Development And Performance Research Of A New Type Of Halogen-free Flux For Lead-free Soldering

Flux is a key material in the field of sealing assembly and welding in electronic industry.The quality of flux directly affects the quality and reliability of welding.With the development trend of green lead-free electronic industry and the improvement of environmental protection requirements,traditional halogen-containing flux can no longer meet the requirements of new lead-free soldering process.Therefore,the development of a new halogen-free flux for lead-free soldering has gradually become a hot research topic in the industry.In this paper,the principle of action of active agent,solvent,carrier,surfactant and other components in halogen-free soldering flux is explored and studied.Orthogonal test method is used for screening and proportion optimization.Through spreading diffusion rate,surface insulation resistance,copper mirror corrosion test and testing of acid value,halogen and splash rate of soldering flux,a flux for lead-free solder Sn-0.7Cu and a flux without washing are developed.The specific research results are as follows:(1)The flux of the medicine core tin wire uses hydrogenated rosin compounded polymerized rosin as a carrier;When N-acid,amine succinate and triethanolamine are mixed as active ingredients,and the ratio is 8:4:1 and the total mass fraction is 3.5%,the welding effect is very good.The addition of surfactant can effectively reduce the surface tension and significantly increase the spreading diffusion rate,but the addition amount of surfactant is not too much,and 0.3%is the best.A small amount of BTA can reduce residual corrosion after welding and improve reliability.After testing,the prepared flux for the flux core tin wire has large spatter,and the spatter value can be reduced from 0.9%to 0.2%by adding 5.0%A oil.(2)Flushing-free flux uses itaconic acid,diphenylguanidine and triethanolamine as active ingredients,and the mass fractions are determined to be 1.0%,2.0%and 0.3%respectively according to orthogonal tests.The addition of surfactant can significantly improve spreading diffusion rate,with the best mass fraction being 0.3%.BYK333 with mass fraction of 0.15%,OP-10 with mass fraction of 0.1%and TX-10 with mass fraction of 0.05%are determined according to orthogonal test.The solvent ethylene glycol phenyl ether and turpentine are used as a mixed solvent in a ratio of 1:1,and the melting boiling point is more appropriate.After testing,the developed wash-free liquid flux has a great irritating smell when in use.The pungent smell can be effectively reduced by adding menthol,the optimal addition mass fraction of menthol is 3.0%.(3)Apply the formulated flux to actual production and check the usage of flux.For example,soldering iron combined with flux-cored tin wire is used for actual circuit board welding,and the solder without cleaning flux is used for wave soldering with good welding effect.