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CN-120170328-B - VOC-free water-soluble environment-friendly soldering flux and preparation method thereof

CN120170328BCN 120170328 BCN120170328 BCN 120170328BCN-120170328-B

Abstract

The invention relates to a VOC-free water-soluble environment-friendly soldering flux and a preparation method thereof, belonging to the technical field of soldering fluxes. The polyethylene glycol-maleic anhydride grafted copolymer, fumaric acid, zinc citrate nano particles, nonionic surfactant, water-soluble cationic chitosan quaternary ammonium salt, pH buffering agent and deionized water are adopted, the amphiphilic molecular skeleton formed by the polyethylene glycol-maleic anhydride grafted copolymer reduces the surface tension of a solution through adjusting the grafting rate, the stability is enhanced through intermolecular hydrogen bonding with fumaric acid, the stability of the scaling powder in the welding process is improved, a protective film is formed after welding, the component does not contain VOC (volatile organic compounds), the pollution to the environment is reduced, the health risk to operators is reduced, the VOC emission in the welding process is reduced, and the environment-friendly effect is achieved.

Inventors

  • ZHANG YUHANG
  • XIE PENG
  • WU JIAQIAN
  • HAN ZHENFENG
  • LIN YUANHUA

Assignees

  • 广州中乌焊接材料科技有限公司

Dates

Publication Date
20260505
Application Date
20250508

Claims (9)

  1. 1. The VOC-free water-soluble environment-friendly soldering flux is characterized by comprising, by weight, 15-25 parts of polyethylene glycol-maleic anhydride graft copolymer, 2-5 parts of fumaric acid, 0.5-4 parts of zinc citrate nano particles, 0.5-1 part of nonionic surfactant, 0.7-1 part of water-soluble cationic chitosan quaternary ammonium salt, 2-4 parts of pH buffering agent and 50-70 parts of deionized water.
  2. 2. The VOC-free water-soluble environmentally friendly soldering flux of claim 1, wherein the nonionic surfactant is any one of polyvinyl alcohol, polysorbate-20 and sorbitol monooleate.
  3. 3. The VOC-free water-soluble environment-friendly soldering flux of claim 1, wherein the grafting rate of the polyethylene glycol-maleic anhydride graft copolymer is 35-45%.
  4. 4. The VOC-free water-soluble environment-friendly soldering flux according to claim 1, wherein the preparation method of the polyethylene glycol-maleic anhydride graft copolymer comprises the following steps of heating and melting polyethylene glycol under the protection of inert atmosphere, dropwise adding maleic anhydride and p-toluenesulfonic acid catalyst, and stirring until the acid value reaches 120-140 mgKOH/g.
  5. 5. The VOC-free water-soluble environment-friendly soldering flux of claim 1, wherein the zinc citrate nano-particles have a particle size of 50-80nm.
  6. 6. The VOC-free water-soluble environment-friendly soldering flux of claim 1, wherein the preparation method of the zinc citrate nano-particles is characterized in that cetyl trimethyl ammonium bromide, n-butanol and cyclohexane are mixed to form microemulsion, zinc nitrate solution and sodium citrate solution are added into the microemulsion in a dropwise manner, zinc citrate precipitate is generated by ultrasonic emulsification, and the nano-particles are obtained by vacuum drying.
  7. 7. The VOC-free water-soluble environment-friendly soldering flux of claim 6, wherein the mass ratio of hexadecyl trimethyl ammonium bromide, n-butanol, cyclohexane, zinc nitrate and sodium citrate is 0.8-1.2:2.5-3.5:5-7:1.5-2:2-2.5.
  8. 8. The VOC-free water-soluble environmentally friendly soldering flux of claim 1, wherein the pH buffering agent is triethanolamine lactate.
  9. 9. A method for preparing the VOC-free water-soluble environment-friendly soldering flux according to any one of claims 1 to 8, which is characterized by comprising the following steps: (1) Adding fumaric acid into deionized water, and adding polyethylene glycol-maleic anhydride graft copolymer to mix hydrogen bonds to form a compound; (2) Adding zinc citrate nano particles into the compound, sequentially adding a nonionic surfactant, a water-soluble cationic chitosan quaternary ammonium salt and a pH buffer after ultrasonic treatment, and regulating the pH to 6.8-7.0.

Description

VOC-free water-soluble environment-friendly soldering flux and preparation method thereof Technical Field The invention belongs to the technical field of soldering flux, and relates to a VOC-free water-soluble environment-friendly soldering flux and a preparation method thereof. Background Soldering flux aids and facilitates the soldering process while providing protection against oxidation, with rosin resins being the most common type of flux. Rosin flux is popular for its superior wettability and insulating properties by reducing the surface tension of the solder to promote flow and wetting of the solder to form a strong soldered connection. However, such conventional fluxes typically contain Volatile Organic Compounds (VOCs) that can release harmful gases during the soldering process, adversely affecting the environment and the health of the operator. In addition, rosin resins leave residues after soldering, which may lead to reduced electrical properties under high temperature and humid conditions, thus often requiring additional cleaning steps, which not only increases production costs, but also creates environmental concerns. With the increasing environmental awareness and the increasing strictness of regulations, water-soluble fluxes have been developed as an alternative. The water-soluble soldering flux is generally composed of water-soluble organic acids, polymers and other additives, and its non-toxic and harmless characteristics make it an ideal choice for green manufacturing. The water-soluble soldering flux can be easily cleaned after being used, so that residues after welding and influence on the environment are reduced. At the same time, they do not release VOCs during the welding process, thereby reducing the threat to the health of the operator. Because of these advantages, water-soluble fluxes are increasingly being used in the manufacture of various types of electronic products, particularly in fields requiring high reliability and stringent environmental requirements, such as consumer electronics, automotive electronics, and medical equipment. With the continuous development of welding technology, no-clean soldering flux is widely used. One of the major advantages of the no-clean flux is that no cleaning is required, reducing additional operations and costs in the production process. However, the problem of no-clean flux is also becoming evident, especially the risk of its residues exceeding the standard. May affect electrical performance and even negatively impact the long-term stability of the component. Residues may cause a decrease in conductivity, especially in high frequency or high temperature operating environments, thereby affecting the overall performance of the product. Although water-soluble fluxes have significant advantages in terms of environmental protection and safety, they still present challenges in practical applications. First, the wettability and fluidity of water-soluble fluxes are generally inferior to conventional rosin-based fluxes, which may result in reduced reliability of the solder joints. In addition, the thermal stability of the water-soluble flux under high temperature soldering conditions needs to be further improved to ensure that it does not decompose or fail during soldering. Disclosure of Invention In order to solve the problems of poor wettability of water-based soldering flux and excessive residues of no-clean soldering flux, the invention provides a molecular structure modification method, which creatively improves the performance of the soldering flux. By modifying the molecular structure of the components such as the water-soluble organic acid, the polymer and the like, the invention realizes the remarkable improvement of the wettability and the fluidity of the soldering flux, thereby effectively improving the soldering effect. In addition, the modified soldering flux can form a more uniform and stable protective film after welding, reduces the formation of residues and ensures that the residues after welding are within the safety standard range. In order to achieve the aim, the invention provides the technical scheme that the VOC-free water-soluble environment-friendly soldering flux comprises, by weight, 15-25 parts of polyethylene glycol-maleic anhydride graft copolymer, 2-5 parts of fumaric acid, 0.5-4 parts of zinc citrate nano particles, 0.5-1 part of nonionic surfactant, 0.7-1 part of water-soluble cationic chitosan quaternary ammonium salt, 2-4 parts of pH buffering agent and 50-70 parts of deionized water. As a preferable technical scheme of the invention, the nonionic surfactant is any one of polyvinyl alcohol, polysorbate-20 and sorbitol monooleate. As a preferable technical scheme of the invention, when the grafting rate of the polyethylene glycol-maleic anhydride graft copolymer is controlled to be 35-45%, the surface tension of the solution is reduced, the content of carboxylic acid groups and the flexibility of a molecular chain a