A high-performance conductive silver paste and preparation method thereof

Abstract

The present invention relates to a high-performance conductive silver paste and a preparation method thereof, belonging to the technical field of conductive pastes. The conductive silver paste comprises, by weight, 30-40 parts of micron-sized silver powder, 1.9-2.7 parts of nano-sized silver powder, 15-22 parts of Ag / MXene micropowder, 1.8-2.4 parts of a thixotropic agent, 25-35 parts of an organic resin, 1.3-1.8 parts of a curing agent, and 38-52 parts of a solvent. The Ag / MXene micropowder uses MXene nanosheets as a carrier, and a large number of silver clusters are loaded on the surface through a chemical reduction and roasting process, thereby increasing the contact probability between the sheet structure and the silver powder and improving the conductivity of the paste after curing. The MXene sheet provides good deformation recovery ability, and the surface of the MXene sheet is non-coated with small silver clusters, which act as a buffer, and has better structural stability during deformation, thereby maintaining stable conductivity. The paste has far-reaching application value in flexible conductive materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of conductive pastes, and in particular relates to a high-performance conductive silver paste and a preparation method thereof. Background Art

[0002] Conductive silver paste is a special functional material with conductive and adhesive properties. It is made by mixing silver powder, adhesive resin, additives and solvents as raw materials. It can be screen-printed according to the designed pattern. After curing, it provides good conductivity and is widely used in various electronic products.

[0003] With the rapid development of the 5G information age, the electronic information industry has undergone a comprehensive reform. Various new high-tech electronic products have gradually entered thousands of households and are widely favored by the public. At the same time, people have also put forward higher performance requirements for new electronic products, prompting electronic technology products to develop in the direction of lightness, thinness and flexibility. However, the mechanical properties and conductive properties of the conductive silver paste currently on the market that is compatible with flexible substrates are difficult to meet the performance requirements of flexible electronic devices, which restricts the further development of wearable electronic devices, flexible displays and other products. The mechanical properties of silver paste are determined by the binding resin in it. The better the flexibility of the resin, the better the bending resistance of the silver paste. The selection of high-performance binding resin can improve the flexibility of the silver paste to a certain extent. Silver powder is a conductive material, and its different properties such as morphology and particle size will affect the conductive properties of the silver paste. In order to obtain a conductive silver paste with high conductivity, silver powders with different morphologies and particle sizes are usually compounded to achieve high conductivity by reducing the contact resistance between the silver powders. Among them, the introduction of flaky conductive materials not only increases the contact area between the silver powders, but also forms a network structure in the silver paste, thereby increasing the flexibility of the silver paste, such as flaky silver powder, graphene and graphene derivatives. However, the bending recovery of flaky silver powder is poor, and the graphene sheet has high hardness and extremely high elastic modulus. The structure is easily destroyed during flexible deformation, which has a greater impact on conductivity. Summary of the Invention

[0004] In order to solve the technical problems mentioned in the background technology, the purpose of the present invention is to provide a high-performance conductive silver paste and a preparation method thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A high-performance conductive silver paste comprising, by weight:

[0007] 30-40 parts of micron-sized silver powder, 1.9-2.7 parts of nano-sized silver powder, 15-22 parts of Ag / MXene micropowder, 1.8-2.4 parts of thixotropic agent, 25-35 parts of organic resin, 1.3-1.8 parts of curing agent and 38-52 parts of solvent.

[0008] The Ag / MXene powder was prepared by the following method:

[0009] Step A1: Premix diethyl iminodiacetate, diallylamine, and anhydrous toluene under dry nitrogen protection, heat to 40-50°C, stir at 90-120 rpm, slowly add trimethylaluminum, and react for 4-5 hours. Then, continue heating and reflux for 1.5-2 hours, and quickly remove toluene by vacuum rotary evaporation to obtain an intermediate;

[0010] Furthermore, the feed ratio of diethyl iminodiacetate, diallylamine, trimethylaluminum and anhydrous toluene is 0.1 mol: 0.2 mol: 25-35 mg: 45-55 mL. Under the catalysis of trimethylaluminum, diethyl iminodiacetate and diallylamine undergo amine ester exchange to form a terminal polyolefin compound.

[0011] Step A2: Mix the intermediate, benzoin dimethyl ether and acetone, introduce nitrogen protection, heat to 45-55°C, apply stirring at 120-150 rpm and 100-150 W / m 2 UV irradiation, intermittent addition of ethanedithiol for 2.5-3.2 hours, after the reaction is completed, acetone is removed by rotary evaporation to obtain a coated modifier;

[0012] Furthermore, the feed ratio of the intermediate, ethanedithiol, benzoin dimethyl ether and acetone is 0.1 mol: 0.28-0.32 mol: 60-80 mg: 120-180 mL. Under ultraviolet light initiation, excess ethanedithiol is added to the terminal double bond of the intermediate to form a thiol-terminated small molecule network compound.

[0013] Step A3: Dissolve the coating modifier, dimethylacetamide, and ethanol, add MXene nanosheets, disperse them ultrasonically, and let them stand for 2 hours. Then, add silver nitrate solution, control the temperature of the water bath to 60-80°C, apply stirring at 30-50 rpm, and react at this temperature for 8-12 hours. After the reaction is completed, centrifuge the precipitate, wash it with water, and dry it to obtain a silver-loaded precursor.

[0014] Furthermore, the feed ratio of MXene nanosheets, coating modifier, silver nitrate, dimethylacetamide and ethanol is 10g:0.22-0.28g:0.35-0.4g:30-40mL:15-30mL. The coating modifier molecules are rich in amide groups and are fully dispersed in the dimethylacetamide system. Its multi-amide structure forms a chelating effect with the secondary amine and sulfide structure, forming a chelating force with the active transition metal element sites on the MXene sheet, and then enriched on the surface of the MXene sheet. The chelating structure without active sites captures the added silver ions and is reduced to elemental silver by the thiol group.

[0015] Step A4: Place the silver-loaded precursor in a nitrogen atmosphere furnace, first calcine at 420-460°C for 2.5-3h, then continue to heat up to 550-600°C and calcine for 1.5-2h, and then break up after cooling in the furnace to obtain Ag / MXene micropowder; under high-temperature calcination, organic matter decomposes and a large number of silver clusters are formed on the surface of the MXene nanosheets, increasing the contact probability with silver powder. The tiny silver clusters have a good buffering effect and are not easily destroyed during the deformation process, maintaining stable conductivity. Compared with traditional silver-coated products, the amount of silver used is lower.

[0016] Furthermore, the thixotropic agent is oleophilic fumed silica, which adjusts the thixotropic properties of the conductive silver paste and imparts good printability.

[0017] Furthermore, the organic resin is a polyurethane resin, which can be cured at low temperature, has good printability before curing, and has stable adhesion after curing.

[0018] Furthermore, the curing agent is an oxazolidine latent curing agent, which cooperates with the polyurethane resin to maintain good printability.

[0019] A method for preparing a high-performance conductive silver paste comprises the following steps: pre-mixing and dissolving an organic resin and a solvent, and then adding other raw materials and grinding and slurrying to obtain the conductive silver paste.

[0020] Beneficial effects of the present invention:

[0021] The present invention is based on a traditional conductive silver paste system, with polyurethane resin as a bonding material, silver powder as a basic conductive material, and independently developed Ag / MXene micropowder compounded. The obtained paste has low resistivity after curing, and the cured line has excellent flexural resistance. The Ag / MXene micropowder uses MXene nanosheets as a carrier, and undergoes an amine ester exchange reaction between diethyl iminodiacetate and diallylamine to prepare a compound with a multi-terminal olefin group, which is an intermediate. Then, ethanedithiol is added to the terminal double bond of the intermediate to form a small molecule network compound terminated by thiol, which is a coating modifier. The multi-amide structure in the network structure forms a chelating effect with the secondary amine and thioether structure, which can form a chelating force with the active transition metal element sites on the MXene sheet, and then evenly spread on the MXene sheet, and through liquid phase reduction Silver clusters are formed on the MXene sheets through the calcination process. Compared with the existing technology, the coating modifier contains only carbon, nitrogen, oxygen and sulfur elements, which are easy to thermally decompose, and the decomposition products have little effect on the conductivity of MXene. The silver clusters on the surface of the MXene sheet act like pins, increasing the contact probability between the sheet structure and the silver powder. Compared with flaky conductive materials, such as flaky silver powder, graphene, etc., it is easy to form more conductive channels and improve the conductivity of the slurry after curing. In addition, the MXene sheet has a more suitable elastic modulus and good deformation recovery ability. The surface of the MXene sheet is non-coated small silver clusters, which have a good buffering effect and better structural stability during deformation, thereby maintaining stable conductivity. It has far-reaching application value in flexible conductive materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 This is an electron microscope image of the Ag / MXene micropowder prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments 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.

[0025] Example 1, preparation of high-performance conductive silver paste, the specific implementation process is as follows:

[0026] (1) Preparation of Ag / MXene powder

[0027] Step A1: Premix diethyl iminodiacetate, diallylamine, and anhydrous toluene under dry nitrogen protection, heat to 50°C, stir at 120 rpm, slowly add trimethylaluminum and react for 4 hours, then continue to heat and reflux for 1.5 hours. The feed ratio of diethyl iminodiacetate, diallylamine, trimethylaluminum, and anhydrous toluene is 0.1 mol:0.2 mol:35 mg:55 mL. After the reaction is completed, the toluene is quickly removed by vacuum rotary evaporation to obtain an intermediate.

[0028] Step A2: Mix the intermediate, benzoin dimethyl ether and acetone, introduce nitrogen protection, heat to 55°C, apply stirring at 150 rpm and 150 W / m 2 Under ultraviolet irradiation, equal amounts of ethanedithiol were divided into four parts and added intermittently for 20 minutes. The addition of ethanedithiol was controlled to react for 2.5 hours. The feed ratio of the intermediate, ethanedithiol, benzoin dimethyl ether and acetone was 0.1 mol: 0.32 mol: 80 mg: 180 mL. After the reaction was completed, the acetone was removed by rotary evaporation to obtain a coated modifier.

[0029] Step A3: Take the coating modifier, dimethylacetamide and ethanol and mix them, add MXene nanosheets and ultrasonically disperse them, then let them stand for 2 hours, then add silver nitrate solution, control the temperature of the water bath to 80°C, apply stirring at 50 rpm, and react at constant temperature for 8 hours, wherein the MXene nanosheets are selected from commercially available XFK52 powder raw materials, and the feed ratio of MXene nanosheets, coating modifier, silver nitrate, dimethylacetamide and ethanol is 10g:0.28g:0.4g:40mL:15mL, and the concentration of the silver nitrate solution is 1mol / L. After the reaction is completed, the precipitate is centrifuged, washed with water, and dried to obtain a silver-loaded precursor.

[0030] Step A4: Place the silver-loaded precursor in a nitrogen atmosphere furnace, first calcine at 460°C for 2.5 hours, then continue to heat up to 600°C and calcine for 1.5 hours, and then break up after cooling in the furnace to obtain Ag / MXene micropowder.

[0031] (2) Preparation of conductive silver paste

[0032] Ingredients: raw materials are taken by weight, 30 parts of micron-grade silver powder, selected from ML-Ag-W05 raw material; 1.9 parts of nano-grade silver powder, selected from ML-Ag-N80 raw material; 15 parts of Ag / MXene micropowder, prepared in this embodiment; 1.8 parts of thixotropic agent, selected from VK-SP15G oleophilic fumed silica; 25 parts of organic resin, selected from 5836P polyurethane resin; 1.3 parts of curing agent, selected from TP-820 oxazolidine latent curing agent; 38 parts of solvent, selected from diethylene glycol butyl ether acetate;

[0033] Pulping: Premix and dissolve the organic resin and solvent, then add the remaining raw materials and grind them on a three-roll mill for 15 minutes to obtain a conductive silver paste.

[0034] Example 2, preparing high-performance conductive silver paste, the specific implementation process is as follows:

[0035] (1) Preparation of Ag / MXene powder

[0036] Step A1: Premix diethyl iminodiacetate, diallylamine, and anhydrous toluene under dry nitrogen protection, heat to 40°C, stir at 90 rpm, slowly add trimethylaluminum and react for 5 hours, then continue heating and reflux for 2 hours. The feed ratio of diethyl iminodiacetate, diallylamine, trimethylaluminum, and anhydrous toluene is 0.1 mol:0.2 mol:25 mg:45 mL. After the reaction is completed, vacuum rotary evaporation is performed to quickly remove toluene to obtain an intermediate.

[0037] Step A2: Mix the intermediate, benzoin dimethyl ether and acetone, introduce nitrogen protection, heat to 45°C, apply stirring at 120 rpm and 100 W / m 2 Under ultraviolet irradiation, take equal amounts of ethanedithiol and divide them into four parts, add them intermittently for 20 minutes, and control the addition of ethanedithiol to react for 3.2 hours. Among them, the feed ratio of intermediate, ethanedithiol, benzoin dimethyl ether and acetone is 0.1 mol: 0.28 mol: 60 mg: 120 mL. After the reaction, acetone is removed by rotary evaporation to obtain a coated modifier.

[0038] Step A3: Take the coating modifier, dimethylacetamide and ethanol and mix them, add MXene nanosheets and ultrasonically disperse them, then let them stand for 2 hours, then add silver nitrate solution, control the temperature of the water bath to 60°C, apply stirring at 30 rpm, and react at constant temperature for 12 hours, wherein the MXene nanosheets are selected from commercially available XFK52 powder raw materials, and the feed ratio of MXene nanosheets, coating modifier, silver nitrate, dimethylacetamide and ethanol is 10g:0.22g:0.35g:30mL:30mL, and the concentration of the silver nitrate solution is 1mol / L. After the reaction is completed, the precipitate is centrifuged, washed with water, and dried to obtain a silver-loaded precursor.

[0039] Step A4: Place the silver-loaded precursor in a nitrogen atmosphere furnace, first calcine at 420°C for 3 hours, then continue to heat up to 550°C and calcine for 2 hours, then break up after cooling in the furnace to obtain Ag / MXene micropowder.

[0040] (2) Preparation of conductive silver paste

[0041] Ingredients: raw materials are taken by weight, 40 parts of micron-grade silver powder, selected from ML-Ag-W05 raw material; 2.7 parts of nano-grade silver powder, selected from ML-Ag-N80 raw material; 22 parts of Ag / MXene micropowder, prepared in this embodiment; 2.4 parts of thixotropic agent, selected from VK-SP15G oleophilic fumed silica; 35 parts of organic resin, selected from 5836P polyurethane resin; 1.8 parts of curing agent, selected from TP-820 oxazolidine latent curing agent; 52 parts of solvent, selected from diethylene glycol butyl ether acetate;

[0042] Pulping: Premix and dissolve the organic resin and solvent, then add the remaining raw materials and grind them on a three-roll mill for 15 minutes to obtain a conductive silver paste.

[0043] Example 3, preparing high-performance conductive silver paste, the specific implementation process is as follows:

[0044] (1) Preparation of Ag / MXene powder

[0045] Step A1: Premix diethyl iminodiacetate, diallylamine, and anhydrous toluene under dry nitrogen protection, heat to 45°C, stir at 120 rpm, slowly add trimethylaluminum and react for 4.2 hours, then continue to heat and reflux for 1.8 hours. The feed ratio of diethyl iminodiacetate, diallylamine, trimethylaluminum, and anhydrous toluene is 0.1 mol:0.2 mol:30 mg:50 mL. After the reaction, vacuum rotary evaporation is performed to quickly remove toluene to obtain an intermediate.

[0046] Step A2: Mix the intermediate, benzoin dimethyl ether and acetone, introduce nitrogen protection, heat to 50°C, apply stirring at 150 rpm and 120 W / m 2 Under ultraviolet irradiation, equal amounts of ethanedithiol were divided into four parts and added intermittently for 20 minutes. The addition of ethanedithiol was controlled to react for 3 hours. The feed ratio of the intermediate, ethanedithiol, benzoin dimethyl ether and acetone was 0.1 mol: 0.3 mol: 70 mg: 150 mL. After the reaction was completed, the acetone was removed by rotary evaporation to obtain a coated modifier.

[0047] Step A3: Take the coating modifier, dimethylacetamide and ethanol and mix them, add MXene nanosheets and ultrasonically disperse them, then let them stand for 2 hours, then add silver nitrate solution, control the temperature of the water bath to 70°C, apply stirring at 50 rpm, and react at constant temperature for 10 hours, wherein the MXene nanosheets are selected from commercially available XFK52 powder raw materials, and the feed ratio of MXene nanosheets, coating modifier, silver nitrate, dimethylacetamide and ethanol is 10g:0.24g:0.35g:40mL:20mL, the concentration of silver nitrate solution is 1mol / L, and after the reaction is completed, centrifuge the precipitate, wash with water, and dry it to obtain a silver-loaded precursor.

[0048] Step A4: Place the silver-loaded precursor in a nitrogen atmosphere furnace, first calcine at 450°C for 3 hours, then continue to heat up to 580°C and calcine for 1.7 hours. After cooling in the furnace, break it up to obtain Ag / MXene micropowder.

[0049] (2) Preparation of conductive silver paste

[0050] Ingredients: raw materials are taken by weight, 35 parts of micron-grade silver powder, selected from ML-Ag-W05 raw material; 2.4 parts of nano-grade silver powder, selected from ML-Ag-N80 raw material; 20 parts of Ag / MXene micropowder, prepared in this embodiment; 2.2 parts of thixotropic agent, selected from VK-SP15G oleophilic fumed silica; 30 parts of organic resin, selected from 5836P polyurethane resin; 1.6 parts of curing agent, selected from TP-820 oxazolidine latent curing agent; 45 parts of solvent, selected from diethylene glycol butyl ether acetate;

[0051] Pulping: Premix and dissolve the organic resin and solvent, then add the remaining raw materials and grind them on a three-roll mill for 15 minutes to obtain a conductive silver paste.

[0052] In Comparative Example 1, referring to Example 3, the Ag / MXene powder was replaced with the same weight portion of ML-Ag-PW10 type flaky silver powder, and the rest of the implementation process was exactly the same.

[0053] Comparative Example 2, referring to Example 3, replaced the Ag / MXene powder with the same weight portion of XFDZ151 nanosilver modified reduced graphene oxide, and the rest of the implementation process was exactly the same.

[0054] The conductive silver paste prepared above was screen-printed on a PET substrate using a 300-mesh nylon brush with a line size of 0.4 mm × 100 mm. The sample was cured at 120°C for 2 h.

[0055] The resistivity of the line was tested using a four-probe tester, recorded as the initial resistivity ρ0. Referring to the YS / T 606-2006 standard, the sample was folded 180° perpendicular to its length, pressed flat with 2 kg for 10 minutes, and repeatedly bent 50 times. The resistivity of the line was then tested again, recorded as the bending resistivity ρ1. The resistance increase rate Φ was calculated as (ρ1-ρ0) / ρ0×100%. The specific test data is shown in Table 1:

[0056] Table 1

[0057] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 <![CDATA[ρ0 / Ω·cm]]> <![CDATA[4.27×10 -5 ]]> <![CDATA[4.07×10 -5 ]]> <![CDATA[3.92×10 -5 ]]> <![CDATA[5.83×10 -5 ]]> <![CDATA[4.67×10 -5 ]]> Φ / % 3.10 2.51 2.73 3.74 8.42

[0058] From the test results in Table 1, it can be seen that the conductive silver paste prepared in the embodiment has extremely low resistivity after curing, and the resistance increase rate after bending is low, showing excellent flexural resistance, and has far-reaching application value in flexible conductive materials.

[0059] Based on the test results in Table 1 above, the Ag / MXene powder prepared in Example 3 was observed by electron microscopy. Figure 1 As shown, it is lamellar with a large number of silver clusters attached to the surface.

[0060] 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.

Claims

1. A high-performance conductive silver paste, characterized in that: The composition comprises, by weight: 30-40 parts of micron-sized silver powder, 1.9-2.7 parts of nano-sized silver powder, 15-22 parts of Ag / MXene powder, 1.8-2.4 parts of thixotropic agent, 25-35 parts of organic resin, 1.3-1.8 parts of curing agent and 38-52 parts of solvent; The Ag / MXene powder was prepared by the following method: Step A1: Premix diethyl iminodiacetate, diallylamine, and anhydrous toluene under dry nitrogen, heat to 40-50°C, stir, and slowly add trimethylaluminum to react for 4-5 hours. Then, continue heating and reflux for 1.5-2 hours, and quickly remove toluene by rotary evaporation under reduced pressure to obtain an intermediate; Step A2: Mix the intermediate, benzoin dimethyl ether and acetone, introduce nitrogen protection, heat to 45-55°C, stir and apply 100-150W / m 2 UV irradiation, intermittent addition of ethanedithiol for 2.5-3.2 hours, after the reaction is completed, acetone is removed by rotary evaporation to obtain a coated modifier; Step A3: The coating modifier, dimethylacetamide and ethanol are mixed, MXene nanosheets are added for ultrasonic dispersion, and then the mixture is allowed to stand for 2 hours. Then, silver nitrate solution is added, and the temperature of the water bath is controlled at 60-80°C. The mixture is stirred and kept at this temperature for 8-12 hours. After the reaction is completed, the precipitate is centrifuged, washed with water and dried to obtain a silver-loaded precursor. Step A4: Place the silver-loaded precursor in a nitrogen atmosphere furnace, first calcine at 420-460°C for 2.5-3 hours, then continue to heat to 550-600°C and calcine for 1.5-2 hours. After cooling in the furnace, break it up to obtain Ag / MXene micropowder.

2. The high-performance conductive silver paste according to claim 1, characterized in that: The feed ratio of diethyl iminodiacetate, diallylamine, trimethylaluminum and anhydrous toluene is 0.1 mol: 0.2 mol: 25-35 mg: 45-55 mL.

3. The high performance conductive silver paste according to claim 2, characterized in that: The feed ratio of the intermediate, ethanedithiol, benzoin dimethyl ether and acetone is 0.1 mol: 0.28-0.32 mol: 60-80 mg: 120-180 mL.

4. The high-performance conductive silver paste according to claim 3, characterized in that: The feed ratio of MXene nanosheets, coating modifier, silver nitrate, dimethylacetamide and ethanol is 10g:0.22-0.28g:0.35-0.4g:30-40mL:15-30mL.

5. The high-performance conductive silver paste according to claim 1, characterized in that: The thixotropic agent is oleophilic fumed silica.

6. The high-performance conductive silver paste according to claim 1, characterized in that: The organic resin is polyurethane resin.

7. The high-performance conductive silver paste according to claim 1, characterized in that: The curing agent is an oxazolidine latent curing agent.

8. A method for preparing a high-performance conductive silver paste according to any one of claims 1 to 7, characterized in that: Specifically, the organic resin and the solvent are pre-mixed and dissolved, and then the remaining raw materials are added and ground into a slurry to obtain the conductive silver paste.

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