Preparation method of flexible device based on array type copper mesh electrode

Abstract

The invention discloses a preparation method of a flexible device based on an array type copper net electrode, which comprises the following steps: treating an oxide on the surface of a copper net by a wet method, and immersing the treated copper net into a rosin ethanol solution for wetting; attaching the wetted copper net to a hard substrate, and drying for 1-10 minutes; patterning the copper mesh by adopting a femtosecond laser micro-nano processing technology to obtain a copper mesh electrode array; aligning and bonding the copper mesh electrode array and the arrayed electronic elements, and injecting a flexible material among the electronic elements to package the electronic elements; and heating the hard substrate to melt the rosin, and stripping the hard substrate from the patterned copper mesh to obtain the flexible device. The flexible device prepared by the preparation method has relatively good bending resistance, tensile resistance and higher output performance.

Description

Technical Field

[0001] The invention belongs to the technical field of flexible device integration, and in particular relates to a method for preparing a flexible device based on an array-type copper mesh electrode. Background Art

[0002] With the rapid development of science and technology, digitalization and intelligence have penetrated into various fields such as the Internet of Things, human-computer interaction, and medical monitoring. This has also given rise to an urgent need for various functional flexible devices on the surfaces of various complex structures. Flexible devices have the advantages of being soft, light, bendable and stretchable. They can flexibly match special-shaped surfaces such as skin and realize applications such as display, sensing, and power generation in a wider range of scenarios. In particular, array-type flexible electronic devices, such as LED display devices, photoelectric sensor arrays, and thermoelectric devices, can achieve higher resolution, stronger output, and higher flexibility by connecting arrayed microelectronic components through flexible electrodes.

[0003] The invention patent application with publication number CN105047259A discloses a medical flexible integrated electrode. The patent application includes a polyimide insulating layer, a flexible rolled copper foil conductive base layer and a silver / silver chloride signal sensing layer stacked in sequence. This electrode can effectively customize various signal feedback and control circuits through the processing technology of a flexible printed circuit board. The patent application not only has good flexibility, but also can contact the body surface well. Sensors / sensors (electrodes / electrodes) used in clinical medicine and portable medical electrophysiological examinations, and signal feedback circuits. It can be used in conjunction with various electrophysiological detection instruments and equipment to detect and feedback the electrical activities of organs with different shapes and ups and downs such as the heart, muscles, nerves, and brain. However, the bending and stretching resistance of the medical flexible integrated electrode disclosed in the patent application needs to be improved.

[0004] The invention patent application with publication number CN116614907A discloses an electrode suitable for a flexible electric heating film, including a conductive film, an electrode layer, a packaging layer and a substrate layer, wherein the electrode layer is made of liquid metal. The electrode suitable for a flexible electric heating film of the present invention adopts an electrode layer made of liquid metal, which solves the problem that the flexible electric heating film in the prior art uses hard metals such as copper foil as electrodes and is prone to fatigue and fracture, enhances the bending resistance of the flexible electric heating film, and improves the working reliability of the flexible electric heating film. The edge of the packaging layer is connected to the conductive film outside the edge of the substrate layer to ensure the sealing of the packaging. At the same time, the invention patent application also uses the hollow part of the substrate layer to connect the conductive film and the packaging layer, further improving the strength of the connection structure between the conductive film and the packaging layer, and improving the packaging reliability. At the same time, the invention patent application also provides a method for preparing the above-mentioned electrode suitable for a flexible electric heating film, and the invention patent application also provides a flexible electric heating film. However, the invention patent application introduces additional parasitic thermal resistance in the packaging process of the electrode layer made of liquid metal.

[0005] Selecting appropriate flexible electrodes and forming them into arrays is a key to realizing array integration of flexible electronic devices. Currently, flexible electrodes such as conductive paste, thin film metal, serpentine metal wire and liquid metal are mostly formed into arrays by scraping, cutting, physical or chemical deposition. However, there are still some problems with these electrodes. For example, slurry electrodes and thin film metals are prone to breakage after repeated bending; the high electrode resistance of serpentine metal wires will seriously reduce the output performance of the device; liquid metal electrodes have leakage problems, and their packaging often brings large parasitic thermal resistance. Summary of the invention

[0006] The invention provides a method for preparing a flexible device based on an array-type copper mesh electrode. The flexible device prepared by the preparation method has good bending resistance, stretching resistance and higher output performance.

[0007] The present invention provides a method for preparing a flexible device based on an array copper mesh electrode, comprising:

[0008] The oxide on the surface of the copper mesh is treated by a wet method, and the treated copper mesh is immersed in a rosin ethanol solution for wetting;

[0009] Attach the moistened copper mesh to a hard substrate and dry for 1 to 10 minutes;

[0010] The copper mesh was patterned using femtosecond laser micro-nano processing technology to obtain a copper mesh electrode array;

[0011] aligning and bonding the copper mesh electrode array and the arrayed electronic components, and injecting a flexible material between the electronic components to encapsulate the electronic components;

[0012] The hard substrate is heated to melt the rosin, and the hard substrate and the patterned copper mesh are peeled off to obtain a flexible device.

[0013] The present invention utilizes rosin ethanol solution to wet the copper mesh and then attaches it to a hard substrate. The wet copper mesh can be self-adsorbed onto the hard substrate. By controlling the appropriate attachment time, the copper mesh can be relatively flatly adhered to the substrate after the ethanol evaporates, thereby avoiding warping.

[0014] The present invention utilizes the bending and stretching resistance of the copper mesh, so that the flexible device made of the copper mesh electrode provided by the present invention has good bending and stretching resistance; compared with the serpentine wire electrode, the copper mesh electrode provided by the present invention has more conductive paths and smaller electrode resistance, so that the flexible device provided by the present invention has higher output performance; compared with the liquid metal electrode, the copper mesh electrode provided by the present invention does not require packaging during the preparation process, so no additional parasitic thermal resistance is introduced.

[0015] The present invention designs the device structure and adopts femtosecond laser micro-nano processing technology to pattern the copper mesh to prepare a high-precision copper mesh electrode array.

[0016] Preferably, the wire diameter of the copper mesh is less than 1 mm. If the wire diameter is too large, the flexibility of the copper mesh will deteriorate, the difficulty of patterning the copper mesh will increase, and the accuracy will decrease.

[0017] Preferably, the mass percentage of rosin in the rosin ethanol solution is 5%-40%.

[0018] The present invention controls the content of rosin to avoid the precipitation of rosin, so that the copper mesh soaked in the rosin ethanol solution can be better attached to the surface of the hard substrate to avoid warping.

[0019] Preferably, the wet treatment process is: cleaning the copper mesh with an organic solvent, removing the surface oxide layer with an oxide etching solution, then removing the residual oxide etching solution with a volatile solvent, and drying to obtain the treated copper mesh.

[0020] The present invention removes oxides and organic pollutants on the surface of the copper mesh through wet treatment, thereby minimizing the influence of oxides and impurities on electrode resistance.

[0021] Further preferably, the organic solvent is a solvent such as acetone and ethanol that can remove organic pollutants, the oxide etching solution is an etching solution such as dilute hydrochloric acid and dilute sulfuric acid that can remove the oxide layer on the surface of the copper mesh, and the volatile solvent is a volatile solvent such as water and ethanol that can remove residual etching solution.

[0022] Preferably, the hard substrate is a substrate with a flat surface, and the material is aluminum nitride, aluminum oxide, silicon wafer or glass.

[0023] Preferably, aligning and bonding the copper mesh electrode array and the arrayed electronic components comprises:

[0024] Inserting the arrayed electronic components into the double-layer porous template;

[0025] The copper mesh electrode array includes an upper electrode array and a lower electrode array, a multi-hole mask is prepared by using a femtosecond laser based on the electronic components arranged in the array, and solder paste is printed on the upper electrode array and the lower electrode array respectively through the multi-hole mask;

[0026] The upper electrode array is first bonded to one end of the electronic components arranged in the array through solder paste, the double-layer porous template is taken out, and then the lower electrode array is bonded to the other end of the electronic components arranged in the array through solder paste, thereby completing the alignment and bonding of the copper mesh electrode array and the arrayed electronic components.

[0027] Preferably, the double-layer porous template comprises two layers of templates with aligned holes, and a gasket is provided at the edge between the two layers of porous templates. The present invention places electronic components into the holes of the two layers of porous templates, and increases the distance between the two layers of porous modules by the gasket, so that the electronic components can be firmly located inside the holes, thereby achieving precise bonding.

[0028] Preferably, the electronic components are display, sensing, power generation and heating components.

[0029] Preferably, the flexible material is silicone, rubber, hydrogel or resin.

[0030] Preferably, the temperature of the heated hard substrate is 100-300°C

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The preparation method utilizes rosin ethanol solution to better adhere the copper mesh to the substrate, and at the same time utilizes the bending resistance and tensile strength of the copper mesh and more conductive paths, so that the flexible device prepared by the preparation method has better bending resistance and tensile strength. Since the copper mesh electrode prepared by the present invention has a small resistance, and since no packaging material is introduced when preparing the copper mesh electrode, no additional parasitic thermal resistance is introduced, the flexible device provided by the present invention has higher output performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A flowchart of a method for preparing a flexible device based on an array copper mesh electrode provided in a specific embodiment of the present invention;

[0034] Figure 2 A photo of the copper mesh provided in Example 1 of the present invention;

[0035] Figure 3A photo of a copper mesh flatly adhered to a hard substrate provided in Example 1 of the present invention;

[0036] Figure 4 A photograph of the upper and lower electrodes of a copper mesh patterned by femtosecond laser provided in Example 1 of the present invention;

[0037] Figure 5 This is a photo of the electronic component (thermoelectric particle) provided in Example 1 of the present invention located in a double-layer porous template;

[0038] Figure 6 This is a photo of the electronic component (thermoelectric particle) provided in Example 1 of the present invention after being welded and bonded to the upper and lower electrodes of the copper mesh;

[0039] Figure 7 A photograph of a flexible thermoelectric device after the elastomer in the gaps between thermoelectric particles provided in Example 1 of the present invention is filled and the substrate is peeled off;

[0040] Figure 8 This is a photo of the flexible thermoelectric device provided in Example 1 of the present invention under twisting and tensile strain;

[0041] Fig. 9 The power generation output IV characteristics and output power diagram of the flexible thermoelectric device provided in Example 1 of the present invention;

[0042] Fig.10 This is a picture of the electrode breakage of the flexible thermoelectric device provided in Comparative Example 1 of the present invention after the bending test.

[0043] Specific embodiment

[0044] The technical solutions in the specific embodiments of the present invention are clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0045] In view of the deficiencies in the prior art, the present invention provides a method for preparing a flexible device based on an array-type copper mesh electrode. A copper mesh with extremely strong bending and stretching resistance is selected as the flexible electrode, and a wetting self-adsorption and femtosecond laser micro-nano processing method is used to achieve high-precision array preparation of the copper mesh for rapid integration of array-type flexible devices. The technical effects that can be achieved are as follows: 1. Compared with thin film metal and slurry electrodes, selecting copper mesh as an electrode for connecting electronic components can make the device have stronger bending and stretching resistance, thereby improving the application value of flexible devices; 2. Copper mesh has more conductive paths than serpentine wire electrodes, so the electrode resistance is smaller, which can make the device have higher output performance; 3. Copper mesh does not need to be packaged as an electrode and will not introduce additional parasitic thermal resistance; 4. Flattening the soft copper mesh is crucial for its high-precision patterning processing. The present invention uses rosin adhesive to wet the copper mesh so that the copper mesh can be self-adsorbed and flattened on a hard substrate, and then high-precision arraying of copper mesh electrodes can be achieved through femtosecond laser micro-nano processing; the rosin adhesive used can also be used as a flux to avoid interface contamination when welding the mesh electrode to the electronic component, obtain high connection strength and low contact impedance, thereby ensuring high reliability and high output performance while achieving rapid integration of flexible devices.

[0046] A specific embodiment of the present invention provides a method for preparing a flexible device based on an array copper mesh electrode, such as Figure 1 As shown, including:

[0047] like Figure 1 As shown in (a), the copper mesh is wet treated: select a suitable copper mesh, first clean the copper mesh with an organic solvent, then use an oxide etching solution to remove the surface oxide layer, and then use a volatile solvent to remove the residual etching solution. After the copper mesh is dried, it is immersed in rosin ethanol adhesive for wetting.

[0048] The wire diameter of the copper mesh provided in the specific embodiment of the present invention is less than 1 mm, the organic solvent is a solvent such as acetone and ethanol that can remove organic pollutants, the oxide etching solution is a dilute hydrochloric acid, dilute sulfuric acid and other etching solutions that can remove the oxide layer on the surface of the copper mesh, and the volatile solvent is a volatile solvent such as water and ethanol that can remove the residual etching solution.

[0049] like Figure 1 As shown in (b), self-adsorption to a hard substrate: the copper mesh wetted with rosin ethanol is attached to a hard substrate, the wet copper mesh will self-adsorb onto the hard substrate, and after the ethanol evaporates, the copper mesh will adhere flatly to the substrate.

[0050] The hard substrate provided in the specific embodiment of the present invention is a substrate with a flat surface such as aluminum nitride, aluminum oxide, silicon wafer, glass, etc.

[0051] like Figure 1As shown in (c), patterned copper mesh electrode: According to the device structure design, the copper mesh is patterned using femtosecond laser micro-nano processing technology to prepare a high-precision copper mesh electrode array.

[0052] like Figure 1 As shown in (d) and (e), the copper mesh electrode is integrated with the electronic component array. The arrayed electronic components are aligned and bonded with the copper mesh electrode with a hard substrate. The electronic components can be display, sensor, power generation and other components.

[0053] like Figure 1 As shown in (f), the hard substrate is encapsulated and removed: the electronic components are encapsulated with flexible materials, and then the substrate is heated to melt the rosin adhesive, and then the substrate and the copper mesh are peeled off, finally realizing the preparation of an array-type flexible device based on the copper mesh.

[0054] The flexible packaging material provided in the specific embodiment of the present invention can be a polymer material such as silica gel, rubber, hydrogel, resin, etc., and the temperature of heating the substrate is greater than 100°C. Example 1

[0055] The present invention provides an embodiment, which is a method for preparing an array copper mesh electrode for flexible device integration, and preparing a flexible thermoelectric device containing 36 pairs of thermoelectric particles, the steps are as follows:

[0056] (1) Copper mesh wet treatment: Figure 2 As shown, a copper mesh with a wire diameter of 25um was selected, and the copper mesh was ultrasonically cleaned with acetone and ethanol to remove organic pollutants, and then soaked in 10% dilute hydrochloric acid to remove the oxide layer on the surface of the copper mesh, and then ethanol was used to remove the residual hydrochloric acid. A 10% rosin adhesive was prepared with rosin and ethanol, and after the copper mesh was dried, it was soaked in the adhesive to wet it.

[0057] (2) Self-adhesive hard substrate: Figure 3 As shown, the copper mesh wetted with rosin ethanol is attached to the aluminum nitride substrate. The wet copper mesh will self-adsorb onto the substrate. After the ethanol evaporates, the copper mesh will adhere flatly to the aluminum nitride substrate.

[0058] (3) Patterned copper mesh electrode: A thermoelectric device containing 36 pairs of thermoelectric particles and a duty cycle of 10% was designed. The size of the thermoelectric particles was 0.8 mm*0.8 mm*2.5 mm. The upper and lower electrodes were designed according to the device structure. The copper mesh was patterned using femtosecond laser micro-nano processing technology to prepare high-precision copper mesh upper electrode arrays and lower electrode arrays, such as Figure 4 As shown, Figure 4 There are two photos, one of which is the upper electrode array and the other is the lower electrode array.

[0059] (4) Arraying of thermoelectric particles: According to the size of the thermoelectric particles, femtosecond laser technology is used to punch holes in a 200um thick stainless steel plate. The size of the holes is about 0.86*0.86mm, slightly larger than the size of the thermoelectric particles. Two perforated stainless steel plates are aligned, and a 0.38mm thick aluminum nitride sheet gasket is placed between the two layers of stainless steel plates to form a double-layer porous template. It can be understood that the gasket is away from the perforated electronic components. Its function is to lift the two perforated stainless steel plates so that the thermoelectric particles can be firmly located inside the holes. Figure 5 As shown, the thermoelectric particles are then positioned and arranged in a double-layer porous template to form an array. The use of a double-layer porous template can make the thermoelectric particles more stably and neatly arranged.

[0060] (5) Copper mesh electrode-thermoelectric particle integration: A 100 μm thick stainless steel porous mask with a hole size of 0.8 mm*0.8 mm was prepared using a femtosecond laser. This mask was used to print Sn on the patterned copper mesh electrode. 64 Bi 35 Ag1 solder paste is used to bond the upper and lower electrode arrays to the two ends of the arrayed thermoelectric particles. First, the arrayed thermoelectric particles are aligned with the upper electrode array for welding and bonding, then the double-layer porous template that fixes the thermoelectric particles is removed, and then the thermoelectric particles are welded and bonded to the lower electrode array to form an electrical path, such as Figure 6 As shown, the soldering temperature is 200°C.

[0061] (6) Encapsulation and removal of substrate: A mixture of AB glue and high elastic silicone rubber is filled into the gaps between the thermoelectric particles in a ratio of 1:1. After curing at room temperature for 1 hour, the aluminum nitride substrate is heated to 110°C to melt the rosin adhesive on the interface between the copper mesh and the substrate. The aluminum nitride substrate is then separated from the copper mesh to finally obtain a substrate-free copper mesh electrode flexible thermoelectric device, such as Figure 7 as shown in (a) and (b).

[0062] Thermoelectric device strain test and power generation performance test: The internal resistance of the flexible thermoelectric device provided by the present invention is about 3Ω. Figure 8 After repeated twisting and stretching 1000 times as shown in a and b, the internal resistance changes within 5%, indicating the high flexibility and high stability of the device.

[0063] like Fig. 9 As shown, the power generation performance test results of the flexible device prepared in this embodiment show that when the temperature difference is greater than 30K, the device can output an open circuit voltage greater than 0.4V, and the maximum output power can reach 11mW. This output performance can meet the self-powering requirements of many wearable electronic devices.

[0064] Comparative Example 1

[0065] Comparative Example 1 provided by the present invention uses copper foil as a flexible electrode to prepare a flexible thermoelectric device including 36 pairs of thermoelectric particles, and the steps are as follows:

[0066] (1) Wet treatment of copper foil: Select a copper foil with a thickness of 25 μm, use acetone and ethanol to ultrasonically clean the copper mesh to remove organic pollutants, then soak it in 10% dilute hydrochloric acid to remove the oxide layer on the surface of the copper mesh, and then use ethanol to remove the residual hydrochloric acid.

[0067] (2) Pasting and patterning copper foil: Paste the copper foil on the aluminum nitride substrate with an adhesive, and then pattern the copper foil into the desired electrode array using femtosecond laser micro-nano processing.

[0068] (3) Arraying of thermoelectric particles: Based on the size of the thermoelectric particles of 0.8mm*0.8mm*2.5mm, a femtosecond laser technique is used to punch holes in a 200um thick stainless steel plate. The size of the holes is about 0.86*0.86mm, slightly larger than the size of the thermoelectric particles. Align the two perforated stainless steel plates, and place a 0.38mm thick aluminum nitride sheet between the two layers of stainless steel plates to form a double-layer porous template. The thermoelectric particles are then positioned and placed in the template to form an array. The use of a double-layer template can make the thermoelectric particles more stable and neatly arranged.

[0069] (4) Copper foil electrode-thermoelectric particle integration: A 100 μm thick stainless steel porous mask with a hole size of 0.8 mm*0.8 mm was prepared using a femtosecond laser. This mask was used to print Sn on the patterned copper foil electrode. 64 Bi 35 Ag1 solder paste. First, align the arrayed thermoelectric particles with the upper electrode for welding and bonding, then remove the double-layer porous mask that fixes the thermoelectric particles, and then weld and bond the thermoelectric particles with the lower electrode to form an electrical path. The welding temperature is 200°C.

[0070] (5) Encapsulation and removal of substrate: A mixture of AB glue and highly elastic silicone is filled into the gaps between the thermoelectric particles in a ratio of 1:1. After curing at room temperature for 1 hour, the aluminum nitride substrate is heated to 150°C to melt the adhesive on the interface between the copper foil electrode and the substrate. The aluminum nitride substrate is then separated from the copper foil to obtain a flexible thermoelectric device based on copper foil.

[0071] Strain test of thermoelectric devices: After only a dozen bending tests, the flexible thermoelectric device with copper foil as electrode had electrode breakage problems, such as Fig.10 As shown, the device completely fails. From this comparative example, it can be seen that the arrayed copper mesh has significant advantages in preparing flexible devices as electrodes.

Claims

1. A method for preparing a flexible device based on an array copper mesh electrode, characterized in that: include: The oxide on the surface of the copper mesh is treated by a wet method, and the treated copper mesh is immersed in a rosin ethanol solution for wetting; Attach the moistened copper mesh to a hard substrate and dry for 1 to 10 minutes; The copper mesh was patterned using femtosecond laser micro-nano processing technology to obtain a copper mesh electrode array; aligning and bonding the copper mesh electrode array and the arrayed electronic components, and injecting a flexible material between the electronic components to encapsulate the electronic components; The hard substrate is heated to melt the rosin, and the hard substrate and the patterned copper mesh are peeled off to obtain a flexible device.

2. The method for preparing a flexible device based on an array copper mesh electrode according to claim 1, characterized in that: The wire diameter of the copper mesh is less than 1 mm.

3. The method for preparing a flexible device based on an array copper mesh electrode according to claim 1, characterized in that: The mass percentage of rosin in the rosin ethanol solution is 5%-40%.

4. The method for preparing a flexible device based on an array copper mesh electrode according to claim 1, characterized in that: The wet treatment process is: cleaning the copper mesh with an organic solvent, removing the surface oxide layer with an oxide etching solution, removing the residual oxide etching solution with a volatile solvent, and drying to obtain the treated copper mesh.

5. The method for preparing a flexible device based on an array copper mesh electrode according to claim 4, characterized in that: The organic solvent is acetone, ethanol or other solvents; The oxide etching solution is dilute hydrochloric acid or dilute sulfuric acid; The volatile solvent is water or ethanol.

6. The method for preparing a flexible device based on an array copper mesh electrode according to claim 1, characterized in that: The hard substrate is a substrate with a flat surface, and the material of the hard substrate is aluminum nitride, aluminum oxide, silicon wafer or glass.

7. The method for preparing a flexible device based on an array copper mesh electrode according to claim 1, characterized in that: The step of aligning and bonding the copper mesh electrode array and the arrayed electronic components comprises: Inserting the arrayed electronic components into a double-layer porous template, and placing a gasket at the edge between the double-layer porous template; The copper mesh electrode array includes an upper electrode array and a lower electrode array, a multi-hole mask is prepared by using a femtosecond laser based on the electronic components arranged in the array, and solder paste is printed on the upper electrode array and the lower electrode array respectively through the multi-hole mask; The upper electrode array is first bonded to one end of the electronic components arranged in the array through solder paste, the double-layer porous template is taken out, and then the lower electrode array is bonded to the other end of the electronic components arranged in the array through solder paste, thereby completing the alignment and bonding of the copper mesh electrode array and the arrayed electronic components.

8. The method for preparing a flexible device based on an array copper mesh electrode according to claim 1, characterized in that: The electronic component is a display, sensor, heating or power generation component.

9. The method for preparing a flexible device based on an array copper mesh electrode according to claim 1, characterized in that: The flexible material is silicone, rubber, hydrogel or resin.

10. The method for preparing a flexible device based on an array copper mesh electrode according to claim 1, characterized in that: The temperature of the heated hard substrate is 100-300°C.

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