Pressure sensor structure based on chemical copper deposition process and preparation method thereof

Abstract

The invention discloses a pressure sensor structure based on a chemical copper deposition process and a preparation method thereof, and belongs to the technical field of flexible pressure sensors, and the pressure sensor structure comprises an upper copper-plated electrode, an upper support film, a pressure-sensitive film, a lower support film and a lower copper-plated electrode which are sequentially stacked from top to bottom; wherein after a mixed material of the upper supporting film and the lower supporting film is cured and formed, an electrode pattern is obtained by utilizing ultraviolet laser etching, then an upper copper-plated electrode and a lower copper-plated electrode are prepared through a chemical copper plating process, and finally, the upper supporting film and the lower supporting film are attached to the upper surface and the lower surface of the pressure-sensitive film by utilizing an adhesive. According to the invention, by combining ultraviolet laser etching and chemical copper plating processes, an electrode with strong adhesive force is formed on the surface of the support film, and then by using the high-molecular polymer characteristics of the support film and the pressure-sensitive film, tight connection between the electrode and the pressure-sensitive film is realized, and the conductivity is improved; the sensitivity, the response speed and the service life of the pressure sensor structure are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible pressure sensors, and particularly relates to a pressure sensor structure based on a chemical copper deposition process and a preparation method thereof. Background Art

[0002] Flexible piezoresistive pressure sensors are a type of sensing device that utilizes flexible materials and realizes pressure-resistance conversion based on the piezoresistive effect. Their core advantages lie in their high sensitivity, wide detection range, excellent mechanical flexibility, and environmental adaptability, and they have important application values in the fields of wearable electronics, health monitoring, human-computer interaction, and intelligent robots. With the development of materials science, micro-nano manufacturing, and information technology, their performance and application scope will be further improved, providing core technical support for the next generation of intelligent devices.

[0003] Currently, the preparation of piezoresistive thin films generally includes the following key steps: First, the active material is uniformly mixed into the flexible matrix to form a high-performance composite material; subsequently, the electrodes are transferred through a transfer technology to ensure efficient signal transmission; finally, a flexible material is used for encapsulation to improve the stability and durability of the sensor. However, traditional transfer technologies face many challenges in the manufacturing of flexible electronic devices. For example, problems such as weak interfacial bonding force between metals and polymer films, uneven stress distribution during the welding process, and uneven material strain often lead to unstable electrode performance, and even damage the device, affecting its long-term reliability and service life. In contrast, electroless plating technology shows great advantages in the field of flexible electronics manufacturing due to its excellent process characteristics. Electroless plating can form a uniform, continuous, and highly stable conductive layer on the surface of the flexible substrate, ensuring excellent conductivity, and can arbitrarily form various electrode patterns with the help of laser direct writing technology. In addition, the electroless plating process does not require high-temperature or high-pressure treatment, which can effectively reduce the thermal damage to the substrate and improve the overall flexibility and durability of the device. Especially in the applications of flexible electronics and wearable devices, electroless plating provides stronger electrode adhesion, significantly improving the bonding strength between the electrode and the substrate, thereby reducing the risk of peeling, cracking, or falling off during use. These characteristics make the electroless plating technology a very promising electrode preparation method in the field of flexible electronics, providing a solid technical guarantee for high-performance and long-life flexible pressure sensors and intelligent devices.

[0004] Therefore, developing a preparation method for pressure sensors based on the chemical copper deposition process is of great significance for practical applications. Summary of the Invention

[0005] Aiming at the problem that the connection between the electrode and the pressure-sensitive film is not tight when preparing the electrode by traditional transfer technology, the present invention provides a pressure sensor structure based on the electroless copper plating process and its preparation method. By combining ultraviolet laser etching and electroless copper plating processes, electrodes with strong adhesion are formed on the surface of the support film, and then, by utilizing the polymer characteristics of the support film and the pressure-sensitive film, a tight connection between the electrode and the pressure-sensitive film is achieved, thereby realizing more accurate and efficient pressure detection.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A pressure sensor structure based on the electroless copper plating process, comprising an upper copper-plated electrode, an upper support film, a pressure-sensitive film, a lower support film, and a lower copper-plated electrode stacked in sequence from top to bottom; wherein, the upper copper-plated electrode and the lower copper-plated electrode are prepared by the electroless copper plating process, and the arrangement directions of the electrode patterns of the two are perpendicular to each other, forming an island-bridge structure; the materials of the upper support film and the lower support film are mixed materials composed of a polymer, a conductive material, and antimony tin oxide (ATO).

[0008] Further, both the upper copper-plated electrode and the lower copper-plated electrode include a plurality of electrode units arranged in a periodic array, and the same-direction electrode units are connected by serpentine electrodes, and the connection direction of the serpentine electrodes of the upper copper-plated electrode is perpendicular to the connection direction of the serpentine electrodes of the lower copper-plated electrode.

[0009] Further, the polymer is polydimethylsiloxane (PDMS) or silicone rubber (Ecoflex), and the conductive material is multi-walled carbon nanotubes (CNT) or carbon black.

[0010] Further, in the upper support film and the lower support film, the mass ratio of the polymer, the conductive material, and antimony tin oxide is 100:3-4:5-6.

[0011] Further, the thickness of the upper copper-plated electrode and the lower copper-plated electrode is 100-200 μm, the thickness of the upper support film and the lower support film is 200-300 μm, and the thickness of the pressure-sensitive film is 0.8-1.2 mm.

[0012] A preparation method of a pressure sensor structure based on the electroless copper plating process, comprising the following steps:

[0013] Step 1: Vacuum stir and mix the polymer, the conductive material, and antimony tin oxide, spin coat and then heat and cure to form the upper support film and the lower support film;

[0014] Step 2: Use ultraviolet laser etching to obtain corresponding electrode patterns on the surfaces of the upper support film and the lower support film, and activate surface active particles;

[0015] Step 3: Prepare the electroless copper plating solution. Immerse the etched upper support film and lower support film in the electroless copper plating solution under a vacuum environment. After standing in a vacuum drying oven for a period of time, obtain the upper copper plating electrode deposited on the surface of the upper support film and the lower copper plating electrode deposited on the surface of the lower support film;

[0016] Step 4: Prepare the pressure-sensitive film by the template method;

[0017] Step 5: Prepare the adhesive. Use the adhesive to bond the upper support film and the lower support film to the upper and lower surfaces of the pressure-sensitive film respectively, ensuring that the electrode pattern arrangement directions of the upper copper plating electrode and the lower copper plating electrode are perpendicular to each other. After heating and curing, obtain the pressure sensor structure based on the electroless copper plating process.

[0018] Further, in Step 1, the temperature for heating and curing is 120 - 150 °C, and the duration is 3 - 5 min.

[0019] Further, in Step 1, the specific process of vacuum stirring and mixing is as follows: First, ultrasonic for 30 - 40 min, and then stir in a vacuum mixer for 1 - 2 min; the rotation speed for spin coating is 450 - 550 rpm, and the duration is 1 - 2 min.

[0020] Further, in Step 2, the speed of the ultraviolet laser is 1500 - 2000 mm / s, the power is 90% - 100%, the frequency is 20 - 60 kHz, and the etching times is 1 time.

[0021] Further, in Step 3, the electroless copper plating solution is composed of deionized water, electroless copper plating solution A and electroless copper plating solution B mixed in a mass ratio of 15:2 - 3:1 - 2.

[0022] Further, in Step 3, the temperature of the vacuum drying oven is 35 - 40 °C, and the standing duration is 6 - 8 h.

[0023] Further, in Step 5, the adhesive is composed of silicone rubber and conductive material mixed in a mass ratio of 100:6 - 8.

[0024] Further, in Step 6, the temperature for heating and curing is 140 - 150 °C, and the duration is 3 - 5 min.

[0025] The mechanism of the pressure sensor structure based on the electroless copper plating process proposed by the present invention is as follows:

[0026] Through ultraviolet laser etching, the antimony tin oxide on the surface of the upper (lower) support film is exposed, and its active particles are excited, facilitating the occurrence of redox reactions with copper ions in the electroless copper plating solution during the subsequent electroless copper plating process, enabling copper to deposit in the area etched by the ultraviolet laser, forming the upper (lower) copper-plated electrode, and ensuring strong adhesion between the upper (lower) copper-plated electrode and the corresponding upper (lower) support film; since both the upper (lower) support film and the pressure-sensitive film belong to polymer materials, with the help of adhesives, the three can be tightly connected, thereby enhancing the adhesion of the upper (lower) copper-plated electrode on the surface of the pressure-sensitive film, significantly improving the bonding strength between the electrode and the substrate, and endowing the pressure sensor structure with long-term stability and service life.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] Aiming at the problem of loose connection existing in the direct connection between the metal electrode and the pressure-sensitive film of the traditional pressure sensor, the present invention proposes a pressure sensor structure based on the electroless copper plating process and its preparation method. By combining the ultraviolet laser etching and electroless copper plating processes, an electrode with strong adhesion is formed on the surface of the support film, and then, taking advantage of the polymer characteristics of the support film and the pressure-sensitive film, a tight connection between the electrode and the pressure-sensitive film is achieved, improving its electrical conductivity, effectively enhancing the sensitivity and response speed of the pressure sensor structure, thus realizing more accurate and efficient pressure detection, and having long-term stability and service life. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0030] Figure 1 It is a schematic structural diagram of the pressure sensor structure based on the electroless copper plating process proposed in Embodiment 1 of the present invention;

[0031] Figure 2 It is a schematic diagram of the electrode pattern dimensions of the upper copper-plated electrode and the lower copper-plated electrode in Embodiment 1 of the present invention, with the unit of mm; among them, (a) is the overall view; (b) is the partial view;

[0032] Figure 3 It is a process flow chart for the preparation of the upper copper-plated electrode and the lower copper-plated electrode in Embodiment 1 of the present invention;

[0033] Figure 4This is a physical diagram of the pressure sensor structure based on the electroless copper plating process proposed in Embodiment 1 of the present invention; among them, (a) is the overall physical diagram; (b) is the physical diagram of a single electrode unit.

[0034] Figure 5 This is a graph of the resistance change of the pressure sensor structure based on the electroless copper plating process proposed in Embodiment 1 of the present invention under 40 kPa.

[0035] Figure 6 This is a graph of the resistance change of the pressure sensor structure based on the electroless copper plating process proposed in Embodiment 1 of the present invention under repeated pressure application at 120 kPa.

[0036] Figure 7 This is a graph of the resistance fluctuation of the pressure sensor structure based on the electroless copper plating process proposed in Embodiment 1 of the present invention under static conditions.

[0037] Figure 8 This is a graph of the resistance fluctuation of the pressure sensor structure based on the transfer electrode process proposed in Comparative Example 1 under static conditions. Detailed implementation manners

[0038] To further understand the present invention, the preferred implementation schemes of the present invention will be described below in conjunction with embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the invention.

[0039] For all raw materials of the present invention, there is no special limitation on their sources, and they can be purchased on the market or prepared by conventional methods well-known to those skilled in the art.

[0040] For all raw materials of the present invention, there is no special limitation on their purity. The present invention preferably adopts analytical pure or the conventional purity requirements in the field of atomic layer deposition.

[0041] For all raw materials and process procedures of the present invention, their trade names or abbreviations are all conventional trade names or abbreviations in the field. Each trade name or abbreviation is clear and definite in the field of its related uses. Those skilled in the art can purchase or prepare them by conventional methods according to the trade name, abbreviation and corresponding uses, or implement them with corresponding equipment.

[0042] The present invention will be further described in detail below in conjunction with embodiments:

[0043] Embodiment 1

[0044] This embodiment proposes a pressure sensor structure based on the electroless copper plating process, and the structure is as Figure 1 shown, including a top copper-plated electrode, an upper support film, a pressure-sensitive film, a lower support film, and a bottom copper-plated electrode stacked in sequence from top to bottom.

[0045] As Figure 2 shown, both the upper copper-plated electrode and the lower copper-plated electrode include a plurality of square electrode units arranged in a periodic array. The same-direction electrode units are connected by serpentine electrodes. The connection direction of the serpentine electrodes of the upper copper-plated electrode is perpendicular to that of the serpentine electrodes of the lower copper-plated electrode, forming an island-bridge structure. Among them, as Figure 2 shown in (a) of , the size of the electrode unit is about 6.34×6.34 mm 2 , the gap size between adjacent unconnected electrode units is about 6.19 mm, and the small square electrode at the end is used for external connection of wires; as Figure 2 shown in (b) of , the line width of the serpentine electrode is 0.68 mm.

[0046] The materials of the upper support film and the lower support film are a mixed material composed of polydimethylsiloxane, multi-walled carbon nanotubes and antimony tin oxide. The mass ratio among polydimethylsiloxane, multi-walled carbon nanotubes and antimony tin oxide is 100:3-4:5-6.

[0047] The material of the pressure-sensitive film is composed of polydimethylsiloxane and multi-walled carbon nanotubes.

[0048] The preparation method of the pressure sensor structure based on the electroless copper plating process specifically includes the following steps:

[0049] Step 1: Vacuum stir and mix polydimethylsiloxane, multi-walled carbon nanotubes and antimony tin oxide according to a mass ratio of 100:3:5. Specifically, ultrasonically treat for 30 min and stir with a vacuum mixer for 1 min to make it evenly stirred. Spin-coat on a spin coater at a speed of 450 rpm for 2 min, and heat on a heating table at 150 °C for 5 min to make it cured and formed, obtaining the upper support film and the lower support film;

[0050] Step 2: Use ultraviolet laser etching to obtain corresponding electrode patterns on the surfaces of the upper support film and the lower support film, and activate surface active particles. Among them, the speed of the ultraviolet laser is 2000 mm / s, the power is 90%, the frequency is 60 kHz, and the etching times is 1 time;

[0051] Step 3: Mix deionized water, electroless plating solution A and electroless plating solution B according to a mass ratio of 15:2:1 to prepare an electroless copper plating solution. After ultrasonic treatment for 1 min, place it in a vacuum machine to extract vacuum for 5 min. Then immerse the etched upper support film and lower support film into the electroless copper plating solution, seal and let it stand in a vacuum drying oven at 35 °C for 8 hours to obtain the upper copper-plated electrode deposited on the surface of the upper support film and the lower copper-plated electrode deposited on the surface of the lower support film. The overall preparation process is as Figure 3 shown; among them, electroless plating solution A and electroless plating solution B are commercial electroless copper plating solutions, and the main components of their mixture include copper sulfate, sodium malate, sodium carbonate and sodium citrate.

[0052] Step 4: Prepare the pressure-sensitive film by the template method, specifically as follows:

[0053] First, mix and stir polydimethylsiloxane and multi-walled carbon nanotubes in a mass ratio of 100:3, ultrasonic for 30 min, then add a curing agent and put it into a vacuum mixer to stir for 1 min to obtain a mixed solution, where the mass ratio of the curing agent to polydimethylsiloxane is 1:10; then add the ground NaCl powder to the mixed solution and mix evenly to obtain a mixture, where the mass ratio of polydimethylsiloxane to NaCl is 1:3; then fill the mixture into a metal groove of 7.5 m×7.5 cm×1 mm, and place it on a heating table at 150 °C to heat for 5 min, take it out after curing, then soak it in deionized water for more than 12 h until the dissolved NaCl is removed, and finally place it in an oven at 60 °C for 30 min to remove the moisture, thus obtaining the pressure-sensitive film;

[0054] Step 5: Mix and stir silicone rubber and multi-walled carbon nanotubes evenly in a mass ratio of 100:6 to prepare an adhesive. Use the adhesive to bond the upper support film and the lower support film to the upper and lower surfaces of the pressure-sensitive film respectively, ensure that the electrode pattern arrangement directions of the upper copper-plated electrode and the lower copper-plated electrode are perpendicular to each other, place it on a heating table at 150 °C to heat for 5 min to cure the adhesive and form a pressure sensor structure based on the electroless copper plating process. The physical object is as Figure 4 shown, where Figure 4 (a) in it is the overall physical object diagram, Figure 4 (b) in it is the physical object diagram of a single electrode unit.

[0055] Figure 5 is the resistance change curve diagram of the pressure sensor structure based on the electroless copper plating process proposed in this embodiment under 40 kPa, Figure 6 is the resistance change curve diagram of the pressure sensor structure based on the electroless copper plating process proposed in this embodiment under repeated pressure application at 120 kPa. According to Figure 5 and Figure 6 it can be seen that the obtained pressure sensor structure based on the electroless copper plating process has different responses under different pressures, proving its good sensing performance, and under the condition of cyclic loading, it can maintain good repeatability and stability, indicating that the obtained pressure sensor structure based on the electroless copper plating process can work stably for a long time and has excellent sensing performance.

[0056] Comparative Example 1

[0057] This comparative example prepared a pressure sensor structure based on the transfer electrode process, including an upper electrode layer, a pressure-sensitive film, and a lower electrode layer stacked in sequence. The preparation process includes the following steps:

[0058] Step 1: Prepare the pressure-sensitive film according to the process of Step 4 in Example 1;

[0059] Step 2: Stick the double-sided thermal release tape of 7×7 cm 2 on a glass sheet of the same size. Then stick a water-soluble tape of the same size on the other side of the thermal release tape. After that, stick a copper foil of 7 cm×7 cm×0.01 mm on the other side of the water-soluble tape. Finally, selectively etch the copper foil according to the electrode pattern with ultraviolet laser. After tearing off the redundant part, the upper electrode layer and the lower electrode layer are obtained;

[0060] Step 3: Mix silicone rubber and multi-walled carbon nanotubes at a mass ratio of 100:6 and stir evenly to prepare an adhesive. Use the adhesive to bond the upper electrode layer and the lower electrode layer to the upper and lower surfaces of the pressure-sensitive film respectively, ensuring that the electrode pattern arrangement directions of the upper electrode layer and the lower electrode layer are perpendicular to each other to form an island-bridge structure. Then place it on a heating table at 150 °C and heat for 5 min to cure the adhesive and release the thermal release tape at the same time. Wash off the water-soluble tape with running water and place it in an oven at 60 °C to dry for 30 min to obtain a pressure sensor structure based on the transfer electrode process.

[0061] Perform stability tests on the pressure sensor structure based on the electroless copper plating process obtained in Example 1 and the pressure sensor structure based on the transfer electrode process obtained in Comparative Example 1 respectively. Specifically, test the resistance fluctuation curve under static conditions to obtain the results of Example 1 as shown in Figure 7 and the results of Comparative Example 1 as shown in Figure 8 It can be seen that the resistance fluctuation of the pressure sensor structure based on the transfer electrode process obtained in Comparative Example 1 is as high as about 12% under static conditions, while the resistance fluctuation of the pressure sensor structure based on the electroless copper plating process obtained in Example 1 is only about 3% under static conditions, which is much lower than that of Comparative Example 1. The results show that the electrode preparation process of Example 1 has better electrical conductivity, can stably transmit signals, provides guarantee for the rapid and accurate response of the pressure sensor structure, and has good development prospects in the field of flexible pressure sensors.

[0062] In this article, specific examples are used to elaborate on the principles and implementation modes of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention, including the best mode, and also enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of the present invention is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A pressure sensor structure based on chemical copper deposition process, characterized in that: It includes an upper copper-plated electrode, an upper supporting film, a pressure-sensitive film, a lower supporting film and a lower copper-plated electrode stacked in sequence from top to bottom; wherein the upper copper-plated electrode and the lower copper-plated electrode are prepared by a chemical copper plating process, and the arrangement directions of the electrode patterns of the two are perpendicular to each other to form an island bridge structure; the material of the upper supporting film and the lower supporting film is a mixed material composed of a high molecular polymer, a conductive material and antimony tin oxide.

2. The pressure sensor structure based on the chemical copper deposition process according to claim 1 is characterized in that: The upper copper-plated electrode and the lower copper-plated electrode both include a plurality of electrode units arranged in a periodic array, and the electrode units in the same direction are connected by serpentine electrodes, and the connection direction of the serpentine electrodes of the upper copper-plated electrode is perpendicular to the connection direction of the serpentine electrodes of the lower copper-plated electrode.

3. The pressure sensor structure based on the chemical copper deposition process according to claim 1 is characterized in that: In the upper supporting film and the lower supporting film, the mass ratio of the high molecular polymer, the conductive material and antimony tin oxide is 100:3-4:5-6; wherein the high molecular polymer is polydimethylsiloxane or silicone rubber, and the conductive material is multi-walled carbon nanotubes or carbon black.

4. A method for preparing a pressure sensor structure based on a chemical copper deposition process, characterized in that: The following steps are involved: Step 1, mixing a high molecular polymer, a conductive material and antimony tin oxide in a vacuum, and then heating and curing the mixture after spin coating to obtain an upper support film and a lower support film; Step 2: using ultraviolet laser etching to obtain corresponding electrode patterns on the surfaces of the upper supporting film and the lower supporting film, and activating the surface active particles; Step 3, preparing a chemical copper plating solution, immersing the etched upper support film and the lower support film into the chemical copper plating solution under a vacuum environment, and after standing in a vacuum drying oven for a period of time, obtaining an upper copper-plated electrode deposited on the surface of the upper support film and a lower copper-plated electrode deposited on the surface of the lower support film; Step 4: Prepare a pressure-sensitive film by using a template method; Step 5, prepare an adhesive, and use the adhesive to adhere the upper support film and the lower support film to the upper and lower surfaces of the pressure-sensitive film respectively, ensuring that the electrode pattern arrangement directions of the upper copper-plated electrode and the lower copper-plated electrode are perpendicular to each other. After heating and curing, a pressure sensor structure based on the chemical copper deposition process as described in any one of claims 1 to 3 is obtained.

5. The method for preparing a pressure sensor structure based on chemical copper deposition process according to claim 4, characterized in that: In step 1, the temperature of heating and curing molding is 120-150°C, and the duration is 3-5 minutes; the specific process of vacuum stirring and mixing is: first ultrasonic for 30-40 minutes, and then stirring in a vacuum mixer for 1-2 minutes; the rotation speed of spin coating is 450-550rpm, and the duration is 1-2 minutes.

6. The method for preparing a pressure sensor structure based on chemical copper deposition process according to claim 4, characterized in that: In step 2, the speed of the ultraviolet laser is 1500-2000 mm / s, the power is 90%-100%, the frequency is 20-60 kHz, and the etching number is 1 time.

7. The method for preparing a pressure sensor structure based on chemical copper deposition process according to claim 4, characterized in that: In step 3, the chemical copper plating solution is prepared by mixing deionized water, chemical plating solution A and chemical plating solution B in a mass ratio of 15:2 to 3:1 to 2.

8. The method for preparing a pressure sensor structure based on chemical copper deposition process according to claim 4, characterized in that: In step 3, the temperature of the vacuum drying oven is 35-40° C., and the standing time is 6-8 hours.

9. The method for preparing a pressure sensor structure based on chemical copper deposition process according to claim 4, characterized in that: In step 5, the adhesive is formed by mixing silicone rubber and conductive material in a mass ratio of 100:6-8.

10. The method for preparing a pressure sensor structure based on chemical copper deposition process according to claim 4, characterized in that: The temperature of heating and curing molding in step 6 is 140-150° C. and the duration is 3-5 minutes.

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