Composition for welding Kovar alloy and ceramic and application thereof

Abstract

The present invention belongs to the field of welding technology, and specifically relates to a composition for welding Kovar alloy to ceramics and its application. For welding Kovar alloy to ceramics, the present invention adopts a phosphate-based material as the welding composition, eliminates the need for a metallized pre-plating layer, simplifies the process flow, and reduces costs; avoids the problem of brittle compounds caused by Ti diffusion during brazing, and has a small corrosion depth, good joint density, and excellent comprehensive performance.

Description

Technical Field

[0001] The invention belongs to the technical field of welding, and in particular relates to a composition for welding Kovar alloy and ceramics and an application thereof. Background Art

[0002] Traditional ceramic metallization welding methods such as the molybdenum-manganese method require long-term sintering at ultra-high temperatures (>1500°C), which consumes huge amounts of energy. The thermal expansion coefficient of Kovar alloy and ceramics differs significantly (Kovar alloy CTE≈5.5×10 -6 / ℃, alumina ceramic CTE≈7.3×10 -6 / °C), generating intense thermal stress during cooling, which can cause cracking and deformation in the welded parts. Furthermore, traditional metallization layers are susceptible to corrosion and delamination in high-temperature, high-humidity, acidic, and alkaline environments, and their interface chemical stability is poor.

[0003] Comparative analysis of the limitations of direct brazing technology (such as CN115555669A) applied to welding Kovar alloy to ceramics:

[0004] 1. Contradiction in interface wettability: Although the Ti element in the brazing filler metal can improve the wettability of ceramics, it will diffuse into the Kovar alloy and form brittle compounds (such as Fe2Ni and Ni3Ti) with Fe and Ni, resulting in a decrease in interface strength.

[0005] 2. Density defects: The metal elements in the brazing seam are easily concentrated to form holes or cracks, which reduces the reliability of the joint;

[0006] 3. Process complexity: Pre-plating multiple layers of metal (Ti / Ni) is required, resulting in complex and costly processes. Active metal brazing further reduces the temperature, but the brazing material is expensive and lacks wettability on ceramics, making it difficult to achieve high-strength connections. Summary of the Invention

[0007] The present invention provides a composition for welding Kovar alloy and ceramics and application thereof.

[0008] The technical solutions of the present invention are as follows:

[0009] The present invention provides a composition for welding Kovar alloy to ceramics, wherein the composition comprises the following raw materials in percentage by mass:

[0010] Aluminum dihydrogen phosphate 43%-47%, borax 12%-13%, titanium dioxide 6%-7%, aluminum oxide 24%-26%; silicon oxide 9%-11%.

[0011] The present invention also provides an application of the Kovar alloy and ceramic welding composition in welding agents.

[0012] The operation is as follows:

[0013] (1) ball-milling the composition and mixing it with ethanol to obtain a slurry;

[0014] (2) controlling the spraying equipment to apply the slurry to the surfaces of the Kovar alloy and the ceramic to be welded, respectively, and controlling the spraying equipment to stop applying when the preset thickness is reached;

[0015] (3) Using a fixture to assemble the coated Kovar alloy and ceramic, and combining a fine-tuning knob with a precision measuring ruler, the gap between the Kovar alloy and ceramic surfaces to be welded is controlled within a preset spacing to obtain a fixed weldment;

[0016] (4) The fixed weldment is vacuum welded.

[0017] Furthermore, the preset thickness of step (2) is 0.15-0.25 mm.

[0018] The preset spacing in step (3) is 0.03-0.05 mm.

[0019] The vacuum welding step (4) is specifically as follows:

[0020] The temperature was raised to 520-580°C at a rate of 6-8°C / min, kept at that temperature for 40-50 minutes, and then cooled to room temperature at a rate of 4-6°C / min.

[0021] In the step (1), the particle size of the composition after ball milling is less than 40 μm.

[0022] In step (2), the Kovar alloy and the ceramic are pretreated before welding, specifically as follows:

[0023] After polishing, the Kovar alloy was ultrasonically cleaned using acetone as a solvent, vacuum dried, and set aside for use;

[0024] The ceramics were ultrasonically cleaned with deionized water and vacuum dried for later use.

[0025] Beneficial effects

[0026] (1) For welding Kovar alloy and ceramic, the present invention uses phosphate-based materials as welding compositions, eliminating the need for metallization pre-plating, simplifying the process and reducing costs.

[0027] (2) Avoiding the problem of brittle compounds caused by Ti diffusion during brazing, the shear strength of the welded joint is stable at 35-40MPa, far exceeding the reliability of traditional brazing (about 12MPa). In addition, the corrosion depth is small, the joint density is good, and it has excellent comprehensive performance.

[0028] (3) The welding temperature of the present invention is only 520-580°C, energy consumption is reduced by more than 60%, and it is suitable for industrial production. DETAILED DESCRIPTION

[0029] The following examples are intended to illustrate the present invention rather than to further limit the present invention.

[0030] The present invention provides a composition for welding Kovar alloy to ceramics, wherein the composition comprises the following raw materials in percentage by mass:

[0031] Aluminum dihydrogen phosphate 43%-47%, borax 12%-13%, titanium dioxide 6%-7%, aluminum oxide 24%-26%; silicon oxide 9%-11%.

[0032] The present invention also provides an application of the Kovar alloy and ceramic welding composition in welding agents.

[0033] The operation is as follows:

[0034] (1) After ball milling, the composition is mixed with ethanol to obtain a relatively viscous slurry.

[0035] Preferably, the particle size after ball milling is less than 40 μm.

[0036] (2) Controlling the spraying equipment to apply the slurry to the surfaces of the Kovar alloy and the ceramic to be welded respectively. When the preset thickness is reached, controlling the spraying equipment to stop coating.

[0037] Wherein, in step (2), the kovar alloy and the ceramic are pretreated before welding, specifically as follows:

[0038] The pretreatment operation of the Kovar alloy includes: after the Kovar alloy is polished, ultrasonic cleaning is performed using acetone as a solvent, and vacuum drying is performed for standby use.

[0039] For example, first, use 800-1000 mesh sandpaper to carefully polish the surface of Kovar alloy, and test the surface roughness according to GB / T9258.2-2008. Using XPS testing, it can be found that the surface oxide is greatly reduced, the metal activity is significantly enhanced, and the oxide layer, impurities and oil stains are effectively removed, creating a good active surface for welding.

[0040] Next, the polished Kovar alloy was quickly placed in an acetone ultrasonic cleaner with an ultrasonic frequency of 40-60kHz for 12-15 minutes. The contact angle meter showed that the surface water contact angle was greatly reduced after cleaning, the hydrophilicity was significantly improved, and fine oil stains and organic impurities were deeply removed, ensuring good wetting and adhesion of the welding material.

[0041] Finally, the cleaned Kovar alloy is placed in a vacuum drying oven at 85-95°C and dried for 1.5-2 hours. The Karl Fischer moisture meter is used to check the moisture content to ensure that it is below 500ppm, effectively preventing welding defects such as pores caused by water vapor.

[0042] The ceramic pretreatment operation includes: ultrasonic cleaning of the ceramic using deionized water, vacuum drying, and standby use.

[0043] For example, first, using deionized water as the medium, the ceramics are ultrasonically cleaned at an ultrasonic frequency of 30-50kHz for 18-20 minutes. AFM observations show that the surface roughness is significantly reduced, effectively removing dust, debris and trace chemical pollutants, creating favorable conditions for uniform coating of welding materials.

[0044] The ceramic is then placed in an oven at 105-115°C for 2.5-3 hours and tested by weighing to ensure that the moisture content is extremely low and ensure uniform adhesion of the welding material.

[0045] In addition, regarding coating, during the operation, precision micro-spraying equipment is used to coat the pre-treated Kovar alloy and ceramic welding surfaces at a rate of 0.05-0.1 mm / s. Real-time monitoring by laser confocal microscopy (CLSM) ensures that the coating thickness is precisely controlled at the preset thickness, preferably 0.15-0.25 mm, to avoid material accumulation or deficiency and ensure uniform distribution.

[0046] (3) Use a fixture to assemble the coated Kovar alloy and ceramics, and use a fine-tuning knob and a precision measuring ruler to control the gap between the Kovar alloy and ceramic surfaces to be welded within a preset spacing to obtain a fixed weldment.

[0047] For example, high-precision customized fixtures are used to assemble coated weldments. Combined with fine-tuning knobs and precision measuring rulers, the gap between the welded surfaces can be strictly controlled within a preset spacing, preferably 0.03-0.05mm. Three-dimensional optical measuring instruments perform real-time measurement and verification, providing precise spatial conditions for welding and ensuring quality consistency.

[0048] (4) The fixed weldment is vacuum welded.

[0049] The vacuum welding step (4) is specifically as follows:

[0050] The fixed weldment is quickly placed in a vacuum furnace and heated to 520-580°C at a rate of 6-8°C / min. This rate has been verified by a large number of experiments to ensure the activation of the welding material while avoiding excessive accumulation of thermal stress. After reaching the predetermined temperature, it is kept warm for 40-50 minutes to promote the chemical reaction and diffusion fusion of the phosphate-based material. After the insulation is completed, it is cooled to room temperature at a rate of 4-6°C / min. Thermocouples accurately monitor temperature changes throughout the process to ensure uniform cooling of the weldment and reduce the generation of thermal stress.

[0051] For welding Kovar alloy and ceramic, the present invention adopts phosphate-based materials as welding compositions, does not require a metallized pre-plating layer, simplifies the process flow, and reduces costs.

[0052] The welding temperature of the present invention is only 520-580° C., energy consumption is reduced by more than 60%, and the method is suitable for industrial production.

[0053] Example 1

[0054] (1) Preparation of composition

[0055] Weighing aluminum dihydrogen phosphate, borax, titanium dioxide, aluminum oxide, and silicon oxide, putting them into a high-energy ball mill, and ball milling them at 300 rpm for 4 hours. The particles were checked with a laser particle size analyzer to ensure that the particle size was less than 40 μm, thereby obtaining a composition;

[0056] Calculated by mass percentage, the composition includes 45% aluminum dihydrogen phosphate, 12.5% borax, 6.5% titanium dioxide, 25% aluminum oxide, and 11% silicon oxide.

[0057] (2) Welding

[0058] (21) Pretreatment: 4 mm × 4 mm × 1.5 mm Kovar alloy sheets and ceramic sheets were selected. The Kovar alloy sheets were first finely polished with 900 grit sandpaper, then cleaned in an ultrasonic cleaner with acetone at an ultrasonic frequency of 50 kHz for 13 minutes, and finally dried in a vacuum drying oven at 90 °C for 1.5 hours. The ceramic sheets were ultrasonically cleaned in deionized water at an ultrasonic frequency of 40 kHz for 19 minutes, and then dried in an oven at 110 °C for 2.5 hours.

[0059] (22) Coating: The composition was mixed with ethanol to prepare a slurry, and then coated with a precision micro-spraying device at a rate of 0.08 mm / s, with the coating thickness controlled to be 0.2 mm.

[0060] (23) Assembly and fixation: Use a fixture to assemble the coated Kovar alloy and ceramics, and use a fine-tuning knob and a precision measuring ruler to control the gap between the Kovar alloy and ceramic surfaces to be welded to 0.04 mm to obtain a fixed weldment.

[0061] (24) Vacuum welding: The fixed weldment is placed in a vacuum furnace, heated to 550°C at 7°C / min, kept at this temperature for 45 minutes, and then cooled to room temperature at 5°C / min. The temperature curve is monitored and recorded by a thermocouple throughout the process.

[0062] Example 2

[0063] (1) Preparation of composition

[0064] Weighing aluminum dihydrogen phosphate, borax, titanium dioxide, aluminum oxide, and silicon oxide, putting them into a high-energy ball mill, and ball milling them at 400 rpm for 3 hours. The particle size was checked by a laser particle size analyzer to ensure that it was less than 40 μm, thereby obtaining a composition;

[0065] Calculated by mass percentage, the composition includes 43% aluminum dihydrogen phosphate, 13% borax, 7% titanium dioxide, 26% aluminum oxide, and 11% silicon oxide.

[0066] (2) Welding

[0067] (21) Pretreatment: 6 mm × 6 mm × 2 mm Kovar alloy sheets and ceramic sheets were selected. The Kovar alloy sheets were first finely polished with 800-grit sandpaper, then cleaned with acetone at an ultrasonic frequency of 50 kHz for 12 minutes, and finally dried in a vacuum drying oven at 95 °C for 2 hours. The ceramic sheets were ultrasonically cleaned with deionized water at an ultrasonic frequency of 30 kHz for 20 minutes, and then dried in an oven at 105 °C for 3 hours.

[0068] (22) Coating: The composition was mixed with ethanol to prepare a slurry, and then coated with a precision micro-spraying device at a rate of 0.08 mm / s to control the coating thickness to be 0.18 mm.

[0069] (23) Assembly and fixation: Use a fixture to assemble the coated Kovar alloy and ceramics, and use a fine-tuning knob and a precision measuring ruler to control the gap between the Kovar alloy and ceramic surfaces to be welded to 0.03 mm to obtain a fixed weldment.

[0070] (24) Vacuum welding: The fixed weldment is placed in a vacuum furnace, heated to 580°C at 6°C / min, kept at this temperature for 40 minutes, and then cooled to room temperature at 4°C / min. The temperature curve is monitored and recorded by a thermocouple throughout the process.

[0071] Example 3

[0072] (1) Preparation of composition

[0073] Weighing aluminum dihydrogen phosphate, borax, titanium dioxide, aluminum oxide, and silicon oxide, putting them into a high-energy ball mill, and ball milling them at 350 rpm for 3.5 hours. The particle size was checked by a laser particle size analyzer to ensure that it was less than 40 μm, thereby obtaining a composition;

[0074] Calculated by mass percentage, the composition includes 47% aluminum dihydrogen phosphate, 12% borax, 6% titanium dioxide, 24% aluminum oxide, and 11% silicon oxide.

[0075] (2) Welding

[0076] (21) Pretreatment: 5 mm × 5 mm × 2 mm Kovar alloy sheets and ceramic sheets were selected. The Kovar alloy sheets were first finely polished with 950-grit sandpaper, then cleaned in an ultrasonic cleaner with acetone at an ultrasonic frequency of 55 kHz for 14 minutes, and finally dried in a vacuum drying oven at 92 °C for 1.8 hours. The ceramic sheets were ultrasonically cleaned in deionized water at an ultrasonic frequency of 40 kHz for 19 minutes, and then dried in an oven at 112 °C for 2.8 hours.

[0077] (22) Coating: The composition was mixed with ethanol to prepare a slurry, and then coated with a precision micro-spraying device at a rate of 0.07 mm / s to control the coating thickness to be 0.23 mm.

[0078] (23) Assembly and fixation: Use a fixture to assemble the coated Kovar alloy and ceramics, and use a fine-tuning knob and a precision measuring ruler to control the gap between the Kovar alloy and ceramic surfaces to be welded to 0.05 mm to obtain a fixed weldment.

[0079] (24) Vacuum welding: The fixed weldment is placed in a vacuum furnace, heated to 560°C at a rate of 7.5°C / min, kept at this temperature for 48 minutes, and then cooled to room temperature at a rate of 5.5°C / min. The temperature curve is monitored and recorded by a thermocouple throughout the process.

[0080] Comparative Example

[0081] (1) Preparation of composition

[0082] Weighing aluminum dihydrogen phosphate, borax, titanium dioxide, aluminum oxide, and silicon oxide, putting them into a high-energy ball mill, and ball milling them at 380 rpm for 3.8 hours. The particle size was checked by a laser particle size analyzer to ensure that it was less than 40 μm, thereby obtaining a composition;

[0083] Calculated by mass percentage, the composition includes 50% aluminum dihydrogen phosphate, 13% borax, 7% titanium dioxide, 24% aluminum oxide, and 6% silicon oxide.

[0084] (2) Welding

[0085] (21) Pretreatment: 7 mm × 7 mm × 2.5 mm Kovar alloy sheets and ceramic sheets were selected. The Kovar alloy sheets were first finely polished with 850-grit sandpaper, then cleaned in an ultrasonic cleaner with acetone at an ultrasonic frequency of 52 kHz for 13 minutes, and finally dried in a vacuum drying oven at 90 °C for 1.6 hours. The ceramic sheets were ultrasonically cleaned in deionized water at an ultrasonic frequency of 40 kHz for 20 minutes, and then dried in an oven at 108 °C for 2.6 hours.

[0086] (22) Coating: The composition was mixed with ethanol to prepare a slurry, and then coated with a precision micro-spraying device at a rate of 0.07 mm / s to control the coating thickness to be 0.23 mm.

[0087] (23) Assembly and fixation: Use a fixture to assemble the coated Kovar alloy and ceramics, and use a fine-tuning knob and a precision measuring ruler to control the gap between the Kovar alloy and ceramic surfaces to be welded to 0.05 mm to obtain a fixed weldment.

[0088] (24) Vacuum welding: The fixed weldment is placed in a vacuum furnace, heated to 560°C at a rate of 7.5°C / min, kept at this temperature for 48 minutes, and then cooled to room temperature at a rate of 5.5°C / min. The temperature curve is monitored and recorded by a thermocouple throughout the process.

[0089] Performance Testing

[0090] The vacuum welded weldments obtained in Examples 1-3 and the comparative example were subjected to the following tests and compared.

[0091] Shear strength: Use a universal material testing machine to apply shear force at a constant rate until the joint breaks. Record the maximum load and calculate the shear strength in accordance with GB / T 6396-2008, Test Methods for Mechanical and Process Properties of Composite Steel Plates.

[0092] Insulation resistance test: In a dry environment, apply 500V DC voltage to both sides of the connector, measure the resistance value and calculate the insulation resistance according to GB / T 10064-2006 "Test method for determination of insulation resistance of solid insulating materials".

[0093] Withstand voltage: Gradually increase the voltage to the preset value (e.g. 5kV), maintain for 1 minute, and observe whether breakdown or leakage occurs, in accordance with GB / T 1408.1-2016 "Electrical strength test methods of insulating materials Part 1: Tests at power frequency".

[0094] Corrosion depth: The weldment was immersed in 5% NaCl solution (35°C, 240h). After removing the corrosion products, the surface depression depth was measured according to GB / T 16545-2015 “Corrosion of metals and alloys - Removal and assessment of corrosion products on test specimens”.

[0095] Brittle phase formation: Use a metallographic microscope to observe the joint cross section and analyze whether brittle phases such as Fe2Ni and Ni3Ti are generated in accordance with GB / T 13298-2015 "Methods for the examination of metal microstructures".

[0096] Chemical stability: Immerse the weldment in 10% H2SO4 and 10% NaOH solution (25°C, 48h) and observe the surface corrosion and shedding according to GB / T 1732-2020 "Determination of resistance of paint films to chemical reagents".

[0097] Joint density: Use scanning electron microscopy (SEM) to observe the cross-sectional morphology of the joint and evaluate defects such as holes and cracks; in accordance with GB / T 25779-2010 "Methods for Metallographic Examination of Welded Joints".

[0098] The above test results are organized into a table, see Table 1 for details.

[0099] Table 1 Test comparison

[0100]

[0101]

Claims

1. Application of a composition for welding Kovar alloy and ceramics in a welding flux, characterized in that: The composition comprises the following raw materials in percentage by weight: Aluminum dihydrogen phosphate 43%-47%, borax 12%-13%, titanium dioxide 6%-7%, aluminum oxide 24%-26%; silicon oxide 9%-11%; The application operates as follows: (1) ball-milling the composition and then mixing it with ethanol to obtain a slurry; (2) Control the spraying equipment to apply the slurry to the surfaces of the Kovar alloy and the ceramic to be welded respectively. When the preset thickness is reached, control the spraying equipment to stop coating; (3) Use a fixture to assemble the coated Kovar alloy and ceramic, and use a fine-tuning knob and a precision measuring ruler to control the gap between the Kovar alloy and ceramic surfaces to be welded within a preset distance to obtain a fixed weldment; (4) The fixed weldment is vacuum welded.

2. The use according to claim 1, characterized in that The preset thickness of step (2) is 0.15-0.25 mm.

3. The use according to claim 1, characterized in that The preset spacing in step (3) is 0.03-0.05 mm.

4. The use according to claim 1, characterized in that Step (4) vacuum welding, specifically: The temperature was raised to 520-580°C at a rate of 6-8°C / min, kept at that temperature for 40-50 minutes, and then cooled to room temperature at a rate of 4-6°C / min.

5. The use according to claim 1, characterized in that In step (1), the particle size of the composition after ball milling is less than 40 μm.

6. The use according to claim 1, characterized in that Step (2) Kovar alloy and ceramic are pretreated before welding, specifically: After polishing, the Kovar alloy was ultrasonically cleaned using acetone as a solvent, vacuum dried, and set aside for use; The ceramics were ultrasonically cleaned with deionized water and vacuum dried for later use.

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