A high-precision nano solder paste and preparation method thereof

Abstract

The present application relates to the technical field of solder paste. The present application discloses a high-precision nano solder paste and a preparation method thereof. The high-precision nano solder paste comprises solder powder, flux, glucomannan and polyethylene glycol modified aliphatic epoxy resin; the raw material composition of the flux comprises: an active agent, a surfactant, a thixotropic agent, an antioxidant, a corrosion inhibitor, a film former and a solvent. The preparation method comprises the following steps: stirring and mixing the active agent and the solvent to prepare a premixed liquid; adding a surfactant, a thixotropic agent, an antioxidant, a film former and a corrosion inhibitor to the premixed liquid in sequence, stirring and mixing to prepare a flux; mixing and stirring the solder powder, flux, glucomannan and polyethylene glycol modified aliphatic epoxy resin, grinding and preparing a high-precision nano solder paste. The high-precision nano solder paste prepared in the present application has good storage stability, long service life, high expansion rate and good wetting performance.

Description

Technical Field

[0001] The present application relates to the technical field of solder paste, and in particular to a high-precision nano solder paste and a preparation method thereof. Background Art

[0002] With the rapid development of information technology, electronic products are becoming increasingly powerful and compact. This trend is also driving the development of electronic components towards higher density and higher precision. At the same time, traditional solder paste is no longer able to meet the demands of modern electronic assembly, especially in the field of precision electronic packaging.

[0003] Traditional solder pastes are primarily suitable for soldering electronic components with larger pad spacing. These pastes typically consist of micron-grade solder alloy powder and flux, allowing for looser pad spacing. However, with the miniaturization of electronic products, the density of component packing on PCBs is increasing, and the pad spacing is shrinking, requiring solder pastes with higher precision and reliability.

[0004] In this context, high-precision nano-solder paste has emerged. It utilizes nano-scale solder alloy powder, which is significantly smaller than traditional micron-scale solder alloy powder. The emergence of high-precision nano-solder paste addresses challenges encountered with traditional solder paste in precision electronic assembly, such as insufficient wetting and low solder joint reliability. It meets the demands of high-density packaging and is suitable for applications such as high-performance computing chips, fine-pitch components, medical electronic equipment, and aerospace electronics.

[0005] However, existing high-precision nano-solder pastes can degrade during storage, affecting their lifespan. There is also room for further improvement in the expansion rate; insufficient expansion limits the solder paste's wettability and filling ability, impacting soldering results.

[0006] Therefore, there is an urgent need to develop a high-precision nano solder paste with good storage stability, long service life, high expansion rate and good wetting performance. Summary of the Invention

[0007] In order to solve at least one of the above technical problems, a high-precision nano-solder paste with good storage stability, long service life, high expansion rate and good wetting performance is developed. The present application provides a high-precision nano-solder paste and a preparation method thereof.

[0008] On the one hand, the present application provides a high-precision nano solder paste, comprising solder powder, flux, glucomannan and polyethylene glycol-modified aliphatic epoxy resin, wherein the weight ratio of the solder powder, flux, glucomannan and polyethylene glycol-modified aliphatic epoxy resin is 85-95:10-15:1-3:1-3;

[0009] The soldering flux comprises, by mass percentage, 6.3% to 10% of active agent, 0.25% to 1.5% of surfactant, 4% to 10% of thixotropic agent, 1% to 5% of antioxidant, 1% to 3% of corrosion inhibitor, 1% to 5% of film former, and the balance being solvent.

[0010] By adopting the above technical solution, this application uses specific raw materials and proportions to produce a high-precision nano-solder paste with good storage stability, long service life, high expansion rate, and good wettability. This application incorporates glucomannan, which can improve the stability of the high-precision nano-solder paste and reduce stratification. This application also incorporates a polyethylene glycol-modified aliphatic epoxy resin, which can increase the expansion rate of the solder paste, improve wettability, prevent solder powder agglomeration, improve the storage stability of the solder paste, and extend its service life.

[0011] Optionally, the polyethylene glycol-modified aliphatic epoxy resin is prepared by comprising polyethylene glycol and an aliphatic epoxy resin, and the weight ratio of the polyethylene glycol to the aliphatic epoxy resin is 1:3-5.

[0012] By adopting the above technical solution, the specific weight ratio of polyethylene glycol and aliphatic epoxy resin in the present application can achieve optimal performance.

[0013] Optionally, the molecular weight of the aliphatic epoxy resin is 600 to 1000, and the epoxy equivalent of the aliphatic epoxy resin is 100 to 300 g / Eq.

[0014] By adopting the above technical solution, the molecular weight and epoxy equivalent of the aliphatic epoxy resin of the present application can balance the performance of the polyethylene glycol-modified aliphatic epoxy resin, thereby improving the overall performance of the solder paste.

[0015] Optionally, the active agent is selected from at least one of maleic acid, p-toluenesulfonic acid and sulfosalicylic acid.

[0016] By adopting the above technical solution, the active agent of the present application can improve the activity of solder paste, promote the chemical reaction between solder powder and pad, thereby improving the wetting performance, and can also remove oxides on the surface of the pad to ensure good electrical connection.

[0017] Optionally, the surfactant is selected from at least one of dibromo-butene-diol, cyclohexylamine hydrobromide and 3-bromo-1-propanol.

[0018] By adopting the above technical solution, the surfactant of the present application can reduce the interfacial tension between the solder powder and the pad, thereby improving the wetting performance of the solder paste, and also helping the solder paste to spread better and increase the expansion rate.

[0019] Optionally, the thixotropic agent is selected from at least one of hydroxyethyl cellulose, hydroxypropyl methyl cellulose and hydrogenated castor oil.

[0020] By adopting the above technical solution, the thixotropic agent of the present application can improve the thixotropy of the solder paste, making it easier to control and preventing excessive flow.

[0021] Optionally, the antioxidant is selected from at least one of N,N'-di-sec-butyl-p-phenylenediamine, mercaptobenzothiazole and triphenyl phosphite.

[0022] By adopting the above technical solution, the antioxidant of the present application can prevent the components in the solder paste from oxidizing, thereby improving the storage stability and service life of the solder paste.

[0023] Optionally, the corrosion inhibitor is selected from at least one of benzotriazole, 2-methylbenzimidazole and triethanolamine; and the film-forming agent is selected from at least one of polyvinyl alcohol, polyvinyl pyrrolidone and methyl hydrogenated rosin.

[0024] By adopting the above technical solution, the corrosion inhibitor of the present application can protect the solder joints from corrosion and improve the long-term reliability of the solder joints. The film-forming agent of the present application can form a protective film around the solder joints to protect the solder joints from oxidation and corrosion.

[0025] Optionally, the solvent is selected from at least one of ethanol, isopropanol and propylene glycol.

[0026] In a second aspect, the present application provides a method for preparing the above-mentioned high-precision nano solder paste, comprising the following steps:

[0027] S1, stirring and mixing the active agent and the solvent to prepare a premixed solution;

[0028] S2, adding the surfactant, thixotropic agent, antioxidant, film-forming agent, and corrosion inhibitor to the premixed solution in sequence, stirring and mixing, to prepare a soldering flux;

[0029] S3. Mixing the solder powder, the flux, the glucomannan and the polyethylene glycol-modified aliphatic epoxy resin, and grinding them to an average particle size of 100 to 250 nm to prepare the high-precision nano solder paste.

[0030] By adopting the above technical solution, the preparation method of the present application is simple to operate and has high preparation efficiency. By gradually adding raw materials, it can ensure that all ingredients are evenly dispersed, improve the performance of the flux, and also improve the expansion rate, wettability and stability of the solder paste, making the solder paste more suitable for the needs of precision electronic packaging.

[0031] In summary, the present invention includes at least one of the following beneficial technical effects:

[0032] 1. This application adopts specific raw materials and proportions to produce high-precision nano solder paste with good storage stability, long service life, high expansion rate and good wetting performance.

[0033] 2. This application incorporates glucomannan, which improves the stability of high-precision nano-solder paste and reduces delamination. This application also incorporates polyethylene glycol-modified aliphatic epoxy resin, which increases the solder paste's expansion rate, improves wettability, prevents solder powder agglomeration, and enhances storage stability.

[0034] 3. The preparation method of the present application is simple to operate and has high preparation efficiency. By gradually adding raw materials, it can ensure that all ingredients are evenly dispersed, thereby improving the expansion rate, wettability and stability of the solder paste. DETAILED DESCRIPTION

[0035] The present application is further described in detail below with reference to the embodiments.

[0036] The present application designs a high-precision nano solder paste, comprising solder powder, flux, glucomannan and polyethylene glycol-modified aliphatic epoxy resin, wherein the weight ratio of the solder powder, flux, glucomannan and polyethylene glycol-modified aliphatic epoxy resin is 85-95:10-15:1-3:1-3;

[0037] The soldering flux comprises, by mass percentage, 6.3% to 10% of active agent, 0.25% to 1.5% of surfactant, 4% to 10% of thixotropic agent, 1% to 5% of antioxidant, 1% to 3% of corrosion inhibitor, 1% to 5% of film former, and the balance being solvent.

[0038] The high-precision nano solder paste of the present application is prepared by the following method, comprising the following steps:

[0039] S1, stirring and mixing the active agent and the solvent to prepare a premixed solution;

[0040] S2, adding the surfactant, thixotropic agent, antioxidant, film-forming agent, and corrosion inhibitor to the premixed solution in sequence, stirring and mixing, to prepare a soldering flux;

[0041] S3. Mixing the solder powder, the flux, the glucomannan and the polyethylene glycol-modified aliphatic epoxy resin, and grinding them to an average particle size of 100 to 250 nm to prepare the high-precision nano solder paste.

[0042] The present application designs a technical solution to address the problems that existing high-precision nano solder paste may experience performance degradation during storage, affecting its service life, and having insufficient expansion rate.

[0043] The raw materials used in this application are as follows:

[0044] Glucomannan: CAS: 11078-31-2.

[0045] Maleic acid: CAS: 110-16-7.

[0046] p-Toluenesulfonic acid: CAS: 104-15-4.

[0047] Dibromo-butene-diol: CAS: 3234-02-4.

[0048] Cyclohexylamine hydrobromide: CAS: 26227-54-3.

[0049] Hydroxyethyl cellulose: CAS: 9004-62-0.

[0050] Hydrogenated castor oil: CAS: 61788-85-0.

[0051] Mercaptobenzothiazole: CAS: 149-30-4.

[0052] Triphenyl phosphite: CAS: 101-02-0.

[0053] Benzotriazole: CAS: 95-14-7.

[0054] Triethanolamine: CAS: 102-71-6.

[0055] Polyvinyl alcohol: CAS: 9002-89-5.

[0056] Methyl hydrogenated abietic acid: CAS: 8050-15-5.

[0057] Isopropyl alcohol: CAS: 67-63-0. Specific embodiments

[0059] Examples 1 to 3

[0060] Example 1

[0061] This embodiment provides a high-precision nano solder paste, comprising solder powder, flux, glucomannan, and polyethylene glycol-modified aliphatic epoxy resin, wherein the weight ratio of the solder powder, flux, glucomannan, and polyethylene glycol-modified aliphatic epoxy resin is 85:10:1:1;

[0062] The flux is composed of raw materials in percentage by mass: 6.3% activator, 0.25% surfactant, 10% thixotropic agent, 1% antioxidant, 1% corrosion inhibitor, 5% film former, and the balance is solvent;

[0063] Among them, the solder powder is SAC 305 alloy powder;

[0064] The polyethylene glycol-modified aliphatic epoxy resin is prepared by mixing polyethylene glycol and an aliphatic epoxy resin in a weight ratio of 1:4. The aliphatic epoxy resin has a molecular weight of 8000 and an epoxy equivalent weight of 200 g / Eq.

[0065] The active agent is p-toluenesulfonic acid; the surfactant is dibromo-butylene-diol; the thixotropic agent is hydroxyethyl cellulose; the antioxidant is mercaptobenzothiazole; the corrosion inhibitor is benzotriazole; the film-forming agent is polyvinyl alcohol; and the solvent is isopropyl alcohol.

[0066] The preparation method comprises the following steps:

[0067] S1, stirring and mixing the active agent and the solvent to prepare a premixed solution;

[0068] S2. Adding a surfactant, a thixotropic agent, an antioxidant, a film-forming agent, and a corrosion inhibitor to the premixed solution in sequence, stirring and mixing, to prepare a soldering flux;

[0069] S3. Solder powder, flux, glucomannan and polyethylene glycol-modified aliphatic epoxy resin are mixed and stirred, and ground to an average particle size of 100 nm to prepare a high-precision nano solder paste.

[0070] Example 2

[0071] This embodiment provides a high-precision nano solder paste, comprising solder powder, flux, glucomannan, and polyethylene glycol-modified aliphatic epoxy resin, wherein the weight ratio of the solder powder, flux, glucomannan, and polyethylene glycol-modified aliphatic epoxy resin is 90:12.5:2:2;

[0072] The flux is composed of raw materials in percentage by mass: activator 8.2%, surfactant 0.9%, thixotropic agent 7%, antioxidant 3%, corrosion inhibitor 2%, film former 3%, and the balance is solvent;

[0073] Among them, the solder powder is SAC 305 alloy powder;

[0074] The polyethylene glycol-modified aliphatic epoxy resin is prepared by mixing polyethylene glycol and an aliphatic epoxy resin in a weight ratio of 1:4. The aliphatic epoxy resin has a molecular weight of 8000 and an epoxy equivalent weight of 200 g / Eq.

[0075] The active agent is p-toluenesulfonic acid; the surfactant is dibromo-butylene-diol; the thixotropic agent is hydroxyethyl cellulose; the antioxidant is mercaptobenzothiazole; the corrosion inhibitor is benzotriazole; the film-forming agent is polyvinyl alcohol; and the solvent is isopropyl alcohol.

[0076] The preparation method comprises the following steps:

[0077] S1, stirring and mixing the active agent and the solvent to prepare a premixed solution;

[0078] S2. Adding a surfactant, a thixotropic agent, an antioxidant, a film-forming agent, and a corrosion inhibitor to the premixed solution in sequence, stirring and mixing, to prepare a soldering flux;

[0079] S3. Solder powder, flux, glucomannan and polyethylene glycol-modified aliphatic epoxy resin are mixed and stirred, and ground to an average particle size of 170 nm to prepare a high-precision nano solder paste.

[0080] Example 3

[0081] This embodiment provides a high-precision nano solder paste, comprising solder powder, flux, glucomannan, and polyethylene glycol-modified aliphatic epoxy resin, wherein the weight ratio of the solder powder, flux, glucomannan, and polyethylene glycol-modified aliphatic epoxy resin is 95:15:3:3;

[0082] The flux is composed of raw materials in percentage by mass: 10% activator, 1.5% surfactant, 4% thixotropic agent, 5% antioxidant, 3% corrosion inhibitor, 1% film former, and the balance is solvent;

[0083] Among them, the solder powder is SAC 305 alloy powder;

[0084] The polyethylene glycol-modified aliphatic epoxy resin is prepared by mixing polyethylene glycol and an aliphatic epoxy resin in a weight ratio of 1:4. The aliphatic epoxy resin has a molecular weight of 8000 and an epoxy equivalent weight of 200 g / Eq.

[0085] The active agent is p-toluenesulfonic acid; the surfactant is dibromo-butylene-diol; the thixotropic agent is hydroxyethyl cellulose; the antioxidant is mercaptobenzothiazole; the corrosion inhibitor is benzotriazole; the film-forming agent is polyvinyl alcohol; and the solvent is isopropyl alcohol.

[0086] The preparation method comprises the following steps:

[0087] S1, stirring and mixing the active agent and the solvent to prepare a premixed solution;

[0088] S2. Adding a surfactant, a thixotropic agent, an antioxidant, a film-forming agent, and a corrosion inhibitor to the premixed solution in sequence, stirring and mixing, to prepare a soldering flux;

[0089] S3. Solder powder, flux, glucomannan and polyethylene glycol-modified aliphatic epoxy resin are mixed and stirred, and ground to an average particle size of 250 nm to prepare a high-precision nano solder paste.

[0090] Comparative Examples 1 to 4

[0091] Comparative Example 1

[0092] The difference between Comparative Example 1 and Example 2 is that glucomannan and polyethylene glycol-modified aliphatic epoxy resin are not added in Comparative Example 1.

[0093] Comparative Example 2

[0094] The difference between Comparative Example 2 and Example 2 is that no glucomannan is added in Comparative Example 2.

[0095] Comparative Example 3

[0096] The difference between Comparative Example 3 and Example 2 is that no polyethylene glycol-modified aliphatic epoxy resin is added in Comparative Example 3.

[0097] Comparative Example 4

[0098] The difference between Comparative Example 4 and Example 2 is that the active agent and the solvent are not pre-mixed in Comparative Example 4. The specific preparation method is as follows: S1, the active agent, the surfactant, the thixotropic agent, the antioxidant, the film-forming agent, the corrosion inhibitor and the solvent are stirred and mixed to prepare a soldering flux;

[0099] S2. Solder powder, flux, glucomannan and polyethylene glycol-modified aliphatic epoxy resin are mixed and stirred, and ground to an average particle size of 170 nm to prepare a high-precision nano solder paste.

[0100] Experimental testing

[0101] Test items and methods

[0102] Storage stability: The prepared high-precision nano solder paste was sealed and stored at 10°C for 6 months to observe whether there was any grease separation or delamination.

[0103] Expansion rate: Test the expansion rate of solder paste according to JIS Z3284;

[0104] Wetting performance: The wetting performance of solder paste is evaluated according to the solder paste wettability evaluation standard in SJ / T 11186-2019 "General Specification for Solder Paste".

[0105] The high-precision nano solder pastes prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were tested for storage stability, expansion rate, and wetting performance. The test results are shown in Table 1.

[0106] Table 1

[0107] Storage stability Expansion rate / % Wetting properties Example 1 No stratification 86.6 Level 1 Example 2 No stratification 87.5 Level 1 Example 3 No stratification 87.0 Level 1 Comparative Example 1 Layered 78.7 Level 2 Comparative Example 2 Layered 79.9 Level 1 Comparative Example 3 Layered 79.1 Level 2 Comparative Example 4 Layered 80.3 Level 1

[0108] From the test results in Table 1, it can be seen that the high-precision nano solder pastes prepared in Examples 1 to 3 have good storage stability, no delamination, long service life, high expansion rate, and good wetting performance.

[0109] Comparative Example 1 did not add glucomannan and polyethylene glycol-modified aliphatic epoxy resin, Comparative Example 2 did not add glucomannan, and Comparative Example 3 did not add polyethylene glycol-modified aliphatic epoxy resin. The storage stability of the high-precision nano solder pastes prepared in Comparative Examples 1 to 3 decreased, delamination occurred, and the expansion rate and wetting performance also decreased significantly.

[0110] In Comparative Example 4, the raw materials of the flux were mixed and stirred together without adding them sequentially, resulting in poor storage stability and reduced expansion rate of the obtained high-precision nano solder paste.

[0111] Examples 4 to 13

[0112] Example 4

[0113] The difference between Example 4 and Example 2 is that in Example 4, the weight ratio of the polyethylene glycol-modified aliphatic epoxy resin to the aliphatic epoxy resin is 1:3.

[0114] Example 5

[0115] The difference between Example 5 and Example 2 is that in Example 5, the weight ratio of the polyethylene glycol-modified aliphatic epoxy resin to the aliphatic epoxy resin is 1:5.

[0116] Example 6

[0117] The difference between Example 6 and Example 2 is that in Example 6, the molecular weight of the aliphatic epoxy resin is 600 and the epoxy equivalent is 100 g / Eq.

[0118] Example 7

[0119] The difference between Example 7 and Example 2 is that in Example 7, the molecular weight of the aliphatic epoxy resin is 1000 and the epoxy equivalent is 300 g / Eq.

[0120] Example 8

[0121] The difference between Example 8 and Example 2 is that in Example 8, the active agent is maleic acid.

[0122] Example 9

[0123] The difference between Example 9 and Example 2 is that in Example 9, the surfactant is cyclohexylamine hydrobromide.

[0124] Example 10

[0125] The difference between Example 10 and Example 2 is that in Example 10, the thixotropic agent is hydrogenated castor oil.

[0126] Example 11

[0127] The difference between Example 11 and Example 2 is that in Example 11, the antioxidant is triphenyl phosphite.

[0128] Example 12

[0129] The difference between Example 12 and Example 2 is that in Example 12, the corrosion inhibitor is triethanolamine.

[0130] Example 13

[0131] The difference between Example 13 and Example 2 is that in Example 13, the film-forming agent is methyl hydrogenated rosinate.

[0132] The high-precision nano solder pastes prepared in Examples 4 to 13 were tested for storage stability, expansion rate, and wetting performance. The test results are shown in Table 2.

[0133] Table 2

[0134] Storage stability Expansion rate / % Wetting properties Example 4 No stratification 87.3 Level 1 Example 5 No stratification 87.2 Level 1 Example 6 No stratification 87.4 Level 1 Example 7 No stratification 87.2 Level 1 Example 8 No stratification 87.5 Level 1 Example 9 No stratification 87.3 Level 1 Example 10 No stratification 87.5 Level 1 Example 11 No stratification 87.6 Level 1 Example 12 No stratification 87.3 Level 1 Example 13 No stratification 87.7 Level 1

[0135] From the test results in Table 2, it can be seen that the difference between Example 4 and Example 5 and Example 2 is that the weight ratio of polyethylene glycol to aliphatic epoxy resin in the polyethylene glycol-modified aliphatic epoxy resin is different, and the expansion rate of the obtained high-precision nano solder paste is lower than that of Example 2.

[0136] The difference between Example 6 and Example 7 and Example 2 is that the molecular weight and epoxy equivalent of the aliphatic epoxy resin are different. Among them, the expansion rate of the high-precision nano solder paste prepared in Example 2 is the best.

[0137] The storage stability, expansion rate and wetting performance of the high-precision nano solder pastes prepared in Examples 8 to 13 are similar to those in Example 2.

[0138] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A high-precision nano solder paste, characterized in that: The invention comprises solder powder, flux, glucomannan and polyethylene glycol modified aliphatic epoxy resin, wherein the weight ratio of the solder powder, flux, glucomannan and polyethylene glycol modified aliphatic epoxy resin is 85-95:10-15:1-3:1-3; The soldering flux comprises, by weight percentage, 6.3% to 10% of an activator, 0.25% to 1.5% of a surfactant, 4% to 10% of a thixotropic agent, 1% to 5% of an antioxidant, 1% to 3% of a corrosion inhibitor, 1% to 5% of a film-forming agent, and the balance being a solvent.

2. The high-precision nano solder paste according to claim 1, characterized in that: The polyethylene glycol-modified aliphatic epoxy resin is prepared by comprising polyethylene glycol and aliphatic epoxy resin, wherein the weight ratio of the polyethylene glycol to the aliphatic epoxy resin is 1:3-5.

3. The high-precision nano solder paste according to claim 2, characterized in that: The molecular weight of the aliphatic epoxy resin is 600-1000, and the epoxy equivalent of the aliphatic epoxy resin is 100-300 g / Eq.

4. The high-precision nano solder paste according to claim 1, characterized in that: The active agent is selected from at least one of maleic acid, p-toluenesulfonic acid and sulfosalicylic acid.

5. The high-precision nano solder paste according to claim 1, characterized in that: The surfactant is selected from at least one of dibromo-butene-diol, cyclohexylamine hydrobromide and 3-bromo-1-propanol.

6. The high-precision nano solder paste according to claim 1, characterized in that: The thixotropic agent is selected from at least one of hydroxyethyl cellulose, hydroxypropyl methyl cellulose and hydrogenated castor oil.

7. The high-precision nano solder paste according to claim 1, characterized in that: The antioxidant is selected from at least one of N,N'-di-sec-butyl-p-phenylenediamine, mercaptobenzothiazole and triphenyl phosphite.

8. The high-precision nano solder paste according to claim 1, characterized in that: The corrosion inhibitor is selected from at least one of benzotriazole, 2-methylbenzimidazole and triethanolamine; The film-forming agent is selected from at least one of polyvinyl alcohol, polyvinyl pyrrolidone and methyl hydrogenated rosin.

9. The high-precision nano solder paste according to claim 1, characterized in that: The solvent is selected from at least one of ethanol, isopropanol and propylene glycol.

10. A method for preparing the high-precision nano solder paste according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1, stirring and mixing the active agent and the solvent to prepare a premixed solution; S2, adding the surfactant, thixotropic agent, antioxidant, film-forming agent, and corrosion inhibitor to the premixed solution in sequence, stirring and mixing, to prepare a soldering flux; S3. Mixing the solder powder, the flux, the glucomannan and the polyethylene glycol-modified aliphatic epoxy resin, and grinding them to an average particle size of 100-250 nm to prepare the high-precision nano solder paste.