Environmental-friendly water-soluble flux and preparation method thereof

Abstract

The invention relates to an environmental-friendly water-soluble flux which is matched with lead-free solder; the environmental-friendly water-soluble flux comprises anhydrous citric acid, DL-malic acid, triethanolamine, modified polyvinylalcohol, polymethyl acrylate, vinyl acetate-ethylene copolymer powder, hydroxyethyl methyl cellulose ether, surfactant, benzotriazol, phenol and mixed solvent; the anhydrous citric acid, the DL-malic acid, the triethanolamine, the modified polyvinylalcohol, the polymethyl acrylate, the vinyl acetate-ethylene copolymer powder and the hydroxyethyl methyl cellulose ether are prepared into a complex active substance A through microencapsulated coating treatment; and the mixed solvent, the surfactant, the benzotriazol, the phenol, the modified polyvinylalcohol, the polymethyl acrylate and the complex active substance A are uniformly mixed by weight ratio to obtain the environmental-friendly water-soluble flux. The environmental-friendly water-soluble flux can effectively assist lead-free solder, particularly applicable to Sn-Ag-Cu lead-free solder, can enhance the solderability of the lead-free solder, can adapt to the high welding temperature requirement on the lead-free solder, has small action to the corrosion of lead-free solder alloys and little residue after welding, can be cleaned by water, has good welding point quality, clean surface and strong stability, and a dried circuit board has higher insulation resistance value.

Description

technical field [0001] The invention relates to flux, in particular to an environment-friendly water-soluble flux for lead-free solder and a preparation method thereof. Background technique [0002] Sn-Pb alloy, as the main packaging material in the modern electronics industry, plays a dominant role in the assembly of electronic components, and has the characteristics of low cost, good electrical conductivity, and excellent mechanical welding performance. However, lead and lead compounds are poisonous and harmful substances. Solder is harmful to human health in the process of production and use, and it is easy to cause cancer. Soldering waste will also seriously pollute the environment. With the increasingly perfect and strict environmental protection laws and regulations, the call for prohibiting the use of lead is growing louder and louder. [0003] Therefore, various countries have promulgated laws and regulations prohibiting the use of lead-containing solder in the elec...

AI Technical Summary

Problems solved by technology

[0004] Sn-Ag-Cu alloys are a type of lead-free solder that has been studied internationally and has good application prospects. However, it was found during research and use that compared with traditional Sn-Pb solder, Sn-Ag- Cu-based lead-free solder has poor wettability, is easy to oxidize, and has a high melting point

Therefore, the flux suitable for Sn-Pb solder is not suitable for Sn-Ag-Cu lead-free solder. One is that this kind of flux can not help the wetting ability of Sn-Ag-Cu lead-free solder; -Ag-Cu based lead-free solder has a high soldering temperature. The increase of the melting point means that the soldering temperature must be increased. On the one hand, the increase in the soldering temperature makes the solder joints easier to oxidize, and at the same time increases the volatilization of the active agent in the flux. It does not have a good activation and protection effect, so that the solder joints are more likely to be oxidized