A method for patterning flexible substrate copper electrode integrated with high thermal conductivity back layer

Abstract

This invention discloses a method for patterning copper electrodes on flexible substrates with integrated high thermal conductivity back layers, belonging to the interdisciplinary fields of flexible electronics manufacturing, additive manufacturing, and micro / nano fabrication. The invention achieves high reliability of the copper electrode under the combined effects of mechanical deformation and Joule heating by constructing a high thermal conductivity filler / polymer composite back layer on the back of a polymer substrate, combined with stress-relieving pattern design of the front copper layer. High-precision patterned copper electrode design at room temperature is achieved through 3D printing-assisted masking technology combined with a fine filling process. The introduction of a high thermal conductivity composite back layer structure establishes efficient lateral and normal heat diffusion paths, significantly reducing the temperature of local hot spots on the electrode and effectively suppressing interface delamination that may be induced by thermal stress. This invention achieves excellent thermal management capabilities and cycling stability while ensuring excellent mechanical flexibility of the electrode, providing key technical support for the integration of flexible electronic systems and active thermal management devices.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of flexible electronics manufacturing, additive manufacturing and micro-nano processing, and relates to a method for patterning copper electrodes on flexible substrates with integrated high thermal conductivity back layers. Specifically, it relates to a method for integrating high thermal conductivity back layers on flexible polymer substrates and preparing high-precision patterned copper electrodes, which is applicable to various flexible electronic systems such as flexible circuits, sensors, wearable devices, and thermal management devices. Background Technology

[0002] With the rapid development of flexible electronics technology, systems such as flexible circuits, sensors, wearable devices, and displays are placing increasing demands on high-performance, customizable, and mechanically deformable patterned conductive electrodes. In dynamic service scenarios involving repeated bending, stretching, or thermal cycling, electrodes not only need to possess good conductivity, but their interfacial bonding strength with the flexible substrate, thermomechanical matching, and the durability of the structure itself are also key factors directly affecting device reliability.

[0003] In the field of flexible electronics, traditional electrodes face bottlenecks such as insufficient mechanical properties, weak interfacial bonding, and limited application scenarios. To address these issues, domestic researchers have conducted extensive studies and proposed several cutting-edge solutions. For example, Chinese invention patent (application number 202511767353.9) provides a method for preparing a nanobiomass-based flexible electrode. By adjusting ultrasonic fragmentation and high-speed shearing conditions, a biomass-based flexible electrode with a porous structure and excellent mechanical properties is prepared, effectively solving the performance degradation problem under complex scenarios. Another Chinese invention patent (application number 202610210240.7), targeting brain-computer interface applications, introduces a functional coating to reduce the risk of contact and infection with external human tissue during flexible electrode implantation. While existing technologies can achieve the functionality of flexible electrodes, they cannot achieve high-precision patterned copper electrode design and fail to design and manufacture functional electrodes for both electrical and thermal fields.

[0004] The fabrication of flexible patterned copper electrodes primarily relies on traditional subtractive manufacturing techniques, which suffer from complex processes, high energy consumption, and difficulty in efficiently achieving patterned copper electrode structures. Common additive manufacturing methods (such as direct printing of conductive inks, electroless plating, vacuum deposition, and patterning) can reduce material consumption to some extent, but still face numerous challenges: direct printing of metal pastes often requires high-temperature sintering to achieve high conductivity, which is incompatible with many heat-sensitive polymer substrates. Furthermore, flexible copper electrodes generate significant Joule heating when powered on. Since most flexible polymer substrates (such as polyimide and PET) have extremely low thermal conductivity (typically below 0.3 W / m·K), heat dissipation is difficult, easily leading to hot spots in localized areas of the electrode. These hot spots not only accelerate interface aging of the copper layer but also generate thermal stress due to thermal expansion mismatch, causing electrode breakage or peeling from the substrate, severely limiting the power density and long-term reliability of flexible electronic devices.

[0005] Therefore, there is an urgent need to develop a new method for fabricating flexible electrodes that can simultaneously achieve high-precision patterning, excellent mechanical strain adaptability, and effective thermal diffusion capability, in order to support the broader design innovation and application expansion of flexible electronic devices. Summary of the Invention

[0006] To address the problems of existing technologies, this invention provides a method for patterning copper electrodes on flexible substrates with integrated high thermal conductivity back layers. By constructing a high thermal conductivity filler / polymer composite back layer on the back of a polymer substrate, combined with stress-relieving pattern design of the front copper layer, high reliability of the copper electrode is achieved under the combined effects of mechanical deformation and Joule heating. This invention utilizes 3D printing-assisted masking technology combined with a fine filling process to achieve high-precision patterned copper electrode design at room temperature, improving the mechanical integrity of the flexible substrate. Furthermore, by introducing a high thermal conductivity composite back layer structure, this invention establishes efficient lateral and normal heat diffusion paths, significantly reducing the temperature of local hot spots on the electrode and effectively suppressing interface delamination that may be induced by thermal stress. This invention achieves excellent thermal management capabilities and cycling stability while ensuring excellent mechanical flexibility of the electrode, providing key technical support for the integration of flexible electronic systems and active thermal management devices.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for patterning a flexible substrate copper electrode with an integrated high thermal conductivity back layer, the method comprising the following steps: Step S1: Select a flexible polymer as the substrate. After pretreating the substrate, deposit a uniform and dense copper cladding layer on one side of its surface to obtain a copper layer. Specifically: The coefficient of thermal expansion of the flexible polymer is in the range of 3×10⁻⁶. -6 / K to 250×10-6 / K; The flexible polymer is selected from one of polyimide (PI), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or thermoplastic polyurethane (TPU); The pretreatment includes surface cleaning and activation treatment; the activation treatment is one or more combinations of plasma treatment, ultraviolet ozone treatment, alkaline solution chemical roughening or acidic solution treatment; the deposition method is selected from magnetron sputtering, electrochemical deposition or chemical plating.

[0008] The thickness of the copper layer is 0.1-30μm.

[0009] Step S2, integrate a highly thermally conductive back layer on the other side surface of the substrate, specifically: A polymer composite material layer containing highly thermally conductive inorganic fillers is coated or printed on the other side of the substrate (i.e., the side opposite to the copper layer). This polymer composite material layer serves as the polymer matrix. Through a gradient temperature curing process, a highly thermally conductive back layer is formed that is tightly bonded to the substrate. During the curing process, the highly thermally conductive inorganic fillers form a network structure. The function of this highly thermally conductive back layer is as follows: when the copper electrode is energized and generates Joule heat, the heat is conducted through the substrate to the highly thermally conductive back layer. The network structure formed by the highly thermally conductive inorganic fillers facilitates rapid lateral diffusion, achieving temperature uniformity in the electrode area and effectively transferring heat to external heat dissipation structures or the entire device surface, thereby suppressing localized hot spots and thermal stress failure.

[0010] Furthermore, the polymer composite layer is made of one of polyimide (PI), epoxy resin (EP), silicone, or polyurethane acrylate (PUA) as the polymer matrix.

[0011] Furthermore, the polymer composite layer is made of the same type of polymer as the flexible polymer in step S1, or the difference in the coefficients of thermal expansion between the polymer composite layer and the flexible polymer is less than 20 × 10⁻⁶. -6 / K, to enhance interfacial bonding and thermomechanical matching.

[0012] Furthermore, the high thermal conductivity inorganic filler is selected from one or more of silicon carbide (SiC), boron nitride (BN), alumina (Al2O3) or carbon nanotubes (CNTs), with a particle size of 10-500 nm and an addition amount of 5-15 wt% of the polymer composite layer mass.

[0013] Furthermore, the coating method is selected from scraping or spin coating, and the printing method is selected from screen printing or solution direct writing 3D printing.

[0014] Furthermore, the gradient temperature curing process is as follows: first, pretreatment is carried out at 80-120℃ for 10-60 minutes, followed by treatment at 150℃ for 30-120 minutes to evaporate the solvent, and finally treatment is carried out at 200-300℃ for 30-120 minutes to achieve complete cross-linking and curing of the corresponding polymer.

[0015] Step S3: Based on the deformation requirements of the application scenario, a strain-adaptive pattern with stress-relieving geometry is designed on the substrate surface where the copper layer is provided in step S2. The strain-adaptive pattern is a serpentine or wavy configuration to effectively absorb external mechanical strain through structural deformation, preventing electrode breakage or peeling from the substrate. Specifically: The serpentine configuration consists of straight segments at both ends and a circular arc transition segment in the middle. The circular arc transition segments alternately combine to form a "horseshoe" or "U" shaped single-cycle unit. The arc angle of each single-cycle unit is 90°-180°, and the ratio of the arc radius to the overall length of the serpentine configuration is 0.2:1 to 1:1.

[0016] The wave-shaped configuration has a wavelength-to-amplitude ratio of 2:1 to 10:1, and the bends are transitioned by rounded arcs.

[0017] Step S4: Based on the strain-adaptive pattern designed in step S3, high-precision solution direct writing 3D printing technology is used to apply a mask pattern of curable material on the surface of the copper layer according to the designed strain-adaptive pattern. Then, the material is printed and cured to achieve additive manufacturing and finally form a precise etch barrier mask. Furthermore, if the curable material is selected from conductive paste or photoresist, then the corresponding etch barrier mask is a conductive paste mask or a photoresist mask.

[0018] Furthermore, the high-precision solution-to-write 3D printing technology specifically involves adding a curable material inside the printing syringe to achieve printing on the surface of a copper layer. Specific parameters: The printed line width is 20-200μm, controlled by printing air pressure, printing speed, printing height, and printing temperature. The printing speed is 5-50mm / s, the printing air pressure is 0.1-0.4Mpa, and the printing height is 0.05-0.1mm.

[0019] The printing syringe has a capacity of 10-30cc and a needle inner diameter of 0.01-0.1mm.

[0020] The conductive paste is silver paste or carbon paste, and its filler solid content is 30-80wt%.

[0021] The photoresist is UV-curable and has a solid content of 30-60 wt%.

[0022] Furthermore, the curing is either thermosetting or UV curing. The thermosetting temperature is 80-150℃, and the time is 10-60 minutes. The UV curing wavelength is 365-405nm, and the energy is 100-500mJ / cm². 2 .

[0023] Step S5: Selectively etch and post-process the surface on which the etch barrier mask is formed in step S4: Use an etchant to etch and remove the copper layer that is not protected by the mask, i.e. the surface of the copper layer on which the etch barrier mask is not formed. Then, select the appropriate method to remove the mask material according to the mask type. Finally, dry to obtain a complete patterned metal electrode.

[0024] Furthermore, the etching process specifically involves using an etching solution selected from a copper chloride-hydrochloric acid system, a sulfuric acid-hydrogen peroxide system, or a citric acid-persulfate system. The etching time is 3-30 minutes, and the temperature is 20-40°C. More specifically, the citric acid-persulfate system is preferred, as it exhibits relatively low corrosivity and metal ion residue, facilitating subsequent wastewater treatment.

[0025] Furthermore, the removal of the mask material specifically involves the following steps: For conductive paste masks, a rinsing solution containing an ester solvent is used for cleaning. The ester solvent is one of divalent ester (DBE), ethyl acetate (EA), propylene glycol methyl ether acetate (PMA), or ethylene glycol monobutyl ether (BCS), with a volume concentration of 10-50%. For photoresist masks, one of N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), or acetone is used for dissolution and removal, with a volume concentration of 80-100%.

[0026] Furthermore, the drying method is one of the following: drying with an inert gas (such as nitrogen, argon, etc.), drying in an oven, or air drying, with a drying temperature of 25-80℃.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Thermal-mechanical synergistic reliability design: By printing a high thermal conductivity back layer in step S2 to uniformly diffuse the Joule heat generated by the copper electrode during operation, local hot spots and thermal stress are suppressed; combined with the serpentine / wave pattern in steps S3 and S4 to absorb mechanical bending and tensile strain, the durability of the electrode under working conditions is synergistically improved from both thermal and mechanical dimensions.

[0028] (2) High-precision patterning and process flexibility: In the core process steps S2, S3 and S4, high-precision 3D printing technology is used to directly form mask patterns on the surface of the copper layer without the need for photolithography mask. It supports complex structures and rapid prototyping customization, and the line width of the pattern can be flexibly adjusted in the range of 20-200μm.

[0029] (3) Interface thermal matching optimization: The thermal expansion coefficient of the high thermal conductivity backing layer (10-30ppm / K) is controlled by gradient curing process, so that it is between that of copper and flexible substrate, thereby reducing the interface shear stress under thermal cycling and improving long-term reliability. Attached Figure Description

[0030] Figure 1 This is a flowchart of the flexible substrate copper electrode patterning preparation method of the present invention; Figure 2 This is a schematic diagram of the overall three-layer structure after processing in step S3 of Example 1; Figure 3 This is a schematic diagram (top view) of the electrode after patterning in step S3 of Example 1. Figure 3 (a) in the diagram is the model diagram; Figure 3 (b) in the diagram is a structural schematic. Figure 4 The image shows the thermal distribution of the thermoelectric device before and after the addition of the high thermal conductivity backing layer, captured by a FLIR infrared thermal imager in Example 1. Figure 4 (a) in the figure is the thermal distribution diagram of the thermoelectric device before the addition of a high thermal conductivity backing layer; Figure 4 (b) in the figure is the thermal distribution diagram of the thermoelectric device after adding a high thermal conductivity backing layer.

[0031] Figure 5 Apply a size of 1E-05N to a conventionally shaped flexible electrode. Simulation diagram of stress distribution after torsional stress; Figure 6 In step S4 of embodiment 1 of the present invention, a serpentine electrode with a size of 1E-05N is applied. Simulation diagram of stress distribution after torsional stress; In the figure: 1 is the copper electrode layer; 2 is the flexible polymer layer; 3 is the high thermal conductivity back layer. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments.

[0033] Example 1 A method for patterning copper electrodes on a flexible substrate with an integrated high thermal conductivity backing layer, the flowchart of which is shown below. Figure 1 As shown, the method for fabricating patterned copper electrodes on a flexible substrate includes the following steps: Step S1, Substrate Treatment and Deposition: Select a substrate with a thermal expansion coefficient of 20×10⁻⁶. -6A polyimide film of / K was used as the substrate. Surface cleaning and activation were performed sequentially: fingerprints and oil were removed using an alkaline degreaser at 50°C, followed by treatment with 3mol / L potassium hydroxide (KOH) for 6 minutes to increase surface polarity; activation was then performed at 25°C using a colloidal palladium solution for 4 minutes. A copper layer was deposited on one side of the substrate using a chemical copper plating process: the plating solution used 12g / L copper sulfate pentahydrate as the main salt, glyoxylic acid as the reducing agent, and potassium sodium tartrate as the complexing agent, with the pH adjusted to 12.0. Copper plating was performed at 55°C to obtain a uniform and dense copper layer with a thickness of 1μm. This layer was then thickened to the target thickness of 25μm using an electroplating process, and finally cleaned and dried.

[0034] Step S2, preparation of high thermal conductivity composite ink: using polyimide solution as matrix, add 10wt% silicon carbide nanoparticles with a particle size of 40–100nm as thermally conductive filler, and obtain high thermal conductivity composite ink by physical blending and magnetic stirring for 30 minutes.

[0035] Step S3, Preparation of the high thermal conductivity back layer: On the back side of the substrate without copper coating, a solution-written 3D printing method was used to form the back layer: needle inner diameter 0.05 mm, room temperature 25℃, printing air pressure 0.2 MPa, printing speed 20 mm / s. After printing, a gradient temperature curing process was performed: 80℃ for 30 minutes, 120℃ for 20 minutes, and 200℃ for 60 minutes to obtain a high thermal conductivity back layer that is tightly bonded to the substrate.

[0036] In step S3 of this embodiment, the schematic diagram of the overall three-layer structure after processing is shown below. Figure 2 As shown. A schematic diagram of the patterned electrodes is shown below. Figure 3 As shown, Figure 3 (a) in the diagram is the model diagram. Figure 3 (b) in the diagram is a structural schematic. Figure 4 This is a thermal distribution map of the thermoelectric device before and after the addition of a high thermal conductivity backing layer, captured by the FLIR infrared thermal imager in Example 1. Figure 4 (a) in the figure shows the thermal distribution of the thermoelectric device before the addition of a high thermal conductivity backing layer. Figure 4 (b) shows the thermal distribution of the thermoelectric device after adding a high thermal conductivity backing layer; "Highest" displays the highest temperature in the screen or selected area, which can intuitively reflect the highest intensity of the hot spot in the area; "Point" displays the real-time temperature at the crosshair in the center of the screen; "Δ Point" displays the temperature difference between two measurement points. The color scale bar is located on the far right of the image, which establishes the mapping relationship between color and temperature. This invention provides a unified visual comparison benchmark, where dark blue represents low temperature <20.0℃, and bright white / red represents high temperature >24.7℃.

[0037] Step S4, Strain-adaptive electrode pattern design: adopts a serpentine stress-relieving structure with a single-cycle bending angle of 180°, and a rounded transition at the bend, with the radius of the rounded arc being 0.5:1 to the overall length of the electrode.

[0038] Step S5, 3D printing mask and selective etching: A mask is printed on the copper layer surface using UV-curable photoresist, and then cured with 365nm UV light at an energy of 300mJ / cm². 2 The exposed copper layer was removed by etching with a sulfuric acid-hydrogen peroxide etching solution at 35°C for 8 minutes. The photoresist mask was then completely dissolved and removed with acetone, followed by natural drying in an oven at 60°C to obtain a flexible patterned copper electrode with an integrated high thermal conductivity back layer.

[0039] Figure 6 In step S4 of Example 1, the serpentine electrode with a size of 1E-05N is applied. Simulation diagram of stress distribution after torsional stress; Figure 5 Apply a size of 1E-05N to a conventionally shaped flexible electrode. Simulation diagram of stress distribution after torsional stress; comparison Figure 5 and Figure 6 It can be seen that the serpentine electrode of the present invention has a more uniform stress distribution, which effectively solves the problem of excessive stress at both ends of conventional electrodes.

[0040] Example 2 A method for patterning copper electrodes on a flexible substrate with an integrated high thermal conductivity backing layer, the flowchart of which is shown below. Figure 1 As shown, the method for fabricating patterned copper electrodes on a flexible substrate includes the following steps: Step S1, Substrate treatment and deposition: Select a thermal expansion coefficient of 16×10⁻⁶. -6 A polyethylene naphthalate (PEN) film of / K was used as a flexible substrate. The surface was treated with UV-Ozone irradiation for 15 minutes to remove organic contaminants and increase surface energy. A 10-50 nm titanium layer was deposited as a binder layer using magnetron sputtering, followed by a 100-200 nm copper layer as a seed layer. The copper layer was prepared using an acidic copper sulfate electroplating system: the electrolyte contained 60 g / L copper sulfate, 180 g / L sulfuric acid, and 200 ppm polyethylene glycol (PEG-6000), with a current density of 2.5 A / dm³. 2 A uniform copper layer with a thickness of 10μm was obtained by constant current electroplating at 25℃ for 20 minutes.

[0041] Step S2, preparation of high thermal conductivity composite ink: using epoxy resin (EP) that matches the substrate as the matrix, add boron nitride particles with a mass fraction of 25 wt% and a particle size of 50–100 nm, and blend to obtain high thermal conductivity composite ink.

[0042] Step S3, Preparation of the high thermal conductivity back layer: 3D printing is performed on the back side of the substrate without copper coating: needle inner diameter 0.1 mm, air pressure 0.1 MPa, printing speed 50 mm / s. Constant temperature curing is performed, holding at 80℃ for 30 minutes to achieve complete curing, forming the high thermal conductivity back layer.

[0043] Step S4, Strain-adaptive electrode pattern design: A wave-shaped stress-relieving structure design is adopted, with a wavelength to amplitude ratio of 5:1.

[0044] Step S5, Mask Curing and Selective Etching: A mask is printed on the copper layer surface using UV-curable photoresist, and then cured with 365nm UV light at an energy of 300mJ / cm². 2 The exposed copper layer was removed by etching with a sulfuric acid-hydrogen peroxide etching solution at 35°C for 3 minutes. The photoresist mask was then completely dissolved and removed using N-methylpyrrolidone (NMP), and dried in an oven at 60°C to obtain a flexible patterned copper electrode.

[0045] Example 3 A method for patterning copper electrodes on a flexible substrate with an integrated high thermal conductivity backing layer, the flowchart of which is shown below. Figure 1 As shown, the method for fabricating patterned copper electrodes on a flexible substrate includes the following steps: Step S1, Substrate treatment and deposition: Select a thermal expansion coefficient of 60×10 -6 / K polyethylene terephthalate (PET) film was used as a flexible substrate. First, it was placed in a vacuum chamber for in-situ Ar plasma cleaning for 10 minutes to remove surface organic contaminants and increase surface energy through physical bombardment. Subsequently, a metal layer was deposited using DC magnetron sputtering technology, with a system base vacuum level better than 5 × 10⁻⁶. -4 To enhance film-substrate adhesion, a Ti adhesion layer with a thickness of approximately 20 nm was first sputtered onto the substrate surface; then, using high-purity copper as the target material, a film was sputtered at a working pressure of 0.5 Pa and a power density of 5.0 W / cm². 2 Under the condition of continuous deposition, by controlling the sputtering time, a uniform and dense copper layer with a thickness of 3 μm was obtained on the surface of the PET substrate.

[0046] Step S2, preparation of high thermal conductivity composite ink: using polyurethane acrylate (PUA) that matches the substrate as the matrix, add alumina (Al2O3) particles with a mass fraction of 30wt% and a particle size of 50–100nm, and blend to obtain high thermal conductivity composite ink.

[0047] Step S3, Preparation of the high thermal conductivity back layer: 3D printing is performed on the back side of the substrate without copper coating: needle inner diameter 0.15mm, air pressure 0.3MPa, printing speed 25mm / s. Gradient temperature curing is performed: 80℃ for 30 minutes, 120℃ for 60 minutes, to obtain a high thermal conductivity back layer that is tightly bonded to the substrate.

[0048] Step S4, Strain-adaptive electrode pattern design: A wave-shaped stress-relieving structure design is adopted, with a wavelength to amplitude ratio of 4:1.

[0049] Step S5, Mask Curing and Selective Etching: A mask pattern is formed on the copper layer surface using conductive silver paste with a solid content of 45% via solution-based direct writing 3D printing, and then cured at 120°C for 30 minutes. A citric acid-persulfate etching solution is used to etch the copper layer at 30°C for 10 minutes to remove the unmasked copper layer. The silver paste mask is removed using a 30% (v / v) divalent ester (DBE) rinsing solution, and after nitrogen drying, a flexible patterned copper electrode with an integrated high thermal conductivity backing layer is obtained.

[0050] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for fabricating patterned copper electrodes on a flexible substrate with an integrated high thermal conductivity back layer, characterized in that, The method for fabricating patterned copper electrodes on flexible substrates includes the following steps: Step S1: Select a flexible polymer as the substrate, pretreat the substrate, and deposit copper on one side of its surface to obtain a copper layer. Step S2, integrate a highly thermally conductive back layer on the other side surface of the substrate, specifically: A polymer composite material layer containing high thermal conductivity inorganic filler is coated or printed on the other side surface of the substrate. The polymer composite material layer serves as the polymer matrix and is cured by gradient temperature rise process to form a high thermal conductivity back layer that is tightly bonded to the substrate. During the temperature rise curing process, the high thermal conductivity inorganic filler forms a network structure. Step S3: Based on the deformation requirements of the application scenario, a strain-adaptive pattern with stress-relieving geometry is designed on the substrate surface where the copper layer is provided in step S2. Step S4: Based on the strain-adaptive pattern designed in step S3, high-precision solution direct writing 3D printing technology is used to apply a mask pattern of curable material on the surface of the copper layer according to the designed strain-adaptive pattern. Then, the material is printed and cured to achieve additive manufacturing and finally form a precise etch barrier mask. Step S5: Selectively etch and post-process the surface on which the etching barrier mask is formed in step S4: Use an etching solution to etch away the copper layer that is not protected by the mask, select the appropriate method to remove the mask material according to the mask type, and finally dry to obtain a complete patterned metal electrode.

2. The method for fabricating a patterned copper electrode on a flexible substrate with an integrated high thermal conductivity back layer according to claim 1, characterized in that, In step S1: The coefficient of thermal expansion of the flexible polymer ranges from 3 x 10 -6 / K to 250 x 10 -6 / K; The pretreatment includes surface cleaning and activation treatment; The activation treatment is one or more of the following: plasma treatment, ultraviolet ozone treatment, alkaline solution chemical roughening, or acidic solution treatment. The deposition method is selected from magnetron sputtering, electrochemical deposition, or chemical plating. The thickness of the copper layer is 0.1-30 μm.

3. The method for fabricating a patterned copper electrode on a flexible substrate with an integrated high thermal conductivity back layer according to claim 2, characterized in that, In step S1, the flexible polymer is selected from one of polyimide (PI), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or thermoplastic polyurethane (TPU).

4. The method for fabricating a patterned copper electrode on a flexible substrate with an integrated high thermal conductivity back layer according to claim 3, characterized in that, In step S2: The high thermal conductivity inorganic filler is selected from one or more of silicon carbide (SiC), boron nitride (BN), alumina (Al2O3), or carbon nanotubes (CNTs), with a particle size of 10-500 nm, and is added at a rate of 5-15 wt% of the polymer composite layer mass. The polymer composite layer is made of the same type of polymer as the flexible polymer in step S1, or the difference in the coefficient of thermal expansion between the polymer composite layer and the flexible polymer is less than 20 × 10⁻⁶. -6 / K; The coating method is selected from scraping or spin coating, and the printing method is selected from screen printing or solution direct writing 3D printing; The gradient temperature curing process is as follows: first, pretreatment is carried out at 80-120℃ for 10-60 minutes, followed by treatment at 150℃ for 30-120 minutes to evaporate the solvent, and finally treatment is carried out at 200-300℃ for 30-120 minutes to achieve complete cross-linking and curing of the corresponding polymer.

5. The method for fabricating a patterned copper electrode on a flexible substrate with an integrated high thermal conductivity back layer according to claim 4, characterized in that, In step S2, the polymer composite layer is made of one of polyimide (PI), epoxy resin (EP), silicone, or polyurethane acrylate (PUA) as the polymer matrix.

6. The method for patterning a flexible substrate copper electrode with an integrated high thermal conductivity back layer according to claim 5, characterized in that, In step S3, the strain-adaptive pattern is a serpentine or wavy configuration, specifically: The serpentine configuration consists of straight segments at both ends and a circular arc transition segment in the middle. The circular arc transition segments are alternately combined to form a "horseshoe" or "U" shaped single-cycle unit. The arc angle of each single-cycle unit is 90°-180°, and the ratio of the arc radius to the overall length of the serpentine configuration is 0.2:1 to 1:

1. The wave-shaped configuration has a wavelength-to-amplitude ratio of 2:1 to 10:1, and the bends are transitioned by rounded arcs.

7. The method for fabricating a patterned copper electrode on a flexible substrate with an integrated high thermal conductivity back layer according to claim 6, characterized in that, In step S4: If the curable material is selected from conductive paste or photoresist, then the etching barrier mask is a conductive paste mask or a photoresist mask. The high-precision solution direct writing 3D printing technology specifically involves adding a curable material into the printing syringe to achieve printing on the surface of a copper layer. The curing process is either thermosetting or UV curing, with a thermosetting temperature of 80-150℃ and a curing time of 10-60 minutes. The UV curing wavelength is 365-405nm, and the energy is 100-500mJ / cm. 2 .

8. The method for patterning a flexible substrate copper electrode with an integrated high thermal conductivity back layer according to claim 7, characterized in that, The specific parameters of the high-precision solution direct-write 3D printing technology are as follows: The line width of the print is 20-200μm, the printing speed is 5-50mm / s, the printing air pressure is 0.1-0.4Mpa, and the printing height is 0.05-0.1mm. The printing syringe specifications are 10-30cc, and the needle inner diameter is 0.01-0.1mm; The conductive paste is either silver paste or carbon paste, and its filler solid content is 30-80 wt%. The photoresist is UV-curable and has a solid content of 30-60 wt%.

9. The method for patterning a flexible substrate copper electrode with an integrated high thermal conductivity back layer according to claim 8, characterized in that, In step S5: The etching solution is one of the following: copper chloride-hydrochloric acid system, sulfuric acid-hydrogen peroxide system, or citric acid-persulfate system. The etching time is 3-30 minutes and the temperature is 20-40℃. The specific methods for removing mask materials are as follows: For conductive paste masks, use a rinsing solution containing ester solvents for cleaning; for photoresist masks, use N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), or acetone for dissolution and removal. The drying method is one of inert gas blowing, oven drying, or natural air drying, and the drying temperature is 25-80℃.

10. The method for fabricating a patterned copper electrode on a flexible substrate with an integrated high thermal conductivity back layer according to claim 9, characterized in that, The ester solvent is one of the following: divalent ester DBE, ethyl acetate EA, propylene glycol methyl ether acetate PMA, or ethylene glycol monobutyl ether BCS.

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