Antioxidant copper fiber-copper powder composite conductive paste and preparation method and application thereof

Abstract

The invention discloses an antioxidant copper fiber-copper powder composite conductive paste and a preparation method and application thereof, and belongs to the technical field of conductive pastes.The composite conductive paste comprises a composite conductive phase, thermosetting resin and an organic carrier; the composite conductive phase is composed of paraffin-coated copper powder, modified copper fibers and a biological reducing agent; the preparation method of the paraffin-coated copper powder comprises the steps that nano-copper powder with the particle size ranging from 30 nm to 200 nm is cleaned and then heated and reduced in the hydrogen atmosphere, the nano-copper powder is placed in liquid paraffin after being cooled, and the paraffin-coated copper powder is obtained after the nano-copper powder is taken out and dried; a preparation method of the modified copper fibers comprises the steps that copper fibers with the diameter ranging from 10 nm to 300 nm and the length ranging from 5 microns to 200 microns are placed in a coupling agent solution, and the copper fibers are taken out and dried to obtain the modified copper fibers; the biological reducing agent comprises capsaicin. The composite conductive paste is good in conductivity and excellent in oxidation resistance, can be sintered and cured at a low temperature, and has a good application prospect in the field of flexible electronic devices.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive pastes, and particularly relates to an antioxidant copper fiber - copper powder composite conductive paste, a preparation method thereof, and an application thereof. Background Art

[0002] In the current rapidly developing field of the electronics industry, conductive pastes, as the core materials for electronic component packaging, electrode manufacturing, etc., are of great importance. With the continuous advancement of electronic products towards lightweight, miniaturization, multi-functionality, and high performance, the market's performance requirements for conductive pastes are becoming increasingly stringent.

[0003] Metallic copper, due to its rich reserves, relatively low cost, and electrical conductivity second only to precious metal silver, has become one of the ideal choices for preparing conductive pastes. However, copper has active chemical properties and is extremely prone to oxidation reactions in the air, and an oxide film layer is rapidly formed on its surface. This oxide film not only significantly increases the resistivity, seriously reducing the electrical conductivity of copper, but also significantly increases the heat treatment temperature of the conductive paste, greatly increasing the processing difficulty and restricting its wide application in the electronic field.

[0004] To overcome the problem of copper oxidation, the existing technology has conducted in - depth exploration from multiple dimensions. Coating the surface of copper powder with metals such as silver or nickel is one of the common methods (such as the Chinese patent document with publication number CN104801709A, etc.), but the uniformity and integrity of the coating are difficult to precisely control, resulting in unstable antioxidant effects. Preparing copper powder using copper salt solutions and antioxidants or deoxidizers, etc., can improve antioxidant properties (such as the Chinese patent document with publication number CN111957986A, etc.), but there are problems such as environmental pollution and biosafety, and it may also affect the electrical conductivity of copper. Coating copper powder with organic polymer polymers (such as the Chinese patent document with publication number CN104629090A, etc.) can isolate oxygen to a certain extent, but the coating layer is prone to cracking during the processing, and the amount of coating agent used is large, which will cause volume shrinkage during sintering, affecting the denseness of the sintered body and thus reducing the electrical conductivity. Using a reducing sintering atmosphere, such as hydrogen, can inhibit oxidation, but hydrogen is flammable and explosive, with a high risk of gas leakage and great safety hazards. Adding organic corrosion inhibitors, such as imidazole compounds, can form a protective layer on the surface of copper powder to prevent oxidation, but its heat resistance is poor, and it will promote the formation of an oxide film on the surface of copper powder during high - temperature heat treatment, causing a sharp drop in conductivity. Although the oxidation of copper powder can be inhibited to a certain extent through low - temperature sintering processes, some low - temperature sintered copper pastes still have environmental protection or cost problems and are difficult to promote and apply.

[0005] At the same time, with the rise of flexible electronic technology, flexible circuits have put forward higher requirements on the flexibility, processability and environmental protection of conductive pastes. Therefore, developing a copper-based conductive paste that has excellent antioxidant properties and conductivity, can be sintered and cured at low temperatures, and is suitable for flexible devices has become a key issue that needs to be solved in the current electronic materials field. Summary of the invention

[0006] The present invention provides an anti-oxidation copper fiber-copper powder composite conductive paste, which can effectively overcome the many defects of existing copper pastes, such as insufficient oxidation resistance, excessively high sintering temperature, poor environmental protection, and limited application on flexible substrates. The anti-oxidation copper fiber-copper powder composite conductive paste has good conductivity, excellent antioxidant performance, low-temperature sintering and curing characteristics, and is highly suitable for flexible devices.

[0007] The specific technical solutions adopted are as follows:

[0008] An anti-oxidation copper fiber-copper powder composite conductive paste, comprising a composite conductive phase, a thermosetting resin and an organic carrier; the mass ratio of the composite conductive phase, the thermosetting resin and the organic carrier is 6-10:1-3:1;

[0009] The composite conductive phase is composed of paraffin-coated copper powder, modified copper fiber and bioreductant, and the mass ratio of the paraffin-coated copper powder, modified copper fiber and bioreductant is 5-10:5-10:1;

[0010] The preparation method of paraffin-coated copper powder is as follows: after washing nano copper powder with a particle size of 30nm-200nm, heating and reducing it in a hydrogen atmosphere, further cooling it and placing it in liquid paraffin, taking it out and drying it to obtain paraffin-coated copper powder;

[0011] The preparation method of the modified copper fiber is as follows: after cleaning the copper fiber with a diameter of 10nm-300nm and a length of 5μm-200μm, the copper fiber is placed in a coupling agent solution, taken out and dried to obtain the modified copper fiber;

[0012] Bioreducing agents include capsaicin.

[0013] The present invention prepares a composite conductive slurry whose components include a composite conductive phase, a thermosetting resin and an organic carrier, wherein the composite conductive phase is composed of paraffin-coated copper powder, modified copper fibers and a bioreductant, and the bioreductant undergoes photothermal decomposition during the slurry curing stage to generate reducing groups, so that copper salts, copper oxides and the like in the copper slurry are self-reduced into pure copper particles, and the organic components form a dense protective film on the surface of the newly generated copper particles to protect the pure copper from oxidation; the paraffin-coated copper powder and the modified copper fibers can provide more contact points after being composited, forming an effective conductive network, thereby improving the overall conductive performance of the slurry and contributing to the low-temperature curing performance.

[0014] Preferably, the viscosity of the antioxidant copper fiber - copper powder composite conductive paste is 70 - 130 Pa·s.

[0015] Preferably, the organic carrier is composed of the following components by weight percentage:

[0016] Terpineol 70 - 90%;

[0017] Ethyl acetate 5 - 15%;

[0018] Ethyl cellulose 2 - 6%;

[0019] Defoamer 1 - 4%;

[0020] Coupling agent 1 - 5%.

[0021] Preferably, the thermosetting resin is selected from at least one of polyester resin, polyurethane resin or polymethyl methacrylate resin. The addition of the thermosetting resin plays roles such as bonding and imparting mechanical properties 、 and enhancing antioxidant properties, etc.

[0022] Preferably, when preparing the paraffin - coated copper powder, in the cleaning process, the nano - copper powder is first ultrasonically oscillated and cleaned with a dilute sulfuric acid solution (volume fraction of 6% - 8%), then rinsed with deionized water until the pH value is 6 - 7, and dried in vacuum.

[0023] Preferably, the conditions for hydrogen - atmosphere heating reduction are: reduction temperature 250 - 280 °C, hydrogen flow rate 50 - 70 mL / min, and reduction time 1 - 2 h.

[0024] Optionally, the mass ratio of the copper powder after hydrogen reduction to liquid paraffin is 10 - 50:1, and the paraffin - coated copper powder is obtained by evaporation and drying under a nitrogen atmosphere.

[0025] Preferably, when preparing the modified copper fiber, the coupling agent includes silane coupling agent, titanate coupling agent, aluminate coupling agent or zirconate coupling agent, the concentration of the coupling agent solution is 1 - 5 wt%, and the copper fiber is taken out and dried after being placed in the coupling agent solution for 10 - 30 min.

[0026] Preferably, the biological reducing agent is capsaicin, or a combination of at least one of chitin, resveratrol, tannic acid, chlorogenic acid, caffeic acid, piperine and capsaicin. The biological reducing agent is safer and more environmentally friendly, and can prevent copper oxidation and play a protective role.

[0027] The present invention also provides a preparation method of the antioxidant copper fiber - copper powder composite conductive paste, including the following steps:

[0028] (1) Weigh the formula amounts of terpineol, ethyl acetate, ethyl cellulose, defoamer and coupling agent, mix and dissolve them fully to obtain an organic carrier;

[0029] (2) Weigh the paraffin-coated copper powder, modified copper fiber, and biological reducing agent in the formula amount, grind and mix them evenly to obtain a composite conductive phase;

[0030] (3) Weigh the composite conductive phase, thermosetting resin, and organic carrier in the formula amount, transfer them to a three-roll mill after sufficient mixing, grind and refine them, then perform ultrasonic treatment, and adjust the viscosity after vacuum degassing to obtain the antioxidant copper fiber-copper powder composite conductive paste.

[0031] Preferably, the composite conductive phase and the thermosetting resin are first put into a planetary mixer for low-speed premixing, and then the organic carrier is slowly added and the speed is increased for stirring to make them mix sufficiently.

[0032] Preferably, after the sufficiently mixed material is transferred to a three-roll mill, it is ground and refined through three rounds with different roll spacings. The roll spacing in the first round is 110 - 130 μm, the roll spacing in the second round is 70 - 90 μm, and the roll spacing in the third round is 30 - 40 μm.

[0033] Specifically, after vacuum degassing, the viscosity of the paste is adjusted to 70 - 130 Pa·s with a diluent or thickener according to requirements.

[0034] The present invention also provides the application of the antioxidant copper fiber-copper powder composite conductive paste in the field of flexible electronic devices.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] (1) The components of the composite conductive paste in the present invention include a composite conductive phase, a thermosetting resin, and an organic carrier. The composite conductive phase is composed of paraffin-coated copper powder, modified copper fiber, and a biological reducing agent. During the curing stage of the composite conductive paste, the biological reducing agent can undergo photothermal decomposition to generate reducing groups, enabling the copper salt or copper oxide in the paste to be self-reduced into pure copper particles. The organic component forms a dense protective film on the surface of the newly formed copper particles to protect the pure copper from oxidation, overcoming the problems of multiple steps and low efficiency, and easy oxidation in the traditional method. Moreover, after the paraffin-coated copper powder and the modified copper fiber are combined, more contact points can be provided. The addition of the modified copper fiber increases the conductive path and forms an effective conductive network, improving the overall conductive performance of the paste.

[0037] (2) The antioxidant copper fiber-copper powder composite conductive paste in the present invention can be cured at a low temperature below 200 °C, the curing time is 1 - 2 h, and the resistivity is low, meeting the market requirements.

[0038] (3) The antioxidant copper fiber-copper powder composite conductive paste in the present invention has excellent antioxidant performance and low-temperature sintering and curing characteristics, is green and environmentally friendly, and is highly suitable for flexible devices. Description of the Drawings

[0039] Figure 1 are scanning electron microscope images of the nano copper powder used in the examples and comparative examples;

[0040] Figure 2 is the scanning electron microscope image of the composite conductive phase prepared in Example 1;

[0041] Figure 3 is the scanning electron microscope image after printing the antioxidant copper fiber - copper powder composite conductive paste prepared in Example 2. Detailed implementation manners

[0042] To make the objectives, features, and advantages of the present invention more apparent and understandable, the following provides a detailed description through specific implementation manners. Many specific details are set forth in the following description to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined correspondingly without conflict.

[0043] For the operation methods without specific conditions noted in the following examples, they are generally in accordance with conventional conditions or the conditions recommended by the manufacturer. The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art. The experimental materials used in the following examples, unless otherwise specified, can be obtained from conventional biochemical reagent companies.

[0044] Example 1

[0045] Preparation of the organic carrier: Accurately weigh 75 g of terpineol, 10 g of ethyl acetate, 4 g of ethyl cellulose, 2 g of an antifoaming agent (polyether antifoaming agent GP - 330), and 1 g of a coupling agent (silane coupling agent KH550). Mix terpineol and ethyl acetate and stir for 5 minutes (200 revolutions per minute) to obtain a mixed solution A. Then, successively add ethyl cellulose, the antifoaming agent, and the coupling agent and stir for 5 minutes. After that, stir in a 70°C constant temperature water bath for 30 minutes until the ethyl cellulose dissolves to obtain a mixed material B, and cool it naturally to obtain the organic carrier.

[0046] Pretreatment of copper powder and preparation of the composite conductive phase: Take spherical copper powder with a particle size of 30 nm - 200 nm (SEM images are as Figure 1100 g as shown in the figure is ultrasonically cleaned (30 KHz) with 8% dilute sulfuric acid solution for 15 minutes, rinsed with deionized water until the pH value is 6 - 7, and then vacuum dried (50 °C, -0.08 MPa) for 1.5 hours. After that, it is reduced in a hydrogen atmosphere tube furnace (250 °C, hydrogen flow rate 50 mL / min) for 2 hours and cooled. Subsequently, it is dispersed in liquid paraffin (the mass ratio of copper powder after hydrogen reduction to liquid paraffin is 95:5) at an ultrasonic oscillation frequency of 35 KHz, and the excess paraffin is removed in a nitrogen atmosphere rotary evaporator (70 °C) to obtain paraffin-coated copper powder.

[0047] Weigh paraffin-coated copper powder, copper fibers modified with titanate coupling agent (copper fibers with a diameter of 10 nm - 300 nm and a length of 5 μm - 200 μm are cleaned and dried, then soaked and ultrasonically treated in a 2.5% mass fraction titanate coupling agent KR-38S solution for 18 minutes and dried at 95 °C for 1.2 hours), and a biological reducing agent (capsaicin: resveratrol = 1:1) according to the mass ratio of 5:5:1. Grind them in an agate mortar for 20 minutes (600 revolutions per minute) to obtain a composite conductive phase (the SEM image is as shown in Figure 2 the figure).

[0048] Preparation of the composite conductive paste: Weigh the composite conductive phase, polyurethane resin, and organic carrier (maintained at 45 °C in a water bath for 12 minutes and stirred) according to the mass ratio of 7:1:1. First, stir the composite conductive phase and the resin at a low speed (80 revolutions per minute) for 8 minutes, then add the organic carrier and increase the rotation speed to 250 revolutions per minute and stir for 18 minutes and evacuate (-0.06 MPa) for mixing. The material is processed by a three-roll mill (the roll spacing is 120 μm, 80 μm, and 30 μm in sequence, and ground three times) and ultrasonic treatment (25 kHz, 12 minutes), and then vacuum degassed (-0.08 MPa, 8 minutes). After adjusting the viscosity (80 Pa·s - 120 Pa·s), the antioxidant copper fiber - copper powder composite conductive paste is obtained.

[0049] Example 2

[0050] Preparation of the organic carrier: Accurately weigh 80 g of terpineol, 8 g of ethyl acetate, 5 g of ethyl cellulose, 3 g of defoaming agent (organosilicon defoaming agent BYK-066N), and 1 g of coupling agent (titanate coupling agent NDZ-201). Mix terpineol and ethyl acetate and stir for 5 minutes (250 revolutions per minute) to obtain a mixed solution A. Then, add ethyl cellulose, defoaming agent, and coupling agent in sequence and stir for 8 minutes. Then, stir in a 75 °C constant temperature water bath for 35 minutes until ethyl cellulose dissolves to obtain a mixed material B, and cool naturally to obtain the organic carrier.

[0051] Pretreatment of Copper Powder and Preparation of Composite Conductive Phase: Take 120 g of spherical copper powder with a particle size of 30 nm - 200 nm, ultrasonically clean it (35 KHz) with 6% dilute sulfuric acid solution for 12 minutes, rinse it with deionized water until the pH value is 6 - 7, then vacuum dry it (55 °C, -0.07 MPa) for 1.2 hours. After that, reduce it in a hydrogen atmosphere tube furnace (280 °C, hydrogen flow rate 60 mL / min) for 1.5 hours and then cool it. Subsequently, disperse it in liquid paraffin (mass ratio 94:6) with an ultrasonic oscillation frequency of 38 KHz, and remove the excess paraffin in a nitrogen atmosphere rotary evaporator (72 °C) to obtain paraffin-coated copper powder.

[0052] Weigh paraffin-coated copper powder, copper fibers modified with silane coupling agent (copper fibers with a diameter of 10 nm - 300 nm and a length of 5 μm - 200 μm are cleaned and dried, then soaked and ultrasonically treated in a 2.5% mass fraction silane coupling agent KH550 solution for 18 minutes and dried at 95 °C for 1.2 hours), and a biological reducing agent (capsaicin: resveratrol = 1:1) according to the mass ratio of 7:5:1. Grind them in an agate mortar for 25 minutes (700 revolutions per minute) to obtain a composite conductive phase.

[0053] Preparation of Composite Conductive Paste: Weigh the composite conductive phase, polyurethane resin, and organic carrier (keep it in a 48 °C water bath for 10 minutes and stir) according to the mass ratio of 68:11:11. First, stir the composite conductive phase and the resin at a low speed (90 revolutions per minute) for 6 minutes, then add the organic carrier and increase the rotation speed to 280 revolutions per minute and stir for 16 minutes and vacuumize (-0.055 MPa) for mixing. The material is processed by a three-roll mill (the roll spacings are 130 μm, 90 μm, and 40 μm in sequence, ground three times) and ultrasound (28 kHz, 10 minutes), and then vacuum degassed (-0.075 MPa, 6 minutes). After adjusting the viscosity (90 Pa·s - 130 Pa·s), the antioxidant copper fiber - copper powder composite conductive paste is obtained.

[0054] Example 3

[0055] Preparation of Organic Carrier: Accurately weigh 85 g of terpineol, 6 g of ethyl acetate, 6 g of ethyl cellulose, 2 g of defoaming agent (polyether defoaming agent GPE - 3000), and 1 g of coupling agent (aluminate coupling agent DL - 411). Mix terpineol and ethyl acetate and stir for 5 minutes (300 revolutions per minute) to obtain mixture A. Then, add ethyl cellulose, defoaming agent, and coupling agent in sequence and continue stirring. Keep stirring in an 80 °C constant temperature water bath for 40 minutes until ethyl cellulose dissolves to obtain mixture B, and then cool it naturally to obtain the organic carrier.

[0056] Pretreatment of copper powder and preparation of composite conductive phase: Take 150 g of spherical copper powder with a particle size of 30 nm - 200 nm, ultrasonically (40 KHz) oscillate and clean it with 7% dilute sulfuric acid solution for 10 minutes. After rinsing with deionized water until the pH value is 6 - 7, vacuum dry it (60 °C, -0.065 MPa) for 1 hour, then reduce it in a hydrogen atmosphere tubular furnace (260 °C, hydrogen flow rate 70 mL / min) for 1.2 hours and cool it. Subsequently, disperse it in liquid paraffin (mass ratio 93:7) at an ultrasonic oscillation frequency of 40 KHz, and remove the excess paraffin in a nitrogen atmosphere rotary evaporator (75 °C) to obtain paraffin-coated copper powder.

[0057] Weigh paraffin-coated copper powder, copper fibers modified by zirconate coupling agent (copper fibers with a diameter of 10 nm - 300 nm and a length of 5 μm - 200 μm are cleaned and dried, then soaked and ultrasonically treated in a 1.5% zirconate coupling agent solution for 20 minutes and dried at 100 °C for 1 hour), and biological reducing agent (capsaicin: resveratrol = 1:1) according to the mass ratio of 7:6:1, and grind them in an agate mortar for 30 minutes (800 revolutions per minute) to obtain the composite conductive phase.

[0058] Preparation of composite conductive paste: Weigh the composite conductive phase, polyurethane resin and organic carrier (keep warm in a 50 °C water bath for 8 minutes and stir) according to the mass ratio of 82:9:9. First, stir the composite conductive phase and resin at 100 revolutions per minute for 5 minutes, then add the organic carrier and increase the rotation speed to 300 revolutions per minute and stir for 15 minutes and vacuumize (-0.05 MPa) for mixing. The material is treated by a three-roll mill (roll spacings are 110 μm, 70 μm, 35 μm in sequence, and ground three times) and ultrasound (30 kHz, 8 minutes), and then vacuum degassed (-0.07 MPa, 5 minutes). After adjusting the viscosity (70 Pa·s - 110 Pa·s), the antioxidant copper fiber - copper powder composite conductive paste is obtained.

[0059] Comparative Example 1

[0060] In this comparative example, the organic carrier prepared by the method of Example 1 is used.

[0061] Pretreatment of copper powder and preparation of composite conductive phase: Take 100 g of spherical copper powder with a particle size of 30 nm - 200 nm, ultrasonically (30 KHz) oscillate and clean it with 8% dilute sulfuric acid solution for 15 minutes. After rinsing with deionized water until the pH value is 6 - 7, vacuum dry it (50 °C, -0.08 MPa) for 1.5 hours to obtain the pretreated copper powder; Weigh the pretreated copper powder, copper fibers (with a diameter of 10 nm - 300 nm and a length of 5 μm - 200 μm), and biological reducing agent (capsaicin: resveratrol = 1:1) according to the mass ratio of 5:5:1, and grind them in an agate mortar for 20 minutes (600 revolutions per minute) to obtain the composite conductive phase.

[0062] Preparation of the composite conductive paste: Weigh the composite conductive phase, polyurethane resin, and organic carrier according to the mass ratio of 7:1:1 (keep them in a water bath at 45°C for 12 minutes with stirring). First, stir the composite conductive phase and the resin at a low speed (80 revolutions per minute) for 8 minutes, then add the organic carrier and increase the rotation speed to 250 revolutions per minute, stir for 18 minutes, and mix under vacuum (-0.06 MPa). The material is processed by a three-roll mill (the roll spacings are 120 μm, 80 μm, and 30 μm in sequence, with three grindings) and ultrasound (25 kHz, 12 minutes), and then vacuum degassed (-0.08 MPa, 8 minutes). After adjusting the viscosity (80 Pa·s - 120 Pa·s), the conductive paste is obtained.

[0063] Comparative Example 2

[0064] Preparation of the organic carrier: Accurately weigh 70 g of terpineol, 15 g of ethyl acetate, 3 g of ethyl cellulose, 1 g of defoamer (organosilicon defoamer BYK-065), and 1 g of coupling agent (titanate coupling agent NDZ-101). Mix terpineol and ethyl acetate and stir for 3 minutes (220 revolutions per minute) to obtain a mixed solution A. Add ethyl cellulose and stir for 5 minutes (250 revolutions per minute), then add the defoamer and coupling agent in sequence and stir for 8 minutes. Stir in a constant temperature water bath at 65°C for 25 minutes until the ethyl cellulose dissolves to obtain a mixed material B, and naturally cool to obtain the organic carrier.

[0065] Pretreatment of copper powder and preparation of the composite conductive phase: Take 80 g of spherical copper powder with a particle size of 30 nm - 200 nm, wash it by ultrasonic oscillation (28 kHz) for 10 minutes, rinse it with deionized water until the pH value is 6 - 7, and then dry it in an oven at 45°C for 1 hour to obtain the pretreated copper powder; Weigh the pretreated copper powder, copper fiber (diameter 10 nm - 300 nm, length 5 μm - 200 μm), and biological reducing agent (capsaicin:caffeic acid = 1:1) according to the mass ratio of 7:5:1, and grind them in a ceramic mortar for 18 minutes (550 revolutions per minute) to obtain the composite conductive phase.

[0066] Preparation of the composite conductive paste: Weigh the composite conductive phase, polyurethane resin, and organic carrier according to the mass ratio of 78:11:11 (keep them in a water bath at 42°C for 10 minutes with stirring). First, stir the composite conductive phase and the resin at a low speed (70 revolutions per minute) for 7 minutes, then add the organic carrier and increase the rotation speed to 220 revolutions per minute, stir for 16 minutes, and mix under vacuum (-0.055 MPa). The material is processed by a three-roll mill (the roll spacings are 100 μm, 60 μm, and 25 μm in sequence, with three grindings) and ultrasound (22 kHz, 10 minutes), and then vacuum degassed (-0.07 MPa, 7 minutes). After adjusting the viscosity (75 Pa·s - 115 Pa·s), the conductive paste is obtained.

[0067] Comparative Example 3

[0068] Preparation of organic carrier: Accurately weigh 80 g of terpineol, 10 g of ethyl acetate, 5 g of ethyl cellulose, 2 g of defoamer (polyether defoamer PPG-1000) and 1 g of coupling agent (silane coupling agent KH560). Mix terpineol and ethyl acetate and stir for 4 minutes (280 revolutions per minute) to obtain mixture A. Add ethyl cellulose and stir for 6 minutes (300 revolutions per minute), then sequentially add the defoamer and the coupling agent and stir for 9 minutes. Stir in a constant temperature water bath at 72 °C for 32 minutes until the ethyl cellulose is dissolved to obtain mixture B, and naturally cool to room temperature to obtain the organic carrier.

[0069] Pretreatment of copper powder and preparation of composite conductive phase: Take 130 g of spherical copper powder with a particle size of 30 nm - 200 nm, ultrasonically clean (32 KHz) with 5% dilute sulfuric acid solution for 8 minutes, rinse with deionized water until the pH value is 6 - 7, then vacuum dry (52 °C, -0.075 MPa) for 1.3 hours, and then reduce and cool in a hydrogen atmosphere tube furnace (240 °C, hydrogen flow rate 55 mL / min) for 1.8 hours to obtain pretreated copper powder; Weigh the pretreated copper powder, copper fiber (diameter 10 nm - 300 nm, length 5 μm - 200 μm) and biological reducing agent (capsaicin) according to the mass ratio of 7:6:1 and grind in an agate mortar for 22 minutes (650 revolutions per minute) to obtain the composite conductive phase.

[0070] Preparation of composite conductive paste: Weigh the composite conductive phase, polyurethane resin and organic carrier (keep warm in a water bath at 46 °C for 9 minutes and stir) according to the mass ratio of 82:9:9. First, stir the composite conductive phase and the resin at a low speed (85 revolutions per minute) for 6 minutes, then add the organic carrier and increase the rotation speed to 260 revolutions per minute and stir for 17 minutes and vacuumize (-0.052 MPa) for mixing. The material is processed by a three-roll mill (roll spacing is 115 μm, 75 μm, 32 μm in sequence, grinding three times) and ultrasonic (26 kHz, 9 minutes), and then vacuum degassed (vacuum degree -0.07 MPa, 7 minutes) to adjust the viscosity (70 Pa·s - 110 Pa·s) to obtain the conductive paste.

[0071] Sample analysis

[0072] Take the conductive pastes prepared in Examples 1 - 3 and Comparative Examples 1 - 3 as samples, print each sample on the same substrate for conductive performance testing, antioxidant performance testing, and adhesion testing. At the same time, the scanning electron microscope image of the antioxidant copper fiber - copper powder composite conductive paste prepared in Example 2 after printing is as Figure 3 shown, indicating that a good conductive path is formed between the copper fiber and the copper powder.

[0073] Resistivity test: Use a four-probe ohmmeter to measure the resistance between the two electrodes.

[0074] Antioxidant performance test: The conductive films formed by curing the conductive pastes of each example and comparative example were placed in a constant temperature and humidity chamber at 85°C and 85% relative humidity for accelerated aging for 1000 - 1500 hours, and the resistivity change rate was measured every 200 hours.

[0075] Adhesion test: The adhesion of the conductive pastes of each example and comparative example to the flexible substrate (PET film) was tested using the cross-cut test.

[0076] Table 1 Results of conductive performance test, antioxidant performance test, and adhesion test

[0077]

[0078] Meanwhile, the antioxidant copper fiber - copper powder composite conductive paste prepared in the example can be cured at a low temperature of 200°C, and at the same time, the resistivity is relatively low.

[0079] The above data fully prove that the antioxidant copper fiber - copper powder composite conductive paste provided by the present invention has excellent performance and has broad application prospects in the field of electronics, especially in the field of flexible electronic devices.

[0080] The above-described examples have described the technical solutions of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and do not limit the present invention. Any modifications, supplements, or substitutions in a similar manner within the scope of the principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An antioxidant copper fiber - copper powder composite conductive paste, characterized in that, The components include a composite conductive phase, a thermosetting resin and an organic carrier; the mass ratio of the composite conductive phase, the thermosetting resin and the organic carrier is 6-10:1-3:1; The composite conductive phase is composed of paraffin-coated copper powder, modified copper fiber and a biological reducing agent; the mass ratio of the paraffin-coated copper powder, the modified copper fiber and the biological reducing agent is 5-10:5-10:1; The preparation method of the paraffin-coated copper powder is as follows: after cleaning the nano copper powder with a particle size of 30nm-200nm, heating and reducing it in a hydrogen atmosphere, further cooling it and then placing it in liquid paraffin, taking it out and drying to obtain the paraffin-coated copper powder; The preparation method of the modified copper fiber is as follows: after cleaning the copper fiber with a diameter of 10nm-300nm and a length of 5μm-200μm, placing it in a coupling agent solution, taking it out and drying to obtain the modified copper fiber; The biological reducing agent includes capsaicin.

2. The antioxidant copper fiber - copper powder composite conductive paste according to claim 1, wherein The viscosity of the antioxidant copper fiber-copper powder composite conductive paste is 70-130 Pa·s.

3. The antioxidant copper fiber - copper powder composite conductive paste according to claim 1, wherein The organic carrier is composed of the following components by weight percentage: Terpineol 70-90%; Ethyl acetate 5-15%; Ethyl cellulose 2-6%; Defoaming agent 1-4%; Coupling agent 1-5%.

4. The antioxidant copper fiber - copper powder composite conductive paste according to claim 1, wherein The thermosetting resin is selected from at least one of polyester resin, polyurethane resin or polymethyl methacrylate resin.

5. The antioxidant copper fiber - copper powder composite conductive paste according to claim 1, characterized in that, When preparing the paraffin-coated copper powder, the conditions for heating and reducing in a hydrogen atmosphere are: reduction temperature 250-280°C, hydrogen flow rate 50-70 mL / min, reduction time 1-2 h.

6. The antioxidant copper fiber - copper powder composite conductive paste according to claim 1, wherein The mass ratio of the copper powder after hydrogen reduction to the liquid paraffin is 10-50:

1.

7. The antioxidant copper fiber - copper powder composite conductive paste according to claim 1, wherein, When preparing the modified copper fiber, the coupling agent includes silane coupling agent, titanate coupling agent, aluminate coupling agent or zirconate coupling agent, and the concentration of the coupling agent solution is 1-5 wt%.

8. The antioxidant copper fiber - copper powder composite conductive paste according to claim 1, characterized in that, The biological reducing agent is capsaicin, or a combination of at least one of chitin, resveratrol, tannic acid, chlorogenic acid, caffeic acid, piperine and capsaicin.

9. The preparation method of the antioxidant copper fiber - copper powder composite conductive paste according to any one of claims 1 - 8, characterized in that, It includes the following steps: (1) Weigh the formulated amount of terpineol, ethyl acetate, ethyl cellulose, defoaming agent and coupling agent, and mix and dissolve them fully to obtain the organic carrier; (2) Weigh the formulated amount of paraffin-coated copper powder, modified copper fiber and biological reducing agent, and grind and mix them evenly to obtain the composite conductive phase; (3) Weigh the formulated amount of the composite conductive phase, thermosetting resin and organic carrier, mix them fully, transfer them to a three-roll mill, grind and refine them, then perform ultrasonic treatment, and adjust the viscosity after vacuum degassing to obtain the antioxidant copper fiber-copper powder composite conductive paste.

10. The application of the antioxidant copper fiber-copper powder composite conductive paste according to any one of claims 1-8 in the field of flexible electronic devices.

Images