Development Of Halogen-free, VOC-free, And Water-based Flux For Lead-free Solder

With the extensive application and development of the lead-free solders in the electronics industry, the flux has become an important auxiliary materials in the surface mount technology. compared to the Sn-Pb solders, the most of lead-free solders have the problems such as high-cost, high melting point, poor wetting properties, and oxidized easily. Therefore, the development of an excellent flux supporting the use of a lead-free solder is increasingly becoming a focus and key for researchers.In this thesis, Sn-3.OAg-0.5Cu was studied as a lead-free solder, a halogen-free VOC-free and water-based flux for the lead-free solders was developed. The main characteristic of the flux was using deionized water as the carrier solvent, and does not contain glycol or other volatile flammable substances; it is safe and environmental friendly. It is called a new "green flux". In this thesis, two aspects of the work were done, the development and performance testing of the water-based flux. The detailed contents are as follows:(1) Use the spreading rate as the main index, first filter out the good performance of several organic acids and organic amine activators by contrast and performance of a single active agent, and then use a variety of organic acids and organic amine compound as the activator. By using orthogonal and comparison methods to design experiments, determine the activator composition and dosage through the spreading rate experiments. Three kinds of non-ionic surface active agents of the Span-20Tween-20and OP-10were ultimately selected from a variety of surfactants.. By using orthogonal experiments to design experiments, and determine the composition of the surfactant by the spreading rate. The best formula of the flux is that the ratio of activator is5.03%, the proportion of the non-ionic surfactant is0.2%,, the ratio of the corrosion inhibitor0.01%, the ratio of other auxiliary components1.5%, the ratio of the deionized water is93.26%.(2) The halogen-free water-based VOC-free flux was tested comprehensively, the results showed that the properties of the flux has been reached the standards in the aspects of appearance, such as the halogen content, the physical stability, the acidity and the copper corrosive. The results of the actual welding experiments, with the Sn-3.0Ag-0.5Cu lead-free solder, shows that the spot was bright and full, the welding residue was little, the spreading rate was up to78.2%. Compared the comprehensive performance with the common goods of fluxes, our self-made flux was better, and it can be used for the manual welding and wave soldering process of the lead-free solders.