An improved conductive silver paste composition and preparation method thereof

Abstract

The present invention relates to an improved conductive silver paste composition and a preparation method thereof, belonging to the technical field of conductive material preparation. The composition specifically comprises the following raw materials in parts by weight: 60-70 parts of silver-coated copper powder, 12-20 parts of graphene oxide, 0.5-1.5 parts of a conductive small molecule polymer, 5-8 parts of modified cellulose nanocrystals, 1-3 parts of an oxidant, 8-12 parts of an epoxy resin, and 5-10 parts of a diluent; wherein the conductive small molecule polymer is obtained by reacting aniline, benzaldehyde, and pyruvic acid; and the modified cellulose nanocrystals are obtained by modifying carboxylated cellulose nanocrystals with dopamine hydrochloride. The prepared conductive silver paste achieves synergistic optimization of conductivity, mechanical properties, and process compatibility through a composite system of silver-coated copper + graphene oxide + conductive polymer + epoxy resin, achieving both high cost-effectiveness and high performance, and is suitable for fields such as photovoltaics, flexible electronics, and automotive electronics.

Description

Technical Field

[0001] The present application relates to the technical field of conductive material preparation, and more specifically, to an improved conductive silver paste composition and a preparation method thereof. Background Art

[0002] Electronic paste is a basic electronic functional material with a wide range of applications in devices such as radio frequency identification (RFID), sensors, integrated circuits, and solar panels. With the advancement of electronic information technology, more and more new electronic devices are entering the market, driving the continuous development of electronic technology products towards high integration, miniaturization, intelligence, and precision.

[0003] Conductive pastes such as silver paste and aluminum-silver paste are currently the primary focus of electronic paste research. Commercial conductive silver pastes primarily consist of silver particles and an organic solvent, but fluctuations in silver prices significantly increase production costs. Furthermore, limited global silver ore resources hinder the sustainable development of the industry. Silver-coated copper (SCC) has been used in the past to replace silver in the preparation of conductive pastes, reducing silver consumption by over 50%. However, copper oxidation issues lead to unstable conductivity, limiting its large-scale application.

[0004] In addition, although pure silver powder has excellent conductivity, it is easy to agglomerate and requires high-temperature sintering, making it difficult to adapt to low-temperature processes such as flexible electronics. Existing conductive silver pastes are mostly imported (such as DuPont and Heraeus). Domestic silver powder has uneven particle size distribution and poor morphology control, resulting in low conductive network density and a square resistance generally higher than 15×10 -5 Ω·cm. In addition, the conductive filler graphene oxide is prone to restacking due to π-π stacking, has poor dispersion, and requires a complex modification process.

[0005] Based on the above statements, the present application provides an improved conductive silver paste composition and a preparation method thereof. Summary of the Invention

[0006] To address the issues raised in the background art, this application provides an improved conductive silver paste composition and a method for preparing the same. In the technical solution of the present invention, the resulting conductive silver paste achieves synergistic optimization of conductivity, mechanical properties, and process compatibility through a composite system of silver-coated copper + graphene oxide + conductive polymer + epoxy resin. This provides both high cost-effectiveness and high performance, making it suitable for applications in photovoltaics, flexible electronics, automotive electronics, and other fields.

[0007] This application provides an improved conductive silver paste composition and a preparation method thereof, which adopts the following technical solutions:

[0008] An improved conductive silver paste composition comprises the following raw materials in parts by weight:

[0009] 60-70 parts of silver-coated copper powder, 12-20 parts of graphene oxide, 0.5-1.5 parts of conductive small molecule polymer, 5-8 parts of modified cellulose nanocrystals, 1-3 parts of oxidant, 8-12 parts of epoxy resin and 5-10 parts of diluent;

[0010] Among them, the conductive small molecule polymer is obtained by reacting aniline, benzaldehyde and pyruvic acid;

[0011] The modified cellulose nanocrystals are obtained by modifying carboxylated cellulose nanocrystals with dopamine hydrochloride.

[0012] Furthermore, the conductive small molecule polymer is prepared by the following steps:

[0013] Aniline and benzaldehyde are added to ethanol, stirred, and then the temperature is raised to 75-85° C., and stirring is continued for 5-7 hours. Subsequently, pyruvic acid is added to the system, and the reaction is continued for 20-30 hours to obtain a conductive small molecule polymer.

[0014] Further preferably, the conductive small molecule polymer is prepared by the following steps:

[0015] Aniline and benzaldehyde are added to ethanol, stirred at 30-90 rpm for 10-15 minutes at room temperature, then the system temperature is raised to 75-85°C and stirred for 5-7 hours. Pyruvic acid is then added to the system and the reaction is continued for 20-30 hours to obtain a conductive small molecule polymer.

[0016] During the above reaction process, the aldehyde group on benzaldehyde is oxidized to a carbonyl group, and the amino group acts as a nucleophile to attack the carbonyl group, resulting in condensation to form an imine intermediate. Subsequently, the carboxylic acid group on pyruvic acid is protonated and attacks the empty orbital of the imine nitrogen atom, undergoing nucleophilic substitution with the nitrogen atom of the imine intermediate to form an amide bond. The formed amide bond is conjugated with the benzene ring and the imine bond through intramolecular cyclization, ultimately generating a closed-ring small molecule containing a conjugated π-electron system.

[0017] Furthermore, the usage ratio of aniline, benzaldehyde, pyruvic acid and ethanol is (1.3-1.5) g: (1.5-1.7) g: (1.3-1.4) g: 30 mL.

[0018] Furthermore, the modified cellulose nanocrystals are specifically prepared by the following steps:

[0019] Add carboxylated cellulose nanocrystals to MES buffer, stir for 10-20 minutes, then add EDC and NHS, continue stirring for 1-3 hours, add dopamine hydrochloride, adjust the pH value of the system to 5-6, continue stirring for 20-30 hours, dialyze and dry to obtain modified cellulose.

[0020] Further preferably, the modified cellulose nanocrystals are prepared by the following steps:

[0021] Add carboxylated cellulose nanocrystals to MES buffer and stir at 30-90 rpm for 10-20 minutes at room temperature. Then add EDC and NHS. Continue stirring for 1-3 hours, then add dopamine hydrochloride. Use 1 mol / L hydrochloric acid solution to adjust the pH value of the system to 5-6. Continue stirring for 20-30 hours. After dialysis for 2-3 days, freeze-dry the product to obtain modified cellulose.

[0022] During the above reaction process, the carboxyl groups on the carboxylated cellulose nanocrystals are activated using the EDC and NHS system, which then react with the amino groups on dopamine hydrochloride to form amide bonds. Dopamine hydrochloride is grafted onto the carboxylated cellulose nanocrystals, and catechol groups are introduced to prepare modified cellulose nanocrystals.

[0023] Furthermore, the usage amounts of carboxylated cellulose nanocrystals, MES buffer, EDC, NHS and dopamine hydrochloride are (0.5-1.0) g:50 mL:(0.7-0.8) g:(0.4-0.5) g:(0.6-0.8) g.

[0024] Furthermore, the silver-coated copper powder is specifically prepared by the following steps:

[0025] A1. The nano-copper powder was added to a sulfuric acid solution, stirred for 10-20 minutes, then the temperature was raised to 35-45 ° C, ultrasonically treated and filtered, the filtrate was added to a sodium hydroxide solution, the temperature was raised to 50-70 ° C, stirred for 10-20 minutes, filtered, and the filtrate was washed to obtain a pretreated nano-copper powder;

[0026] A2. Add silver nitrate to deionized water, stir, add ammonium citrate, and continue stirring to form a silver ion complex system; disperse the pretreated nano-copper powder in deionized water, add ammonia and sodium oleate, stir, and then add the silver ion complex system dropwise. After the addition is complete, continue stirring for 20-30 minutes, filter, and dry to obtain silver-coated copper powder.

[0027] Further preferably, the silver-coated copper powder is prepared by the following steps:

[0028] A1. The nano-copper powder was added to a 5-20wt% sulfuric acid solution in a mass volume ratio of (3-5) g: 20 mL, and stirred at a rate of 30-90 rpm for 10-20 minutes at room temperature. After the system temperature was raised to 35-45 ° C, ultrasonic treatment was performed for 2-4 hours at an ultrasonic frequency of 20-40 KHz, and then filtered. The filtrate was added to a 5-8wt% sodium hydroxide solution in a mass volume ratio of (3-5) g: 20 mL, the system temperature was raised to 50-70 ° C, stirred at a rate of 30-90 rpm for 10-20 minutes, filtered, and the filtrate was washed with deionized water until the pH value of the washing solution was 7 to obtain pretreated nano-copper powder;

[0029] A2. Silver nitrate was added to deionized water at a mass volume ratio of 1g: 10mL, stirred at room temperature at a rate of 30-90rpm for 10-15 minutes, ammonium citrate was added, and stirring was continued for 10-15 minutes to obtain a silver ion complex system; the pretreated nano-copper powder obtained in step A1 was dispersed in deionized water at a mass volume ratio of 1g: 10mL, ammonia and sodium oleate were added, and the system was stirred at a rate of 300-500rpm for 10-15 minutes, after which the silver ion complex system was added dropwise at a rate of 1-3mL / min. After completion of the addition, stirring was continued for 20-30 minutes, filtered, and the filtrate was vacuum dried at 20-30pa and 350-400°C for 40-60 minutes to obtain a silver-coated copper powder.

[0030] Furthermore, in step A2, the mass ratio of silver nitrate to ammonium citrate is 1:(0.1-0.3).

[0031] Furthermore, in step A2, the dosage ratio of the pretreated nano-copper powder, ammonia water, sodium oleate and silver ion complex system is (1-3) g: (3-10) mL: (0.1-0.3) g: (20-30) mL.

[0032] A method for preparing an improved conductive silver paste composition comprises the following steps:

[0033] Silver-coated copper powder, conductive small molecule polymer, modified cellulose nanocrystals, graphene oxide, epoxy resin and diluent in the formula are stirred at a rate of 300-500 rpm at room temperature, and then an oxidant is added, the system temperature is increased to 30-40°C, stirred for 1-3 hours, and then cooled to room temperature to obtain an improved conductive silver paste composition.

[0034] During the above reaction process, the conductive small molecule polymer, graphene oxide, and catechol functional groups on the modified cellulose nanocrystals are uniformly dispersed through π-π interactions. The oxidizing effect of the oxidant further promotes the amidation condensation on the conductive small molecule polymer and increases the content of the conjugated structure. At the same time, the use of the oxidant further increases the degree of oxidation of the graphene oxide and increases its binding effect with the matrix. The conversion of the catechol groups on the modified cellulose nanocrystals to catechol quinone is promoted. Through the coordination effect with the silver-coated copper powder, the dispersion effect of the silver-coated copper powder and other components in the system can be improved, sedimentation can be prevented, and the contact points between the silver-coated copper powder and the conductive matrix can be increased, thereby improving the conductive effect of the conductive silver paste from multiple aspects.

[0035] Furthermore, the oxidant is hydrogen peroxide.

[0036] In summary, this application has the following beneficial effects:

[0037] In the technical solution of the present invention, the conductive silver paste includes a composite system of silver-coated copper + graphene oxide + conductive small molecule polymer + epoxy resin. By using silver-coated copper powder instead of traditional silver powder raw materials, the preparation cost of the conductive silver paste is reduced; at the same time, aniline, benzaldehyde and pyruvic acid components are used to prepare polyaniline-based conductive small molecule polymers, which fill the gaps, form continuous conductive paths, improve conductivity, and make up for the defect that the silver-coated copper component has slightly insufficient conductivity compared to pure silver powder.

[0038] At the same time, by adding an oxidant component to the modified conductive silver paste composition, the oxidation of the catechol groups on the modified cellulose nanocrystals in the system can be promoted, thereby enhancing their complexation with the silver-coated copper. This can also promote the complete oxidation of the conductive small-molecule polymer. Under the action of the oxidant, the graphene oxide is in an extended state and can be distributed on the graphene oxide surface in the form of face-to-face interactions and chain entanglement with the conductive small-molecule polymer. This inhibits the restacking of the graphene oxide and reduces the π-π stacking distance between the graphene and the polymer, thereby improving charge transfer performance. At the same time, the graphene oxide has better dispersibility in the modified system and creates more contact points with the silver-coated copper metal.

[0039] In addition, the conductive small molecule polymer, graphene oxide and catechol functional groups on the modified cellulose nanocrystals are uniformly dispersed through π-π interactions. The oxidizing action of the oxidant further promotes the amidation condensation on the conductive small molecule polymer and increases the content of the conjugated structure. At the same time, the use of the oxidant further increases the degree of oxidation of the graphene oxide and increases its binding effect with the matrix. It promotes the transformation of the catechol groups on the modified cellulose nanocrystals into catechol quinone. Through the coordination effect with the silver-coated copper powder, the dispersion effect of the silver-coated copper powder and other components in the system can be improved, sedimentation can be prevented and the contact point between the silver-coated copper powder and the conductive matrix can be increased, thereby improving the conductive effect of the conductive silver paste from multiple aspects, achieving the coordinated optimization of conductivity, mechanical properties and process adaptability, and having both high cost performance and high performance, and is suitable for photovoltaics, flexible electronics and automotive electronics and other fields. DETAILED DESCRIPTION

[0040] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0041] The reagents used in the specific implementation of this application are all analytical grade, and:

[0042] The diluent used was butyl acetate.

[0043] The epoxy resin used is bisphenol A epoxy resin E-51.

[0044] The graphene oxide used is a single-layer graphene oxide with an average thickness of 0.5-1.2 nm and a diameter of 4-7 μm.

[0045] The carboxylated cellulose nanocrystal fibers used have a diameter of 410 nm, a length of 100-500 nm, and a cellulose type I crystal structure.

[0046] Example 1

[0047] An improved conductive silver paste composition comprises the following raw materials in parts by weight:

[0048] 60 parts of silver-coated copper powder, 12 parts of graphene oxide, 0.5 parts of conductive small molecule polymer, 5 parts of modified cellulose nanocrystals, 1 part of oxidant, 8 parts of epoxy resin and 5 parts of diluent;

[0049] The conductive small molecule polymer is prepared by the following steps:

[0050] Aniline and benzaldehyde were added to ethanol, stirred at 60 rpm for 15 minutes at room temperature, then the system temperature was raised to 75°C and stirred for 5 hours. Pyruvic acid was then added to the system and the reaction was continued for 20 hours to obtain a conductive small molecule polymer; the dosage ratio of aniline, benzaldehyde, pyruvic acid, and ethanol was 1.3 g:1.5 g:1.3 g:30 mL.

[0051] The modified cellulose nanocrystals are specifically prepared by the following steps:

[0052] Carboxylated cellulose nanocrystals were added to MES buffer and stirred at 60 rpm for 15 minutes at room temperature. EDC and NHS were then added. After stirring for 1 hour, dopamine hydrochloride was added. The pH value of the system was adjusted to 5 using 1 mol / L hydrochloric acid solution. Stirring was continued for 20 hours. After dialysis for 2 days, the product was freeze-dried to obtain modified cellulose. The amount of carboxylated cellulose nanocrystals, MES buffer, EDC, NHS and dopamine hydrochloride used was 0.5 g: 50 mL: 0.7 g: 0.4 g: 0.6 g.

[0053] Silver-coated copper powder is specifically prepared by the following steps:

[0054] A1. The nano-copper powder was added to a 5wt% sulfuric acid solution in a mass volume ratio of 3g: 20mL, stirred at 90rpm for 20 minutes at room temperature, and the system temperature was raised to 35°C, ultrasonicated for 2 hours at an ultrasonic frequency of 30KHz, and then filtered. The filtrate was added to a 5wt% sodium hydroxide solution in a mass volume ratio of 3g: 20mL, the system temperature was raised to 50°C, stirred at 30rpm for 10 minutes, filtered, and the filtrate was washed with deionized water until the pH value of the washing solution was 7 to obtain pretreated nano-copper powder;

[0055] A2. Silver nitrate was added to deionized water in a mass volume ratio of 1g:10mL, stirred at 90rpm for 15 minutes at room temperature, ammonium citrate was added, and stirring was continued for 15 minutes to obtain a silver ion complex system, the mass ratio of silver nitrate and ammonium citrate was 1:0.1; the pretreated nano-copper powder obtained in step A1 was dispersed in deionized water in a mass volume ratio of 1g:10mL, ammonia and sodium oleate were added, and the system was stirred at 500rpm for 10 minutes, followed by addition of the silver ion complex system at a rate of 2mL / min. After completion of the addition, stirring was continued for 30 minutes, filtered, and the filtrate was vacuum dried at 30pa and 400°C for 50 minutes to obtain a silver-coated copper powder; during the process, the amount ratio of the pretreated nano-copper powder, ammonia, sodium oleate and silver ion complex system was 1g:3mL:0.1g:20mL.

[0056] A method for preparing an improved conductive silver paste composition comprises the following steps:

[0057] Silver-coated copper powder, conductive small molecule polymer, modified cellulose nanocrystals, graphene oxide, epoxy resin and diluent in the formula were stirred at 500 rpm for 20 minutes at room temperature, and then an oxidant was added. The system temperature was raised to 30°C, and stirring was continued for 2 hours. After cooling to room temperature, an improved conductive silver paste composition was obtained, and the oxidant used was 70wt% hydrogen peroxide solution.

[0058] Example 2

[0059] An improved conductive silver paste composition comprises the following raw materials in parts by weight:

[0060] 65 parts of silver-coated copper powder, 16 parts of graphene oxide, 1.0 part of conductive small molecule polymer, 7 parts of modified cellulose nanocrystals, 2 parts of oxidant, 10 parts of epoxy resin and 7 parts of diluent;

[0061] The conductive small molecule polymer is prepared by the following steps:

[0062] Aniline and benzaldehyde were added to ethanol, stirred at 60 rpm at room temperature for 15 minutes, then the system temperature was raised to 80°C and stirring was continued for 6 hours. Pyruvic acid was then added to the system and the reaction was continued for 25 hours to obtain a conductive small molecule polymer; the dosage ratio of aniline, benzaldehyde, pyruvic acid, and ethanol was 1.4 g:1.6 g:1.35 g:30 mL.

[0063] The modified cellulose nanocrystals are specifically prepared by the following steps:

[0064] Carboxylated cellulose nanocrystals were added to MES buffer, stirred at 60 rpm for 15 minutes at room temperature, and then EDC and NHS were added. After stirring for 2 hours, dopamine hydrochloride was added, and the pH value of the system was adjusted to 5.5 using 1 mol / L hydrochloric acid solution. Stirring was continued for 25 hours. After dialysis for 2 days, the product was freeze-dried to obtain modified cellulose; the usage of carboxylated cellulose nanocrystals, MES buffer, EDC, NHS and dopamine hydrochloride was 0.8 g:50 mL:0.7 g:0.4 g:0.7 g.

[0065] Silver-coated copper powder is specifically prepared by the following steps:

[0066] A1. The nano-copper powder was added to a 10wt% sulfuric acid solution in a mass volume ratio of 4g: 20mL, stirred at 90rpm for 20 minutes at room temperature, and the system temperature was raised to 40°C, ultrasonicated for 3 hours at an ultrasonic frequency of 30KHz, and then filtered. The filtrate was added to a 6wt% sodium hydroxide solution in a mass volume ratio of 4g: 20mL, the system temperature was raised to 60°C, stirred at 60rpm for 5 minutes, filtered, and the filtrate was washed with deionized water until the pH value of the washing solution was 7 to obtain pretreated nano-copper powder;

[0067] A2. Silver nitrate was added to deionized water in a mass volume ratio of 1g: 10mL, stirred at 90rpm for 15 minutes at room temperature, ammonium citrate was added, and stirring was continued for 15 minutes to obtain a silver ion complex system, the mass ratio of silver nitrate and ammonium citrate was 1: 0.2; the pretreated nano-copper powder obtained in step A1 was dispersed in deionized water in a mass volume ratio of 1g: 10mL, ammonia and sodium oleate were added, and the system was stirred at 500rpm for 15 minutes, followed by addition of the silver ion complex system at a rate of 2mL / min. After completion of the addition, stirring was continued for 30 minutes, filtered, and the filtrate was vacuum dried at 30pa and 400°C for 50 minutes to obtain a silver-coated copper powder; during the process, the amount ratio of the pretreated nano-copper powder, ammonia, sodium oleate and silver ion complex system was 2g: 5mL: 0.2g: 25mL.

[0068] A method for preparing an improved conductive silver paste composition comprises the following steps:

[0069] Silver-coated copper powder, conductive small molecule polymer, modified cellulose nanocrystals, graphene oxide, epoxy resin and diluent in the formula were stirred at 500 rpm for 20 minutes at room temperature, and then an oxidant was added. The system temperature was raised to 35°C, and stirring was continued for 2 hours. After cooling to room temperature, an improved conductive silver paste composition was obtained, and the oxidant used was 70wt% hydrogen peroxide solution.

[0070] Example 3

[0071] An improved conductive silver paste composition comprises the following raw materials in parts by weight:

[0072] 70 parts of silver-coated copper powder, 20 parts of graphene oxide, 1.5 parts of conductive small molecule polymer, 8 parts of modified cellulose nanocrystals, 3 parts of oxidant, 12 parts of epoxy resin and 10 parts of diluent;

[0073] The conductive small molecule polymer is prepared by the following steps:

[0074] Aniline and benzaldehyde were added to ethanol, stirred at 60 rpm for 15 minutes at room temperature, then the system temperature was raised to 85°C and stirred for 7 hours. Pyruvic acid was then added to the system and the reaction was continued for 30 hours to obtain a conductive small molecule polymer; the dosage ratio of aniline, benzaldehyde, pyruvic acid, and ethanol was 1.5 g:1.7 g:1.4 g:30 mL.

[0075] The modified cellulose nanocrystals are specifically prepared by the following steps:

[0076] Carboxylated cellulose nanocrystals were added to MES buffer and stirred at 60 rpm for 15 minutes at room temperature. EDC and NHS were then added. Stirring was continued for 3 hours, and then dopamine hydrochloride was added. The pH value of the system was adjusted to 6 using 1 mol / L hydrochloric acid solution. Stirring was continued for 30 hours. After dialysis for 3 days, the product was freeze-dried to obtain modified cellulose. The usage of carboxylated cellulose nanocrystals, MES buffer, EDC, NHS and dopamine hydrochloride was 1.0 g:50 mL:0.8 g:0.5 g:0.8 g.

[0077] Silver-coated copper powder is specifically prepared by the following steps:

[0078] A1. The nano-copper powder was added to a 15wt% sulfuric acid solution in a mass volume ratio of 5g: 20mL, stirred at 90rpm for 20 minutes at room temperature, and the system temperature was raised to 45°C, ultrasonicated for 4 hours at an ultrasonic frequency of 30KHz, and then filtered. The filtrate was added to an 8wt% sodium hydroxide solution in a mass volume ratio of 5g: 20mL, the system temperature was raised to 70°C, stirred at 90rpm for 20 minutes, filtered, and the filtrate was washed with deionized water until the pH of the washing solution was 7 to obtain pretreated nano-copper powder;

[0079] A2. Silver nitrate was added to deionized water in a mass volume ratio of 1g:10mL, stirred at 90rpm for 15 minutes at room temperature, ammonium citrate was added, and stirring was continued for 15 minutes to obtain a silver ion complex system, the mass ratio of silver nitrate and ammonium citrate was 1:0.3; the pretreated nano-copper powder obtained in step A1 was dispersed in deionized water in a mass volume ratio of 1g:10mL, ammonia and sodium oleate were added, and the system was stirred at 500rpm for 15 minutes, followed by addition of the silver ion complex system at a rate of 2mL / min. After completion of the addition, stirring was continued for 30 minutes, filtered, and the filtrate was vacuum dried at 30pa and 400°C for 50 minutes to obtain a silver-coated copper powder; during the process, the amount ratio of the pretreated nano-copper powder, ammonia, sodium oleate and silver ion complex system was 3g:10mL:0.3g:30mL.

[0080] A method for preparing an improved conductive silver paste composition comprises the following steps:

[0081] Silver-coated copper powder, conductive small molecule polymer, modified cellulose nanocrystals, graphene oxide, epoxy resin and diluent in the formula were stirred at 500 rpm for 20 minutes at room temperature, and then an oxidant was added. The system temperature was raised to 40°C, and stirring was continued for 3 hours. After cooling to room temperature, an improved conductive silver paste composition was obtained, and the oxidant used was 70wt% hydrogen peroxide solution.

[0082] Comparative Example 1

[0083] The difference between this comparative example and Example 1 is that silver-coated copper powder is used instead of modified cellulose nanocrystals. Specifically, an improved conductive silver paste composition comprises the following raw materials in parts by weight:

[0084] 65 parts of silver-coated copper powder, 12 parts of graphene oxide, 0.5 parts of conductive small molecule polymer, 1 part of oxidant, 8 parts of epoxy resin and 5 parts of diluent.

[0085] Comparative Example 2

[0086] The difference between this comparative example and Example 1 is that silver-coated copper powder is used instead of graphene oxide. Specifically, an improved conductive silver paste composition comprises the following raw materials in parts by weight:

[0087] 72 parts of silver-coated copper powder, 0.5 parts of conductive small molecule polymer, 5 parts of modified cellulose nanocrystals, 1 part of oxidant, 8 parts of epoxy resin and 5 parts of diluent.

[0088] Comparative Example 3

[0089] The difference between this comparative example and Example 1 is that silver-coated copper powder is used instead of conductive small molecule polymer. Specifically, an improved conductive silver paste composition includes the following raw materials in parts by weight:

[0090] 60.5 parts of silver-coated copper powder, 12 parts of graphene oxide, 5 parts of modified cellulose nanocrystals, 1 part of oxidant, 8 parts of epoxy resin and 5 parts of diluent.

[0091] Comparative Example 4

[0092] The difference between this comparative example and Example 1 is that carboxymethyl cellulose nanocrystals are used instead of modified cellulose nanocrystals in this comparative example.

[0093] Comparative Example 5

[0094] The difference between this comparative example and Example 1 is that no oxidant is added to the improved conductive silver paste composition of this comparative example. Specifically, an improved conductive silver paste composition comprises the following raw materials in parts by weight:

[0095] 60 parts of silver-coated copper powder, 12 parts of graphene oxide, 0.5 parts of conductive small molecule polymer, 5 parts of modified cellulose nanocrystals, 8 parts of epoxy resin and 5 parts of diluent.

[0096] Performance Testing

[0097] The performance of the improved conductive silver paste compositions prepared in Examples 1-3 and Comparative Examples 1-3 of the present application is now tested.

[0098] The improved conductive silver paste compositions in different groups were mixed with the curing agent QNP1 (hexahydrotetramethylphthalic anhydride). The mass ratio of the curing agent to the epoxy resin in the formula was 1:8. The system was then dispersed at a high speed of 1000 rpm for 1 hour. After being treated in a vacuum degassing machine for 20 minutes, it was coated on a printed circuit board and cured at 100°C for 100 minutes. The resistivity test and stability test were then carried out. The specific test methods are as follows.

[0099] Resistivity test: Use a four-probe resistance tester to measure the square resistance of the silver paste electrode after curing. Each sample is tested 5 times and the average value is recorded.

[0100] Stability test: Place the sample in a 60°C / 90% RH environment for 1000 hours and observe the resistivity change. Each sample is tested 5 times in parallel and the average value is recorded.

[0101] The specific performance test results are shown in Table 1:

[0102] Table 1

[0103]

[0104] From the results shown in Table 1 above, it can be seen that the comprehensive performance of the improved conductive silver paste compositions prepared in Examples 1-3 of the present application is significantly better than the products prepared in Comparative Examples 1-6, that is, within the technical solution defined in the present application, the comprehensive performance of the conductive silver paste prepared is excellent.

[0105] From the results in the comparative example, we can see that silver-coated copper replaces pure silver powder, reducing silver consumption by more than 50%. At the same time, a continuous conductive network is formed through graphene oxide and conductive small molecule polymer, and the resistivity is close to that of pure silver paste (8-15×10 -5 Ω·cm); a conductive small molecule polymer is used as a component of the conductive silver paste. The polymer fills the gaps between silver particles, compensating for the insufficient conductivity of the silver-coated copper and reducing the resistivity by 15-20%. An oxidant is used in the preparation process to enhance the coordination effect with the silver-coated copper. At the same time, the graphene oxide stretches, inhibits stacking, improves dispersibility, and promotes the amidation condensation of the conductive small molecule polymer, strengthening the interfacial bonding strength with the substrate and improving stability.

[0106] Throughout the specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0107] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. An improved conductive silver paste composition comprising the following raw materials in parts by weight: 60-70 parts of silver-coated copper powder, 12-20 parts of graphene oxide, 0.5-1.5 parts of conductive small molecule polymer, 5-8 parts of modified cellulose nanocrystals, 1-3 parts of oxidant, 8-12 parts of epoxy resin and 5-10 parts of diluent; in, Conductive small molecule polymers are prepared by the following steps: Aniline and benzaldehyde are added to ethanol, stirred, and then the temperature is raised to 75-85°C. Stirring is continued for 5-7 hours, and then pyruvic acid is added to the system. The reaction is continued for 20-30 hours to obtain a conductive small molecule polymer. The ratio of aniline, benzaldehyde, pyruvic acid, and ethanol is (1.3-1.5) g: (1.5-1.7) g: (1.3-1.4) g: 30 mL. The modified cellulose nanocrystals are obtained by modifying carboxylated cellulose nanocrystals with dopamine hydrochloride.

2. The improved conductive silver paste composition according to claim 1, characterized in that: The modified cellulose nanocrystals are specifically prepared by the following steps: Add carboxylated cellulose nanocrystals to MES buffer, stir for 10-20 minutes, then add EDC and NHS, continue stirring for 1-3 hours, add dopamine hydrochloride, adjust the pH value of the system to 5-6, continue stirring for 20-30 hours, dialyze and dry to obtain modified cellulose.

3. The improved conductive silver paste composition according to claim 2, characterized in that: The usage amounts of carboxylated cellulose nanocrystals, MES buffer, EDC, NHS and dopamine hydrochloride are (0.5-1.0) g:50 mL:(0.7-0.8) g:(0.4-0.5) g:(0.6-0.8) g.

4. The improved conductive silver paste composition according to claim 1, characterized in that: The silver-coated copper powder is specifically prepared by the following steps: A1. The nano-copper powder was added to a sulfuric acid solution, stirred for 10-20 minutes, then the temperature was raised to 35-45 ° C, ultrasonically treated and filtered, the filtrate was added to a sodium hydroxide solution, the temperature was raised to 50-70 ° C, stirred for 10-20 minutes, filtered, and the filtrate was washed to obtain a pretreated nano-copper powder; A2. Add silver nitrate to deionized water, stir, add ammonium citrate, and continue stirring to form a silver ion complex system; disperse the pretreated nano-copper powder in deionized water, add ammonia and sodium oleate, stir, and then add the silver ion complex system dropwise. After the addition is complete, continue stirring for 20-30 minutes, filter, and dry to obtain silver-coated copper powder.

5. The improved conductive silver paste composition according to claim 4, characterized in that: In step A2, the mass ratio of silver nitrate to ammonium citrate is 1:(0.1-0.3).

6. The improved conductive silver paste composition according to claim 4, characterized in that: In step A2, the dosage ratio of the pretreated nano-copper powder, ammonia water, sodium oleate and silver ion complex system is (1-3) g: (3-10) mL: (0.1-0.3) g: (20-30) mL.

7. A method for preparing an improved conductive silver paste composition according to any one of claims 1 to 6, characterized in that: The specific steps include: Silver-coated copper powder, conductive small molecule polymer, modified cellulose nanocrystals, graphene oxide, epoxy resin and diluent in the formula are stirred at a rate of 300-500 rpm at room temperature, and then an oxidant is added, the system temperature is increased to 30-40°C, stirred for 1-3 hours, and then cooled to room temperature to obtain an improved conductive silver paste composition.

8. The method for preparing an improved conductive silver paste composition according to claim 7, wherein: The oxidant is hydrogen peroxide.

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