Kovar alloy and ceramic welding composition and application thereof

Abstract

The invention belongs to the technical field of welding, and particularly relates to a composition for Kovar alloy and ceramic welding and application of the composition for Kovar alloy and ceramic welding, for Kovar alloy and ceramic welding, a phosphate-based material is adopted as the welding composition, a metallization pre-plating layer is not needed, the technological process is simplified, and the cost is reduced; and the problem of brittle compounds caused by Ti diffusion in brazing is avoided, the corrosion depth is small, the joint compactness is good, and the excellent comprehensive performance is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of welding, and in particular relates to a composition for welding a 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 is significantly different (Kovar alloy CTE≈5.5×10 -6 / ℃, alumina ceramic CTE≈7.3×10 -6 / ℃), strong thermal stress is generated during cooling, resulting in cracking and deformation of the welding parts. In addition, the traditional metallization layer is prone to corrosion and delamination in high temperature, high humidity, acid and alkali environment, and the interface chemical stability is poor.

[0003] Comparative analysis of the limitations of direct brazing technology (such as CN115555669A) applied to welding of Kovar alloy and 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 generate 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: It requires pre-plating of multiple layers of metal (Ti / Ni), and the process steps are complicated and the cost is high. Although active metal brazing further reduces the temperature, the cost of the brazing material is high, and the wettability to ceramics is still insufficient, making it difficult to achieve high-strength connection. Summary of the invention

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

[0008] The technical solution of the present invention is as follows:

[0009] The present invention provides a composition for welding Kovar alloy and 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 agent.

[0012] The operation is as follows:

[0013] (1) After ball milling, the composition is mixed 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 coating when a preset thickness is reached;

[0015] (3) Using a fixture to assemble the coated Kovar alloy and ceramic, and combining 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;

[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 step (4) of vacuum welding is specifically:

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

[0023] After the Kovar alloy is polished, it is ultrasonically cleaned using acetone as a solvent, and then vacuum dried for later use;

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

[0025] Beneficial Effects

[0026] (1) For welding of Kovar alloy and ceramic, the present invention adopts phosphate-based materials as welding compositions, which does not require metallization pre-plating, simplifies the process flow and reduces costs.

[0027] (2) Avoid the brittle compound problem caused by Ti diffusion during brazing, and 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, and the energy consumption is reduced by more than 60%, which 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 and 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 agent.

[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 the coating.

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

[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 the 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 to create 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 cleaning 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 the fine oil and organic impurities were deeply removed to ensure good wetting and adhesion of the welding materials.

[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 test the moisture content to ensure that it is less than 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, and dust, debris and trace chemical pollutants are effectively removed, creating favorable conditions for uniform coating of welding materials.

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

[0045] In addition, regarding coating, during the operation, precision micro-spraying equipment is used to coat the pretreated 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 accurately controlled within the preset thickness, preferably 0.15-0.25 mm, to avoid material accumulation or deficiency and ensure uniform distribution.

[0046] (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.

[0047] For example, a high-precision customized fixture is used to assemble the coated weldment. The fine-tuning knob and precision measuring ruler are combined to strictly control the gap between the welded surfaces within the preset spacing, preferably 0.03-0.05mm. The three-dimensional optical measuring instrument performs real-time measurement and verification to provide precise spatial conditions for welding and ensure quality consistency.

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

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

[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 welding materials 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 phosphate-based materials. After the insulation is completed, it is cooled to room temperature at 4-6°C / min. Thermocouples accurately monitor temperature changes throughout the process to ensure uniform cooling of the weldment and reduce thermal stress.

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

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

[0053] Example 1

[0054] (1) Preparation of composition

[0055] Weigh aluminum dihydrogen phosphate, borax, titanium dioxide, aluminum oxide, and silicon oxide, put them into a high-energy ball mill, and ball-mill them at a speed of 300 rpm for 4 hours. Use a laser particle size analyzer to ensure that the particle size is less than 40 μm, as 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: A 4 mm × 4 mm × 1.5 mm Kovar sheet and a ceramic sheet were selected. The Kovar sheet was first finely polished with 900-grit sandpaper, then cleaned with acetone in an ultrasonic cleaner at an ultrasonic frequency of 50 kHz for 13 minutes, and finally dried in a vacuum oven at 90°C for 1.5 hours. The ceramic sheet was ultrasonically cleaned with 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 to control the coating thickness 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 and heated to 550°C at a rate of 7°C / min, kept at that temperature for 45 minutes, and then cooled to room temperature at a rate of 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] Weigh aluminum dihydrogen phosphate, borax, titanium dioxide, aluminum oxide, and silicon oxide, put them into a high-energy ball mill, and ball-mill them at a speed of 400 rpm for 3 hours. A laser particle size analyzer is used to detect and ensure that the particle size is 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: A 6 mm × 6 mm × 2 mm Kovar sheet and a ceramic sheet were selected. The Kovar sheet was first finely polished with 800-grit sandpaper, then cleaned with acetone in an ultrasonic cleaner at an ultrasonic frequency of 50 kHz for 12 minutes, and finally dried in a vacuum oven at 95°C for 2 hours. The ceramic sheet was 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 and 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] Weigh aluminum dihydrogen phosphate, borax, titanium dioxide, aluminum oxide, and silicon oxide, put them into a high-energy ball mill, and ball mill them at a speed of 350 rpm for 3.5 hours. A laser particle size analyzer is used to ensure that the particle size is 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: A 5 mm × 5 mm × 2 mm Kovar sheet and a ceramic sheet were selected. The Kovar sheet was first finely polished with 950-grit sandpaper, then cleaned with acetone at an ultrasonic frequency of 55 kHz for 14 minutes in an ultrasonic cleaner, and finally dried in a vacuum oven at 92°C for 1.8 hours. The ceramic sheet was ultrasonically cleaned with 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 and heated to 560°C at a rate of 7.5°C / min, kept at that temperature for 48 min, 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] Weigh aluminum dihydrogen phosphate, borax, titanium dioxide, aluminum oxide, and silicon oxide, put them into a high-energy ball mill, and ball mill them at a speed of 380 rpm for 3.8 hours. A laser particle size analyzer is used to detect and ensure that the particle size is 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: A 7 mm × 7 mm × 2.5 mm Kovar sheet and a ceramic sheet were selected. The Kovar sheet was first finely polished with 850-grit sandpaper, then cleaned with acetone at an ultrasonic frequency of 52 kHz for 13 minutes in an ultrasonic cleaner, and finally dried in a vacuum oven at 90 °C for 1.6 hours. The ceramic sheet was ultrasonically cleaned with 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 was placed in a vacuum furnace and heated to 560°C at a rate of 7.5°C / min, kept at that temperature for 48 min, and then cooled to room temperature at a rate of 5.5°C / min. The temperature curve was 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 detection: In a dry environment, apply 500V DC voltage to both sides of the joint, measure the resistance value and calculate the insulation resistance according to GB / T 10064-2006 "Test method for determining the insulation resistance of solid insulating materials".

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

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

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

[0097] Joint density: Use scanning electron microscope (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 "Metallographic Examination Methods for 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. A composition for welding Kovar alloy and ceramic, 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%.

2. Use of the composition for welding Kovar alloy and ceramics as claimed in claim 1 in welding agent.

3. The use according to claim 2, characterized in that: The operation is as follows: (1) After ball milling, the composition is mixed with ethanol to obtain a slurry; (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 coating when a preset thickness is reached; (3) Using a fixture to assemble the coated Kovar alloy and ceramic, and combining 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; (4) The fixed weldment is vacuum welded.

4. The use according to claim 3, characterized in that: The preset thickness of step (2) is 0.15-0.25 mm.

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

6. The use according to claim 3, characterized in that: The step (4) of vacuum welding is specifically as follows: The temperature was raised to 520-580°C at a rate of 6-8°C / min, and kept at that temperature for 40-50 minutes. After the temperature was raised, the temperature was cooled to room temperature at a rate of 4-6°C / min.

7. The use according to claim 3, characterized in that: In the step (1), the particle size of the composition after ball milling is less than 40 μm.

8. The use according to claim 3, characterized in that: In step (2), the kovar alloy and the ceramic are pretreated before welding, specifically: After the Kovar alloy is polished, it is ultrasonically cleaned using acetone as a solvent, vacuum dried, and set aside; The ceramics were ultrasonically cleaned with deionized water and vacuum dried for later use.

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