Studying On Preparation And Properties Of Halogen-free, Rosin-free,and No-clean Flux For Lead-free Sn-Cu Solders

Compared with the traditional Sn-Pb solder, Sn-Cu based lead-free solder has poor wettability, easily oxidized, and a high melting point. The increase of melting point means that the soldering temperature must be increased. On the one hand, caused by damage to the board components, on the other hand lead to flux volatilization of the active agent. This would not achieve good activation and protection Faced on the problems about the use of lead-free solder, in order to ensure to improve the lead-free solder wetting properties and succeed in welding. Therefore research and supporting the use of lead-free solder flux, researchers are increasingly concerned about it.Currently, most of the flux containing a halogen. This will cause corrosive residue after welding. Not only it has potential adverse effect on mechanical and electrical properties of the product, but also the cleaning agent which cleans the residue will destroy the ozone layer. Meanwhile it will have an affect on the human environment. It does not comply with the requirements of environmental protection. So Therefore, no-clean flux will play an important role in the future of the electronics industry. It can not only reduce costs and shorten the production cycle, but also can reduce the production process. It has important economic and social benefits, has a broad market prospects in the electronics industry.The topic will as manifested in the actual welding process according to Sn-0.7Cu lead-free solder alloy for the study, according to the flux composition of analysis and research, with reference to national standard no-clean flux performance, combined with the actual production process, the development of a Sn-0.7Cu lead-free solder in the welding process play a good fluxing no-clean flux. In this experiment, the deionized water was chose as a solvent. When selecting organic acid activator, we need to consider the solubility of the organic acids. In order to ensure the selection of several organic acids can be completely dissolved, we should to be added to the alcohol ether cosolvent to help organic acids dissolved. Meanwhile the wetting force and activity of the selected organic acids should be strong. By orthogonal experiments shows that when compound succinic acid, adipic acid and itaconic acid showed better welding activity. Select sorbitol, diethylene glycol diethyl ether and nitroethane alcohol as a cosolvent, it has a better co-insoluble and fluxing effect after complex cosolvent. Due to the surface tension of the solvent water is larger, the selected non-ionic surface active agent BYK33and OP-10plays a role preferably reduce the surface tension. Add to tert-butyl hydroquinone and natural antibacterial agent E, can effectively inhibit mildew, improve the flux shelf life.According to the provisions of the national standard no-clean flux performance test methods, conduct to performance testing on the developed flux. The test results showed that the subject developed halogen-free rosin no-clean flux is a yellow transparent, good physical stability, free of halogen, long shelf life, the high cost of a new water-based flux. In the actual process of the application process, with good effect of flux residue after soldering, basic non-corrosive to the base metal, lead-free solder expansion rate of76.5%can be achieved no-clean, in line with the relevant national standards, the flux in the market has a strong competitive edge.