Study Of Composition And Properties For Four Kinds Of No-Clean Solder Paste

With the development of electronic industry and the importance placed to environment protection, no-clean solder paste has been paid much attention and used in electronic industry, owing to its characteristics such as less leftover, feebleness corruption and free of cleanout after reflow soldering. In this paper, soldering micro-powder and no-clean flux which compose no-clean solder paste and four kinds of no-clean solder paste were studied. The properties of Sn37Pb and Sn3Ag2.8Cu soldering micro-powder prepared by atomization were analyzed. The compositions of three kinds of no-clean flux were optimized by orthogonal experiment, and their properties were tested according to industry standards and were compared with homemade flux. Every kind of prepared flux was mixed with Sn37Pb soldering micro-powder or Sn3Ag2.8Cu lead-free micro-powder separately to prepare four kinds of no-clean solder paste, then studied the properties and contrasted with homemade no-clean solder paste. The main results are as following:(1) The biggest throughput of pilot atomization system is 400g/time. Sn3Ag2.8Cu and Sn37Pb soldering micro-powder prepared under this condition can meet the demand of soldering powder for solder paste.(2) The test of anti-oxidizing surface treatment showed that benzotriazole(BTA) can effectively mitigates the oxidation of Sn3Ag2.8Cu and Sn37Pb soldering micro-powder in air.(3) No-colophony no-clean flux, low-colophony no-clean flux A and low-colophony no-clean flux B were prepared with excellent properties by selecting different mixed organic acids as activator.(4) No-colophony no-clean SnPb solder paste, low-colophony no-clean SnPb solder paste A, low-colophony no-clean SnPb solder paste B and low-colophony no-clean lead-free solder paste B, whose solder ball and wetness assess grade were 1 stage, were prepared by mixing each of the three kinds of no-clean flux with Sn37Pb soldering micro-powder or Sn3Ag2.gCu lead-free micro-powder respectively. All of the three solder pastes could form plump and splendid solder point, and no taulty soldering. The leftover of these no-clean solder paste were infinitesimal. These no-clean solder paste had excellent spread and wetness performance. The growth rate of these no-clean solder pastes were 85% upwards after reflow soldering.(5) By the observation of soldering interface, the IMC of Sn-Pb based solder paste was thinner than that of Sn3Ag2.8Cu lead-free solder paste. Cu3Sn layer mainly formed and grew up during aging. The best reflow soldering process parameters of these four no-clean solder pastes were optimized.