Water-based soldering flux

Abstract

The invention relates to a water-based soldering flux. The water-based soldering flux comprises the following components in percentage by weight: 2.0%-3.5% of an activating agent, 1.5%-6.5% of water-based polyacrylate, 0.2%-0.8% of a surfactant, 0.1%-0.4% of an anti-mildew agent, 0.1%-0.5% of a corrosion inhibitor and 88.3%-96.1% of deionized water. The water-based soldering flux does not contain volatile organic solvent components, is halogen-free, and is added with water-based polyacrylate. The anti-mildew agent and the corrosion inhibitor can improve the wettability and the leveling property of the water-based soldering flux, effectively inhibit mildew growth and reduce corrosion, cleaning is not needed after welding, and the water-based soldering flux is really safe and environmentally friendly and is suitable for being coated on the welding face of a PCB in a spraying, dipping and foaming mode.

Description

Technical Field

[0001] The invention relates to a soldering flux, in particular to a water-based soldering flux for wave soldering. Background Art

[0002] In the field of electronic soldering, flux is a very important auxiliary material. Traditional flux is mainly organic solvent type, with low boiling point alcohols (such as methanol, ethanol, isopropanol, etc.) as carriers. Although these substances themselves do not have a particularly large impact on the human body and the environment, the products after high temperature decomposition may also have adverse effects on the environment and the human body. In recent years, people have begun to develop fluxes with water as the solvent matrix, that is, "water-based fluxes", which have the advantages of environmental protection, no need to wash and safety, but they cause serious corrosion to circuit boards and conveyor belts during lead-free soldering. In addition, the growth of microorganisms (such as bacteria, fungi and molds) not only affects solderability, but also the microbial residues after soldering affect conductivity, etc. Summary of the invention

[0003] In view of the application difficulties of the existing water-based flux, the present invention provides a water-based flux, which improves the wettability and leveling properties of the water-based flux while effectively inhibiting the growth of mold and reducing corrosion. It does not need to be cleaned after welding, and is a truly safe and environmentally friendly flux. It is suitable for spraying, dipping, and foaming to coat it on the welding surface of the PCB board. To achieve the purpose of the present invention, the following technical scheme is adopted.

[0004] A water-based soldering flux of the present invention contains, by weight percentage: Activator 2.0%~3.5% Water-based polyacrylate 1.5%~6.5% Surfactant 0.2%~0.8% Antifungal agent 0.1%~0.4% Corrosion inhibitor 0.1%~0.5% The rest is deionized water as solvent, and the percentages are by weight.

[0005] The activator is a mixture of organic acid and organic amine, wherein the organic acid content is 80% to 90% of the activator, and the organic amine content is 10% to 20% of the activator, and the percentages are all weight percentages. The organic acid is one or more of oxalic acid, malonic acid, succinic acid, tartaric acid, itaconic acid, 2-hydroxybenzoic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, etc. The organic amine is one or more of triethanolamine, diethylenetriamine, triethylamine, urea, ethylenediamine, etc. The main function of the activator is to remove oxides on the lead pins and oxides on the surface of the molten solder.

[0006] The main function of the water-based polyacrylate is to improve the wettability and leveling properties of the water-based soldering flux.

[0007] The surfactant is composed of a nonionic surfactant or a cationic surfactant, such as one or more of dodecylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, dodecyl dimethyl amine oxide, and tetradecyl dimethyl amine oxide. Its main function is to reduce surface tension, enhance wetting power, and improve solderability.

[0008] The antifungal agent is one or a mixture of ethylene glycol chitosan, hydroxypropyl chitosan, turmeric root alcohol, etc. Its main function is to inhibit the growth of microorganisms (such as bacteria, fungi and molds) in water and improve weldability and service reliability after welding.

[0009] The corrosion inhibitor is one or a mixture of benzotriazole, 2-thiolbenzotriazole, toluenethiourea, propyl sulfide, diamylamine, formaldehyde, para-thiocresol, etc. Its main function is to reduce the corrosion of water-based soldering flux to circuit boards and conveyor belts.

[0010] The preparation process of the water-based soldering flux of the present invention is as follows: the first step is to weigh 0.2% to 0.8% of a surfactant and 86.5% to 97.89% of deionized water, pour them into a reaction kettle, mix and stir for 15 minutes, and heat to 40°C ± 2°C; the second step is to slowly add 2.0% to 3.5% of an activator (the activator is composed of 80% to 90% of an organic acid and 10% to 20% of an organic amine) while stirring, and stir for 120 minutes; the third step is to add 0.1% to 0.4% of an antifungal agent and 0.1% to 0.5% of a corrosion inhibitor, and stir for 30 minutes to obtain the water-based soldering flux of the present invention.

[0011] The water-based soldering flux of the present invention uses deionized water as a solvent, does not contain volatile organic matter, is halogen-free, effectively inhibits the growth of mold and reduces corrosion while improving the wettability and leveling properties of the water-based soldering flux, does not need to be cleaned after welding, is a truly safe and environmentally friendly soldering flux, is suitable for being coated on the welding surface of a PCB board in a spraying, dipping or foaming manner, and realizes lead-free and halogen-free high-quality welding of electronic products. [Specific implementation method] Example 1: Malonic acid 1.2% Itaconic acid 0.4% Diethylenetriamine 0.2% Water-based polyacrylate 1.5% Octylphenol polyoxyethylene ether 0.2% Hydroxypropyl chitosan 0.1% Toluenethiourea 0.1% Deionized water 96.3% Example 2: 2-Hydroxybenzoic acid 1.5% Adipic acid 0.6% Urea 0.4% Water-based polyacrylate 3.3% Nonylphenol polyoxyethylene ether 0.4% Hydroxypropyl chitosan 0.25% 2-Mercaptobenzotriazole 0.25% Deionized water 93.3% Example 3: Glutaric acid 1.3% Tartaric acid 0.5% Pimelic acid 0.4% Ethylenediamine 0.5% Water-based polyacrylate 4.5% Tetradecyl dimethylamine oxide 0.3% Dodecylphenol polyoxyethylene ether 0.3% Ethylene glycol chitosan 0.3% Benzotriazole 0.4% Deionized water 91.5% Example 4: Suberic acid 1.1% Malonic acid 2.05% Diethylenetriamine 0.7% Water-based polyacrylate 6.5% Nonylphenol polyoxyethylene ether 0.8% Hydroxypropyl chitosan 0.4% 2-Mercaptobenzotriazole 0.5% Deionized water 87.95% Table 1 is the comparative data of the test results of solderability, copper mirror corrosion and copper plate corrosion of Examples 1-4 of the present invention.

[0013] Table 1 Comparison of the test results of solderability and copper mirror corrosion of Examples 1-4

Claims

1. A water-based soldering flux, the components and contents of which are: Activator 2.0%~3.5% Water-based polyacrylate 1.5%~6.5% Surfactant 0.2%~0.8% Antifungal agent 0.1%~0.4% Corrosion inhibitor 0.1%~0.5% The rest is deionized water as solvent, and the percentages are by weight.

2. A water-based soldering flux according to claim 1, Features: The activator is a mixture of organic acid and organic amine, wherein the organic acid content is 80-90%, and the organic amine content is 10%-20%, and the percentages are all weight percentages.

3. A water-based soldering flux according to claim 1, Features: The organic acid is one or more of oxalic acid, malonic acid, succinic acid, tartaric acid, itaconic acid, 2-hydroxybenzoic acid, glutaric acid, adipic acid, pimelic acid, suberic acid and the like.

4. A water-based soldering flux according to claim 1, Features: The organic amine is one or more of triethanolamine, diethylenetriamine, triethylamine, urea, ethylenediamine and the like.

5. A water-based soldering flux according to claim 1, Features: The surfactant is a nonionic surfactant or a cationic surfactant, such as one or more of dodecylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, dodecyl dimethyl amine oxide, and tetradecyl dimethyl amine oxide.

6. A water-based soldering flux according to claim 1, Features: The antifungal agent is one or a mixture of ethylene glycol chitosan, hydroxypropyl chitosan, turmeric root alcohol and the like.

7. A water-based soldering flux according to claim 1, Features: The corrosion inhibitor is one or a mixture of benzotriazole, 2-thiolbenzotriazole, toluenethiourea, propyl sulfide, diamylamine, formaldehyde, para-thiocresol and the like.

8. The method for preparing a water-based soldering flux according to claim 1, It is characterized in that The method comprises the following steps: a first step, weighing 0.2% to 0.8% of a surfactant and 86.5% to 97.89% of deionized water, pouring the mixture into a reaction kettle, mixing and stirring for 15 minutes, and heating the mixture to 40°C ± 2°C; a second step, slowly adding 2.0% to 3.5% of an activator (the activator is composed of 80% to 90% of an organic acid and 10% to 20% of an organic amine) while stirring, and stirring for 120 minutes; a third step, adding 0.1% to 0.4% of an antifungal agent and 0.1% to 0.5% of a corrosion inhibitor, and stirring the mixture for 30 minutes, thereby obtaining a water-based soldering flux.

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