 g Cu2O powder with a Grain size of <20 microns mixed in a Turbula mixer for 2 hours. This corresponds to a volume share from 20 vol.%. From this mixture, 7 g were filled into a 20 mm diameter graphite die and precompressed at a pressure of 5 MPa. The filled and precompacted graphite die was placed in an inductively heated hot press and evacuated to a pressure of 10 ^"2 mbar, simultaneously increasing the mechanical pressure to 50 MPa and achieving a heating rate of 150 ° C / min by means of an induction coil.

After reaching a temperature of 95O ⁰ C and a holding time of 2 minutes, the sample was cooled at a cooling rate of about 200 ° C to about 400 ⁰ C; after a temperature of about 100 ⁰ C was reached, the vacuum vessel was vented. To measure the thermal expansion coefficient, the samples were examined by means of a dilatometer in a temperature range from RT to 300 ^° C. An average expansion coefficient of about 8.1 ppm / K in this range was determined, at 50 ⁰ C this was 7.2 ppm / K.

Example 4

11, 04 g synthetic diamond powder with a grain size of 300 microns were coated with a layer of a thickness of about 500 nm Cr via a PVD process and were with 28.05 g of Cu with a particle size ~ 100 nm for 12 hours in isopropanol in a Turbulamischer mixed and then dried. From the powder mixture, 3 g was filled into a 12.5 mm diameter graphite die and precompacted at a pressure of 5 MPa. The filled and precompacted graphite die was placed in a Spark Plasma sintering unit and evacuated to a pressure of 10 ^"1 mbar, simultaneously increasing the mechanical pressure to 30 MPa and achieving a heating rate of 150 ° C / min using pulsed DC a temperature of 900 ⁰ C and a holding time of 2 minutes, the sample was cooled at a cooling rate of about 200 ⁰ C to about 400 ⁰ C, after which a temperature was reached about 100 ⁰ C, the vacuum vessel was vented by using. Cu nanopowders under non-reducing conditions showed an in-situ formation of Cu 2 O. The proportion of Cu 2 O was determined to be about 18.7% by volume .. For the measurement of the coefficient of thermal expansion, the samples were measured by means of a dilatometer in a temperature range from RT to 300 ^° C. A mean expansion coefficient of 8.5 ppm / K in this range was determined, at 50 ^° C. it was 7.4 ppm / K.

In addition to Mo or Cr for coating the diamond, layers of, for example, W, Ta, B or AlN, which likewise bring about good adhesion or thermal contact, are also suitable. Example 5:

5.53 g of a PITCH carbon fiber were coated with a ca. 100 nm thick Mo layer by a PVD process, mixed with 33.67 g of Cu powder with a particle size <30 μm with isopropanol for 24 hours, dried and in a graphite matrix with a diameter 40 mm filled and precompacted at a pressure of 5 MPa. The filled and pre-compacted graphite die was set in a field assisted sintering plant and evacuated to a pressure of 10 mbar ^{'. 2} At the same time, the mechanical pressure was increased to 50 MPa and realized a heating rate of 200 ° C / min by means of pulsed direct current. After reaching a temperature of 900 ⁰ C and a holding time of 2 minutes, the sample was cooled at a cooling rate of about 200 ° C to about 400 ⁰ C; after a temperature of about 100 ° C was reached, the vacuum vessel was vented. The proportion of Cu2O was estimated to be about 1.9% by volume using XRD measurement (Figure 6). To measure the thermal expansion coefficient, the samples were examined by means of a dilatometer in a temperature range from RT to 200 ^° C. An average coefficient of expansion in the xy direction of 10.8 ppm / K in this range was determined, at 50 ^° C. it was 8.9 ppm / K.

Example 6: 23.32 g of synthetic diamond powder with a particle size of 50-60 μm, 6.82 g

Mo powders with a particle size <50 μm, 53.34 g Cu with a particle size <30 μm were dry mixed for 2 hours in a Turbula mixer and filled in a graphite matrix with a diameter of 65 mm and precompacted at a pressure of 5 MPa. The filled and pre-compacted graphite die was set in a hot press and evacuated to a pressure of 10 mbar ^{~ 2} and purged with hydrogen. At the same time, the mechanical pressure was increased to 20 MPa and a heating rate of 50 ° C / min was applied.

After reaching a temperature of 95O ⁰ C and a holding time of 15 minutes, the sample was cooled; after a temperature of about 100 ⁰ C was reached, the container was flooded with nitrogen and vented. The thermal expansion coefficient was measured in a temperature range of RT to 300 ⁰ C. A mean expansion coefficient of about 10.5 ppm / K in this range was found, at 5O ⁰ C this was 10.0 ppm / K (Figure 7). Similar properties can be achieved using other metallic or ceramic fillers, such as W, Ta, B or AIN and Al2O3.

Example 7:

2.2 g of synthetic diamond powder with a grain size of 300 microns, which were coated with an approximately 500 nm thick Cr layer, 0.45 g Cr powder with a grain size <50 .mu.m, 5.05 g of Cu with a particle size <30 .mu.m were dry mixed for 2 hours in a Turbulamischer and filled in a graphite die with a diameter of 20 mm and precompacted at a pressure of 5 MPa. The filled and pre-compacted graphite die was placed in an induction heated hot press and evacuated to a pressure of 10 ^"2 mbar, simultaneously increasing the mechanical pressure to 50 MPa and a heating rate of 150 ° C / min by means of an induction coil.

After reaching a temperature of 1000 ⁰ C and a holding time of 2 minutes, the sample was cooled at a cooling rate of about 200 ⁰ C to about 400 ⁰ C; after a temperature of about 100 ⁰ C was reached, the vacuum vessel was vented. To determine the thermal expansion coefficient, the sample was measured in a temperature range from RT to 300 ^° C. The proportion of Cu2O was determined to be about 1.2% by volume by XRD measurement. An average expansion coefficient of about 8.8 ppm / K in this range was determined, at 50 ° C this was 8.4 ppm / K. (Figure 7)

Example 8:

2.2 g of synthetic diamond powder with a grain size of 300 .mu.m, which were coated with an approximately 500 nm thick Cr layer, 1, 80g Cr powder with a particle size <50 microns, 3.37 g of Cu with a particle size <30 microns were 2 Dry mixed in a Turbulamischer and filled in a graphite die with a diameter of 20 mm and precompacted at a pressure of 5 MPa. The filled and precompacted graphite die was placed in an induction heated hot press and evacuated to a pressure of 10 ^"2 mbar, simultaneously increasing the mechanical pressure to 50 MPa and achieving a heating rate of 150 ° C / min by means of an induction coil of 1000 ⁰ C and a holding time of 2 minutes, the sample was cooled at a cooling rate of about 200 ⁰ C to about 400 ⁰ C;. after a temperature was reached about 100 ⁰ C, the vacuum vessel was vented the proportion of Cu2O was To determine the thermal expansion coefficient, the sample was measured in a temperature range from RT to 300 ^° C. A mean expansion coefficient of approximately 6.6 ppm / K in this range was determined at 5O ⁰ C was 5.9 ppm / K (Figure 7)

Example 9 0.53 gr Vitreous Grown Carbon Fibers were coated with 5.6 g of Cu powder

Grain size <30 microns and 2.6 g of Mo were mixed with isopropanol for 24 hours, dried and filled in a graphite die with a diameter of 20 mm and with a Pressure of 5 MPa precompacted. The filled and vorkom pact graphite die was set in a hot press and evacuated to a pressure of 10 mbar ^{'. 2} At the same time, the mechanical pressure was increased to 20 MPa and a heating rate of 150 ° C / min was applied. After reaching a temperature of 900 ⁰ C and a holding time of 15 minutes, the sample was cooled at a cooling rate of about 200 ° C to about 400 ° C; after a temperature of about 100 ⁰ C was reached, the vacuum vessel was vented. The proportion of Cu2O was determined to be about 1.6 vol.% By XRD measurement. The thermal expansion coefficient was measured by dilatometer for the xy direction in a temperature range of RT to 200 ⁰ C. An average expansion coefficient of about 13.3 ppm / K in this range was determined, at 50 ° C this was 11, 8, ppm / K.

It was found that the substances or elements used for the filler B can be substituted with one another without adversely affecting the mechanical and / or physical, etc. structure of the resulting material. The same applies to the materials used for the filler C.

Claims

claims:

1. Material comprising

- A metal matrix A, the or the material in at least one spatial direction has a coefficient of thermal expansion in the range of 16 to 20 ppm / K, and of

Copper or a copper alloy is formed and represents 10 to 75 vol.%., Preferably 35 to 55 vol.%, Of the material,

at least one metallic and / or ceramic filler B having a coefficient of thermal expansion in the range from 4 to 6 ppm / K in at least one spatial direction, of Cu 2 O and / or Al 2 O 3 and / or AlN and / or Mo and / or Cr and / or W and / or B and / or Ta is formed and is present in the material in an amount of from 1 to 40% by volume, preferably 10 to 30%, in particular 10 to 25% by volume,

- At least one carbon-based, optionally coated or coated with a coating, filler C, which is characterized by a thermal expansion coefficient of - 2 to +2 ppm / K in at least one spatial direction, has high thermal conductivity, of graphite and / or Carbon fibers and / or carbon nanofibers and / or carbon nanotubes and / or diamond is formed and in an amount of 5 to 65 vol.%, Preferably 30 to 50 vol.%, In particular 39 to 41 vol.% Is present, and - That optionally in the material in addition to the material of the metal matrix A and the fillers B and C amorphous and / or intermediate substances or compounds in the amount of <5 vol.% Are included.

2. Material according to claim 1, characterized in that the filler C forming substances, in particular diamond, with the elements Mo and / or Cr and / or W and / or Ta and / or B and / or AIN, coated or with coated with a coating, wherein the proportion of the layer from 0.1 to 5 vol.%, Preferably 0.3 to 2 vol.%, In particular 0.5 to 1, 0 vol.%, Of the material.

3. Material according to claim 1 or 2, characterized in that the material is a homogeneous distribution of the fillers B and C in the metal matrix A.

4. Material according to one of claims 1 to 3, characterized in that the tubes or fiber fillers have a preferred orientation perpendicular to the pressing direction of the material.

5. Material according to one of claims 1 to 4, characterized in that the material has a thermal expansion coefficient of 4 to 12 ppm / K in at least one spatial direction.

6. Material according to one of claims 1 to 5, characterized in that the material has a thermal conductivity of at least 200 W / mK in at least one spatial direction, preferably of at least 300 W / mK, in particular of at least 400 W / mK.

7. Material according to one of claims 1 to 6, characterized in that the material has a density> 80% (based on the theoretical density), preferably more than 90%, in particular more than 95%.

8. Material according to one of claims 1 to 7, characterized in that the material is created by a sintering process or sintering of the material of the metal matrix A and the fillers B and C.

9. Material according to one of claims 1 to 8, characterized in that the metal matrix A has a particle size of <50 microns, preferably <5 microns, in particular <2 microns, wherein advantageously the lower limit is set at 10 nm.

10. Material according to one of claims 1 to 9, characterized in that the filler B in a particle size of <50 microns, preferably <20 microns, in particular <10 microns, is present, wherein advantageously the lower limit of the filler B with 1 micron is scheduled.

11. Material according to one of claims 1 to 10, characterized in that the filler C in the case of diamond has a particle size in the range <500 .mu.m, preferably <300 .mu.m, preferably <100 .mu.m, advantageously greater than 1 .mu.m.

12. Material according to one of claims 1 to 11, characterized in that the filler C in the form of carbon fibers having a diameter between 5 to 15 microns and a length in the range of 10 to 1000 .mu.m, preferably 100 to 500 .mu.m, in particular 300 to 500 microns and / or in the form of graphite nanofibers having a diameter in a range of 100 to 500 nm and a length in the range of 1 to 500 .mu.m, preferably 10 to 300 .mu.m, in particular 50 to 100 microns, is present and / or in the form of Kohienstoff nanotube having a diameter in the range of 10 to 200 nm and the length in a range of 1 to 200 .mu.m, preferably 80 to 120 microns, is present.

13. Material according to one of claims 1 to 12, characterized in that in the presence of a copper alloy as the metal matrix A, the copper alloy elements, e.g. Tin and / or zinc, up to 15 wt.%.

14. Material according to one of claims 1 to 13, characterized in that the material has an expansion coefficient of 4 to 12 (.10 ^'6 K ^{' 1} ) in a temperature range from 20 ⁰ C to 50 ⁰ C.

15. A method for producing a material, in particular having the features of one of claims 1 to 14, with a preselectable or predetermined thermal expansion coefficient, wherein a powder mixture comprising powder of copper and / or copper alloy for the formation of a metal matrix A in an amount from 15 to 75 vol.%, preferably 35 to 55 vol.%,

Powder of Cu 2 O and / or Al 2 O 3 and / or AlN and / or Mo and / or Cr and / or W and / or B and / or Ta in an amount of 1 to 40% by volume, preferably 10 to 30%, in particular 10 to 25 vol.%, as filler B, and powder of graphite and / or carbon fibers and / or carbon nanofibers and / or carbon nanotubes and / or diamond in an amount of 5 to 65 vol.%, preferably 30 to 50 vol .%, In particular 39 to 41 vol.%, As filler C after mixing at a heating rate of more than 50 ° C / min, in particular more than 100 ° C / min, in particular more than 150 ° C / min, brought to sintering temperature and the sintering temperature in a range of 700 ⁰ C to 1300 ⁰ C, preferably 850 ⁰ C to 1050 ⁰ C, for a holding time or duration of 0.1 to 250 minutes, preferably 1 to 60 minutes, especially 2 to 15 min , is set or held and then the sintered body is cooled and removed from the mold, the volume% on the total volume of the used Pulvergemenges are related.

16. The method according to claim 15, characterized in that the powder used as filler C, in particular diamond, coated or coated with a coating, with the elements Mo and / or Cr and / or W and / or Ta and / or B and / or AIN, wherein the proportion of the layer is 0.1 to 5 vol.%, Preferably 0.3 to 2 vol.%, In particular 0.5 to 1.0 vol.%, Of the powder mixture.

17. The method according to claims 15 or 16, characterized in that the heating of the mixture and / or the sintering process under air or industrial gases, for example hydrogen, argon, nitrogen, or under vacuum, in particular less than 10 ^"1 mbar, is made.

18. The method according to any one of claims 15 to 17, characterized in that the mixture of the starting powder is precompressed in a mold, in particular a graphite die, wherein the precompression is set to 1 to 15 MPa, in particular between 5 to 10 MPa ,

19. The method according to any one of claims 15 to 18, characterized in that during sintering, a pressure of at least 5 MPa, in particular from 20 to 50 Mpa, is maintained.

20. The method according to any one of claims 15 to 19, characterized in that the metal matrix A in the form of a matrix starting powder with a particle size of <50 microns, preferably <5 microns, in particular <2 microns, is used.

21. The method according to any one of claims 15 to 20, characterized in that the filler B in the form of a powder having a particle size of <50 microns, preferably <20 microns, preferably <10 microns, is used.

22. The method according to any one of claims 15 to 21, characterized in that the filler C - in the case of diamond with a particle size of 1 to 500 microns, preferably 1 to 300 microns, preferably 1 to 100 microns, is used,

- In the case of carbon fibers with a diameter in a range of 5 to 15 microns and a length of 10 to 1000 .mu.m, preferably 100 to 500 .mu.m, in particular 300 to 500 microns, are used, - in the case of graphite nanofibers with a diameter in a range of 100 to 500 nm and a length in a range of 1 to 500 .mu.m, preferably 10 to 300 .mu.m, in particular 10 to 100 .mu.m, is used, and

- In the case of carbon nanotubes, these with a diameter in a range of 10 to 200 nm and a length in a range of 1 to 200 .mu.m, preferably 1 to 100 .mu.m used or added to the starting mixture.

23. The method according to any one of claims 16 to 22, characterized in that the coating is applied by deposition of the layer material via the gas phase (chemical or physical vapor deposition, CVD or PVD) by wet chemical methods or by a spray process on the filler C.

24. The method according to any one of claims 15 to 23, characterized in that in the material by selecting the sintering temperature and / or the sintering time, a density is set, which is greater than 80%, in particular greater than 90%. the theoretically achievable material density.

25. The method according to any one of claims 15 to 24, characterized in that the sintered body of the sintering temperature at a cooling rate of more than 50 ° C / min, preferably more than 100 ° C / min, in particular more than 200 ° C / min, is cooled.

26. The method according to any one of claims 15 to 25, characterized in that during the heating process from the periphery of the material material forth uniform heating of the starting material or starting powder located in a mold is made.