A method for manufacturing a microstructured thin film pressure sensor

Abstract

This invention discloses a method for fabricating a thin-film pressure sensor with a microstructure, belonging to the field of thin-film pressure sensor fabrication technology. It involves customizing the microstructure using a screen printing stencil and combining it with injection molding to form a flexible intermediate layer. Then, an appropriate ink-leaking area is created on the screen printing stencil to complete the transfer of the pressure-sensitive substrate paste. This method overcomes the drawbacks of traditional sandpaper molding, which results in disordered structures and complex photolithography / etching processes. It significantly improves the precision of microstructure forming while allowing for the fabrication of pressure-sensitive elements with different shapes and parameters as needed. This enhances product customization capabilities, broadens the application scenarios, reduces material waste, and compresses production costs. It is also compatible with both small-batch customization and large-scale mass production modes, simultaneously improving production efficiency and yield. Furthermore, by using a flexible material as a transition carrier, combined with an integrated process of vacuum drying and bonding packaging, the overall process is simplified. The entire production process requires no high-precision equipment and can be carried out in an ambient temperature environment, effectively lowering the operational threshold.

Description

Technical Field

[0001] This invention relates to the field of thin-film pressure sensor fabrication technology, and more specifically, to a method for fabricating a thin-film pressure sensor with microstructures. Background Technology

[0002] Flexible thin-film pressure sensors are widely used in human-computer interaction fields such as electronic skin, health monitoring, and bionic skin for robots. The sensor's detection sensitivity and operational stability are mainly determined by the molding quality of the surface microstructure. Current mainstream microstructure fabrication processes all have significant drawbacks: the method of replicating microstructures using sandpaper templates results in disordered structure dimensions and uncontrollable arrangement, leading to poor sensor performance consistency; micro / nano fabrication processes such as photolithography and plasma etching involve large equipment investments, complex procedures, and low processing efficiency, hindering large-scale production; and technologies such as MEMS coating and high-energy beam processing are susceptible to environmental temperature fluctuations, resulting in low thin-film yields and stringent requirements for production equipment. Furthermore, traditional processes generally suffer from insufficient microstructure precision, high manufacturing costs, and weak customization capabilities. Overall, they suffer from poor process stability, difficulty in mass production, and high overall costs.

[0003] Chinese Patent Publication No. CN116718297A discloses a method for fabricating a flexible capacitive pressure sensor with a double-layer microstructure. The method uses a porous hybrid microstructure silicone membrane with random surface structures and a PVA-based hydrogel membrane with random surface structures to prepare the microstructure of the pressure sensor. The advantages of this method are high sensitivity, wide detection range, and excellent linearity. However, its drawbacks are as follows: The method involves mixing sodium chloride (NaCl) and silicone and casting it onto a sandpaper template to obtain a hybrid microstructure silicone mold; then casting a PVA / KOH / KI / glycerol mixed solution onto the sandpaper template and peeling it off at room temperature to obtain a randomly structured hydrogel membrane. The resulting microstructures are formed according to the rough surface of the sandpaper, resulting in limited size and relatively simple and disordered structures. This leads to unstable sensitivity in the pressure sensor. Furthermore, directly applying the silicone membrane or hydrogel to the sandpaper cannot guarantee the uniformity of the membrane, resulting in inaccurate sensitivity to external pressure. Summary of the Invention

[0004] This invention addresses the problems of poor process stability, high mass production difficulty, and high overall cost in the existing microstructure fabrication process of thin-film pressure sensors. It provides a method for fabricating thin-film pressure sensors with microstructures. The method involves customizing the microstructure using a screen printing stencil and combining it with injection molding to form a flexible intermediate layer. Then, an appropriate ink leakage area is created on the screen printing stencil to complete the transfer of the pressure-sensitive substrate paste. This method eliminates the drawbacks of traditional sandpaper molding, which results in disordered structures, and complex photolithography / etching processes. It significantly improves the precision of microstructure forming while allowing for the fabrication of pressure-sensitive elements with different shapes and parameters as needed. This enhances product customization capabilities, broadens the application scenarios, reduces material waste, and compresses production costs. It is also compatible with both small-batch customization and large-scale mass production modes, simultaneously improving production efficiency and yield. Furthermore, by using a flexible material as a transition carrier, combined with an integrated process of vacuum drying and bonding packaging, the overall process is simplified. The entire production process does not require high-precision equipment and can be carried out in an ambient temperature environment, effectively lowering the operational threshold.

[0005] In a first aspect, one technical solution provided in the embodiments of the present invention is: a method for fabricating a thin-film pressure sensor with a microstructure, comprising the following steps: S1. Select flexible raw materials and pre-treat the flexible raw materials according to the preset intermediate layer formula to obtain flexible materials; S2. A base stencil with a microstructure is made using a screen printing stencil. The base stencil is used as a mold to inject flexible material into the base stencil for casting and molding. After cooling and demolding, a flexible intermediate layer with a microstructure is obtained. S3. Create an ink leakage area on the screen printing stencil that matches the shape of the pressure-sensitive element, so that the bottom surface of the screen printing stencil is attached to the surface of the flexible intermediate layer. Select a functional conductive paste as the pressure-sensitive substrate and screen print the pressure-sensitive substrate onto the flexible intermediate layer through the ink leakage area. S4. After vacuum drying the flexible interlayer with the pressure-sensitive substrate attached, the pressure-sensitive substrate is peeled off to obtain the pressure-sensitive element. S5. Select an electrode substrate to fabricate a base layer, configure an electrode layer on the base layer, and bond and encapsulate the pressure-sensitive element, electrode layer, and base layer to obtain a thin-film pressure sensor.

[0006] This solution utilizes a screen printing stencil to customize microstructures and combines this with injection molding to form a flexible intermediate layer. This eliminates the drawbacks of traditional sandpaper molding, which results in disordered structures, and complex photolithography / etching processes. It enables precise fabrication of micron-level regular microstructures, significantly improving microstructure forming accuracy and ensuring consistent performance across different batches. This results in a marked enhancement of sensor sensitivity and operational stability. By creating an appropriate ink leakage area on the screen printing stencil for paste transfer, and flexibly selecting from various functional conductive pastes, pressure-sensitive elements with different shapes and parameters can be manufactured as needed, enhancing product customization capabilities and broadening applicability. Using flexible materials as a transition carrier, combined with an integrated process of vacuum drying and bonding encapsulation, simplifies the overall process. Furthermore, the entire production process requires no high-precision equipment and can operate at room temperature, effectively lowering the operational threshold. By reusing the screen printing stencil and mature screen printing technology, material waste is reduced, production costs are compressed, and both small-batch customization and large-scale mass production modes are compatible. Production efficiency and yield are improved simultaneously, and the use of high-quality materials further extends the sensor's lifespan.

[0007] Preferably, in step S1, a flexible raw material is selected, and the flexible raw material is pretreated according to a preset intermediate layer formula to obtain a flexible material, including the following steps: Using TPE resin as the main material, fillers, plasticizers, antioxidants, heat stabilizers and color masterbatches are used as compound functional additives. The proportion of each material is determined according to the target hardness, elasticity and wear resistance of the intermediate layer. The main material and compound functional additives are mixed and melted, and then transferred to a drying equipment for drying treatment to obtain a flexible material.

[0008] In this solution, TPE resin is selected as the main material, combined with various functional additives to form a compound raw material. The ratio can be precisely adjusted according to the usage requirements, and the hardness, elasticity, and wear resistance of the intermediate layer can be flexibly controlled. Moreover, the raw materials are mixed, melted, and dried to effectively remove moisture, air bubbles, and volatile impurities, thereby avoiding molding defects. At the same time, TPE material has good resilience, high and low temperature resistance, and wear resistance and aging resistance. As an intermediate transition layer, it can accurately replicate micron-level microstructures, thereby ensuring the molding quality of subsequent pressure-sensitive elements and improving the working stability and service life of the sensor from the source.

[0009] Preferably, in step S2, a base stencil with a microstructure is made using a screen printing stencil. The base stencil is then used as a mold to inject flexible material into the stencil for casting. After cooling and demolding, a flexible intermediate layer with a microstructure is obtained. This includes the following steps: A base stencil is obtained by using a screen printing stencil made of polyester fiber or glass fiber and processing microstructures on the stencil using a laser cutting machine or mechanical stamping process. The flexible material is uniformly injected onto the surface of the base mesh until the flexible material covers one side of the base mesh with microstructures. After the substrate mesh is placed in a room temperature environment and allowed to cool, the flexible material is peeled off from the substrate mesh to obtain a flexible intermediate layer with a microstructure.

[0010] In this solution, by selecting screen printing plates made of polyester fiber or glass fiber, and processing microstructures using laser cutting, mechanical stamping, and other processes, regular molds with micron-level precision can be prepared. Furthermore, the structural styles can be designed as needed, offering high customization flexibility. Flexible material is evenly spread across the mold through injection molding, and then demolded after being allowed to cool at room temperature. The overall process is simple, requiring no special working conditions or high-end equipment. This ensures that the microstructure on the surface of the formed flexible intermediate layer is complete and evenly distributed, overcoming the disordered structure defects of traditional sandpaper templates. This guarantees the quality of the semi-finished product from the mold end, laying a solid foundation for the subsequent molding of pressure-sensitive elements and the stable operation of the sensor.

[0011] Preferably, the pattern of the microstructure is pre-designed using drawing software and consists of one or more of circles, rectangles, and triangles arranged in an array.

[0012] In this solution, the microstructure is designed in advance using drawing software, which ensures that the microstructure is structurally regular and accurate when processed by laser cutting, mechanical stamping and other processes. At the same time, the structure style can be customized according to the requirements, which is highly flexible.

[0013] Preferably, in step S3, an ink-discharging area matching the shape of the pressure-sensitive element is formed on the screen printing stencil, so that the bottom surface of the screen printing stencil is bonded to the surface of the flexible intermediate layer. A functional conductive paste is selected as the pressure-sensitive substrate, and the pressure-sensitive substrate is screen-printed onto the flexible intermediate layer through the ink-discharging area, including the following steps: Based on the size and shape of the pressure-sensitive element, corresponding openings are made in the effective printing area of ​​the screen printing stencil as ink leakage areas. The flexible intermediate layer with the microstructure side facing upwards is fixed horizontally on the plane. The screen printing stencil is placed directly above the flexible intermediate layer, and the height of the screen printing stencil is adjusted until the bottom surface of the screen printing stencil is in contact with the surface of the flexible intermediate layer. Select a functional conductive paste as the pressure-sensitive substrate, and apply the pressure-sensitive substrate evenly to one edge of the ink leakage area of ​​the screen printing stencil. A printing squeegee is used to uniformly squeegee the pressure-sensitive substrate until the entire substrate is covered by the ink leakage area.

[0014] In this solution, by creating matching ink leakage areas on the screen printing stencil, the size and shape of the pressure-sensitive element can be precisely defined, thereby meeting the customization needs of products with different specifications. By precisely aligning and tightly bonding the flexible intermediate layer with the screen printing stencil, and then using a squeegee to print at a uniform speed, the conductive paste can be spread evenly, resulting in consistent coating thickness and regular forming. By selecting a functional conductive paste as the pressure-sensitive substrate, the element can be guaranteed to have excellent conductivity and pressure sensing performance. This screen printing method is simple to operate and the process is controllable, which can effectively improve the preparation accuracy of the pressure-sensitive layer and the consistency of the finished product, making it highly suitable for large-scale production.

[0015] Preferably, the mesh count of the screen printing stencil is between 100 and 1000 mesh.

[0016] In this solution, a low number of screen printing stencils can be used to print large-size pressure-sensitive thick films, and a high mesh count can meet the needs of manufacturing miniature high-precision products. This ensures uniform slurry coating and clear pattern outlines, effectively improving the molding quality of pressure-sensitive elements and broadening the application range of the process.

[0017] Preferably, the functional conductive paste includes varistor conductive silver paste and varistor conductive carbon paste; The pressure-sensitive conductive silver paste is a paste in which silver particles are dispersed in an organic solvent; The pressure-sensitive conductive carbon paste is a paste made of carbon black, organic resin and organic solvent.

[0018] In this solution, two types of pastes, silver paste and carbon paste, can be selected as needed: silver paste has excellent conductivity and is suitable for high-precision micro-pressure detection; carbon paste has outstanding stability and is suitable for large-range pressure scenarios; both pastes have good adhesion and film formation effect, which can fully meet the usage requirements of thin-film pressure sensors under different working conditions.

[0019] Preferably, in step S4, after vacuum drying the flexible interlayer with the pressure-sensitive substrate attached, the pressure-sensitive substrate is peeled off to obtain the pressure-sensitive element, including the following steps: A flexible intermediate layer with a pressure-sensitive substrate attached is placed in a vacuum drying oven. The drying temperature, holding time, and vacuum level of the oven are set based on the type of solvent used in the functional conductive paste in the pressure-sensitive paste and the curing characteristics. Wait for the temperature inside the vacuum drying oven to drop to room temperature, remove the flexible intermediate layer with the pressure-sensitive substrate attached, and peel off the cured pressure-sensitive substrate to obtain the pressure-sensitive element with microstructure.

[0020] In this solution, by flexibly setting the vacuum drying parameters according to the solvent type and curing characteristics of the conductive paste, the solvent in the paste can be fully evaporated, thereby achieving uniform curing. After the equipment cools down to room temperature before unloading and peeling, the cracking of the pressure-sensitive layer and the collapse and deformation of the microstructure can be effectively prevented, thus ensuring the integrity and regularity of the replicated micron-level microstructure. Compared with natural air drying, this drying method is more efficient and has better molding stability, which greatly reduces the defect rate and finally obtains a high-quality pressure-sensitive element, providing a reliable guarantee for subsequent sensor packaging and stable use.

[0021] Preferably, in step S5, a substrate is selected to form a base layer, and an electrode layer is disposed on the substrate layer, including the following steps: Using PI film or PET film as the electrode substrate, the electrode substrate is cut to obtain the lower substrate layer based on the size requirements of the thin film pressure sensor, and an upper substrate layer with the same size and shape as the lower substrate layer is cut from the electrode substrate. Using silver paste as the electrode material, a rectangular array of silver electrodes is prepared on the surface of the lower substrate layer by screen printing. After low-temperature drying and curing, the electrode layer is obtained.

[0022] In this solution, PI film and PET film are selected as electrode substrates. Both have excellent mechanical properties, heat resistance and chemical stability, which can improve the environmental adaptability of the sensor. The upper and lower substrate layers are uniformly cut according to the product size to ensure accurate alignment in subsequent packaging. At the same time, the rectangular array silver electrode is prepared by screen printing process combined with low temperature curing, which makes the electrode shape regular and the conductivity stable. The whole operation is simple and easy to implement, which not only ensures the electrical performance of the sensor, but also meets the needs of large-scale production.

[0023] Preferably, in step S5, the pressure-sensitive element, electrode layer, and substrate layer are bonded and encapsulated to obtain a thin-film pressure sensor, including the following steps: The pressure-sensitive element is attached to the working surface of the silver electrode on the electrode layer, and the upper substrate layer is aligned with the lower substrate layer. After alignment, the upper substrate layer is covered on the upper surface of the electrode layer and sealed with the lower substrate layer to obtain the thin film pressure sensor.

[0024] In this solution, by precisely attaching the pressure-sensitive element to the working surface of the silver electrode, full contact between the two can be ensured, allowing the pressure signal to be stably converted into an electrical signal. After aligning the upper and lower base layers and sealing them together, the overall structure is neat and solid, which can isolate moisture and dust from intrusion, thereby effectively protecting the internal functional structure. This packaging method is simple to operate and the finished product has strong integrity, thereby further improving the stability and service life of the sensor.

[0025] The beneficial effects of this invention are as follows: This invention customizes microstructures using a screen printing stencil and combines this with injection molding to form a flexible intermediate layer. Then, an appropriate ink-leaking area is created on the screen printing stencil to complete the transfer of the pressure-sensitive substrate paste. This eliminates the drawbacks of traditional sandpaper molding, which results in disordered structures and complex photolithography / etching processes. It significantly improves the precision of microstructure forming while allowing for the production of pressure-sensitive elements with different shapes and parameters as needed. This enhances product customization capabilities, broadens the application scenarios, reduces material waste, and compresses production costs. It is also compatible with both small-batch customization and large-scale mass production modes, simultaneously improving production efficiency and yield. Furthermore, by using flexible materials as a transition carrier, combined with an integrated process of vacuum drying and bonding packaging, the overall process is simplified. The entire production process requires no high-precision equipment and can be carried out in a normal temperature environment, effectively lowering the operational threshold.

[0026] The above description of the invention is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0027] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. The drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0028] Figure 1 This is a flowchart of a method for fabricating a thin-film pressure sensor with a microstructure according to the present invention; Figure 2 This is a schematic diagram illustrating the operational steps for preparing the flexible intermediate layer according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the flexible intermediate layer in an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the preparatory steps for fabricating a pressure-sensitive element according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the pressure-sensitive element according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the thin-film pressure sensor of the present invention; Figure 7 This is a physical image of the thin-film pressure sensor fabricated in an embodiment of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only one preferred embodiment of this invention and are only used to explain this invention. They do not limit the scope of protection of this invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0030] Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the operations (or steps) as sequential processes, many of the operations (or steps) can be performed in parallel, concurrently, or simultaneously. Furthermore, the order of the operations can be rearranged. The process can be terminated when its operation is completed, but it may also have additional steps not included in the figures; the process may correspond to a method, function, procedure, subroutine, subroutine, etc.

[0031] Example: To address the problems of poor process stability, high mass production difficulty, and high overall cost in the existing microstructure fabrication process of thin-film pressure sensors, this example provides a method for fabricating a thin-film pressure sensor with microstructures, such as... Figure 1 As shown, it includes the following steps: S1: Select flexible raw materials and pre-treat them according to the preset intermediate layer formula to obtain flexible materials.

[0032] In this embodiment, a flexible raw material is selected, and the flexible raw material is pretreated according to a preset intermediate layer formula to obtain a flexible material, including the following steps: Using TPE resin as the main material, fillers, plasticizers, antioxidants, heat stabilizers and color masterbatches are used as compound functional additives. The proportion of each material is determined according to the target hardness, elasticity and wear resistance of the intermediate layer. The main material and compound functional additives are mixed and melted, and then transferred to a drying equipment for drying treatment to obtain a flexible material.

[0033] Specifically, for example, sensors used in conventional applications employ light calcium carbonate as filler, naphthenic oil as plasticizer, and commercially available composite antioxidants and composite heat stabilizers as antioxidants and heat stabilizers. Common black or transparent masterbatches can be used. In high-frequency pressure applications, talc powder with better wear resistance can be used as filler, and naphthenic oil can still be used as plasticizer; the remaining materials can remain unchanged. In high-precision micro-pressure applications, light calcium carbonate can be used as filler, and food-grade white oil as plasticizer. The filler ratio can be reduced, and the plasticizer ratio increased; the remaining materials can remain unchanged. After selecting the materials and ratios, all the prepared materials are added to the mixing equipment at once, and then the equipment is started for continuous mixing until the materials are completely melted, free of visible particles and lumps, and have a uniform overall color. The mixing temperature and mixing time are set according to the actual situation.

[0034] After mixing, a hot air drying machine is used to spread the molten flexible raw material evenly in the drying machine tray. The thickness is made uniform during spreading. Then the door is closed and the drying machine is started. After drying, a semi-molten flexible material is obtained.

[0035] This embodiment uses TPE resin as the main material, combined with various functional additives to form a compound raw material. The ratio can be precisely adjusted according to the usage requirements, and the hardness, elasticity, and wear resistance of the intermediate layer can be flexibly controlled. Moreover, the raw materials are mixed, melted, and dried to effectively remove moisture, air bubbles, and volatile impurities, thereby avoiding molding defects. At the same time, TPE material has good resilience, high and low temperature resistance, and wear resistance and aging resistance. As an intermediate transition layer, it can accurately replicate micron-level microstructures, thereby ensuring the molding quality of subsequent pressure-sensitive elements and improving the working stability and service life of the sensor from the source.

[0036] S2: A base stencil with a microstructure is made using a screen printing stencil. The base stencil is used as a mold to inject flexible material into the base stencil for casting and molding. After cooling and demolding, a flexible intermediate layer with a microstructure is obtained.

[0037] In this embodiment, a microstructured base stencil is fabricated using a screen printing stencil. The base stencil is then used as a mold to inject flexible material into the stencil for casting. After cooling and demolding, a flexible intermediate layer with a microstructure is obtained. The process includes the following steps: A base stencil is obtained by using a screen printing stencil made of polyester fiber or glass fiber and processing microstructures on the stencil using a laser cutting machine or mechanical stamping process. The flexible material is uniformly injected onto the surface of the base mesh until the flexible material covers one side of the base mesh with microstructures. After the substrate mesh is placed in a room temperature environment and allowed to cool, the flexible material is peeled off from the substrate mesh to obtain a flexible intermediate layer with a microstructure.

[0038] Specifically, the microstructure design and processing of the base mesh is carried out first. The microstructure pattern is designed using CAD software, and the array arrangement can be rectangular, circular, triangular, etc. The microstructure size is designed to be at the micrometer level. Then, the design file is imported into a laser cutting machine / mechanical stamping machine to process the concave and convex microstructures on the mesh. After processing, visual inspection is performed to confirm that there are no defects such as breaks, defects, or burrs in the microstructure. Then, the processed mesh is immersed in a clean water washing tank, and the front and back of the mesh are thoroughly brushed with a soft brush to remove processing debris. Then, a high-pressure water gun is used to spray and rinse the entire area to clean the gaps and remove any remaining impurities. Then, anhydrous ethanol is used to wet a lint-free cloth and wipe the front and back of the mesh a second time to remove oil and water stains. After that, the mesh is hung vertically and allowed to air dry completely in a clean environment at room temperature to obtain the base mesh.

[0039] like Figure 2 As shown, the dried and qualified base stencil is fixed in the injection molding fixture. It is necessary to ensure that the stencil is horizontal and without warping. The semi-molten flexible material is evenly poured onto the side of the stencil with microstructure. During pouring, the feeding speed needs to be controlled so that the material completely covers the effective area of ​​the stencil, ensuring no missing material and no large-area overflow.

[0040] After casting, the tooling and material are allowed to cool naturally at room temperature until the flexible material is completely hardened and set. Once set, the flexible intermediate layer is slowly peeled off along the edge of the stencil. Care must be taken to prevent the microstructure of the replica stencil from being pulled and damaged during peeling. After peeling, a flexible intermediate layer with a surface replicating the microstructure of the base stencil is obtained, as shown in the diagram. Figure 3 As shown.

[0041] This embodiment utilizes screen printing stencils made of polyester or glass fiber, combined with laser cutting and mechanical stamping processes to fabricate microstructures. This allows for the production of well-formed molds with micron-level precision, and also enables the design of customizable structural styles, offering high flexibility. The flexible material is evenly distributed across the mold through injection molding, followed by demolding after cooling at room temperature. The overall process is simple, requiring no special working conditions or high-end equipment. This results in a complete and uniformly distributed microstructure on the surface of the formed flexible intermediate layer, overcoming the disordered structure defects of traditional sandpaper templates. This ensures the quality of the semi-finished product from the mold end, laying a solid foundation for the subsequent molding of pressure-sensitive elements and the stable operation of the sensor.

[0042] In this embodiment, the pattern of the microstructure is pre-designed using drawing software and consists of one or more of the following: circles, rectangles, and triangles, arranged in an array.

[0043] This embodiment designs the microstructure in advance using drawing software, ensuring that the microstructure is structurally regular and accurate when subsequently processed by laser cutting, mechanical stamping and other processes. At the same time, the structure style can be customized according to the requirements, which is highly flexible.

[0044] S3: Create an ink leakage area on the screen printing stencil that matches the shape of the pressure-sensitive element, so that the bottom surface of the screen printing stencil is attached to the surface of the flexible intermediate layer. Select a functional conductive paste as the pressure-sensitive substrate and screen print the pressure-sensitive substrate onto the flexible intermediate layer through the ink leakage area.

[0045] In this embodiment, an ink-discharging area matching the shape of the pressure-sensitive element is formed on the screen printing stencil, so that the bottom surface of the screen printing stencil is attached to the surface of the flexible intermediate layer. A functional conductive paste is selected as the pressure-sensitive substrate, and the pressure-sensitive substrate is screen-printed onto the flexible intermediate layer through the ink-discharging area. The process includes the following steps: Based on the size and shape of the pressure-sensitive element, corresponding openings are made in the effective printing area of ​​the screen printing stencil as ink leakage areas. The flexible intermediate layer with the microstructure side facing upwards is fixed horizontally on the plane. The screen printing stencil is placed directly above the flexible intermediate layer, and the height of the screen printing stencil is adjusted until the bottom surface of the screen printing stencil is in contact with the surface of the flexible intermediate layer. Select a functional conductive paste as the pressure-sensitive substrate, and apply the pressure-sensitive substrate evenly to one edge of the ink leakage area of ​​the screen printing stencil. A printing squeegee is used to uniformly squeegee the pressure-sensitive substrate until the entire substrate is covered by the ink leakage area.

[0046] Specifically, before fabricating the pressure-sensitive element, it is necessary to select the pressure-sensitive substrate. Commonly used pressure-sensitive substrates include general conductive paste, carbon paste, and silver paste. General conductive paste is a paste made of conductive microparticles and organic solvents. It has strong adhesion and dries quickly, making it suitable for general-purpose thin-film pressure sensors under normal working conditions. Carbon paste is mainly composed of carbon black, resin, and solvent. It has high resistivity and strong stability, making it suitable for detection scenarios with large pressure ranges. Silver paste is mainly composed of silver microparticles and organic solvents. It has low resistivity and high conductivity sensitivity, making it suitable for micro-pressure and high-precision detection scenarios. In this embodiment, silver paste is preferred as the functional conductive paste. Before use, the paste needs to be stirred evenly. After stirring, it should be left to stand for a period of time until the bubbles that appeared during stirring disappear to obtain the pressure-sensitive substrate.

[0047] Choose a screen printing stencil with a mesh size of 100 to 1000. The higher the mesh number, the higher the printing precision of the pressure-sensitive layer and the thinner the film. Low mesh numbers are suitable for manufacturing large-size, thick-film printed pressure-sensitive elements, while high mesh numbers are suitable for miniature and high-precision pressure-sensitive elements. After determining the shape and size of the required pressure-sensitive element, open ink leakage holes of corresponding shape and size in the effective printing area of ​​the screen printing stencil as ink leakage areas, and grind the edges of the ink leakage holes to prevent material from sticking and clogging.

[0048] After the ink leakage area is set up, as follows Figure 4As shown, the flexible interlayer is horizontally fixed on the printing table, ensuring the side with the microstructure faces upwards. The prepared screen printing stencil is then placed directly above the flexible interlayer. The stencil's height and level are adjusted to ensure a tight fit between the bottom surface of the stencil and the surface of the flexible interlayer, preventing any gaps or warping and ensuring uniform printing gaps throughout the process. Next, pressure-sensitive substrate is evenly applied to one edge of the ink-leaking area on the screen printing stencil. The amount applied should be sufficient to cover the entire ink-leaking area in a single print, preventing excessive overflow of the pressure-sensitive substrate into ineffective areas of the flexible interlayer.

[0049] For screen printing, manual squeegee printing or fully automatic screen printing machine printing can be used. Manual squeegee printing is suitable for small-batch sample production with a large variety of products. Specifically, the operator holds a special screen printing squeegee, keeps the squeegee tilt angle stable throughout the process, and scrapes the entire ink leakage area from one side of the pressure-sensitive substrate to the other in one go at a uniform speed. After squeegee printing is completed, the screen printing plate is lifted vertically upwards. Fully automatic screen printing machine printing is suitable for mass production scenarios. Specifically, the downward pressure of the squeegee, the travel speed of the squeegee, and the lifting height of the screen plate are set in advance in the equipment system. After the settings are completed, the equipment is started, and the screen printing machine automatically completes the entire process of screen placement, material spreading, squeegee printing, and screen lifting.

[0050] This embodiment precisely defines the size and shape of the pressure-sensitive element by creating matching ink leakage areas on the screen printing stencil, thereby meeting the customization needs of products with different specifications. By precisely aligning and tightly bonding the flexible intermediate layer with the screen printing stencil, and then using a squeegee to print at a uniform speed, the conductive paste can be spread evenly, resulting in consistent coating thickness and regular forming. By selecting a functional conductive paste as the pressure-sensitive substrate, the element can be guaranteed to have excellent conductivity and pressure sensing performance. This screen printing method is simple to operate and the process is controllable, which can effectively improve the preparation accuracy of the pressure-sensitive layer and the consistency of the finished product, making it highly suitable for large-scale production.

[0051] In this embodiment, the mesh count of the screen printing stencil is between 100 and 1000 mesh.

[0052] This embodiment uses a low number of screen printing stencils to adapt to the printing of large-size pressure-sensitive thick films. The high mesh count meets the requirements for the production of miniature high-precision products, ensuring uniform paste coating and clear pattern outlines, effectively improving the molding quality of pressure-sensitive elements and broadening the application range of the process.

[0053] In this embodiment, the functional conductive paste includes varistor conductive silver paste and varistor conductive carbon paste; The pressure-sensitive conductive silver paste is a paste in which silver particles are dispersed in an organic solvent; The pressure-sensitive conductive carbon paste is a paste made of carbon black, organic resin and organic solvent.

[0054] This embodiment allows for the selection of two types of pastes, silver paste and carbon paste, as needed: silver paste has excellent conductivity and is suitable for high-precision micro-pressure detection; carbon paste has outstanding stability and is suitable for large-range pressure scenarios; both pastes have good adhesion and film formation effect, which can fully meet the usage requirements of thin-film pressure sensors under different working conditions.

[0055] S4: After vacuum drying the flexible interlayer with the pressure-sensitive substrate attached, the pressure-sensitive substrate is peeled off to obtain the pressure-sensitive element.

[0056] In this embodiment, the pressure-sensitive element is obtained by vacuum drying the flexible interlayer with the pressure-sensitive substrate attached and then peeling off the pressure-sensitive substrate. The process includes the following steps: A flexible intermediate layer with a pressure-sensitive substrate attached is placed in a vacuum drying oven. The drying temperature, holding time, and vacuum level of the oven are set based on the type of solvent used in the functional conductive paste in the pressure-sensitive paste and the curing characteristics. Wait for the temperature inside the vacuum drying oven to drop to room temperature, remove the flexible intermediate layer with the pressure-sensitive substrate attached, and peel off the cured pressure-sensitive substrate to obtain the pressure-sensitive element with microstructure.

[0057] Specifically, after the printing process is completed, the flexible intermediate layer with the pressure-sensitive substrate attached is placed smoothly onto the rack of the vacuum drying oven. Then, drying parameters are set according to the type of pressure-sensitive substrate, and vacuum drying is performed. Since silver paste is used in this embodiment, the temperature can be set to 50-70 degrees Celsius, the vacuum degree to -0.08 to -0.06 MPa, and the drying time to approximately 1-2.5 hours. This accelerates solvent evaporation while preventing oxidation of the pressure-sensitive substrate surface and thus preventing the failure of the pressure-sensitive substrate's conductivity.

[0058] After drying, stop vacuuming and allow the chamber to cool naturally to room temperature before opening the door and removing the workpiece. Slowly peel the fully cured pressure-sensitive element from the surface of the flexible interlayer. The resulting pressure-sensitive element is shown below. Figure 5 As shown, random sampling of the obtained pressure-sensitive elements was performed, and the surface microstructure of the pressure-sensitive elements was observed using a micron-level optical microscope. The screening criteria were: the microstructure was complete without collapse, damage, bubbles, or holes, and the shape and size of the replicated microstructure array were consistent with the flexible intermediate layer. At the same time, the pressure-sensitive substrate film was continuous without film breaks or material shortages. Products that met the standards were judged to be qualified.

[0059] This embodiment flexibly sets vacuum drying parameters based on the solvent type and curing characteristics of the conductive paste, allowing the paste solvent to fully evaporate and achieve uniform curing. Discharging and peeling the material after the equipment cools to room temperature effectively prevents cracking of the pressure-sensitive layer and collapse or deformation of the microstructure, ensuring the integrity and regularity of the replicated micron-level microstructure. This drying method is more efficient and provides better molding stability than natural air drying, significantly reducing the defect rate and ultimately yielding high-quality pressure-sensitive elements, providing a reliable guarantee for subsequent sensor packaging and stable use.

[0060] S5: Select an electrode substrate to make a base layer, configure an electrode layer on the base layer, and bond and encapsulate the pressure-sensitive element, electrode layer and base layer to obtain a thin-film pressure sensor.

[0061] In this embodiment, an electrode substrate is selected to fabricate a base layer, and an electrode layer is disposed on the base layer, including the following steps: Using PI film or PET film as the electrode substrate, the electrode substrate is cut to obtain the lower substrate layer based on the size requirements of the thin film pressure sensor, and an upper substrate layer with the same size and shape as the lower substrate layer is cut from the electrode substrate. Using conductive silver paste as the electrode material, a rectangular array of silver electrodes is prepared on the surface of the lower substrate layer by screen printing. After low-temperature drying and curing, the electrode layer is obtained.

[0062] Specifically, PI film is the mainstream and commonly used choice, with a thickness range of 0.0125mm to 0.25mm. 0.1mm to 0.125mm is commonly used in mass production. It has excellent heat resistance, mechanical properties, chemical stability, and dielectric properties. If higher tensile strength and smoothness are required for the sensor, PET film can also be selected as the base layer. During cutting, the film is precisely cut according to the shape and size of the finished sensor and the burrs are removed using cutting equipment.

[0063] When fabricating the electrode layer, conductive silver paste is used as the electrode material. The main components of this conductive silver paste include silver powder (over 50%), organic binder resin, organic solvents, and functional additives. Compared to the varistor-sensitive conductive silver paste mentioned earlier, the conductive silver paste has larger silver powder particle size and a higher proportion of resin binder phase. The conductive pathway is mainly composed of continuous silver powder overlap, making it more suitable for low-resistance and stable electrode circuit scenarios. Rectangular array silver electrodes can be printed using screen printing, electroplating, or photolithography etching processes, depending on the production requirements. After printing, the electrode layer is obtained by low-temperature drying and curing.

[0064] This embodiment selects PI film and PET film as electrode substrates, both of which have excellent mechanical properties, heat resistance and chemical stability, which can improve the sensor's environmental adaptability. The upper and lower substrate layers are uniformly cut according to the product size, which can ensure accurate alignment in subsequent packaging. At the same time, the rectangular array silver electrode is prepared by screen printing process combined with low temperature curing, which makes the electrode shape regular and the conductivity stable. The whole operation is simple and easy to implement, which not only ensures the electrical performance of the sensor, but also meets the needs of large-scale production.

[0065] In this embodiment, a thin-film pressure sensor is obtained by bonding and encapsulating a pressure-sensitive element, an electrode layer, and a substrate layer, including the following steps: The pressure-sensitive element is attached to the working surface of the silver electrode on the electrode layer, and the upper substrate layer is aligned with the lower substrate layer. After alignment, the upper substrate layer is covered on the upper surface of the electrode layer and sealed with the lower substrate layer to obtain the thin film pressure sensor.

[0066] Specifically, the pressure-sensitive element is precisely aligned and bonded to the working surface of the silver electrode. The pattern of the pressure-sensitive layer can be designed as circular, square, strip, star, etc., as needed. After alignment, a sealing and bonding encapsulation process is used. The electrode layer and pressure-sensitive element are integrally sealed and composited using upper and lower substrate layers to obtain a thin-film pressure sensor. The specific structure is as follows: Figure 6 As shown.

[0067] In this embodiment, by precisely attaching the pressure-sensitive element to the working surface of the silver electrode, full contact between the two can be ensured, allowing the pressure signal to be stably converted into an electrical signal. After aligning the upper and lower base layers and sealing them together, the overall structure is neat and solid, which can isolate moisture and dust from intrusion, thereby effectively protecting the internal functional structure. This packaging method is simple to operate and the finished product has strong integrity, thereby further improving the stability and service life of the sensor.

[0068] like Figure 7 The image shown is a physical diagram of the thin-film pressure sensor obtained according to the manufacturing process of this embodiment.

[0069] As can be seen from the above embodiments, it has at least the following substantial effects: (1) This invention uses screen printing stencils to customize microstructures and combines injection molding to form a flexible intermediate layer. It eliminates the drawbacks of disordered structure and complex photolithography / etching processes in traditional sandpaper molding. It can accurately prepare micron-level regular microstructures, greatly improve the microstructure forming accuracy, ensure the uniformity of performance of different batches of products, and significantly enhance the sensor sensitivity and working stability. (2) This invention completes the transfer of paste by opening an appropriate ink leakage area on the screen printing plate. It can be flexibly selected with a variety of functional conductive pastes, and pressure-sensitive elements with different shapes and parameters can be made as needed. The product customization capability is stronger and the applicable scenarios are wider. (3) The present invention uses flexible materials as a transition carrier, combined with an integrated process of vacuum drying and bonding packaging, which simplifies the overall process. At the same time, the entire production process does not require high-end precision equipment and can be carried out in a normal temperature environment, which effectively reduces the operating threshold. (4) By reusing the screen printing stencil and mature screen printing process, this invention not only reduces material loss and compresses production costs, but also is compatible with small-batch customization and large-batch mass production modes, improving production efficiency and yield simultaneously. At the same time, relying on high-quality materials, it also further extends the service life of the sensor.

[0070] The specific embodiments described above are preferred embodiments of the present invention and are not intended to limit the specific scope of the present invention. The scope of the present invention includes, but is not limited to, these specific embodiments. All equivalent changes made in accordance with the shape and structure of the present invention are within the protection scope of the present invention.

Claims

1. A method for fabricating a thin-film pressure sensor with a microstructure, characterized in that: Includes the following steps: S1. Select flexible raw materials and pre-treat the flexible raw materials according to the preset intermediate layer formula to obtain flexible materials; S2. A base stencil with a microstructure is made using a screen printing stencil. The base stencil is used as a mold to inject flexible material into the base stencil for casting and molding. After cooling and demolding, a flexible intermediate layer with a microstructure is obtained. S3. Create an ink leakage area on the screen printing stencil that matches the shape of the pressure-sensitive element, so that the bottom surface of the screen printing stencil is attached to the surface of the flexible intermediate layer. Select a functional conductive paste as the pressure-sensitive substrate and screen print the pressure-sensitive substrate onto the flexible intermediate layer through the ink leakage area. S4. After vacuum drying the flexible interlayer with the pressure-sensitive substrate attached, the pressure-sensitive substrate is peeled off to obtain the pressure-sensitive element. S5. Select an electrode substrate to fabricate a base layer, configure an electrode layer on the base layer, and bond and encapsulate the pressure-sensitive element, electrode layer, and base layer to obtain a thin-film pressure sensor.

2. The method for fabricating a thin-film pressure sensor with a microstructure according to claim 1, characterized in that: In S1, a flexible raw material is selected, and the flexible raw material is pretreated according to a preset intermediate layer formula to obtain a flexible material, including the following steps: Using TPE resin as the main material, fillers, plasticizers, antioxidants, heat stabilizers and color masterbatches are used as compound functional additives. The proportion of each material is determined according to the target hardness, elasticity and wear resistance of the intermediate layer. The main material and compound functional additives are mixed and melted, and then transferred to a drying equipment for drying treatment to obtain a flexible material.

3. The method for fabricating a thin-film pressure sensor with a microstructure according to claim 1, characterized in that: In S2, a base stencil with a microstructure is made using a screen printing stencil. Using the base stencil as a mold, flexible material is injected into the base stencil to form a mold. After cooling and demolding, a flexible intermediate layer with a microstructure is obtained. This process includes the following steps: A base stencil is obtained by using a screen printing stencil made of polyester fiber or glass fiber and processing microstructures on the stencil using a laser cutting machine or mechanical stamping process. The flexible material is uniformly injected onto the surface of the base mesh until the flexible material covers one side of the base mesh with microstructures. After the substrate mesh is placed in a room temperature environment and allowed to cool, the flexible material is peeled off from the substrate mesh to obtain a flexible intermediate layer with a microstructure.

4. The method for fabricating a thin-film pressure sensor with a microstructure according to claim 3, characterized in that: The microstructure pattern is pre-designed using drawing software and consists of one or more of the following: circles, rectangles, and triangles, arranged in an array.

5. The method for fabricating a thin-film pressure sensor with a microstructure according to claim 1, characterized in that: In step S3, an ink-discharging area matching the shape of the pressure-sensitive element is created on the screen printing stencil, so that the bottom surface of the screen printing stencil is attached to the surface of the flexible intermediate layer. A functional conductive paste is selected as the pressure-sensitive substrate, and the pressure-sensitive substrate is screen-printed onto the flexible intermediate layer through the ink-discharging area. This includes the following steps: Based on the size and shape of the pressure-sensitive element, corresponding openings are made in the effective printing area of ​​the screen printing stencil as ink leakage areas. The flexible intermediate layer with the microstructure side facing upwards is fixed horizontally on the plane. The screen printing stencil is placed directly above the flexible intermediate layer, and the height of the screen printing stencil is adjusted until the bottom surface of the screen printing stencil is in contact with the surface of the flexible intermediate layer. Select a functional conductive paste as the pressure-sensitive substrate, and apply the pressure-sensitive substrate evenly to one edge of the ink leakage area of ​​the screen printing stencil. A printing squeegee is used to uniformly squeegee the pressure-sensitive substrate until the entire substrate is covered by the ink leakage area.

6. The method for fabricating a thin-film pressure sensor with a microstructure according to claim 5, characterized in that: The mesh count of the screen printing stencil is between 100 and 1000 mesh.

7. The method for fabricating a thin-film pressure sensor with a microstructure according to claim 5, characterized in that: The functional conductive paste includes varistor conductive silver paste and varistor conductive carbon paste; The pressure-sensitive conductive silver paste is a paste in which silver particles are dispersed in an organic solvent; The pressure-sensitive conductive carbon paste is a paste made of carbon black, organic resin and organic solvent.

8. The method for fabricating a thin-film pressure sensor with a microstructure according to claim 1, characterized in that: In step S4, the flexible interlayer with the pressure-sensitive substrate attached is vacuum dried, and then the pressure-sensitive substrate is peeled off to obtain the pressure-sensitive element. This includes the following steps: A flexible intermediate layer with a pressure-sensitive substrate attached is placed in a vacuum drying oven. The drying temperature, holding time, and vacuum level of the oven are set based on the type of solvent used in the functional conductive paste in the pressure-sensitive paste and the curing characteristics. Wait for the temperature inside the vacuum drying oven to drop to room temperature, remove the flexible intermediate layer with the pressure-sensitive substrate attached, and peel off the cured pressure-sensitive substrate to obtain the pressure-sensitive element with microstructure.

9. The method for fabricating a thin-film pressure sensor with a microstructure according to claim 1, characterized in that: In step S5, an electrode substrate is selected to fabricate a base layer, and an electrode layer is disposed on the base layer, including the following steps: Using PI film or PET film as the electrode substrate, the electrode substrate is cut to obtain the lower substrate layer based on the size requirements of the thin film pressure sensor, and an upper substrate layer with the same size and shape as the lower substrate layer is cut from the electrode substrate. Using conductive silver paste as the electrode material, a rectangular array of silver electrodes is prepared on the surface of the lower substrate layer by screen printing. After low-temperature drying and curing, the electrode layer is obtained.

10. The method for fabricating a thin-film pressure sensor with a microstructure according to claim 9, characterized in that: In step S5, the pressure-sensitive element, electrode layer, and substrate layer are bonded and encapsulated to obtain a thin-film pressure sensor, including the following steps: The pressure-sensitive element is attached to the working surface of the silver electrode on the electrode layer, and the upper substrate layer is aligned with the lower substrate layer. After alignment, the upper substrate layer is covered on the upper surface of the electrode layer and sealed with the lower substrate layer to obtain the thin film pressure sensor.

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