Preparation Of Sn0.3Ag0.7Cu Lead-Free Solder Paste And Its Impact On Performance

For fitting the free-Pb requirement of Surface Mount Technology and the development of electronic products oriented to microstructure, thin type and high precision, the free- Pb solder paste has been one of the most significant and inevitable electronic accessories, which quality directly related to the quality of surface mount components.In this thesis, no-clean flux with excellent performance was produced, starting optimization and performance testing of flux and its effective composition. In addition, the effect of the ratio of thixotropic agent in flux and alloy powder on rheology and printing performance of solder paste were discussed. Finally, the synthetic performance of Sn0.3Ag0.7Cu solder paste was investigated, compared with commercial solder pastes. So the main conclusions is following:(1)The composition of flux matrix are including: the solvent system Diethylene glycol dibutyl ether and solvent,whose mass ratio is 2:3, the film-forming agent system of Rosin B, full hydrogenated rosin and polymerized rosin, whose mass ratio is 3:2:1,and TA3 as thixotropic agent; the quality ration of mixed solvent : compound rosin : TA3 is 40:45:5. The mass of sebacic acid, itaconic acid, and triethanolamine of active agent respectively is 1.7wt%, 4.8wt.% and 1.5wt.% in flux. The mass of benzene Benzotriazole as copper anti-corrosion agent is 1.0 wt.%, the mass of N, N'- ethylene bisstearamide as mold release is 0.5wt.%, the mass of 2.6- Ditertbutyl p-cresol as antioxidant is 0.5wt.%. A rosin-based, halogen-free and no-clean flux is developed and investigated, which have stable physical properties,the appearance of milky white viscous paste, acid value of 147.26 mgKOH·g-1, Non-volatile matter content of 27.5%, small resistance; good wetting performance and excellent overall flux performance.(2)Meanwhile, the effect of the ratio of thixotropic agent in flux and Sn0.3Ag0.7Cu(type 4)alloy powder on rheology and printing performance of solder paste were studied. When the mass proportion of alloy powder is 88.5wt.% and dosage of TA3 is 5.0g(proportionally5.0wt.% of flux), solder paste has moderate viscosity, maximum thixotropic index and adhesion value, and optimal thermal anti-slump performance.(3)The lead-free solder paste is prepared by mixing Sn0.3Ag0.7Cu(type4)alloy powder and homemade flux, No. SD01. Comparing commercial paste SUPER0307-4 and OM338, SD01 paste has a suitable viscosity and good thixotropy and excellent adhesion, excellent cold and thermal anti-slump performance, fitting for printing high-end fine pitch; SD01 solder tin ball is qualified, and the round of copper solder spreading has a smaller residual transparently and welding spot is full; Finally, SD01 paste has better weldability; as well as having the appearance of uniform viscous paste, being acid value of 133.13 mgKOH·g-1 and halogen-free.