Zinc oxide varistor based on laser composite processing and surface treatment method thereof

Abstract

The application belongs to the technical field of metal oxide varistor manufacturing, and particularly relates to a zinc oxide resistor disc based on laser composite processing and a surface treatment method thereof. The surface treatment method of the zinc oxide resistor disc provided by the application comprises the following steps in sequence: short pulse laser scanning on a surface to be treated of a sintered zinc oxide resistor disc blank, continuous laser remelting scanning, and metal electrode preparation. The two-step composite processing scheme of short pulse laser cleaning combined with continuous laser remelting is adopted to perform precision modification treatment on the surface of the zinc oxide resistor disc blank, so that non-contact precision cleaning, microscopic defect repair and surface function strengthening are realized, the damage problem of mechanical grinding is overcome, and the surface quality, electrode bonding strength and electrical reliability of the zinc oxide resistor disc are significantly improved. The application has a wide application prospect in the modification and processing of zinc oxide resistor discs.

Description

Technical Field

[0001] This invention belongs to the field of metal oxide varistor manufacturing technology, specifically relating to a zinc oxide resistive sheet based on laser composite processing and its surface treatment method. Background Technology

[0002] Zinc oxide resistor elements are the core component of surge arresters (also known as lightning arresters), and their nonlinear volt-ampere characteristics directly determine the overvoltage protection performance of the equipment. The manufacturing process of resistor elements typically includes key steps such as batching, granulation, molding, sintering, and post-processing.

[0003] Sintering is a crucial step in imparting specific microstructure and electrical properties to zinc oxide resistor sheets. However, during high-temperature sintering, factors such as the volatilization and migration of additives (e.g., Bi₂O₃, Sb₂O₃), uneven grain growth, and thermal stress during cooling inevitably lead to the formation of a defect layer on the resistor sheet surface, consisting of loose oxides, microcracks, and pores. This surface defect layer is typically rough and uneven, which not only interferes with the bulk characteristic characterization of the resistor sheet but, more importantly, severely affects the adhesion and contact quality of subsequent metal electrode (e.g., aluminum electrode) deposition. Insufficient electrode adhesion can easily lead to electrode detachment under thermal or electrical shock, resulting in localized overheating or even device failure.

[0004] Currently, mechanical grinding (such as grinding with abrasive wheels) is widely used in the industry as the standard post-processing technology for sintered resistor sheets, aiming to remove the surface oxide layer and obtain a relatively flat reference surface. However, this traditional process has several inherent defects: (1) Non-uniformity of material removal: Mechanical grinding is a contact and stress-based process, which can easily introduce mechanical stress or even microcracks on the surface and subsurface of the resistor sheet. These micro-damages may become hidden dangers for the deterioration of electrical performance. (2) Dust pollution and material loss: A large amount of ceramic dust generated by grinding needs to be specially treated, and this process is a net removal of material, resulting in waste of raw materials. (3) Limited processing accuracy and consistency: It is difficult to achieve micron-level precision and selective processing, and the adaptability to the surface state of resistor sheets in different batches or different positions in the same batch is poor, making it difficult to guarantee processing consistency. (4) Single function: It only achieves flattening and cleaning, and cannot perform functional optimization of the surface, such as improving the microstructure to enhance electrode adhesion.

[0005] To address these issues, the industry has also sought non-contact processing methods. Laser processing, as a precise and controllable energy source, has been applied to the surface treatment of various materials. For example, patent application CN113130160A discloses a method for cleaning semi-finished zinc oxide resistor sheets using lasers. However, the aforementioned prior art only involves a single laser processing operation and achieves a single cleaning purpose. It fails to recognize and solve the comprehensive problem of repairing multiple defects such as loose oxide layers and microcracks that simultaneously exist on the surface of the sintered resistor sheet, and it does not propose a technical concept for how to achieve complete reconstruction of the zinc oxide resistor sheet surface.

[0006] Therefore, there is an urgent need to develop a comprehensive post-processing method that can take into account high-precision surface cleaning, micro-defect repair and surface functional enhancement, so as to improve the application reliability and electrical stability of zinc oxide resistor sheets. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, one of the objectives of this invention is to provide a surface treatment method for zinc oxide resistor sheets based on laser composite processing. This invention utilizes a two-step composite processing scheme of non-contact pulsed laser cleaning and continuous laser remelting, achieving integrated processing for removing the surface oxide layer, repairing microscopic defects, and enhancing surface functionality. This results in zinc oxide resistor sheets with a dense, smooth surface and excellent electrode bonding performance, solving problems such as mechanical damage, limited functionality, and poor consistency in existing surface treatment processes after sintering of zinc oxide resistor sheets.

[0008] The second objective of this invention is to provide a zinc oxide resistor sheet obtained by the above-mentioned surface treatment method, which has a unique microstructure and surface modification layer on its surface, and possesses excellent interface reliability and electrical stability.

[0009] To achieve the above objectives, the first aspect of the present invention adopts the following technical solution: A surface treatment method for zinc oxide resistive sheets based on laser composite processing includes the following steps: S1. The surface to be treated of the sintered zinc oxide resistor sheet blank is subjected to short-pulse laser scanning; the process conditions for short-pulse laser scanning are: wavelength of 1000~1100nm, pulse width of 100~150ns, repetition frequency of 40k~60kHz, laser spot diameter of 40~60μm, scanning line spacing of 30~50μm, scanning speed of 400~600mm / s, and laser power of 5~12W. S2. The surface of the zinc oxide resistor sheet blank after step S1 is subjected to continuous laser remelting scanning to melt and solidify the material within a micrometer-level depth on the surface, thereby forming a laser-modified layer on the surface to be treated; the process conditions of the continuous laser remelting scanning are: wavelength of 1050~1120nm, laser power of 60~100W, spot diameter of 80~120μm, scanning speed of 1200~1800mm / s, and scanning line spacing of 60~100μm; S3. Prepare a metal electrode on the laser-modified layer of the zinc oxide resistor blank to obtain the finished zinc oxide resistor.

[0010] The short-pulse laser scanning used in step S1 of this invention is a nanosecond pulse laser. This invention removes the oxide layer and deposits on the surface to be treated by short-pulse laser scanning to achieve a cleaning effect. This invention does not specifically limit the parameters of the short-pulse laser scanning. Technicians can adaptively adjust the laser processing parameters within the above-mentioned laser process range. The energy density configuration of the processing process is capable of selectively stripping the surface oxide layer without damaging the internal dense main structure.

[0011] Preferably, based on the above scheme, before short-pulse laser scanning, an online detection device can be set up to detect the surface morphology of the zinc oxide resistor blank, and the process parameters of short-pulse laser scanning can be adaptively adjusted according to the detection results. This preferred scheme introduces online feedback, making the processing intelligent and adaptive. By sensing the surface condition in real time (such as oxide layer thickness and roughness) and dynamically adjusting parameters such as laser energy and scanning speed, it is possible to ensure that the processing effect is uniform and reliable for different batches or different areas of the same resistor blank, thereby improving the robustness of the process and the consistency of the product.

[0012] Based on the above scheme, preferably, in step S1, the process conditions for the short pulse laser scanning are: wavelength of 1064nm, pulse width of 120ns, repetition frequency of 50kHz, laser spot diameter of 50μm, scanning line spacing of 40μm, scanning speed of 500mm / s, and laser power of 8W.

[0013] Based on the above scheme, preferably, in step S1, after the short pulse laser scanning, a step of purging with clean air is also included.

[0014] Based on the above scheme, preferably, in step S2, the process conditions for continuous laser remelting scanning are: wavelength of 1080nm, laser power of 80W, spot diameter of 100μm, scanning speed of 1500mm / s, and scanning line spacing of 80μm.

[0015] Preferably, in step S2, the micrometer-level depth is 1~50μm, based on the above scheme.

[0016] Preferably, in step S2, the laser beam path of the continuous laser remelting scan is a preset microstructure pattern. In this invention, by controlling the scanning path of the continuous laser remelting scan, a regular micron-level surface texture can be constructed while a dense layer is formed through remelting. These microstructure patterns not only significantly improve the adhesion of subsequent metal electrodes by increasing the mechanical interlocking area, but also play a potential role in regulating the surface electric field distribution and suppressing edge discharge, thereby endowing the surface to be treated with functional gains beyond flatness and density.

[0017] This invention configures the path of continuous laser remelting scanning to form a preset microstructure pattern on the surface to be treated. This microstructure pattern is formed by laser etching and is used to enhance electrode adhesion. Preferably, based on the above scheme, the microstructure pattern is one or more of a periodically arranged array of pits, grids, and trenches; the depth of the microstructure pattern is 1~50μm, and the feature size is 10~200μm.

[0018] Preferably, based on the above scheme, the surface roughness Ra of the laser-modified layer is not greater than 1.0 μm.

[0019] Based on the above scheme, preferably, in step S3, before the metal electrode is prepared, the zinc oxide resistor blank is further cleaned and dried; the cleaning is performed by ultrasonic cleaning using deionized water as the medium.

[0020] Preferably, in step S3, the metal electrode is an aluminum electrode, based on the above scheme. The metal electrode is prepared using magnetron sputtering technology.

[0021] The second aspect of this invention is the following technical solution: A finished zinc oxide resistor sheet obtained by the surface treatment method described above.

[0022] The zinc oxide resistor sheet product provided by the present invention includes a main body made of zinc oxide resistor material and a laser-modified layer located on at least one surface of the main body; the laser-modified layer is a dense layer formed by rapid solidification after laser remelting of the surface material of the main body.

[0023] Preferably, based on the above scheme, the surface of the laser-modified layer has a microstructure pattern formed by laser etching to enhance electrode adhesion.

[0024] In this invention, the laser-modified layer is a non-equilibrium product of rapid solidification via laser remelting. Its fine grains and dense structure give it superior mechanical integrity and chemical stability compared to the substrate. Furthermore, the microstructural patterns on the surface serve as physical evidence of precise laser processing and directly reflect the product's functionality. Therefore, the composite surface features of the dense layer combined with the microstructure of this invention cannot be achieved through traditional grinding processes or single laser processing techniques.

[0025] The technical solution of the present invention has the following advantages and beneficial effects: The surface treatment method for zinc oxide resistors provided by this invention combines pulsed laser precision etching and cleaning with continuous laser local remelting, and applies them sequentially to the surface treatment of zinc oxide resistors. Specifically, the photothermal ablation or photochemical decomposition effect of short-pulse lasers precisely peels away the loose oxide layer and contaminants on the surface without conducting excessive heat, exposing a relatively clean substrate. Subsequently, the stable heat input of a continuous laser is used to rapidly solidify an extremely thin layer on the cleaned substrate surface. This remelting process effectively heals surface microcracks that may be left by the short-pulse laser process or those generated during the original sintering, and refines the surface grains through rapid solidification, forming a dense, low-roughness laser-modified layer. Therefore, the composite laser processing technology of this invention overcomes the shortcomings of single laser cleaning, which may damage the substrate, or single laser remelting, which may be ineffective due to surface contamination. It synergistically achieves complete surface reconstruction from cleaning to repair and strengthening.

[0026] The surface processing method provided by this invention has the following unique advantages: First, it is a non-contact, stress-free processing method, completely avoiding the stress damage and micro-crack risks introduced by mechanical grinding, thus improving the mechanical reliability of the product. Second, it integrates functions into a single process flow, sequentially realizing surface cleaning, defect repair, and microstructure construction, simplifying the process and improving efficiency. Third, it optimizes both surface quality and function, resulting in a surface that is not only low in roughness and dense and smooth, but also possesses microstructures that enhance electrode adhesion, fundamentally improving the interface bonding quality between the electrode and the resistor sheet, which is beneficial for improving the reliability of the surge arrester under long-term operation and electrical impulses. Fourth, it offers high processing precision and controllability, with laser processing parameters that can be precisely controlled, resulting in good product consistency and minimal material waste.

[0027] Therefore, this invention uses laser composite processing technology to precisely modify the surface of the sintered zinc oxide resistor blank, achieving non-contact precision cleaning, micro-defect repair and surface function enhancement, overcoming the damage problem of mechanical grinding, and significantly improving the surface quality, electrode bonding strength and electrical reliability of the zinc oxide resistor. It has broad application prospects in the modification and processing of zinc oxide resistors. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described clearly and completely below in conjunction with specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Therefore, the following embodiments of this invention are merely exemplary. Various improvements and changes can be made to the specific embodiments described in this specification without departing from the scope or spirit of this invention, which will be obvious to those skilled in the art.

[0029] Unless otherwise stated, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. While only preferred methods and materials have been described in this invention, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. Furthermore, the terms "comprising," "including," "having," "containing," etc., as used in this invention are open-ended, meaning they include but are not limited to.

[0030] In the following embodiments of the present invention, the surface treatment method of zinc oxide resistor blanks prepared by sintering and without post-treatment is described as an example. The present invention does not impose any particular limitation on zinc oxide resistor blanks, and those skilled in the art can use conventional formulas and conventional sintering processes to prepare them. Specifically, the preparation process of zinc oxide resistor blanks used in the following examples and comparative examples is as follows: (1) Ingredients: Weigh the following raw materials by mass percentage: ZnO 91.5%, Bi2O3 3.2%, Sb2O3 2.5%, Co2O3 1.0%, MnO2 0.8%, Cr2O3 0.5%, SiO2 0.3%, Al(NO3)3·9H2O 0.2%. Place all raw materials in a ball mill jar, use deionized water as the medium, add zirconia balls, and ball mill for 12 hours to mix the components evenly and obtain a slurry. Dry the slurry at 120°C for 12 hours, pass it through an 80-mesh sieve, and obtain a mixed powder. (2) Granulation: Add 8% polyvinyl alcohol (PVA) as a binder to the mixed powder as a total mass of powder. After thorough mixing, granulate the powder using a spray granulation equipment to obtain spherical granules with a particle size of 80~150μm. (3) Molding: Fill the granulated powder into a mold and press it under a pressure of 150MPa to obtain a round green blank with a diameter of 34mm and a thickness of 20mm. (4) Debinding: Place the green blank in a muffle furnace and heat it to 500℃ at a heating rate of 2℃ / min. Hold it at 2h to completely remove the organic binder. (5) Sintering: Place the debinded green blank in a high-temperature sintering furnace and heat it to 1180℃ at a heating rate of 5℃ / min. Hold it at 1180℃ for 2h and then cool it to room temperature with the furnace to obtain the zinc oxide resistance sheet green blank. The surface of the sintered zinc oxide resistor blank has a loose oxide layer and sintering residues. The initial surface arithmetic mean roughness (Sa) was measured to be 3.8 μm using a white light interferometer.

[0031] In the following embodiments of the present invention, the nanosecond pulsed fiber laser used is purchased from Apache Fiber Laser Technologies Co., Ltd., model IPG Photonics YLPN-1-4x200-50. The continuous fiber laser used is purchased from Apache Fiber Laser Technologies Co., Ltd., model IPG Photonics YLR-200-AC.

[0032] Example 1

[0033] This embodiment provides a surface treatment method for zinc oxide resistive sheets based on laser composite processing, including the following steps: S1. Prepare a batch of sintered and untreated zinc oxide resistor blanks as samples to be processed. The diameter of the zinc oxide resistor blanks is 34 mm and the thickness is 20 mm. The initial surface arithmetic mean roughness (Sa) of the zinc oxide resistor blanks was measured to be 3.8 μm using a white light interferometer, and there were obvious loose layers and sintering residues on the surface.

[0034] S2. Fix the zinc oxide resistance sheet blank onto a five-axis laser processing stage. Use a nanosecond pulsed fiber laser to perform pulsed laser scanning on the upper surface of the resistance sheet blank. The pulsed laser process parameters are set as follows: wavelength 1064nm, pulse width 120ns, repetition frequency 50kHz, laser spot diameter 50μm, scan line spacing 40μm, scanning speed 500mm / s, laser power 8W. A serpentine fill path is used to perform a full-coverage scan of the entire surface to be processed. Based on the surface area of ​​the resistance sheet (diameter 34mm, single-sided area 908mm²), ... 2 The scanning parameters were calculated, and the scanning time for each blank was 45 seconds per side. The loose oxide layer on the surface of the blank was removed through the ablation effect of the pulsed laser scanning. After treatment, the surface was blown with clean air to remove any loose dust and oxide particles. Subsequently, the resistor blank was flipped over and refixed, and the lower surface of the resistor blank was treated using the same pulsed laser scanning process as described above.

[0035] S3. Immediately switch to a continuous fiber laser to perform continuous laser remelting scanning on the upper surface of the zinc oxide resistor blank after step S2. The process parameters for continuous laser remelting scanning are set as follows: wavelength 1080nm, laser power 80W, spot diameter 100μm, scanning speed 1500mm / s, scanning line spacing 80μm, and a serpentine filling path to perform full-coverage scanning of the entire surface to be treated. Based on the surface area of ​​the resistor blank and the scanning parameters, the single-sided remelting scanning time for each blank is calculated to be 23s. During this process, the extremely thin surface layer (5-10μm depth) is instantly melted by the continuous laser energy and solidified by rapid heat conduction from the substrate, forming a dense surface modification layer. Subsequently, the resistor blank is flipped over and refixed, and the lower surface of the resistor blank is treated using the same continuous laser remelting scanning process as described above.

[0036] S4. The resistor sheet treated in step S3 is placed in an ultrasonic cleaner using deionized water as the cleaning medium and ultrasonically cleaned at a frequency of 40kHz for 10 minutes. Then, the surface moisture is dried with clean compressed air. Next, metal electrodes are prepared on the upper and lower surfaces of the resistor sheet. The metal electrodes are aluminum electrodes, and their preparation process is as follows: The zinc oxide resistor sheet blank treated as described above is placed in a magnetron sputtering coating equipment, and a vacuum is drawn to a vacuum degree of not less than 5×10⁻⁶. ﹣3Pa, high-purity argon gas is introduced as the working gas, the magnetron sputtering power is 5kW, the sputtering time is 10min, and an aluminum metal layer with a thickness of 5~8μm is deposited on the upper and lower surfaces of the resistor sheet by magnetron sputtering, thereby obtaining the zinc oxide resistor sheet product of this embodiment.

[0037] Example 2

[0038] This embodiment provides a surface treatment method for zinc oxide resistor sheets based on laser composite processing. The process is basically the same as that in Embodiment 1, except that step S3 is different.

[0039] Step S3 of this embodiment is adjusted as follows: immediately switch to a continuous fiber laser to perform continuous laser remelting scanning on the upper surface of the zinc oxide resistance sheet blank after step S2. Simultaneously with the remelting scan, the laser beam moves along a preset concentric circular path via a matching laser dynamic galvanometer control system. The process parameters for continuous laser remelting scanning are set as follows: wavelength 1080nm, laser power 80W, spot diameter 100μm, scanning speed 1500mm / s, and scanning line spacing 80μm. After processing, the laser energy causes the extremely thin surface layer (5-10μm depth) to melt instantaneously and solidify due to rapid heat conduction from the substrate. Simultaneously, a series of concentric circular groove microstructures with a depth of 15μm and a width of 50μm are formed on the surface of the blank, with a ring spacing of 200μm, thereby obtaining a dense surface modification layer. Subsequently, the resistance sheet blank is flipped and refixed, and the lower surface of the resistance sheet blank is treated using the same continuous laser remelting scanning process as described above. The remaining processes remain unchanged, thus obtaining the zinc oxide resistor sheet product of this embodiment.

[0040] Comparative Example 1 This comparative example provides a surface treatment method for zinc oxide resistor sheets, which is a common surface treatment method for mechanically grinding sheets in the prior art. The specific steps are as follows: S1, same as step S1 in Example 1.

[0041] S2. Fix the zinc oxide resistance sheet blank onto the worktable of a precision surface grinder, and perform surface grinding on the upper surface of the blank using a resin-bonded diamond grinding wheel (grit size #400). The grinding process parameters are set as follows: grinding wheel linear speed 25 m / s, workpiece feed speed 0.5 m / min, and grinding depth 0.05 mm. A water-based coolant is used for thorough cooling during the grinding process to reduce grinding heat.

[0042] S3. Flip the resistor sheet and re-fix it. Grind its lower surface using the same grinding parameters as in step S2 to obtain a flat reference surface on both sides. The material removal thickness on one side is 0.05~0.10mm.

[0043] S4. Same as step S4 in Example 1, thus obtaining the finished zinc oxide resistor sheet of the comparative example.

[0044] Comparative Example 2 This comparative example provides a surface treatment method for zinc oxide resistor sheets, which adopts a single-pulse laser scanning process. The specific steps are similar to those in Example 1, except that step S3 in Example 1 is omitted, while the remaining steps and parameters are the same as in Example 1.

[0045] Comparative Example 3 This comparative example provides a surface treatment method for zinc oxide resistor sheets, which adopts a single continuous laser remelting scanning process. The specific steps are similar to those in Example 1, except that step S2 in Example 1 is omitted, while the remaining steps and parameters are the same as in Example 1.

[0046] Comparative Example 4 This comparative example provides a surface treatment method for zinc oxide resistor sheets, which first employs a single continuous laser remelting scanning process, and then employs a pulsed laser scanning process. The specific steps are similar to those in Example 1, except that the order of steps S2 and S3 is changed based on Example 1, while the remaining steps and parameters are the same as in Example 1.

[0047] Comparative Example 5 This comparative example provides a surface treatment method for zinc oxide resistor sheets, which modifies the process parameters of step S2 based on Example 1. The specific steps are similar to those in Example 1, except that the average power in the pulsed laser scanning in step S2 of Example 1 is increased to 25W, while the other parameters remain unchanged.

[0048] Comparative Example 6 This comparative example provides a surface treatment method for zinc oxide resistor sheets, which modifies the process parameters of step S3 based on Example 1. The specific steps are similar to those in Example 1, except that the laser power in the continuous laser remelting scan in step S3 of Example 1 is increased to 250W, while the scanning speed is reduced to 500mm / s, and the other parameters remain unchanged.

[0049] Test Example: Performance Testing of Zinc Oxide Resistor To verify the surface treatment effect and application performance of the zinc oxide resistor sheet of the present invention, key performance tests were conducted on the zinc oxide resistor sheets prepared in Examples 1-2 and Comparative Examples 1-6. Ten parallel samples were prepared for each example or comparative example, and the test results were the arithmetic mean of the ten measurements. Surface roughness was tested using a white light interferometer. Surface micro-defects were imaged at high resolution using a field emission scanning electron microscope (FET) with a magnification of 1000-5000x. Electrode peel strength was tested using a digital adhesion tester according to GB / T 5210-2006 standard: a Φ20mm aluminum test column was bonded, and after the adhesive cured, it was stretched vertically at a rate of 1mm / s. The peel strength was calculated from the ultimate tensile force. Five different locations were selected for testing each sample, and the average value was taken. Square wave current increase rate was tested using a surge generator according to GB / T18802.1-2011 standard: a 2ms square wave current was applied, and the current increase rate was calculated based on the varistor voltage change rate, using Comparative Example 1 as a reference.

[0050] The test results of surface micro-defects of the zinc oxide resistor sheets prepared in Examples 1-2 and Comparative Examples 1-6 are shown in Table 1. The test results of surface roughness, electrode peel strength, and square wave current enhancement rate of the zinc oxide resistor sheets prepared in Examples 1-2 and Comparative Examples 1-6 are shown in Table 2.

[0051] Table 1. Test results of surface micro-defects

[0052] Table 2. Test results of surface roughness, electrode peel strength, and square wave current boost rate.

[0053] As can be seen from Table 1 and Table 2, the surface treatment method provided by the present invention, compared with the mechanical grinding method in Comparative Example 1, that is, the prior art, can comprehensively improve the roughness, microstructure, electrode peel strength and square wave current of the finished product, and significantly improve the key performance of zinc oxide resistor sheets.

[0054] Furthermore, a comparison of Example 1 with Comparative Examples 2 and 3 reveals that Comparative Example 2, which omits the laser remelting step, while achieving a clean surface, fails to heal the microscopic defects left by the pulsed laser, resulting in electrode peel strength and square wave current carrying capacity significantly lower than Example 1. Comparative Example 3, which omits the pulsed laser scanning step, directly remelts the original oxide layer, leading to the inability to expel internal gases from the melt, forming numerous pores, and its performance is even inferior to the mechanically ground wafer of Comparative Example 1. This demonstrates that the pulsed laser cleaning and continuous laser remelting steps of the present invention work synergistically and are indispensable, jointly improving the application stability of the zinc oxide resistor sheet.

[0055] Furthermore, a comparison between Example 1 and Comparative Example 4 reveals that severe peeling and cracking occurred on the surface after the pulsed laser cleaning and continuous laser remelting sequence. This is because the initial continuous laser remelting melts surface contaminants and diffuses them into the substrate, which subsequent pulsed lasers cannot effectively remove. Instead, stress cracks are induced by secondary thermal shock. Consequently, the performance of the resistor sheet obtained in Comparative Example 4 is inferior to that of Example 1, demonstrating that the laser processing technology of this invention has a tightly linked sequence; changing this sequence will lead to surface treatment failure.

[0056] Furthermore, a comparison of Example 1 with Comparative Examples 5 and 6 reveals that excessive power in Comparative Example 5 introduced irreversible thermal damage; excessive heat input in Comparative Example 6 led to abnormal grain growth and thermal stress cracking. This demonstrates that even following the same two-step laser processing sequence, if the laser parameters deviate from the "low-damage cleaning" and "rapid solidification of thin layers" principles of this invention, ideal results cannot be achieved. Therefore, the laser process of this invention is a unique design based on material properties and laser processing effects.

[0057] In summary, the above test results fully verify the superiority of the zinc oxide resistor sheet product obtained by the surface treatment of this invention. This invention employs a two-step composite treatment scheme of first short-pulse laser cleaning and then continuous laser remelting, which not only effectively obtains a dense surface with ultra-low roughness and no damage, but also significantly improves the key performance of the zinc oxide resistor sheet, especially the reliability of the electrode interface and its electrical withstand capability, demonstrating outstanding industrial application value.

[0058] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A surface treatment method for zinc oxide resistive sheets based on laser composite processing, characterized in that, Includes the following steps: S1. The surface to be treated of the sintered zinc oxide resistor sheet blank is subjected to short-pulse laser scanning; the process conditions for short-pulse laser scanning are: wavelength of 1000~1100nm, pulse width of 100~150ns, repetition frequency of 40k~60kHz, laser spot diameter of 40~60μm, scanning line spacing of 30~50μm, scanning speed of 400~600mm / s, and laser power of 5~12W. S2. The surface of the zinc oxide resistor sheet blank after step S1 is subjected to continuous laser remelting scanning to melt and solidify the material within a micrometer-level depth on the surface, thereby forming a laser-modified layer on the surface to be treated; the process conditions of the continuous laser remelting scanning are: wavelength of 1050~1120nm, laser power of 60~100W, spot diameter of 80~120μm, scanning speed of 1200~1800mm / s, and scanning line spacing of 60~100μm; S3. Prepare a metal electrode on the laser-modified layer of the zinc oxide resistor blank to obtain the finished zinc oxide resistor.

2. The surface treatment method for zinc oxide resistive sheets based on laser composite processing according to claim 1, characterized in that, In step S1, the process conditions for the short-pulse laser scanning are as follows: wavelength of 1064nm, pulse width of 120ns, repetition frequency of 50kHz, laser spot diameter of 50μm, scanning line spacing of 40μm, scanning speed of 500mm / s, and laser power of 8W.

3. The surface treatment method for zinc oxide resistive sheets based on laser composite processing according to claim 1, characterized in that, In step S1, after the short-pulse laser scanning, a step of purging with clean air is also included.

4. The surface treatment method for zinc oxide resistive sheets based on laser composite processing according to any one of claims 1 to 3, characterized in that, In step S2, the process conditions for continuous laser remelting scanning are: wavelength of 1080nm, laser power of 80W, spot diameter of 100μm, scanning speed of 1500mm / s, and scanning line spacing of 80μm.

5. The surface treatment method for zinc oxide resistive sheets based on laser composite processing according to any one of claims 1 to 3, characterized in that, In step S2, the micrometer-level depth is 1~50μm.

6. The surface treatment method for zinc oxide resistive sheets based on laser composite processing according to any one of claims 1 to 3, characterized in that, In step S2, the laser beam path of the continuous laser remelting scan is a preset microstructure pattern.

7. The surface treatment method for zinc oxide resistive sheets based on laser composite processing according to claim 6, characterized in that, The microstructure pattern is one or more of the following: a periodically arranged array of pits, a grid, and a groove; the depth of the microstructure pattern is 1~50μm, and the feature size is 10~200μm.

8. The surface treatment method for zinc oxide resistive sheets based on laser composite processing according to any one of claims 1 to 3, characterized in that, The surface roughness Ra of the laser-modified layer is no greater than 1.0 μm.

9. The surface treatment method for zinc oxide resistive sheets based on laser composite processing according to any one of claims 1 to 3, characterized in that, In step S3, before the metal electrode is prepared, the zinc oxide resistor blank is further cleaned and dried; the cleaning is performed by ultrasonic cleaning using deionized water as the medium.

10. A finished zinc oxide resistor sheet obtained by the surface treatment method as described in any one of claims 1 to 9.

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