Preparation method of lower electrode assembly

Abstract

The invention relates to a preparation method of a lower electrode assembly, and relates to the field of electrode assembly manufacturing, and the preparation method comprises the following steps: an electrode bar is coaxially assembled in a ceramic sleeve to form an electrode assembly, and an annular assembly gap exists between the periphery of the electrode bar and the inner wall of the ceramic sleeve; carrying out sand blasting treatment on the exposed end part of the electrode bar in the electrode assembly to form an annular lead-in gap so as to obtain a pretreatment assembly; and taking the electrode bar in the pretreatment assembly as a substrate, and spraying alloy powder to the peripheral surface of the electrode bar by adopting a thermal spraying process to form a metal coating, thereby obtaining a lower electrode assembly. The lower electrode assembly has the effects of improving the structural stability, the electrical performance and the thermal cycle life of the lower electrode assembly.

Description

A method for fabricating a lower electrode assembly Technical Field

[0001] This application relates to the field of electrode assembly manufacturing, and in particular to a method for preparing a lower electrode assembly. Background Technology

[0002] In the field of semiconductor and LCD panel manufacturing equipment technology, dry etching equipment is widely used in thin-film patterning processes during LCD panel manufacturing. The lower electrode, as a key component in dry etching equipment, significantly impacts etching uniformity and equipment operational reliability. With the continuous development of LCD panel manufacturing technology, higher requirements are being placed on the structural stability, electrical performance, and thermal stability of the lower electrode. Improving the performance of the lower electrode helps to enhance the production quality and efficiency of LCD panels, thus driving the development of the entire LCD panel industry.

[0003] In existing technologies, the lower electrode typically employs a structure of a metal electrode rod and an outer ceramic insulating sleeve. The electrode rod is often made of titanium or titanium alloy, while the ceramic sleeve is usually made of insulating ceramic materials such as alumina. Several conventional methods exist to address issues arising after assembling the electrode rod and ceramic sleeve. One approach is to assemble and use them directly without special treatment; another is to use adhesives to fill the gaps, attempting to enhance the connection between the two; yet another involves strictly controlling the machining precision of the electrode rod and ceramic sleeve to reduce assembly gaps; additionally, sandblasting is a commonly used method to improve the assembly effect by treating the surface.

[0004] However, existing technologies have significant drawbacks. Due to differences in thermal expansion coefficients, processing precision, and assembly tolerances between titanium and ceramic materials, an annular gap forms between the outer circumference of the titanium rod and the inner wall of the ceramic sleeve after assembly. During equipment operation, this gap can easily trigger discharge or plasma intrusion in vacuum and plasma environments, affecting electrode stability; it also leads to discontinuous heat conduction at the gap, causing localized temperature rises or thermal stress concentrations; and after long-term use, particulate contamination may occur within the gap, reducing equipment yield. The traditional method of using adhesives and sandblasting suffers from insufficient reliability and therefore needs improvement. Summary of the Invention

[0005] To address the aforementioned problems, this application provides a method for fabricating a lower electrode assembly.

[0006] The method for preparing a lower electrode assembly provided in this application adopts the following technical solution: A method for preparing a lower electrode assembly includes the following steps: S1, assembling an electrode rod coaxially inside a ceramic sleeve to form an electrode assembly, wherein there is an annular assembly gap between the outer periphery of the electrode rod and the inner wall of the ceramic sleeve; S2, sandblasting the exposed end of the electrode rod in the electrode assembly to form an annular inlet gap, thereby obtaining a pre-treated assembly; S3, using the electrode rod in the pre-treated assembly as a substrate, applying alloy powder to the outer peripheral surface of the electrode rod using a thermal spraying process to form a metal coating, thereby obtaining the lower electrode assembly.

[0007] Sandblasting creates a controllable induction gap between the electrode rod and the ceramic sleeve, facilitating the extension and filling of the subsequent coating. Thermal spraying allows molten alloy powder to accumulate on the surface of the electrode rod and within the gap, forming a continuous and dense metallic coating. This coating, combined with the electrode rod substrate, not only enhances the overall integrity and mechanical load-bearing capacity of the assembly as a structural filler, but its continuous metallic properties also provide a superior transmission path for current and heat compared to air gaps. This improves the uniformity of the electric field distribution and promotes lateral heat diffusion, thereby comprehensively enhancing the structural stability, electrical performance, and thermal cycle life of the electrode assembly.

[0008] Preferably, the electrode rod comprises a titanium rod.

[0009] Preferably, the ceramic sleeve comprises an alumina ceramic sleeve.

[0010] Using titanium rods as electrode rods provides a reliable structural core for the assembly due to their excellent mechanical strength and moderate coefficient of thermal expansion. Combined with alumina ceramic sleeves, their inherent high insulation ensures reliable electrical isolation. The thermal stability of ceramic materials and their physical properties that match those of metals together form a more harmonious matrix in terms of mechanical load-bearing, electric field distribution, and heat conduction. This material combination provides an optimized interface basis for subsequent sandblasting and thermal spraying coatings, enabling the final metal-filled coating to form a tighter bond and complementary performance with the matrix, thereby synergistically improving the overall structural integrity, stability under the working electric field, and thermal stability of the entire electrode assembly.

[0011] Preferably, the sandblasting conditions in step S2 are: abrasive particle size of 40-80 mesh, pressure of 0.3-0.4 MPa, spray gun distance of 300-400 mm, step distance of 2-4 mm, and spray gun moving speed of 900-1100 mm / s.

[0012] By limiting the parameter range of the sandblasting process, the surface of the titanium rod can achieve a suitable roughness while forming a size-controlled annular induction gap. This facilitates the full spread of the subsequent thermal spraying molten particles and their tight bonding with the substrate, thereby generating a denser and more continuous metal filling layer. This dense layer can improve the overall mechanical coherence of the component, and its complete coverage helps to improve the uniformity of the electric field distribution and provides a more efficient path for heat transfer, thereby improving the structural stability, electrical performance, and thermal stability of the electrode component.

[0013] Preferably, the width of the annular inlet gap in step S2 is 0.5-1 mm.

[0014] By controlling the width of the annular inlet gap, a suitable space is provided for the flow, extension and accumulation of molten metal particles in subsequent thermal spraying, which helps to form a fully filled and dense metal coating, thereby improving the overall stability of the electrode assembly under mechanical stress, electric field and thermal cycling conditions.

[0015] Preferably, the alloy powder in step S3 includes NiAl alloy powder.

[0016] During the thermal spraying process, NiAl alloy powder forms an intermetallic compound with an ordered lattice structure in situ. This compound combines the directionality and strength of covalent bonds with the ductility of metallic bonds, enabling the coating to form a well-bonded interface with the electrode rod, enhancing the overall structural integrity of the assembly. Furthermore, its thermal expansion characteristics, coordinated with the electrode rod and ceramic sleeve, help buffer thermal stress and maintain the integrity of the interface during thermal cycling. Simultaneously, while maintaining good electrical and thermal conductivity, the structure of this intermetallic compound endows the coating with superior high-temperature oxidation resistance and structural stability compared to ordinary alloys, thereby improving the electrical performance and thermal stability of the electrode assembly in plasma working environments.

[0017] Preferably, the alloy powder contains 93-97% Ni by mass, with the balance being Al.

[0018] By limiting the proportion of alloy powder, the coating obtained by thermal spraying is mainly composed of intermetallic compound phases represented by Ni3Al, which have an ordered crystal structure. This gives it both high bonding strength and lattice mobility at the microscopic level, which helps the coating and the substrate form a tighter and stronger interface, thereby enhancing the overall structural integrity of the component. While maintaining metallic electrical and thermal conductivity, the phase exhibits an anomalous characteristic of increasing yield strength with increasing temperature and its inherent oxidation resistance, providing additional structural stability for the coating under long-term electrothermal loads in a plasma environment. This is beneficial for maintaining a uniform distribution of the electric field on the electrode surface and efficient heat dissipation, comprehensively improving the component's performance in terms of mechanical load-bearing, electrical operation, and thermal fatigue resistance.

[0019] Preferably, the alloy powder further includes 0.5-1% Y.

[0020] Adding trace amounts of yttrium to alloy powder results in yttrium primarily segregating at grain and phase boundaries in the thermally sprayed coating. This refines the grains and optimizes the coating's microstructure through pinning. This enhances the coating's density and cohesion, strengthens its interface with the substrate, and improves the overall structural load-bearing continuity. Furthermore, yttrium's active element effect helps form a more stable and well-adhesive oxide film at high temperatures. This protective film maintains the electrical and thermal conductivity of the coating metal substrate while enhancing its resistance to oxidation and thermal corrosion. This, in turn, helps the electrode assembly maintain longer-term and more stable electrical and thermal properties in plasma working environments.

[0021] Preferably, the thermal spraying process conditions in step S3 are: spray gun distance 90-110mm, spray gun movement step distance 2-4mm, and spray gun movement speed 900-1100mm / s.

[0022] By limiting the range of process parameters for thermal spraying, the temperature, velocity, and deposition distribution of molten or semi-molten alloy particles when impacting the substrate are controlled, thereby promoting the formation of a dense metal coating with uniform microstructure, low porosity, and good adhesion to the substrate. The consistency of the internal structure of this coating reduces local stress concentration and enhances the structural coherence of the component under mechanical loads. Its complete and uniform coverage provides a coherent electrical and thermal conductivity network, which is conducive to the stable distribution of the surface electric field and the effective conduction of heat during operation. At the same time, suitable process conditions also help to form a favorable residual stress state in the coating, thereby improving the stability of the electrode assembly during long-term thermal cycling.

[0023] Preferably, in step S3, the metal coating covers an area of ​​4-6 mm along the axial direction of the electrode rod.

[0024] By controlling the width of the metal coating along the axial direction of the electrode rod within a suitable range, the coating can fully cover and effectively bridge the annular inlet gap region formed by sandblasting. This width design ensures the continuity of the coating itself as a structural filler, enhancing the mechanical coherence and load-bearing uniformity of the component in the axial direction after bonding with the substrate. At the same time, this dimension also provides sufficient space and path for the distribution of the electric field along the coating surface and the radial dissipation of heat, which helps to reduce the edge effect of the electric field and promote the lateral diffusion of working heat, thereby synergistically improving the structural stability, electrical operation smoothness, and thermal cycling fatigue resistance of the electrode assembly.

[0025] In summary, this application includes at least one of the following beneficial technical effects: 1. A controllable induction gap is formed between the electrode rod and the ceramic sleeve through sandblasting, creating conditions for the extension and filling of the subsequent coating; a thermal spraying process is used to deposit molten alloy powder on the surface of the electrode rod and in the gap to form a continuous and dense metal coating. This metal coating is combined with the electrode rod substrate, which not only serves as a structural filler to improve the integrity of the component and the continuity of mechanical load-bearing, but its continuous metallic properties also provide a transmission path for current and heat that is superior to that of an air gap, which is beneficial to improving the uniformity of the electric field distribution and promoting the lateral diffusion of heat, thereby comprehensively improving the structural stability, electrical performance and thermal cycle life of the electrode assembly.

[0026] 2. Adding trace amounts of yttrium to the alloy powder results in yttrium mainly segregating at grain and phase boundaries in the thermally sprayed coating. This refines the grains and optimizes the microstructure of the coating through pinning. On one hand, this enhances the coating's density and cohesion, while also strengthening its interface with the substrate, thus improving the overall structural load-bearing continuity. On the other hand, the active element effect of yttrium helps to promote the formation of a more stable and well-adhered oxide film at high temperatures. This protective film maintains the electrical and thermal conductivity of the coating metal substrate while enhancing its resistance to oxidation and thermal corrosion. This, in turn, helps the electrode assembly maintain longer-term and more stable electrical and thermal properties in the plasma working environment. Attached Figure Description

[0027] Figure 1 is a cross-sectional view of the electrode assembly.

[0028] Explanation of reference numerals in the attached drawings: 1. Lower electrode assembly; 11. Electrode rod; 12. Ceramic sleeve; 13. Metal coating; 2. Lower insulating layer; 3. Base; 4. Substrate. Detailed Implementation

[0029] This application discloses a method for preparing a lower electrode assembly. Unless otherwise specified, the raw materials used in this application can be obtained from commercially available raw materials. The following is a detailed description of this application in conjunction with the embodiments: Embodiment 1 The electrode rod is a titanium rod, the ceramic sleeve is an alumina ceramic sleeve, and the alloy powder is NiAl alloy powder, which is composed of the following components in terms of mass percentage: Ni 93%, with the balance being Al.

[0030] Electrode rod pretreatment: After grinding the surface of the electrode rod with 400-grit sandpaper, immerse it in anhydrous ethanol, ultrasonically clean it for 3 minutes, rinse it three times with 55℃ deionized water for 1 minute each time, and blow it dry with high-purity nitrogen to complete the electrode rod pretreatment.

[0031] S1. The electrode rod is coaxially assembled inside the ceramic sleeve to form an electrode assembly. There is an annular assembly gap between the outer periphery of the electrode rod and the inner wall of the ceramic sleeve. S2. The exposed end of the electrode rod in the electrode assembly is sandblasted with 40 mesh abrasive, pressure 0.3 MPa, spray gun distance 300 mm, step distance 2 mm, and spray gun moving speed 900 mm / s to form an annular inlet gap of 0.5 mm, resulting in a pre-treated assembly. The pre-treated assembly is ultrasonically cleaned in anhydrous ethanol for 10 min, rinsed three times with 55℃ deionized water for 1 min each time, and dried with high-purity nitrogen. S3. Using the electrode rod in the pre-treated assembly as the substrate, alloy powder is sprayed onto the outer periphery of the electrode rod using a thermal spraying process. The thermal spraying process conditions are: spray gun distance 90 mm, spray gun moving step distance 2 mm, and spray gun moving speed 900 mm / s, forming a metal coating. The metal coating covers a dimension of 4 mm along the axial direction of the electrode rod, resulting in the lower electrode assembly.

[0032] Example 2: The electrode rod is a titanium rod, the ceramic sleeve is an alumina ceramic sleeve, and the alloy powder is NiAl alloy powder, which is composed of the following components by mass percentage: Ni 97%, with the balance being Al.

[0033] Electrode rod pretreatment: After grinding the surface of the electrode rod with 400-grit sandpaper, immerse it in anhydrous ethanol, ultrasonically clean it for 3 minutes, rinse it three times with 55℃ deionized water for 1 minute each time, and blow it dry with high-purity nitrogen to complete the electrode rod pretreatment.

[0034] S1. The electrode rod is coaxially assembled inside the ceramic sleeve to form an electrode assembly. There is an annular assembly gap between the outer periphery of the electrode rod and the inner wall of the ceramic sleeve. S2. The exposed end of the electrode rod in the electrode assembly is sandblasted with 80 mesh abrasive, pressure 0.4 MPa, spray gun distance 400 mm, step distance 4 mm, and spray gun moving speed 1100 mm / s to form a 1 mm annular inlet gap, thus obtaining a pre-treated assembly. The pre-treated assembly is ultrasonically cleaned in anhydrous ethanol for 10 min, rinsed three times with 55℃ deionized water for 1 min each time, and dried with high-purity nitrogen. S3. Using the electrode rod in the pre-treated assembly as the substrate, alloy powder is sprayed onto the outer periphery of the electrode rod using a thermal spraying process. The thermal spraying process conditions are: spray gun distance 110 mm, spray gun moving step distance 4 mm, and spray gun moving speed 1100 mm / s, forming a metal coating. The metal coating covers a dimension of 6 mm along the axial direction of the electrode rod, thus obtaining the lower electrode assembly.

[0035] Example 3: The electrode rod is a titanium rod, the ceramic sleeve is an alumina ceramic sleeve, and the alloy powder is NiAl alloy powder, which is composed of the following components by mass percentage: Ni 95%, with the balance being Al.

[0036] Electrode rod pretreatment: After grinding the surface of the electrode rod with 400-grit sandpaper, immerse it in anhydrous ethanol, ultrasonically clean it for 3 minutes, rinse it three times with 55℃ deionized water for 1 minute each time, and blow it dry with high-purity nitrogen to complete the electrode rod pretreatment.

[0037] S1. The electrode rod is coaxially assembled inside the ceramic sleeve to form an electrode assembly. There is an annular assembly gap between the outer periphery of the electrode rod and the inner wall of the ceramic sleeve. S2. The exposed end of the electrode rod in the electrode assembly is sandblasted. The sandblasting conditions are: abrasive particle size of 60 mesh, pressure of 0.35 MPa, spray gun distance of 350 mm, step distance of 3 mm, and spray gun moving speed of 1000 mm / s, forming an annular inlet gap of 0.75 mm to obtain the pre-treated assembly. The pre-treated assembly is ultrasonically cleaned in anhydrous ethanol for 10 min, rinsed three times with 55℃ deionized water for 1 min each time, and dried with high-purity nitrogen. S3. Using the electrode rod in the pre-treated assembly as the substrate, alloy powder is sprayed onto the outer periphery of the electrode rod using a thermal spraying process. The thermal spraying process conditions are: spray gun distance of 100 mm, spray gun moving step distance of 3 mm, and spray gun moving speed of 1000 mm / s, forming a metal coating. The metal coating covers a dimension of 5 mm along the axial direction of the electrode rod to obtain the lower electrode assembly.

[0038] Example 4 is based on Example 3. The only difference between Example 4 and Example 3 is that in Example 4, the sandblasting conditions in step S2 are: sand particle size 60 mesh, pressure 0.6 MPa, spray gun distance 350 mm, step distance 3 mm, and spray gun moving speed 1000 mm / s.

[0039] Example 5 is based on Example 3. The only difference between Example 5 and Example 3 is that in Example 5, the sandblasting conditions in step S2 are: abrasive particle size of 120 mesh, pressure of 0.35 MPa, spray gun distance of 350 mm, step distance of 3 mm, and spray gun moving speed of 1000 mm / s.

[0040] Example 6 is based on Example 3. The only difference between Example 6 and Example 3 is that the width of the annular inlet gap in step S2 of Example 6 is 0.15 mm.

[0041] Example 7 is based on Example 3. The only difference between Example 7 and Example 3 is that the width of the annular inlet gap in step S2 of Example 7 is 1.3 mm.

[0042] Example 8 is based on Example 3. The only difference between Example 8 and Example 3 is that the alloy powder in step S3 of Example 8 also includes rare earth elements and is composed of the following components in mass percentage: Ni 95%, Y 0.5%, and the balance is Al.

[0043] Example 9 is based on Example 3. The only difference between Example 9 and Example 3 is that the alloy powder in step S3 of Example 9 also includes rare earth elements and is composed of the following components in mass percentage: Ni 95%, Y 1%, and the balance is Al.

[0044] Example 10 is based on Example 3. The only difference between Example 10 and Example 3 is that the alloy powder in step S3 of Example 10 also includes rare earth elements and is composed of the following components in mass percentage: Ni 95%, Y 0.75%, and the balance is Al.

[0045] Example 11 is based on Example 3. The only difference between Example 11 and Example 3 is that the alloy powder in step S3 of Example 11 also includes rare earth elements and is composed of the following components in mass percentage: Ni 95%, Y 0.2%, and the balance is Al.

[0046] Example 12 is based on Example 3. The only difference between Example 12 and Example 3 is that the alloy powder in step S3 of Example 12 also includes rare earth elements and is composed of the following components in mass percentage: Ni 95%, Y 1.2%, and the balance is Al.

[0047] Example 13 is based on Example 3. The only difference between Example 13 and Example 3 is that in Example 13, the thermal spraying process conditions in step S3 are: spray gun distance 40mm, spray gun moving step distance 3mm, and spray gun moving speed 1000mm / s.

[0048] Example 14 is based on Example 3. The only difference between Example 14 and Example 3 is that the thermal spraying process conditions in Example 14 are: spray gun distance 100mm, spray gun moving step distance 3mm, and spray gun moving speed 400mm / s.

[0049] Example 15 is based on Example 3. The only difference between Example 15 and Example 3 is that in Example 15, the metal coating covers an area of ​​2 mm along the axial direction of the electrode rod in step S3.

[0050] Example 16 is based on Example 3. The only difference between Example 16 and Example 3 is that in Example 16, the metal coating covers an area of ​​8 mm along the axial direction of the electrode rod in step S3.

[0051] Comparative Example 1: The electrode rod is a titanium rod, the ceramic sleeve is an alumina ceramic sleeve, and the silicone adhesive is Dow DOWSIL. TM EA-3000.

[0052] S1. The electrode rod is coaxially assembled inside the ceramic sleeve to form an electrode assembly, with an annular assembly gap between the outer periphery of the electrode rod and the inner wall of the ceramic sleeve. S2. The exposed end of the electrode rod in the electrode assembly is sandblasted with 40 mesh abrasive, pressure 0.3 MPa, spray gun distance 300 mm, step distance 2 mm, and spray gun moving speed 900 mm / s to form an annular inlet gap of 0.5 mm, resulting in a pre-treated assembly. The pre-treated assembly is ultrasonically cleaned in anhydrous ethanol for 10 min, rinsed three times with 55℃ deionized water for 1 min each time, and dried with high-purity nitrogen. S3. The silicone adhesive is injected into the annular assembly gap between the outer periphery of the electrode rod and the inner wall of the ceramic sleeve, cured at 150℃ for 2 h, the protruding cured adhesive at the end of the ceramic sleeve is cleaned, the exposed end face of the titanium rod is polished with 400 mesh sandpaper, ultrasonically cleaned in anhydrous ethanol for 5 min, rinsed three times with 55℃ deionized water for 1 min each time, and dried with high-purity nitrogen to obtain the lower electrode assembly.

[0053] Performance testing (1) Coating bonding strength and thermal stability test: ASTM C633 and GB / T 42259-2022 Test method for thermal barrier coatings of metals and other inorganic coatings were selected as standards. A NiAl coating was prepared on the same titanium material as the electrode rod using the same process. One end of the coating was machined into a flat circular surface with a diameter of 25.4 mm. A high-strength adhesive (FM1000 polyamide-epoxy resin film) was used to bond the coated surface to an uncoated mating fixture. After the adhesive was fully cured, a sample was obtained. The sample was mounted on the self-aligning fixture of the universal testing machine, and a tensile load perpendicular to the coating surface was applied at a constant rate of 0.02 mm / s. The maximum failure load was recorded. Bonding strength (MPa) = maximum load (N) / bonding area (mm²) 2 For each test sample, three samples were prepared, and the average value was taken after measurement. The results were recorded in Table 1. The test sample was placed in a muffle furnace at 300℃ and held for 5 minutes. Then it was quickly transferred to deionized water at 25℃ for quenching. After the test sample cooled to 25℃, one cycle was completed. This process was repeated 100 times. The bonding strength of the test sample after thermal shock was tested and calculated. The strength retention rate was calculated. For each test sample, three samples were prepared, and the average value was taken after measurement. The results were recorded in Table 1.

[0054] (2) High-voltage arc test: The lower electrode assembly was installed on the insulating support in the vacuum chamber. The electrode rod (titanium rod) was connected to the high-voltage end of the radio frequency power supply (13.56MHz). The outer wall of the ceramic sleeve was grounded. The vacuum chamber was evacuated to 0.1Pa. The radio frequency high voltage was gradually applied from 500V, with an amplitude increase of 100V per step. The voltage was stabilized and monitored for 2 minutes at each voltage level. An electric field was formed between the electrode rod and the grounding end. The flashover voltage of the coating-filled area at the end of the electrode assembly was continuously monitored by a high-speed camera and a plasma emission spectrometer when an arc occurred. The results are recorded in Table 1.

[0055] Table 1. Test results of structural stability, thermal stability, and electrical performance of the lower electrode assembly. As shown in Table 1, the bonding strength of Examples 1-3 is greater than 57.2 MPa, the strength retention rate is greater than 89.7%, and the flashover voltage is greater than 1900 V, thus demonstrating that the lower electrode assembly prepared in this application has good structural stability, thermal stability, and electrical performance.

[0056] As shown in Table 1, in Examples 4-5, the sandblasting parameters were changed. Excessive sandblasting pressure or excessively fine sand particles would cause micro-damage to the substrate or insufficient coarsening, thereby weakening the bonding strength and arc resistance. In Examples 6-7, the gap width was changed. Too narrow a gap would result in an undense coating, while too wide a gap would result in high bridging stress in the coating, and all properties would decrease.

[0057] As shown in Table 1, the addition of rare earth elements to the alloy powder in Examples 8-12 and the addition of an appropriate amount of yttrium optimized the performance, while insufficient or excessive content could not achieve the best effect. The performance improvement effect of Examples 11 and 12 was reduced.

[0058] As shown in Table 1, in Examples 13-14, the spraying parameters were changed. Too close a spraying distance caused overheating and high stress, and too slow a moving speed caused local overheating, which damaged the coating quality. In Examples 15-16, the spraying width of the coating was changed: if the coating was too narrow, the seal would not be tight, and if the coating was too wide, unnecessary stress would be introduced, and the performance of both would decrease.

[0059] As shown in Table 1, when adhesive is used to seal the gap in Comparative Example 1, the organic material has poor temperature resistance and bonding strength, resulting in significant performance degradation.

[0060] This specific embodiment is merely an explanation of this application and is not intended to limit it. Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of this application. The technical scope of this application is not limited to the contents of the specification but must be determined according to the scope of the claims.

Claims

1. A method for preparing a lower electrode assembly, characterized in that: Includes the following steps: S1. The electrode rod is coaxially assembled inside the ceramic sleeve to form an electrode assembly, with an annular assembly gap between the outer periphery of the electrode rod and the inner wall of the ceramic sleeve; S2. The exposed end of the electrode rod in the electrode assembly is sandblasted to form an annular inlet gap, resulting in a pre-treated assembly; S3. Using the electrode rod in the pre-treated assembly as a substrate, alloy powder is sprayed onto the outer periphery of the electrode rod using a thermal spraying process to form a metal coating, resulting in the lower electrode assembly.

2. The method for preparing a lower electrode assembly according to claim 1, characterized in that: The electrode rod includes a titanium rod.

3. The method for preparing a lower electrode assembly according to claim 1, characterized in that: The ceramic sleeve includes an alumina ceramic sleeve.

4. The method for preparing a lower electrode assembly according to claim 1, characterized in that: The sandblasting conditions in step S2 are as follows: abrasive particle size 40-80 mesh, pressure 0.3-0.4 MPa, spray gun distance 300-400 mm, step distance 2-4 mm, and spray gun moving speed 900-1100 mm / s.

5. The method for preparing a lower electrode assembly according to claim 1, characterized in that: The width of the annular inlet gap in step S2 is 0.5-1mm.

6. The method for preparing a lower electrode assembly according to claim 1, characterized in that: The alloy powder in step S3 includes NiAl alloy powder.

7. The method for preparing a lower electrode assembly according to claim 6, characterized in that: The alloy powder contains 93-97% Ni by mass, with the balance being Al.

8. The method for preparing a lower electrode assembly according to claim 7, characterized in that: The alloy powder also contains 0.5-1% Y.

9. A method for preparing a lower electrode assembly according to claim 1, characterized in that: In step S3, the thermal spraying process conditions are: spray gun distance 90-110mm, spray gun movement step distance 2-4mm, and spray gun movement speed 900-1100mm / s.

10. A method for preparing a lower electrode assembly according to claim 1, characterized in that: In step S3, the metal coating covers an area of ​​4-6 mm along the axial direction of the electrode rod.

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