Water-soluble solder paste and preparation method and application thereof

Abstract

The invention relates to the technical field of electronic welding materials, and discloses water-soluble solder paste and a preparation method and application thereof. The water-soluble solder paste comprises a water-soluble soldering flux and tin powder, wherein the mass ratio of the water-soluble soldering flux to the tin powder is 1: (7-10); the water-soluble soldering flux comprises the following components in parts by weight: 45-55 parts of a film-forming agent; 8-12 parts of an organic acid active agent; 6-8 parts of a thixotropic agent; 0.3 to 3 parts of a surfactant; 1-3 parts of a corrosion inhibitor; 3-5 parts of an antioxidant; 25 to 35 parts of a solvent; the film forming agent is prepared from the following raw materials: polyethylene glycol 400, hydroxypropyl methyl cellulose sodium, a VYBAR 825 polymer, triethylamine, 1, 6-hexanediol, tripropylene glycol and polyoxyethylene glyceryl ether MF-200A. According to the water-soluble solder paste, the specific film-forming agent is added, vacuum stirring and other operations are combined, and the prepared water-soluble solder paste has the advantages of being free of organic solvent cleaning, resistant to moisture absorption, long in storage life and the like.

Description

Technical Field

[0001] The present application relates to the technical field of electronic welding materials, and in particular to a water-soluble solder paste and a preparation method and application thereof. Background Art

[0002] In the electronics manufacturing industry, processes such as surface mount assembly of electronic circuit boards and soldering of IC pins are crucial. This is especially true in specific scenarios, such as sensor soldering within ultrasonic radars and photosensitive sensors, which place stringent requirements on soldering materials and processes. With the continuous advancement of electronic technology, the requirements for soldering quality and efficiency are also increasing. High-quality soldering materials ensure stable connections between electronic components, improving the reliability and performance of electronic products. This not only helps improve the stability of the entire electronic system, but also meets the trend of miniaturization and high performance of modern electronic products.

[0003] In existing technology, natural rosin is used to increase solder paste viscosity and prevent shifting. However, during actual soldering operations, the rosin / flux residue left on electronic circuit boards after soldering. To remove this residue, organic solvents are typically used as cleaning agents to remove the flux and water-insoluble natural rosin. However, cleaning solder residue with organic solvents can be corrosive to circuit boards. To address this, water-soluble solder pastes are now commercially available that can be cleaned with water after soldering, eliminating the corrosive effects of organic solvents on circuit boards.

[0004] However, the water-soluble solder paste in the prior art is prone to moisture absorption when used in the air for a long time, resulting in reduced viscosity, tin frying, and other phenomena. To this end, a reflow oven filled with protective gas is generally used to solve the moisture absorption problem of the water-soluble solder paste. However, the current water-soluble solder paste still has problems such as short storage life, easy delamination, and poor wetting performance. Summary of the Invention

[0005] In order to overcome at least one of the problems existing in the above-mentioned prior art, one of the purposes of this application is to provide a water-soluble solder paste, which has the advantages of not requiring organic solvent cleaning, being resistant to moisture absorption, having a long storage life (can be stored for 6 months), having good wetting properties, not being easy to delaminate, and having high welding strength. It avoids the problems of solder paste delamination and easy moisture absorption, and can meet the requirements of people for solder paste electronic solder materials during actual use. The second purpose of this application is to provide a method for preparing the water-soluble solder paste. The third purpose of this application is to provide an application of the water-soluble solder paste.

[0006] To this end, this application adopts the following technical solutions: The first aspect of the present application provides a water-soluble solder paste, comprising a water-soluble flux and tin powder, wherein the mass ratio of the water-soluble flux to the tin powder is 1:(7-10); the water-soluble flux comprises the following components in parts by weight: 45-55 parts of film-forming agent; 8-12 parts of organic acid active agent; 6-8 parts of thixotropic agent; The raw materials for preparing the film-forming agent include polyethylene glycol 400, sodium hydroxypropyl methylcellulose, VYBAR 825 polymer, triethylamine, 1,6-hexanediol, tripropylene glycol and polyoxyethylene glycerol ether MF-200A.

[0007] Preferably, the film-forming agent is a mixture of polyethylene glycol 400, sodium hydroxypropyl methylcellulose, VYBAR 825 polymer, triethylamine, 1,6-hexanediol, tripropylene glycol and polyoxyethylene glycerol ether MF-200A in a mass ratio of (4-6): (2-4.5): (1.5-3.5): (0.8-1.2): (0.3-0.7): (0.1-0.4): (0.5-0.7).

[0008] Among the raw materials used in the preparation of the film-forming agent, polyethylene glycol 400 is a water-soluble polymer with excellent solubility and stability. It forms a protective film during the soldering process, preventing tin powder oxidation and providing protection. Sodium hydroxypropyl methylcellulose is a cellulose ether compound with thickening and film-forming properties, helping to improve the viscosity and stability of the water-soluble flux. VYBAR 825 polymer has excellent thermal and chemical stability, improving the overall performance of the water-soluble flux. Triethylamine is an organic base that regulates the pH of the water-soluble flux and maintains its stability. 1,6-Hexanediol has certain solubility and volatility, which helps ensure uniform mixing of the flux and its volatilization during soldering. Tripropylene glycol has good solubility and a moderate boiling point, making it suitable as a solvent and auxiliary agent. Polyoxyethylene glycerol ether MF-200A is a nonionic surfactant that reduces surface tension, allowing for better spreading of the flux. These ingredients are mixed in a certain proportion to form a film-forming agent. During the soldering process, the film-forming agent will form a uniform thin film on the soldering site. This thin film can isolate the air and prevent the tin powder from oxidizing. It also helps to evenly distribute the flux and smoothly carry out soldering. At the same time, it also avoids the situation where the existing water-soluble solder paste is prone to moisture absorption, resulting in reduced viscosity and tin explosion. It can also prevent the tin powder in the solder paste from sinking or separating, thereby increasing the storage life of the water-soluble solder paste.

[0009] Preferably, the organic acid active agent is selected from at least one of dodecanedioic acid, phenylsuccinic acid, glycolic acid, suberic acid, succinic acid, and hexadecanoic acid. Further preferably, the organic acid active agent is selected from at least one of dodecanedioic acid, phenylsuccinic acid, suberic acid, succinic acid, and hexadecanoic acid. Even more preferably, the organic acid active agent is selected from at least one of dodecanedioic acid, phenylsuccinic acid, and suberic acid.

[0010] At least one of dodecanedioic acid, phenylsuccinic acid, glycolic acid, suberic acid, succinic acid, and hexadecanoic acid is selected as the organic acid activator, which can effectively remove metal surface oxides during welding and improve welding wetting performance.

[0011] Preferably, the thixotropic agent is a bisamide thixotropic agent.

[0012] Preferably, the bisamide thixotropic agent is selected from at least one of ethylene bis(12-hydroxystearamide), phenylene bisstearamide, and hexamethylenediamine bisstearamide. Further preferably, the bisamide thixotropic agent is selected from at least one of ethylene bis(12-hydroxystearamide) and phenylene bisstearamide.

[0013] Bisamide thixotropic agents are key additives for water-soluble solder pastes. Bisamide thixotropic agents contain polar groups (such as hydroxyl groups and amide bonds) and long-chain alkyl groups (hydrophobic ends) in their molecules. In water-soluble systems, they can self-assemble through hydrogen bonding and van der Waals forces to form a three-dimensional network structure. When left standing, this structure can encapsulate solder powder and flux components, maintaining a high viscosity in the solder paste, preventing tin powder sedimentation and solvent stratification, and ensuring the uniformity of the solder paste. However, under the action of external forces such as shear, the network structure of the biamide is destroyed, causing the viscosity of the solder paste to drop rapidly and its fluidity to increase. When the shear force disappears, the network structure can be restored and the viscosity of the solder paste will rise again. Therefore, the use of biamide thixotropic agents can give water-soluble solder pastes excellent thixotropic properties, ensuring the fluidity and stability of the solder paste in different usage scenarios.

[0014] Preferably, the surfactant is selected from at least one of dimethicone, oleyl alcohol polyoxyethylene ether, Surfynol 104 surfactant, and GE-511 surfactant. Further preferably, the surfactant is selected from at least one of dimethicone, oleyl alcohol polyoxyethylene ether, and Surfynol 104 surfactant. Even more preferably, the surfactant is selected from at least one of dimethicone and Surfynol 104 surfactant.

[0015] Preferably, the corrosion inhibitor is at least one selected from mercaptobenzothiazole, ethylenethiourea, and 2-mercaptoethanol. Further preferably, the corrosion inhibitor is at least one selected from mercaptobenzothiazole and 2-mercaptoethanol.

[0016] Preferably, the antioxidant is selected from at least one of 2-ethylimidazole, benzimidazole, methylbenzotriazole, and benzotriazole. Further preferably, the antioxidant is selected from at least one of 2-ethylimidazole, benzimidazole, and methylbenzotriazole. Even more preferably, the antioxidant is selected from at least one of 2-ethylimidazole and benzimidazole.

[0017] Preferably, the solvent is selected from at least one of tetrahydrofurfuryl alcohol, tetraethylene glycol, diethylene glycol dibutyl ether, propylene glycol methyl ether, and dipropylene glycol dimethyl ether. Further preferably, the solvent is selected from at least one of tetrahydrofurfuryl alcohol, tetraethylene glycol, diethylene glycol dibutyl ether, and propylene glycol methyl ether. Even more preferably, the solvent is selected from at least one of tetrahydrofurfuryl alcohol, tetraethylene glycol, and diethylene glycol dibutyl ether.

[0018] The surfactants in this application help reduce the surface tension of the system, improve wettability, and disperse the tin powder to prevent agglomeration. Corrosion inhibitors bind to active sites on the tin powder surface, forming a dense adsorption film that blocks contact between acidic substances and water and the metal, thereby inhibiting corrosion reactions. Antioxidants inhibit the oxidation of tin powder, prevent rusting of the pad substrate, and protect the stability of the flux components, ultimately ensuring the extended shelf life of the water-soluble solder paste and the reliability of soldering.

[0019] Preferably, the particle size of the tin powder is 22 to 35 μm. More preferably, the particle size of the tin powder is 25 to 32 μm.

[0020] By adopting the above technical solution, the water-soluble flux and tin powder are mixed in a specific mass ratio to ensure the basic performance of the solder paste; the film-forming agent, organic acid activator, thixotropic agent, surfactant, corrosion inhibitor, antioxidant and solvent are combined in specific weight percentages, and the film-forming agent is prepared using specific raw materials, so that the solder paste has good wetting properties, long life, and suitable viscosity. It can be cleaned after welding, has a high tin climbing height, a large expansion rate, and high strength. At the same time, it can solve the problems of existing water-soluble solder paste such as moisture absorption, tin explosion, short storage life, and easy delamination.

[0021] The second aspect of the present application provides a method for preparing the water-soluble solder paste according to the first aspect of the present application, comprising the following steps: S1: Weighing raw materials of various components of a water-soluble soldering flux in parts by weight, mixing, heating, stirring, cooling, grinding, and allowing to stand to prepare a water-soluble soldering flux; S2: Weigh the water-soluble flux and tin powder according to parts by weight, mix and stir to obtain the water-soluble solder paste.

[0022] Preferably, in step S1, the heating temperature is 50-70°C, the stirring speed is 1200-1800 r / min, the stirring time is 3-5 hours, and the standing time is 2-3 days. Further preferably, in step S1, the heating temperature is 50-65°C, the stirring speed is 1300-1800 r / min, the stirring time is 3-4.5 hours, and the standing time is 2-2.5 days. Even further preferably, in step S1, the heating temperature is 55-65°C, the stirring speed is 1400-1800 r / min, the stirring time is 3-4 hours, the ground particle fineness is ≤10 μm, and the standing time is 2.5 days.

[0023] Preferably, in step S2, the stirring speed is 20 to 30 r / min, the stirring time is 35 to 50 min, the vacuum degree of the vacuum stirring is -0.09 MPa to -0.1 MPa, the vacuum stirring speed is 20 to 30 r / min, and the vacuum stirring time is 15 to 20 min. Further preferably, in step S2, the stirring speed is 20 to 30 r / min, the stirring time is 35 to 45 min, the vacuum degree of the vacuum stirring is -0.09 MPa to -0.1 MPa, the vacuum stirring speed is 20 to 25 r / min, and the vacuum stirring time is 15 to 18 min. More preferably, in step S2, the stirring speed is 20 to 26 r / min, the stirring time is 40 to 45 min, the vacuum degree of the vacuum stirring is -0.09 MPa to -0.1 MPa, the vacuum stirring speed is 20 to 25 r / min, and the vacuum stirring time is 15 to 18 min.

[0024] In the preparation method of this water-soluble solder paste, step S1 utilizes a combined process of "heating and dispersing - grinding and refining - static foam stabilization" to ensure uniform flux, a tight and stable internal structure, and consistent internal and surface temperatures. This ensures that the resulting water-soluble solder paste exhibits excellent wetting properties, a long lifespan, and an appropriate viscosity. Furthermore, the ground particles are ≤10 μm, which increases the contact area during water washing and improves the effectiveness of washing residual solder paste after soldering.

[0025] Maintaining a vacuum in step S2 prevents air from entering the system, preventing oxidation of the tin powder due to oxygen exposure during mixing. It also promptly removes bubbles introduced by mechanical agitation during mixing. This prevents oxidation of the tin powder and bubbles in the solder paste, ensuring a "cold solder joint"-free solder joint. Low-speed stirring helps the flux evenly and thoroughly coat the tin powder surface, forming a "flux-tin powder" interface layer, while also preventing high-speed stirring from causing surface wear and accelerating oxidation.

[0026] Preferably, the preparation method of the film-forming agent comprises the following steps: The film-forming agent is prepared by mixing polyethylene glycol 400, sodium hydroxypropyl methylcellulose, VYBAR 825 polymer, triethylamine, 1,6-hexanediol, tripropylene glycol and polyoxyethylene glycerol ether MF-200A, and then stirring.

[0027] During stirring, shear forces promote dissolution and intermolecular interactions among the components. For example, the hydroxyl groups of polyethylene glycol 400 form hydrogen bonds with those of sodium hydroxypropyl methylcellulose, forming a composite film that combines flexibility and strength. VYBAR 825 polymer is evenly dispersed in the film-forming agent, enabling it to synergize with the bisamide thixotropic agent in the subsequent solder paste system, enhancing the thixotropy of the water-soluble solder paste. The film-forming agent in this application exhibits stable performance and exhibits no delamination when mixed with other components, ultimately providing the solder paste with excellent post-solder film protection.

[0028] A third aspect of the present application provides an application of a water-soluble solder paste in electronic soldering materials. The water-soluble solder paste is the above-mentioned water-soluble solder paste, or is prepared by the above-mentioned preparation method.

[0029] Compared with the prior art, this application has at least the following beneficial effects: 1) The raw materials of the water-soluble solder paste of the present application are all soluble in water or can be washed away with water after soldering, thus avoiding the problem of circuit board corrosion caused by the use of organic solvents for cleaning.

[0030] 2) This application utilizes a specially formulated film-forming agent to form a uniform film on the solder joint. This film isolates the solder paste from air, preventing oxidation of the tin powder. It also facilitates uniform distribution of the flux and smooths soldering, while also avoiding the viscosity loss and tin frying that can occur with existing water-soluble solder pastes due to moisture absorption. The water-soluble solder paste solder joints of this application were exposed to temperatures of 85°C and humidity of 85% for 72 hours, and the residue on the solder joints showed no discoloration or corrosion, demonstrating excellent moisture absorption resistance.

[0031] 3) The water-soluble solder paste of the present application has a compact internal structure and stable materials through a specific process during the preparation process, and its storage life can reach 6 months, thus solving the problem of short storage life of existing water-soluble solder paste.

[0032] 4) By adding an organic acid activator, the water-soluble solder paste effectively removes metal surface oxides during the welding process and improves the welding wetting performance. The flux of the water-soluble solder paste of the present application has a strong bonding force with the tin powder, is not easy to delaminate, and has good wetting performance. The tin climbing height during welding is ≥0.8mm and the expansion rate is ≥83%, which meets the welding requirements of high-precision electronic components. DETAILED DESCRIPTION

[0033] The contents of this application are further described in detail below through specific examples, comparative examples and tables, but are not limited to all discussions and data.

[0034] The water-soluble solder paste raw materials include a Sn-Ag-Cu alloy with a particle size range of 22 to 35 μm, where the mass fraction of Ag is 3.0% and the mass fraction of Cu is 1.5%. The film-forming agent is prepared according to the formulation and preparation method of this application. In the examples and comparative examples, the mass ratio of flux to tin powder is 11.5:88.5.

[0035] Preparation example of film-forming agent: Preparation Example 1: A preparation method of a film-forming agent comprises the following steps: The film-forming agent was prepared by mixing 4 g of polyethylene glycol 400, 3 g of sodium hydroxypropyl methylcellulose, 1.8 g of VYBAR 825 polymer, 0.9 g of triethylamine, 0.3 g of 1,6-hexanediol, 0.2 g of tripropylene glycol and 0.55 g of polyoxyethylene glycerol ether MF-200A, and then stirring.

[0036] Preparation Example 2: A preparation method of a film-forming agent comprises the following steps: The film-forming agent was prepared by mixing 5 g of polyethylene glycol 400, 2.3 g of sodium hydroxypropyl methylcellulose, 3.1 g of VYBAR 825 polymer, 0.9 g of triethylamine, 0.5 g of 1,6-hexanediol, 0.2 g of tripropylene glycol and 0.6 g of polyoxyethylene glycerol ether MF-200A, and then stirring.

[0037] Preparation Example 3: A preparation method of a film-forming agent comprises the following steps: The film-forming agent was prepared by mixing 5.5 g of polyethylene glycol 400, 3.6 g of sodium hydroxypropyl methylcellulose, 2.8 g of VYBAR 825 polymer, 1.1 g of triethylamine, 0.6 g of 1,6-hexanediol, 0.3 g of tripropylene glycol and 0.6 g of polyoxyethylene glycerol ether MF-200A, and then stirring.

[0038] Preparation Comparative Example 1: A preparation method of a film-forming agent comprises the following steps: The film-forming agent was prepared by mixing 8 g of polyethylene glycol 400, 3 g of sodium hydroxypropyl methylcellulose, 1.8 g of VYBAR 825 polymer, 0.9 g of triethylamine, 0.3 g of 1,6-hexanediol, 0.2 g of tripropylene glycol and 0.55 g of polyoxyethylene glycerol ether MF-200A, and then stirring.

[0039] Preparation Comparative Example 2: A preparation method of a film-forming agent comprises the following steps: The film-forming agent was prepared by mixing 4 g of polyethylene glycol 400, 5 g of sodium hydroxypropyl methylcellulose, 1.8 g of VYBAR 825 polymer, 0.9 g of triethylamine, 0.3 g of 1,6-hexanediol, 0.2 g of tripropylene glycol and 0.55 g of polyoxyethylene glycerol ether MF-200A, and then stirring.

[0040] Preparation Comparative Example 3: A preparation method of a film-forming agent comprises the following steps: The film-forming agent was prepared by mixing 4 g of polyethylene glycol 400, 3 g of sodium hydroxypropyl methylcellulose, 1 g of VYBAR 825 polymer, 0.9 g of triethylamine, 0.3 g of 1,6-hexanediol, 0.2 g of tripropylene glycol and 0.55 g of polyoxyethylene glycerol ether MF-200A, and then stirring.

[0041] Preparation Comparative Example 4: A preparation method of a film-forming agent comprises the following steps: 4 g of polyethylene glycol 400, 3 g of sodium hydroxypropyl methylcellulose, 0.9 g of triethylamine, 0.3 g of 1,6-hexanediol, 0.2 g of tripropylene glycol and 0.55 g of polyoxyethylene glycerol ether MF-200A were mixed and then stirred to prepare the film-forming agent.

[0042] It is particularly important to emphasize that, unless otherwise specified, the raw materials, reagents or devices in this application can be obtained from conventional commercial channels.

[0043] Table 1 Mass ratio and process parameters of water-soluble solder paste raw material components of Examples 1 to 8 (unit: g) Table 2 Mass ratio of the raw material components of the water-soluble solder paste of Comparative Examples 1 to 4 (unit: g) Example 1: A water-soluble solder paste is prepared by the following steps: S1: Weigh the raw materials of each component of the water-soluble flux corresponding to Example 1 in Table 1 according to parts by weight, put them into a reactor and mix them, then heat them to 50°C, set the stirring speed to 1600 r / min, stir for 3 hours, cool to room temperature and maintain for 1 hour, put them into a three-roll grinder and grind them to a particle fineness of ≤10 μm, let them stand for 2 days, and prepare a water-soluble flux.

[0044] S2: According to the weight ratio, 11.5g of water-soluble flux and 88.5g of tin powder were weighed, mixed, and stirred at 20r / min for 35min to clean up the residue. The vacuum degree was controlled at -0.09MPa, the vacuum stirring speed was 20r / min, and the vacuum stirring time was 18min to prepare a water-soluble solder paste.

[0045] Example 2: The preparation method of a water-soluble solder paste is the same as that of Example 1, except that the types, amounts, and process conditions of the raw materials are added according to those of Example 2.

[0046] Example 3: The preparation method of a water-soluble solder paste is the same as that of Example 1, except that the types, amounts, and process conditions of the raw materials are added according to those of Example 3.

[0047] Example 4: The preparation method of a water-soluble solder paste is the same as that of Example 1, except that the types, amounts, and process conditions of the raw materials are added according to those of Example 4.

[0048] Example 5: The preparation method of a water-soluble solder paste is the same as that of Example 1, except that the types, amounts, and process conditions of the raw materials are added according to those of Example 5.

[0049] Example 6: The preparation method of a water-soluble solder paste is the same as that of Example 1, except that the types, amounts, and process conditions of the raw materials are added according to those of Example 6.

[0050] Example 7: The preparation method of a water-soluble solder paste is the same as that of Example 1, except that the types, amounts, and process conditions of the raw materials are added according to those of Example 7.

[0051] Example 8: The preparation method of a water-soluble solder paste is the same as that of Example 1, except that the types, amounts, and process conditions of the raw materials are added according to those of Example 8.

[0052] Comparative Example 1: The preparation method and process conditions of a water-soluble solder paste are the same as those in Example 1, except that the types and amounts of the raw materials are added according to those in Comparative Example 1.

[0053] Comparative Example 2: A method for preparing a water-soluble solder paste and process conditions are the same as those in Example 1, except that the types and amounts of the raw materials are added according to those in Comparative Example 2.

[0054] Comparative Example 3: The preparation method and process conditions of a water-soluble solder paste are the same as those in Example 1, except that the types and amounts of the raw materials are added according to those in Comparative Example 3.

[0055] Comparative Example 4: The preparation method and process conditions of a water-soluble solder paste are the same as those in Example 1, except that the types and amounts of the raw materials are added according to those in Comparative Example 4.

[0056] Material performance test: The water-soluble solder pastes obtained in Examples 1 to 8 and Comparative Examples 1 to 4 were subjected to various performance tests. The test methods are as follows: Cleaning condition: After welding, the residue is directly cleaned with water to check whether it is clean.

[0057] Room temperature viscosity: At room temperature, stir the water-soluble solder paste to ensure uniform distribution of the components. Stir in the same direction for 3 to 5 minutes to avoid entraining air. Insert the viscometer rotor deep into the middle of the solder paste and set the speed to 10 r / min. Record once every 5 minutes. Read three times in total and take the average value.

[0058] Lifespan: Store at 0-10°C, take out every month and observe for delamination (separation of tin powder and flux) and sedimentation (hard lumps at the bottom). Record the storage time. Lifespan ends when delamination or lumps appear on the surface and cannot be restored to uniformity by stirring.

[0059] Moisture absorption resistance: The water-soluble solder paste solder joints of the present application were placed in an environment with a temperature of 85°C and a humidity of 85% for 72 hours, and the residual corrosion on the solder joints was observed.

[0060] Tin creep height: tested in accordance with IPC-A-610 standard.

[0061] Expansion rate: Tested in accordance with JIS Z 3197 standard.

[0062] The test properties of the water-soluble solder pastes of Examples 1 to 8 and Comparative Examples 1 to 4 are shown in Table 3 below: Table 3 Performance test results of Examples 1 to 8 and Comparative Examples 1 to 4 The water-soluble solder pastes of Examples 1 to 5 are prepared by combining the film-forming agent of the present application formula with an organic acid activator, a thixotropic agent, a surfactant, a corrosion inhibitor, an antioxidant, and a solvent to obtain a water-soluble flux. The water-soluble flux is combined with tin powder so that the prepared water-soluble solder paste can be washed off with water after welding, avoiding the problem of circuit board corrosion caused by using organic solvents for cleaning; the room temperature viscosity is in the range of 179 to 189 Pa·s, and the solder joints are placed in an environment of temperature 85°C and humidity 85% for 72 hours. The residue on the solder joints does not change color, no corrosion is observed, and the moisture absorption resistance is excellent; the storage life can reach more than 7 months, it is not easy to delaminate, and has good wetting performance; the welding performance is excellent, the tin climbing height during welding is ≥0.82mm, and the expansion rate is ≥83.1%, which meets the welding requirements of high-precision electronic components.

[0063] Compared with Example 1 of the water-soluble solder paste of Example 6, the film-forming agent of Example 6 adopts the film-forming agent of Comparative Example 1. The results show that the storage life, tin climbing height and expansion rate of the water-soluble solder paste of Example 6 are reduced. Compared with Example 1 of the water-soluble solder paste of Example 7, the film-forming agent of Example 7 adopts the film-forming agent of Comparative Example 2. The results show that the storage life and moisture absorption resistance of the water-soluble solder paste of Example 7 are better, but the residue is not clean after washing with water after welding. Compared with Example 1 of the water-soluble solder paste of Example 8, the film-forming agent of Example 8 adopts the film-forming agent of Comparative Example 3. The results show that the water-soluble solder paste of Example 8 also has the disadvantage of not having a long enough storage life. It can be seen that the present application adopts a film-forming agent prepared by a specific proportion of polyethylene glycol 400, sodium hydroxypropyl methylcellulose, VYBAR 825 polymer, triethylamine, 1,6-hexanediol, tripropylene glycol and polyoxyethylene glycerol ether MF-200A, which can improve the storage life, moisture absorption resistance, water washing cleanliness and other properties of the water-soluble solder paste.

[0064] Comparative Examples 1 and 2 were compared with Example 1. The film-forming agents used in Comparative Example 4 were used. The results showed that after cleaning with water after soldering, the viscosity of Comparative Example 1 at room temperature was only 152 Pa·s. After 72 hours at 85°C and 85% humidity, the solder joints showed whitish residue and corrosion patina, indicating poor moisture absorption resistance. The product had a shelf life of only three months, exhibited easy delamination, and exhibited low wetting properties. During soldering, the solder creep height was 0.70 mm, and the expansion rate was 76.5%, indicating average soldering performance. The test results for Comparative Example 2 were similar to those of Comparative Example 1.

[0065] Comparative Examples 3-4, compared with Example 1, used polyethylene glycol 10000 as the film-forming agent. The results showed that after soldering, the residue in Comparative Example 3 was not clean after water washing, and the room temperature viscosity was only 147 Pa·s. After the solder joint was placed in an environment with a temperature of 85°C and a humidity of 85% for 72 hours, the residue on the solder joint was whitish, with corrosion patina, and poor moisture absorption resistance. The storage life was only 4 months, the solder joint was prone to delamination, and the wettability was low. The solder creep height during soldering was 0.65 mm, and the expansion rate was 75.3%, indicating average soldering performance. Although the residue in Comparative Example 4 was clean after soldering, the room temperature viscosity was not high. After the solder joint was placed in an environment with a temperature of 85°C and a humidity of 85% for 72 hours, the residue on the solder joint was whitish, with corrosion patina, and poor moisture absorption resistance. The storage life, solder creep height, and expansion rate during soldering were also average.

[0066] It can be seen from this that the film-forming agent of the present application is beneficial for the water-soluble solder paste to form a protective film during the welding process, thereby preventing the oxidation of tin powder, improving the stability of the water-soluble solder paste, extending the storage life, and improving the moisture absorption resistance and welding performance of the water-soluble solder paste.

[0067] Obviously, the above embodiments of the present application are merely examples for clearly illustrating the present application, and are not limitations on the implementation methods of the present application. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. Any obvious changes or modifications derived from the technical solution of the present application are still within the scope of protection of the present application.

Claims

1. A water-soluble solder paste, characterized in that: The invention comprises a water-soluble soldering flux and tin powder, wherein the mass ratio of the water-soluble soldering flux to the tin powder is 1: (7-10); The water-soluble soldering flux comprises the following components in parts by weight: 45~55 parts of film-forming agent; 8-12 parts of organic acid active agent; 6~8 parts of thixotropic agent; 0.3~3 parts of surfactant; 1~3 parts of corrosion inhibitor; 3-5 parts of antioxidants; 25-35 parts of solvent; The raw materials for preparing the film-forming agent include polyethylene glycol 400, sodium hydroxypropyl methylcellulose, VYBAR 825 polymer, triethylamine, 1,6-hexanediol, tripropylene glycol and polyoxyethylene glycerol ether MF-200A.

2. The water-soluble solder paste according to claim 1, wherein The film-forming agent is a mixture of polyethylene glycol 400, sodium hydroxypropyl methylcellulose, VYBAR 825 polymer, triethylamine, 1,6-hexanediol, tripropylene glycol and polyoxyethylene glycerol ether MF-200A in a mass ratio of (4-6): (2-4.5): (1.5-3.5): (0.8-1.2): (0.3-0.7): (0.1-0.4): (0.5-0.7).

3. The water-soluble solder paste according to claim 1, wherein The organic acid active agent is selected from at least one of dodecanedioic acid, phenylsuccinic acid, glycolic acid, suberic acid, succinic acid, and hexadecanoic acid; And / or, the thixotropic agent is a bisamide thixotropic agent.

4. The water-soluble solder paste according to claim 3, characterized in that The bisamide thixotropic agent is selected from at least one of ethylene bis(12-hydroxystearamide), phenylene bisstearamide, and hexamethylenediamine bisstearamide.

5. The water-soluble solder paste according to claim 1, wherein The surfactant is selected from at least one of dimethyl silicone oil, oleyl alcohol polyoxyethylene ether, Surfynol 104 surfactant, and GE-511 surfactant; And / or, the antioxidant is selected from at least one of 2-ethylimidazole, benzimidazole, methylbenzotriazole, and benzotriazole; And / or, the solvent is selected from at least one of tetrahydrofurfuryl alcohol, tetraethylene glycol, diethylene glycol dibutyl ether, propylene glycol methyl ether, and dipropylene glycol dimethyl ether.

6. The water-soluble solder paste according to claim 1, characterized in that The particle size of the tin powder is 22-35 μm.

7. A method for preparing the water-soluble solder paste according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: Weighing raw materials of various components of a water-soluble soldering flux in parts by weight, mixing, heating, stirring, cooling, grinding, and allowing to stand to prepare a water-soluble soldering flux; S2: Weighing water-soluble flux and tin powder in parts by weight, mixing, stirring, and then vacuum stirring to obtain the water-soluble solder paste; Preferably, the preparation method of the film-forming agent comprises the following steps: The film-forming agent is prepared by mixing polyethylene glycol 400, sodium hydroxypropyl methylcellulose, VYBAR 825 polymer, triethylamine, 1,6-hexanediol, tripropylene glycol and polyoxyethylene glycerol ether MF-200A, and then stirring.

8. The method for preparing the water-soluble solder paste according to claim 7, wherein: In step S1, the heating temperature is 50-70° C., the stirring speed is 1200-1800 r / min, the stirring time is 3-5 h, and the standing time is 2-3 d.

9. The method for preparing the water-soluble solder paste according to claim 7, wherein: In step S2, the stirring speed is 20 to 30 r / min, the stirring time is 35 to 50 min, the vacuum degree of the vacuum stirring is -0.09 MPa to -0.1 MPa, the vacuum stirring speed is 20 to 30 r / min, and the vacuum stirring time is 15 to 20 min.

10. Use of the water-soluble solder paste according to any one of claims 1 to 6 or the water-soluble solder paste prepared by the preparation method according to any one of claims 7 to 9 in electronic soldering materials.

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