Method for producing a composite material

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The invention relates to a process for producing a diamond-containing composite material. Diamond grains having a mean particle size of from 5 to 300 μm are infiltrated under atmospheric pressure or with the aid of pressure with a eutectic or near-eutectic alloy which has a solidus temperature of <900° C. and comprises at least one element or an alloy from the group consisting of Cu, Ag, Au and at least one element from the group consisting of Si, Y, Sc, rare earth metals or densified by hot pressing. The components produced in this way have a high thermal conductivity and low thermal expansion and are particularly useful as heat sinks for semiconductor components.

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Description

The invention relates to a process for producing a diamond-containing composite material.

Diamond-containing composite materials have been used for a long time as cutting tool materials. In addition, owing to the high thermal conductivity and low thermal expansion of diamond, they are also potentially interesting materials for heat sinks. Thus, the thermal conductivity of diamond is from 1000 to 2000 W/(m.K), with the content of nitrogen and boron atoms on lattice sites being of special importance for determining the quality.

Heat sinks are widely used in the production of electronic components. Apart from the heat sink, semiconductor components and a mechanically stable encapsulation are the essential constituents of an electronic package. The terms substrate, heat spreader or support plate are frequently also used for the heat sink. The semiconductor component comprises, for example, single-crystal silicon or gallium arsenide. This is connected to the heat sink, usually using soldering methods as joining technique. The heat sink has the function of conducting away heat produced during operation of the semiconductor component. Semiconductor components which produce a particularly large quantity of heat are, for example, LDMOS (laterally diffused metal oxide semiconductor), laser diodes, CPU (central processing unit), MPU (microprocessor unit) or HFAD (high frequency amplify device).

The geometric configurations of the heat sink are specific to the application and may vary widely. Simple forms are flat plates. However, substrates having a complex configuration with recesses and steps are also used. The heat sink itself is in turn joined to a mechanically stable encapsulation. The coefficients of thermal expansion of the semiconductor materials used are low compared to other materials and are reported in the literature as from 2.1×10−6 K−1 to 4.1×10−6 K−1 for silicon and from 5.6×10−6 K−1 to 5.8×10−6 K−1 for gallium arsenide.

Other semiconductor materials which are not yet widely used in industry, e.g. Ge, In, Ga, As, P or silicon carbide, also have similarly low coefficients of expansion. Ceramic materials, material composites or plastics are usually used for the encapsulation. Examples of ceramic materials are Al2O3 with a coefficient of expansion of 6.5×10−6 K−1 or aluminum nitride having a coefficient of expansion of 4.5×10−6 K-−1.

If the expansion behavior of the participating components is different, stresses are incorporated in the composite, and these lead to distortion, to detachment of material or to fracture of the components. Stresses can arise during manufacture of the package, specifically during the cooling phase from the soldering temperature to room temperature. However, temperature fluctuations also occur during operation of the package, and these can extend, for example, from −50° C. to 200° C. and lead to thermal mechanical stresses in the package.

In recent years, the process speed and degree of integration of semiconductor components have increased greatly, which has also led to an increase in the evolution of heat in the package.

These factors determine the requirements for diamond-containing composite materials for heat sinks. Firstly, these should have a very high thermal conductivity in order to keep the temperature rise of the semiconductor component during operation as low as possible. Secondly, it is necessary for the coefficient of thermal expansion to be matched as well as possible to that of the semiconductor component and also that of the encapsulation.

EP 0 521 405 describes a heat sink which has a polycrystalline diamond layer on the side facing the semiconductor chip. The absence of plastic deformability of the diamond layer can lead to cracks in the diamond layer even during cooling from the coating temperature.

U.S. Pat. No. 5,273,790 describes a diamond composite material having a thermal conductivity of >1700 W/(m.K) in the case of which loose diamond particles brought to shape are converted into a stable shaped body by means of subsequent diamond deposition from the gas phase. The diamond composite produced in this way is too expensive for commercial use in mass-produced parts.

WO 99/12866 describes a process for producing a diamond-silicon carbide composite material. It is produced by infiltration of a diamond skeleton with silicon or a silicon alloy. Owing to the high melting point of silicon and the resulting high infiltration temperature, diamond is partly converted into carbon or subsequently into silicon carbide. Owing to the high brittleness, the mechanical forming of this material is highly problematical and costly, so that this composite material has hitherto not yet been used for heat sinks.

U.S. Pat. No. 4,902,652 describes a process for producing a sintered diamond material. An element from the group of transition metals of groups 4a, 5a and 6a, boron and silicon are deposited onto diamond powder by means of physical coating methods in this process. The coated diamond grains are subsequently joined to one another by means of a solid-state sintering process. Disadvantages are that the product formed has a high porosity and a coefficient of thermal expansion which is too low for many applications.

U.S. Pat. No. 5,045,972 describes a composite material in which diamond grains having a size of from 1 to 50 μm and also a metallic matrix comprising aluminum, magnesium, copper, silver or an alloy thereof are present. A disadvantage is that the metallic matrix is bound only unsatisfactorily to the diamond grains, so that, as a result, the thermal conductivity and mechanical integrity are not sufficient.

The use of finer diamond powder, for example diamond powder having a particle size of <3 μm, as is described in U.S. Pat. No. 5,008,737, also does not improve diamond/metal adhesion.

U.S. Pat. No. 5,783,316 describes a process in which diamond grains are coated with W, Zr, Re, Cr or titanium, the coated grains are subsequently compacted and the porous body is infiltrated, for example, with Cu, Ag or Cu—Ag melts. The high coating costs limit the uses of composite materials produced in this way.

EP 0 859 408 describes a material for heat sinks whose matrix is made up of diamond grains and metal carbides, with the interstices of the matrix being filled by a metal. As metal carbides, mention is made of the carbides of metals of groups 4a to 6a of the Periodic Table. TiC, ZrC and HfC are particularly emphasized in EP 0 859 408. Ag, Cu, Au and Al are said to be particularly advantageous filler metals. A disadvantage is that the metal carbides have a low thermal conductivity, which in the case of TiC, ZrC, HfC, VC, NbC and TaC is in range from 10 to 65 W/(m.K). A further disadvantage is that the metals of groups 4a to 6a of the Periodic Table have a degree of solubility in the filler metal, for example silver, as a result of which the thermal conductivity of the metal phase is greatly reduced.

EP 0 893 310 describes a heat sink comprising diamond grains, a metal or a metal alloy having a high thermal conductivity from the group consisting of Cu, Ag, Au, Al, Mg and Zn and a metal carbide of the metals of groups 4a, 5a and Cr, with the metal carbides covering at least 25% of the surface of the diamond grains. EP 0 898 310 also describes techniques, for example an infiltration process, for producing a heat sink. Alloys comprising a metal having a high thermal conductivity and a carbide-forming metal from the group of the elements of groups 5a, 6a and Cr are used for this purpose. However, two-component alloys of these components require infiltration temperatures of above 1000° C., as a result of which unacceptably high decomposition of diamond into graphite occurs. The examples of EP 0 898 310 therefore describe three-component alloys consisting of Cu—Ag—Ti. Even when Ti reacts completely with diamond to form TiC, the metallic region surrounding the diamond or carbide regions consists of an Ag—Cu alloy and therefore has a significantly lower thermal conductivity than pure Ag. In addition, in the three-component system Ag—Cu—Ti or in systems in which Ti has been replaced by Zr, Hf, Mo, W, V or Cr, the solidus or liquidus temperature is increased compared to the eutectic temperature of an Ag—Cu alloy. Thus, the liquidus temperature of a eutectic Ag—Cu alloy (Ag-30% by weight of Cu) is 780° C., while the Cu—Ag—Ti alloys mentioned in EP 0 898 310 have a liquidus temperature of from 830 to 870° C.

It is therefore an object of the present invention to provide a process which makes it possible to produce diamond-containing composite materials having a high thermal conductivity and a low coefficient of expansion in an inexpensive, reliable manner.

This object is achieved by a process as claimed in claim 1 or claim 2 of the present invention.

The process of the invention comprises a shaping step carried out under atmospheric pressure or with the aid of pressure to produce an intermediate. The intermediate comprises diamond powder having a mean particle size of the diamond grains of from 5 to 300 μm. A preferred particle size range is from 60 to 250 μm. Fine diamond grains and thus a large interfacial area to adjoining neighboring phases reduce the thermal conductivity. Pressureless processes are, for example, pouring processes, vibratory introduction processes or slip casting. Pressure-aided techniques are, for example, die pressing, isostatic pressing and powder injection molding. Depending on the technique chosen, the proportion of diamond after the shaping process is from 40 to 90%, based on the total volume. The remainder comprises pores and/or binder and/or metallic components having a high thermal conductivity. An incorporated binder makes it possible to increase the density of the green body or reduces the die friction. Diamond powder and binder are for this purpose mixed in customary mixers or mills. Suitable binders are, for example, those based on polymer or wax. Advantageous proportions of binder are in the range from 1 to 20% by weight. It is advantageous to remove at least part of the binder by means of a chemical or thermal process prior to the infiltration step. In the case of a thermal process, it can be advantageous to carry out the process so that residues of pyrolized carbon remain on the diamond surface and react with part of the infiltrate to form a carbide. Thermal binder removal can also be integrated into the infiltration process. Metallic components having a high thermal conductivity which may be mentioned are Cu, Al, Au and alloys thereof.

The infiltration process can be carried out under atmospheric pressure or with the aid of pressure. The latter is usually referred to as squeeze casting. The infiltrate alloy has a eutectic or near-eutectic composition. Near-eutectic alloys encompass compositions which have a liquidus temperature below 950° C. The infiltrate alloy comprises at least one metallic component having a high thermal conductivity and comprising an element or an alloy from the group consisting of Cu, Ag, Au and at least one element from the group consisting of Si, Y, Sc, rare earth metals. It has been found that the use of infiltrate alloys according to the invention leads to very good wetting of the diamond grains and to a high interface strength between the diamond grains and the surrounding phases. In addition, the infiltrate alloys according to the invention have the advantage that their solidus temperatures are significantly below those of Cu, Au or Ag alloys with the metals of groups 4a/5a of the Periodic Table or Cr, as can be seen from Table 1. This makes it possible to use two-component alloys instead of multicomponent alloys, which has a favorable effect on the thermal conductivity. The solidus temperatures of the infiltrate alloys according to the invention are below 870° C. This ensures that unacceptably high reaction of the diamond does not occur during the infiltration process.

TABLE 1 Con- centration Boundary Solubility at Solubility Eutectic at the system eutectic at tem- eutectic Cu—, Au— temperature 400° C. perature point System or Ag-rich [atom %] [atom %] [° C.] [atom %] Cu—Ti peritect. — 0.8 — — Cu—Zr eutect. 0.12 <0.1 972 8.6 Cu—Hf eutect. 0.4 <0.1 988 7.75 Cu—Mo eutect. <0.1 <0.1 1083 <0.5 Cu—W eutect. <0.1 <0.1 1084 <0.5 Cu—Cr eutect. ca. 1 <0.1 1077 ca.2 Cu—V peritect. — <0.1 — — Cu—Nb eutect. <0.1 <0.1 1080 <0.5 Cu—Ta eutect. <0.1 <0.1 1083 <0.5 Cu—Y eutect. <0.4 <0.1 860 9.3 Cu—La eutect. 0 0 865 9 Cu—Nd eutect. 0 0 865 9 Cu—Pr eutect. 0 0 870 7.5 Cu—Si peritect. — 9 — — Ag—Ti peritect. — 1.5 — — Ag—Zr eutect. <0.1 <0.1 940 2.5 Ag—Mo eutect. <0.1 <0.1 959 <0.5 Ag—Cr eutect. <0.1 <0.1 961 <0.5 Ag—V eutect. <0.1 <0.1 961 <0.5 Ag—Y eutect. 1.31 <0.5 799 11.5 Ag—La eutect. 0.05 <0.1 792 10 Ag—Nd eutect. 0.2 <0.1 806 10.5 Ag—Pr eutect. 0.05 <0.01 802 9.2 Ag—Si eutect. 0 0 835 11 Ag—Ti peritect. — 1.5 — — Au—Hf peritect. — 5 — — Au—Mo eutect. 1.25 ca. 1 1054 2.1 Au—W eutect. <0.1 <0.1 1063 <0.5 Au—Cr peritect. — 25 — — Au—V peritect. — 15 — — Au—Nb peritect. — ca. 8 — — Au—Ta peritect. — ca. 8 — — Au—La eutect. 0 0 808 9 Au—Nd eutect. 0 0 796 9.5 Au—Pr eutect. 0 0 808 12 Au—Si eutect. 0 0 363 19

This reaction can be reduced still further by the use of multicomponent alloys corresponding to the composition ranges indicated in the claims. These multicomponent alloys are particularly advantageous when the infiltration times are long because of the process. However, the use of multicomponent alloys leads to a reduced thermal conductivity.

Table 1 also shows that the infiltrate alloys according to the invention have a very low solvent capability for Y, Si and rare earth metals at the eutectic temperature or at 400° C. This has the advantage that the Cu—, Ag— or Au-rich phase formed by the eutectic conversion has a very high purity and thus thermal conductivity. Alloys of Ag or Au with Cu or up to 3 atom % of Ni likewise have a sufficiently high thermal conductivity which is not reduced to an unacceptable extent by small amounts of undissolved Si, Y, Sc or rare earth metal. Proportions of graphite also do not reduce the thermal conductivity to an unacceptable extent.

Y, Sc, Si and the rare earth metals not only reduce the solidus temperature of Cu, Au and Ag but also produce good wetting and bonding of the Cu—, Au— or Ag-rich phase to the diamond grains. In the case of Ag—Si, an Si—C compound having a thickness in the nanometer range was able to be found. Owing to the low proportion, these phases do not produce any significant deterioration in the thermal conductivity. Also deserving of mention is the thermal conductivity of Si—C of about 250 W/(m.K), which is very high compared to the metal carbides of the elements of groups 4a and 5a of the Periodic Table and chromium carbide. The good wetting behavior ensures that the pores of the intermediate are filled to an extent of at least 97%.

The wetting behavior can be improved still further by addition of Ni, Cr, Ti, V, Mo W, Nb, Ta, Co and/or Fe, but the total content of these elements must not exceed 3 atom %, since otherwise they result in an unacceptably large reduction in the thermal conductivity. The advantages of the infiltrate alloy according to the invention also become apparent when hot pressing is used as densification process. Here, an intermediate comprising from 40 to 90% by volume of diamond grains having a mean particle size of from 5 to 300 μm and from 10 to 60% by volume of a eutectic or near-eutectic infiltrate alloy which has a solidus temperature of <900° C. and comprises at least one metallic component of high thermal conductivity which comprises an element or an alloy from the group consisting of Cu, Ag, Au and at least one element from the group consisting of Si, Y, Sc, rare earth metals and optionally <3 atom % of one or more elements from the group consisting of Ni, Cr, Ti, V, Mo, W, Nb, Ta, Co, Fe which promote wetting, with near-eutectic alloys encompassing compositions which have a liquidus temperature of <950° C., is homogenized by mixing or milling. A die of a hot press, e.g. a graphite die, is filled with the intermediate. The intermediate is subsequently brought to a temperature which is above the solidus temperature of the infiltrate alloy but below 1000° C., for example by conductive heating of the die, and densified, with the pressure being applied by moving the punch. The advantages according to the invention can likewise be achieved when the infiltrate alloy is in the liquid or partially liquid range, i.e. between the solidus temperature and the liquidus temperature.

Depending on the infiltration or hot pressing apparatuses used, it can be advantageous, particularly when a high cooling rate occurs during solidification of the infiltrate alloy, to subject the infiltrated intermediate to a heat treatment so that constituents which have been trapped in solution are precipitated, as a result of which the thermal conductivity is improved. This heat treatment can also have a favorable effect on the interface strength between the diamond particles and the surrounding constituents. This heat treatment step can also be integrated into the cooling process of the infiltration step.

Diamond-containing composite materials produced according to the invention have a sufficiently good mechanical formability due to the very ductile Ag, Au or Cu microstructure constituents. It is also advantageous for inexpensive production that the high thermal conductivity of the Ag—, Au— or Cu-rich microstructure constituents enables the diamond content to be reduced.

Variation of the diamond and metal phase content make it possible to produce heat sinks for a variety of requirements to be tailored in respect of thermal conductivity and thermal expansion.

Further microstructure constituents do not worsen the property to an unacceptable degree as long as their content does not exceed 5% by volume. Here, mention may be made of free Si, C, Y, Sc and rare earth metals. Although these microstructure constituents increase the thermal conductivity slightly, they in the case of C and Si have a favorable effect on the coefficient of thermal expansion by reducing the latter. In addition, they can sometimes only be avoided completely with a relatively high degree of difficulty in terms of the production process.

Particularly advantageous contents of Ag—, Au— or Al-rich phase are from 7 to 30% by volume. Experiments have shown that diamond powder can be processed within a wide particle size spectrum. Apart from natural diamonds, it is also possible to process more inexpensive synthetic diamonds. Excellent processing results have also been achieved using the customary coated diamond types. As a result, the most inexpensive type in each case can be employed. In the case of applications in which the thermal conductivity has to meet extremely high requirements and cost is not critical, it is advantageous to use a diamond fraction having a mean particle size in the range from 50 to 250 μm. Furthermore, the highest thermal conductivity values can be achieved by the use of Ag at contents of from 7 to 30% by volume.

Apart from the particularly advantageous use of the components for conducting away heat in semiconductor components, the composite material of the invention can also be used as heat sink in other applications, for example in the aerospace field or in engine construction.

The invention is illustrated below by means of production examples.

EXAMPLE 1

Natural diamond powder of the grade IIA (Micron+SND from Element Six GmbH) having a mean particle size of 80-150 μm was introduced into a graphite mold having the dimensions 35 mm×35 mm×5 mm. The bulk density was brought to 65% by volume by mechanical shaking. The diamond powder was subsequently covered with a film composed of a eutectic Ag—Si alloy having an Si content of 11 atom % and, to carry out the infiltration, was heated in a furnace to a temperature of 860° C. under reduced pressure, with the hold time being 15 minutes. The subsequent gas pressure infiltration using helium was carried out at 1 bar for 15 minutes. After cooling to room temperature with a hold point at 400° C. for about 10 minutes, the volume contents of the phases present were determined by means of quantitative metallography.

The value for silicon carbide was about 1% by volume, with the silicon carbide mostly enveloping the diamond grains uniformly. Owing to the low thickness of this silicon carbide shell, the modification of the silicon carbide phase could not be determined. Apart from diamond and silicon carbide, the microstructure comprises an Ag-rich phase with embedded Si precipitates which have been formed by the eutectic reaction. The proportion by volume of the Ag-rich phase was about 12%, and that of Si was about 1%. No further constituents apart from Ag could be detected in the Ag-rich phase by means of EDX, so that it can be assumed on the basis of the applicable detection limit that the proportion of Ag is greater than 99 atom %.

To determine the thermal conductivity and the coefficient of thermal expansion, the plate was processed by means of a laser and erosion. A mean value of 500 W/(m.K) was measured for the thermal conductivity at room temperature. The determination of the coefficient of thermal expansion gave a mean value of 8.5 10−6 K−1.

EXAMPLE 2

In a further experiment, synthetic diamond powder of the grade Micron+MDA from Element Six GmbH having a mean particle size of 40-80 μm was processed. Processing was carried out as described in Example 1. The mean thermal conductivity at room temperature of the composite material produced in this way was 410 W/(m.K), and the mean coefficient of thermal expansion was 9.0×10−6 K−1.

EXAMPLE 3

In a further experiment, synthetic diamond powder of the grade Micron+MDA from Element Six GmbH having a mean particle size of 40-80 μm was processed. Processing was carried out as described in Example 1. The infiltration of the bed of diamond powder with a eutectic Ag—Si melt was carried out at a gas pressure of about 40 MPa in a conventional squeeze casting apparatus whose hot forming steel mold had been preheated to 150° C. The temperature of the Ag—Si melt was about 880° C. The subsequent, slow cooling to room temperature was carried out with a hold point at 400° C. for about 15 minutes. The mean thermal conductivity at room temperature of the composite material produced in this way was 480 W/(m.K).

EXAMPLE 4

Synthetic diamond powder of the grade Micron+MDA from Element Six GmbH having a mean particle size of 40-80 μm was processed as described in Example 3, but without a hold phase at about 400° C. for 15 minutes being carried out during cooling from the infiltration temperature. The mean thermal conductivity at room temperature of the composite material produced in this way was 440 W/(m.K), and the mean coefficient of thermal expansion was 8.5×10−6 K−1.

EXAMPLE 5

Natural diamond powder of the grade IIA (Micron+SND from Element Six GmbH) having a mean particle size of 40-80 μm was mixed with 7% by volume of a binder based on epoxy resin. The precursor or intermediate produced in this way was pressed by means of die pressing at a pressure of 200 MPa to give a plate having the dimensions 35×35 mm×5 mm. The porosity of the plate was about 15% by volume.

This plate was subseq uently covered with a film composed of a eutectic Cu—Y alloy having a Y content of 9.3 atom % and, to carry out the infiltration, was heated in a furnace to a temperature of 900° C. under reduced pressure, with the hold time being 15 minutes. To determine the thermal conductivity and the coefficient of thermal expansion, the plate was processed by means of a laser and erosion. A mean value of 410 W/(m.K) was measured for the thermal conductivity at room temperature. The determination of the coefficient of thermal expansion gave a mean value of 7.7 10−6 K−1.

Claims

1-21. (canceled)

22. A method of producing a diamond-containing composite material, which comprises the following steps:

shaping, in a pressureless or pressure-aided shaping process, an intermediate product containing diamond grains having a mean particle size of from 5 to 300 μm and, optionally, metallic components of high thermal conductivity and/or binder, and setting a proportion of diamond after shaping from 40 to 90%, based on a total volume of the intermediate product;
heating, in a pressureless or pressure-aided heating process, the intermediate product and a eutectic or near-eutectic infiltrate alloy having a solidus temperature of <900° C. and containing at least a metallic component of high thermal conductivity with an element or an alloy from the group consisting of Cu, Ag, Au and at least one element from the group consisting of Si, Y, Sc, rare earth metals, and optionally <3 atom % of one or more elements from the group consisting of Ni, Cr, Ti, V, Mo, W, Nb, Ta, Co, Fe that promote wetting, wherein near-eutectic alloys encompass compositions having a liquidus temperature of <950° C., to a temperature above a liquidus temperature of the infiltrate alloy but below 1000° C., causing an infiltration of the intermediate product by the infiltrate alloy and a filling of pores of the intermediate product to an extent of at least 97%.

23. The method according to claim 22, wherein the eutectic or near-eutectic infiltrate alloy is a two-component alloy comprising a first component selected from the group consisting of Cu, Ag, and Au and a second component selected from the group consisting of Si, Y, Sc, and a rare earth metal.

24. The method according to claim 23, wherein the infiltrate alloy comprises the components Ag and Y.

25. The method according to claim 23, wherein the infiltrate alloy comprises the components Ag and Si.

26. The method according to claim 23, wherein the infiltrate alloy comprises the components Au and Si.

27. The method according to claim 23, wherein the infiltrate alloy comprises the components Cu and Y.

28. The method according to claim 23, wherein the infiltrate alloy comprises the components Cu and one or more elements of the rare earth metals.

29. The method according to claim 22, wherein the eutectic or near-eutectic infiltrate alloy is a multicomponent alloy having a solidus temperature of <800° C.

30. The method according to claim 22, wherein the eutectic or near-eutectic infiltrate alloy is a multicomponent alloy having a solidus temperature of <700° C.

31. The method according to claims 22, wherein the infiltrate alloy is a eutectic alloy.

32. The method according to claim 22, wherein the intermediate product comprises a binder based on polymer or wax.

33. The method according to claim 32, which comprises setting a proportion of binder from 1 to 20% by weight.

34. The method according to claim 32, which comprises, subsequent to shaping the intermediate product, heating the intermediate product to a temperature from 300° C. to 900° C. in a protective gas atmosphere to at least partially pyrolyze the binder.

35. The method according to claim 22, which comprises carrying out the infiltration at an elevated pressure p between 5 MPa and 200 MPa.

36. The method according to claim 35, which comprises carrying out the infiltration in a squeeze casting process.

37. The method according to claim 22, which comprises subjecting the infiltrated or hot-pressed intermediate product to a heat treatment step at a temperature in a range of 300° C.<T<900° C., forming phases corresponding to equilibrium.

38. The method according to claim 22, which comprises forming the composite material with 40 to 90% by volume of diamond having a mean particle size of from 5 to 300 μm, from 0.005 to 12% by volume of a silicon-carbon compound, from 7 to 49% by volume of an Ag-rich or Au-rich phase, and less than 5% by volume of a further phase, wherein a volume ratio of the Ag-rich or Au-rich phase to the silicon-carbon compound is greater than 4, and at least 60% of a surface of the diamond grains is covered by the silicon-carbon compound.

39. The method according to claim 38, wherein the silicon-carbon compound is SiC.

40. The method according to claim 22, which comprises forming the composite material with 40 to 90% by volume of diamond having a mean particle size of from 5 to 300 μm, from 0.001 to 5% by volume of a Y-carbon compound or rare earth metal-carbon compound, from 7 to 49% by volume of an Ag-rich, Au-rich, or Cu-rich phase, and less than 5% by volume of a further phase, wherein a volume ratio of the Ag-rich, Au-rich, or Cu-rich phase to the Y-carbon compound or rare earth metal-carbon compound is greater than 4, and at least 60% of a surface of the diamond grains are covered by the Y-carbon compound or rare earth metal-carbon compound.

41. The method according to claim 22, which further comprises forming the composite material as a heat sink.

42. A method of producing a diamond-containing composite material, which comprises the following steps:

mixing or milling an intermediate product containing from 40 to 90% by volume of diamond grains having a mean particle size from 5 to 300 μm and from 10 to 60% by volume of a eutectic or near-eutectic infiltrate alloy having a solidus temperature of <900° C. and comprising at least a metallic component with high thermal conductivity and including an element or an alloy from the group consisting of Cu, Ag, Au and at least one element from the group consisting of Si, Y, Sc, rare earth metals, and optionally <3 atom % of one or more elements from the group consisting of Ni, Cr, Ti, V, Mo, W, Nb, Ta, Co, Fe that promote wetting, wherein the near-eutectic infiltrate alloy encompasses compositions having a liquidus temperature of <950° C.;
filling a die of a hot press with the intermediate product, heating to a temperature T between 500° C. and 1000° C., and hot-pressing the intermediate product.

43. The method according to claim 42, wherein the eutectic or near-eutectic infiltrate alloy is a two-component alloy comprising a first component selected from the group consisting of Cu, Ag, and Au and a second component selected from the group consisting of Si, Y, Sc, and a rare earth metal.

44. The method according to claim 43, wherein the infiltrate alloy comprises the components Ag and Y.

45. The method according to claim 43, wherein the infiltrate alloy comprises the components Ag and Si.

46. The method according to claim 43, wherein the infiltrate alloy comprises the components Au and Si.

47. The method according to claim 43, wherein the infiltrate alloy comprises the components Cu and Y.

48. The method according to claim 43, wherein the infiltrate alloy comprises the components Cu and one or more elements of the rare earth metals.

49. The method according to claim 42, wherein the eutectic or near-eutectic infiltrate alloy is a multicomponent alloy having a solidus temperature of <800° C.

50. The method according to claim 42, wherein the eutectic or near-eutectic infiltrate alloy is a multicomponent alloy having a solidus temperature of <700° C.

51. The method according to claims 42, wherein the infiltrate alloy is a eutectic alloy.

52. The method according to claim 42, wherein the intermediate product comprises a binder based on polymer or wax.

53. The method according to claim 52, which comprises setting a proportion of binder from 1 to 20% by weight.

54. The method according to claim 52, which comprises, subsequent to shaping the intermediate product, heating the intermediate product to a temperature from 300° C. to 900° C. in a protective gas atmosphere to at least partially pyrolyze the binder.

55. The method according to claim 42, which comprises carrying out the infiltration at an elevated pressure p between 5 MPa and 200 MPa.

56. The method according to claim 55, which comprises carrying out the infiltration in a squeeze casting process.

57. The method according to claim 42, which comprises subjecting the infiltrated or hot-pressed intermediate product to a heat treatment step at a temperature in a range of 300° C.<T<900° C., forming phases corresponding to equilibrium.

58. The method according to claim 42, which comprises forming the composite material with 40 to 90% by volume of diamond having a mean particle size of from 5 to 300 μm, from 0.005 to 12% by volume of a silicon-carbon compound, from 7 to 49% by volume of an Ag-rich or Au-rich phase, and less than 5% by volume of a further phase, wherein a volume ratio of the Ag-rich or Au-rich phase to the silicon-carbon compound is greater than 4, and at least 60% of a surface of the diamond grains is covered by the silicon-carbon compound.

59. The method according to claim 58, wherein the silicon-carbon compound is SiC.

60. The method according to claim 42, which comprises forming the composite material with 40 to 90% by volume of diamond having a mean particle size of from 5 to 300 μm, from 0.001 to 5% by volume of a Y-carbon compound or rare earth metal-carbon compound, from 7 to 49% by volume of an Ag-rich, Au-rich, or Cu-rich phase, and less than 5% by volume of a further phase, wherein a volume ratio of the Ag-rich, Au-rich, or Cu-rich phase to the Y-carbon compound or rare earth metal-carbon compound is greater than 4, and at least 60% of a surface of the diamond grains are covered by the Y-carbon compound or rare earth metal-carbon compound.

61. The method according to claim 42, which further comprises forming the composite material as a heat sink.

Patent History
Publication number: 20060157884
Type: Application
Filed: Jan 20, 2004
Publication Date: Jul 20, 2006
Applicant:
Inventors: Arndt Ludtke (Reutte), Gerhard Leichtfried (Reutte)
Application Number: 10/548,723
Classifications
Current U.S. Class: 264/122.000; 264/128.000; 423/446.000
International Classification: D04H 1/00 (20060101); D04H 1/64 (20060101); B01J 3/06 (20060101); B29C 59/00 (20060101);