An electronic paste for beryllium oxide substrate and a method for preparing the same

Abstract

The application belongs to the technical field of electronic paste, and discloses an electronic paste for beryllium oxide matrix and a preparation method thereof. The electronic paste is composed of 60-75% metal functional phase, 10-20% glass phase, 2-5% binder, 10-20% solvent and 0.7-2% additive in terms of mass percentage. The sintering temperature of the electronic paste is 1650 DEG C, which is slightly lower than the sintering temperature of the BeO ceramic substrate (greater than or equal to 1900 DEG C), so that the forming state of the substrate cannot be changed, and a chemical bonding transition phase can be formed with the substrate to significantly improve the interface bonding strength. The difference between the thermal expansion coefficients of the functional layer prepared by the electronic paste and the BeO matrix is less than 2.5 ppm / K, so that the interface thermal stress can be reduced, the thermal cycle number can be significantly improved, and the anti-cracking ability is strong.

Description

Technical Field

[0001] This invention belongs to the field of electronic paste technology, and relates to an electronic paste for beryllium oxide matrix and its preparation method. Background Technology

[0002] Beryllium oxide (BeO) has a hexagonal wurtzite crystal structure (α-type). Beryllium oxide (BeO) has a covalent bond energy of 1059 kJ / mol and high covalent bond strength, endowing it with excellent thermal and chemical stability. Simultaneously, beryllium oxide possesses excellent thermal and electrical properties. Its room temperature thermal conductivity is 260–310 W / (m·K), with heat dissipation capacity far superior to alumina ceramics, and its thermal conductivity efficiency is close to that of metallic aluminum, exhibiting good thermal matching. In terms of electrical properties, beryllium oxide has a dielectric constant of 6.5–7.5 at 1 MHz and a volume resistivity ≥10⁻⁶. 14 With a breakdown strength of 30~40kV / mm and an Ω·cm, beryllium oxide exhibits excellent insulation properties and high voltage resistance, making it well-suited for high-frequency and high-voltage applications. Based on this, high-purity beryllium oxide ceramic substrates have become the core matrix material for high thermal conductivity, high insulation, and high-temperature resistant electronic devices, and are widely used in high-power microwave / RF devices, laser tubes, power modules, traveling wave tube power windows, spaceborne and aerospace electronic devices, nuclear reactor reflectors, and other fields.

[0003] Existing conventional electronic pastes, such as silver-palladium (Ag-Pd) paste and silver-copper (Ag-Cu) paste, have an optimal sintering temperature range of 850~950℃, which is incompatible with the high thermal conductivity of beryllium oxide ceramic substrates. The metallization layer has slow thermal conductivity, and heat accumulates at the interface, leading to localized overheating (≥300℃) and pad detachment. At the same time, the low-temperature sintering process means that the metallization layer formed by sintering is only physically adhered to the beryllium oxide ceramic substrate, resulting in high porosity, low density, and insufficient adhesion strength to the substrate. It is impossible to form a strong and dense conductive metal layer, which is difficult to meet the requirements of high-end devices.

[0004] Currently, the solution to this problem involves adding beryllium oxide powder as an inorganic additive to tungsten-based electronic pastes. This enables vacuum sealing between the tungsten paste and the beryllium oxide ceramic substrate, improving their sintering compatibility. However, beryllium oxide powder is a highly toxic material. During the entire process of electronic paste preparation, mixing, sintering, and subsequent processing, beryllium oxide dust and vapor are easily generated. Inhalation of this dust can cause pulmonary granulomatosis and even induce chronic beryllium disease (CBD). Furthermore, beryllium oxide is clearly classified as a Group 1 carcinogen, posing occupational health risks and environmental hazards when using beryllium oxide powder as a raw material. Therefore, providing an electronic paste with a sintering temperature that matches the beryllium oxide matrix and does not require the addition of highly toxic beryllium oxide powder is of great significance. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides an electronic paste for a beryllium oxide matrix and its preparation method. By mass percentage, the electronic paste comprises 60-75% metallic functional phase, 10-20% glassy phase, 2-5% binder, 10-20% solvent, and 0.7-2% additives. The sintering temperature of the electronic paste is 1650℃, slightly lower than the ≥1900℃ of the BeO ceramic substrate, which does not alter the substrate's forming state and allows it to form a chemically bonded transition phase with the substrate, significantly improving interfacial bonding strength. The functional layer prepared by the electronic paste of this invention has a CTE difference of less than 2.5 ppm / K with the BeO matrix, reducing interfacial thermal stress, significantly increasing the number of thermal cycles, and exhibiting strong crack resistance.

[0006] On one hand, the present invention provides an electronic paste for a beryllium oxide matrix, wherein the electronic paste comprises, by mass percentage, 60-75% metallic functional phase, 10-20% glass phase, 2-5% binder, 10-20% solvent, and 0.7-2% additives.

[0007] Furthermore, by mass percentage, the metallic functional phase consists of 50-60% tungsten powder and 10-15% molybdenum powder, and the tungsten powder has a D... 90 The density of molybdenum powder is 5~10μm. 90 The particle size is 5~10μm, and the purity of both tungsten powder and molybdenum powder is ≥99.9%.

[0008] Further, by mass percentage, the glass phase consists of 2-4% magnesium oxide, 3-5% aluminum oxide, 2-4% silicon dioxide, 1-3% aluminum nitride ceramic, and 2-5% samarium oxide; the binder is one of ethyl cellulose and polyamide; the solvent is at least one of terpineol and isooctanol; the additives consist of 0.5-1.5% dispersant and 0.2-0.5% rheology modifier, wherein the dispersant is one of BYK-163, sodium polyacrylate, and sodium hexametaphosphate, and the rheology modifier is castor oil.

[0009] On the other hand, the present invention claims protection for the method for preparing the above-mentioned electronic paste for a beryllium oxide matrix, which specifically includes the following steps:

[0010] S1: Raw material pretreatment: Tungsten powder and molybdenum powder are placed in a hydrogen atmosphere furnace and reduced at 1050~1100℃ for 1~1.5h to remove the oxide layer on the surface of the powder. After cooling to room temperature in the furnace, they are taken out for later use. Magnesium oxide, aluminum oxide, silicon dioxide, aluminum nitride and samarium oxide are weighed according to the formula and ball-milled at 200~250r / min for 4~6h to obtain the glass phase.

[0011] S2: Preparation of organic carrier: Weigh the binder, solvent and additives according to the ratio. Add the additives to the solvent first, and stir for 20 to 30 minutes at room temperature and stirring speed of 300 to 500 r / min until the additives are completely dissolved in the solvent. Then add the binder, heat to 60 to 70℃, maintain stirring speed of 500 to 800 r / min, and stir at a constant temperature for 1 to 2 hours until the binder is completely dissolved. A uniform, transparent organic carrier without particle agglomeration is obtained. Let it cool naturally to room temperature for later use.

[0012] S3: Mixing and Grinding. The pretreated metallic functional phase powder and glass phase powder are added to the organic carrier prepared in S2 according to the specified ratio. The mixture is stirred for 30-40 minutes at room temperature and a stirring speed of 600-800 r / min to obtain a preliminary mixed slurry. This slurry is then transferred to a three-roll mill for grinding. The roller spacing is adjusted to 5-10 μm, the grinding speed is 200-300 r / min, and the grinding is performed 3-5 times until the slurry has a fineness ≤15 μm and a viscosity of 25-35 Pa. s, to obtain a uniform, fine electronic paste initial product without obvious particle agglomeration.

[0013] S4: Degassing and Curing. The initial slurry after S3 grinding is transferred to a vacuum degassing machine and degassed for 15-20 minutes at a vacuum of -0.08 to -0.1 MPa and room temperature to remove air bubbles. The slurry is then sealed and cured at room temperature for 12-24 hours to ensure that all components are fully wetted and evenly dispersed, resulting in the finished electronic slurry.

[0014] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0015] (1) The sintering temperature of the electronic paste of the present invention is 1650℃, which is slightly lower than the ≥1900℃ of the BeO ceramic substrate. This temperature does not change the forming state of the substrate and can form a chemically bonded transition phase with the substrate, significantly improving the interfacial bonding strength. The electronic paste of the present invention contains MgO, silicon dioxide, aluminum nitride and samarium oxide. MgO, silicon dioxide and samarium oxide are the core components that form a chemically bonded anchoring phase with the BeO matrix. Based on the ratio range provided by the present invention, the interfacial bonding strength that can be formed is >12MPa. AlN, as a thermal conductivity enhancing phase, synergistically forms a transition phase with MgO-Al2O3-SiO2, improving the interfacial bonding strength to >13.5MPa. Magnesium oxide undergoes an interfacial solid-phase reaction with the BeO matrix to generate MgO. A eutectic transition phase, BeO (magnesium beryllium oxide), provides a chemically bonded phase that firmly anchors the glassy phase to the BeO ceramic surface. Silica reacts with the BeO matrix to form a continuous transition layer, Be₂SiO₄ (barium beryllium silicate), which then interacts with MgO. BeO forms a double-layer anchoring structure, significantly improving the bonding strength between the metallization layer and the BeO matrix; samarium oxide undergoes an interfacial reaction with the BeO matrix to generate Sm2O3. BeO rare earth beryllium salt transition phase, and MgO BeO and Be2SiO4 form a three-layer chemically bonded anchoring structure, significantly improving the interfacial bonding strength. Samarium oxide can also promote solid-phase diffusion, making the bonding between the W-Mo metallic phase and the glass phase tighter, inhibiting abnormal growth of W-Mo grains, suppressing high-temperature oxidation and decomposition of AlN, reducing nitrogen bubble generation, and lowering the porosity of the metal layer.

[0016] (2) The functional layer prepared by the electronic paste of the present invention has superior electrical and thermal properties, and its volume resistivity is ≥10. 14 Ω cm (glass phase insulation region), breakdown strength ≥32 kV / mm, thermal conductivity 168~175 W / (m²) K), capable of reacting with the BeO matrix at 260~310 W / (m K) Gradient matching is achieved, allowing for rapid heat conduction from the device → functional layer → BeO substrate without heat buildup. The electronic paste of this invention has a coefficient of thermal expansion matching the BeO matrix. The CTE of the electronic paste prepared within the formulation range provided in this invention is 5.1~5.4 ppm / K, with a difference of less than 2.5 ppm / K from the 7.5 ppm / K CTE of the BeO matrix. This reduces interfacial thermal stress, significantly increases the number of thermal cycles to over 700, and enhances crack resistance. The functional layer prepared with the electronic paste of this invention also has a low porosity (≤2.5%). After 700 thermal cycles, there are no macroscopic cracks, bulges, or edge warping, and the attenuation rate is ≤3.2%, far below the industry standard for superior products. The metallic phase of this invention consists of tungsten powder and molybdenum powder. Molybdenum has excellent corrosion resistance in a high-temperature reducing atmosphere and can form a stable W-Mo alloy phase with tungsten, ensuring continuous conductive pathways. It can also undergo weak interfacial reactions with components in the glass phase, enhancing the metal-glass bonding force. Detailed Implementation

[0017] The technical solution of the present invention will be described below with reference to embodiments. However, the present invention is not limited to the following embodiments. Unless otherwise specified, the experimental methods and detection methods described in each embodiment are conventional methods; unless otherwise specified, the reagents and materials can be purchased commercially. Unless otherwise specified, the percentages in the following embodiments refer to mass percentages.

[0018] The purity of both tungsten powder and molybdenum powder is ≥99.9%.

[0019] The purity of magnesium oxide, aluminum oxide, silicon dioxide, aluminum nitride, and samarium oxide is ≥99.5%.90 All are ≤2μm.

[0020] Example 1

[0021] This embodiment provides a method for preparing an electronic paste for a beryllium oxide matrix, specifically including the following steps:

[0022] By mass percentage, the electronic paste of this embodiment consists of 60% metallic functional phase, 20% glass phase, 5% binder, 14.3% solvent, and 0.7% additives. The metallic functional phase consists of 50% tungsten powder and 10% molybdenum powder. The glass phase consists of 4% magnesium oxide, 5% aluminum oxide, 4% silicon dioxide, 2% aluminum nitride, and 5% samarium oxide. The additives consist of 0.5% BYK-163 and 0.2% castor oil.

[0023] S1: Raw material pretreatment, tungsten powder (D 90 (8μm) and molybdenum powder (D 90 The powder (5 μm) was placed in a hydrogen atmosphere furnace and cooled to room temperature with the furnace. It was then removed and reduced at 1050℃ for 1.5 h to remove the oxide layer on the surface of the powder. The powder was then set aside. Magnesium oxide, aluminum oxide, silicon dioxide, aluminum nitride, and samarium oxide were weighed according to the formula and ball-milled at 200 r / min for 5 h to obtain a 20% glass phase.

[0024] S2: Preparation of organic carrier: Weigh the binder (polyamide), solvent (terpineol) and additives according to the formula. Add the additives to the solvent first, and stir for 30 minutes at room temperature and stirring speed of 300 r / min until the additives are completely dissolved in the solvent. Then add the binder, heat to 70℃, maintain stirring speed of 800 r / min, and stir at a constant temperature for 2 hours until the binder is completely dissolved. A uniform, transparent organic carrier without particle agglomeration is obtained. After naturally cooling to room temperature, it is ready for use.

[0025] S3: Mixing and Grinding. The pretreated metallic functional phase powder and glass phase powder are added to the organic carrier prepared in S2 according to the specified ratio. The mixture is stirred for 40 minutes at room temperature and a stirring speed of 600 r / min to obtain a preliminary mixed slurry. This slurry is then transferred to a three-roll mill for grinding. The roller spacing is adjusted to 8 μm, the grinding speed is 200 r / min, and the grinding is performed 3-5 times until the slurry fineness is ≤15 μm and the viscosity is 25-35 Pa. s, to obtain a uniform, fine electronic paste initial product without obvious particle agglomeration.

[0026] S4: Degassing and maturation. The initial slurry after S3 grinding is transferred to a vacuum degassing machine and degassed for 20 minutes at a vacuum of -0.08 MPa and room temperature to remove air bubbles from the slurry. The slurry is then sealed and maturated at room temperature for 12 hours to ensure that all components are fully wetted and evenly dispersed, resulting in the finished electronic slurry.

[0027] Example 2

[0028] This embodiment provides a method for preparing an electronic paste for a beryllium oxide matrix, specifically including the following steps:

[0029] By mass percentage, the electronic paste of this embodiment consists of 70% metallic functional phase, 11% glass phase, 2% binder, 15% solvent, and 2% additives. The metallic functional phase consists of 58% tungsten powder and 12% molybdenum powder. The glass phase consists of 2% magnesium oxide, 3% aluminum oxide, 2% silicon dioxide, 1% aluminum nitride, and 3% samarium oxide. The additives consist of 1.5% sodium polyacrylate and 0.5% castor oil.

[0030] S1: Raw material pretreatment, tungsten powder (D 90 (5μm) and molybdenum powder (D) 90 The powder (5 μm) was placed in a hydrogen atmosphere furnace and reduced at 1100℃ for 1.5 h to remove the oxide layer on the surface of the powder. After cooling to room temperature with the furnace, it was taken out and set aside. Magnesium oxide, aluminum oxide, silicon dioxide, aluminum nitride and samarium oxide were weighed according to the formula and ball-milled at 200 r / min for 4 h to obtain 11% glass phase.

[0031] S2: Preparation of organic carrier: Weigh the binder (ethyl cellulose), solvent (10% terpineol + 5% isooctyl alcohol) and additives according to the formula. First, add the additives to the solvent and stir for 30 minutes at room temperature and a stirring speed of 500 r / min until the additives are completely dissolved in the solvent. Then add the binder, heat to 65℃, maintain the stirring speed of 500 r / min, and stir at a constant temperature for 2 hours until the binder is completely dissolved. A uniform, transparent organic carrier without particle agglomeration is obtained. After naturally cooling to room temperature, it is ready for use.

[0032] S3: Mixing and Grinding. The pretreated metallic functional phase powder and glass phase powder are added to the organic carrier prepared in S2 according to the specified ratio. The mixture is stirred for 40 minutes at room temperature and a stirring speed of 800 r / min to obtain a preliminary mixed slurry. This slurry is then transferred to a three-roll mill for grinding. The roller spacing is adjusted to 5 μm, the grinding speed is 200 r / min, and the grinding is performed 3-5 times until the slurry fineness is ≤15 μm and the viscosity is 25-35 Pa. s, to obtain a uniform, fine electronic paste initial product without obvious particle agglomeration.

[0033] S4: Degassing and maturation. The initial slurry after S3 grinding is transferred to a vacuum degassing machine and degassed for 15 minutes at a vacuum of -0.10 MPa and room temperature to remove air bubbles from the slurry. The slurry is then sealed and maturated at room temperature for 24 hours to ensure that all components are fully wetted and evenly dispersed, resulting in the finished electronic slurry.

[0034] Example 3

[0035] This embodiment provides a method for preparing an electronic paste for a beryllium oxide matrix, specifically including the following steps:

[0036] By mass percentage, the electronic paste of this embodiment consists of 75% metallic functional phase, 10% glass phase, 3% binder, 10% solvent, and 2% additives. The metallic functional phase consists of 60% tungsten powder and 15% molybdenum powder. The glass phase consists of 2% magnesium oxide, 3% aluminum oxide, 2% silicon dioxide, 1% aluminum nitride, and 2% samarium oxide. The additives consist of 1.5% BYK-163 and 0.5% castor oil.

[0037] S1: Raw material pretreatment, tungsten powder (D 90 (5μm) and molybdenum powder (D) 90 The powder (8μm) was placed in a hydrogen atmosphere furnace and reduced at 1100℃ for 1.5h to remove the oxide layer on the surface of the powder. After cooling to room temperature with the furnace, it was taken out and set aside. Magnesium oxide, aluminum oxide, silicon dioxide, aluminum nitride and samarium oxide were weighed according to the formula and ball-milled at 200r / min for 4h to obtain 10% glass phase.

[0038] S2: Preparation of organic carrier: Weigh the binder (ethyl cellulose), solvent (isooctanol) and additives according to the formula. Add the additives to the solvent first, and stir for 30 minutes at room temperature and stirring speed of 500 r / min until the additives are completely dissolved in the solvent. Then add the binder, heat to 70℃, maintain stirring speed of 500 r / min, and stir at a constant temperature for 2 hours until the binder is completely dissolved. A uniform, transparent organic carrier without particle agglomeration is obtained. After naturally cooling to room temperature, it is ready for use.

[0039] S3: Mixing and Grinding. The pretreated metallic functional phase powder and glass phase powder are added to the organic carrier prepared in S2 according to the specified ratio. The mixture is stirred for 40 minutes at room temperature and a stirring speed of 800 r / min to obtain a preliminary mixed slurry. This slurry is then transferred to a three-roll mill for grinding. The roller spacing is adjusted to 5 μm, the grinding speed is 200 r / min, and the grinding is performed 3-5 times until the slurry fineness is ≤15 μm and the viscosity is 25-35 Pa. s, to obtain a uniform, fine electronic paste initial product without obvious particle agglomeration.

[0040] S4: Degassing and maturation. The initial slurry after S3 grinding is transferred to a vacuum degassing machine and degassed for 15 minutes at a vacuum of -0.10 MPa and room temperature to remove air bubbles from the slurry. The slurry is then sealed and maturated at room temperature for 24 hours to ensure that all components are fully wetted and evenly dispersed, resulting in the finished electronic slurry.

[0041] Example 4

[0042] This embodiment provides a method for preparing an electronic paste for a beryllium oxide matrix, specifically including the following steps:

[0043] By mass percentage, the electronic paste of this embodiment consists of 62% metallic functional phase, 15% glass phase, 2% binder, 20% solvent, and 1% additives. The metallic functional phase consists of 50% tungsten powder and 12% molybdenum powder. The glass phase consists of 3% magnesium oxide, 4% aluminum oxide, 3% silicon dioxide, 3% aluminum nitride, and 2% samarium oxide. The additives consist of 0.5% sodium hexametaphosphate and 0.5% castor oil.

[0044] S1: Raw material pretreatment, tungsten powder (D 90 (10μm) and molybdenum powder (D) 90 The powder (10 μm) was placed in a hydrogen atmosphere furnace and reduced at 1050℃ for 1.5 h to remove the oxide layer on the surface of the powder. After cooling to room temperature with the furnace, it was taken out and set aside. Magnesium oxide, aluminum oxide, silicon dioxide, aluminum nitride and samarium oxide were weighed according to the formula and ball-milled at 200 r / min for 5 h to obtain 15% glass phase.

[0045] S2: Preparation of organic carrier: Weigh the binder (polyamide), solvent (15% terpineol + 5% isooctyl alcohol) and additives according to the formula. First, add the additives to the solvent and stir for 30 minutes at room temperature and a stirring speed of 300 r / min until the additives are completely dissolved in the solvent. Then add the binder, heat to 60℃, maintain a stirring speed of 500 r / min, and stir at a constant temperature for 1 hour until the binder is completely dissolved. A uniform, transparent organic carrier without particle agglomeration is obtained. After naturally cooling to room temperature, it is ready for use.

[0046] S3: Mixing and Grinding. The pretreated metallic functional phase powder and glass phase powder are added to the organic carrier prepared in S2 according to the specified ratio. The mixture is stirred for 40 minutes at room temperature and a stirring speed of 700 r / min to obtain a preliminary mixed slurry. This slurry is then transferred to a three-roll mill for grinding. The roller spacing is adjusted to 10 μm, the grinding speed is 300 r / min, and the grinding is performed 3-5 times until the slurry fineness is ≤15 μm and the viscosity is 25-35 Pa. s, to obtain a uniform, fine electronic paste initial product without obvious particle agglomeration.

[0047] S4: Degassing and maturation. The initial slurry after S3 grinding is transferred to a vacuum degassing machine and degassed for 20 minutes at a vacuum of -0.10 MPa and room temperature to remove air bubbles from the slurry. The slurry is then sealed and maturated at room temperature for 16 hours to ensure that all components are fully wetted and evenly dispersed, resulting in the finished electronic slurry.

[0048] Example 5

[0049] This embodiment provides a method for preparing an electronic paste for a beryllium oxide matrix, specifically including the following steps:

[0050] By mass percentage, the electronic paste of this embodiment consists of 70% metallic functional phase, 10% glass phase, 3% binder, 15.5% solvent, and 1.5% additives. The metallic functional phase consists of 55% tungsten powder and 15% molybdenum powder. The glass phase consists of 2% magnesium oxide, 3% aluminum oxide, 2% silicon dioxide, 1% aluminum nitride, and 2% samarium oxide. The additives consist of 1% sodium polyacrylate and 0.3% castor oil.

[0051] S1: Raw material pretreatment, tungsten powder (D 90 (5μm) and molybdenum powder (D) 90 The powder (5 μm) was placed in a hydrogen atmosphere furnace and reduced at 1100℃ for 1.5 h to remove the oxide layer on the surface of the powder. After cooling to room temperature with the furnace, it was taken out and set aside. Magnesium oxide, aluminum oxide, silicon dioxide, aluminum nitride and samarium oxide were weighed according to the formula and ball-milled at 200 r / min for 4 h to obtain 10% glass phase.

[0052] S2: Preparation of organic carrier: Weigh the binder (ethyl cellulose), solvent (10% terpineol + 5.5% isooctanol) and additives according to the formula. First, add the additives to the solvent and stir for 30 minutes at room temperature and a stirring speed of 500 r / min until the additives are completely dissolved in the solvent. Then add the binder, heat to 65℃, maintain the stirring speed of 600 r / min, and stir at a constant temperature for 2 hours until the binder is completely dissolved. A uniform, transparent organic carrier without particle agglomeration is obtained. After naturally cooling to room temperature, it is ready for use.

[0053] S3: Mixing and Grinding. The pretreated metallic functional phase powder and glass phase powder are added to the organic carrier prepared in S2 according to the specified ratio. The mixture is stirred for 40 minutes at room temperature and a stirring speed of 800 r / min to obtain a preliminary mixed slurry. This slurry is then transferred to a three-roll mill for grinding. The roller spacing is adjusted to 5 μm, the grinding speed is 300 r / min, and the grinding is performed 3-5 times until the slurry fineness is ≤15 μm and the viscosity is 25-35 Pa. s, to obtain a uniform, fine electronic paste initial product without obvious particle agglomeration.

[0054] S4: Degassing and maturation. The initial slurry after S3 grinding is transferred to a vacuum degassing machine and degassed for 20 minutes at a vacuum of -0.08 MPa and room temperature to remove air bubbles from the slurry. The slurry is then sealed and maturated at room temperature for 24 hours to ensure that all components are fully wetted and evenly dispersed, resulting in the finished electronic slurry.

[0055] Comparative Example 1

[0056] The preparation method of the comparative electronic paste is the same as that in Example 2, except that magnesium oxide is not added to the glass phase, and the missing amount is supplemented by solvent.

[0057] Comparative Example 2

[0058] The preparation method of the comparative electronic paste is the same as that of Example 2, except that the amount of samarium oxide added in the glass phase is 8%, and the increase is deducted by solvent.

[0059] Comparative Example 3

[0060] The preparation method of the comparative electronic paste is the same as that of Example 2, except that the amount of aluminum nitride added in the glass phase is 5%, and the increase is deducted by solvent.

[0061] Comparative Example 4

[0062] The preparation method of the electronic paste in this comparative example is the same as that in Example 2, except that the molybdenum powder is replaced with manganese powder by mass.

[0063] Example 6

[0064] This embodiment provides performance testing of electronic pastes.

[0065] Sample preparation: High-purity BeO ceramic substrates (purity ≥99.5%, free of impurities and cracks) were selected. After cutting, the substrates were ultrasonically cleaned with anhydrous ethanol for 20 min and dried for later use. A 200-mesh screen was used to coat the substrate with a thickness of 20±2 μm. The coated samples were placed in an oven, preheated at 85℃ for 35 min, and then heated to 140℃ and held for 1.5 h (for binder removal). Sintering: 1650℃, reducing atmosphere H2:N2=5:95, heating rate 5℃ / min, holding for 2.5 h, and cooling rate 3℃ / min.

[0066] 1. Determination of interfacial bonding strength

[0067] Referring to GB / T 31310-2014 Test Method for Bond Strength of Ceramic Metallization Layers, the shear strength method was adopted. The sintered BeO substrate was cut into 10×10mm specimens with a metallization layer thickness of 20μm. A Ni layer (3μm) + Au layer (0.5μm) was electroplated on the surface of the metallization layer, and a φ1mm oxygen-free copper pillar was welded on. A universal testing machine was used to apply shear force perpendicular to the metallization layer interface at a rate of 0.5mm / min until the metal layer peeled off. Five specimens were tested in each group, and the average value was taken as the interface bond strength (MPa). The test results are shown in Table 1.

[0068] 2. Porosity determination

[0069] Referring to GB / T 1966-2006 Test Method for Apparent Porosity and Bulk Density of Porous Ceramics, the Archimedes' water displacement method was adopted. After sintering, the metallized layer sample was polished to remove surface powder, dried to constant weight, and weighed as dry weight m1; it was then vacuum-impregnated with anhydrous ethanol until saturated, and weighed as suspended weight m2; the sample was removed, the surface ethanol was wiped dry, and weighed as wet weight m3; the porosity was calculated using the formula: P = (m3 - m1) / (m3 - m2) × 100%, and the test results are shown in Table 1.

[0070] 3. Testing of hot and cold cycling performance

[0071] The high and low temperature cycling test method for electronic components was followed according to GJB 33A-1997. The sample was a 20×20mm BeO substrate; it was placed in a high and low temperature test chamber, with a temperature range of -55℃ (holding for 1 hour) → 200℃ (holding for 1 hour), and a heating and cooling rate of 10℃ / min to complete one cycle; after 700 cycles, the surface was observed for cracks / peeling, and the interfacial bonding strength after thermal cycling was tested. The attenuation rate of interfacial bonding strength was calculated, and the test results are shown in Table 1.

[0072] 4. Coefficient of thermal expansion (CTE) testing

[0073] According to GB / T 7962.20-2010 Test Method for Coefficient of Thermal Expansion of Colorless Optical Glass, a thermomechanical analyzer (TMA) was used for testing. The test temperature range was 25~1000℃, the heating rate was 5℃ / min, the thermal expansion of the sample was recorded, and the average coefficient of thermal expansion was calculated. The test results are shown in Table 1.

[0074] Table 1 Performance test results of electronic paste

[0075]

[0076] The electronic paste of this invention has a sintering temperature of 1650℃, which is slightly lower than the ≥1900℃ of the BeO ceramic substrate. This temperature does not alter the substrate's forming state and allows it to form a chemically bonded transition phase with the substrate, significantly improving the interfacial bonding strength. The functional layer prepared using the electronic paste of this invention also possesses superior electrical and thermal properties, with a volume resistivity ≥10⁻⁶. 14 Ω cm (glass phase insulation region), breakdown strength ≥32 kV / mm, thermal conductivity 168~175 W / (m²) K), capable of reacting with the BeO matrix at 260~310 W / (m K) forms a gradient match, and heat is rapidly conducted from the device → functional layer → BeO substrate without heat accumulation.

[0077] As shown in Table 1, the difference between the thermal expansion coefficient of the functional layer and the BeO matrix in this invention is less than 2.5 ppm / K, which can reduce interfacial thermal stress. When MgO is not added to the system, the CTE difference between the sintered functional layer and the BeO matrix increases from less than 2.5 ppm / K to 3.2 ppm / K, and the interfacial thermal stress increases significantly. After 700 cycles of thermal cycling, dense network cracks appear in the functional layer, and the interfacial bonding strength drops to ≤5.5 MPa, completely losing its serviceability. Obvious bulging and detachment are visible after cycling. Excessive addition of samarium oxide in the system will react with the BeO matrix to form a thick and brittle rare-earth beryllium salt transition layer. This transition layer is a brittle phase, which easily becomes a stress concentration point and cannot withstand thermal cycling or external forces. Furthermore, samarium oxide has a high melting point, and excessive amounts will significantly increase the viscosity of the glassy liquid phase, making it difficult to flow and fill the gaps between the metal phases at high temperatures, resulting in increased porosity. Under the combined effect of excessive brittle transition layer and high porosity, interfacial thermal stress cannot be released, and cracks propagate rapidly during cycling. AlN is a highly reactive powder, and excessive addition will easily adsorb residual moisture in the slurry, undergoing a hydrolysis reaction during high-temperature sintering: producing a large amount of residual gas, leading to increased porosity, and the through-pores can also become leakage channels. Although excessive addition of AlN will reduce the CTE difference between the metallization layer and the BeO matrix, the large number of pores generated by AlN hydrolysis leads to a decrease in the toughness of the functional layer and a significant deterioration in overall performance.

[0078] As shown in Table 1, the functional layer prepared by the electronic paste of this invention has superior interfacial bonding strength, low porosity, and low interfacial bonding strength decay rate after thermal cycling. Scanning electron microscopy (SEM) observation of the cross-section of the metallized layer revealed no obvious large pores, and the pore size was ≤1μm. The metal phase of this invention is composed of tungsten powder and molybdenum powder. Molybdenum has excellent corrosion resistance in a high-temperature reducing atmosphere and can form a stable W-Mo alloy phase with tungsten, ensuring the continuity of the conductive path. It can also undergo weak interfacial reactions with the components in the glass phase, enhancing the metal-glass bonding force. After replacing tungsten with manganese, since manganese has much higher chemical reactivity than molybdenum, it is easily oxidized in a reducing atmosphere. The manganese oxide generated during sintering is a semiconductor phase, which destroys the metal conductive network. Furthermore, manganese cannot form a solid solution alloy with tungsten, and it is easy to segregate and oxidize at the grain boundaries. It also cannot form an effective bond with the glass phase components, relying only on physical adhesion, resulting in poor bonding force. After replacement, the interfacial bonding strength drops to ≤6.5MPa. After sintering, the edges of the metallized layer warp, and it directly detaches from the BeO matrix during subsequent packaging or thermal cycling. Due to the thermal expansion coefficient of manganese (CTE≈23.0×10⁻⁶), -6 K -1 The concentration of molybdenum is much higher than that of molybdenum (≈5.3×10). -6 K -1 Replacing molybdenum powder with manganese powder caused a sharp increase in the overall thermal conductivity (CTE) of the metallic phase, completely disrupting its thermal expansion compatibility with the BeO matrix. This resulted in significant interfacial thermal stress during cooling, directly leading to bonding failure. Numerous through-pores appeared within the functional layer, drastically reducing its thermal conductivity and preventing the utilization of the high thermal conductivity advantage of the BeO matrix.

[0079] As described above, the basic principles, main features, and advantages of the present invention have been well described. The above embodiments and specifications are merely descriptions of preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. Various changes and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit and scope of the present invention should fall within the protection scope defined by the present invention.

Claims

1. An electronic paste for a beryllium oxide matrix, characterized in that, The electronic paste, by mass percentage, consists of 60-75% metallic functional phase, 10-20% glass phase, 2-5% binder, 10-20% solvent, and 0.7-2% additives; The glass phase is composed of 2-4% magnesium oxide, 3-5% aluminum oxide, 2-4% silicon dioxide, 1-3% aluminum nitride ceramic, and 2-5% samarium oxide; The metallic functional phase consists of 50-60% tungsten powder and 10-15% molybdenum powder.

2. The electronic paste for a beryllium oxide matrix according to claim 1, characterized in that, The tungsten powder D 90 The molybdenum powder has a density of 5~10 μm and a density of D. 90 The particle size is 5~10μm, and the purity of the tungsten powder and molybdenum powder is ≥99.9%.

3. The electronic paste for a beryllium oxide matrix according to claim 1, characterized in that, The binder is one of ethyl cellulose and polyamide; The solvent is at least one of terpineol and isooctyl alcohol.

4. The electronic paste for a beryllium oxide matrix according to claim 1, characterized in that, The additive consists of 0.5-1.5% dispersant and 0.2-0.5% rheology modifier.

5. The electronic paste for a beryllium oxide matrix according to claim 4, characterized in that, The dispersant is one of BYK-163, sodium polyacrylate, and sodium hexametaphosphate; The rheology modifier is castor oil.

6. The method for preparing the electronic paste for a beryllium oxide matrix according to any one of claims 1 to 5, characterized in that, include: S1: Tungsten powder and molybdenum powder are placed in a hydrogen atmosphere furnace and reduced to remove the oxide layer on the surface of the powder to obtain a metallic functional phase powder; glass phase raw materials are weighed and ball-milled to obtain glass phase powder; S2: Weigh the binder, solvent and additives, add the additives to the solvent and stir for the first time until completely dissolved, then add the binder and stir for the second time until the binder is completely dissolved to obtain the organic carrier; S3: The metal functional phase powder and glass phase powder are added to the organic carrier, and after a third stirring, a slurry coarse material is obtained. After grinding, an electronic slurry primary product is obtained. S4: Vacuum degassing and aging of the initial electronic paste to obtain the electronic paste for beryllium oxide matrix.

7. The preparation method according to claim 6, characterized in that, The reduction temperature is 1050~1100℃, and the reduction time is 1~1.5h; The ball milling mixing speed is 200~250 r / min, and the time is 4~6 h.

8. The preparation method according to claim 6, characterized in that, The first stirring speed is 300~500 r / min, the time is 20~30 min, and the first stirring is carried out at room temperature; The second stirring temperature is 60~70℃, the rotation speed is 500~800r / min, and the time is 1~2h.

9. The preparation method according to claim 6, characterized in that, The third stirring speed is 600~800 r / min, and the time is 30~40 min. The third stirring is carried out at room temperature. The grinding roller spacing is 5~10μm, the grinding speed is 200~300r / min, and the grinding number is 3~5 times.

10. The preparation method according to claim 6, characterized in that, The vacuum degassing is performed at a vacuum level of -0.08 to -0.1 MPa and room temperature for 15 to 20 minutes. The ripening process involves ripening at room temperature for 12-24 hours.

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