High temperature resistant NANO copper by laser direct drawing, method for manufacturing the same, and use

Abstract

To provide high temperature resistant nano copper by laser direct drawing; method for manufacturing the same; and use.SOLUTION: High temperature resistant nano copper is obtained by heating and agitating an alcoholic solvent, an organic dispersant, an organic auxiliary agent and formate to obtain a precursor liquid, adding nano copper oxide to the precursor liquid and subjecting the mixture to ultrasonic dispersion to obtain nano copper oxide ink, applying nano copper oxide ink to a pretreated substrate to obtain a nano copper oxide film and subjecting the nano copper oxide film to laser direct drawing induced passivation / photothermal reduction sintering.EFFECT: Nano copper oxide ink simple in manufacturing, stored for a long time without being affected by oxidization and suitable for various manufacturing processes, such as a coating method, a painting method and a printing method is high in processing efficiency on the basis of laser direct drawing and can unify many performances by one step to the high temperature resistant nano copper.SELECTED DRAWING: Figure 17

Description

[Technical Field]

[0001] The present invention relates to the field of nano-copper production, and in particular to high temperature resistant nano-copper by laser direct writing, its production method and use. [Background technology]

[0002] Copper is a metal widely used in human society. Its unique properties and advantages make it a key player in fields such as construction, electrical engineering, communications, energy, and medicine. Nanocopper, in particular, is a promising material for functional electronics applications, such as conductive electrodes, transistors, sensors, and electrochemical batteries, due to its favorable electrical and thermal properties and economic advantages. However, copper is highly susceptible to oxidation under high-temperature conditions, resulting in a deterioration of its metallic properties and reduced electrical conductivity, greatly limiting its applications. Nanocopper has a larger specific surface area than bulk copper and is more susceptible to oxygen gas reactions. Therefore, the oxidation failure problem of nanocopper is much more serious than that of bulk copper.

[0003] To improve the high-temperature oxidation resistance and thermal stability of nano-copper, various antioxidant treatment methods have been developed to date.

[0004] (1) Surface coating: Coating the surface of nano-copper with a layer of inert material (e.g., graphene, graphene oxide, or precious metals such as gold, silver, or platinum) can effectively block direct contact between oxygen gas and nano-copper.

[0005] (2) Surface modification: By adsorbing or chemically bonding some organic molecules / polymers to the surface of nano-copper, these react with the nano-copper to form stable compounds, slowing down the oxidation rate at high temperatures.

[0006] (3) Alloying: By combining nano-copper with other metals (e.g., nickel, tin, aluminum, manganese) to form an alloy, the melting point of nano-copper is increased, thereby improving its oxidation resistance at high temperatures.

[0007] (4) Atmosphere control: During the sintering or high-temperature treatment of nanocopper, oxidation can be effectively prevented by controlling the treatment atmosphere (e.g., inert / reducing gas protection, vacuum conditions).

[0008] Of the above processing methods, methods (1) and (2) have relatively significant high-temperature oxidation resistance, but are relatively expensive, have relatively complex process flows, and affect the electrical and thermal properties of nanocopper to some extent. Method (3) can improve oxidation resistance, but also changes other physical and chemical properties of nanocopper, resulting in it no longer meeting the original application requirements. Method (4) is mainly applicable to specific processing environments, and in practical applications, it is difficult to maintain for long periods of time and requires expensive equipment, increasing the complexity and cost of operation.

[0009] Prior art techniques for method (1), such as patent number CN202111501706.2, entitled "Method for Producing an Oxidation-Resistant Copper-Based Surface-Enhanced Raman Scattering Substrate," involve melt spinning and dealloying to produce a bicontinuous nanoporous copper strip. The nanoporous copper is then pickled to remove the surface oxide layer. Finally, a graphene oxide solution is spin-coated onto the nanoporous copper surface, which is then immediately transferred to a tube furnace and thermally reduced in a hydrogen and argon gas atmosphere to obtain nanoporous copper coated with an ultrathin layer of reduced graphene oxide, further slowing its oxidation and ensuring the stability of the reduced graphene oxide / nanoporous copper composite substrate in Raman detection. While this invention offers good stability and high reproducibility, the process steps are complex and require inert gas operation, resulting in relatively harsh reaction conditions.

[0010] In the prior art, method (1) has been described, for example, in Patent No. CN201710343566.8, entitled "Novel Antioxidant Nanocopper Solder Paste, Manufacturing Method and Use Thereof," which uses a magnetron sputtering process to uniformly coat the surface of nanocopper powder with a metal film (gold or silver). The composition of a conventional nanocopper solder paste is then combined with an appropriate amount of molding aids to produce a novel antioxidant and crack-resistant nanocopper solder paste. This invention prevents oxidation by coating the nanocopper with an inert metal layer of gold or silver, allowing it to be used for long periods at high temperatures without problems. However, it significantly increases material costs, limiting its large-scale application.

[0011] In the prior art, for method (2), for example, in Patent No. CN201710752263.1, "Method for Producing Antioxidant Copper Nanowires," copper nanowires are first added to a dispersant, followed by the addition of a polar organic solvent and / or water and mixing to obtain a copper nanowire dispersion. Next, an antioxidant is added to the copper nanowire dispersion and mixed to obtain a mixture. The mixture is then placed in a pressurized, heated, and sealed system to react. Finally, the mixture is cooled, separated into liquid and solid, and washed to obtain copper nanowires with an antioxidant surface treatment, i.e., antioxidant copper nanowires. While this invention is simple and inexpensive, the operating process is relatively complicated, the reaction time is relatively long, and sealed reaction conditions involving pressurization and heating are required, making it unsuitable for efficient processing at room temperature.

[0012] In the prior art, method (2) is described, for example, in Patent No. CN202110912124.7, entitled "Antioxidant Copper Film / Copper Wire, Manufacturing Method and Use Thereof." Antioxidant copper powder, an alcohol-based solvent, an alcoholamine-based solvent, a resin, and auxiliary agents are ground and mixed, and then degassed to obtain an antioxidant copper paste. The antioxidant copper paste is applied to a substrate, dried, and pre-cured under an inert atmosphere to obtain copper film precursor 1 / copper wire precursor 1. Copper film precursor 1 / copper wire precursor 1 is cured under an inert atmosphere to obtain copper film precursor 2 / copper wire precursor 2. Copper film precursor 2 / copper wire precursor 2 is then added to a compound containing a thiol group or a disulfide bond and treated to obtain an antioxidant copper film / copper wire. The copper film / copper wire obtained by this invention has excellent antioxidation properties, but requires an inert atmosphere to achieve high conductivity, making the manufacturing conditions relatively strict.

[0013] Prior art techniques for method (3), such as patent number CN201410532942.4, entitled "Method for Producing Copper-Nickel Alloy Nanoparticles," involve preparing a mixture of copper nitrate trihydrate and nickel nitrate hexahydrate, adding a complexing agent and a dispersing agent while stirring (the molar ratio of copper nitrate to complexing agent is 1:0.5 to 1:4, and the molar ratio of copper nitrate to dispersing agent is 1:1 to 1:2). The resulting solution is then dried in an oven at 160-180°C to form a moisture-free, porous, dry gel. The dried gel is then calcined in an argon atmosphere at 500-700°C for 2-5 hours to obtain copper-nickel alloy nanoparticles. While this invention has the advantages of readily available raw materials and a relatively high yield, the manufacturing process requires a high-temperature environment and an inert atmosphere, limiting its large-scale application.

[0014] In the prior art, method (3) has been discussed, for example, in Patent No. CN201110055004.6, entitled "Nano-copper-tin alloy conductive ink, its manufacturing method, and its use." By using a nano-copper-tin alloy instead of a nano-copper-silver alloy as the conductive filler in the conductive ink, the sintering temperature of the conductive ink is reduced. This not only improves the sintering temperature of the conductive ink, but also improves the oxidation resistance during sintering, the mechanical properties, and solderability of the conductive circuit formed by sintering, and avoids the problem of silver ion migration compared to nano-copper-silver alloy conductive inks. Furthermore, the nano-copper-tin alloy is doped with rare earth metal elements, increasing the number of grain boundaries and the electron scattering rate, thereby improving its electrical conductivity compared to nano-copper alloys. Meanwhile, the raw material costs of the conductive ink are reduced. However, the addition of tin lowers the melting point of the nano-copper-tin alloy, which is detrimental to its oxidation resistance under long-term high-temperature conditions.

[0015] In the prior art, method (4), for example, in Patent No. CN201910399914.2, "Method for Producing Antioxidant Micro-Nano Copper Material," uses a micro-nano copper production device to produce micro-nano copper powder. An organic coating agent is placed in the vacuum chamber of the in-situ coating device, and the organic coating agent in the vacuum chamber is heated to sublimate or vaporize. An inert gas is introduced into the production system, and the micro-nano copper powder is introduced into the vacuum chamber of the in-situ coating device along with the inert gas. The sublimated or vaporized organic coating agent contacts and coats the surface of the micro-nano copper particles. The vacuum heating and inert atmosphere used in this invention form a good organic coating layer on the surface of the micro-nano copper ions, significantly improving the antioxidation and dispersibility of the micro-nano copper particles and reducing their surface activity. However, the specific processing environment of the entire process significantly increases costs and does not meet the requirements for practical application.

[0016] Prior art techniques for method (4), such as patent number CN202111250495.X's "Anti-oxidation superhydrophobic copper film and its manufacturing method," use copper nanoclusters produced by decomposing an organometallic precursor as a catalyst to decompose a liquid organic precursor into graphite carbon. The graphite carbon is concentrated on the surface of the copper nanoclusters, forming copper-carbon core-shell particles. Numerous copper-carbon crystal grains accumulate on the substrate surface, forming an anti-oxidation superhydrophobic copper film. This invention primarily uses chemical vapor deposition to form an anti-oxidation copper carbon film on the substrate surface, and the relatively rough nanostructured surface formed by the deposition achieves superhydrophobic properties. While the overall process is easy to control and has good reproducibility, it requires strict reaction conditions (controlling an inert atmosphere of hydrogen and argon gas, a reaction temperature of 400-600°C, and a reaction pressure of 1000-9000 Pa), which inevitably leads to cost-effectiveness issues.

[0017] Therefore, developing an anti-oxidation surface treatment method for high-temperature resistant nanocopper that is easy to fabricate, efficient to process, highly compatible, and cost-effective is a current technical challenge for solving the applications of nanocopper in functional electronics fields such as conductive electrodes, transistors, sensors, and electrochemical batteries. Summary of the Invention [Problem to be solved by the invention]

[0018] SUMMARY OF THE INVENTION In view of the shortcomings of the prior art, the object of the present invention is to provide a laser direct write high temperature resistant nano copper, a method for producing same and uses thereof, which is produced using laser direct write induction. [Means for solving the problem]

[0019] In the present invention, the method for producing high temperature resistant nano copper by laser direct drawing mainly includes: (1) a step of uniformly heating and stirring an alcohol-based solvent, an organic dispersant, an organic auxiliary, and an appropriate amount of formate to obtain a precursor solution; Step (2) of adding an appropriate amount of nano-copper oxide to the precursor solution and dispersing it sufficiently by ultrasonic waves to obtain nano-copper oxide ink; Step (3) of applying the nano-copper oxide ink onto the pre-treated substrate and drying it by heating to obtain a nano-copper oxide film; and (4) subjecting the nano-copper oxide film to laser direct writing induced passivation / photothermal reduction sintering to obtain high temperature resistant nano-copper.

[0020] The alcohol-based solvent in step (1) is at least one selected from monohydric alcohols, dihydric alcohols, and polyhydric alcohols, the organic dispersant is at least one selected from polyacrylamide-based organic high polymers, polyethylene oxide-based organic high polymers, tannin, and lignin, but is not limited thereto, and the organic auxiliary is a compound represented by the chemical formula C n H 2n+1 The organic amide is at least one selected from alkylamides satisfying the condition NO (1≦n≦5). The formate is at least one selected from lithium formate, beryllium formate, sodium formate, magnesium formate, potassium formate, calcium formate, iron formate, manganese formate, cobalt formate, nickel formate, copper formate, zinc formate, barium formate, and ammonium formate. The heating and stirring is carried out at a temperature of 50 to 70°C, a rotation speed of 600 to 1500 rpm, and a time of 2 to 20 hours.

[0021] The nanocopper oxide in step (2) is at least one selected from copper oxide nanoparticles, copper oxide nanowires, copper oxide nanosheets, copper oxide nanorods, and copper oxide nanoshuttles. The ultrasonic dispersion is performed at a real-time temperature of 50-60°C, with an ultrasonic pulse width of 0.1 s and an ultrasonic duration of 0.1-2 h. Furthermore, the ultrasonic dispersion can be achieved by adding the nanocopper oxide in small amounts multiple times. Direct ultrasonic treatment after adding all the nanocopper oxide to the precursor solution can cause severe aggregation and poor dispersion of the copper oxide nanowires, preventing successful laser-induced direct writing. The nanocopper oxide ink contains 43.0-50.4 wt% nanocopper oxide, 37.1-50.4 wt% alcohol-based solvent, 3.4-5.3 wt% organic dispersant, 0.0-9.5 wt% organic additive, and 1.3-2.0 wt% formate. The nanocopper oxide ink has long shelf life, is resistant to oxidation, and is suitable for various manufacturing processes, including printing, coating, and imprinting.

[0022] The coating method in step (3) is at least one selected from, but not limited to, spin coating, spray coating, blade coating, brush coating, droplet coating, and screen printing. The pretreatment is oxygen plasma surface treatment, and the treatment time is 60 to 150 seconds. The substrate includes a flexible substrate and a rigid substrate. The flexible substrate is at least one selected from, but not limited to, polyimide (PI), polyethylene terephthalate (PET), polyvinyl alcohol (PVA), and polyethylene naphthalate (PEN). The rigid substrate is at least one selected from, but not limited to, polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polysulfone (PSF), liquid crystal polymer (LCP), glass, silicon wafer, and ceramic. The heat drying is performed at a temperature of 50 to 80°C for 2 to 12 hours.

[0023] The laser in step (4) is a continuous green light with a wavelength of 532 nm, and the laser direct writing induced passivation / photothermal reduction sintering has a power of 100-400 mW, a speed of 20-200 mm / s, and a scanning period of 20-40 μm.

[0024] The surface of the high-temperature resistant nano-copper, when formate passivation is induced by direct laser writing, has good oxidation resistance and thermal stability, as well as excellent electrical conductivity.

[0025] The present invention also provides a fully laser in-situ direct-write integrated sensor system, including a special engineering plastic substrate, a high-temperature-resistant nano-copper interconnect circuit, a laser-induced graphene temperature sensor, a voltage divider, an analog-to-digital converter (ADC), a microcontroller (MCU), and a low-dropout linear regulator (LDO), where the remaining components are connected via the high-temperature-resistant nano-copper interconnect circuit to achieve the integrated sensor function, and the high-temperature-resistant nano-copper interconnect circuit and the laser-induced graphene temperature sensor are both formed in-situ on the special engineering plastic substrate by full laser direct-write techniques (laser direct-write induced passivation / photothermal reduction sintering and laser-induced carbonization), and the high-temperature-resistant nano-copper is manufactured by any of the above-mentioned methods for manufacturing high-temperature-resistant nano-copper. The special engineering plastic substrate is typically one or more of polyimide (PI), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polysulfone (PSF), and liquid crystal polymer (LCP), and is preferably polyether ether ketone (PEEK) or polyphenylene sulfide (PPS) because they are particularly advantageous for a wide range of applications in fields such as aerospace, automobiles, and electronics. [Effects of the Invention]

[0026] Laser direct-write passivation, based on laser processing, refers to the use of high-energy laser irradiation to induce a formate passivation reaction on the surface of nanocopper, causing the copper ions on the surface of the nanocopper and formate to form a copper formate dimer complex, forming a stable and effective antioxidant coordination passivation layer, thereby improving the surface properties of the nanocopper, significantly improving its antioxidant properties and thermal stability, and achieving high-temperature-resistant nanocopper. In this invention, laser direct-write passivation has the following advantages:

[0027] (1) Efficient processing: The laser direct-write induced passivation process is very fast, concentrating high-intensity energy in a short time, forming a reaction temperature field, and completing the formate passivation of the nano-copper surface. Compared with traditional chemical passivation and physical coating methods, laser direct-write induced passivation significantly shortens the production cycle and improves processing efficiency.

[0028] (2) Patterning control: Laser direct writing induced passivation can precisely control the processing area. Its typical patterning capability enables localized passivation of the nanocopper surface, which can precisely improve the high-temperature oxidation resistance of specific areas of the nanocopper.

[0029] (3) No additional treatment required: Laser direct writing induced passivation does not require pre-treatment, post-treatment, or external chemical reagents and can be performed directly in an air environment. Since harsh reaction conditions such as vacuum or inert atmosphere are not required, the treatment process is simple, significantly reducing manufacturing costs and making it an environmentally friendly anti-oxidation surface treatment method.

[0030] (4) Multi-functional integration: In laser direct writing induced passivation, copper oxide nanoparticles are reduced and sintered to form nanocopper through one-step direct writing, which improves the oxidation resistance of nanocopper, enhances its thermal stability in high-temperature environments, and endows nanocopper with excellent electrical conductivity.

[0031] (5) Strong compatibility: Laser direct writing induced passivation is not limited by the shape and complexity of nano-copper materials and is suitable for multi-scale nano-copper. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is an optical photograph of the prepared precursor solution. [Figure 2] 1 is an optical photograph of the prepared nano-copper oxide ink. [Figure 3] 1 is an optical photograph of the fabricated high-temperature resistant nano-copper electrode with a serpentine pattern. [Figure 4] The change in relative resistance of nanocopper with various concentrations of sodium formate when heated at 170°C for various times in a dry air atmosphere. [Figure 5] 10 shows the change in resistance of nanocopper after laser surface treatment with various concentrations of copper oxide nanowires. [Figure 6] Optical image of nano copper at laser power of 250 mW. [Figure 7] Optical image of nano copper at laser power of 100 mW. [Figure 8] Optical image of nano-copper at laser power of 400mW. [Figure 9] The change in resistance of nano-copper surface treated with different laser powers. [Figure 10] Figure 10 shows the change in relative resistance with time at 80°C for nano-copper surface treated with different laser powers. [Figure 11] 1 is an optical image of nano-copper when the laser line scanning period is 15 μm. [Figure 12] 1 is an optical image of nano-copper when the laser line scanning period is 45 μm. [Figure 13] The resistance change of nano-copper surface treated with various laser line scanning periods. [Figure 14] Figure 10 shows the relative resistance change with time at 170°C for nanocopper treated with different laser line scan periods. [Figure 15] Figure 1 shows the change in relative resistance with time at 170°C for nanocopper (LIP-Cu) and sodium formate-free nanocopper (Cu). [Figure 16]Figure 1 shows the change in relative resistance with time at 120°C for nanocopper (LIP-Cu) and sodium formate-free nanocopper (Cu). [Figure 17] The change in relative resistance of nanocopper (LIP-Cu) and sodium formate-free nanocopper (Cu) as the temperature is gradually increased from 30°C to 170°C. [Figure 18] 1 is an optical photograph of a fully laser in-situ direct writing integrated sensor system. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will be specifically described below with reference to the drawings through examples, which are provided to more clearly illustrate the technical solutions of the present invention and are therefore provided as examples only and cannot limit the scope of protection of the present invention. The first aspect of the present invention mainly comprises: (1) a step of uniformly heating and stirring an alcohol-based solvent, an organic dispersant, an organic auxiliary, and an appropriate amount of formate to obtain a precursor solution; Step (2) of adding an appropriate amount of nano-copper oxide to the precursor solution and dispersing it sufficiently by ultrasonic waves to obtain nano-copper oxide ink; Step (3) of applying the nano-copper oxide ink onto the pre-treated substrate and drying it by heating to obtain a nano-copper oxide film; A method for producing heat-resistant nanocopper by laser direct writing is proposed, which includes step (4) of subjecting the nanocopper oxide film to laser direct writing induced passivation / photothermal reduction sintering to obtain heat-resistant nanocopper.

[0034] Example 1: S1: 0.5 g of polyvinylpyrrolidone and 0.15 g of sodium formate were weighed and mixed with 3.0 mL of ethylene glycol, and the mixture was uniformly heated at 60° C. and 1200 rpm and stirred for 6 hours to obtain a precursor solution. S2: 1.5 g of copper oxide nanowires (40 nm) was weighed and added to the precursor solution. Ultrasonic dispersion was performed thoroughly at an ultrasonic real-time temperature of 55°C, an ultrasonic pulse width of 0.1 s, and an ultrasonic time of 2 min, to obtain nano copper oxide solution 1. S3: 1.5 g of copper oxide nanowires (40 nm) was weighed and added to nano-copper oxide solution 1. Ultrasonic dispersion was then thoroughly carried out at an ultrasonic real-time temperature of 55°C, an ultrasonic pulse width of 0.1 s, and an ultrasonic time of 2 min to obtain nano-copper oxide solution 2. S4: 2.0 g of copper oxide nanowires (40 nm) was weighed and added to nano-copper oxide solution 2. Ultrasonic dispersion was thoroughly carried out at an ultrasonic real-time temperature of 55°C, an ultrasonic pulse width of 0.1 s, and an ultrasonic time of 3 min, to obtain nano-copper oxide ink. S5: The nano-copper oxide ink was mechanically shaken uniformly for 1 min and then left to stand for preparation for use. S6: A special engineering plastic substrate made of polyphenylene sulfide, 2 mm thick and 20 x 50 mm in size, was prepared and ultrasonically cleaned with isopropanol for 5 minutes to remove foreign matter from the surface, then dried and prepared for use. S7: A special engineering plastic substrate made of polyphenylene sulfide was subjected to oxygen plasma surface treatment for 120 seconds. S8: A polyphenylene sulfide special engineering plastic substrate was vacuum-adsorbed onto the spin coat chuck of a spin coater, and 1.5 mL of nano-copper oxide ink was dropped onto the center of the substrate. The substrate was then spin-coated at 1000 rpm for 20 s, and then at 500 rpm for 10 s. S9: A polyphenylene sulfide special engineering plastic substrate spin-coated with nano-copper oxide ink was placed in a constant temperature air drying oven or vacuum drying oven and dried by heating at 60°C for 2 hours to obtain a nano-copper oxide film. S10: A polyphenylene sulfide special engineering plastic substrate coated with nano-copper oxide film was placed on a processing platform using a 532 nm wavelength continuous green light laser, and the height of the processing platform was adjusted to focus the laser. S11: A serpentine electrode pattern with a size of 18.0 × 15.3 mm was drawn, and patterned direct writing (laser direct writing induced passivation / photothermal reduction sintering) was performed with a laser along the filling path of the snake-shaped electrode pattern at a power of 250 mW, a speed of 40 mm / s, and a line scanning period of 30 μm, converting the black nano-copper oxide along the scanning path into red nano-copper, and obtaining a high-temperature resistant nano-copper electrode. FIG. 1 is an optical photograph of the prepared precursor solution. Figure 2 shows an optical photograph of the prepared nano-copper oxide ink. Figure 3 shows an optical photograph of the fabricated high-temperature resistant nano-copper electrode with a meandering pattern.

[0035] Example 2: S1: 0.5 g of polyvinylpyrrolidone and 0.05 g, 0.10 g, 0.15 g, 0.20 g, and 0.25 g of sodium formate were weighed out sequentially and mixed with 3.0 mL of ethylene glycol and 1.0 mL of N,N-dimethylformamide solution. The mixture was heated uniformly at 60°C and 1200 rpm while stirring for 12 hours to obtain five precursor solutions with different concentrations of sodium formate. S2: 2.0 g of copper oxide nanowires (40 nm) were weighed and added to the five precursor solutions. The ultrasonic real-time temperature was 55°C, the ultrasonic pulse width was 0.1 s, and the ultrasonic time was 3 min. Then, the five nano copper oxide solutions 1 were obtained. S3: 2.0 g of copper oxide nanowires (40 nm) were weighed and added to five types of nano-copper oxide solutions 1. The ultrasonic real-time temperature was 55°C, the ultrasonic pulse width was 0.1 s, and the ultrasonic time was 3 min. Then, the five types of nano-copper oxide solutions 2 were obtained. S4: 1.0 g of copper oxide nanowires (40 nm) was weighed and added to five types of nano-copper oxide solution 2. The ultrasonic real-time temperature was 55°C, the ultrasonic pulse width was 0.1 s, and the ultrasonic time was 2 min. Then, ultrasonic dispersion was thoroughly carried out to obtain five types of nano-copper oxide inks. S5: The nano-copper oxide ink was mechanically shaken uniformly for 2 min and then left to stand for use. S6: Five polyphenylene sulfide special engineering plastic substrates, 2 mm thick and 20 x 50 mm in size, were prepared and ultrasonically cleaned for 5 minutes using isopropanol to remove foreign matter from the surface, then dried and prepared for use. S7: A special engineering plastic substrate made of polyphenylene sulfide was subjected to oxygen plasma surface treatment for 120 seconds. S8: Special engineering plastic substrates of polyphenylene sulfide were vacuum-adsorbed onto the spin coat chuck of a spin coater, and 1.5 mL of nano-copper oxide ink with different concentrations of sodium formate was dropped onto the center of the substrate. The substrate was then spin-coated at 1000 rpm for 20 s and then at 500 rpm for 10 s. S9: A polyphenylene sulfide special engineering plastic substrate spin-coated with nano-copper oxide ink was placed in a constant temperature air drying oven or vacuum drying oven and dried by heating at 60°C for 5 hours to obtain a nano-copper oxide film. S10: A polyphenylene sulfide special engineering plastic substrate coated with nano-copper oxide film was placed on a processing platform using a 532 nm wavelength continuous green light laser, and the height of the processing platform was adjusted to focus the laser. S11: A rectangular electrode pattern measuring 36 × 6 mm was drawn, and patterned direct writing (laser direct writing induced passivation / photothermal reduction sintering) was sequentially performed with a laser along the filling path of the rectangular electrode pattern at a power of 250 mW, a speed of 40 mm / s, and a line scanning period of 35 μm, converting the black nano-copper oxide along the scanning path into red nano-copper, resulting in a nano-copper electrode. S12: A thin layer of silver paste was manually applied to both ends of each nano-copper electrode, and the electrodes were pulled out and placed in a vacuum drying oven, where they were dried by heating at 60°C for 4 hours. S13: A voltage divider circuit board was designed according to the resistance value of the nano-copper electrodes, and each nano-copper electrode was connected in turn via alligator clip wires, and then connected to the data collection device via DuPont lines. S14: The nano-copper electrode was placed in a constant temperature air drying oven, and the temperature was set to 170°C. The change in partial pressure was recorded in real time through a data acquisition device. S15: The data results were converted into the relative resistance change of the nano-copper electrode by the partial pressure formula. Figure 4 shows the change in relative resistance over time at 170°C for nanocopper with different concentrations of sodium formate. As can be seen, when the sodium formate content was 0.15g, the high-temperature resistance after laser direct-write-induced passivation was the best. As the sodium formate content decreased, the complex formed by coordination with the nanocopper surface became insufficient to resist oxygen gas penetration, resulting in poor high-temperature oxidation resistance. As the sodium formate content increased, additional reactions occurred at the nanocopper interface, adversely affecting the passivation effect and surface properties, resulting in the nanocopper's long-term high-temperature oxidation resistance being lost.

[0036] Example 3: S1: 0.5 g of polyvinylpyrrolidone and 0.15 g of sodium formate were weighed and mixed with 3.0 mL of ethylene glycol and 3.0 mL of isopropanol, and the mixture was uniformly heated at 60°C and 1200 rpm and stirred for 6 hours to obtain a precursor solution. S2: 2.0g / 3.0g / 4.0g / 5.0g / 6.0g / 7.0g of copper oxide nanowires (40nm) were weighed out sequentially and added to the precursor solution in small amounts in multiple batches. Ultrasonic dispersion was then thoroughly carried out at an ultrasonic real-time temperature of 55°C, an ultrasonic pulse width of 0.1s, and a single ultrasonic time of 2min, to obtain nano-copper oxide inks with different concentrations of copper oxide nanowires. S3: The nano-copper oxide ink was mechanically shaken uniformly for 1–3 min and then left to stand for preparation for use. S4: Six polyphenylene sulfide special engineering plastic substrates, 2 mm thick and 20 × 50 mm in size, were prepared and ultrasonically cleaned with isopropanol for 5 minutes to remove foreign matter from the surface, then dried and prepared for use. S5: Same as S7 in Example 2. S6: Special polyphenylene sulfide engineering plastic substrates were vacuum-adsorbed onto the spin coat chuck of a spin coater, and 1.5 mL of nano-copper oxide ink with different concentrations of copper oxide nanowires was dropped onto the center of the substrate. The substrate was then spin-coated at 1000 rpm for 20 s and then at 500 rpm for 10 s. S7: A special engineering plastic made of polyphenylene sulfide spin-coated with nano-copper oxide ink was placed in a constant temperature air drying oven or vacuum drying oven and dried by heating at 60°C for 6 hours to obtain a nano-copper oxide film. S8 to S9: Similar to S10 to S11 in Example 2. S10: A thin layer of silver paste was manually applied to both ends of each nano-copper electrode, and the electrodes were pulled out and placed in a vacuum drying oven and dried at 60°C for 4.5 hours. S11: The resistance of laser surface-treated nanocopper with various concentrations of copper oxide nanowires was measured with a benchtop multimeter. Figure 5 shows the change in the resistance of nanocopper after laser surface treatment at various concentrations of copper oxide nanowires. As the content of copper oxide nanowires gradually increases, the content of nanocopper subjected to laser photothermal reduction sintering also increases, and the resistance value decreases, showing a tendency for the conductivity to saturate (minimum value is 0.66 Ω / sq).

[0037] Example 4: S1: 0.5 g of polyvinylpyrrolidone and 0.15 g of sodium formate were weighed and mixed with 3.0 mL of ethylene glycol and 1.0 mL of N,N-dimethylformamide solution. The mixture was heated uniformly at 60°C and 1200 rpm while stirring for 12 hours to obtain a precursor solution. S2 to S5: Same as in Example 2. S6: Seven polyphenylene sulfide special engineering plastic substrates, 2 mm thick and 20 × 50 mm in size, were prepared and ultrasonically cleaned with isopropanol for 5 minutes to remove foreign matter from the surface, then dried and prepared for use. S7 to S8: The same as in Example 1. S9: Same as S7 in Example 3. S10: Same as in Example 1. S11: A rectangular electrode pattern with a size of 36 × 6 mm was drawn, and patterned direct writing (laser direct writing induced passivation / photothermal reduction sintering) was performed by laser along the filling path of the rectangular electrode pattern at powers of 100 mW / 150 mW / 200 mW / 250 mW / 300 mW / 350 mW / 400 mW, maintaining a speed of 40 mm / s and a line scanning period of 35 μm. The black nano-copper oxide along the scanning path was converted into red nano-copper, and a nano-copper electrode was obtained. S12: A thin layer of silver paste was manually applied to both ends of each nano-copper electrode, and the electrodes were pulled out and placed in a vacuum drying oven and dried at 60°C for 6 hours. S13: The resistance of nano-copper surface treated with different laser powers was measured with a benchtop multimeter. S14: Same as S13 in Example 2. S15: The nano-copper electrode was placed in a constant temperature air drying oven, and the temperature was set to 80°C. The change in partial pressure was recorded in real time through a data acquisition device. S16: Same as S15 in Example 2. Figure 6 is an optical image of nano-copper at a laser power of 250mW. Figure 7 is an optical image of nano-copper at a laser power of 100mW. Figure 8 is an optical image of nano-copper at a laser power of 400mW. When the laser power is 250mW, the surface of the nano-copper obtained by reduction sintering is relatively dense, smooth, and bright in color. When the laser power is relatively low (100mW), the reduction threshold of nano-copper is not reached, and the surface of the nano-copper is dark red and contains some copper oxide. When the laser power is high (400mW), excessive energy injection causes stress concentration in the surface region of the nano-copper, resulting in cracks. Figure 9 shows the change in resistance of surface-treated nano-copper electrodes with various laser powers. As the laser power gradually increases, the energy per unit area of ​​the focused spot increases, the photothermal effect becomes more pronounced, and the reduction-sintering reaction becomes more complete. It was found that when the laser power is between 250 and 400 mW, the conductivity of the surface-treated nano-copper electrode tends to saturate (minimum value is 0.36 Ω / sq). Figure 10 shows the change in relative resistance over time at 80°C for nano-copper surface-treated with various laser powers. It was found that when the laser power was 250mW, the reaction temperature field and conditions were most reasonable for formate coordination passivation induced by laser direct writing. As the laser power increased or decreased, excessive sintering (reoxidation of nano-copper) and insufficient reduction sintering (the nano-copper surface contained relatively large amounts of copper oxide) reduced the high-temperature oxidation resistance of nano-copper, resulting in a larger change in relative resistance over the same period.

[0038] Example 5: S1 to S10: Same as in Example 4. S11: A rectangular electrode pattern with a size of 36 × 6 mm was drawn, and patterned direct writing (laser direct writing induced passivation / photothermal reduction sintering) was performed by laser along the filling path of the rectangular electrode pattern, following a line scanning period of 15 μm / 20 μm / 25 μm / 30 μm / 35 μm / 40 μm / 45 μm in order, maintaining a power of 250 mW and a speed of 40 mm / s. The black nano-copper oxide along the scanning path was converted into red nano-copper, and a nano-copper electrode was obtained. S12: Same as in Example 4. S13: The resistance of surface-treated nano-copper at different laser line scanning periods was measured with a benchtop multimeter. S14: Same as in Example 4. S15: The nano-copper electrode was placed in a constant temperature air drying oven, and the temperature was set to 170°C. The change in partial pressure was recorded in real time through a data acquisition device. S16: Same as in Example 4. Figure 16 shows an optical image of nanocopper with a laser line scanning period of 35 μm, Figure 11 shows an optical image of nanocopper with a laser line scanning period of 15 μm, and Figure 12 shows an optical image of nanocopper with a laser line scanning period of 45 μm. When the laser line scanning period is 35 μm, the period is close to the size of the laser spot, and the surface of the nanocopper obtained by reduction sintering is relatively dense and smooth. When the laser line scanning period is relatively short (15 μm), the overlapping area of ​​the scanning paths increases, resulting in increased heat accumulation and thermal stress in the repeated scanning area, causing cracks on the surface of the nanocopper. When the laser line scanning period is relatively long (45 μm), a thermal barrier is created between the scanning paths, which can lead to the formation of microcracks. Figure 13 shows the change in resistance of nano-copper surface-treated with various laser line scanning cycles. It was found that the resistance of nano-copper obtained by reduction sintering was lowest (0.36 Ω / sq) when the laser line scanning cycle was 35 μm. As the laser line scanning cycle gradually became shorter, excessive sintering caused by repeated heat accumulation reduced the conductivity of the nano-copper. As the laser line scanning cycle gradually became longer, surface defects caused by the energy difference between photothermal reduction sintering cycles also affected the conductivity of the nano-copper. Figure 14 shows the change in relative resistance over time at 170°C for nanocopper treated with various laser line scanning periods. It was found that when the laser line scanning period was 35 μm, the nanocopper subjected to laser direct writing-induced passivation exhibited good high-temperature thermal stability. When the laser line scanning period was shortened, cracks caused by thermal stress accelerated the penetration of oxygen gas at high temperatures, reducing the oxidation resistance of the nanocopper. When the laser line scanning period was lengthened, the barrier caused by the thermal difference led to surface defects in the nanocopper, which in turn led to poor high-temperature oxidation resistance and a large change in relative resistance over the same period.

[0039] Example 6: S1 to S5: Same as in Example 4. S6 to S10: Same as in Example 1. S11: A rectangular electrode pattern measuring 36 × 6 mm was drawn, and patterned direct writing (laser direct writing induced passivation / photothermal reduction sintering) was performed with a laser along the filling path of the rectangular electrode pattern at a power of 250 mW, a speed of 40 mm / s, and a line scanning period of 35 μm, converting the black nano-copper oxide along the scanning path into red nano-copper, resulting in a nano-copper electrode. S12: A thin layer of silver paste was manually applied to both ends of the nano-copper electrode, and the electrode was pulled out and placed in a vacuum drying oven, where it was heated at 60°C for 2 hours to dry. S13: A voltage divider circuit board was designed according to the resistance value of the nano-copper electrode, and connected to the nano-copper electrode through alligator clip lead wires, and then connected to the data collection device via DuPont lines. S14: 0.5 g of polyvinylpyrrolidone was weighed and mixed with 3.0 mL of ethylene glycol and 1.0 mL of N,N-dimethylformamide solution. The mixture was stirred for 12 hours while uniformly heating at 60°C and 1200 rpm to obtain a sodium formate-free precursor solution. S15: 2.0 g of copper oxide nanowires (40 nm) was weighed and added to the sodium formate-free precursor solution. Ultrasonic dispersion was thoroughly carried out at an ultrasonic real-time temperature of 55°C, an ultrasonic pulse width of 0.1 s, and an ultrasonic time of 3 min, to obtain sodium formate-free nanocopper oxide solution 1. S16: 2.0 g of copper oxide nanowires (40 nm) was weighed and added to sodium formate-free nano-copper oxide solution 1. Ultrasonic dispersion was thoroughly carried out at an ultrasonic real-time temperature of 55°C, an ultrasonic pulse width of 0.1 s, and an ultrasonic time of 3 min, to obtain sodium formate-free nano-copper oxide solution 2. S17: 1.0 g of copper oxide nanowires (40 nm) was weighed and added to the sodium formate-free nano-copper oxide solution 2. Ultrasonic dispersion was thoroughly carried out at an ultrasonic real-time temperature of 55°C, an ultrasonic pulse width of 0.1 s, and an ultrasonic time of 2 min, to obtain a sodium formate-free nano-copper oxide ink. S18: The sodium formate-free nano-copper oxide ink was mechanically shaken uniformly for 2 min and then left to stand for use. S19 to S20: Similar to S6 to S7 in Example 1. S21: A polyphenylene sulfide special engineering plastic substrate was vacuum-adsorbed onto the spin coat chuck of a spin coater, and 1.5 mL of sodium formate-free nano-copper oxide ink was dropped onto the center of the substrate. The substrate was then spin-coated at 1000 rpm for 20 s and then at 500 rpm for 10 s. S22: A special engineering plastic made of polyphenylene sulfide spin-coated with sodium formate-free nano-copper oxide ink was placed in a constant temperature air drying oven or vacuum drying oven and dried by heating at 60°C for 2 hours to obtain a sodium formate-free nano-copper oxide film. S23: A special engineering plastic, polyphenylene sulfide, coated with a sodium formate-free nano-copper oxide film was placed on a processing platform with a 532 nm wavelength continuous green light laser, and the height of the processing platform was adjusted to focus the laser. S24: A rectangular electrode pattern with a size of 36 × 6 mm was drawn, and patterned direct writing (laser direct writing induced passivation / photothermal reduction sintering) was performed with a laser along the filling path of the rectangular electrode pattern at a power of 250 mW, a speed of 40 mm / s, and a line scanning period of 35 μm. The black nano-copper oxide along the scanning path was converted to red nano-copper, and a sodium formate-free nano-copper electrode was obtained. S25: A thin layer of silver paste was manually applied to both ends of the sodium formate-free nano-copper electrode, and the electrode was pulled out and placed in a vacuum drying oven and dried at 60°C for 2 hours. S26: A voltage divider circuit board was designed according to the resistance value of the sodium formate-free nanocopper electrode, and connected to the sodium formate-free nanocopper electrode through an alligator clip lead wire, and then connected to the data acquisition device via a DuPont line. S27: The nano-copper electrode and the sodium formate-free nano-copper electrode were placed in a constant temperature air-blowing drying oven, the temperature was set to 170°C, and the change in partial pressure was recorded in real time through a data acquisition device. S28: The data results were converted into the relative resistance changes of the nano-copper electrode and the sodium formate-free nano-copper electrode by the partial pressure equation. Figure 15 shows the change in relative resistance with time of nanocopper (LIP-Cu) and sodium formate-free nanocopper (Cu) at 170°C. The high-temperature oxidation resistance of sodium formate-free nanocopper was found to be much inferior to that of nanocopper. Nanocopper has better thermal stability even at a high temperature of 170°C due to the formate coordination passivation protection induced by laser heat.

[0040] Example 7: S1 to S26: Same as in Example 6. S27: The nano-copper electrode and the sodium formate-free nano-copper electrode were placed in a constant temperature air-blowing drying oven, the temperature was set to 120°C, and the change in partial pressure was recorded in real time through a data acquisition device. S28: Same as in Example 6. Figure 16 shows the change in relative resistance of nanocopper (LIP-Cu) and sodium formate-free nanocopper (Cu) with time at 120°C. It was found that the conductivity of sodium formate-free nanocopper continued to decrease at 120°C, but the conductivity of nanocopper remained stable within 105 h with no obvious decrease.

[0041] Example 8: S1 to S26: Same as in Example 6. S27: The nano-copper electrode and the sodium formate-free nano-copper electrode were placed in a constant temperature air drying oven and gradually heated from 30°C to 190°C, with temperature intervals of 20°C, and each temperature was maintained for 10 min. The changes in partial pressure were recorded in real time through a data collection device. S28: Same as in Example 6. Figure 17 shows the change in relative resistance of nanocopper (LIP-Cu) and sodium formate-free nanocopper (Cu) as the temperature is gradually increased from 30°C to 170°C. It was found that the electrical properties of sodium formate-free nanocopper decreased at a gradually faster rate during the stepwise increase process, but the electrical properties of nanocopper were stable by the time the temperature increased to 150°C, and only slightly decreased when the temperature increased to 170°C. The second aspect of the present invention proposes a complete laser in-situ direct-write integrated sensor system, including a specialized engineering plastic rigid substrate, a high-temperature resistant nano-copper interconnect circuit, a laser-induced graphene temperature sensor, a voltage divider, an analog-to-digital converter (ADC), a microcontroller (MCU), and a low-dropout linear regulator (LDO).

[0042] Example 9: S1: A 50mm wide PI tape was attached to the surface of a special engineering plastic substrate made of polyphenylene sulfide, 60mm long, 60mm wide, and 4mm thick. S2: A circuit with an outer outline of 45 x 27 mm was drawn and cut along the outline using an ultraviolet nanosecond pulse laser with a wavelength of 355 nm. S3: The PI tape within the cutting outline was peeled off from the polyphenylene sulfide special engineering plastic substrate. S4: An appropriate amount of the nano-copper oxide ink prepared in Example 1 was applied onto a special engineering plastic substrate made of polyphenylene sulfide, and then heated and dried. S5: The remaining PI tape was peeled off from the polyphenylene sulfide special engineering plastic substrate, revealing a nano-copper oxide film with circuit outlines. S6: A 532 nm continuous wavelength laser was used to perform laser direct writing induced passivation / photothermal reduction sintering along the filling path of the circuit pattern, resulting in high temperature resistant nano-copper interconnect circuits. S7: A temperature sensor with an appropriate size and shape was designed, and in situ induced carbonization was performed at the corresponding location on the surface of a special engineering plastic substrate of polyphenylene sulfide using a CO2 laser with a wavelength of 10.6 μm to form a laser-induced graphene temperature sensor. S8: According to the circuit design, each element was connected to a high-temperature resistant nano-copper interconnect circuit with copper paste, and the copper paste was heated to harden. S9: The visual serial port was connected through an external DuPont line, and this integrated temperature sensor system was placed within the upper and lower temperature limits of the chip's tolerance range to detect and measure the temperature. Figure 18 shows an optical photograph of the integrated sensor system using a complete laser in-situ direct writing technique.

Claims

1. A method for producing high temperature resistant nano copper by laser direct writing, Step (1) of uniformly heating and stirring an alcohol-based solvent, an organic dispersant, an organic auxiliary, and an appropriate amount of formate to obtain a precursor solution; Step (2) adding an appropriate amount of nano-copper oxide to the precursor solution and dispersing it sufficiently by ultrasonic waves to obtain a nano-copper oxide ink containing 43.0-50.4 wt% nano-copper oxide, 37.1-50.4 wt% alcohol-based solvent, 3.4-5.3 wt% organic dispersant, 0.0-9.5 wt% organic auxiliary, and 1.3-2.0 wt% formate, wherein the nano-copper oxide is copper oxide nanowires; Step (3) of applying the nano copper oxide ink onto the pretreated substrate, heating and drying it to obtain a nano copper oxide film; and step (4) of subjecting the nano-copper oxide film to laser one-step direct-writing induced passivation / photothermal reduction sintering to obtain high-temperature resistant nano-copper, wherein the laser is a continuous green light with a wavelength of 532 nm, a power of 100-400 mW, a speed of 20-200 mm / s, and a scanning period of 20-40 μm, and the induction of passivation is by inducing a passivation reaction of formate on the surface of the nano-copper, whereby copper ions on the surface of the nano-copper and formate form a copper formate dimer complex, thereby forming an antioxidant coordination passivation layer.

2. 2. The method for producing high-temperature resistant nanocopper by laser direct writing according to claim 1, wherein the alcohol-based solvent in step (1) is at least one selected from the group consisting of monohydric alcohols and polyhydric alcohols.

3. 2. The method for producing high-temperature resistant nanocopper by laser direct writing according to claim 1, wherein the organic dispersant in step (1) is at least one selected from the group consisting of polyacrylamide-based organic high polymers, polyethylene oxide-based organic high polymers, tannin, and lignin.

4. The organic co-agent of step (1) has the chemical formula C ｎ H ２ｎ＋１ 2. The method for producing high temperature resistant nano copper by direct laser writing according to claim 1, wherein the organic amide is at least one selected from alkyl amides satisfying NO (1≦n≦5).

5. 2. The method for producing high-temperature resistant nanocopper by laser direct writing according to claim 1, wherein the formate in step (1) is at least one selected from the group consisting of lithium formate, beryllium formate, sodium formate, magnesium formate, potassium formate, calcium formate, iron formate, manganese formate, cobalt formate, nickel formate, copper formate, zinc formate, barium formate, and ammonium formate.

6. 2. The method for manufacturing high temperature resistant nano copper by laser direct writing according to claim 1, wherein the pretreatment in step (3) is oxygen plasma surface treatment, and the treatment time is 60s to 150s.

7. The method for producing high-temperature resistant nanocopper by laser direct writing according to claim 1, characterized in that the heating and stirring in step (1) is performed at a temperature of 50 to 70°C, at a rotation speed of 600 to 1500 rpm, and for 2 to 20 hours; the ultrasonic dispersion in step (2) is performed at a real-time temperature of 50 to 60°C, with an ultrasonic pulse width of 0.1 s and for 0.1 to 2 hours; and the heating and drying in step (3) is performed at a temperature of 50 to 80°C and for 2 to 12 hours.

8. 1. A fully laser in situ direct writing integrated sensor system, comprising:

10. An integrated sensor system by full laser in-situ direct writing, comprising: a special engineering plastic substrate, a high-temperature-resistant nano-copper interconnect circuit, a laser-induced graphene temperature sensor, a voltage divider, an analog-to-digital converter (ADC), a microcontroller (MCU), and a low-dropout linear regulator (LDO), wherein the remaining components are connected via the high-temperature-resistant nano-copper interconnect circuit to realize an integrated sensor function, wherein the high-temperature-resistant nano-copper interconnect circuit and the laser-induced graphene temperature sensor are both formed in-situ on the special engineering plastic substrate by full laser direct writing technology, and the high-temperature-resistant nano-copper is manufactured by the method according to any one of claims 1 to 7.

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