Diamond aluminum nitride composite material, preparation method and heat dissipation substrate

Abstract

The invention discloses a diamond aluminum nitride composite material, a preparation method and a heat dissipation substrate, and belongs to the technical field of electronic devices. And 94-99 wt% of the main material and the balance of the additive are subjected to ball milling and mixing to obtain a mixture, and the mixture is sintered to prepare the diamond aluminum nitride composite material. Wherein 94-99 wt% of the main material comprises 20-70 wt% of titanium-coated diamond particles and 24-79 wt% of aluminum nitride powder, the additive comprises 1-6 wt% of a sintering aid, and the diamond aluminum nitride composite material with high heat conductivity and breakdown voltage resistance can be prepared. According to the method, the heat conductivity and breakdown voltage resistance of the composite material can be guaranteed, meanwhile, the process is simple and rapid, industrial production of the diamond aluminum nitride composite material can be improved, and the production cost is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of electronic devices, and in particular to a diamond aluminum nitride composite material, a preparation method and a heat dissipation substrate. Background Art

[0002] In modern power electronics applications, power devices are developing towards higher power and smaller size. As power density increases, the requirements for heat dissipation performance and breakdown voltage resistance of heat dissipation substrates are becoming increasingly stringent. Therefore, it is necessary to provide a packaging material that combines high thermal conductivity with high breakdown voltage resistance. Summary of the Invention

[0003] The present application provides a diamond aluminum nitride composite material, a preparation method and a heat dissipation substrate. The diamond aluminum nitride composite material has high thermal conductivity and breakdown voltage resistance, and can improve the heat dissipation efficiency and safety and stability of electronic devices.

[0004] This application is implemented as follows: In a first aspect, examples of the present application provide a diamond-aluminum nitride composite material comprising, by weight percentage, 94-99% of a main material and the remainder of an additive. The 94-99% main material comprises 20-70% by weight of titanium-coated diamond and 24-79% by weight of aluminum nitride. The additive comprises 1-6% by weight of a sintering aid.

[0005] In the above-mentioned diamond-aluminum nitride composite material, diamond has a high thermal conductivity and a low expansion coefficient, aluminum nitride has a high thermal conductivity and excellent electrical insulation, and aluminum nitride can cooperate well with the thermal expansion of diamond, so that the diamond-aluminum nitride composite material has high thermal conductivity and breakdown voltage resistance on the basis of good structural stability.

[0006] The use of titanium-coated diamond and aluminum nitride for compounding can achieve a close bond between diamond and aluminum nitride, which not only reduces the interfacial thermal resistance between the two to better exert the intrinsic thermal conductivity of diamond and aluminum nitride, but also reduces the probability of easy debonding of the diamond aluminum nitride composite material to form air gaps or microcracks that trigger partial discharge, and can reduce interfacial heat accumulation, thereby enabling the diamond aluminum nitride composite material to have higher thermal conductivity and breakdown voltage. When the diamond aluminum nitride composite material of the present application is made into a heat dissipation substrate, it can effectively reduce the operating temperature of electronic devices, increase the number of cycles, and extend the service life.

[0007] In combination with the first aspect, in an optional embodiment of the present application, the sintering aid includes at least one of Y2O3, CaO, Li2O, YF3, MgO, CaF2, CaC2, Sm2O3, Li2CO3, Dy2O3, B2O3 or CeO.

[0008] Optionally, the sintering aid includes at least one oxide and at least one fluoride, and the mass ratio of the oxide to the fluoride is (1-5): (1-5).

[0009] Optionally, the density of the diamond aluminum nitride composite material is not less than 95%.

[0010] Optionally, the density of the diamond aluminum nitride composite material is not less than 99%.

[0011] In the above-mentioned implementation process, the diamond aluminum nitride composite material provided by the embodiment of the present application has a density of not less than 95% or even 99%, and there are fewer pores inside the diamond aluminum nitride composite material. When dissipating heat from electronic devices, heat can be more efficiently transferred from the aluminum nitride and diamond inside the diamond aluminum nitride composite material to the outside world for heat dissipation (the thermal conductivity of aluminum nitride and diamond is higher than the thermal conductivity of air in the pores), and in an electrical environment, electrons are not easy to escape from the air in the pores inside the diamond aluminum nitride composite material and break through the diamond aluminum nitride composite material, thereby improving the thermal conductivity and breakdown voltage resistance of the diamond aluminum nitride composite material.

[0012] Furthermore, the addition of oxides (such as Y2O3 / CaO / MgO / CeO) ​​to the sintering agent can react on the AlN surface to form a low-melting-point liquid phase, promoting densification. For example, Al2O3 can react on the AlN surface to form a low-melting-point liquid phase, the Y-Al-O phase. The addition of fluorides (such as CaF2 / YF3) to the sintering agent can reduce liquid phase viscosity, accelerate grain boundary diffusion, and inhibit the formation of oxygen impurities (forming volatile Al-OF compounds). A mass ratio of oxides to fluorides of (1-5):(1-5) can improve the thermal conductivity of the composite material.

[0013] In combination with the first aspect, in an optional embodiment of the present application, in the diamond aluminum nitride composite material, the average grain size of the aluminum nitride is 10-30 μm.

[0014] Optionally, the main material includes 30-60% wt titanium-coated diamond and 24-69% wt aluminum nitride.

[0015] Optionally, the average particle size of the titanium-coated diamond is 150-400 μm.

[0016] Optionally, the average particle size of the titanium-coated diamond is 80-320 μm.

[0017] Optionally, the titanium-coated diamond is titanium-plated diamond, and the thickness of the titanium coating is 200-400 nm.

[0018] Optionally, the thermal conductivity of the diamond aluminum nitride composite material is not less than 150 W / m·K, and the breakdown voltage is not less than 3 KV.

[0019] Optionally, the thermal conductivity of the diamond aluminum nitride composite material is not less than 350 W / m·K, and the breakdown voltage is not less than 13 KV.

[0020] Optionally, the thermal conductivity of the diamond aluminum nitride composite material is 350-460 W / m·K.

[0021] In the aforementioned implementation, the diamond-aluminum-nitride composite material prepared according to the method provided in the embodiments of this application has suitable particle sizes for the titanium-coated diamond and aluminum nitride, which can alleviate arc concentration while ensuring thermal conductivity and improve the breakdown threshold. This results in the diamond-aluminum-nitride composite material provided in the embodiments of this application having a thermal conductivity of no less than 350 W / m·K and a breakdown voltage of no less than 13 kV. When applied to heat-dissipating substrates, it can effectively reduce the operating temperature of electronic devices, increase cycle life, and extend service life.

[0022] In a second aspect, an example of the present application provides a method for preparing a diamond aluminum nitride composite material, comprising: S1. Ball milling 94-99 wt% of a main material and the remainder of an additive to obtain a mixture, based on weight percentage. The 94-99 wt% main material includes 20-70 wt% titanium-coated diamond particles and 24-79 wt% aluminum nitride powder. The additive includes 1-6 wt% sintering aid.

[0023] S2. Sintering the mixture to obtain a diamond aluminum nitride composite material.

[0024] In the above implementation process, titanium-coated diamond particles, aluminum nitride powder and sintering aids in an appropriate mass ratio are ball-milled and mixed and then sintered to obtain a diamond aluminum nitride composite material with higher density, smaller aluminum nitride grain size and low degree of diamond graphitization, so that the diamond aluminum nitride composite material has higher thermal conductivity and breakdown voltage resistance.

[0025] By combining titanium-coated diamond of suitable quality with aluminum nitride, on the one hand, during the sintering process, part of the titanium metal in the titanium layer can achieve a close bond with the diamond particles by generating titanium carbide on the diamond surface. On the other hand, another part of the titanium metal in the titanium layer has good physical and chemical compatibility with the aluminum nitride, and the titanium layer has good adhesion to the aluminum nitride, and the titanium layer can be tightly bonded to the aluminum nitride, thereby achieving a close bond between the diamond and the aluminum nitride. Using the titanium layer to tightly bond the aluminum nitride and the diamond can, on the one hand, reduce the interfacial thermal resistance between the two, better utilize the intrinsic thermal conductivity of the diamond and aluminum nitride, and thus improve the overall thermal conductivity of the diamond-aluminum nitride composite material. On the other hand, the close bonding between diamond and aluminum nitride can improve the density of the composite material, reduce internal porosity, and reduce the voltage breakdown weak parts inside the composite material; and, due to the high interface bonding strength and low interface thermal resistance, in the process of resisting voltage breakdown, the diamond aluminum nitride composite material is not easy to debond to form air gaps or microcracks to cause local discharge, and the interface heat accumulation is less, which can increase the voltage breakdown threshold and alleviate voltage breakdown, thereby further improving the breakdown voltage of the diamond aluminum nitride composite material. If the mass of titanium-coated diamond is too much and the mass of aluminum nitride is too little, aluminum nitride cannot be effectively filled between the diamond particles. The density of the diamond aluminum nitride composite material obtained after sintering will be low, the breakdown voltage will be low, and the thermal conductivity and breakdown voltage will not be effectively improved. If the mass of titanium-coated diamond is too little and the mass of aluminum nitride is too much, the thermal conductivity will be poor, and the thermal conductivity and breakdown voltage will still not be effectively improved.

[0026] Adding an appropriate amount of sintering aid to the mixture and combining it with sintering technology can reduce the sintering temperature and improve the thermal conductivity and breakdown voltage of the composite material. If the content of the sintering aid is too much, it will introduce too many voltage breakdown weak points and heat transfer resistance areas into the diamond aluminum nitride composite material, which will affect the thermal conductivity and breakdown voltage of the diamond aluminum nitride composite material. If the amount of sintering aid added is too little, the sintering temperature cannot be effectively reduced, which will affect the density of the diamond aluminum nitride composite material. If the sintering temperature is too high, it will not only lead to an increase in the degree of diamond graphitization, affecting the thermal conductivity of the composite material; it will also cause the grain size of aluminum nitride to be too large, and local arc concentration will easily cause local discharge, which will reduce the breakdown voltage.

[0027] The preparation method has simple process and high repetition rate, which is conducive to the industrial production of diamond aluminum nitride composite materials.

[0028] In conjunction with the second aspect, in an optional embodiment of the present application, the sintering method includes: vacuum hot pressing the mixed material and then cooling and reducing the pressure, wherein the sintering temperature is 1200-1400°C, the sintering pressure is 30-80 MPa, and the sintering time is 10-50 minutes.

[0029] In this implementation process, adding an appropriate amount of sintering aid to the mixture and combining it with vacuum hot pressing technology can further reduce the sintering temperature and improve the thermal conductivity and breakdown voltage of the composite material. In addition, vacuum hot pressing sintering at a sintering temperature of 1200-1400°C and a sintering pressure of 30-80 MPa for 10-50 minutes can promote plastic flow and densification of the particles, achieving a relative density of >95%, ensuring sufficient liquid phase sintering and aluminum nitride grain growth.

[0030] In conjunction with the second aspect, in an optional embodiment of the present application, the average particle size of the titanium-coated diamond is 150-400 μm, and / or the average particle size of the aluminum nitride powder is 1.5-4 μm.

[0031] Optionally, the average particle size of the titanium-coated diamond is 80-320 μm.

[0032] Optionally, the titanium-coated diamond is titanium-plated diamond, and the thickness of the titanium coating is 200-400 nm.

[0033] Optionally, the main material includes 30-60% wt of titanium-coated diamond particles and 34-69% wt of aluminum nitride powder.

[0034] In the above implementation process, the titanium-coated diamond and aluminum nitride have suitable particle sizes, which can reduce thermal resistance while increasing breakdown voltage, so that the diamond aluminum nitride composite material can have both high thermal conductivity and breakdown voltage resistance.

[0035] In combination with the second aspect, in an optional embodiment of the present application, the sintering aid includes at least one of Y2O3, CaO, Li2O, YF3, MgO, CaF2, CaC2, Sm2O3, Li2CO3, Dy2O3, B2O3 or CeO.

[0036] Optionally, the sintering aid includes at least one oxide and at least one fluoride, and the mass ratio of the oxide to the fluoride is (1-5): (1-5).

[0037] Optionally, the sintering aids are Y2O3, MgO and CaF2.

[0038] Optionally, the sintering aids are Y2O3 and CaF2.

[0039] Optionally, the sintering aids are CeO and CaF2.

[0040] Optionally, the sintering aids are CeO, MgO and CaF2.

[0041] In the above implementation process, an appropriate mass ratio of oxide and fluoride sintering aids is added. The combination of these two sintering aids can reduce the sintering temperature of the diamond aluminum nitride composite during sintering, improve the density of the diamond aluminum nitride composite, inhibit the growth of aluminum nitride grains, and reduce the probability of diamond graphitization during sintering, thereby improving the thermal conductivity and breakdown voltage of the diamond aluminum nitride composite. Furthermore, the addition of oxides (such as Y2O3 / CaO / MgO / CeO) ​​to the sintering agent can react on the AlN surface to form a low-melting liquid phase, promoting densification. For example, Al2O3 can react on the AlN surface to form a low-melting liquid phase, the Y-Al-O phase. The addition of fluorides (such as CaF2 / YF3) to the sintering agent can reduce the liquid phase viscosity, accelerate grain boundary diffusion, and inhibit the formation of oxygen impurities (forming volatile Al-OF compounds). A mass ratio of oxides to fluorides of (1-5): (1-5) can improve the thermal conductivity of the composite.

[0042] In combination with the second aspect, in an optional embodiment of the present application, during hot pressing sintering, the heating rate is 30~60℃ / min.

[0043] Optionally, the sintering temperature is 1200-1300°C.

[0044] In the above implementation process, heating to the sintering temperature at a relatively fast rate of 30-60°C / min can reduce the time the titanium-coated diamond is exposed to high temperatures, reducing the impact of the sintering process on the thermal conductivity of the titanium-coated diamond, resulting in a diamond-aluminum nitride composite material with higher thermal conductivity. Lowering the sintering temperature to 1200-1300°C can further improve the thermal conductivity and breakdown voltage of the resulting diamond-aluminum nitride composite material.

[0045] In conjunction with the second aspect, in an optional embodiment of the present application, the method of cooling and lowering the pressure includes step-by-step cooling and lowering the pressure: The first stage of cooling and pressure reduction involves lowering the temperature from 1200-1400°C to 800-1000°C and the pressure from 30-80 MPa to 30-60 MPa, followed by holding at this temperature and pressure for 10-20 minutes. The second stage of cooling and pressure reduction involves lowering the temperature from 800-1000°C to 400-700°C and the pressure from 30-60 MPa to 10-20 MPa, followed by holding at this temperature and pressure for 10-20 minutes. The third stage of cooling and pressure reduction involves cooling the furnace to room temperature and then releasing the pressure to atmospheric pressure.

[0046] In the above implementation process, after sintering is completed, a step-by-step cooling and pressure reduction method is adopted. The first stage of cooling and pressure reduction can slowly release thermal stress and avoid interface microcracks; the second stage of cooling and pressure reduction can further stabilize the grain boundary phase; the third stage of cooling and pressure reduction can eventually eliminate residual stress, making the bond between titanium-coated diamond and silicon nitride stronger, thereby enabling the obtained diamond aluminum nitride composite material to have higher thermal conductivity and breakdown voltage resistance.

[0047] In a third aspect, an embodiment of the present application provides a heat dissipation substrate, comprising the diamond aluminum nitride composite material provided in the embodiment of the first aspect of the present application.

[0048] In the above implementation process, the diamond aluminum nitride composite material provided in the first aspect is used to prepare a heat dissipation substrate. Since the diamond aluminum nitride composite material has a high thermal conductivity and a high breakdown voltage, when the heat dissipation substrate is used to dissipate heat from electronic devices, it can effectively reduce the operating temperature of the electronic devices, increase the number of cycles, and extend the service life. It can be suitable for the heat dissipation and insulation safety requirements of higher power electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art.

[0050] Figure 1 A flow chart of the preparation process of the diamond aluminum nitride composite material provided in the embodiments of the present application; Figure 2 This is a low-magnification SEM image of the diamond aluminum nitride composite material provided in Example 1 of the present application; Figure 3 This is a high-magnification SEM image of the diamond aluminum nitride composite material provided in Example 1 of the present application. DETAILED DESCRIPTION

[0051] The embodiments of the present application will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0052] Currently, electronic devices are developing towards higher power and smaller sizes. The higher the power, the greater the heat generated by the electronic device, necessitating a heat dissipation substrate that can more efficiently transfer heat away from the electronic device. Typically, to improve heat dissipation efficiency, the size of the heat dissipation substrate is increased. However, increasing the size of the heat dissipation substrate does not meet the demands of miniaturization of power devices. Therefore, a material with higher thermal conductivity is needed to fabricate the heat dissipation substrate.

[0053] Diamond, as a naturally occurring superhard material, has a high thermal conductivity of 2200W / m·K. If diamond is used to prepare a heat dissipation substrate, it is expected to significantly improve the heat dissipation of the heat dissipation substrate. Due to the high cost of natural diamonds, researchers have begun to explore the combination of diamond and other high thermal conductivity materials. For example, the thermal conductivity of diamond-copper composite materials has exceeded 900W / m·K, and the thermal conductivity of diamond-silicon carbide composite materials can reach more than 800W / m·K. However, the current breakdown voltage of diamond composite materials is low, and they cannot be used in electronic devices that require a high breakdown voltage for heat dissipation substrates, such as IGBTs.

[0054] Therefore, it is necessary to provide a diamond composite material with higher thermal conductivity and breakdown voltage.

[0055] The inventors believe that by compounding diamond with other insulating and highly thermally conductive materials, it is possible to obtain a diamond composite material that has both high thermal conductivity and high breakdown voltage.

[0056] The inventors discovered that among existing insulating materials, aluminum nitride ceramics have high thermal conductivity (theoretical value reaches 320W / m·K) and excellent electrical insulation properties, and have good thermal expansion matching with diamond, making them an ideal choice for preparing diamond composite materials with high thermal conductivity and breakdown voltage resistance.

[0057] The inventors tried to mix aluminum nitride powder and diamond particles and then perform conventional sintering to prepare a diamond aluminum nitride composite material, but the thermal conductivity and breakdown voltage of the composite material were low. The inventors analyzed the reasons and found that the temperature of conventional pressureless vacuum sintering was high, which would cause some diamonds to undergo graphitization reaction, which would reduce the thermal conductivity of the diamond composite material. In addition, the density of the diamond composite material obtained by conventional pressureless sintering is poor, and there are many pores inside the composite material, which will become a weak area for voltage breakdown and a heat transfer barrier area, thereby affecting the thermal conductivity and breakdown voltage of the composite material. In addition, the interface bonding between diamond and aluminum nitride is poor, the interface thermal resistance is high, and the voltage breakdown stability is poor, which will also reduce the thermal conductivity and breakdown voltage of the composite material.

[0058] Therefore, in order to improve the above-mentioned problem of poor interfacial bonding, the inventors attempted to use an in-situ reaction deposition method to coat the surface of diamond particles with an aluminum nitride layer. The diamond particles coated with the aluminum nitride layer were then mixed with aluminum nitride particles, laser melted, and sintered. The aluminum nitride coating grown in situ on the surface of the diamond particles came into contact with the aluminum nitride particles, achieving a tight bond between the aluminum nitride particles and the diamond particles. However, the above-mentioned preparation process is relatively complex. The diamond particles need to undergo complex surface treatment before in-situ reaction deposition. The deposition process parameters are relatively complex to control. In addition, the diamond particles need to be frequently heated and cooled, which affects the structural stability and thermal conductivity of the diamond particles. The process repeatability is poor, which is not conducive to industrial production.

[0059] Based on this, an embodiment of the present application provides a method for preparing a diamond aluminum nitride composite material, so as to prepare a diamond aluminum nitride composite material with both high thermal conductivity and high breakdown voltage through an efficient and simple process.

[0060] See also Figure 1 The method for preparing the diamond aluminum nitride composite material provided in the embodiment of the present application comprises: S1. Ball milling 94-99 wt% of a main material and the remainder of an additive to obtain a mixture, based on weight percentage. The 94-99 wt% main material includes 20-70 wt% titanium-coated diamond particles and 24-79 wt% aluminum nitride powder. The additive includes 1-6 wt% sintering aid.

[0061] S2. Sintering the mixture to obtain a diamond aluminum nitride composite material.

[0062] Titanium-coated diamond is used in combination with aluminum nitride. On the one hand, part of the metallic titanium in the titanium layer can generate titanium carbide on the diamond surface during the sintering process, thereby achieving a close bond between the titanium layer and the diamond. On the other hand, titanium and aluminum nitride have good physical and chemical matching, and the titanium layer has good adhesion to aluminum nitride. The titanium layer can be tightly bonded with aluminum nitride, thereby achieving a close bond between diamond and aluminum nitride, thereby reducing the interfacial contact thermal resistance between the two, better exerting the intrinsic thermal conductivity of diamond and aluminum nitride, reducing the voltage breakdown threshold, and thus improving the overall thermal conductivity and breakdown voltage resistance of the diamond aluminum nitride composite material. Compared to the in-situ growth of aluminum nitride coating on the surface of diamond particles, the aluminum nitride coating and the diamond surface are always physically bonded, and the chemical bond between the titanium layer and the diamond particles will be stronger, which is also more conducive to reducing interfacial thermal resistance and improving breakdown voltage resistance.

[0063] In the embodiments of this application, titanium-coated diamond refers to diamond particles coated with a titanium layer. The titanium layer can fully or partially coat the diamond particles, and this application does not impose any restrictions. It is understood that in the diamond-aluminum nitride composite material obtained after sintering, the titanium layer contains at least a portion of titanium carbide.

[0064] In some embodiments, the titanium layer fully covers the diamond, which can further improve the bonding strength between the diamond and the aluminum nitride.

[0065] Furthermore, the present application does not limit how the titanium layer is coated on the surface of the diamond particles. In some embodiments, the titanium layer can be plated on the surface of the diamond particles. For example, the purchased diamond particles are subjected to acid and alkali treatment to remove substances such as paraffin on the surface of the diamond particles and improve the purity of the surface of the diamond particles. Then, metallic titanium is plated by evaporation, and after cooling, it is washed 3-5 times in distilled water. Alternatively, in some embodiments, the titanium layer can be formed by ball-milling the diamond particles and titanium powder and then sintering them. That is, titanium-coated diamond includes titanium-plated diamond and titanium-coated diamond.

[0066] Furthermore, the present application does not limit the particle size of the titanium-coated diamond particles. In some embodiments, the average particle size of the titanium-coated diamond particles can be 150-400 μm. Titanium-coated diamond particles of appropriate particle size can improve the thermal conductivity and breakdown voltage of the composite material.

[0067] As an example, the average particle size of the titanium-coated diamond may be in the range of one or any two of 150 μm, 200 μm, 250 μm, 300 μm, 350 μm or 400 μm.

[0068] Furthermore, in some embodiments, the average particle size of the titanium-coated diamond may be 80-320 μm.

[0069] Furthermore, this application does not limit the thickness of the titanium layer on the titanium-coated diamond. In some embodiments, the thickness of the titanium layer can be 200-400 nm. A titanium layer of suitable thickness can enhance the bonding strength between the diamond and aluminum nitride, further improving the thermal conductivity and breakdown voltage of the diamond-aluminum nitride composite material.

[0070] As an example, the thickness of the titanium layer may be one of 200 nm, 250 nm, 300 nm, 350 nm, or 400 nm, or a range between any two thereof.

[0071] By combining titanium-coated diamond and aluminum nitride in an appropriate mass ratio, the problems of weak bonding of the composite material due to excessive diamond and poor thermal conductivity caused by excessive aluminum nitride particles can be avoided, and both high thermal conductivity and high breakdown voltage can be achieved.

[0072] This application does not limit the specific mass content range of titanium-coated diamond in the main material. Those skilled in the art can make an appropriate selection within the range of 20% to 70% by weight. As an example, the diamond aluminum nitride composite material can contain one of 20% by weight, 25% by weight, 30% by weight, 35% by weight, 40% by weight, 45% by weight, 50% by weight, 55% by weight, 60% by weight, 65% by weight, or 70% by weight, or any two thereof.

[0073] As an example, the main material includes 20%wt titanium-coated diamond particles and 74%wt aluminum nitride powder; as an example, the main material includes 20%wt titanium-coated diamond particles and 79%wt aluminum nitride powder; as an example, the main material includes 70%wt titanium-coated diamond particles and 29%wt aluminum nitride powder; as an example, the main material includes 70%wt titanium-coated diamond particles and 24%wt aluminum nitride powder.

[0074] Furthermore, the main material includes 30-60%wt titanium-coated diamond particles and 34-69%wt aluminum nitride powder.

[0075] Furthermore, in some embodiments, during sintering, the particle size of the aluminum nitride powder raw material can be 1.5-4 μm. Sintering the aluminum nitride raw material powder of suitable particle size under the above sintering conditions can obtain a diamond aluminum nitride composite material with high density and suitable grain size.

[0076] As an example, the particle size of the aluminum nitride powder raw material may be in the range of one of 1.5 μm, 1.9 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, or 4 μm, or any two thereof.

[0077] Adding an appropriate weight percentage of sintering aid to the mixed powder can lower the sintering temperature. The lower sintering temperature reduces the impact of the sintering process on the thermal conductivity of the diamond. Furthermore, the low sintering temperature reduces the extent of grain growth in the aluminum nitride powder during sintering, resulting in aluminum nitride particles with an optimal grain size in the composite material. Aluminum nitride particles with an appropriate grain size can mitigate the likelihood of electric field concentration at grain boundaries, which can lead to distortion points caused by coarse grains and uneven microstructure. This can suppress local arc concentration, increase the breakdown voltage, and improve the composite material's breakdown voltage resistance. Furthermore, aluminum nitride particles with an appropriate grain size and an appropriate grain boundary area can avoid the increase in grain boundary thermal resistance caused by excessive grain boundaries, thereby reducing the composite material's internal resistance. Furthermore, excessive grain boundary thermal resistance can lead to heat accumulation at the grain boundaries, resulting in poor heat dissipation and reduced breakdown voltage of the solid material. Therefore, adding an appropriate weight percentage of sintering aid combined with vacuum hot pressing can reduce the sintering temperature and improve the thermal conductivity and breakdown voltage of the composite material.

[0078] If the amount of sintering aid added is too small and the sintering temperature is too high during sintering, some diamond will graphitize and the aluminum nitride grains will become coarse, which will in turn reduce the thermal conductivity and breakdown voltage of the composite material. If no sintering aid is added, the sintering temperature usually needs to be increased to 1800℃ or even above 2000℃ during atmospheric vacuum sintering, which will seriously reduce the thermal conductivity and breakdown voltage of the composite material.

[0079] Although adding sintering aids can help lower the sintering temperature, reduce the impact of the sintering process on the thermal conductivity of diamond, and reduce the grain size of aluminum nitride, adding too much sintering aid will introduce too many impurity elements into the composite material, which will become a weak point of voltage breakdown and a barrier to heat transfer, and will reduce the thermal conductivity and breakdown voltage of the composite material.

[0080] The present application does not limit the specific amount of the sintering aid, and relevant personnel can make appropriate selections within the above range. As an example, the weight content of the sintering aid can be one of 1%wt, 2%wt, 3%wt, 4%wt, 5%wt, or 6%wt, or a range between any two of them.

[0081] The present application does not limit the specific type of sintering aid. In some embodiments, the sintering aid includes at least one of Y2O3, CaO, Li2O, YF3, MgO, CaF2, CaC2, Sm2O3, Li2CO3, Dy2O3, B2O3 or CeO.

[0082] Further, in some embodiments, the sintering aid includes any two of Y2O3, CaO, Li2O, YF3, MgO, CaF2, CaC2, Sm2O3, Li2CO3, Dy2O3, B2O3 or CeO.

[0083] In some embodiments, the sintering aid comprises at least one oxide and at least one fluoride, with the mass ratio of the oxide to the fluoride being (1-5):(1-5). The combination of the two sintering aids can further reduce the sintering temperature and improve the thermal conductivity and breakdown voltage of the diamond aluminum nitride composite material. Excessive oxide sintering aid content, introducing excessive oxygen into the composite material system, can affect the thermal conductivity and breakdown voltage of the diamond aluminum nitride composite material.

[0084] As an example, the mass ratio of the oxide sintering aid to the fluoride sintering aid may be 1:1, 2:1, 3:1, 4:1, 5:1, 1:2, 1:3, 1:4 or 1:5, or a range between any two of them.

[0085] As an example, the sintering aid is YF3 and Y2O3 in a mass ratio of 1:1; as an example, the sintering aid is CeO and CaF2 in a mass ratio of 1:1; as an example, the sintering aid is Y2O3 and CaF2 in a mass ratio of 1:1. As an example, the sintering aid is CeO, MgO, and CaF2 in a mass ratio of 1:1:1.

[0086] It is understandable that, in addition to the sintering aid, the additives in step S1 inevitably contain some impurities or other auxiliary additives.

[0087] In step S1, the present application does not limit the specific ball milling method. In some embodiments, the grinding balls are aluminum nitride grinding balls, the ball milling ratio is 1:2, and the grinding balls have diameters of 8 cm, 5 cm, and 3 cm. The vacuum mixing is ball milled for 8-20 hours.

[0088] Furthermore, in step S2, the sintering method may be a vacuum hot pressing sintering method, which can further reduce the sintering temperature, reduce the aluminum nitride grain size, and improve the breakdown voltage of the diamond aluminum nitride composite material.

[0089] This application does not limit the specific sintering temperature, and relevant personnel can make appropriate selections within the above range. As an example, the sintering temperature can be one of 1200°C, 1250°C, 1300°C, 1350°C, or 1400°C, or a range between any two thereof, and the sintering time can be one of 10 minutes, 15 minutes, 20 minutes, 25 minutes, or 30 minutes, or a range between any two thereof.

[0090] As an example, the sintering temperature may be 1200-1300°C.

[0091] The present application does not limit the specific sintering pressure, and relevant personnel can make appropriate selections within the above range. As an example, the sintering pressure can be one of 30 MPa, 40 MPa, 50 MPa, 60 MPa, 70 MPa or 80 MPa, or a range between any two of them.

[0092] Furthermore, in some embodiments, during the process of heating to the sintering temperature, the temperature may be increased at a heating rate of 30-60°C / min. For example, the heating rate may be in the range of 30°C / min, 35°C / min, 40°C / min, 45°C / min, 50°C / min, 55°C / min, or 60°C / min, or any two thereof.

[0093] Furthermore, the temperature and pressure reduction method after sintering can be a step-by-step temperature and pressure reduction method: The first stage of cooling and pressure reduction is: reducing the temperature from 1200~1400℃ to 800~1000℃, reducing the pressure from 30~80MPa to 30~60MPa, and then keeping the temperature and pressure for 10~20min.

[0094] The second stage is cooling and pressure reduction: reduce the temperature from 800~1000℃ to 400~700℃, and the pressure from 30~60MPa to 10~20MPa, and then keep the temperature and pressure for 10~20min.

[0095] The third stage is cooling and pressure reduction: cooling to room temperature with the furnace, and then releasing the pressure to normal pressure.

[0096] As an example, during the first stage of cooling and pressure reduction, the temperature can be reduced to one of 800°C, 900°C or 1000°C or a range between any two of them, and the pressure can be reduced to one of 30 MPa, 40 MPa, 50 MPa or 60 MPa or a range between any two of them.

[0097] As an example, during the first stage of cooling and pressure reduction, the temperature can be reduced to one of 400°C, 500°C, 600°C or 700°C or a range between any two of them, and the pressure can be reduced to one of 10 MPa, 15 MPa or 20 MPa or a range between any two of them.

[0098] Furthermore, an embodiment of the present application provides a diamond-aluminum nitride composite material comprising, by weight percentage, 94-99% of a main material and the remainder being an additive. The 94-99% main material comprises 20-70% by weight of titanium-coated diamond and 24-79% by weight of aluminum nitride. The additive comprises 1-6% by weight of a sintering aid. Furthermore, the main material comprises 30-60% by weight of titanium-coated diamond and 24-69% by weight of aluminum nitride.

[0099] Furthermore, the density of the diamond aluminum nitride composite material provided in the embodiments of the present application is not less than 95%. Furthermore, the density of the diamond aluminum nitride composite material provided in the embodiments of the present application is not less than 99%. Furthermore, the density of the diamond aluminum nitride composite material provided in the embodiments of the present application is not less than 99.7%.

[0100] In some embodiments, the thermal conductivity of the diamond aluminum nitride composite material is not less than 150 W / m·K, and the breakdown voltage is not less than 3 KV. Furthermore, the thermal conductivity of the diamond aluminum nitride composite material provided in the embodiments of the present application is not less than 350 W / m·K, and the breakdown voltage is not less than 13 KV. Furthermore, the thermal conductivity of the diamond aluminum nitride composite material provided in the embodiments of the present application is 350-460 W / m·K.

[0101] Furthermore, in the diamond aluminum nitride composite material provided in the embodiment of the present application, the average grain size of the titanium-coated diamond is 150-400 μm, and the average grain size of the aluminum nitride is 10-30 μm.

[0102] Furthermore, the average grain size of the titanium-coated diamond is 80-320 μm.

[0103] Furthermore, an embodiment of the present application provides a heat dissipation substrate, comprising the diamond aluminum nitride composite material provided in an embodiment of the present application.

[0104] The diamond aluminum nitride composite material of the present application is further described in detail below with reference to the examples.

[0105] Example 1 Example 1 provides a diamond aluminum nitride composite material, the preparation method of which is as follows: Step 1. Raw material preparation: According to the weight percentage, 30wt% titanium-coated diamond particles, 66wt% silicon nitride powder, and 4wt% sintering aid powder are mixed by drum ball milling. Two diameters of silicon nitride balls are used as grinding media. The ball milling time is 10 hours to obtain a mixture. Among them, diamond raw material with an average particle size of 100μm is selected, and the diamond is subjected to titanium coating by metal vapor deposition. The titanium layer thickness is about 200nm to obtain titanium-coated diamond particles. The average particle size of aluminum nitride powder is 1.9μm. The sintering aid includes yttrium oxide, magnesium oxide, and calcium fluoride mixed in a mass ratio of 1:1:1.

[0106] Step 2: Mold filling: In a dry and dust-free environment, fill the mixture obtained in step 1 into a graphite mold. When filling in layers, place a 0.5mm graphite paper on the upper and lower sides of the mixed powder, and spray boron nitride to facilitate demolding.

[0107] Step 3, sintering: HPS hot pressing sintering process is used for sintering. The sintering parameters include: initial press preload of 10MPa, vacuum degree of 10 -3 Pa. Sintering was performed at 1200°C with a heating rate of 30°C / min and a pressure of 40 MPa. The temperature and pressure were maintained for 10 minutes. The temperature and pressure were then gradually decreased from 1200°C to 1000°C to 400°C, with a pressure of 40 MPa to 30 MPa to 15 MPa.

[0108] Step 4, post-processing: demoulding from the cold press, grinding with a diamond wheel lathe to remove the surface carbon paper, and then testing.

[0109] Example 2 Example 2 provides a diamond aluminum nitride composite material, which differs from Example 1 in that: In step 1, the raw materials include 40 wt% titanium-coated diamond particles, 55 wt% silicon nitride powder, and 5 wt% sintering aid powder. The average particle size of the diamond raw material is 150 μm. The sintering aid is yttrium oxide, magnesium oxide, and calcium fluoride mixed in a mass ratio of 1:2:3.

[0110] In step 3, the temperature was raised at a rate of 40°C / min, hot-pressed at 1300°C, and the pressure was controlled at 50 MPa for 20 minutes. The temperature and pressure were then gradually reduced from 1300°C to 1000°C to 700°C, and the pressure was 50 MPa to 30 MPa to 15 MPa.

[0111] Example 3 Example 3 provides a diamond aluminum nitride composite material, which differs from Example 1 in that: In step 1, the raw materials include 50 wt% titanium-coated diamond particles, 45 wt% silicon nitride powder, and 5 wt% sintering aid powder. The average particle size of the diamond raw material is 200 μm. The sintering aid includes yttrium oxide, magnesium oxide, and calcium fluoride mixed in a mass ratio of 2:2:3. The ball milling time is 14 hours.

[0112] In step 3, the temperature was raised at a rate of 50°C / min, hot-pressed at 1350°C, and the pressure was controlled at 70 MPa for 20 minutes. The temperature and pressure were then gradually reduced from 1350°C to 1100°C to 800°C, and the pressure was 70 MPa to 50 MPa to 15 MPa.

[0113] Example 4 Example 4 provides a diamond aluminum nitride composite material, which differs from Example 1 in that: In step 1, the raw materials include 60 wt% titanium-coated diamond particles, 34 wt% silicon nitride powder, and 6 wt% sintering aid powder. The diamond raw material particle size is 300 μm. The sintering aid is yttrium oxide, magnesium oxide, and calcium fluoride mixed in a mass ratio of 1:2:3. The ball milling time is 14 hours.

[0114] In step 3, the temperature was raised at a rate of 50°C / min, hot-pressed at 1400°C, and the pressure was controlled at 70 MPa for 20 minutes. The temperature and pressure were then gradually reduced from 1400°C to 1100°C to 800°C, and the pressure was 70 MPa to 50 MPa to 15 MPa.

[0115] Example 5 The difference between Example 5 and Example 1 is that: In step 1, the sintering aid includes yttrium oxide and calcium fluoride mixed in a mass ratio of 1:1.

[0116] Example 6 The difference between Example 6 and Example 1 is that: In step 1, the sintering aid includes yttrium oxide and calcium fluoride mixed in a mass ratio of 6:1.

[0117] Example 7 The difference between Example 7 and Example 1 is that: In step 3, the heating rate is 10°C / min.

[0118] Example 8 The difference between Example 8 and Example 1 is that: In step 8, the sintering temperature is 1450°C.

[0119] Comparative Example 1 Comparative Example 1 provides a diamond aluminum nitride composite material, which differs from Example 1 in that: In step 1, the raw materials include 80 wt% of titanium-coated diamond particles, 13 wt% of silicon nitride powder, and 7 wt% of sintering aid powder.

[0120] In step 3, the sintering method is atmospheric pressure vacuum sintering, and the sintering temperature is 1800°C.

[0121] Some process parameters of the embodiments and comparative examples are shown in Table 1.

[0122] Table 1

[0123] Test example: (1) Room temperature thermal conductivity: The room temperature thermal conductivity of the diamond aluminum nitride composite materials provided in the examples and comparative examples was tested. The test method was based on the international standard GB / T 39862-2021.

[0124] (2) Breakdown voltage test: refer to GB / T 1408.1 standard.

[0125] (3) Density test: refer to GB / T 3810.3-2016 standard.

[0126] (4) Morphology analysis: The micromorphology of the diamond aluminum nitride composite material provided in Example 1 was analyzed. The SEM images at different magnifications are shown in Figure 2 and Figure 3 .

[0127] See Table 2 for test results.

[0128] Table 2

[0129] Result analysis: from Figure 2 and Figure 3It can be seen that the black titanium-coated diamond particles are surrounded by dense aluminum nitride grains of uniform and small size. The number of pores inside the diamond aluminum nitride composite material is relatively low.

[0130] As can be seen from Table 2, the diamond aluminum nitride composite material obtained by the preparation method provided in Examples 1 to 8 of the present application has a high thermal conductivity and breakdown voltage. Compared with Examples 1, 5 and 6, it can be seen that when the same mass content of sintering aids is added, Example 5 uses Y2O3 and CaF2 with a mass ratio of 1:1 as sintering aids. Compared with Examples 1 and 6, the thermal conductivity and breakdown voltage of the composite material obtained are better. Comparing Example 1 and Example 7, it can be seen that under the same raw material composition and sintering temperature, Example 1 adopts a faster heating rate of 30°C / min, which can further improve the thermal conductivity of the diamond aluminum nitride composite material. Comparing Example 1 and Comparative Example 1, it can be seen that the amount of sintering aid added in Comparative Example 1 is too much, the content of titanium-coated diamond is too much, and the aluminum nitride content is too low, and sintering molding cannot be achieved.

[0131] It is illustrated that the preparation method provided in the embodiments of the present application can efficiently and conveniently prepare a diamond aluminum nitride composite material with high thermal conductivity and breakdown voltage resistance.

[0132] The foregoing description is merely a preferred embodiment of the present application and is not intended to limit the present application. Persons skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A diamond aluminum nitride composite material, characterized in that: According to weight percentage, it includes 94-99wt% main material and the balance additives; the 94-99wt% main material includes 20-70wt% titanium-coated diamond and 24-79wt% aluminum nitride; the additives include 1-6wt% sintering aids.

2. The diamond aluminum nitride composite material according to claim 1, characterized in that The sintering aid includes at least one of Y2O3, CaO, Li2O, YF3, MgO, CaF2, CaC2, Sm2O3, Li2CO3, Dy2O3, B2O3 or CeO; Optionally, the sintering aid comprises at least one oxide and at least one fluoride, and the mass ratio of the oxide to the fluoride is (1-5): (1-5); Optionally, the density of the diamond aluminum nitride composite material is not less than 95%; Optionally, the density of the diamond aluminum nitride composite material is not less than 99%.

3. The diamond aluminum nitride composite material according to claim 1 or 2, characterized in that: In the diamond aluminum nitride composite material, the average grain size of the aluminum nitride is 10-15 μm; Optionally, the main material comprises 30-60%wt titanium-coated diamond and 24-69%wt aluminum nitride; Optionally, the average particle size of the titanium-coated diamond is 150-400 μm; Optionally, the average particle size of the titanium-coated diamond is 80-320 μm; Optionally, the titanium-coated diamond is titanium-plated diamond, and the thickness of the titanium coating is 200-400 nm; Optionally, the thermal conductivity of the diamond aluminum nitride composite material is not less than 150W / m·K, and the breakdown voltage is not less than 3KV; Optionally, the thermal conductivity of the diamond aluminum nitride composite material is not less than 350W / m·K, and the breakdown voltage is not less than 13KV; Optionally, the thermal conductivity of the diamond aluminum nitride composite material is 350-460 W / m·K.

4. A method for preparing a diamond aluminum nitride composite material, characterized in that: include: S1. According to weight percentage, 94-99 wt% of the main material and the balance of additives are ball-milled to obtain a mixture; the 94-99 wt% main material comprises 20-70 wt% titanium-coated diamond particles and 24-79 wt% aluminum nitride powder; the additives comprise 1-6 wt% sintering aid; S2. Sintering the mixture to obtain the diamond aluminum nitride composite material.

5. The preparation method according to claim 4, characterized in that The sintering method comprises: performing vacuum hot pressing sintering on the mixed material, and then cooling and reducing the pressure; wherein the sintering temperature is 1200-1400° C., the sintering pressure is 30-80 MPa, and the sintering time is 10-50 minutes.

6. The preparation method according to claim 4, characterized in that The average particle size of the titanium-coated diamond is 150-400 μm; and / or the average particle size of the aluminum nitride powder is 1.5-4 μm; Optionally, the average particle size of the titanium-coated diamond is 80-320 μm; Optionally, the titanium-coated diamond is titanium-plated diamond, and the thickness of the titanium coating is 200-400 nm; Optionally, the main material includes 30-60% wt of the titanium-coated diamond particles and 34-69% wt of the aluminum nitride powder.

7. The preparation method according to any one of claims 4 to 6, characterized in that The sintering aid includes at least one of Y2O3, CaO, Li2O, YF3, MgO, CaF2, CaC2, Sm2O3, Li2CO3, Dy2O3, B2O3 or CeO; Optionally, the sintering aid comprises at least one oxide and at least one fluoride, and the mass ratio of the oxide to the fluoride is (1-5): (1-5); Optionally, the sintering aids are Y2O3, MgO and CaF2; Optionally, the sintering aids are Y2O3 and CaF2; Optionally, the sintering aids are CeO and CaF2; Optionally, the sintering aids are CeO, MgO and CaF2.

8. The preparation method according to claim 5, characterized in that During the hot pressing sintering, the heating rate is 30-60°C / min; Optionally, the sintering temperature is 1200-1300°C.

9. The preparation method according to claim 5 or 8, characterized in that: The method for reducing temperature and pressure includes step-by-step reduction in temperature and pressure: The first stage of cooling and pressure reduction is to reduce the temperature from 1200~1400℃ to 800~1000℃, and the pressure from 30~80MPa to 30~60MPa, and then keep the temperature and pressure for 10~20min; The second stage is cooling and pressure reduction: the temperature is reduced from 800~1000℃ to 400~700℃, and the pressure is reduced from 30~60MPa to 10~20MPa, and then kept at this temperature and pressure for 10~20min; The third stage is cooling and pressure reduction: cooling to room temperature with the furnace, and then releasing the pressure to normal pressure.

10. A heat dissipation substrate, characterized in that: The diamond aluminum nitride composite material comprises the diamond aluminum nitride composite material according to any one of claims 1 to 3.

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