Conductive silver paste for soldering electronic components and method for preparing the same

Abstract

The application discloses a kind of electronic component tin soldering electrically-conductive silver paste and preparation method thereof, and is related to the technical field of electrically-conductive silver paste.The electrically-conductive silver paste for electronic component tin soldering and the preparation method thereof, by pretreating nano silver powder with organic acid, the carboxyl group in the organic acid interacts with the surface of nano silver powder, forming a coating layer, preventing silver powder from agglomerating, making it uniformly dispersed in the paste, improving the stability of the paste, reducing the resistance, and the treated nano silver powder contacts each other more closely, forming a good conductive network, thereby improving the conductivity of the conductive paste;And in the air, nano silver powder is easily oxidized, an organic acid forms a protective film on the surface of silver powder, blocks oxygen and moisture, reduces the oxidation rate of silver powder, improves the oxidation resistance of the paste and prolongs the service life.

Description

Technical Field

[0001] This invention relates to the field of conductive silver paste technology, specifically to a conductive silver paste for soldering electronic components and its preparation method. Background Technology

[0002] Chinese Patent Publication No. CN118398278A discloses a conductive silver paste and a method for preparing the conductive silver paste. The method includes the following steps: S1: preparing a reducing solution; S2: preparing an oxidizing solution; S3: preparing a neutralizing solution; S4: performing a redox reaction to obtain a silver-containing solution; S5: post-processing the silver-containing solution; S6: preparing the conductive silver paste. This application can prepare conductive silver paste with low sheet resistance, and the preparation method is simple, easily repeatable, and yields stable results. However, the adhesion and conductivity of the conductive silver paste prepared by the above-mentioned prior art solutions need further improvement. Therefore, this invention provides a conductive silver paste for soldering electronic components and its preparation method to solve the above problems. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a conductive silver paste for soldering electronic components and its preparation method, thus solving the problems mentioned in the background section.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solution: a conductive silver paste for soldering electronic components, comprising the following raw materials in parts by weight: 60-85 parts of nano silver powder, 2-5 parts of polyurethane prepolymer, 0.8-2 parts of functionalized graphene, and 8-10 parts of silver-copper powder.

[0005] A method for preparing conductive silver paste for soldering electronic components, specifically including the following preparation steps:

[0006] Step 1: Pretreatment of nano-silver powder: Dissolve malonic acid, adipic acid, sebacic acid and oleic acid in ethanol to prepare an organic acid ethanol solution with a concentration of 0.50-0.70 mol / L. Then, pour 10-15 g of nano-silver powder into 180-200 mL of organic acid ethanol solution, sonicate for 1.5-2 h, let stand for 4-6 h, filter, wash with ethanol 2-3 times, and finally dry in a vacuum oven at room temperature for 42-48 h.

[0007] Step 2: Add silver-copper powder, polyurethane prepolymer and functionalized graphene to the pretreated nano-silver powder in sequence, mix and grind to obtain a mixture, and then perform degassing treatment on the mixture to obtain conductive silver paste.

[0008] Preferably, the preparation method of the nano-silver powder is as follows:

[0009] S1. Dissolve 5.2-6.5g of silver nitrate in 36-40mL of deionized water, and heat the solution in a water bath to 45-55℃ while stirring.

[0010] S2. Add the solution from S1 dropwise to 0.7-1.8g of reducing agent. After the addition is complete, stir for 25-30 minutes, and then sonicate at 1000-3000r / min for 15-20 minutes.

[0011] S3. Add a 5% (w / w) ammonia solution dropwise to adjust the pH of the mixed solution to 5-7, and then stir for 25-30 minutes.

[0012] S4. Soak in a 1% (w / w) aqueous solution of 1,2,3-benzotriazole for 20-25 minutes and then filter.

[0013] S5. First, wash with deionized water 3-5 times, then wash with anhydrous ethanol and acetone 1-2 times respectively, and finally dry and grind in a vacuum drying oven at 50-60℃ to obtain nano silver powder.

[0014] Preferably, in step two, the reducing agent is prepared by dissolving 2.4-2.8g of sodium hypophosphite, 0.8-1.2g of sodium hexametaphosphate, 6.3-6.5g of polyvinylpyrrolidone, and 2.5-4mL of 1mol / L dilute sulfuric acid in 235-250mL of deionized water and stirring until homogeneous to obtain the reducing agent.

[0015] Preferably, the method for preparing the functionalized graphene is as follows:

[0016] (1) Mix 1.5-3g of ethylenediamine with 2-6g of graphene dispersion and sonicate for 20-30min.

[0017] (2) Add 20-35 mL of methanol, then slowly add 0.8-1.5 g of methyl acrylate, and stir the reaction under nitrogen atmosphere for 22-24 h.

[0018] (3) After the reaction is complete, pour it into 20-35 mL of methanol. After it is completely dissolved, slowly add 0.8-1.5 g of ethylenediamine and stir the reaction under nitrogen atmosphere for 22-24 h to obtain functionalized graphene.

[0019] Preferably, the graphene dispersion is prepared by mixing 15-25g of graphite with 150-165mL of acetonitrile, then adding 2.5-4g of 1-cyanoethyl-2-ethyl-4-methylimidazole, mixing well, and then ultrasonically dispersing for 2.5-3h. The dispersion is then taken out and allowed to stand for 20-24h. The supernatant is then taken out and centrifuged at 3500-4000r / min for 20-30min to obtain the graphene dispersion.

[0020] Preferably, the method for synthesizing the polyurethane prepolymer is as follows:

[0021] I. Dissolve 16-25g of diisocyanate in 23-34mL of toluene;

[0022] II. Under a nitrogen atmosphere, dissolve 5.5-8g of polyester diol in 45-50mL of toluene, add 1.2-2.5g of dibutyltin dilaurate, and heat the oil bath to 40℃ while stirring to react.

[0023] III. Dissolve 4.3-4.8g of methyl ethyl ketone oxime in 10mL of toluene, then pour it into the mixture from II. Heat the mixture to 50-60℃ and react for 1.5-2h. Finally, distill under reduced pressure at 65-70℃.

[0024] Preferably, the diisocyanate is selected from toluene diisocyanate, isophorone diisocyanate, and 1,4-toluene diisocyanate; the polyester diol is selected from polyethylene glycol, polypropylene glycol, polytetrahydrofuran glycol, and polycarbonate diol.

[0025] Beneficial effects

[0026] This invention provides a conductive silver paste for soldering electronic components and its preparation method. Compared with the prior art, it has the following advantages:

[0027] (1) The conductive silver paste for soldering electronic components and its preparation method pre-treat nano-silver powder with organic acid, so that the carboxyl groups in the organic acid interact with the surface of the nano-silver powder to form a coating layer, preventing the silver powder from agglomerating, making it uniformly dispersed in the paste, improving the stability of the paste, reducing resistance, and the nano-silver powders after treatment are in closer contact with each other, forming a good conductive network, thereby improving the conductivity of the conductive paste; in addition, nano-silver powder is easily oxidized in the air. The organic acid forms a protective film on the surface of the silver powder, blocking oxygen and moisture, reducing the oxidation rate of the silver powder, improving the oxidation resistance of the paste, and extending its service life; the organic acid can also improve the compatibility and affinity between nano-silver powder and the substrate material, so that the silver powder can better adhere to the substrate surface, enhance the bonding force between the conductive paste and the substrate, and prevent the silver powder from falling off or the conductive layer from peeling off due to external force during use.

[0028] (2) The conductive silver paste for soldering electronic components and its preparation method, through the addition of functionalized graphene, have the following effects: First, it works synergistically with silver powder to form a more complete conductive network, improve the conductivity of the conductive silver paste, make current transmission smoother, and reduce resistance; Second, it can be adsorbed on the surface of silver powder, acting as a dispersant, further preventing the silver powder from agglomerating, improving the stability and consistency of the paste, and ensuring the stability of conductivity; Third, it enhances the bonding force between the conductive silver paste and the substrate material, improves the adhesion and mechanical strength of the coating, and prevents the silver powder from falling off or the conductive layer from peeling off during use; Fourth, it can form a protective film on the surface of silver powder, blocking the contact between the silver powder and corrosive substances such as moisture and oxygen in the external environment, reducing the rate of oxidation or corrosion of the silver powder, and improving the corrosion resistance and service life of the conductive silver paste.

[0029] (3) The conductive silver paste for soldering electronic components and its preparation method, by adding polyurethane prepolymer, can effectively improve the bonding force between silver powder and substrate, so that the conductive silver paste can firmly adhere to the surface of various materials after curing, preventing the silver paste from falling off due to external force during use, and ensuring the stability of the conductive path; it can also make the conductive silver paste have a certain elasticity and flexibility after curing, so as to adapt to substrates of different shapes and curved surfaces, reducing the cracking or failure of conductive silver paste due to substrate deformation; at the same time, it can undergo cross-linking reaction with other active groups to form a stable three-dimensional network structure, improving the heat resistance, water resistance and chemical corrosion resistance of the conductive silver paste.

[0030] (4) The conductive silver paste for soldering electronic components and its preparation method form a protective film on the surface of silver powder by 1,2,3-benzotriazole, which prevents the silver powder from being oxidized and enhances the stability of the silver powder, thereby maintaining the long-term stability of the conductive performance of the conductive silver paste; and during the reaction process, substances such as sodium hypophosphite, sodium hexametaphosphate, and polyvinylpyrrolidone can improve the dispersibility of silver powder, form a more uniform conductive network, and at the same time improve the adhesion between the silver powder and the substrate material. Attached Figure Description

[0031] Figure 1 A comparison chart of water contact angle tests provided by this invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1

[0034] A method for preparing conductive silver paste for soldering electronic components, specifically including the following preparation steps:

[0035] Step 1: Preparation of nano-silver powder: Dissolve 5.2g of silver nitrate in 36mL of deionized water and heat to 45℃ in a water bath under stirring. Add the solution dropwise to 0.7g of reducing agent. After the addition is complete, stir for 25min, then sonicate at 1000r / min for 15min. Add 5% ammonia solution dropwise to adjust the pH of the mixed solution to 5, then stir for 25min. Soak in 1% 1,2,3-benzotriazole aqueous solution for 20min and then filter. Wash three times with deionized water, then wash once each with anhydrous ethanol and acetone. Finally, dry and grind in a vacuum drying oven at 50℃ to obtain nano-silver powder.

[0036] Step 2: Pretreatment of nano-silver powder: Dissolve malonic acid, adipic acid, sebacic acid and oleic acid in ethanol to prepare an organic acid ethanol solution with a concentration of 0.50 mol / L. Then, pour 10 g of nano-silver powder into 180 mL of organic acid ethanol solution, sonicate for 1.5 h, let stand for 4 h, filter, wash twice with ethanol, and finally dry in a vacuum oven at room temperature for 42 h.

[0037] Step 3: Preparation of polyurethane prepolymer: Dissolve 16g of toluene diisocyanate in 23mL of toluene; under nitrogen atmosphere, dissolve 5.5g of polyethylene glycol in 45mL of toluene, add 1.2g of dibutyltin dilaurate, heat in an oil bath to 40℃ and stir to obtain solution A; dissolve 4.3g of methyl ethyl ketone oxime in 10mL of toluene, then pour into solution A, heat to 50℃ and react for 1.5h, then distill under reduced pressure at 65℃.

[0038] Step 4: Preparation of Functionalized Graphene

[0039] (1) Mix 15g of graphite with 150mL of acetonitrile, then add 2.5g of 1-cyanoethyl-2-ethyl-4-methylimidazole, mix well and then ultrasonically disperse for 2.5h. Then take out the dispersion and let it stand for 20h. Take out the upper layer and centrifuge at 3500r / min for 20min to obtain the graphene dispersion.

[0040] (2) Take 2g of graphene dispersion and mix it with 1.5g of ethylenediamine, and sonicate for 20min; add 20mL of methanol, then slowly add 0.8g of methyl acrylate, and stir under nitrogen atmosphere for 22h; after the reaction is completed, pour it into 20mL of methanol, and after it is completely dissolved, slowly add 0.8g of ethylenediamine, and stir under nitrogen atmosphere for 22h to obtain functionalized graphene.

[0041] Step 5: Take 60g of pretreated nano-silver powder, add 8g of silver-copper powder, 2g of polyurethane prepolymer and 0.8g of functionalized graphene to it, mix and grind to obtain a mixture, and degas the mixture to obtain conductive silver paste.

[0042] Example 2

[0043] A method for preparing conductive silver paste for soldering electronic components, specifically including the following preparation steps:

[0044] Step 1: Preparation of nano-silver powder: Dissolve 6.1g of silver nitrate in 38mL of deionized water and heat to 50℃ in a water bath under stirring. Add the solution dropwise to 1.2g of reducing agent. After the addition is complete, stir for 27min and then sonicate at 2000r / min for 17min. Add 5% ammonia solution to adjust the pH of the mixed solution to 6 and stir for 28min. Soak in 1% 1,2,3-benzotriazole aqueous solution for 23min and then filter. Wash with deionized water 4 times, then wash with anhydrous ethanol and acetone 2 times respectively. Finally, dry and grind in a vacuum drying oven at 55℃ to obtain nano-silver powder.

[0045] Step 2: Pretreatment of nano-silver powder: Dissolve malonic acid, adipic acid, sebacic acid and oleic acid in ethanol to prepare an organic acid ethanol solution with a concentration of 0.60 mol / L. Then, pour 12g of nano-silver powder into 190mL of organic acid ethanol solution, sonicate for 1.6h, let stand for 5h, filter, wash with ethanol 3 times, and finally dry in a vacuum oven at room temperature for 45h.

[0046] Step 3: Preparation of polyurethane prepolymer: Dissolve 21g of isophorone diisocyanate in 28mL of toluene; under nitrogen atmosphere, dissolve 6.5g of polypropylene glycol in 48mL of toluene, add 1.9g of dibutyltin dilaurate, heat in an oil bath to 40℃ and stir to obtain solution A; dissolve 4.5g of methyl ethyl ketone oxime in 10mL of toluene, then pour into solution A, heat to 55℃ and react for 1.8h, then distill under reduced pressure at 68℃.

[0047] Step 4: Preparation of Functionalized Graphene

[0048] (1) Mix 20g of graphite with 160mL of acetonitrile, then add 3.2g of 1-cyanoethyl-2-ethyl-4-methylimidazole, mix well and then sonicate for 2.8h. Then take out the dispersion and let it stand for 22h. Take out the upper layer and centrifuge at 3800r / min for 25min to obtain the graphene dispersion.

[0049] (2) Take 4g of graphene dispersion and mix it with 2.2g of ethylenediamine, and sonicate for 25min; add 25mL of methanol, then slowly add 1.2g of methyl acrylate, and stir under nitrogen atmosphere for 23h; after the reaction is completed, pour it into 28mL of methanol, and after it is completely dissolved, slowly add 1.1g of ethylenediamine, and stir under nitrogen atmosphere for 23h to obtain functionalized graphene.

[0050] Step 5: Take 75g of pretreated nano-silver powder, add 9g of silver-copper powder, 3.5g of polyurethane prepolymer and 1.4g of functionalized graphene to it, mix and grind to obtain a mixture, and degas the mixture to obtain conductive silver paste.

[0051] Example 3

[0052] A method for preparing conductive silver paste for soldering electronic components, specifically including the following preparation steps:

[0053] Step 1: Preparation of nano-silver powder: Dissolve 6.5g of silver nitrate in 40mL of deionized water and heat to 55℃ in a water bath under stirring. Add the solution dropwise to 1.8g of reducing agent. After the addition is complete, stir for 30min and then sonicate at 3000r / min for 20min. Add 5% ammonia solution to adjust the pH of the mixed solution to 7 and stir for 30min. Soak in 1% 1,2,3-benzotriazole aqueous solution for 25min and then filter. Wash 5 times with deionized water, then wash twice with anhydrous ethanol and acetone respectively. Finally, dry and grind in a vacuum drying oven at 60℃ to obtain nano-silver powder.

[0054] Step 2: Pretreatment of nano-silver powder: Dissolve malonic acid, adipic acid, sebacic acid and oleic acid in ethanol to prepare an organic acid ethanol solution with a concentration of 0.70 mol / L. Then, pour 15g of nano-silver powder into 200mL of organic acid ethanol solution, sonicate for 2h, let stand for 6h, filter, wash with ethanol 3 times, and finally dry in a vacuum oven at room temperature for 48h.

[0055] Step 3: Preparation of polyurethane prepolymer: Dissolve 25g of 1,4-toluene diisocyanate in 34mL of toluene; under nitrogen atmosphere protection, dissolve 8g of polytetrahydrofuran glycol in 50mL of toluene, add 2.5g of dibutyltin dilaurate, heat the mixture in an oil bath to 40℃ and stir to obtain solution A; dissolve 4.8g of methyl ethyl ketone oxime in 10mL of toluene, then pour it into solution A, heat to 60℃, react for 2h, and then distill under reduced pressure at 70℃.

[0056] Step 4: Preparation of Functionalized Graphene

[0057] (1) Mix 25g of graphite with 165mL of acetonitrile, then add 4g of 1-cyanoethyl-2-ethyl-4-methylimidazole, mix well and then ultrasonically disperse for 3h. Then take out the dispersion and let it stand for 24h. Take out the upper layer and centrifuge at 4000r / min for 30min to obtain the graphene dispersion.

[0058] (2) Take 6g of graphene dispersion and mix it with 3g of ethylenediamine, and sonicate for 30min; add 35mL of methanol, then slowly add 1.5g of methyl acrylate, and stir the reaction under nitrogen atmosphere for 24h; after the reaction is completed, pour it into 35mL of methanol, and after it is completely dissolved, slowly add 1.5g of ethylenediamine, and stir the reaction under nitrogen atmosphere for 24h to obtain functionalized graphene.

[0059] Step 5: Take 85g of pretreated nano-silver powder, add 10g of silver-copper powder, 5g of polyurethane prepolymer and 2g of functionalized graphene to it in sequence, mix and grind to obtain a mixture, and degas the mixture to obtain conductive silver paste.

[0060] Comparative Example 1

[0061] The difference from Example 1 is that the nano silver powder in Example 1 is not pretreated.

[0062] Comparative Example 2

[0063] The difference from Example 1 is that the functionalized graphene in Example 1 is replaced with graphene.

[0064] Comparative Example 3

[0065] Compared with Example 1, the difference lies in the method of synthesizing the polyurethane prepolymer in Example 1: 5.5g of polyethylene glycol is added dropwise to 16g of toluene diisocyanate at a reaction temperature of 40°C. After the addition is completed, the reaction continues for 1.5h. Then the temperature is raised to 60°C, and 1.2g of hydroxyethyl methacrylate containing dibutyltin dilaurate is added, wherein the mass of hydroxyethyl methacrylate is 1.2g.

[0066] Comparative Example 4

[0067] Compared with Example 1, the difference is that the nano silver powder in Example 1 is replaced with silver powder, and no pretreatment is performed.

[0068] Bending resistance test: Bend the printed conductor symmetrically outward by 180°, and press a weight onto the silver paste with a pressure of approximately 5.5 kPa for 1 minute; then fold the printed conductor in the opposite direction by 180°, press the same weight onto the silver paste for 1 minute, and perform a conductivity test on the silver paste. The above steps are considered as one bending test. Repeat the above operation until the conductor breaks (number of tests < 10).

[0069] Resistivity and conductivity testing: First, the prepared silver paste was coated onto a glass slide to form a conductive line with a length of 25 mm, a width of 10 mm, and a thickness of approximately 50 μm. The dimensions of the line were controlled by using polyimide tape fixed to the glass substrate. Then, the coated silver paste was vacuum cured at 120°C for 2 hours. Finally, the resistivity and conductivity were tested using an RTS-9 dual-electrical-test four-probe instrument. The results are shown in Table 1.

[0070] Adhesion test: The test was conducted in accordance with GB9286-98, where 5B is the best grade for the 100-grid test and 0B is the worst grade for the 100-grid test; the results are shown in Table 1.

[0071] Pencil hardness test: The test was conducted according to GB / T6739-2006; the results are shown in Table 1.

[0072] Table 1

[0073]

[0074] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0075] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0076] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing conductive silver paste for soldering electronic components, characterized in that, Specifically, the preparation steps are as follows: Step 1: Pretreatment of nano-silver powder: Dissolve malonic acid, adipic acid, sebacic acid and oleic acid in ethanol to prepare an organic acid ethanol solution with a concentration of 0.50-0.70 mol / L. Then, pour 10-15 g of nano-silver powder into 180-200 mL of organic acid ethanol solution, sonicate for 1.5-2 h, let stand for 4-6 h, filter, wash with ethanol 2-3 times, and finally dry in a vacuum oven at room temperature for 42-48 h. Step 2: Add silver-copper powder, polyurethane prepolymer and functionalized graphene to the pretreated nano-silver powder in sequence, mix and grind to obtain a mixture, and degas the mixture to obtain conductive silver paste. The raw materials include the following parts by weight: 60-85 parts of nano silver powder, 2-5 parts of polyurethane prepolymer, 0.8-2 parts of functionalized graphene, and 8-10 parts of silver-copper powder. The preparation method of the nano-silver powder is as follows: S1. Dissolve 5.2-6.5g of silver nitrate in 36-40mL of deionized water, and heat the solution in a water bath to 45-55℃ while stirring. S2. Add the solution from S1 dropwise to 0.7-1.8g of reducing agent. After the addition is complete, stir for 25-30 minutes and sonicate for 15-20 minutes. S3. Add a 5% (w / w) ammonia solution dropwise to adjust the pH of the mixed solution to 5-7, and then stir for 25-30 minutes. S4. Soak in a 1% (w / w) aqueous solution of 1,2,3-benzotriazole for 20-25 minutes and then filter. S5. First wash with deionized water 3-5 times, then wash with anhydrous ethanol and acetone 1-2 times respectively, and finally dry and grind in a vacuum drying oven at 50-60℃ to obtain nano silver powder. The preparation method of the functionalized graphene is as follows: (1) Mix 1.5-3g of ethylenediamine with 2-6g of graphene dispersion and sonicate for 20-30min; (2) Add 20-35 mL of methanol, then slowly add 0.8-1.5 g of methyl acrylate, and stir the reaction under nitrogen atmosphere for 22-24 h to obtain the reaction product; (3) After the reaction is complete, the reaction product is poured into 20-35 mL of methanol. After it is completely dissolved, 0.8-1.5 g of ethylenediamine is slowly added dropwise, and the reaction is stirred for 22-24 h under nitrogen atmosphere to obtain functionalized graphene. The graphene dispersion is prepared by mixing 15-25g of graphite with 150-165mL of acetonitrile, then adding 2.5-4g of 1-cyanoethyl-2-ethyl-4-methylimidazole, mixing well, and then ultrasonically dispersing for 2.5-3h. The dispersion is then taken out and allowed to stand for 20-24h. The supernatant is then taken out and centrifuged at 3500-4000r / min for 20-30min to obtain the graphene dispersion. The method for synthesizing the polyurethane prepolymer is as follows: I. Dissolve 16-25g of diisocyanate in 23-34mL of toluene; II. Under a nitrogen atmosphere, dissolve 5.5-8g of polyester diol in 45-50mL of toluene, add 1.2-2.5g of dibutyltin dilaurate, and heat the oil bath to 40℃ while stirring to react. III. Dissolve 4.3-4.8g of methyl ethyl ketone oxime in 10mL of toluene, then pour it into the mixture from II. Heat the mixture to 50-60℃ and react for 1.5-2h. Finally, distill under reduced pressure at 65-70℃.

2. The method for preparing conductive silver paste for soldering electronic components according to claim 1, characterized in that: In step two, the reducing agent is prepared by dissolving 2.4-2.8g of sodium hypophosphite, 0.8-1.2g of sodium hexametaphosphate, 6.3-6.5g of polyvinylpyrrolidone, and 2.5-4mL of 1mol / L dilute sulfuric acid in 235-250mL of deionized water and stirring until homogeneous to obtain the reducing agent.

3. The method for preparing conductive silver paste for soldering electronic components according to claim 1, characterized in that: The diisocyanate is selected from toluene diisocyanate, isophorone diisocyanate, and 1,4-toluene diisocyanate; the polyester diol is selected from polyethylene glycol, polypropylene glycol, polytetrahydrofuran glycol, and polycarbonate diol.

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