High-thermal-conductivity low-expansion modified electronic ceramic substrate and preparation method thereof

Abstract

This invention relates to the field of electronic packaging ceramic materials technology, and discloses a high thermal conductivity, low expansion modified electronic ceramic substrate, comprising a modified composite ceramic matrix and nanoscale bonding transition layers grown in situ on both sides of the modified composite ceramic matrix; the modified composite ceramic matrix comprises, by mass parts: 65-85 parts of main crystalline phase, 10-25 parts of low expansion regulating phase, 2-8 parts of nano-thermal conductivity reinforcing phase, and 3-10 parts of composite sintering aid. This invention uses a composite of hydroxylated modified AlN and coupled modified Al₂O₃ as the main crystalline phase, which retains the intrinsic high thermal conductivity of AlN while significantly reducing raw material costs and sintering difficulty through Al₂O₃. Simultaneously, through hydrothermal hydroxylation modification, a dense hydroxyl protective layer is constructed on the surface of the AlN powder, completely solving the industry pain point of easy hydrolysis of AlN powder, improving powder storage stability by more than 10 times, and significantly improving batch-to-batch consistency of substrate performance.

Description

Technical Field

[0001] This invention relates to the field of electronic packaging ceramic materials technology, specifically to a high thermal conductivity, low expansion modified electronic ceramic substrate and its preparation method. Background Technology

[0002] With the rapid development of third-generation semiconductor devices towards higher power, higher density, miniaturization, and higher reliability, the electronic packaging substrate, as a core component for heat dissipation and structural support, directly determines the operating limits and lifespan of the devices. Currently, commercial electronic ceramic substrates mainly face the following technical bottlenecks:

[0003] Alumina (Al2O3) substrates: While the fabrication process is mature and inexpensive, their room temperature thermal conductivity is only 20-35 W / m·K, which cannot meet the heat dissipation requirements of high-power devices; their coefficient of thermal expansion is approximately 7.2 × 10⁻⁻⁻⁶. 6 / K, with Si chip (3.5×10⁻ 6 / K), GaN chip (5.6×10⁻ 6 The / K) matching is extremely poor, and the device is prone to generating huge thermal stress during operation, which leads to interface cracking and device failure.

[0004] Aluminum nitride (AlN) substrate: theoretical thermal conductivity up to 320 W / m·K, commercial products have thermal conductivity of 170-230 W / m·K, and a coefficient of thermal expansion of approximately 4.5 × 10⁻⁻⁻⁴. 6 / K, but it has fatal flaws: First, the powder is expensive and the sintering temperature needs to be above 1800℃, making the preparation cost extremely high; second, AlN powder is very easy to hydrolyze, and Al(OH)3 is easily generated during storage and preparation, which leads to a sharp decline in the thermal conductivity and mechanical properties of the substrate; third, the bonding force with the metallization layer is insufficient, and interface peeling is easy to occur after long-term hot and cold cycles, resulting in poor reliability.

[0005] Silicon nitride (Si3N4) substrates have excellent mechanical properties and fracture toughness, but their room temperature thermal conductivity is only 80-120 W / m・K, which cannot meet the heat dissipation requirements of ultra-high power devices. In addition, they require high temperature and high pressure atmosphere sintering, and the manufacturing cost is much higher than the previous two types of substrates, making it difficult to promote on a large scale.

[0006] To address the aforementioned issues, existing technologies often employ single modification methods: such as adding a low-expansion phase to the AlN matrix to regulate the coefficient of thermal expansion, but this often leads to a significant decrease in thermal conductivity; or adding thermally conductive enhancing phases such as carbon materials and boron nitride, but these are prone to powder agglomeration and poor compatibility with the matrix, making it impossible to form a continuous thermal conductivity pathway, thus limiting the modification effect; at the same time, the core pain points of AlN powder hydrolysis and poor substrate metallization bonding force have not been solved, making it difficult to achieve a balance of high thermal conductivity, low expansion, high reliability, and low cost.

[0007] Therefore, developing an electronic ceramic substrate that combines ultra-high thermal conductivity, low thermal expansion coefficient precisely matched to semiconductor chips, excellent mechanical properties, high metallization bonding strength, and low cost and scalable fabrication has become an urgent need in the field of high-power third-generation semiconductor packaging. Summary of the Invention

[0008] (a) Technical problems to be solved

[0009] To address the shortcomings of existing technologies, this invention provides a high thermal conductivity, low expansion modified electronic ceramic substrate and its preparation method, thus solving the problems mentioned above.

[0010] (II) Technical Solution

[0011] To achieve the above objectives, the present invention provides the following technical solution: a modified electronic ceramic substrate with high thermal conductivity and low expansion, comprising a modified composite ceramic substrate and a nanoscale bonding transition layer grown in situ on both sides of the modified composite ceramic substrate;

[0012] The modified composite ceramic matrix comprises the following components by mass: 65-85 parts of main crystalline phase, 10-25 parts of low expansion regulating phase, 2-8 parts of nano-thermal conductive reinforcing phase, and 3-10 parts of composite sintering aid.

[0013] The main crystalline phase is a mixture of surface-hydroxylated modified aluminum nitride powder and surface-silane-coupled modified alumina powder in a mass ratio of 3-5:1.

[0014] The low-expansion regulating phase is a mixture of negative thermal expansion tungsten zirconate powder and pre-calcined low-expansion cordierite powder in a mass ratio of 1:2-4.

[0015] The nano-thermal conductive reinforcing phase is composed of hydroxylated modified boron nitride nanosheets and few-layer graphene in a mass ratio of 4-6:1.

[0016] Preferably, in the main crystalline phase, the particle size D50 of the hydroxylated modified aluminum nitride powder is 1-2 μm, the hydroxylation modification is hydrothermal modification using an anhydrous ethanol-deionized water mixed system, and the surface hydroxyl coverage is ≥85%;

[0017] The particle size D50 of the silane coupling modified alumina powder is 0.5-1μm. It is modified with KH550 or KH560 silane coupling agent, and the coating rate of the coupling agent is ≥90%.

[0018] Preferably, in the low-expansion control phase, the tungsten zirconate powder is a nano-sized powder with a particle size D50 of 100-300 nm;

[0019] The cordierite powder has a particle size D50 of 0.8-1.5μm. After pre-calcination in air at 1050-1150℃ for 2-3 hours, the purity of the cordierite phase is ≥98%.

[0020] Preferably, in the nano-thermal conductive enhancement phase, the hydroxylated modified boron nitride nanosheets have 3-8 layers and a sheet diameter of 0.5-3 μm;

[0021] The few-layer graphene has 1-5 layers and a sheet diameter of 1-4 μm. Both are hydroxylated and modified, with a surface hydroxyl content ≥2.5 mmol / g.

[0022] Preferably, the composite sintering aid is a Y2O3-CaO-MgO ternary system with a mass ratio of 4-6:2-3:1-2 and a powder particle size D50 of 0.3-0.8 μm.

[0023] Preferably, the nanoscale bonding transition layer is an Al-ON covalent bonding composite transition layer with a thickness of 50-120 nm. The transition layer and the ceramic substrate are an in-situ integrated structure with an interfacial bonding strength ≥50 MPa and a substrate surface roughness Ra ≤0.2 μm.

[0024] A method for preparing a modified electronic ceramic substrate with high thermal conductivity and low expansion includes the following steps:

[0025] S1. Powder pretreatment: Surface modification of main crystalline phase powder, pre-sintering modification of low expansion control phase, dispersion modification of nano thermally conductive enhancement phase, and mixing and grinding of composite sintering aid are completed respectively.

[0026] S2. Mixing and slurry preparation: Add the pretreated powders to the solvent according to the ratio, add binder, plasticizer and dispersant, and obtain a uniform and stable ceramic slurry by planetary ball milling. After sieving, vacuum degassing is performed.

[0027] S3, Casting: The degassed ceramic slurry is cast using a casting process to obtain a ceramic green belt with uniform thickness;

[0028] S4. Debinding and pre-sintering: After the ceramic green body is cut, it is placed in a nitrogen atmosphere furnace and heated in stages to complete the debinding and pre-sintering, so as to obtain a pre-sintered green body without cracks or deformation.

[0029] S5. Atmospheric pressure sintering densification: The pre-sintered green body is placed in a high-purity nitrogen atmosphere and sintered at low temperature under atmospheric pressure to complete the densification treatment and obtain the ceramic substrate.

[0030] S6. Surface in-situ modification: After polishing and cleaning the densified ceramic substrate, it is activated by plasma and subjected to in-situ hydrothermal reaction to grow a nanoscale bonding transition layer on the substrate surface, ultimately obtaining a modified electronic ceramic substrate with high thermal conductivity and low expansion.

[0031] Preferably, the specific process for powder pretreatment in step S1 is as follows:

[0032] Main crystalline phase modification: Aluminum nitride powder is added to a mixed solution of anhydrous ethanol and deionized water in a volume ratio of 8-10:1, the pH is adjusted to 8.5-9.5, and the mixture is subjected to hydrothermal reaction at 75-85℃ for 3-5 hours. After filtration and washing, the mixture is vacuum dried at 120℃ for 10-14 hours to obtain hydroxylated modified aluminum nitride powder.

[0033] Alumina powder is added to anhydrous ethanol, and 1.5-2.5% of silane coupling agent by weight of the powder is added. The mixture is ultrasonically dispersed at 55-65℃ for 20-40 min, stirred and reacted for 1.5-2.5 h, filtered and dried to obtain coupling-modified alumina powder. The main crystalline phase powder is obtained by mixing according to the formula.

[0034] Low expansion control phase pretreatment: Tungsten zirconate powder and cordierite powder are mixed in proportion, pre-calcined in air at 1050-1150℃ for 2-3 hours, cooled in the furnace and then ball-milled to the target particle size to obtain low expansion control phase powder.

[0035] Modification of nano-thermal conductive reinforcing phase: Boron nitride nanosheets and few-layer graphene were added to deionized water in a certain ratio, and 0.8-1.2% sodium polyacrylate dispersant by weight of the powder was added. The mixture was ultrasonically exfoliated for 2-4 hours, filtered, and vacuum dried to obtain modified nano-thermal conductive reinforcing phase powder.

[0036] Pretreatment of sintering aid: Y2O3, CaO and MgO are mixed in proportion, ball-milled for 3-5 hours, and dried to obtain composite sintering aid powder.

[0037] Preferably, the specific process parameters for steps S2-S5 are as follows:

[0038] S2. Mixing and slurry preparation: Using anhydrous ethanol as solvent, add 4-6% PVB binder and 1.5-2.5% dibutyl phthalate plasticizer by weight of powder, and ball mill for 10-14 hours at a ball-to-powder ratio of 4-6:1 and a speed of 250-350 rpm to obtain a ceramic slurry with a solid content of 55-60%. Pass the slurry through a 200-300 mesh sieve and degas it under vacuum for 20-40 minutes.

[0039] S3. Casting: The doctor blade gap is 0.2-0.5mm, the casting speed is 0.5-1.0m / min, and the segmented drying temperature is 60℃, 80℃, 100℃, and 120℃ to obtain a ceramic green belt with uniform thickness.

[0040] S4. Debinding and pre-sintering: Under a nitrogen atmosphere, heat to 240-260℃ at a rate of 1.5-2.5℃ / min and hold for 1.5-2.5h;

[0041] Increase the temperature to 580-620℃ at a rate of 0.8-1.2℃ / min and hold for 3-5 hours;

[0042] Heat to 950-1050℃ at a rate of 2.5-3.5℃ / min, hold for 1.5-2.5 hours, and then cool with the furnace.

[0043] S5. Atmospheric pressure sintering densification: Under atmospheric pressure and high-purity nitrogen atmosphere, the temperature is increased to 1150-1250℃ at 4-6℃ / min and held for 0.5-1.5h.

[0044] Heat to 1650-1750℃ at a rate of 2.5-3.5℃ / min, hold for 4-8 hours, and then cool with the furnace.

[0045] Preferably, the specific process of surface in-situ modification in step S6 is as follows: the densified ceramic substrate is polished to a mirror finish on both sides, ultrasonically cleaned with anhydrous ethanol for 10-20 minutes, dried, and then placed in a plasma reaction chamber for activation treatment with a mixed plasma of argon-nitrogen volume ratio of 3-5:1 for 10-20 minutes, with a treatment power of 150-250W.

[0046] The activated substrate was placed in a hydrothermal reactor, and a mixed solution of anhydrous ethanol and deionized water in a volume ratio of 1:1 was added. The pH was adjusted to 9.5-10.5, and the hydrothermal reaction was carried out at 130-150℃ for 2-4 hours. After removal, the substrate was rinsed with deionized water and vacuum dried at 110-130℃ for 4-8 hours to obtain an Al-ON nanoscale bonding transition layer in situ on the substrate surface.

[0047] (III) Beneficial Effects

[0048] Compared with the prior art, the present invention provides a high thermal conductivity, low expansion modified electronic ceramic substrate and its preparation method, which has the following beneficial effects:

[0049] 1. This invention relates to a high thermal conductivity, low expansion modified electronic ceramic substrate and its preparation method. The invention uses a composite of hydroxylated modified AlN and coupled modified Al2O3 as the main crystalline phase, which not only retains the intrinsic high thermal conductivity of AlN, but also significantly reduces the raw material cost and sintering difficulty through Al2O3. At the same time, through hydrothermal hydroxylation modification, a dense hydroxyl protective layer is constructed on the surface of AlN powder, which completely solves the industry pain point of easy hydrolysis of AlN powder, improves the storage stability of powder by more than 10 times, and greatly improves the batch consistency of substrate performance.

[0050] 2. This invention relates to a high thermal conductivity and low expansion modified electronic ceramic substrate and its preparation method. Through a dual-phase synergistic control system of negative thermal expansion and low expansion, using nano-tungsten zirconate negative thermal expansion powder and pre-calcined cordierite low expansion powder, the thermal expansion coefficient of the substrate can be precisely controlled within a wide temperature range of 25-300℃, achieving perfect matching with Si and GaN semiconductor chips and reducing device operating thermal stress by more than 60%. Simultaneously, the dual-phase control phase forms a good interfacial bond with the substrate, avoiding the precipitous drop in thermal conductivity caused by adding a single low expansion phase, truly achieving a balance between high thermal conductivity and low expansion.

[0051] 3. This invention relates to a high thermal conductivity and low expansion modified electronic ceramic substrate and its preparation method. The invention uses hydroxylated modified boron nitride nanosheets and few-layer graphene as thermal conductivity enhancement phases. The two are uniformly dispersed in the matrix through surface modification, constructing an interpenetrating three-dimensional thermally conductive network, which significantly reduces phonon scattering. The thermal conductivity of the substrate can reach up to 250 W / m·K. At the same time, the two-dimensional nanomaterials can pin grain boundaries and inhibit abnormal grain growth in the matrix. The bending strength of the substrate can reach up to 450 MPa, and the fracture toughness is improved by more than 40%, thus balancing thermal conductivity and mechanical reliability.

[0052] 4. This invention relates to a high thermal conductivity, low expansion modified electronic ceramic substrate and its preparation method. The invention employs a Y2O3-CaO-MgO ternary composite sintering aid, which can form a low-melting-point eutectic phase with oxide impurities on the surface of the matrix powder. This reduces the sintering temperature from the traditional 1850℃ to 1650-1750℃, enabling sintering under normal pressure nitrogen atmosphere. This eliminates the need for high-pressure sintering equipment, reducing energy consumption by more than 30% and significantly lowering production costs. Simultaneously, it purifies grain boundaries, reducing the scattering of phonons by the grain boundary glass and further improving the thermal conductivity of the substrate.

[0053] 5. This invention relates to a high thermal conductivity, low expansion modified electronic ceramic substrate and its preparation method. Through plasma activation and in-situ hydrothermal reaction, an Al-ON nanoscale bonding transition layer is grown in situ on the substrate surface. This transition layer and the ceramic substrate form a covalently bonded integral structure without interface defects, significantly improving the bonding force between the subsequent metallization layer and the substrate. The metallization bonding force is increased from the traditional 20 N / mm² to over 45 N / mm². Simultaneously, it optimizes the substrate surface roughness, significantly improving the reliability of the device during thermal cycling. After 1000 thermal cycles, there is no peeling or cracking at the interface, meeting the high reliability packaging requirements for automotive and military applications. Detailed Implementation

[0054] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0055] A modified electronic ceramic substrate with high thermal conductivity and low expansion includes a modified composite ceramic matrix and a nanoscale bonding transition layer grown in situ on both sides of the modified composite ceramic matrix.

[0056] The modified composite ceramic matrix comprises the following components by mass parts: 65-85 parts of main crystalline phase, 10-25 parts of low expansion regulating phase, 2-8 parts of nano-thermal conductive reinforcing phase, and 3-10 parts of composite sintering aid.

[0057] The main crystalline phase is a mixture of surface-hydroxylated modified aluminum nitride powder and surface-silane-coupled modified alumina powder in a mass ratio of 3-5:1.

[0058] The low expansion regulating phase is a mixture of negative thermal expansion tungsten zirconate powder and pre-calcined low expansion cordierite powder in a mass ratio of 1:2-4.

[0059] The nano-thermal conductive reinforcing phase is composed of hydroxylated modified boron nitride nanosheets and few-layer graphene in a mass ratio of 4-6:1.

[0060] In the main crystalline phase, the particle size D50 of the hydroxylated modified aluminum nitride powder is 1-2 μm. The hydroxylation modification is carried out by hydrothermal modification of anhydrous ethanol-deionized water mixed system, and the surface hydroxyl coverage is ≥85%.

[0061] The particle size D50 of the silane coupling modified alumina powder is 0.5-1μm. It is modified with KH550 or KH560 silane coupling agent, and the coating rate of the coupling agent is ≥90%.

[0062] In the low expansion control phase, the tungsten zirconate powder is a nano-sized powder with a particle size D50 of 100-300 nm;

[0063] The cordierite powder has a particle size D50 of 0.8-1.5μm. After pre-calcination in air at 1050-1150℃ for 2-3 hours, the purity of the cordierite phase is ≥98%.

[0064] In the nano-thermal conductive reinforcing phase, the hydroxylated modified boron nitride nanosheets have 3-8 layers and a sheet diameter of 0.5-3 μm;

[0065] The few-layer graphene has 1-5 layers and a sheet diameter of 1-4 μm. Both are hydroxylated and modified, with a surface hydroxyl content ≥2.5 mmol / g.

[0066] The composite sintering aid is a ternary system of Y2O3-CaO-MgO, with a mass ratio of 4-6:2-3:1-2, and a powder particle size D50 of 0.3-0.8μm.

[0067] The nanoscale bonding transition layer is an Al-ON covalent bonding composite transition layer with a thickness of 50-120 nm. The transition layer and the ceramic substrate are an in-situ integrated structure with an interfacial bonding strength of ≥50 MPa and a substrate surface roughness Ra≤0.2 μm.

[0068] A method for preparing a modified electronic ceramic substrate with high thermal conductivity and low expansion includes the following steps:

[0069] S1. Powder pretreatment: Surface modification of main crystalline phase powder, pre-sintering modification of low expansion control phase, dispersion modification of nano thermally conductive enhancement phase, and mixing and grinding of composite sintering aid are completed respectively.

[0070] The specific process for powder pretreatment in step S1 is as follows:

[0071] Main crystalline phase modification: Aluminum nitride powder is added to a mixed solution of anhydrous ethanol and deionized water in a volume ratio of 8-10:1, the pH is adjusted to 8.5-9.5, and the mixture is subjected to hydrothermal reaction at 75-85℃ for 3-5 hours. After filtration and washing, the mixture is vacuum dried at 120℃ for 10-14 hours to obtain hydroxylated modified aluminum nitride powder.

[0072] Alumina powder is added to anhydrous ethanol, and 1.5-2.5% of silane coupling agent by weight of the powder is added. The mixture is ultrasonically dispersed at 55-65℃ for 20-40 min, stirred and reacted for 1.5-2.5 h, filtered and dried to obtain coupling-modified alumina powder. The main crystalline phase powder is obtained by mixing according to the formula.

[0073] Low expansion control phase pretreatment: Tungsten zirconate powder and cordierite powder are mixed in proportion, pre-calcined in air at 1050-1150℃ for 2-3 hours, cooled in the furnace and then ball-milled to the target particle size to obtain low expansion control phase powder.

[0074] Modification of nano-thermal conductive reinforcing phase: Boron nitride nanosheets and few-layer graphene were added to deionized water in a certain ratio, and 0.8-1.2% sodium polyacrylate dispersant by weight of the powder was added. The mixture was ultrasonically exfoliated for 2-4 hours, filtered, and vacuum dried to obtain modified nano-thermal conductive reinforcing phase powder.

[0075] Pretreatment of sintering aid: Y2O3, CaO and MgO are mixed in proportion, ball-milled for 3-5 hours, and dried to obtain composite sintering aid powder;

[0076] S2. Mixing and slurry preparation: Add the pretreated powders to the solvent according to the ratio, add binder, plasticizer and dispersant, and obtain a uniform and stable ceramic slurry by planetary ball milling. After sieving, vacuum degassing is performed.

[0077] S3, Casting: The degassed ceramic slurry is cast using a casting process to obtain a ceramic green belt with uniform thickness;

[0078] S4. Debinding and pre-sintering: After the ceramic green body is cut, it is placed in a nitrogen atmosphere furnace and heated in stages to complete the debinding and pre-sintering, so as to obtain a pre-sintered green body without cracks or deformation.

[0079] S5. Atmospheric pressure sintering densification: The pre-sintered green body is placed in a high-purity nitrogen atmosphere and sintered at low temperature under atmospheric pressure to complete the densification treatment and obtain the ceramic substrate.

[0080] The specific process parameters for steps S2-S5 are as follows:

[0081] S2. Mixing and slurry preparation: Using anhydrous ethanol as solvent, add 4-6% PVB binder and 1.5-2.5% dibutyl phthalate plasticizer by weight of powder, and ball mill for 10-14 hours at a ball-to-powder ratio of 4-6:1 and a speed of 250-350 rpm to obtain a ceramic slurry with a solid content of 55-60%. Pass the slurry through a 200-300 mesh sieve and degas it under vacuum for 20-40 minutes.

[0082] S3. Casting: The doctor blade gap is 0.2-0.5mm, the casting speed is 0.5-1.0m / min, and the segmented drying temperature is 60℃, 80℃, 100℃, and 120℃ to obtain a ceramic green belt with uniform thickness.

[0083] S4. Debinding and pre-sintering: Under a nitrogen atmosphere, heat to 240-260℃ at a rate of 1.5-2.5℃ / min and hold for 1.5-2.5h;

[0084] Increase the temperature to 580-620℃ at a rate of 0.8-1.2℃ / min and hold for 3-5 hours;

[0085] Heat to 950-1050℃ at a rate of 2.5-3.5℃ / min, hold for 1.5-2.5 hours, and then cool with the furnace.

[0086] S5. Atmospheric pressure sintering densification: Under atmospheric pressure and high-purity nitrogen atmosphere, the temperature is increased to 1150-1250℃ at 4-6℃ / min and held for 0.5-1.5h.

[0087] Heat to 1650-1750℃ at a rate of 2.5-3.5℃ / min, hold for 4-8 hours, and then cool with the furnace.

[0088] S6. Surface in-situ modification: After polishing and cleaning the densified ceramic substrate, it is activated by plasma and subjected to in-situ hydrothermal reaction to grow a nanoscale bonding transition layer on the substrate surface, and finally obtains a modified electronic ceramic substrate with high thermal conductivity and low expansion.

[0089] The specific process of surface in-situ modification in step S6 is as follows: the densified ceramic substrate is polished to a mirror finish on both sides, ultrasonically cleaned with anhydrous ethanol for 10-20 minutes, dried and placed in a plasma reaction chamber, and activated with mixed plasma of argon-nitrogen volume ratio of 3-5:1 for 10-20 minutes, with a processing power of 150-250W.

[0090] The activated substrate was placed in a hydrothermal reactor, and a mixed solution of anhydrous ethanol and deionized water in a volume ratio of 1:1 was added. The pH was adjusted to 9.5-10.5, and the hydrothermal reaction was carried out at 130-150℃ for 2-4 hours. After removal, the substrate was rinsed with deionized water and vacuum dried at 110-130℃ for 4-8 hours to obtain an Al-ON nanoscale bonding transition layer in situ on the substrate surface.

[0091] Example 1:

[0092] The high thermal conductivity and low expansion modified electronic ceramic substrate provided in this embodiment has the following components by mass: 75 parts of main crystalline phase, 15 parts of low expansion regulating phase, 4 parts of nano-thermal conductivity reinforcing phase, and 6 parts of composite sintering aid.

[0093] The main crystalline phase is a mixture of hydroxylated modified AlN powder and KH550 modified Al2O3 powder in a mass ratio of 4:1.

[0094] AlN powder has a particle size D50 of 1.2 μm and a hydroxyl group coverage of 88%; Al2O3 powder has a particle size D50 of 0.8 μm and a coupling agent coating rate of 92%.

[0095] The low-expansion regulating phase is a mixture of ZrW2O8 powder and cordierite powder in a mass ratio of 1:3;

[0096] ZrW2O8 powder with a particle size D50 of 200 nm and cordierite powder with a particle size D50 of 1 μm, after pre-calcination at 1100 °C for 2 h, have a phase purity of 98.5%.

[0097] The nano-thermal conductive reinforcing phase is a mixture of hydroxylated BNNS and few-layer graphene in a mass ratio of 5:1; the BNNS has 3-5 layers and a sheet diameter of 0.5-2 μm; the few-layer graphene has 1-3 layers and a sheet diameter of 1-3 μm, with a surface hydroxyl content of 2.8 mmol / g.

[0098] The composite sintering aid is a compound of Y2O3-CaO-MgO in a mass ratio of 5:3:2, with a particle size D50=0.5μm.

[0099] An Al-ON bonded transition layer with a thickness of 80 nm was grown in situ on the surface.

[0100] The preparation method of this embodiment includes the following steps:

[0101] S1. Powder pretreatment: The main crystalline phase modification, low expansion control phase pre-calcination, nano thermal conductivity enhancement phase modification, and composite sintering aid mixing and grinding are completed according to the above proportions. For details of the process, please refer to claim 8.

[0102] S2. Mixing and slurry preparation: Using anhydrous ethanol as solvent, add 5% PVB binder and 2% dibutyl phthalate plasticizer by weight of powder, and ball mill for 12 hours at a ball-to-material ratio of 5:1 and a rotation speed of 300 rpm to obtain a ceramic slurry with a solid content of 58%. Pass it through a 200-mesh sieve and degas it under vacuum for 30 minutes.

[0103] S3. Casting: The doctor blade gap is 0.3mm, the casting speed is 0.8m / min, and the segmented drying temperatures are 60℃, 80℃, 100℃, and 120℃ to obtain a ceramic green body with uniform thickness.

[0104] S4. Debinding and pre-sintering: Under nitrogen atmosphere, heat to 250℃ at 2℃ / min and hold for 2h; heat to 600℃ at 1℃ / min and hold for 4h; heat to 1000℃ at 3℃ / min and hold for 2h, then cool with the furnace.

[0105] S5. Atmospheric pressure sintering densification: Under atmospheric pressure and high-purity nitrogen atmosphere, the temperature is increased to 1200℃ at 5℃ / min and held for 1h; then increased to 1700℃ at 3℃ / min and held for 6h, and cooled with the furnace to obtain a densified ceramic substrate.

[0106] S6. Surface in-situ modification: The substrate is polished to a mirror finish on both sides, ultrasonically cleaned, and then activated for 15 min with a mixed plasma of argon-nitrogen gas volume ratio of 4:1 at a power of 200W. Subsequently, it is hydrothermally reacted at 140℃ for 3 h and vacuum dried at 120℃ for 6 h to obtain the target substrate.

[0107] Example 2:

[0108] The difference between this embodiment and Embodiment 1 is that the modified composite ceramic matrix composition is: 80 parts of main crystalline phase, 12 parts of low expansion regulating phase, 5 parts of nano thermally conductive reinforcing phase, and 3 parts of composite sintering aid.

[0109] The mass ratio of the main crystalline phase AlN to Al2O3 is 5:1;

[0110] The mass ratio of the low-expansion-controlled phase ZrW2O8 to cordierite was 1:2;

[0111] Sintering temperature 1720℃, holding time 5h;

[0112] The remaining components and process steps are completely consistent with those in Example 1.

[0113] Example 3:

[0114] The difference between this embodiment and Embodiment 1 is that the modified composite ceramic matrix composition is: 70 parts of main crystalline phase, 18 parts of low expansion regulating phase, 3 parts of nano thermally conductive reinforcing phase, and 9 parts of composite sintering aid.

[0115] The mass ratio of the main crystalline phase AlN to Al2O3 is 3:1;

[0116] The mass ratio of the low-expansion-controlled phase ZrW2O8 to cordierite is 1:4;

[0117] Sintering temperature 1680℃, holding time 8h;

[0118] The remaining components and process steps are completely consistent with those in Example 1.

[0119] Comparative Example 1:

[0120] This comparative example uses a traditional pure AlN ceramic substrate, with the following components: 95 parts of pure AlN powder and 5 parts of Y2O3 sintering aid.

[0121] Prepared using traditional processes, without surface modification, low expansion control phase, nano-thermal conductive enhancement phase, or surface bonding transition layer, sintered at 1850℃ and held for 6 hours.

[0122] Performance testing:

[0123] The performance of the samples from Examples 1-3 and Comparative Example 1 was tested, and the test results are shown in the table below:

[0124] The test results show that the substrate prepared by the embodiments of the present invention is significantly superior to the traditional pure AlN substrate in terms of thermal conductivity, mechanical properties, metallization bonding force, thermal expansion matching, and thermal cycling reliability. At the same time, the sintering temperature is greatly reduced and the preparation cost is significantly reduced. It perfectly solves the core pain points of the prior art and has extremely high application value.

[0125] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A modified electronic ceramic substrate with high thermal conductivity and low expansion, characterized in that: It includes a modified composite ceramic matrix and a nanoscale bonding transition layer grown in situ on both sides of the modified composite ceramic matrix; The modified composite ceramic matrix comprises the following components by mass: 65-85 parts of main crystalline phase, 10-25 parts of low expansion regulating phase, 2-8 parts of nano-thermal conductive reinforcing phase, and 3-10 parts of composite sintering aid. The main crystalline phase is a mixture of surface-hydroxylated modified aluminum nitride powder and surface-silane-coupled modified alumina powder in a mass ratio of 3-5:

1. The low-expansion regulating phase is a mixture of negative thermal expansion tungsten zirconate powder and pre-calcined low-expansion cordierite powder in a mass ratio of 1:2-4. The nano-thermal conductive reinforcing phase is composed of hydroxylated modified boron nitride nanosheets and few-layer graphene in a mass ratio of 4-6:

1.

2. The high thermal conductivity, low expansion modified electronic ceramic substrate according to claim 1, characterized in that: In the main crystalline phase, the particle size D50 of the hydroxylated modified aluminum nitride powder is 1-2 μm, the hydroxylation modification is a hydrothermal modification of anhydrous ethanol-deionized water mixed system, and the surface hydroxyl coverage is ≥85%; The particle size D50 of the silane coupling modified alumina powder is 0.5-1μm. It is modified with KH550 or KH560 silane coupling agent, and the coating rate of the coupling agent is ≥90%.

3. The high thermal conductivity, low expansion modified electronic ceramic substrate according to claim 1, characterized in that: In the low-expansion control phase, the tungsten zirconate powder is a nano-sized powder with a particle size D50 of 100-300 nm; The cordierite powder has a particle size D50 of 0.8-1.5μm. After pre-calcination in air at 1050-1150℃ for 2-3 hours, the purity of the cordierite phase is ≥98%.

4. The high thermal conductivity, low expansion modified electronic ceramic substrate according to claim 1, characterized in that: In the aforementioned nano-thermal conductive enhancement phase, the hydroxylated modified boron nitride nanosheets have 3-8 layers and a sheet diameter of 0.5-3 μm; The few-layer graphene has 1-5 layers and a sheet diameter of 1-4 μm. Both are hydroxylated and modified, with a surface hydroxyl content ≥2.5 mmol / g.

5. The high thermal conductivity, low expansion modified electronic ceramic substrate according to claim 1, characterized in that: The composite sintering aid is a Y2O3-CaO-MgO ternary system with a mass ratio of 4-6:2-3:1-2 and a powder particle size D50 of 0.3-0.8 μm.

6. The high thermal conductivity, low expansion modified electronic ceramic substrate according to claim 1, characterized in that: The nanoscale bonding transition layer is an Al-ON covalent bonding composite transition layer with a thickness of 50-120 nm. The transition layer and the ceramic substrate are an in-situ integrated structure with an interfacial bonding strength of ≥50 MPa and a substrate surface roughness Ra≤0.2 μm.

7. A method for preparing a high thermal conductivity, low expansion modified electronic ceramic substrate according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Powder pretreatment: Surface modification of main crystalline phase powder, pre-sintering modification of low expansion control phase, dispersion modification of nano thermally conductive enhancement phase, and mixing and grinding of composite sintering aid are completed respectively. S2. Mixing and slurry preparation: Add the pretreated powders to the solvent according to the ratio, add binder, plasticizer and dispersant, and obtain a uniform and stable ceramic slurry by planetary ball milling. After sieving, vacuum degassing is performed. S3, Casting: The degassed ceramic slurry is cast using a casting process to obtain a ceramic green belt with uniform thickness; S4. Debinding and pre-sintering: After the ceramic green body is cut, it is placed in a nitrogen atmosphere furnace and heated in stages to complete the debinding and pre-sintering, so as to obtain a pre-sintered green body without cracks or deformation. S5. Atmospheric pressure sintering densification: The pre-sintered green body is placed in a high-purity nitrogen atmosphere and sintered at low temperature under atmospheric pressure to complete the densification treatment and obtain the ceramic substrate. S6. Surface in-situ modification: After polishing and cleaning the densified ceramic substrate, it is activated by plasma and subjected to in-situ hydrothermal reaction to grow a nanoscale bonding transition layer on the substrate surface, ultimately obtaining a modified electronic ceramic substrate with high thermal conductivity and low expansion.

8. The method for preparing a high thermal conductivity, low expansion modified electronic ceramic substrate according to claim 7, characterized in that: The specific process for powder pretreatment in step S1 is as follows: Main crystalline phase modification: Aluminum nitride powder is added to a mixed solution of anhydrous ethanol and deionized water in a volume ratio of 8-10:1, the pH is adjusted to 8.5-9.5, and the mixture is subjected to hydrothermal reaction at 75-85℃ for 3-5 hours. After filtration and washing, the mixture is vacuum dried at 120℃ for 10-14 hours to obtain hydroxylated modified aluminum nitride powder. Alumina powder is added to anhydrous ethanol, and 1.5-2.5% of silane coupling agent by weight of the powder is added. The mixture is ultrasonically dispersed at 55-65℃ for 20-40 min, stirred and reacted for 1.5-2.5 h, filtered and dried to obtain coupling-modified alumina powder. The main crystalline phase powder is obtained by mixing according to the formula. Low expansion control phase pretreatment: Tungsten zirconate powder and cordierite powder are mixed in proportion, pre-calcined in air at 1050-1150℃ for 2-3 hours, cooled in the furnace and then ball-milled to the target particle size to obtain low expansion control phase powder. Modification of nano-thermal conductive reinforcing phase: Boron nitride nanosheets and few-layer graphene were added to deionized water in a certain ratio, and 0.8-1.2% sodium polyacrylate dispersant by weight of the powder was added. The mixture was ultrasonically exfoliated for 2-4 hours, filtered, and vacuum dried to obtain modified nano-thermal conductive reinforcing phase powder. Pretreatment of sintering aid: Y2O3, CaO and MgO are mixed in proportion, ball-milled for 3-5 hours, and dried to obtain composite sintering aid powder.

9. The method for preparing a high thermal conductivity, low expansion modified electronic ceramic substrate according to claim 7, characterized in that: The specific process parameters for steps S2-S5 are as follows: S2 Mixing and Slurry Preparation: Using anhydrous ethanol as solvent, add 4-6% PVB binder and 1.5-2.5% dibutyl phthalate plasticizer by weight of powder, and ball mill for 10-14 hours at a ball-to-powder ratio of 4-6:1 and a rotation speed of 250-350 rpm to obtain a ceramic slurry with a solid content of 55-60%. Pass the slurry through a 200-300 mesh sieve and degas it under vacuum for 20-40 minutes. S3 casting: scraper gap 0.2-0.5mm, casting speed 0.5-1.0m / min, segmented drying temperature 60℃, 80℃, 100℃, 120℃, to obtain a ceramic green body with uniform thickness; S4 pre-sintering with debinding: Under a nitrogen atmosphere, heat to 240-260℃ at a rate of 1.5-2.5℃ / min and hold for 1.5-2.5h; Increase the temperature to 580-620℃ at a rate of 0.8-1.2℃ / min and hold for 3-5 hours; Heat to 950-1050℃ at a rate of 2.5-3.5℃ / min, hold for 1.5-2.5 hours, and then cool with the furnace. S5 Atmospheric Pressure Sintering Densification: Under atmospheric pressure and high-purity nitrogen atmosphere, the temperature is increased to 1150-1250℃ at 4-6℃ / min and held for 0.5-1.5h; Heat to 1650-1750℃ at a rate of 2.5-3.5℃ / min, hold for 4-8 hours, and then cool with the furnace.

10. The method for preparing a high thermal conductivity, low expansion modified electronic ceramic substrate according to claim 7, characterized in that: The specific process of surface in-situ modification in step S6 is as follows: the densified ceramic substrate is polished to a mirror finish on both sides, ultrasonically cleaned with anhydrous ethanol for 10-20 minutes, dried, and then placed in a plasma reaction chamber. It is activated by mixed plasma with an argon-nitrogen volume ratio of 3-5:1 for 10-20 minutes with a processing power of 150-250W. The activated substrate was placed in a hydrothermal reactor, and a mixed solution of anhydrous ethanol and deionized water in a volume ratio of 1:1 was added. The pH was adjusted to 9.5-10.5, and the hydrothermal reaction was carried out at 130-150℃ for 2-4 hours. After removal, the substrate was rinsed with deionized water and vacuum dried at 110-130℃ for 4-8 hours to obtain an Al-ON nanoscale bonding transition layer in situ on the substrate surface.

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