| With the development of the electronics industry and the surface mount technology (SMT), flux has become one of the most important materials in the assembly of electronics industry. This thesis briefly describes the definition, function, composition, development status and basic knowledge of the flux. Based on the previous study, we focus on the film-forming agent, corrosion inhibitor on the performance of fluxing and dose-effect relationship. The contents are shown as follow:Succinic acid and malic acid was selected as the active agent; while selectint glycol, iso-triol and ethylene glycol ether as the solvent; OP-10 as the surface active agents, polyethylene glycol series substance (e.g. PEG-1000, PEG-2000, PEG-4000, PEG-6000) as the film-forming reagent. And then the as-prepared the flux was tested with the Sn-3.0Ag-0.5Cu lead-free solder. Lastly the amount of addition of the film-forming reagent to the flux was optimized based on its performance.The results showed that the spreading area of the fluxes increased due to the addition of different molecular weight of polyethylene glycol. As for PEG-1000,2000, and 4000, with the increasing of its amount, the spreading area increased firstly, and then decreased. However, the result was different for PEG-6000, when the addition amount was 0.25%, the spreading area reached the maximum value 61.15 mm2. Larger amount of addition and high molecular weight of the film-forming reagent, is likely to induce more tacky of the copper board, and more amount of non-volatile matter left in the copper board. But the film-forming reagent exhibits little effect on the acidity of the fluxes. The spreading test and the scanning electron microscope results indicated that the film-forming reagent possibly formed a protective film-coating under the welding temperature and the copper plate surface was smooth, which could improve the corrosion resistance of the flux.Selecting imidazole (IM), benzimidazole (BIA), benzotriazole (BTA) as the corrosion inhibitors, weight loss method, electrochemical method and scanning electron microscope(SEM) were employed to analyze and evaluate its corrosion inhibition performance and EIS spectra. Compared with the corrosion inhibition and EIS spectra, and the corrosion mechanism was explored for the three corrosion inhibitors and the complex corrosion inhibitors in the 2.0% (wt) of succinic acid and malic acid solution. By comparing the scanning electron micrographs of the copper surface with and without corrosion inhibitors, the corrosion inhibiting effect has also been analyzed. Furthermore, adding other components to the flux, such as co-solvents, surfactants, film formers, the adding amount of the inhibitors to the solder spreading ability and the corrosive impact of flux were studied by spreading test formulated. At the same time, the impact on the performance of the OP-10 was discussed, and the optimal flux formula was obtained in the end. When compared the performance of the flux with two commercially available products, the experiments results revealed that the corrosion inhibition efficiency firstly increased and then decreased with its concentration of all three corrosion inhibitors. The amount of imidazole, if higher than 0.04%, accelerated the corrosion of copper. When the content of benzotriazole was 0.08%, it showed better corrosion resistance, which was 88.78%. Benzimidazole and benzotriazole showed good corrosion inhibition efficiency in mixture form with the optimum ratio 1:1, the while corrosion inhibition efficiency reached to 94.25%. The scanning electron microscopy results showed that the addition of corrosion inhibitors formed a tight complex protective film to prevent the corrosion and protect the copper effectively. The spreading test results showed that:the mixed corrosion inhibitor could effectively reduce the copper corrosion, together with increase of the solder spread ability and the reduce amount of BTA. The best addition was BIA 0.04%; BTA 0.04%, which the prepared flux had the best performance, and spreading an area was 62.05 mm. Meanwhile, OP-10 played an important role in lowering the interfacial tension at low concentrations, and did not increase the corrosion. It was a good surface active agent, which could be used as the development of a VOC-free flux, and the best amount was 0.3%.After the comprehensive performance tests of the final optimized flux formulations, we found that the flux has no obvious stratification or dispersoids, the spot was bright, non-tacky, low residue, halogen-free, low solids content (2.63%).The maximum wetting force was 3.79 mN, and the wetting time was 1.38 s, and the insulation resistance value reached 1010 Q, which met the industrial demand. Compared with the commercially available flux, the results showed that our flux’s wetting force, fluxing, low residue, low corrosive, safety and environmental friend. |
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