High-thermal-conductivity black aluminum nitride ceramic substrate and preparation method and application thereof

Abstract

The application discloses a kind of high thermal conductivity black aluminum nitride ceramic substrate and preparation method thereof, belong to electronic information functional material technical field.The ceramic substrate is composed of the following mass percentage components:85wt%~99wt% aluminum nitride, 3wt%~12wt% silicon carbide, 1wt%~5wt% composite sintering aid, wherein composite sintering aid includes Y2O3 and Er2O3, molar ratio is 1:1~3:1.Preparation method includes slurry preparation, spray granulation, cold isostatic pressing, two-stage atmosphere sintering and post-processing, wherein the second stage sintering temperature is 1720~1800 DEG C.The application uses β-SiC particles as colorant and thermal conductivity enhancement phase simultaneously, constructs the dual-phase thermal conductivity network of "AlN main phase + SiC secondary phase", cooperates the synergistic deoxidizing effect of Y2O3 and Er2O3 composite aid and ≤1800 DEG C sintering temperature control, while realizing uniform black color, thermal conductivity is stably maintained at 210 W / (m·K) or more, solve the technical bottleneck of traditional black AlN ceramic "thermal conductivity must be degraded".

Description

Technical Field

[0001] This invention belongs to the field of electronic information functional materials technology, and in particular relates to an aluminum nitride ceramic substrate with a uniform black appearance and high thermal conductivity, which incorporates silicon carbide (SiC) phase and uses yttrium oxide-erbium oxide as a composite sintering aid, as well as its preparation method and application. Background Technology

[0002] Aluminum nitride (AlN) ceramics are widely recognized as ideal heat dissipation substrate materials for high-end electronic packaging due to their high theoretical thermal conductivity (320 W / (m·K)), matching coefficient of thermal expansion with silicon chips, and excellent electrical insulation properties. With the development of optoelectronic devices such as ultraviolet LEDs and lidar, packaging substrates also need to possess efficient absorption capabilities for stray light. However, conventional AlN ceramics are white, with a visible light reflectance of 25%–40%, which can cause severe internal optical crosstalk, reducing the light extraction efficiency and signal-to-noise ratio of the devices. Therefore, developing black AlN ceramic substrates that combine high thermal conductivity and excellent light-shielding properties has become a crucial technology that urgently needs to be mastered.

[0003] To obtain black AlN ceramics, the industry has developed four main technical routes: The first route is the transition metal oxide coloring route. This route achieves black coloring by adding transition metal oxides such as iron oxide (Fe2O3), cobalt oxide (CoO), nickel oxide (NiO), and manganese oxide (MnO2) to the AlN matrix. This was the earliest method adopted in the industry. However, the reaction of metal oxides with oxygen impurities at the grain boundaries of AlN forms a large amount of silicate glass phase with low thermal conductivity, low melting point, and high electrical resistance. This leads to increased phonon scattering, causing the thermal conductivity to plummet to 120~150 W / (m·K), a decrease of 30%~40%, thus negating AlN's advantages as a heat dissipation material. In addition, these metal ions are easily volatilized at high temperatures, which also leads to unstable sintering density.

[0004] The second technical route is the elemental silicon coloring route. Nippon Steel proposed in patent JP2001220241A to introduce 100~2000 ppm of elemental Si to achieve blackening (blackness reaching L*≤40), attempting to avoid the large-scale formation of low thermal conductivity glass phases. However, elemental Si will nitride to form Si3N4 in high-temperature nitrogen atmosphere, and the reaction is uncontrollable, resulting in poor color uniformity; moreover, the thermal conductivity of the generated Si3N4 is much lower than that of AlN, and it will form a large number of heterogeneous interfaces with the AlN matrix, generating additional interfacial thermal resistance; Si is only used as a colorant and cannot compensate for the grain boundary thermal resistance introduced by sintering aids—and the patent document does not record any technical means to enhance thermal conductivity by adding phases.

[0005] The third technical route is the SiC-AlN composite ceramic route. SiC is dark gray to black and has a high thermal conductivity of 120~490 W / (m·K), possessing the potential for both coloring and thermal conductivity. Early research used SiC as the main phase (50~80wt%) with a small amount of AlN added. For example, European patent EP0080213A2 discloses SiC-AlN high thermal conductivity ceramics with CaO, BaO, and SrO as additives. However, this approach resulted in a significant decrease in volume resistivity, failing to meet the insulation requirements of electronic packaging. Another study prepared a 60AlN-40SiC-3Y2O3 composite material using a hot-pressing method (Ceramics International, Vol.51, 2025), but the highest thermal conductivity reached was only 61.7 W / (m·K). Regarding the preparation process, Chinese patent CN119613122A discloses the preparation of AlN-SiC heat sink material by in-situ reaction of Si-Al alloy combined with spark plasma sintering, but the equipment and process thresholds are high, and the black coloring function is not addressed.

[0006] The fourth technical route is the rare earth oxide sintering aid route, with Y2O3 being widely used as a single sintering aid for AlN. Chinese patent CN118930279B discloses a scheme that uses erbium hydride (ErH3) as a precursor to generate highly active Er2O3 in situ and achieve synergistic deoxygenation with Y2O3. However, ErH3 is sensitive to water and oxygen, requiring high process safety, and it is only applicable to white AlN systems, not involving SiC coloring.

[0007] In summary, the existing technology has the following systemic defects: (1) Coloring with transition metal oxides leads to severe deterioration of thermal conductivity, coloring of elemental Si does not contribute to thermal conductivity enhancement, and the thermal conductivity of high-content SiC composites is all below 100 W / (m·K), which has formed a technical bias that "introducing SiC will inevitably reduce thermal conductivity"; (2) There is no literature that proposes a technical solution to achieve both coloring and thermal conductivity enhancement with low-content SiC; (3) There is a lack of sintering schemes that can simultaneously satisfy AlN densification and SiC phase stability under the same process framework; (4) The synergistic effect of specific Y2O3-Er2O3 ratio in the AlN-SiC system has not been disclosed.

[0008] The present invention aims to provide a high thermal conductivity black AlN ceramic substrate and its preparation method that overcomes the above-mentioned technical bottlenecks. Summary of the Invention

[0009] The purpose of this invention is to address the technical bottleneck of "inevitable degradation of thermal conductivity" in existing black AlN ceramics by providing a high thermal conductivity black aluminum nitride ceramic substrate and its preparation method. Specifically: (1) A dual-functional material scheme is provided in which β-SiC particles are used as both black colorant and thermally conductive enhancement phase, which overcomes the limitations of existing technologies such as the sudden drop in thermal conductivity caused by coloring of transition metal oxides, the lack of contribution to thermal conductivity enhancement by coloring of elemental Si, and the thermal conductivity of high-content SiC composites being less than 100 W / (m·K). (2) A Y2O3-Er2O3 composite sintering aid system is provided, which achieves deep grain boundary purification and low-temperature efficient densification of AlN-SiC system through a specific molar ratio, and solves the problem of limited oxygen removal effect of single rare earth aids; (3) A two-stage atmosphere sintering method is provided that can simultaneously achieve full densification of AlN matrix and thermodynamic stability of SiC phase under the same process framework, so as to solve the contradiction between the high temperature requirement of AlN densification and the nitriding decomposition temperature of SiC.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a high thermal conductivity black aluminum nitride ceramic substrate, characterized in that it comprises the following components by mass fraction: 85wt%~99wt% AlN, 3wt%~12wt% SiC, and 1wt%~5wt% composite sintering aid.

[0011] Furthermore, the composite sintering aid is a combination of Y2O3 and Er2O3, with a molar ratio of Y2O3 to Er2O3 of 1:1 to 3:1.

[0012] Furthermore, the SiC is β-SiC, with an average particle size D 50 The range is 0.05μm to 0.8μm.

[0013] Furthermore, the SiC accounts for 4wt% to 8wt% of the total mass of the raw materials.

[0014] Furthermore, the average particle size D of the AlN powder 50 The particle size ranges from 0.8μm to 1.5μm, with a carbon content of ≤300ppm and an oxygen content of ≤0.7wt%.

[0015] Furthermore, the AlN accounts for 88wt%~95wt% of the total mass of the raw materials.

[0016] Furthermore, the ceramic substrate exhibits a uniform black color, with an average light reflectance ≤14% in the wavelength range of 400nm~800nm, a thermal conductivity ≥210W / (m·K), and a volume resistivity ≥1×10⁻⁶. 14 Ω·cm.

[0017] This invention also provides a method for preparing a high thermal conductivity black aluminum nitride ceramic substrate, characterized by comprising the following steps: S1. Slurry preparation: AlN powder, SiC powder, and composite sintering aid are added to a non-aqueous solvent, and after adding a dispersant, the mixture is ball-milled to obtain a mixed slurry. S2. Spray granulation: The mixed slurry is spray-dried and granulated to obtain spherical particles with a flowability index ≥75; S3. Molding: The granulated powder is loaded into a mold and subjected to cold isostatic pressing at a pressure of 180~250MPa. S4. Atmosphere sintering: The green body is placed in a sintering furnace filled with high-purity nitrogen and sintered in two stages under a static positive pressure high-purity nitrogen atmosphere: In the first stage, the temperature is raised to 1550~1650℃ at a rate of 3~5℃ / min and held for 1~2h; in the second stage, the temperature is raised to 1720~1800℃ and held for 2~4h. S5. Post-processing: After cooling in the furnace, surface grinding and polishing are performed to obtain a black high thermal conductivity ceramic substrate with a surface roughness Ra≤0.2μm.

[0018] Furthermore, the non-aqueous solvent in S1 is one or more of anhydrous ethanol and isopropanol, and the dispersant is one or more of polyethyleneimine (PEI) and polyethylene glycol (PEG).

[0019] Furthermore, before the second stage of heating in S4, high-purity nitrogen is continuously introduced into the furnace at a flow rate of 0.5~2L / min for forced airflow treatment for 30~60min. Forced convection removes volatile impurities from the grain boundaries, thereby further purifying the grain boundary environment and removing free carbon. At the same time, the back pressure effect of nitrogen is used to suppress the thermodynamic decomposition of SiC.

[0020] A high thermal conductivity black aluminum nitride ceramic substrate, prepared by the above method, is suitable for packaging optoelectronic devices such as ultraviolet LEDs, LiDAR, and photodetectors.

[0021] The core technical principle of this invention is as follows: low-content β-SiC particles in the AlN matrix simultaneously act as a black colorant and a second thermally conductive channel reinforcing phase, combined with the synergistic deoxygenation and low-temperature densification effects of Y2O3-Er2O3 composite additives in a specific ratio, and a two-stage atmosphere sintering process at ≤1800℃, to systematically achieve the synergistic effect of the four functions of "coloring-thermal conduction-densification-SiC protection".

[0022] β-SiC is an indirect bandgap semiconductor with an indirect bandgap width of approximately 2.36 eV. Its broad-spectrum absorption in the visible light band originates from the synergistic effect of interband transition absorption, free carrier absorption, and defect-level assisted absorption. Simultaneously, the high refractive index of SiC (approximately 2.5–3.5) and the refractive index of the AlN matrix (approximately 2.1) form a refractive index mismatch interface. Incident light undergoes multiple scattering at the interface, significantly increasing the equivalent optical path length. This results in near-complete cumulative absorption across the entire wavelength range, macroscopically manifesting as a uniform black color with low reflectivity. Regarding thermal conductivity, SiC itself possesses extremely high thermal conductivity (120–490 W / (m·K)). Uniformly dispersing a suitable amount (4–8 wt%) of submicron β-SiC particles within the AlN matrix can construct a two-phase thermally conductive network of "AlN main phase + SiC secondary phase". In this network, SiC particles act as a second thermally conductive channel, effectively compensating for the grain boundary thermal resistance caused by the addition of sintering aids, thus maintaining the overall thermal conductivity of the composite material at a high level. This is a key technical feature that distinguishes this invention from elemental Si coloring schemes—Si not only does not contribute to enhanced thermal conductivity, but the Si3N4 generated by its nitridation actually introduces additional interfacial thermal resistance.

[0023] Y₂O₃ reacts with the Al₂O₃ oxide layer on the surface of AlN particles to form a Y-Al-O liquid phase (such as YAG, YAP, YAM, etc.), which promotes densification and achieves preliminary deoxygenation through liquid phase sintering. The addition of Er₂O₃ has the following synergistic effects: First, Er… 3+ With Y 3+ Competition for coordination in the liquid phase lowers the eutectic formation temperature of the liquid phase, allowing the liquid phase to be fully generated and flowed at lower temperatures, thus achieving a relative density of ≥99% below 1780℃. Secondly, Er2O3 can effectively react with the Al2O3 oxide layer on the AlN surface to form an Er-Al-O liquid phase, which together with the Y-Al-O liquid phase constitutes a composite liquid phase system. Through capillary action, oxygen impurities are more efficiently migrated from the AlN grain interface to the three-way intersection of grain boundaries, reducing the interfacial oxygen content and grain boundary glass phase thickness between AlN grains, thereby significantly reducing phonon interface scattering.

[0024] When the molar ratio of Y₂O₃ to Er₂O₃ is within a specific range of 1:1 to 3:1, the aforementioned synergistic effect is optimal, and the thermal conductivity can be increased by more than 20 W / (m·K) compared to Y₂O₃ alone, and by more than 37 W / (m·K) compared to Er₂O₃ alone. When the molar ratio exceeds this range (e.g., 22:1), the Er₂O₃ content is too low, and the effects of decreasing the liquid phase eutectic temperature and enhancing interfacial deoxygenation are not significant; the thermal conductivity is only close to the level of Y₂O₃ alone. This invention introduces Er in the form of Er₂O₃ instead of ErH₃, avoiding the process safety issues of hydrides being sensitive to water and oxygen and flammable. At the same time, the direct oxide combination of Er₂O₃ and Y₂O₃ is easier for industrial weighing and mixing.

[0025] In the specific multi-component system AlN-SiC-Y2O3-Er2O3, the presence of the rare earth liquid phase accelerates mass transport and interfacial reaction kinetics, making the nitridation decomposition of SiC perceptible at around 1820℃—significantly lower than the thermodynamic stability boundary of the pure SiC system in nitrogen (above 1840℃). This invention ensures the thermodynamic stability of the SiC phase during sintering through the synergistic effect of the following two aspects: First, the sintering temperature in the second stage is strictly controlled within a safe window of 1720~1800℃. The Y2O3-Er2O3 composite additive lowers the liquid phase formation temperature and enhances the densification driving force, enabling a relative density of ≥99% to be achieved within this temperature range, eliminating the need for the high temperature of 1800~1900℃ required for traditional AlN sintering.

[0026] Second, a forced nitrogen flow field treatment (0.5~2L / min, 30~60min) is implemented before the second stage of heating. Forced convection removes volatile impurities and free carbon from grain boundaries, while maintaining the nitrogen back pressure in the furnace, thus suppressing the nitriding decomposition of SiC from both kinetic and thermodynamic perspectives.

[0027] In summary, the innovative points of this invention are: 1. Pioneering low-content β-SiC "coloring-thermal conductivity" bifunctional phase Unlike traditional transition metal oxide coloring (which leads to a halving of thermal conductivity), elemental Si coloring (which does not contribute to thermal conductivity and generates low-thermal-conductivity Si3N4, introducing interfacial thermal resistance, JP2001220241A), and high-content SiC-AlN composite schemes (with thermal conductivity generally below 100 W / (m·K)), this invention proposes for the first time to simultaneously achieve uniform black coloring (reflectivity ≤14%) and construct a "AlN main phase + SiC secondary phase" two-phase thermally conductive network using 4~8wt% low-content β-SiC particles in an AlN matrix. SiC not only acts as a colorant but also as a second thermally conductive channel, effectively compensating for the grain boundary thermal resistance formed by the addition of sintering aids, enabling the material's thermal conductivity to be stably maintained at 210 W / (m·K). With a thermal conductivity exceeding W / (m·K), this invention completely solves the technical problem of AlN thermal conductivity being halved due to traditional metal oxide coloring. This concept breaks through the technical bias in existing literature that "introducing SiC into AlN will irreversibly sacrifice thermal conductivity," and the thermal conductivity can reach 3 to 4 times that of existing AlN-SiC composite materials.

[0028] 2. Synergistic grain boundary purification and low-temperature densification of Y2O3-Er2O3 in specific ratios Unlike single rare earth additives which have limited deoxygenation effects, or those that introduce Er via hydrides (ErH3, CN118930279B) which raise process safety concerns, this invention combines Er2O3 oxide with Y2O3 in a specific molar ratio of 1:1 to 3:1. This synergistic effect lowers the liquidus eutectic temperature and enhances the migration efficiency of oxygen impurities at the interface, achieving a relative density of ≥99% below 1780℃. When the ratio deviates from this range, the synergistic effect weakens significantly (e.g., when Y:Er=22:1, the thermal conductivity is only 198 W / (m·K)).

[0029] 3. The critical window for SiC nitriding in the AlN-SiC-rare earth system and the synergistic process of "low-temperature densification + SiC protection" Unlike existing AlN-SiC composite ceramics, which mostly rely on special processes such as hot pressing or spark plasma sintering at temperatures above 1800℃, this invention is the first to discover that in this specific multi-component system, due to the accelerated interfacial reaction kinetics of rare earth liquid phases, the nitriding degradation of SiC is already noticeable at 1820℃, and the safe upper limit should be lowered to 1800℃. Accordingly, by using Y2O3-Er2O3 composite additives to lower the densification temperature, combined with back pressure protection from forced nitrogen flow field treatment, and within the universal process framework of atmospheric pressure sintering, this invention systematically resolves for the first time the contradiction between the high-temperature densification requirements of AlN and the risk of low-temperature nitriding decomposition of SiC.

[0030] 4. Integrated solution with four functions: coloring, thermal conductivity, densification, and SiC protection. The three core technical features of this invention are: the Y2O3-Er2O3 composite additive lowers the densification temperature, providing a thermodynamically safe environment for SiC; β-SiC constructs a second thermally conductive channel to compensate for the grain boundary thermal resistance introduced by the additive; and low-temperature sintering reduces the risk of β-SiC nitridation, ensuring the integrity of the two-phase thermally conductive network. The absence of any one of these features will cause a sharp drop in thermal conductivity of 40-60 W / (m·K), and only when all three features are present can the thermal conductivity stably reach above 210 W / (m·K).

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Overcoming the thermal conductivity bottleneck of black AlN ceramics, achieving a balance between high thermal conductivity and excellent light-shielding. By introducing 4-8 wt% β-SiC micropowder into the AlN matrix, a two-phase thermally conductive network of "AlN main phase + SiC secondary phase" is constructed. SiC serves as both a colorant and a thermally conductive reinforcing phase, ensuring that the material's thermal conductivity is stably maintained above 210 W / (m·K) (with a preferred range of up to 230 W / (m·K)). This represents a 40%-75% improvement compared to traditional transition metal oxide coloring schemes (120-150 W / (m·K)) and a 3-4 times improvement compared to existing AlN-SiC composite materials (55-62 W / (m·K)). Simultaneously, the product's average reflectivity in the visible light band can be controlled below 14%, with a preferred scheme as low as 12.2%. It exhibits a uniform black to jet-black color, effectively absorbing stray light and significantly improving the light extraction efficiency and signal-to-noise ratio of photosensitive devices such as ultraviolet LEDs, LiDAR, and photodetectors.

[0032] 2. Achieving deep grain boundary purification improves the material's thermal conductivity and electrical insulation reliability. A Y₂O₃-Er₂O₃ composite rare earth additive system (molar ratio 1:1~3:1), combined with two-stage atmosphere sintering and forced nitrogen flow field treatment, effectively migrates oxygen impurities from the AlN grain surface to the tri-junction of grain boundaries via a liquid-phase sintering mechanism. This reduces the thickness of the glassy phase at grain boundaries and phonon scattering centers, resulting in clean, dense ceramic grain boundaries with a volume resistivity ≥1×10⁻⁶. 14 Ω·cm, exhibiting excellent stability under long-term high-temperature operation.

[0033] 3. Effectively solves the problem of SiC nitriding decomposition in the high-temperature sintering environment of AlN. By strictly controlling the second-stage sintering temperature within the safe window of 1720~1800℃, and using Y2O3-Er2O3 composite additives to achieve sufficient densification at a lower temperature, combined with back pressure protection from forced nitrogen flow field treatment, it is ensured that SiC exists stably as an independent high thermal conductivity phase in the AlN matrix, providing process assurance for the structural integrity of the two-phase thermally conductive network.

[0034] 4. Excellent mechanical properties and good processing adaptability. Due to the pinning effect of SiC particles on the grain boundaries of the AlN matrix, the abnormal growth of AlN grains during sintering is suppressed, resulting in a fine-grain strengthening effect. At the same time, the high hardness of the SiC phase itself contributes to dispersion strengthening. Combined with the high-density microstructure, the flexural strength of the ceramic substrate can reach 370~410MPa, and the Vickers hardness is >12GPa. This can meet the requirements of post-processing such as precision scribing and drilling, and reduce the packaging breakage rate.

[0035] 5. Strong process compatibility, suitable for large-scale production. The AlN and SiC raw materials used are all commercially available mature powders, eliminating the need for expensive nano-scale raw materials or special precursors. The preparation process (ball milling, granulation, cold isostatic pressing, and atmospheric sintering) is highly compatible with traditional AlN ceramic production lines. Industrial scale-up can be achieved simply by adjusting the sintering aid formula and sintering temperature profile. The new process has a short introduction cycle and low investment threshold.

[0036] 6. Environmentally friendly and non-toxic, meeting green manufacturing requirements. Using environmentally friendly inorganic non-metallic material β-SiC to replace traditional coloring schemes containing heavy metal ions such as Co and Ni, the entire preparation process produces no toxic or harmful emissions. The product complies with RoHS and other environmental directives, making it suitable for applications with stringent environmental compliance requirements, such as medical electronics and automotive electronics. Attached Figure Description

[0037] Figure 1 A process flow diagram for preparing a high thermal conductivity black aluminum nitride ceramic substrate. Detailed Implementation

[0038] The endpoints and values ​​of the ranges disclosed herein are not limited to these precise ranges, but should be understood to cover values ​​close to these ranges. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0039] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0040] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0041] The present invention will be further described in detail below with reference to specific embodiments. The AlN powder used in the following embodiments has an average particle size of 1.2 μm, an oxygen content of 0.6 wt%, and a carbon content of 300 ppm; the SiC powder is β-SiC with a purity of 99.9%.

[0042] Example 1 This embodiment prepares a high thermal conductivity black aluminum nitride ceramic substrate. The raw materials include: AlN 93wt%, SiC 4wt%, Y2O3 1.5wt%, Er2O3 1.5wt% (Y2O3:Er2O3 molar ratio = 1.69:1), and SiC particle size 0.3μm, wherein the SiC particle size D 50 =0.3μm.

[0043] The preparation method is as follows: S1. Slurry preparation: AlN powder, SiC powder, and composite sintering aid are added to anhydrous ethanol, followed by the addition of dispersant polyethyleneimine. The mixture is then ball-milled for 8 hours to obtain a mixed slurry. S2. Spray granulation: The mixed slurry is spray-dried and granulated to obtain spherical particles with a flowability index ≥75; S3. Molding: The granulated powder is loaded into the mold and subjected to cold isostatic pressing at a pressure of 200 MPa. S4. Atmosphere sintering: The green body is placed in a sintering furnace filled with high-purity nitrogen. Under a static positive pressure high-purity nitrogen atmosphere, a two-stage sintering process is adopted: In the first stage, the temperature is raised to 1600℃ at a rate of 3~5℃ / min and held for 1.5h; Before the second stage heating, high-purity nitrogen is continuously introduced into the furnace at a flow rate of 0.5~2L / min for forced airflow treatment for 50min; In the second stage, the temperature is raised to 1780℃ and held for 3h. S5. Post-processing: After cooling in the furnace, surface grinding and polishing are performed to obtain a black high thermal conductivity ceramic substrate with a surface roughness Ra≤0.2μm.

[0044] Example 2 This embodiment prepares a high thermal conductivity black aluminum nitride ceramic substrate. The raw materials include: AlN 92wt%, SiC 5wt%, Y2O3 1.5wt%, Er2O3 1.5wt%, wherein the SiC particle size D 50 =0.3μm.

[0045] The preparation method is the same as in Example 1.

[0046] Example 3 This embodiment prepares a high thermal conductivity black aluminum nitride ceramic substrate. The raw materials include: AlN 91wt%, SiC 6wt%, Y2O3 1.5wt%, Er2O3 1.5wt%, wherein the SiC particle size D 50 =0.3μm.

[0047] The preparation method is the same as in Example 1.

[0048] Example 4 This embodiment prepares a high thermal conductivity black aluminum nitride ceramic substrate. The raw materials include: AlN 89wt%, SiC 8wt%, Y2O3 1.5wt%, Er2O3 1.5wt%, wherein the SiC particle size D 50 =0.3μm.

[0049] The preparation method is the same as in Example 1.

[0050] Example 5 This embodiment prepares a high thermal conductivity black aluminum nitride ceramic substrate. The raw materials include: AlN 88wt%, SiC 7wt%, Y2O3 3wt%, Er2O3 2wt% (Y2O3:Er2O3 molar ratio = 2.54:1), wherein the SiC particle size D 50 =0.05μm.

[0051] The preparation method is the same as in Example 1.

[0052] Example 6 This embodiment prepares a high thermal conductivity black aluminum nitride ceramic substrate. The raw materials include: AlN 88wt%, SiC 7wt%, Y2O3 3wt%, Er2O3 2wt%, wherein the SiC particle size D 50 =0.2μm.

[0053] The preparation method is the same as in Example 1.

[0054] Example 7 This embodiment prepares a high thermal conductivity black aluminum nitride ceramic substrate. The raw materials include: AlN 88wt%, SiC 7wt%, Y2O3 3wt%, Er2O3 2wt%, wherein the SiC particle size D 50 =0.5μm.

[0055] The preparation method is the same as in Example 1.

[0056] Example 8 This embodiment prepares a high thermal conductivity black aluminum nitride ceramic substrate. The raw materials include: AlN 88wt%, SiC 7wt%, Y2O3 3wt%, Er2O3 2wt%, wherein the SiC particle size D 50 =0.8μm.

[0057] The preparation method is the same as in Example 1.

[0058] The performance test results of Examples 1-4 are shown in Table 1. The correspondence between color and reflectance is based on the Munsell Color System.

[0059] Table 1 Performance testing of ceramic substrates with different SiC contents

[0060] As shown in Table 1, the reflectivity continuously decreases with increasing SiC content, and the color transitions from black to jet black. The highest point occurs at 6%, likely due to the most complete two-phase network at this level. While there are more heat conduction channels at 8%, more interfaces are also introduced, leading to a slight increase in total interfacial thermal resistance. The overall thermal conductivity remains at a high level of ≥210 W / (m·K), demonstrating that the secondary heat conduction channels constructed with an appropriate amount of SiC effectively compensate for grain boundary thermal resistance.

[0061] The performance test results of Examples 5-8 are shown in Table 2. Table 2 Performance testing of ceramic substrates with different SiC particle sizes

[0062] As shown in Table 2, particle size has an inverse effect on reflectivity and thermal conductivity. In terms of optical properties, larger particle sizes result in lower reflectivity (deeper color), consistent with the Mie scattering law—when the particle size (0.4~0.8 μm) is comparable to the wavelength of visible light, forward scattering dominates, and the light is absorbed multiple times within the matrix, reducing reflectivity. Regarding thermal conductivity, smaller particle sizes lead to higher thermal conductivity, resulting in greater dispersion of fine SiC particles within the matrix and a greater number of thermal channels per unit mass. In terms of mechanical properties, larger particle sizes result in higher strength. This invention preferably uses a particle size range of 0.05~0.8 μm, within which the aforementioned properties can be flexibly adjusted according to specific application requirements.

[0063] Comparative Example 1 This comparative example prepares an aluminum nitride ceramic substrate, the raw materials of which include: AlN 91wt%, SiC 4wt%, Y2O3 3wt%, wherein the SiC particle size D 50 =0.3μm.

[0064] The preparation method is the same as in Example 1.

[0065] Test results: Reflectivity 13.8%, thermal conductivity 195 W / (m·K), volume resistivity 1.1×10⁻⁶ 14 Ω·cm, flexural strength 370 MPa.

[0066] Comparative Example 2 This comparative example prepares an aluminum nitride ceramic substrate, the raw materials of which include: AlN 91wt%, SiC 4wt%, Er2O3 3wt%, wherein the SiC particle size D 50 =0.3μm.

[0067] The preparation method is the same as in Example 1.

[0068] Test results: Reflectivity 14.2%, thermal conductivity 178 W / (m·K), volume resistivity 0.9×10⁻⁶ 14 Ω·cm, flexural strength 345 MPa.

[0069] Comparative Example 3 This comparative example prepares an aluminum nitride ceramic substrate. The raw materials include: AlN 91wt%, SiC 4wt%, Y2O3 2.5wt%, Er2O3 0.5wt%, wherein the SiC particle size D 50 =0.3μm.

[0070] The preparation method is the same as in Example 1.

[0071] Test results: Reflectivity 13.8%, density 3.27 g / cm³ 3 Thermal conductivity 198 W / (m·K), volume resistivity 1×10⁻⁶ 14 Ω·cm, flexural strength 372 MPa.

[0072] Comparative Example 4 This comparative example prepares an aluminum nitride ceramic substrate. The raw materials include: AlN 96wt%, elemental Si powder 0.15wt% (i.e., 1500 ppm), Y2O3 4.85wt%, wherein the particle size D of the Si powder is... 50 =0.3μm.

[0073] The preparation method is the same as in Example 1.

[0074] Test results: Reflectivity 17.5%, thermal conductivity 188 W / (m·K), volume resistivity 1×10⁻⁶ 14 Ω·cm, flexural strength 365 MPa. Compared with Example 1, thermal conductivity decreased by 30 W / (m·K), and reflectivity increased by 4 percentage points.

[0075] Comparative Example 5 This comparative example prepares an aluminum nitride ceramic substrate. The raw materials include: AlN 93wt%, SiC 4wt%, Y2O3 1.5wt%, Er2O3 1.5wt% (Y2O3:Er2O3 molar ratio = 1.69:1), and SiC particle size 0.3μm, wherein the SiC particle size D 50 =0.3μm.

[0076] The preparation method is the same as in Example 1, but the forced gas flow treatment of high-purity nitrogen is not set in S4.

[0077] Test results: Reflectivity 15.1%, thermal conductivity 199 W / (m·K), volume resistivity 1.1×10⁻⁶ 14The thermal conductivity was Ω·cm and the bending strength was 377 MPa. Compared with Example 1, the thermal conductivity was significantly reduced, indicating that the forced airflow field treatment effectively removed volatile impurities and free carbon from the grain boundaries through forced convection, while the dynamic nitrogen back pressure also played an auxiliary role in suppressing the slight nitriding of SiC.

[0078] Comparing the data from Comparative Examples 1 and 2 with those from Example 1, it can be found that the thermal conductivity of Example 1 is 23 W / (m·K) higher than that of the Y₂O₃-only scheme and 40 W / (m·K) higher than that of the Er₂O₃-only scheme. This improvement far exceeds the level expected by linear superposition, demonstrating a significant synergistic effect between Y₂O₃ and Er₂O₃. The mechanism lies in the fact that the coexistence of Er₂O₃ and Y₂O₃ in the liquid phase lowers the eutectic temperature and simultaneously enhances the migration efficiency of interfacial oxygen impurities to the tri-junction. As shown in Comparative Example 3, when the Y:Er molar ratio deviates from the range of 1:1 to 3:1, the Er₂O₃ content is too low, the synergistic effect is significantly weakened, and the thermal conductivity approaches the level of Y₂O₃ alone. The above comparisons indicate that the selection of a specific Y₂O₃-Er₂O₃ ratio has a crucial impact on the technical effect of this invention.

[0079] The embodiments described above are merely preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A high thermal conductivity black aluminum nitride ceramic substrate, characterized in that, The composition includes the following components by mass fraction: 85wt%~99wt% AlN, 3wt%~12wt% SiC, and 1wt%~5wt% composite sintering aids; The composite sintering aid is a combination of Y2O3 and Er2O3, with a molar ratio of Y2O3 to Er2O3 of 1:1 to 3:

1.

2. The high thermal conductivity black aluminum nitride ceramic substrate according to claim 1, characterized in that, The SiC is β-SiC, with an average particle size D. 50 The range is 0.05μm to 0.8μm.

3. The high thermal conductivity black aluminum nitride ceramic substrate according to claim 1, characterized in that, The SiC accounts for 4wt% to 8wt% of the total mass of the raw materials.

4. The high thermal conductivity black aluminum nitride ceramic substrate according to claim 1, characterized in that, The average particle size D of the AlN powder 50 The particle size ranges from 0.8μm to 1.5μm, with a carbon content of ≤300ppm and an oxygen content of ≤0.7wt%.

5. The high thermal conductivity black aluminum nitride ceramic substrate according to claim 1, characterized in that, The AlN accounts for 88wt% to 95wt% of the total mass of the raw materials.

6. The high thermal conductivity black aluminum nitride ceramic substrate according to claim 1, characterized in that, The ceramic substrate exhibits a uniform black color, with an average light reflectance ≤14% in the wavelength range of 400nm~800nm, a thermal conductivity ≥210W / (m·K), and a volume resistivity ≥1×10⁻⁶. 14 Ω·cm.

7. A method for preparing a high thermal conductivity black aluminum nitride ceramic substrate according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Slurry preparation: AlN powder, SiC powder, and composite sintering aid are added to a non-aqueous solvent, and after adding a dispersant, the mixture is ball-milled to obtain a mixed slurry. S2. Spray granulation: The mixed slurry is spray-dried and granulated to obtain spherical particles with a flowability index ≥75; S3. Molding: The granulated powder is loaded into a mold and subjected to cold isostatic pressing at a pressure of 180~250MPa. S4. Atmosphere sintering: The green body is placed in a sintering furnace filled with high-purity nitrogen and sintered in two stages under a static positive pressure high-purity nitrogen atmosphere: In the first stage, the temperature is raised to 1550~1650℃ at a rate of 3~5℃ / min and held for 1~2h; in the second stage, the temperature is raised to 1720~1800℃ and held for 2~4h. S5. Post-processing: After cooling in the furnace, surface grinding and polishing are performed to obtain a black high thermal conductivity ceramic substrate with a surface roughness Ra≤0.2μm.

8. The preparation method according to claim 7, characterized in that, Before the second stage of heating in S4, high-purity nitrogen is continuously introduced into the furnace at a flow rate of 0.5~2L / min for forced airflow field treatment for 30~60min.

9. A high thermal conductivity black aluminum nitride ceramic substrate, characterized in that, It is prepared by the preparation method described in any one of claims 7 to 8.

10. An application of a high thermal conductivity black aluminum nitride ceramic substrate, characterized in that, It is suitable for packaging optoelectronic devices such as ultraviolet LEDs, LiDAR, and photodetectors.

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