Study On The Preparation And Performance Of No-clean Fulx And Lead-free Solder Paste

With the development of electronic products oriented to microstructure, thin type and high precision, Surface Mount Technology (SMT) has been one of the most popular technologies in electronic mounting industry. Solder paste, whose performance directly influences the quality of welding and decides the quality of products, is the inevitable material in SMT. 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 synthetic performance of Sn-3.0Ag-0.5Cu was investigated.Viscosity of solder paste was tested by using a rotaty thermometer. Shear strength of solder joint was measured by using mechanical testing machine. Microstructure and fracture of solder joint were observed by using Scanning Electron Microscopy (SEM), and the composition of solder joint were tested and analyzed by Energy Dispersive Spectrometer (EDS). The results were following as:1) The homemade clean-free flux includes matrix and effective components. The composition of flux matrix are including: hydrogenated rosin and polymerized rosin compound, whose mass ratio is2:3; diethylene glycol, ethylene glycol monobutyl ether and solvent A compound, whose volume ratio is1:2:1; ST, H as thixotropic agents, the quality ration of compund rosin:H:ST:mixed solvent is50:2:3.5:35.Take the causticity of the active agent on the copper and solder spread area as an index:select succinic acid, adipic acid as the main active agents, surfactant A as a secondary active agent, triethanolamine as a pH buffer; the total amount of succinic acid and adipic acid is5wt%, whose compound mass ratio is3:2; the dosage of active agent A is0.3wt%; the dosage of triethanolamine is3wt%; the mass ratio of benzotriazole and8-hydroxyquinoline is1:1and the total dosage of them is1wt%.2) The rosin-based halogen-free no-clean flux is a milky viscous paste, which have stable physical properties, pH6.0, halogen-free, low corrosivity, non-volatile content of31.5%, the spreading area of38.18 mm2, and excellent performance.3) Compared with commercial PNF306solder paste and ALPHA OM338solder paste, homemade ZZ01solder paste has a suitable viscosity and excellent thixotropy, which can meet the requirements of high-end fine-pitch printing. All the three kinds of solder paste have excellent anti-cold collapse performance and thermal subsidence properties, ALPHA OM338solder paste> ZZ01solder paste>PNF306solder paste. ALPHA OM338solder paste and the ZZ01paste solder passed the solder balling test, while PNF306solder paste failed. The spreading area of ZZ01solder paste, PNF306solder paste and ALPHA OM338solder paste are38.24mm2,36.05mm2,40.01mm2, respectively. ZZ01solder paste with least residues is thin and transparent. IMC layer by ZZ01solder paste solder joint is thin, dense and uniform. The shear strength of ZZ01solder paste, PNF306solder paste, and ALPHA OM338solder paste is45.12MPa,40.22MPa and48.82MPa, respectively. All of fracture modes are ductile fracture.