Composite materials and heat dissipation components

Abstract

A composite material comprising a metal phase and a plurality of particles dispersed in the metal phase. The plurality of particles are a carbon-based material, the metal phase includes a main element, a first element, and a second element, and a particle coating layer on each of the plurality of particles is a carbide of the second element. The main element is copper, the first element is a metal element having lower surface tension than copper, and the second element is at least one selected from the group consisting of beryllium, silicon, titanium, chromium, zirconium, niobium, hafnium, and tantalum. The content of the first element with respect to the total of the main element, the first element, and the second element is 0.25-10.0 at%, and the content of the second element with respect to the total of the main element, the first element, and the second element is 1.5-14.0 at%.

Description

[Technical field]

[0001] The present disclosure relates to a composite material and a heat dissipation member. This application claims priority to Japanese Patent Application No. 2020-053219, filed on March 24, 2020. The entire contents of the Japanese patent application are incorporated herein by reference. [Background technology]

[0002] Examples of heat dissipation members for semiconductor elements include heat spreaders and heat sinks. A composite material made of a metal and a carbon-based material such as diamond is known as a material suitable for such heat dissipation members. The composite material includes a metal phase and a plurality of particles dispersed in the metal phase. Each of the plurality of particles (each particle) is made of a carbon-based material such as diamond that has excellent thermal conductivity. The surface of each particle is provided with a coating layer made of carbide. The coating layer improves the wettability between the particle and the metal phase and suppresses the formation of voids in the composite material.

[0003] Examples of the metal phase of the composite material include metal phases described in Patent Documents 1 to 3. The metal phase in the composite material of Patent Document 1 is made of a eutectic alloy of silver (Ag) and copper (Cu). Since the eutectic alloy contains about 72 mass% Ag, it can be said to be an alloy mainly composed of Ag. The metal phase in the composite material of Patent Document 2 is mainly composed of Ag. The metal phase in the composite material of Patent Document 3 is mainly composed of Cu. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-197153 A [Patent Document 2] International Publication No. 2016 / 035795 [Patent Document 3] International Publication No. 2019 / 163721 Summary of the Invention

[0005] The composite material of the present disclosure comprises: A metallic phase; a plurality of particles dispersed in the metal phase; Each of the plurality of particles has a coating layer covering a surface of the each of the particles, the plurality of particles being a carbon-based material; the metal phase includes a main element, a first element, and a second element; the coating layer is a carbide of the second element, The main element is copper, the first element is a metal element having a surface tension lower than that of copper; the second element is at least one selected from the group consisting of beryllium, silicon, titanium, chromium, zirconium, niobium, hafnium, and tantalum; a content of the first element in the total of the main element, the first element, and the second element is 0.25 atomic % or more and 10.0 atomic % or less; The content of the second element in the total of the main element, the first element, and the second element is 1.5 atomic % or more and 14.0 atomic % or less.

[0006] The heat dissipation member of the present disclosure includes: A substrate made of a composite material of the present disclosure; and a copper layer covering at least a portion of a surface of the substrate. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a cross section of a composite material according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram of the surface of a particle contained in the composite material shown in FIG. [Diagram 3] FIG. 3 is a schematic diagram of a heat dissipation member according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Problem that this disclosure aims to solve] From the viewpoint of lowering the linear expansion coefficient of the composite material, it is preferable that the main component of the metal phase of the composite material is Cu rather than Ag, since the linear expansion coefficient of Cu is lower than that of Ag. In addition, Cu has the advantages of being lighter and less expensive than Ag. Therefore, a composite material having a metal phase mainly composed of Cu is desired.

[0009] Here, the composite material used in the heat dissipation member may be required to have excellent thermal conductivity as well as heat resistance at high temperatures. For example, when brazing a ceramic frame-shaped member to a substrate made of a composite material, a brazing material made of Ag-Cu alloy is used. It is required that the composite material does not deform at the temperature at which the brazing material melts. From this point of view, the composite material of Patent Document 1 having a metal phase mainly composed of Ag-Cu alloy has room for improvement in terms of heat resistance. This is because the melting point of the Ag-Cu alloy constituting the metal phase is close to the melting point of the brazing material.

[0010] On the other hand, the melting point of Cu is higher than that of Ag-Cu alloy, so that composite materials having a metal phase mainly composed of Cu have excellent heat resistance. However, even if the carbon-based material particles have a coating layer that improves the wettability between the particles and the metal phase, the wettability between the carbon-based material particles and Cu is poor. Therefore, when multiple particles made of carbon-based material are combined with Cu, multiple voids are likely to be formed in the composite material. These voids may reduce the thermal conductivity of the composite material.

[0011] In view of the above, an object of the present disclosure is to provide a composite material having excellent thermal conductivity and heat resistance, and another object of the present disclosure is to provide a heat dissipation member having excellent heat dissipation properties and heat resistance. [Effects of this disclosure]

[0012] The composite material of the present disclosure has excellent thermal conductivity and heat resistance. The heat dissipation member of the present disclosure has excellent heat dissipation properties and heat resistance.

[0013] [Description of the embodiments of the present disclosure] The composite material is obtained by combining a plurality of particles of a carbon-based material with a molten metal that is a raw material of a metal phase. The present inventors have intensively studied a configuration that improves the wettability between the carbon-based material particles and the metal phase in a composite material having a metal phase mainly composed of Cu. As a result, the present inventors have found that the wettability between the carbon-based material particles and the metal phase can be improved by including an element having a smaller surface tension than Cu in the molten metal of the metal phase. In a molten metal containing a first element having a smaller surface tension than Cu, the first element is likely to be concentrated on the surface of the molten metal in contact with the particles. It is believed that this first element improves the wettability between the carbon-based material particles and the molten metal. Based on this knowledge, the present inventors have completed the composite material according to this embodiment. First, the embodiments of the present disclosure will be listed and described. Here, in this specification, an aggregate of a plurality of particles of a carbon-based material is called a "carbon-based powder".

[0014] <1> The composite material according to this embodiment is A metallic phase; a plurality of particles dispersed in the metal phase; Each of the plurality of particles is a composite material having a coating layer covering a surface of the each particle, the plurality of particles being a carbon-based material; the metal phase includes a main element, a first element, and a second element; the coating layer is a carbide of the second element, The main element is copper, the first element is a metal element having a surface tension lower than that of copper; the second element is at least one selected from the group consisting of beryllium, silicon, titanium, chromium, zirconium, niobium, hafnium, and tantalum; a content of the first element in the total of the main element, the first element, and the second element is 0.25 atomic % or more and 10.0 atomic % or less; The content of the second element in the total of the main element, the first element, and the second element is 1.5 atomic % or more and 14.0 atomic % or less.

[0015] Here, the main element refers to a metal element that is the main component of the metal phase, that is, a metal element that occupies the majority of the metal phase.

[0016] the above <1> The composite material includes the following components: "Metal phase and a plurality of particles dispersed in the metal phase; Each of the plurality of particles is a composite material having a coating layer covering a surface of the each particle, each said particle being a carbon-based material; The components other than carbon are: The first element is 0.25 atomic percent or more and 10.0 atomic percent or less. Contains 1.5 atomic % or more and 14.0 atomic % or less of a second element, The balance is copper and unavoidable impurities. the first element is a metal element having a surface tension lower than that of copper; The second element is at least one selected from the group consisting of beryllium, silicon, titanium, chromium, zirconium, niobium, hafnium, and tantalum.

[0017] The composite material according to this embodiment has excellent thermal conductivity. Particles of carbon-based materials such as diamond have excellent thermal conductivity. In addition, Cu, which is the main component of the metal phase, also has excellent thermal conductivity. Therefore, the composite material according to this embodiment has excellent thermal conductivity. Furthermore, a coating layer made of a carbide of the second element is provided on the surface of each of the multiple particles in the composite material according to this embodiment. This coating layer improves the wettability between the particles and the molten metal phase when the composite material is produced. The metal phase in the composite material also contains a first element having a smaller surface tension than Cu. This first element is concentrated on the surface of the molten metal phase when the composite material is produced, improving the wettability between the molten metal phase and the particles. Due to the improvement in wettability by the coating layer and the improvement in wettability by the first element, voids are unlikely to form in the composite material. Therefore, the composite material according to this embodiment has excellent thermal conductivity.

[0018] The composite material according to this embodiment has excellent heat resistance. The metal phase in the composite material according to the present embodiment is mainly composed of Cu. Cu has a higher melting point than Ag alloy. Therefore, when the composite material is brazed to ceramics or the like, the composite material is unlikely to deform at temperatures near the melting point of the brazing material.

[0019] The composite material according to this embodiment has a small linear expansion coefficient. The linear expansion coefficient of Cu is smaller than that of Ag. Therefore, the linear expansion coefficient of the composite material of the present embodiment having a metal phase mainly composed of Cu is likely to be lower than that of a composite material having a metal phase mainly composed of Ag. The linear expansion coefficient of the composite material having a metal phase mainly composed of Cu is close to that of a heat generating body such as a semiconductor element. Therefore, peeling between the composite material and the heat generating body due to the difference in linear expansion coefficient is likely to be suppressed.

[0020] The composite material according to this embodiment is inexpensive and lightweight. The metal phase in the composite material according to the present embodiment contains Cu as a main element. Cu is lighter and less expensive than Ag. Therefore, the composite material according to the present disclosure is lighter and less expensive than a composite material mainly composed of Ag.

[0021] <2> As one embodiment of the composite material according to this embodiment, The carbon-based material may be diamond.

[0022] Diamond has extremely good thermal conductivity. Therefore, if the particles dispersed in the metal phase are diamond, the thermal conductivity of the composite material is improved. Diamond powders with various particle sizes are commercially available, and diamond powders are easily available.

[0023] <3> As one embodiment of the composite material according to this embodiment, The first element may be at least one element selected from the group consisting of silver, magnesium, aluminum, tin, zinc, and manganese.

[0024] The surface tension of molten Ag, magnesium (Mg), aluminum (Al), tin (Sn), zinc (Zn), and manganese (Mn) is smaller than that of molten Cu. <3> The metals listed in are readily available.

[0025] <4> the above <3> As one embodiment of the composite material described in The first element may be silver.

[0026] Ag has excellent wettability with particles having a coating layer, and therefore Ag is suitable as the first element contained in the metal phase.

[0027] <5> As one embodiment of the composite material according to this embodiment, The second element may be titanium.

[0028] The second element is at least one selected from the group consisting of beryllium (Be), silicon (Si), titanium (Ti), chromium (Cr), zirconium (Zr), niobium (Nb), hafnium (Hf), and tantalum (Ta). Among these candidates for the second element, Ti is easily available. Titanium carbide also easily improves the wettability of the molten metal phase to the particles made of carbon-based materials.

[0029] <6> As one embodiment of the composite material according to this embodiment, The content of the plurality of particles may be 40% by volume or more and 80% by volume or less.

[0030] If the content of the carbon-based powder, which has a higher thermal conductivity than the metal phase, is within the above range, a composite material with excellent thermal conductivity can be obtained. Also, if the amount of carbon-based powder is not too much during the production of the composite material, the molten metal of the metal phase can easily infiltrate between the particles of the carbon-based powder. Therefore, a composite material with few voids and excellent thermal conductivity can be obtained.

[0031] <7> As one embodiment of the composite material according to this embodiment, The plurality of particles includes a plurality of fine particles and a plurality of coarse particles, Each of the plurality of fine particles has a particle size of less than 30 μm; Each of the plurality of coarse particles has a particle size of 30 μm or more; The volume ratio of the fine particles to all the particles may be 20 volume % or more and 50 volume % or less.

[0032] If the carbon-based powder is a mixture of a plurality of fine particles and a plurality of coarse particles, the content of the carbon-based powder in the composite material is likely to be high. In particular, if the volume ratio of the plurality of fine particles to all the particles is within the above range, the content of the carbon-based powder in the composite material is likely to be high.

[0033] <8> The heat dissipation member according to this embodiment is the above <1> from <7> A substrate made of the composite material according to any one of the preceding claims, and a copper layer covering at least a portion of a surface of the substrate.

[0034] The heat dissipation member according to this embodiment has excellent heat dissipation properties. The substrate of the heat dissipation member according to this embodiment is made of the composite material according to the above embodiment. The carbon-based material particles contained in the composite material and Cu, which is the main component of the metal phase, have excellent thermal conductivity. Therefore, the heat dissipation member according to this embodiment, which includes a substrate made of the composite material according to the above embodiment, can effectively dissipate heat from a heat generating body such as a semiconductor element.

[0035] The heat dissipation member according to this embodiment is suitable as a heat dissipation member for semiconductor elements. The composite material substrate provided in the heat dissipation member according to this embodiment has a linear expansion coefficient intermediate between that of the carbon-based material and Cu. The linear expansion coefficient of this substrate is close to that of the semiconductor element and the insulating substrate of the semiconductor element. Therefore, when the semiconductor element is used, peeling between the semiconductor element and the heat dissipation member caused by the difference in linear expansion coefficient is suppressed.

[0036] The heat dissipation member according to this embodiment can be easily joined to a heat generating body such as a semiconductor element. The heat dissipation member according to this embodiment includes a copper layer on at least a portion of the surface of the substrate. The copper atoms, which are the main component of the copper layer, easily bond with the copper atoms, which are the main component of the metal phase of the substrate, so that the copper layer is easily bonded to the substrate of the composite material. The copper layer also smoothes the surface of the substrate. This copper layer is also easily bonded to a heat generating body such as a semiconductor element. Therefore, when the heat dissipation member and the heat generating body are soldered together, voids are unlikely to form between the heat dissipation member and the heat generating body. Therefore, by disposing the copper layer on the heat generating body, the heat generating body can be soldered well to the heat dissipation member.

[0037] [Details of the embodiment of the present disclosure] A composite material and a heat dissipation member according to an embodiment of the present disclosure will be described below with reference to Fig. 1 to Fig. 3. Note that the present invention is not limited to the exemplary embodiments, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0038] <Embodiment 1> ≪Composite materials≫ The composite material 1 of the present embodiment includes a metal phase 2 and a plurality of particles 3 dispersed in the metal phase 2. As shown in Fig. 2, the surface of each of the plurality of particles 3 (each of the particles 3) is provided with a coating layer 4. Each component of the composite material 1 will be described in detail below.

[0039] (metallic phase) Metal phase 2 contains Cu as the main element. A main element is a metal element that is the main component of metal phase 2, that is, a metal element that occupies the majority of metal phase 2. The thermal conductivity of Cu is approximately 400 W / m K. Therefore, metal phase 2, which is mainly composed of Cu, contributes to improving the thermal conductivity of composite material 1.

[0040] The metal phase 2 includes a first element and a second element in addition to Cu. The first element is a metal element having a surface tension lower than that of Cu. That is, the surface tension of the molten metal of the first element is lower than that of the molten metal of Cu. The surface tension of the metal element is publicly known. A specific example of the first element is at least one element selected from the group consisting of Ag, Mg, Al, Sn, Zn, and Mn. The first element is concentrated on the surface of the molten metal of the metal phase 2 during the production of the composite material 1. The first element concentrated on the surface of the molten metal improves the wettability between the molten metal in contact with the particles 3 and the particles 3.

[0041] The second element is at least one selected from the group consisting of Be, Si, Ti, Cr, Zr, Nb, Hf, and Ta. A predetermined amount of the second element is contained in the raw material of the composite material 1 when the composite material 1 is produced. Most of the second element in the raw material is consumed in the formation of the coating layer 4 of the particle 3. Therefore, the amount of the second element contained in the metal phase 2 is very small.

[0042] The contents of the first element and the second element in the entire composite material 1 will be described later.

[0043] (particle) ·Material The particles 3 are made of a carbon-based material. The carbon-based material is preferably at least one selected from the group consisting of diamond, graphite, carbon nanotubes, and carbon fibers. Diamond has substantially no anisotropy in thermal conduction, and typically has a high thermal conductivity of 1000 W / m·K or more. Diamond powders of various particle sizes are commercially available, and diamond powder is easy to obtain. In these respects, the composite material 1 containing diamond is easy to use as a material for heat dissipation members, and is also easy to manufacture.

[0044] Graphite is soft and has good workability. Therefore, composite material 1 containing graphite has good workability. The thermal conductivity along the axial direction of carbon nanotubes may be higher than the thermal conductivity along the axial direction of diamond. Therefore, composite material 1 containing carbon nanotubes is expected to have better thermal conductivity. Carbon fibers have good mechanical strength. Therefore, composite material 1 containing carbon fibers has good mechanical strength.

[0045] Composite material 1 containing multiple different types of carbon-based materials combines the effects of each carbon-based material. For example, composite material 1 containing mainly diamond as carbon-based materials and partially containing graphite is expected to have excellent thermal conductivity and be easy to process, such as by cutting.

[0046] ·Content The content of all particles 3 in the composite material 1, i.e., the content of the carbon-based powder, may be, for example, 40% by volume or more and 85% by volume or less. If the content is 40% by volume or more, the composite material 1 contains many particles 3 with excellent thermal conductivity. Therefore, the thermal conductivity of the composite material 1 is improved. In addition, the linear expansion coefficient of the composite material 1 is likely to be smaller than that of Cu. If the content is 85% by volume or less, the metal phase 2 is likely to spread into the gaps between the particles 3 during the preparation of the composite material 1. The lower limit of the content of the particles 3 may be, for example, 45% by volume, further 50% by volume, 55% by volume, or 60% by volume. In addition, the upper limit of the content may be, for example, 80% by volume, further 75% by volume or less.

[0047] The content of the plurality of particles 3 in the composite material 1 can be obtained, for example, as follows. First, the volume of the composite material 1 is obtained by Archimedes' method. Next, the composite material 1 is dissolved in dilute nitric acid to separate the carbon-based powder. The mass of the carbon-based powder is measured, and the volume of the carbon-based powder is calculated based on the theoretical density of the carbon-based material that constitutes the carbon-based powder. Then, the volume of the carbon-based powder is divided by the volume of the composite material 1 to obtain the content of the plurality of particles 3 in the composite material 1.

[0048] Size The average particle size of the particles 3 in the composite material 1 is preferably, for example, 10 μm or more and 120 μm or less. The average particle size of the particles 3 may be 15 μm or more, or even 20 μm or more. The average particle size may be 100 μm or less, or even 90 μm or less, 80 μm or less, 70 μm or less, or 60 μm or less.

[0049] The average particle size of the particles 3 is determined from the circle-equivalent diameter obtained by observing the cross section of the composite material 1. Specifically, the circle-equivalent diameter is determined for k or more particles 3 in the cross section of the composite material 1. The average of the circle-equivalent diameters of the k particles is the average particle size of the particles 3. k is 10 or more. k is preferably 20 or more, and more preferably 50 or more. Here, to determine the circle-equivalent diameter, first, a SEM (Scanning Electron Microscope) image of the cross section of the composite material 1 is obtained, and the cross-sectional area of ​​the particles 3 is determined by a binarization process. The diameter of a circle having the same cross-sectional area as that cross-sectional area is the circle-equivalent diameter. The threshold value of the binarization process is adjusted so that each particle 3 can be clearly identified.

[0050] The carbon-based powder may be a mixture of a plurality of fine particles 31 and a plurality of coarse particles 32. By producing the composite material 1 using the carbon-based powder containing fine particles and coarse particles, it is easy to obtain a composite material 1 having a high relative density.

[0051] In this specification, fine particles 31 are particles 3 having an equivalent circle diameter of less than 30 μm obtained by observing a cross section of a composite material 1. The average particle diameter of the fine particles 31 is preferably 10 μm or more and 25 μm or less. The average particle diameter is the average of the equivalent circle diameters of n fine particles 31. n is 10 or more. n is preferably 20 or more, and more preferably 50 or more.

[0052] On the other hand, the coarse particles 32 in this specification are particles 3 having an equivalent circle diameter of 30 μm or more obtained by observing a cross section of the composite material 1. The average particle diameter of the coarse particles 32 is preferably 80 μm or more and 120 μm or less. The average particle diameter is the average of the equivalent circle diameters of m coarse particles 32. m is 10 or more. m is preferably 20 or more, and more preferably 50 or more.

[0053] The volume ratio of the fine particles 31 to all the particles 3 of the plurality of particles 3 is preferably 20 volume % or more and 50 volume % or less. If the volume ratio of the fine particles 31 to the coarse particles 32 is within the above range, a sufficient number of fine particles 31 are likely to be arranged between adjacent coarse particles 32. As a result, the volume of the particles 3 in the composite material 1 is increased, and the thermal conductivity of the composite material 1 is likely to be increased. The volume ratio of the fine particles 31 to all the particles 3 is more preferably 25 volume % or more and 40 volume % or less.

[0054] (covering layer) The coating layer 4 covers at least a portion, typically substantially the entire surface, of each of the plurality of particles 3. This coating layer 4 is a carbide of the second element. The coating layer 4 improves the wettability of the particles 3 with the molten metal of the metal phase 2 during production of the composite material 1. In particular, the coating layer 4 made of titanium carbide contributes to improving the wettability of the particles 3 with the molten metal of the metal phase 2.

[0055] The thermal conductivity of the coating layer 4 is lower than that of Cu and carbon-based materials. Therefore, the coating layer 4 is preferably thin within a range in which the above-mentioned wettability improvement effect can be obtained. The thickness of the coating layer 4 is adjusted by the amount of the second element added when the composite material 1 is produced. The thickness of the coating layer 4 tends to be thinner as the amount of the second element added decreases.

[0056] (Content of first element in composite material) The content of the first element in the composite material 1 is 0.25 atomic % or more and 10.0 atomic % or less. When the content of the first element is 0.25 atomic % or more, the effect of improving wettability by the first element can be sufficiently obtained. Therefore, the composite material 1 having the content of the first element of 0.25 atomic % or more has excellent thermal conductivity. When the content of the first element is 10.0 atomic % or less, the decrease in heat resistance of the composite material 1 is suppressed. The content of the first element in the composite material 1 of this embodiment is more preferably 0.5 atomic % or more and 4.5 atomic % or less.

[0057] In this specification, the content of the first element in the composite material 1 is determined by the following formula. {(number of atoms of the first element) / (number of atoms of the main element + number of atoms of the first element + number of atoms of the second element)} x 100

[0058] The atomic number of each element in the composite material 1 is measured as follows. First, the composite material 1 is dissolved in dilute nitric acid, and the solution is filtered to separate the particles 3 from the rest. The concentration of the dilute nitric acid is about 70%. Next, the solution containing the metal phase 2 and the coating layer 4 other than the particles 3 is analyzed by ICP atomic emission spectrometry (ICP atomic emission spectrometry). The atomic number of each element obtained by the analysis is then substituted into the above formula to determine the content (atomic %) of the first element in the composite material 1.

[0059] (Content of secondary elements in composite materials) The content of the second element in the composite material 1 is 1.5 atomic % or more and 14.0 atomic % or less. If the content of the second element is 1.5 atomic % or more, it can be said that the coating layer 4, which is a carbide of the second element, is sufficiently present on the surface of each particle 3. Since the coating layer 4 improves the wettability between the metal phase 2 and the particle 3, the composite material 1 having the content of the second element of 1.5 atomic % or more has excellent thermal conductivity. On the other hand, if the content of the second element is 14.0 atomic % or less, it can be said that the coating layer 4 present on the surface of each particle 3 is not too thick. Therefore, the composite material 1 having the content of the second element of 14.0 atomic % or less has excellent thermal conductivity. The content of the second element is more preferably 2.5 atomic % or more and 10.0 atomic % or less.

[0060] In this specification, the content of the second element in the composite material 1 is calculated by the following formula. The method for calculating the number of atoms of each element is the same as the method for calculating the number of atoms of each element when calculating the content of the first element. {(number of atoms of the second element) / (number of atoms of the main element + number of atoms of the first element + number of atoms of the second element)} x 100

[0061] (others) The composite material 1 may contain a third element to the extent that the thermal conductivity and heat resistance of the composite material 1 are not deteriorated. The third element is sulfur (S), phosphorus (P), nickel (Ni), cobalt (Co), iron (Fe), etc. These elements are elements that may be mixed in during the preparation of the composite material 1. In this specification, the content of the third element in the composite material 1 is calculated in atomic ratio by the following formula. {(number of atoms of the third element) / (number of atoms of the main element + number of atoms of the first element + number of atoms of the second element + number of atoms of the third element)} x 100

[0062] The content of the third element is 0 atomic % or more and 2.0 atomic % or less. This content of the third element does not deteriorate the thermal conductivity and heat resistance of the composite material 1. The composite material of the present embodiment including the third element can also be specified as follows. "Metal phase and a plurality of particles dispersed in the metal phase; Each of the plurality of particles is a composite material having a coating layer covering a surface of the each particle, the plurality of particles being a carbon-based material; the metal phase includes a main element, a first element, a second element, and a third element; the coating layer is a carbide of the second element, The main element is copper, the first element is a metal element having a surface tension lower than that of copper; the second element is at least one selected from the group consisting of beryllium, silicon, titanium, chromium, zirconium, niobium, hafnium, and tantalum; the third element is at least one selected from the group consisting of sulfur, phosphorus, nickel, cobalt, and iron; a content of the first element in the total of the main element, the first element, the second element, and the third element is 0.25 atomic % or more and 10.0 atomic % or less; a content of the second element in the total of the main element, the first element, the second element, and the third element is 1.5 atomic % or more and 14.0 atomic % or less; A composite material in which the content of the third element in the total of the main element, the first element, the second element, and the third element is 0 atomic % or more and 2.0 atomic % or less.

[0063] Here, the composite material in the above parentheses includes the following components: "Metal phase and a plurality of particles dispersed in the metal phase; Each of the plurality of particles is a composite material having a coating layer covering a surface of the each particle, each said particle being a carbon-based material; The components other than carbon are: The first element is 0.25 atomic percent or more and 10.0 atomic percent or less. Secondary elements: 1.5 atomic percent or more and 14.0 atomic percent or less; Contains 0 atomic % or more and 2.0 atomic % or less of a third element; The balance is copper and unavoidable impurities. the first element is a metal element having a surface tension lower than that of copper; the second element is at least one selected from the group consisting of beryllium, silicon, titanium, chromium, zirconium, niobium, hafnium, and tantalum; The third element is at least one selected from the group consisting of sulfur, phosphorus, nickel, cobalt, and iron.

[0064] (Thermal Conductivity of Composite Materials) The thermal conductivity of the composite material 1 of this embodiment is, for example, 600 W / m·K or more. The higher the thermal conductivity of the composite material 1, the more preferable it is as a material for heat dissipation components of semiconductor elements, etc. Therefore, the thermal conductivity of the composite material 1 is more preferably 650 W / m·K or more, 660 W / m·K or more, or 700 W / m·K or more.

[0065] (Linear expansion coefficient of composite materials) As described above, the composite material 1 of the present embodiment has a linear expansion coefficient intermediate between that of the carbon-based material and that of Cu. Quantitatively, the linear expansion coefficient of the composite material 1 is 4×10 -6 / K or more 15×10 -6 / K or less. The higher the content of particles 3 in composite material 1, the smaller the linear expansion coefficient of composite material 1 tends to be. By adjusting the content of particles 3, the linear expansion coefficient of composite material 1 can be adjusted to 4.5×10 -6 / K or more 13×10 -6 / K or less, or 4.5×10 -6 / K or more 10×10 -6 / K or less. If the difference between the linear expansion coefficient of the composite material 1 and the linear expansion coefficient of the heating element becomes small, the composite material 1 bonded to the heating element with a brazing material or the like becomes less likely to peel off from the heating element.

[0066] (Relative density of composite material) In the composite material 1 of this example, the wettability between the metal phase 2 and the particles 3 is good. Therefore, the composite material 1 of this example has few pores, and the relative density of the composite material 1 is high. The relative density of the composite material 1 of this example is, for example, 90% or more. The higher the relative density of the composite material 1, the less likely a decrease in the thermal conductivity of the composite material 1 caused by pores occurs. Therefore, the relative density of the composite material 1 is preferably 95% or more, further preferably 96% or more, 97% or more, 98% or more, or 99% or more.

[0067] The relative density is a value obtained by dividing the actual density of composite material 1 by the theoretical density of composite material 1. The actual density of composite material 1 is obtained by dividing the mass of composite material 1 by its volume. The volume of composite material 1 is obtained by the Archimedes method or the like. Meanwhile, in this specification, the theoretical density of composite material 1 is obtained according to the following steps 1 to 5. Step 1: Calculate the volume of composite material 1 using Archimedes' method. Step 2: Determine the weight of each element contained in composite material 1. First, composite material 1 is dissolved in dilute nitric acid, and the weight of particles 3 separated from composite material 1, i.e., the weight of the carbon-based powder, is measured. Also, the weight of each element contained in the dilute nitric acid solution is determined. The weight of each element contained in the solution is determined from the number of atoms of each element obtained by ICP emission analysis of the solution. Step 3: The weight of each element obtained in step 2 is divided by the theoretical density of each element to obtain the volume of each element in composite material 1. Furthermore, the volume ratio of each element in composite material 1 is calculated based on the volume of each element. Step 4: Calculate the volume of each element that fills the volume of composite material 1 calculated in step 1 with the volume ratio calculated in step 3. Step 5: Multiply the volume of each element found in step 4 by the theoretical density of each element to calculate the weight of each element in composite material 1. The total weight of each element divided by the volume of composite material 1 found in step 1 is the theoretical density of composite material 1.

[0068] (Application) The composite material 1 of the present embodiment, which has excellent thermal conductivity, is suitable as a material for heat dissipation members. In particular, the composite material 1, which has excellent compatibility of the linear expansion coefficient with semiconductor elements and their peripheral parts, is suitable as a material for heat dissipation members for semiconductor elements. Examples of semiconductor devices that include heat dissipation members made of the composite material 1 of the present embodiment include high-frequency power devices such as LDMOS (Laterally Diffused Metal Oxide Semiconductor). Other examples of semiconductor devices include semiconductor laser devices, light-emitting diode devices, central processing units of various computers, graphics processing units, high electron mobility transistors (HEMTs), chip sets, memory chips, etc.

[0069] (effect) The composite material 1 of the present embodiment is lightweight and inexpensive. The metal phase 2 in the composite material 1 is mainly composed of Cu. Cu is lighter and less expensive than Ag. Therefore, the composite material 1 of the present embodiment is lighter and less expensive than a composite material mainly composed of Ag.

[0070] The composite material 1 of the present embodiment is excellent in thermal conductivity and heat resistance, the effects of which will be described in detail in Test Examples 1 and 2 described later.

[0071] <Manufacturing method of composite materials> The composite material of this embodiment can be obtained, for example, by the infiltration method described below. First, a raw material powder containing a carbon-based powder is filled into a mold. The raw material powder may be, for example, only a carbon-based powder, or may be a mixed powder of a carbon-based powder and a powder containing a second element that is a raw material for the coating layer 4.

[0072] Next, a copper material that will become the metal phase 2 is placed on the raw material powder. The copper material may be a powder or small pieces. The copper material contains Cu, a first element, and a second element. Here, the raw material powder and the copper material may be mixed and filled into the mold.

[0073] The molding die in which the raw material powder and the copper material are placed is heated to melt the copper material, so that the raw material powder is infiltrated with the molten copper material and combined with the molten copper material.

[0074] The infiltration temperature, i.e., the heating temperature of the raw material powder and the copper material, is equal to or higher than the melting point of Cu, which is the temperature at which the copper material can melt. For example, the infiltration temperature is equal to or higher than 1100°C, or even equal to or higher than 1150°C. However, if the infiltration temperature is too high, Cu and other elements contained in the copper material are likely to be oxidized during the heating process. Therefore, the infiltration temperature is preferably equal to or lower than 1300°C.

[0075] The time for which the infiltration temperature is maintained varies depending on the size of the composite material 1. For example, the time for which the infiltration temperature is maintained is about 10 minutes or more and 120 minutes or less.

[0076] The atmosphere during infiltration is a vacuum atmosphere of 1 Pa or less, a reducing atmosphere, or an inert atmosphere. By using the above vacuum atmosphere, reducing atmosphere, or inert atmosphere, oxidation of Cu and the like is reduced. The pressure of the vacuum atmosphere is 0.1 Pa or less, and further 0.01 Pa or less. The inert atmosphere includes an inert gas atmosphere such as argon or nitrogen. The reducing atmosphere includes a hydrogen atmosphere, or a mixed atmosphere of hydrogen and an inert gas. In any atmosphere, it is preferable that the oxygen concentration is low.

[0077] During infiltration, the molten metal takes in the second element contained in the raw material powder and comes into contact with the particles 3, forming a coating layer 4 on the surface of the particles 3. The coating layer 4 improves the wettability between the particles 3 and the molten metal. In addition, the first element is concentrated on the surface of the molten metal in contact with the particles 3, and the concentrated first element improves the wettability between the particles 3 and the molten metal. As a result, the particles 3 and the molten metal are combined. At that time, voids are unlikely to form near the particles 3.

[0078] After infiltration of the metal phase 2, the raw material in the mold is cooled. By cooling the raw material, a composite material 1 is obtained in which a plurality of particles 3 having a coating layer 4 are dispersed in the metal phase 2 mainly composed of Cu.

[0079] <Embodiment 2> <Heat dissipation materials> The heat dissipation member 5 shown in Fig. 3 is an example of a heat dissipation member using the composite material 1 according to this embodiment. The heat dissipation member 5 in Fig. 3 includes a substrate 6 and a copper layer 7. The substrate 6 is made of the composite material 1. The copper layer 7 is provided on at least a portion of the substrate 6. In this example, the copper layer 7 is provided on each of a first surface and a second surface of the substrate 6.

[0080] Copper atoms, which are the main component of the copper layer 7, easily bond with copper atoms, which are the main component of the metal phase 2 in the composite material 1 constituting the substrate 6, so that the copper layer 7 is unlikely to peel off from the substrate 6. In addition, the copper layer 7 smoothes the surface of the heat dissipation member 5, so that when the heat dissipation member 5 including the copper layer 7 is solder-joined to a heat generating body such as a semiconductor element, voids are unlikely to occur between the heat dissipation member 5 and the heat generating body. Therefore, heat is easily transferred from the heat generating body to the heat dissipation member 5, and the temperature rise of the heat generating body is suppressed.

[0081] The copper layer 7 is formed by bonding a copper foil to the surface of the base material 6 with a brazing material such as an Ag-Cu alloy. Alternatively, the copper layer 7 may be formed by vapor deposition or Cu plating. Further on the surface A plating layer may be provided, the material of which may be, for example, nickel (Ni).

[0082] <Test Example 1> In Test Example 1, the effects of the contents of the first element and the second element in the composite material on the thermal conductivity and heat resistance of the composite material were examined.

[0083] <Sample Preparation> In Test Example 1, composite materials of Sample No. 1 to Sample No. 28, in which the particles were diamond, the first element was Ag, and the second element was Ti, were produced. The specific production procedure was as follows.

[0084] First, a raw material powder of diamond powder containing Ti as a second element was prepared. A copper material containing Ag as a first element and Ti as a second element was also prepared. The raw material powder was filled into a carbon mold, and the copper material was filled on top of the filling. Next, the raw material powder and the copper material were heat-treated together with the mold in an argon atmosphere to combine the diamond powder with the molten metal. The heat treatment temperature was anywhere between 1100°C and 1200°C, and the heat treatment time was anywhere between 10 minutes and 120 minutes. After the heat treatment, the mold was cooled to obtain a composite material.

[0085] ≪Measurement items≫ The structures and properties of the composite materials of Samples No. 1 to 28 obtained by the above-mentioned preparation procedure were measured. The results are shown in Table 1. The composite materials of the samples with "*" or "**" after the sample number in Table 1 satisfy the requirements of the composite material 1 according to the embodiment 1. The measurement items in Test Example 1 are as follows.

[0086] (Thermal Conductivity) The thermal conductivity (W / m K) of each composite material was measured. Thermal conductivity was measured at room temperature by the flash method using a commercially available measuring device (NETZSCH LFA467). The measurement conditions were in accordance with ASTM E1461-13 "Standard Test Method for Thermal Diffusivity by the Flash Method." Here, the thermal conductivity of samples No. 22 and 23 was not measured because the diamond particles were not infiltrated with the molten metal.

[0087] (Heat resistance) The heat resistance of each composite sample was examined. Specifically, each composite sample was heat-treated at 800°C for 30 minutes, and the surface of the composite was visually inspected to see if any traces of melting were present. Composite materials with traces of melting were composite materials with insufficient heat resistance. Composite materials without traces of melting were composite materials with excellent heat resistance. In Table 1, insufficient heat resistance is indicated by "no good," and excellent heat resistance is indicated by "good." The heat resistance of samples No. 22 and 23, in which the diamond particles were not infiltrated with the molten metal, was not examined.

[0088] (average particle size) The cross section of the composite material of each sample was observed to investigate the average particle size of the diamond particles contained in the composite material. Specifically, SEM photographs of the cross section of the composite material were taken, and each diamond particle was identified by image analysis, while the equivalent circle diameter of each diamond particle was determined. Diamond particles with an equivalent circle diameter of less than 30 μm were classified as fine particles, and diamond particles with an equivalent circle diameter of 30 μm or more were classified as coarse particles. The average particle size of fine particles is the average value of the equivalent circle diameters of diamond particles judged to be fine particles. The average particle size of coarse particles is the average value of the equivalent circle diameters of diamond particles judged to be coarse particles. Here, diamond particles with a cross-sectional area of ​​3 μm in the SEM photograph were classified as fine particles. 2 The following diamond particles were not included in the calculation of the average fines value:

[0089] (Volume ratio of fine particles to coarse particles) The volume ratio (volume %) of fine particles and coarse particles was obtained from SEM photographs. Specifically, the total area of ​​fine particles and the total area of ​​coarse particles in the SEM photographs were obtained, and the area ratio of fine particles to coarse particles was regarded as the volume ratio of fine particles to coarse particles. For example, when the total area of ​​fine particles obtained from the SEM photographs is 3000 μm 2 , the total area of ​​the coarse particles is 7000 μm 2 In this case, the volume fraction of fine particles in all particles is 30 volume %, and the volume fraction of coarse particles is 70 volume %.

[0090] (Particle content in composite material) The particle content (%) in the composite material was determined as follows. First, the volume of the composite material of each sample was determined by Archimedes' method. Next, the composite material was dissolved in 70% dilute nitric acid, and the solution was filtered to separate the diamond powder. The mass of the separated diamond powder was measured, and the volume of the diamond powder was calculated based on the theoretical density of diamond. The volume of the diamond powder was then divided by the volume of the composite material to obtain the particle content in the composite material.

[0091] (Ag content in composite material) The Ag content (atomic %) in the metal phase and coating layer was measured. The content of Ag, the first element, was determined by ICP emission spectroscopy of a solution of the composite material dissolved in dilute nitric acid. The Ag content is the ratio of the number of Ag atoms to the total number of Cu, Ag, and Ti atoms in the solution.

[0092] (Ti content in composite material) The Ti content (atomic %) in the metal phase and coating layer was measured. The Ti content, which is a secondary element, was determined by ICP emission spectroscopy of a solution of the composite material dissolved in dilute nitric acid. The Ti content is the ratio of the number of Ti atoms to the total number of Cu, Ag, and Ti atoms in the solution.

[0093] (Relative density of composite material) The relative density (%) of the composite material was determined by the method described in the "Relative Density of Composite Materials" section above. First, the mass of the composite material of each sample was measured, and the volume of the composite material of each sample was determined by Archimedes' method. The actual density of the composite material of each sample was determined by dividing the measured mass by the volume. Next, the theoretical density of the composite material of each sample was determined, and the relative density of the composite material was obtained by dividing the actual density of Composite Material 1 by the theoretical density of Composite Material 1. The theoretical density of the composite material was determined by following steps 1 to 5 shown in the "Relative Density of Composite Materials" section.

[0094] [Table 1]

[0095] As shown in Table 1, the Ag content in the composite material is 0.25 atomic % or more and 10.0 atomic % or less, and the Ti content is 1.5 atomic % or more and 14.0 atomic % or less. belowThe composite materials of Samples No. 1 to No. 19, which had an Ag content of 0.5 atomic % or more and 4.5 atomic % or less and a Ti content of 2.5 atomic % or more and 10.0 atomic % or less, had a thermal conductivity of 660 W / m K or more and had good heat resistance.

[0096] The composite materials with Ag contents exceeding 10.0 atomic % in samples No. 20, 21, and 28 had low heat resistance. This is presumably because the Ag content in the metal phase was too high, and part of the metal phase melted during heat treatment at 800°C.

[0097] In samples No. 22 and No. 23, in which the Ti content in the composite material was less than 1.5 atomic percent, the molten metal did not sufficiently infiltrate the diamond particles, and no composite material was formed. On the other hand, in sample No. 21, although the Ti content was low, the Ag content was high, and so the molten metal infiltrated the diamond particles. This indicates that the presence of Ag in the molten metal plays a major role in improving the wettability between the diamond particles and the molten metal.

[0098] In sample No. 24, the diamond particles were sufficiently infiltrated with the molten metal even though the Ag content was less than 0.25 atomic %. This is presumably because the Ti content in sample No. 24 was relatively high, forming a thick coating layer on the surface of the diamond particles. Although the thick coating layer improves the wettability of the diamond particles with the molten metal, it reduces the thermal conductivity of the composite material. In fact, the thermal conductivity of sample No. 24 was about 400 W / m K.

[0099] The thermal conductivity of the composite materials of samples No. 25 to No. 27, in which the Ti content in the composite material was over 14.0 atomic %, was about 400 W / m K. A high Ti content means that the coating layer was thick. Therefore, it is presumed that the thermal conductivity of the composite materials of samples No. 25 to No. 27 was reduced by the presence of a thick coating layer.

[0100] In addition, samples No. 5 to 7, 17 in Table 1 and sample No. . From the comparison results of 1–4, 8–16, 18, and 19, it was found that the mixed powder of fine and coarse diamond powder increased the particle content in the composite material.

[0101] <Test Example 2> In Test Example 2, composite materials of Samples No. 30 to 39 were prepared by changing the first and second elements, and the thermal conductivity and heat resistance of each sample were examined. The measurement items and measurement methods of Test Example 2 were the same as those of Test Example 1. Sample No. . The measurement results of 30 to 39 are shown in Table 2.

[0102] The first element in Test Example 2 was either Ag, Mg, Al, Sn, Zn, or Mn. The second element was either Ti, Zr, Cr, Si, Ta, or Nb. In Table 2, the first element is represented as "α" and the second element is represented as "β".

[0103] [Table 2]

[0104] As shown in Table 2, the composite materials of samples No. 30 to No. 39 had excellent thermal conductivity and heat resistance. From these results, it was revealed that Mg, Al, Sn, Zn, and Mn effectively function as the first element in place of Ag. It was also revealed that Zr, Cr, Si, Ta, and Nb effectively function as the second element in place of Ti. [Explanation of symbols]

[0105] 1 composite material, 2 metal phase, 3 particles, 31 fine particles, 32 coarse particles, 4 coating layer, 5 heat dissipation member, 6 base material, 7 copper layer.

Claims

1. A metallic phase; a plurality of particles dispersed in the metal phase; Each of the plurality of particles is a composite material having a coating layer covering a surface of the each particle, the plurality of particles are diamond; The components other than carbon are: A first element is 0.25 atomic % or more and 10.0 atomic % or less, The second element is contained in an amount of 1.5 atomic % or more and 14.0 atomic % or less, The balance is copper and unavoidable impurities. the coating layer is a carbide of the second element, the first element is a metal element having a surface tension lower than that of copper; the second element is at least one selected from the group consisting of silicon, titanium, chromium, zirconium, niobium, and tantalum; The plurality of particles includes a plurality of fine particles and a plurality of coarse particles, Each of the plurality of fine particles has a particle size of less than 30 μm; Each of the plurality of coarse particles has a particle size of 30 μm or more; A volume ratio of the plurality of fine particles to the total volume of the plurality of particles is 20 volume % or more and 50 volume % or less. Composite material.

2. A metallic phase; a plurality of particles dispersed in the metal phase; Each of the plurality of particles is a composite material having a coating layer covering a surface of the each particle, the plurality of particles are diamond; The components other than carbon are: A first element is 0.25 atomic % or more and 10.0 atomic % or less, The second element is 1.5 atomic % or more and 14.0 atomic % or less, Contains a third element in an amount of more than 0 atomic % and not more than 2.0 atomic %; The balance is copper and unavoidable impurities. the coating layer is a carbide of the second element, the first element is a metal element having a surface tension lower than that of copper; the second element is at least one selected from the group consisting of silicon, titanium, chromium, zirconium, niobium, and tantalum; the third element is at least one selected from the group consisting of sulfur, phosphorus, nickel, cobalt, and iron; The plurality of particles includes a plurality of fine particles and a plurality of coarse particles, Each of the plurality of fine particles has a particle size of less than 30 μm; Each of the plurality of coarse particles has a particle size of 30 μm or more; A volume ratio of the plurality of fine particles to the total volume of the plurality of particles is 20 volume % or more and 50 volume % or less. Composite material.

3. 3. The composite material according to claim 1, wherein the first element is at least one selected from the group consisting of silver, magnesium, aluminum, tin, zinc, and manganese.

4. The composite material of claim 3 , wherein the first element is silver.

5. The composite material according to any one of claims 1 to 4, wherein the second element is titanium.

6. The composite material according to claim 1 , wherein the content of the plurality of particles is 40% by volume or more and 85% by volume or less.

7. A substrate made of the composite material according to any one of claims 1 to 6; A copper layer covering at least a portion of the surface of the substrate. Heat dissipation material.

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