A method for reducing surface roughness of a gas sensor after flow leveling using ultrasound

Abstract

The application discloses a method for reducing the surface roughness of a gas sensor by using ultrasonic waves, which comprises the following steps: firstly, screen printing insulating paste on an electrode sheet; then, applying ultrasonic waves to the screen-printed electrode sheet by using an ultrasonic transducer, and simultaneously, heating; then, cleaning and sintering; the ultrasonic transducer is controlled by a timing switch to control the switching frequency; the probe of the ultrasonic transducer is arranged at a distance from the electrode sheet and forms an angle with the surface of the electrode sheet. By using ultrasonic waves with a suitable frequency, and the probe with a suitable height and inclination, the paste bubbles can be effectively broken, the surface tension of the liquid can be changed, and the roughness of the electrode sheet surface can be significantly reduced, so that the performance and precision of the gas sensor are improved. The electrical contact between the electrodes can be effectively isolated, so that the risk of short circuit is reduced, and the yield in the manufacturing process is improved. The ultrasonic technology does not directly act on the paste surface, and helps to maintain the original properties and stability of the paste.

Description

Technical Field

[0001] This invention relates to the field of gas sensor technology, and more specifically to a method for reducing the surface roughness of a gas sensor after leveling using ultrasound. Background Technology

[0002] Gas sensors, as terminal nodes of the next-generation Internet of Things (IoT), are widely used in food, chemical, and electronics industries. Common gas sensors are typically manufactured using thick-film screen printing. However, oxygen in the air often adsorbs onto the surface of the sensitive layer of the metal oxide sensor and absorbs electrons, forming O2. - O - O 2- Oxygen ions affect the response of gas sensors. Gas sensors generally have an optimal operating temperature; below or above this temperature, maximum response cannot be achieved. Therefore, to ensure the optimal operating temperature of the gas sensor, a heating electrode needs to be printed on the surface of the gas sensor to provide temperature, and an interdigitated electrode is used to collect resistance changes. However, the two metal electrodes cannot be in direct contact and must be completely insulated. To avoid pattern deformation during the printing of the upper metal layer, complete insulation is required on the metal electrodes, and an insulating paste is used to obtain an insulating film with the lowest possible roughness.

[0003] The key to improving the electrical insulation performance of gas sensors lies in reducing the roughness of the insulation layer. Several methods have been proposed, including rolling the film flat after printing, improving the leveling agent in the paste formulation to enhance the paste's rheological properties, and using polishing techniques to obtain a low-roughness surface. While rolling can achieve a low-roughness surface, it requires changes to equipment and processes and is costly. For example, Chinese Patent CN116278428A discloses a method for reducing film roughness and a screen-printed film. However, its limitation on screen-printed substrates is only to flexible substrates such as PET. For ceramic or silicon substrates commonly used in gas sensors, rolling can easily crush the substrate. Improving the leveling agent in slurry formulations is time-consuming and requires the development of new formulations. For example, Chinese patent CN107915960A discloses an ultra-low surface roughness polyester-based film / composite film and its preparation method. While improving film roughness by doping with surface modifiers, the benzene compounds used have some toxicity, and the chemical reagents used are mostly expensive. Furthermore, the formulation is complex, the process is lengthy, the reaction time is long, and the reaction temperature is high. Polishing techniques, on the other hand, easily introduce polishing particles that form polishing fluid, leading to surface contamination. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a method for reducing the surface roughness of a gas sensor after leveling by using ultrasound. This method can effectively reduce the surface roughness of the gas sensor after leveling and has significant advantages in terms of improving performance, simplifying the process, and reducing costs.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A method for reducing the surface roughness of a gas sensor after leveling using ultrasound includes the following steps: first, screen printing an insulating paste onto an electrode sheet; then, applying ultrasound to the screen-printed electrode sheet using an ultrasonic transducer while simultaneously heating it; followed by cleaning and sintering; wherein the ultrasonic transducer controls the switching frequency via a timer switch; and the distance between the probe of the ultrasonic transducer and the electrode sheet is set such that it forms an angle with the surface of the electrode sheet.

[0007] As a further improvement to the above technical solution:

[0008] The ultrasonic transducer turns on and off within one switching cycle, with the on-time being 3 seconds and the off-time ranging from 10 to 60 seconds.

[0009] The shutdown time is 30 seconds.

[0010] The ultrasonic transducer applies ultrasonic treatment to the screen-printed electrode sheet for 1 hour.

[0011] The heating temperature is 80°C.

[0012] The distance between the probe and the electrode plate is in the range of 5-50mm.

[0013] The distance between the probe and the electrode plate is 20mm.

[0014] The included angle ranges from 0 to 90°.

[0015] The included angle is in the range of 45°.

[0016] Compared with the prior art, the advantages of the present invention are as follows:

[0017] The ultrasonic waves of this invention can effectively break up air bubbles in the slurry and change the surface tension of the liquid. Through these effects, the surface roughness of the electrode sheet can be significantly reduced, thereby improving the performance and accuracy of the gas sensor. Compared with traditional surface treatment methods, such as rolling flattening of films or improving leveling agents in slurry formulations, ultrasonic technology does not require additional equipment and materials, thus simplifying the manufacturing process and reducing production costs.

[0018] Ultrasonic technology effectively isolates electrical contacts between electrodes, thereby reducing the risk of short circuits and improving yield during manufacturing. Since ultrasonic technology does not directly act on the slurry surface, it has minimal impact on the slurry itself, helping to maintain its original properties and stability.

[0019] In summary, using ultrasound at an appropriate frequency and with a probe at an appropriate height and tilt angle can effectively reduce the surface roughness of gas sensors after leveling, offering significant advantages in improving performance, simplifying processes, and reducing costs. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the process for reducing the surface roughness of a gas sensor after leveling using ultrasound.

[0021] Figure 2 This is a flowchart of the ultrasonic roughness improvement experiment.

[0022] Figure 3 For experimental comparison data illustration Figure 1 .

[0023] Figure 4 For experimental comparison data illustration Figure 2 .

[0024] Figure 5 For experimental comparison data illustration Figure 3 .

[0025] Figure 6 For experimental comparison data illustration Figure 4 .

[0026] Figure 7 For experimental comparison data illustration Figure 5 .

[0027] Figure 8 For experimental comparison data illustration Figure 6 . Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] like Figure 1 As shown, the method for reducing the surface roughness of a gas sensor after leveling using ultrasound in this embodiment includes the following steps: first, screen printing an insulating paste on an electrode sheet; then, applying an ultrasonic transducer to the screen-printed electrode sheet while simultaneously heating it; then, cleaning and sintering; the ultrasonic transducer controls the switching frequency through a timer switch; the distance between the probe of the ultrasonic transducer and the electrode sheet is set, and an angle is formed between the probe and the surface of the electrode sheet.

[0030] Ultrasonic technology has been widely used in the electronics manufacturing industry, such as in solid-state bonding, cleaning, ultrasonic bonding, additive manufacturing, and metal welding. Its application in gas sensor manufacturing expands its scope and provides a new solution. Ultrasonic waves can effectively break up air bubbles in slurries and alter the surface tension of the liquid. Through these effects, the surface roughness of the electrode sheet can be significantly reduced, thereby improving the performance and accuracy of the gas sensor. Compared to traditional surface treatment methods, such as rolling to flatten the film or improving the leveling agents in the slurry formulation, ultrasonic technology requires no additional equipment or materials, thus simplifying the manufacturing process and reducing production costs.

[0031] The effectiveness of ultrasonic technology is significantly influenced by the cleaning fluid and various acoustic parameters, including the ultrasonic transducer array, temperature, and frequency. By adjusting these parameters, the effect of ultrasonic action can be flexibly controlled to meet requirements under different conditions. Compared to methods using chemical reagents or toxic substances to improve surface roughness, ultrasonic technology does not introduce harmful substances, which is beneficial to environmental protection and sustainable development, aligning with the environmental protection principles of modern manufacturing. Ultrasonic technology reduces the roughness of the insulating film layer, effectively isolating electrical contacts between electrodes, thereby reducing the risk of short circuits and improving the yield rate in the manufacturing process. This advantage makes the manufacturing process more reliable and stable.

[0032] Simplified Process and Reduced Costs: Using ultrasound to reduce film roughness avoids impurity particles that may be introduced by polishing steps in traditional processes, while also preventing coolant contamination. The application of ultrasound technology simplifies the process, reduces time, and eliminates the need for surface modifiers to improve material formulations, thus lowering manufacturing costs and development cycles. Simple Equipment and Low Costs: The equipment required for ultrasound technology is relatively simple, with low development costs, making this approach more attractive. Since ultrasound is a physical method that does not directly act on the slurry surface, it has minimal impact on the slurry itself, helping to maintain the original properties and stability of the slurry.

[0033] In summary, using ultrasound at an appropriate frequency and with a probe at an appropriate height and tilt angle can effectively reduce the surface roughness of gas sensors after leveling, offering significant advantages in improving performance, simplifying processes, and reducing costs.

[0034] In this embodiment, the ultrasonic transducer is turned on and then off within one switching cycle. The on-time is 3 seconds, and the off-time ranges from 10 to 60 seconds, with 30 seconds being the optimal off-time. By precisely controlling the ultrasonic action time within the switching cycle, it is ensured that the ultrasonic waves fully act on the electrode surface, achieving the best effect in removing bubbles and improving surface roughness. In particular, choosing 30 seconds as the off-time helps ensure that the ultrasonic waves fully affect the slurry surface, further improving the treatment effect. Using a 3-second on-time and a 30-second off-time effectively controls the energy consumption of the ultrasonic waves while ensuring sufficient treatment time, avoiding unnecessary energy waste and improving the efficiency of ultrasonic treatment. The optimal off-time of 30 seconds, obtained through experiments, ensures a relatively stable ultrasonic action cycle, reduces fluctuations in treatment effect caused by insufficient or excessive ultrasonic action time, and guarantees the stability and reliability of the treatment.

[0035] In this embodiment, the ultrasonic transducer applies ultrasonic treatment to the screen-printed electrode sheet for one hour. The prolonged ultrasonic treatment allows for a more thorough impact on the electrode sheet surface, improving its roughness and promoting material flowability, thereby enhancing surface smoothness and quality. The prolonged ultrasonic treatment also helps the material adhere better to the electrode sheet surface, improving adhesion performance and ensuring a strong bond between the material and the electrode sheet. Furthermore, the prolonged ultrasonic treatment allows for the completion of electrode sheet processing in a shorter time, thus improving production efficiency and reducing production time and costs. Finally, the prolonged ultrasonic treatment ensures the stability and consistency of the processing results, reducing quality problems caused by insufficient or uneven processing, and improving product stability and reliability.

[0036] In summary, applying ultrasonic treatment to screen-printed electrode sheets using an ultrasonic transducer for one hour can fully leverage the advantages of ultrasonic technology, thereby improving the surface quality and production efficiency of the electrode sheets and ensuring the stability and reliability of the products.

[0037] In this embodiment, the heating temperature is 80℃. A heating temperature of 80℃ promotes material flowability, allowing the ultrasonic action to more thoroughly affect the electrode surface, further improving surface quality and roughness. The 80℃ heating temperature helps accelerate the material curing process, improving adhesion and stability, and ensuring a strong bond between the material and the electrode. Under 80℃ heating conditions, the ultrasonic action can complete the electrode processing more quickly, thereby shortening processing time and improving production efficiency. A heating temperature of 80℃ maintains a stable temperature during the ultrasonic action process, ensuring the stability and consistency of the processing effect and reducing uneven processing caused by temperature fluctuations. The 80℃ heating temperature is moderate, avoiding excessive thermal stress on the electrode and material, and is suitable for processing most electrode sheets and materials, exhibiting good adaptability.

[0038] In summary, applying ultrasonic treatment to screen-printed electrode sheets for one hour with an ultrasonic transducer and heating them to 80°C can further improve the processing effect, accelerate the curing process, shorten the processing time, maintain stability, and has wide applicability.

[0039] In this embodiment, the distance between the probe and the electrode plate can be 5mm, 10mm, 15mm, 30mm, 40mm, or 50mm. The adjustable range of the distance between the probe and the electrode plate, from 5mm to 50mm, allows for flexible selection of the most suitable distance based on actual conditions and requirements to achieve the best ultrasonic effect. Different distance settings are suitable for electrode plates of different sizes and shapes, as well as different types of materials. This flexibility allows ultrasonic treatment to adapt to various process requirements, thereby improving the applicability and flexibility of the process. By selecting a suitable distance, it can be ensured that the ultrasonic waves can fully act on the surface of the electrode plate to achieve the best treatment effect, thereby improving surface quality and precision. Flexible adjustment of the distance between the probe and the electrode plate not only improves the treatment effect but also helps maintain the stability and consistency of the treatment process, reducing uneven treatment caused by improper spacing. Adjusting the distance between the probe and the electrode plate is relatively simple and easy to operate, requiring no complex equipment or operating procedures, which is beneficial for improving production efficiency and operational convenience.

[0040] In summary, the ultrasonic transducer applies ultrasonic treatment to the screen-printed electrode sheet for 1 hour, and the distance between the probe and the electrode sheet can be 5mm, 10mm, 15mm, 30mm, 40mm, or 50mm. This allows for flexible adaptation to different process requirements, optimization of processing effects, and maintenance of stability and reliability, while also being easy to operate.

[0041] In this embodiment, the included angle can be 0°, 30°, 60°, or 90°. By adjusting the included angle of the ultrasonic transducer, the transmission direction of ultrasonic waves on the electrode surface can be controlled. Different included angles allow ultrasonic waves to enter the material surface at different angles, thereby better influencing the material properties and surface quality. Selecting a suitable included angle ensures that the ultrasonic waves fully act on the electrode surface, achieving the best processing effect. Different included angles can generate different forces and effects during the processing, helping to optimize surface quality and precision. Different included angle settings are suitable for electrode sheets of different shapes and sizes, and the most suitable included angle can be flexibly selected according to actual conditions to achieve the best ultrasonic effect. The included angle is adjustable over a wide range, allowing for flexible selection of the most suitable included angle as needed, thereby increasing operational flexibility and adjustability. By optimizing the transmission direction and effect of ultrasonic waves, processing efficiency and quality can be improved, processing time and costs can be reduced, thereby improving production efficiency and economic benefits.

[0042] In summary, applying ultrasonic treatment to screen-printed electrode sheets for one hour using an ultrasonic transducer, with the included angle being 0°, 30°, 60°, or 90°, can optimize the processing effect, adapt to electrode sheets of different shapes, increase operational flexibility, and improve production efficiency.

[0043] like Figure 2 As shown, the experimental analysis is as follows:

[0044] 1) The effect of ultrasonic transducer switching frequency on the surface roughness of the gas sensor after leveling

[0045] To investigate the effect of switching frequency on surface roughness: A timed switch was used, with cycles of 3 seconds on, 10 seconds, 20 seconds, 30 seconds, and 60 seconds off, for 1 hour. Simultaneously, screen-printed electrode sheets were heated at 80°C using a heating table. Three sheets were taken as a blank control group and leveled at 80°C for one hour without ultrasonic treatment. First, three sheets under each condition were averaged. All ceramic sheets were then ultrasonically cleaned of surface contaminants with alcohol. Afterward, platinum electrode patterns were printed onto the sheets according to the test conditions, and the sheets were sintered at 850°C for 30 minutes. Then, a step meter was used to measure the film thickness and surface roughness before the insulating paste was printed. Next, the insulating paste (DuPont) was printed, and the step data and surface roughness Ra were measured again after the above operations. The effect of ultrasonic time, i.e., switching frequency, on ultrasonic treatment was determined.

[0046] 2) The effect of probe height on the surface roughness of the gas sensor after leveling

[0047] To investigate the effect of probe height on surface roughness, an orthogonal experiment was designed to improve the surface roughness of the insulating film by changing the probe height to 5mm, 10mm, 15mm, 30mm, 40mm, and 50mm from the electrode plate under the condition of optimal switching frequency and leveling at 80 degrees Celsius for 1 hour.

[0048] 3) The effect of probe angle on the surface roughness of the gas sensor after leveling

[0049] To investigate the effect of probe angle on surface roughness, an orthogonal experiment was designed. Under the conditions of optimal switching frequency and optimal probe height, the probe angle was changed to 0°, 30°, 60° and 90° relative to the electrode plate. The improvement of the surface roughness of the insulating film was investigated during the leveling process at 80 degrees Celsius for 1 hour.

[0050] like Figure 3 For experimental comparison data illustration Figure 1 As shown, (a)-(e) are the electrode film thickness data for 3s on, 10s off, 20s, 30s and 60s off using a timer switch (heating before leveling, leveling conditions are 80℃ leveling for 1h, probe distance from ceramic sheet is 5mm and angle is 90°).

[0051] like Figure 4 For experimental comparison data illustration Figure 2 As shown, (a)-(e) represent the effect of changing the switching frequency on the film thickness after leveling; (f) represents the statistics of the average surface roughness.

[0052] like Figure 5 For experimental comparison data illustration Figure 3 As shown, (a) is the electrode film thickness data without ultrasound after leveling at 80℃ for 1 hour; (b)-(g) are the effects of ultrasound on the surface roughness of the film when the probe height is 5mm, 10mm, 15mm, 30mm, 40mm and 50mm respectively (the ultrasound conditions are a probe angle of 90°, a switching frequency of 3s on and 30s off, and leveling at 80℃ for 1 hour).

[0053] like Figure 6 For experimental comparison data illustration Figure 4 As shown, (a)-(h) show the effect of probe heights of 5mm, 10mm, 15mm, 30mm, 40mm, and 50mm on the surface roughness after ultrasound (before the experiment); (i) shows the effect of the change in the height of the ultrasonic probe from the ceramic plate on the average roughness when the ultrasound is turned on for 3 seconds and off for 30 seconds.

[0054] like Figure 7 For experimental comparison data illustration Figure 5As shown, (a) is the effect of leveling at 80℃ for 1 hour without ultrasonication; (b) is the effect of probe angle 0° on roughness before ultrasonic leveling; (c) is the effect of probe angle 30° on roughness before ultrasonic leveling; (d) is the effect of probe angle 45° on roughness before ultrasonic leveling; and (e) is the effect of probe angle 90° on roughness before ultrasonic leveling. (The alumina substrate is 20mm above the probe, and the ultrasonic frequency is cycled for 1 hour with 3s on and 30s off).

[0055] like Figure 8 For experimental comparison data illustration Figure 6 As shown, (a) leveling at 80℃ for 1 hour without ultrasound; (b) the effect of ultrasound on surface roughness when the probe angle is 0°; (c) the effect of ultrasound on surface roughness when the probe angle is 30°; (d) the effect of ultrasound on surface roughness when the probe angle is 45°; and (e) the effect of ultrasound on surface roughness when the probe angle is 90°. (The ultrasound probe operating conditions were: on for 3 seconds, off for 30 seconds, cycle for 1 hour, leveling at 80℃, and the height of the ultrasound probe from the ceramic substrate was 20 mm).

[0056] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and modifications obtained without departing from the inventive concept should also be considered within the scope of protection of the present invention.

Claims

1. A method for reducing the surface roughness of a gas sensor after leveling using ultrasound, characterized in that, Includes the following steps: First, insulating paste is screen-printed onto the electrode sheet. Then, an ultrasonic transducer is used to apply ultrasonic waves to the screen-printed electrode sheet while simultaneously heating it. The process then involves cleaning and sintering. The ultrasonic transducer's switching frequency is controlled by a timer switch. The probe of the ultrasonic transducer is positioned at a distance from the electrode sheet and forms an angle with the surface of the electrode sheet. Within one switching cycle, the ultrasonic transducer first turns on and then off, with an on time of 3 seconds and a off time ranging from 10 to 60 seconds. The heating temperature is 80°C, the distance between the probe and the electrode sheet is 20 mm, and the angle ranges from 45°.

2. The method for reducing the surface roughness of a gas sensor after leveling using ultrasound according to claim 1, characterized in that, The shutdown time is 30 seconds.

3. The method for reducing the surface roughness of a gas sensor after leveling using ultrasound according to claim 1, characterized in that, The ultrasonic transducer applies ultrasonic treatment to the screen-printed electrode sheet for 1 hour.

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