Vacuum brazing method suitable for binding ceramic target material and metal back plate

Abstract

The invention relates to the technical field of vacuum brazing of ceramic target materials and metal back plates, in particular to a vacuum brazing method suitable for binding of the ceramic target materials and the metal back plates, and the vacuum brazing method comprises the following steps that S1, ceramic and metal are pretreated; s2, brazing filler metal and auxiliary materials are prepared; s3, charging and vacuum control; s4, carrying out stepped heating and pressurization; and S5, cooling and post-processing. The method has the beneficial effects that the vacuum rate during brazing is adjusted in a gradient mode, temperature-pressure dynamic matching is achieved through cooperative adjustment, the performance of a vacuum brazing joint is improved, and the applicability is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of vacuum brazing of ceramic targets and metal backplates, and specifically relates to a vacuum brazing method suitable for binding ceramic targets and metal backplates. Background Art

[0002] Ceramics have the advantages of high hardness, high strength, high temperature resistance, oxidation resistance, good wear resistance and chemical stability. However, ceramics are brittle, difficult to process, and not easy to connect with other materials. Metals have good toughness, electrical conductivity, thermal conductivity and processing performance. Connecting ceramics and metals can give full play to the advantages of both, obtaining composite materials or components with more excellent performance, and meeting the requirements for high performance of materials in many fields such as aerospace, electronics, and automobiles. Traditional welding methods are difficult to achieve good connection between ceramics and metals because there are great differences in physical and chemical properties between ceramics and metals, such as mismatched thermal expansion coefficients and poor wettability. With the development of vacuum technology and brazing materials, vacuum brazing technology has gradually become an effective way to solve the problem of connecting ceramics and metals.

[0003] In the prior art, vacuum brazing of ceramics and metals often has problems such as a large porosity at the joint and an excessively long surface crack length, which will seriously affect the service life of the product and the product has poor applicability. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present application proposes a vacuum brazing method suitable for binding ceramic targets and metal backplates. By gradually adjusting the vacuum rate during brazing and coordinately adjusting to achieve dynamic matching of temperature and pressure, the performance of the vacuum brazing joint is improved, and the applicability is greatly improved.

[0005] The following is the technical solution of the present invention. A vacuum brazing method suitable for binding ceramic targets and metal backplates includes the following steps: S1. Pretreat the ceramics and metals; S2. Prepare brazing filler metal and auxiliary materials; S3. Load the furnace and control the vacuum; S4. Gradually increase the temperature and pressure in a stepped manner; S5. Cool and perform post-treatment.

[0006] As a preferred solution of the present invention, in S1, for the surfaces to be welded of the ceramics and metals and the area within 8 - 12 mm around the weld seams, use 800-mesh or finer sandpaper to polish until the surface roughness Ra ≤ 0.8 μm.

[0007] As a preferred solution of the present invention, in S1, use a mixed solution of acetone and ethanol with a volume ratio of 1:1 for ultrasonic cleaning, and the cleaning time is 10 - 20 minutes.

[0008] As a preferred embodiment of the present invention, in S2, the filler metal is an Al-Si-Mg alloy foil or an Ag-Cu-Ti active filler metal. When using an Ag-Cu-Ti active filler metal for superalloys, nano-TiC particles are uniformly added through a ball milling process.

[0009] As a preferred embodiment of the present invention, the Ag-Cu-Ti active filler metal contains 4-6 wt% of Ti and 5-10 wt% of nano-TiC particles.

[0010] As a preferred embodiment of the present invention, in S3, the distance between the workpiece and the heating element is ≥50 mm, and heating starts after the vacuum is pumped down to ≤ Pa.

[0011] As a preferred embodiment of the present invention, in S4, the pumping speed of the vacuum pump group is adjusted so that the vacuum degree gradients from Pa to Pa at a gradient rate of 0.1 Pa / min.

[0012] As a preferred embodiment of the present invention, in S4, a stepped temperature increase is adopted: In the first stage, the temperature is increased to 450 °C at a rate of 5 °C / min and held for 30 minutes; In the second stage, the temperature is increased to 50 °C below the melting point of the filler metal at a rate of 10 °C / min and held for 20 minutes; In the third stage, the temperature is increased to the brazing temperature at a rate of 5 °C / min and held for 10-60 minutes, and electromagnetic stirring is used to promote the flow of the filler metal.

[0013] As a preferred embodiment of the present invention, in S4, dynamic matching of temperature and pressure is performed, and pressure is compensated when the temperature changes. The expression is as follows:

[0014] In the above formula, is the compensated pressure, is the compensation coefficient, is the thermal expansion coefficient of the ceramic, is the thermal expansion coefficient of the metal, is the temperature difference, is the contact area; The heating power is adjusted through the PED algorithm, and the expression for the corrected value of the heating power is as follows:

[0015] In the above formula, is the corrected value of the heating power, is the deviation between the set temperature and the actually measured temperature, is the empirical parameter.

[0016] As a preferred embodiment of the present invention, in S5, gradient cooling is adopted: the temperature is decreased to 300 °C at a rate of 5 °C / min, and the heating system is turned off.

[0017] The beneficial effects of the present invention are as follows: by uniformly adding nano-TiC particles through the ball milling process, gradiently adjusting the vacuum rate during brazing, synergistically adjusting to achieve the dynamic matching of temperature and pressure, and performing gradient cooling after brazing, the performance of the vacuum brazed joint is improved, and the applicability is greatly enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of the vacuum brazing method of the present invention; Figure 2 is a flowchart of the vacuum brazing method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] To make the technical problems solved, the technical solutions adopted, and the technical effects achieved by the present invention clearer, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0020] Embodiment: As Figure 1 and Figure 2 shown, a vacuum brazing method applicable to the bonding of a ceramic target and a metal backplane includes the following steps: S1. Pretreat the ceramic and the metal; S2. Prepare the brazing filler metal and auxiliary materials; S3. Load the furnace and control the vacuum; S4. Gradually increase the temperature and pressure in a stepped manner; S5. Cool and perform post-treatment.

[0021] In step S1, the pretreatment of the ceramic and the metal includes the following steps: S11. Grind the surfaces to be welded and the periphery of the weld; For the surfaces to be welded and the 8-12 mm area around the weld of the ceramic (such as ) and the metal (such as titanium alloy), grind with 800-mesh or finer sandpaper until the surface roughness Ra ≤ 0.8 μm; S12. Perform ultrasonic cleaning; Use a mixed solution of acetone and ethanol with a volume ratio of 1:1 for ultrasonic cleaning. The cleaning time is 10-20 minutes to remove oil stains and oxide layers, and then blow dry with compressed nitrogen; S13. Activate the surface by ion sputtering; For aluminum alloy workpieces, the surface is activated by ion sputtering to enhance the wettability of the solder.

[0022] In step S2, solder and auxiliary materials are prepared. Specifically, an aluminum-based solder with a thickness of 0.1 - 0.3 mm, such as an Al-Si-Mg alloy foil, is pre-placed in the joint surface gap and evenly spot-welded at 6 - 10 points along the circumference; for superalloys, such as nickel-based alloys, an Ag-Cu-Ti active solder is used, and nano-TiC particles are added to enhance the high-temperature strength and evenly mixed by a ball milling process. Among them, the Ti content of the Ag-Cu-Ti active solder is 4 - 6 wt%, and the nano-TiC particles are 5 - 10 wt%; in the vacuum brazing of aluminum alloys, magnesium powder is added to the furnace at a ratio of 15 g / m 3 to reduce the oxide film.

[0023] In step S3, the furnace loading and vacuum control are carried out. Specifically, the workpieces are sent into the central constant temperature zone of the vacuum furnace by a forklift, and when stacking, ensure that the distance from the heating element is ≥50 mm. In the preheating stage, the vacuum is pumped to ≤ Pa and then heating starts. Before heating up, the equipment that has been stopped for more than 24 hours is baked. The baking method is: keep warm at 450 ± 20 °C for 1 hour or keep warm at 700 ± 50 °C for 60 minutes.

[0024] In step S4, stepwise heating and pressurization are carried out. Specifically, in the brazing stage, the pumping speed of the vacuum pump group is adjusted so that the vacuum degree gradients from Pa to Pa, and the gradient rate is 0.1 Pa / min.

[0025] Stepwise heating is adopted, and the heating curve is as follows: The first stage: heat up to 450 °C at a rate of 5 °C / min and keep warm for 30 minutes to eliminate residual stress.

[0026] The second stage: heat up to 50 °C below the solder melting point at a rate of 10 °C / min, for example, heat the Al-Si-Mg solder up to 580 °C and keep warm for 20 minutes to make the temperature uniform.

[0027] The third stage: heat up to the brazing temperature at a rate of 5 °C / min, for example, the Al-Si-Mg solder is 600 - 620 °C, and keep warm for 10 - 60 minutes to promote the flow of the solder through electromagnetic stirring.

[0028] Pressure control is carried out, and an axial pressure of 1 - 3 MPa is applied to match the difference in thermal expansion coefficients of the materials and reduce interface voids.

[0029] During the brazing process, the temperature and pressure data are collected in real time through an infrared thermometer and a piezoelectric sensor, and the sampling frequency is ≥10 HZ.

[0030] Due to the different thermal expansion coefficients of ceramics and metals, when the temperature changes, the pressure to be compensated is expressed as follows:

[0031] In the above formula, is the compensation pressure, is the compensation coefficient, is the thermal expansion coefficient of ceramics, is the thermal expansion coefficient of metals, is the temperature difference, is the contact area.

[0032] The heating power is adjusted by the PED algorithm, and the expression of the heating power correction value is as follows:

[0033] In the above formula, is the heating power correction value, is the deviation between the set temperature and the actual measured temperature, is the empirical parameter. In this embodiment, are 0.5, 0.2, and 0.1 respectively.

[0034] When brazing ceramics and metals, due to their different thermal expansion coefficients, temperature changes will cause them to expand or contract to different degrees, thus generating thermal stress at the joint interface. Thermal stress may lead to problems such as cracks and solder joint detachment in the brazed joint, affecting the reliability of the connection. The heating power correction value adjusts the heating power through the PID algorithm, and then controls the temperature, so that the temperature change meets the process requirements and minimizes fluctuations, or generates appropriate as needed. At the same time, the thermal expansion coefficient compensation formula calculates the pressure to be compensated according to . Then, the compensation pressure is applied by adjusting the pressure of the hydraulic servo system to offset the thermal stress generated by the thermal expansion difference. For example, when the heating power increases and the temperature rises, increases, and the calculated according to the thermal expansion coefficient compensation formula will also increase accordingly, and the hydraulic servo system is adjusted to increase the pressure to compensate for the thermal expansion difference.

[0035] The sensor continuously collects data, and the PID controller calculates the heating power correction value in real time according to the temperature deviation and adjusts the heating power; at the same time, it calculates the pressure compensation value according to the thermal expansion coefficient compensation formula and adjusts the pressure of the hydraulic servo system. Through coordinated adjustment, the dynamic matching of temperature - pressure is achieved to compensate for the thermal expansion difference between ceramics and metals. The parameter correction period ≤ 5 seconds.

[0036] S5, Cooling and post - treatment; Gradient cooling is adopted: cool down at a rate of 5°C / min to 300°C, then turn off the heating system and keep it in a vacuum environment to cool naturally to room temperature to avoid cracks caused by rapid cooling.

[0037] S6. Weld inspection and performance verification. Specifically, inspect the weld and verify its performance. The inspection items include: porosity, surface crack length, room temperature shear strength, 800°C creep strength, and 20 thermal shock cycles. The performance is shown in the following table: Table 1 Performance Inspection Table.

[0038]

[0039] From the experimental results in the above table, it can be seen that the porosity meets the porosity requirements (requirement ≤ 2%), there are no cracks or fine cracks on the surface, the room temperature shear strength meets the requirements that the aluminum-based joint ≥ 80 MPa and the superalloy joint ≥ 150 MPa, and the creep strength attenuation of the superalloy joint ≤ 10%. The thermal shock cycle test results also meet the requirements. By uniformly adding nano-TiC particles through the ball milling process, gradient-adjusting the vacuum rate during brazing, synergistically adjusting to achieve the dynamic matching of temperature-pressure, and gradient cooling after brazing, the performance of the vacuum brazed joint is improved, and the applicability is greatly enhanced.

[0040] Target bonding usually involves the connection of ceramic targets (such as Al2O3, Si3N4, etc.) and metal substrates (such as copper, titanium alloy, nickel-based alloy, etc.). The vacuum brazing technology of the present invention effectively solves problems such as thermal expansion mismatch, many interface defects, and poor high-temperature reliability in target bonding through key processes such as pretreatment, solder optimization, coordinated control of temperature and pressure, and gradient cooling, providing a high-performance and highly applicable connection solution for the preparation of targets in high-end fields such as semiconductors and photovoltaics, and significantly improving the service life and stability of target components.

[0041] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Obviously, those skilled in the art can make various changes and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the equivalent technology of the present invention, the present invention also intends to include these modifications and variations.

Claims

1. A vacuum brazing method applicable to the bonding of ceramic targets and metal backplates, characterized in that, It includes the following steps: S1. Pretreat the ceramic and the metal; S2. Prepare the filler metal and auxiliary materials; S3. Load the furnace and control the vacuum; S4. Gradually increase the temperature and pressure in a stepped manner; S5. Cool and perform post-treatment.

2. The vacuum brazing method applicable to the bonding of a ceramic target and a metal backplane according to claim 1, characterized in that, In S1, the surfaces to be welded of the ceramic and the metal and the area within 8 - 12 mm around the weld seam are polished with 800-mesh or finer sandpaper until the surface roughness Ra ≤ 0.8 μm.

3. A vacuum brazing method applicable to the bonding of a ceramic target and a metal backplane according to claim 1, characterized in that, In S1, ultrasonic cleaning is carried out using a mixed solution of acetone and ethanol with a volume ratio of 1:1, and the cleaning time is 10 - 20 minutes.

4. A vacuum brazing method applicable to the bonding of a ceramic target and a metal backplane according to claim 1, characterized in that, In S2, the filler metal is an Al-Si-Mg alloy foil or an Ag-Cu-Ti active filler metal. When using the Ag-Cu-Ti active filler metal for superalloys, nano-TiC particles are uniformly added through a ball milling process.

5. A vacuum brazing method applicable to the bonding of a ceramic target and a metal backplane according to claim 4, characterized in that, The Ti content of the Ag-Cu-Ti active filler metal is 4 - 6 wt%, and the nano-TiC particle content is 5 - 10 wt%.

6. A vacuum brazing method applicable to the bonding of a ceramic target and a metal backplane according to claim 1, characterized in that, In S3, the distance between the workpiece and the heating element is ≥50 mm, and heating starts after the vacuum is pumped down to ≤ Pa.

7. A vacuum brazing method applicable to the bonding of a ceramic target and a metal backplane according to claim 1, characterized in that In S4, adjust the pumping speed of the vacuum pump group so that the vacuum degree ranges from Pa to Pa at a gradient rate of 0.1 Pa / min.

8. A vacuum brazing method applicable to the bonding of a ceramic target and a metal backplane according to claim 1, characterized in that, In S4, the temperature is increased in a stepped manner as follows: In the first stage, the temperature is increased to 450 °C at a rate of 5 °C / min and held for 30 minutes; In the second stage, the temperature is increased to 50 °C below the melting point of the filler metal at a rate of 10 °C / min and held for 20 minutes; In the third stage, the temperature is increased to the brazing temperature at a rate of 5 °C / min and held for 10 - 60 minutes, and electromagnetic stirring is used to promote the flow of the filler metal.

9. A vacuum brazing method applicable to the bonding of a ceramic target and a metal backplane according to claim 1, characterized in that, In S4, dynamic matching of temperature and pressure is carried out, and the pressure is compensated when the temperature changes. The expression is as follows: In the above formula, is the compensation pressure, is the compensation coefficient, is the thermal expansion coefficient of the ceramic, is the thermal expansion coefficient of the metal, is the temperature difference, is the contact area; The heating power is adjusted through the PED algorithm, and the expression for the corrected value of the heating power is as follows: In the above formula, is the heating power correction value, is the deviation between the set temperature and the actually measured temperature, is the empirical parameter.

10. A vacuum brazing method applicable to the bonding of a ceramic target and a metal backplane according to claim 1, characterized in that, In S5, gradient cooling is adopted: the temperature is decreased to 300 °C at a rate of 5 °C / min, and the heating system is turned off.

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