Anti-silver migration aqueous silver paste and preparation method thereof

Abstract

The invention provides an anti-silver migration aqueous silver paste and a preparation method thereof, and relates to the field of conductive silver paste production.The preparation method comprises the steps that a thickening agent and solvent water are mixed to obtain a 1-4 wt% thickening agent solution; the preparation method comprises the following steps: mixing water-based resin, solvent water, a fluorine-containing active agent, a thickening agent solution, a silane coupling agent and a defoaming agent according to a certain proportion to obtain a resin matrix solution; and mixing the resin matrix solution, silver powder and low-melting-point alloy powder according to a certain proportion, rolling and defoaming to obtain the silver migration resistant aqueous silver paste. Compared with the prior art, the silver migration resistance and the conductivity are excellent, and short circuit cannot be caused after long-term use.

Description

Technical Field

[0001] This invention relates to the field of conductive silver paste, and more specifically to an anti-silver migration aqueous silver paste and its preparation method. Background Technology

[0002] Against the backdrop of the rapid development of modern electronic technology, low-temperature water-based silver paste has been widely used in many fields such as printed electronics, flexible electronics, and photovoltaics due to its advantages such as curing at low temperatures, environmental friendliness, and ease of operation. For example, in printed electronics, it enables high-precision circuit printing; in flexible electronics, it meets the requirements of wearable devices for material flexibility and conductivity; and in the photovoltaic industry, it plays a key role in improving the photoelectric conversion efficiency and stability of batteries.

[0003] However, low-temperature aqueous silver paste faces several pressing issues in practical applications. Among these, silver migration is particularly prominent. When silver ions move between conductive paths in electronic devices, silver migration occurs, leading to electrical short circuits and severely impacting the reliability and stability of the electronic equipment. In applications such as touchscreens, low-temperature aqueous silver paste is used to screen-print conductive lines on substrates such as glass or polyester films. These traces typically have narrow spacing to achieve a narrow bezel design. The narrower the spacing, the greater the likelihood of silver ion migration and bridging between paths under specific conditions such as high humidity, high pressure, and high heat, ultimately damaging the device's functionality.

[0004] To meet the stringent requirements of the electronics industry for high conductivity of traditional low-temperature water-based silver paste, researchers currently mainly achieve this by increasing the amount of silver powder particles in the paste. However, this significantly increases the cost of conductive silver paste, seriously hindering the rapid development of related industries. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an anti-silver migration aqueous silver paste and its preparation method.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing an anti-silver migration aqueous silver paste includes the following steps:

[0008] S1. Mix the thickener with solvent water to obtain a 1-4 wt% thickener solution;

[0009] S2. Mix waterborne resin, solvent water, fluorinated surfactant, thickener solution, silane coupling agent and defoamer in a certain proportion to obtain resin matrix solution;

[0010] S3. Mix the resin matrix solution, silver powder, and low melting point alloy powder, roll them, and degas them to obtain an anti-silver migration aqueous silver paste.

[0011] Based on water-based silver paste, the resin matrix solution accounts for 38-42 wt%, the silver powder accounts for 55-59 wt%, and the low-melting-point alloy powder accounts for 1-4 wt%.

[0012] Furthermore, the proportions of each component in the resin matrix solution in step S2 are as follows:

[0013] Waterborne resin 45.3-46.3 wt%

[0014] Solvent: water 0.8-1.2wt%

[0015] Fluorine-containing surfactant 0.15-0.45wt%

[0016] Thickener 49.9-50.9 wt%

[0017] Silane coupling agent 1.0-1.5wt%

[0018] Defoamer 1.0-1.5wt%

[0019] As the core film-forming substance, the content of water-based resin determines the coating's performance (such as adhesion, weather resistance, and mechanical strength). Water, as a diluent / dispersion medium for water-based silver paste, helps adjust solution viscosity and avoids environmental problems associated with organic solvents. Fluorinated surfactants, as active agents, significantly reduce solution surface tension, improve wetting ability on the substrate, and enhance the coating's stain and water resistance. Thickeners, as key components for adjusting solution viscosity, maintain the dispersion stability of each component by increasing system consistency, preventing stratification. Silane coupling agents, as interface modifiers, react with inorganic substrates on one end and bind to water-based resin on the other, acting as a "bridge" to significantly improve the adhesion between the coating and the substrate, while also enhancing the coating's resistance to damp heat and aging. Defoamers prevent "pinholes" and "bubble marks" from appearing in the coating after drying, ensuring a smooth and dense coating surface.

[0020] Furthermore, the thickener is at least one of hydroxypropyl methylcellulose, methylcellulose, sodium alginate, polyvinyl alcohol, wax gel, organic modified bentonite, and fumed silica.

[0021] Furthermore, in step S1, the mixing water temperature is 40-80℃, and the stirring speed is 300-500 r / min.

[0022] Furthermore, the waterborne resin is at least one of waterborne acrylic resin, waterborne polyurethane resin, waterborne epoxy resin, waterborne alkyd resin, and waterborne polyester resin.

[0023] Furthermore, the fluorinated surfactant includes at least one of anionic fluorinated surfactants, cationic fluorinated surfactants, and nonionic fluorinated surfactants.

[0024] Furthermore, the silane coupling agent is at least one of KH-550, KH-560, KH-570, and KH-792.

[0025] Furthermore, the defoamer is at least one of the following: silicone defoamer A-893, polyether-modified silicone defoamer BNK-G309, and mineral oil-based defoamer BNK-G308.

[0026] Furthermore, the silver powder is at least one of spherical silver powder, flake silver powder, dendritic silver powder, and nano silver powder.

[0027] Furthermore, the low-melting-point alloy powder is Sn. 42 Bi 58 Sn 52 In 48 Sn 63 Pb 37 In 67 Bi 33 At least one of them.

[0028] Preferably, the size of the low-melting-point alloy powder is 0.5-5 μm.

[0029] Furthermore, the rolling process specifically includes: adjusting the feed roll gap and the discharge roll gap to 70-50µm and 50-30µm respectively, and rolling 2-4 times; adjusting the two roll gaps to 50-30µm and 25-10µm, and rolling 2-4 times; adjusting the two roll gaps to 20-10µm and 10-5µm, and rolling 3-5 times; adjusting the two roll gaps to 10-5µm and 5-1µm, and rolling 4-6 times, with the rotation speed at each stage being 150-600rpm.

[0030] Furthermore, in step S3, degassing is performed under a vacuum of -98 kPa, at a speed of 1500-2600 rpm, with stirring for 0.5-2.5 min.

[0031] The anti-silver migration aqueous silver paste prepared by the above method contains the following components:

[0032] Resin matrix solution 38%-42%

[0033] Silver powder 55%-59%

[0034] 1-4% of low melting point alloy powder

[0035] In this process, the resin matrix solution acts as a "binder and dispersant" for the water-based silver paste. Its core function is to uniformly encapsulate and disperse the silver powder and low-melting-point alloy powder, dry them to form a continuous film, and firmly bond the functional powder to the substrate surface, thus helping to improve the weather resistance of the coating. The silver powder, as the "core functional component" of the silver paste, provides the core performance of the coating due to its high electrical and thermal conductivity. The low-melting-point alloy powder plays a role in "performance optimization and process assistance." Its low melting point allows it to melt at lower temperatures. On the one hand, it can fill the gaps between silver powder particles, reduce the "breakpoints" in the conductive path, and improve the overall conductivity efficiency. On the other hand, it can cut off the diffusion channels for silver migration, reduce the contact between silver and the external medium, reduce the generation of silver ions, avoid local electric field concentration, and slow down the migration momentum.

[0036] The selection of each component and the proportion of each component affect the performance of the water-based silver paste. When the proportion of each component is within the range of this invention, the water-based silver paste prepared by this invention has low resistivity and strong resistance to silver migration after curing. Even under harsh operating environments such as long-term humid heat and high electric field, it can effectively inhibit the problems of conductivity decay and substrate corrosion caused by silver ion migration. In addition, the excellent bonding and dispersion characteristics of the resin matrix solution can also make the cured silver paste coating firmly bonded to the substrate, making it less prone to peeling and cracking, and further improving the weather resistance of the coating, thus ensuring the long-term stability of the silver paste performance.

[0037] The beneficial effects of this invention are as follows: adding low-melting-point alloy powder to the silver paste system melts the low-melting-point alloy powder, thereby forming a metallurgical connection between the silver powder particles. This not only enhances the conductivity of the silver paste but also reduces the mobility of silver ions, thus improving the silver paste's resistance to silver migration. The solidified portion of the molten alloy powder encapsulates the silver powder and water-based resin, reducing the risk of silver powder detaching from the resin matrix and improving the coating's scratch resistance. There is no need to increase the curing temperature; the alloy melting can be achieved using only the existing drying process of the water-based silver paste, completing the filling of the gaps between the silver powder particles and preventing the film from curling. Attached Figure Description

[0038] Figure 1 The images show SEM images of the cured silver paste circuits in Example 3 and Comparative Example 1. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0041] Unless otherwise specified, all components mentioned in the following examples were purchased from commercial sources.

[0042] Example 1

[0043] Add 0.2g of solid HPMC to 9.8g of solvent water and stir at 80℃ for 3h. When the solution becomes turbid and no bubbles are present, cool to room temperature and continue stirring at 400r / min until it becomes colorless and transparent and no longer gel-like, to obtain a 2wt% thickener HPMC aqueous solution. Store in a sealed, cool place.

[0044] Take 10g of the above 2wt% HPMC aqueous solution, add 0.2g of solvent water and 9.1g of 30wt% aqueous polyurethane resin, stir until colorless and transparent, then add 0.25g of polyether modified silicone defoamer BNK-G309 and 0.06g of nonionic fluorinated surfactant, stir until no bubbles are present, and finally add 0.25g of silane coupling agent KH-550. The stirring speed is 300r / min, the stirring time is 20min, and the mixture is sonicated for 30min to obtain a uniformly dispersed aqueous resin solution (the ratio of the aqueous resin matrix solution is shown in Table 1).

[0045] Table 1

[0046]

[0047] Take 4g of the above-mentioned uniformly dispersed aqueous resin solution, 5.9g of flake silver powder, and 0.1g of low-melting-point alloy powder Sn. 42 Bi 58 The mixture is stirred and mixed, and then subjected to a rolling process: the feed roller gap and the discharge roller gap are adjusted to 70-50um and 50-30um respectively, and rolled 2-4 times; the two roller gaps are adjusted to 50-30um and 25-10um, and rolled 2-4 times; the two roller gaps are adjusted to 20-10um and 10-5um, and rolled 3-5 times; the two roller gaps are adjusted to 10-5um and 5-1um, and rolled 4-6 times. The speed at each stage is 150-600rpm to obtain a premixed material, which is then subjected to a degassing treatment: 1500-2600rpm speed, stirring for 0.5-2.5min, vacuum degree -98Kpa, to obtain water-based silver paste.

[0048] Example 2

[0049] The 5.9g of flake silver powder and 0.1g of low-melting-point alloy powder Sn from Example 1 were used. 42 Bi 58 Replace with "5.8g of flake silver powder and 0.2g of low-melting-point alloy powder Sn". 42 Bi 58 "Other components and processes remain unchanged."

[0050] Example 3

[0051] The 5.9g of flake silver powder and 0.1g of low-melting-point alloy powder Sn from Example 1 were used. 42 Bi 58 Replace with "5.7g of flake silver powder and 0.3g of low-melting-point alloy powder Sn". 42 Bi 58 "Other components and processes remain unchanged."

[0052] Example 4

[0053] The 5.9g of flake silver powder and 0.1g of low-melting-point alloy powder Sn from Example 1 were used. 42 Bi 58 Replace with "5.6g of flake silver powder and 0.4g of low-melting-point alloy powder Sn". 42 Bi 58 "Other components and processes remain unchanged."

[0054] Example 5

[0055] In Example 3, “Sn” 42 Bi 58 Replace with "Sn" 52 In 48 "Other components and processes remain unchanged."

[0056] Example 6

[0057] In Example 3, “Sn” 42 Bi 58 Replace with "In" 67 Bi 33 "Other components and processes remain unchanged."

[0058] Example 7

[0059] Add 0.2% solid polyvinyl alcohol to 9.8% solvent water and stir at 40°C for 4 hours. When the solution becomes turbid and free of bubbles, cool to room temperature and continue stirring at 500 r / min until it becomes colorless, transparent and free of jelly, to obtain a 2 wt% thickener polyvinyl alcohol aqueous solution. Store in a sealed, cool place.

[0060] Take 10.1g of the above-mentioned 2wt% polyvinyl alcohol aqueous solution, 0.17g of solvent water and 9g of 30wt% waterborne polyurethane resin, stir until colorless and transparent, then add 0.2g of organosilicon defoamer A-893 and 0.08g of anionic fluorinated surfactant, stir until no bubbles are present, and finally add 0.3g of silane coupling agent KH-570. The stirring speed is 300r / min, the stirring time is 20min, and the mixture is sonicated for 20min to obtain a uniformly dispersed waterborne resin solution (the ratio of the waterborne resin matrix solution is shown in Table 2).

[0061] Table 2

[0062]

[0063] Take 3.8g of the above-mentioned uniformly dispersed aqueous resin solution, 5.9g of flake silver powder, and 0.3g of low-melting-point alloy powder Sn. 42 Bi 58 The mixture is stirred and mixed, and then subjected to a rolling process: the feed roller gap and the discharge roller gap are adjusted to 70-50um and 50-30um respectively, and rolled 2-4 times; the two roller gaps are adjusted to 50-30um and 25-10um, and rolled 2-4 times; the two roller gaps are adjusted to 20-10um and 10-5um, and rolled 3-5 times; the two roller gaps are adjusted to 10-5um and 5-1um, and rolled 4-6 times. The speed at each stage is 150-600rpm to obtain a premixed material, which is then subjected to a degassing treatment: 1500-2600rpm speed, stirring for 0.5-2.5min, vacuum degree -98Kpa, finally to obtain water-based silver paste.

[0064] Example 8

[0065] Add 0.8g of solid polyvinyl alcohol to 9.2g of solvent water and stir at 40°C for 4 hours. When the solution becomes turbid and no bubbles are present, cool to room temperature and continue stirring at 500r / min until it becomes colorless, transparent and no longer gel-like, to obtain a 2wt% thickener polyvinyl alcohol aqueous solution. Store in a sealed, cool place.

[0066] Take 9.91g of the above-mentioned 2wt% polyvinyl alcohol aqueous solution, 0.23g of solvent water and 9.2g of 20wt% waterborne polyurethane resin, stir until colorless and transparent, then add 0.29g of organosilicon defoamer A-893 and 0.03g of cationic fluorinated surfactant, stir until no bubbles are formed, and finally add 0.2g of silane coupling agent KH-570. The stirring speed is 300r / min, the stirring time is 20min, and the mixture is sonicated for 20min to obtain a uniformly dispersed waterborne resin solution (the ratio of the waterborne resin matrix solution is shown in Table 3).

[0067] Table 3

[0068]

[0069] Take 4.2g of the above-mentioned uniformly dispersed aqueous resin solution, 5.6g of flake silver powder, and 0.2g of low-melting-point alloy powder Sn. 42 Bi 58 The mixture is stirred and mixed, and then subjected to a rolling process: the feed roller gap and the discharge roller gap are adjusted to 70-50um and 50-30um respectively, and rolled 2-4 times; the two roller gaps are adjusted to 50-30um and 25-10um, and rolled 2-4 times; the two roller gaps are adjusted to 20-10um and 10-5um, and rolled 3-5 times; the two roller gaps are adjusted to 10-5um and 5-1um, and rolled 4-6 times. The speed at each stage is 150-600rpm to obtain a premixed material, which is then subjected to a degassing treatment: 1500-2600rpm speed, stirring for 0.5-2.5min, vacuum degree -98Kpa, finally to obtain water-based silver paste.

[0070] Comparative Example 1

[0071] The 5.9g of flake silver powder and 0.1g of low-melting-point alloy powder Sn from Example 1 were used. 42 Bi 58 Replace it with "6g of flake silver powder".

[0072] Table 4 shows the ingredient list for the water-based silver paste of Examples 1-8 and Comparative Example 1.

[0073] Table 4

[0074]

[0075] Performance testing

[0076] The aqueous silver pastes prepared in Examples 1-8 and Comparative Example 1 were screen-printed onto PET films. The screen-printed silver paste lines had a width of 1 mm and a line spacing of 250 μm. The lines were then dried in an oven at 150°C for 30 min to obtain the cured silver paste lines.

[0077] 1. The conductivity properties of the cured silver paste circuits are compared as shown in Table 5.

[0078] Table 5. Conductivity test results

[0079]

[0080] Table 5 shows that the formulation of Comparative Example 1 is "4g water-based resin matrix + 6g silver powder" (without any low-melting-point alloys), and its resistivity is The resistivity of the cured silver paste circuits in Examples 1-8 (all with added low-melting-point alloys) is not higher than that of other examples. The resistivity of Comparative Example 1 is much higher than that of Examples 1-8, indicating that the addition of low-melting-point alloy in this invention reduces the resistivity of water-based silver paste and improves its conductivity.

[0081] Depend on Figure 1 As far as we know, Sn 42 Bi 58 The introduction of this technology has led to a key optimization of product performance. Compared with the micropores, local cracks, and structural inhomogeneities commonly found on the surface of Comparative Example 1, the surface density of Example 3 has been greatly improved. Not only is the overall structure more uniform and flat, but there are also no obvious pores or discontinuous areas. More importantly, this improvement in density directly provides core support for conductivity, successfully constructing a more continuous and low-impedance conductive path. This effectively avoids the problems of interface blockage and loss during current transmission, and the integrity and transmission efficiency of the conductive path are significantly better than those of Comparative Example 1.

[0082] 2. The anti-silver migration properties of the cured silver paste circuits are compared and shown in Table 6.

[0083] For the anti-silver migration test, the test conditions are: 85℃ / 85%RH for 1000h, and the line-to-line resistance after the test must be >10. 8 Ω.

[0084] Table 6. Test results of anti-silver migration performance

[0085]

[0086] Table 6 shows that all examples 1-8 included low-melting-point alloy powder, and their anti-silver migration performance met the standard; while Comparative Example 1, containing only resin and silver powder (no alloy), did not meet the anti-silver migration performance standard. This indicates that adding low-melting-point alloy powder improves the interfacial bonding of silver powder: melting at low temperatures (such as Sn) 42 Bi 58 Melting point ≈ 138℃, In 67 Bi 33 With a melting point of approximately 72°C, it fills the gaps between silver powder particles, reduces interparticle contact resistance, and improves conductivity continuity; it is suitable for low-temperature processes: avoiding damage to the substrate caused by high-temperature sintering, while ensuring the formation of a stable conductive path at low temperatures.

[0087] Select low melting point alloy powder—Sn 42 Bi 58 The anti-silver migration principle of the aqueous silver paste obtained by the preparation method of this application is illustrated by example.

[0088] 1. Sacrificial anode protection: reducing Ag at the source + Dissolution (electrochemical mechanism)

[0089] The standard electrode potential of silver is Ag. + / Ag ≈ 0.80V (high potential, easily reduced, difficult to oxidize), while Sn and Bi have even lower potentials: Sn² + / Sn ≈ -0.14V, Bi³ + / Bi ≈ 0.20V (both lower than Ag, making it more easily oxidized and dissolved).

[0090] When Sn 42 Bi 58 When powder is added to silver paste, the circuit solidifies to form an "Ag-Sn-Bi" microstructure. Under an electric field and humidity environment, Sn and Bi preferentially act as "sacrificial anodes" and undergo oxidation and dissolution (releasing Sn²⁺). + Bi³ + Ag is protected as the "cathode"—due to the preferential corrosion of Sn / Bi, Ag is almost never oxidized to Ag. + This cuts off the "raw materials" (Ag) for silver migration at its source. + ).

[0091] 2. Low melting point fills pores: blocks Ag + Migration channels (microstructure optimization)

[0092] The traditional problem with silver paste circuits is that after low-temperature curing (such as 80-150℃ commonly used in flexible electronics), micron-sized pores easily remain between silver particles. These pores can adsorb moisture and residual ions, forming Ag. + The "highway" of migration.

[0093] Sn 42 Bi 58 Its melting point is only 138℃, which perfectly matches the low-temperature curing process of silver paste: during the curing process, the temperature rises to 150-200℃ (slightly higher than Sn). 42 Bi 58 At its melting point, the alloy powder melts into a liquid metallic phase and fills the pores between silver particles under capillary action; upon cooling, the liquid Sn... 42 Bi 58 Solidification forms a continuous metal skeleton, tightly "welding" the silver particles together, increasing the density of the silver paste circuitry by 30%-50% (significantly reducing porosity).

[0094] After the pores are filled with the metallic phase, water vapor and impurity ions cannot enter, Ag + Without the "electrolyte channels" for migration, the migration rate drops significantly.

[0095] 3. Interferes with dendrite growth: Prevents the formation of Ag short-circuit paths.

[0096] Even with a small amount of Ag +Overcoming the above obstacles to migrate, Sn 42 Bi 58 Silver dendrite growth can still be suppressed in two ways:

[0097] Ion competition precipitation: Sn 2+ Bi 3+ migration rate and Ag + Similarly, under the influence of an electric field, Sn will compete with Ag+ to migrate towards the negative electrode; due to... 2+ / Bi 3+ The lower reduction potential (easier precipitation) will preferentially deposit on the negative electrode surface, occupying Ag. + The required "active sites" are restored to prevent the continuous growth of Ag metal dendrites;

[0098] Structural physical obstacles: cured Sn 42 Bi 58 The metallic phase is distributed in a network within the silver paste, forming a "physical barrier"—even if trace amounts of Ag dendrites are generated, they are difficult to penetrate the dense Sn-Bi metal network and cannot form a short-circuit channel across the circuit.

[0099] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing an anti-silver-migration aqueous silver paste, characterized by, Comprising the following steps: S1, mixing thickening agent with solvent water to obtain 1-4wt% thickening agent solution; S2, mixing water-based resin, solvent water, fluorine-containing active agent, thickening agent solution, silane coupling agent, defoaming agent in a certain proportion to obtain resin matrix solution; S3, taking resin matrix solution, silver powder, low melting point alloy powder for mixing, rolling, defoaming to obtain anti-silver migration water-based silver paste; Among them, based on water-based silver paste, resin matrix solution accounts for 38-42wt%, silver powder accounts for 55-59wt%, and low melting point alloy powder accounts for 1-4wt%.

2. The method of preparing an anti-silver-migrating aqueous silver paste according to claim 1, characterized by: The proportion of each component in the resin matrix solution in step S2 is: Water-based resin 45.3-46.3wt% Solvent water 0.8-1.2wt% Fluorine-containing active agent 0.15-0.45wt% Thickening agent 49.9-50.9wt% Silane coupling agent 1.0-1.5wt% Defoaming agent 1.0-1.5wt% 。 3. The method of preparing an anti-silver-migrating aqueous silver paste according to claim 1, characterized by: The thickening agent is at least one of hydroxypropyl methyl cellulose, methyl cellulose, sodium alginate, polyvinyl alcohol, wax gel, organically modified bentonite, and fumed silica.

4. The method of preparing an anti-silver-migration aqueous silver paste according to claim 1, characterized by: The mixing water temperature in step S1 is 40-80℃, and the stirring speed is 300-500r / min.

5. The method of preparing an anti-silver-migration aqueous silver paste according to claim 1, characterized by: The water-based resin is at least one of water-based acrylic resin, water-based polyurethane resin, water-based epoxy resin, water-based alkyd resin, and water-based polyester resin.

6. The method of preparing an anti-silver-migration aqueous silver paste according to claim 1, characterized by: The silver powder is at least one of spherical silver powder, flaky silver powder, dendritic silver powder, and nano silver powder.

7. The method of preparing an anti-silver-migration aqueous silver paste according to claim 1, characterized by: The low melting point alloy powder is Sn 42 Bi 58 , Sn 52 In 48 , Sn 63 Pb 37 , In 67 Bi 33 , and at least one of them.

8. The method of preparing an anti-copper migration aqueous silver paste according to claim 7, characterized by: The size of the low melting point alloy powder is 0.5-5um.

9. The method of preparing an anti-silver-migration aqueous silver paste according to claim 1, characterized by: The defoaming in step S3 is under a vacuum degree of-98Kpa, a stirring speed of 1500-2600rpm, and stirring for 0.5-2.5min.

10. An aqueous silver paste prepared according to the method of any one of claims 1 to 9, characterized in that, Comprising the following components: Resin matrix solution 38-42wt% Silver powder 55-59wt% Low melting point alloy powder 1-4wt%.

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