The Improvement Of The Solder Paste Performance And The Effect Of Composition On It

FLY905 lead-free solder paste is the first production from Yikst soldering producer following lead free tendency. Its performance has many defects, such as poor wettability, difficult for printing, slumping and drying easily, as well as limited storage period, all of that bring some defects such as poor solderability, solder balls, bridging, pseudo soldering and tombstoning, etc. Those defects has great influence on the quality of reflowing solder joints, therefore, it results in the decrease of finished product rate. With the purpose of improving the performance of FLY905, this paper on the foundation of realizing the deficiency of FLY905 studied the reason that the component of the flux affect the solder paste, tested the performance of the improved solder pastes and contrasted with the original one.By adding cationic surfactant to improve the wettability of Lead-free solder paste, the results of selecting and optimizing are: two different kind of cationic surfactant can coordinate with each other to improve the wettability; and when the proportion of oleic acid ammonium salt is 0.5% and that of F-alkyl carboxylate surfactant is 1%, the wettability of solder paste is best, because the former can increase the surface energy of Cu pad and the latter can improve the activity of the active functional group forming flux.By adjusting the proportion of solder powder and flux for improving the printing performance of Lead-free solder paste, the results shows that when the proportion of solder powder is 88.5% and 89.0%, the solder pastes were printed nicely. The studying on rheological performance of solder paste indicated that the viscosity and thixotropy index of solder paste determine the printing performance when just considering the capability of solder paste itself. Concretely, when the viscosity and thixotropy index of solder paste are in the appropriate scale, the solder paste could be printed well.The other components of flux have been adjusted and the producing process has been meliorated. In this paper the author has carved up the main part, the active part and the accessorial part; and also chose two kinds of solvent to replace single solvent to enhance polarity and dissolving capacity. This paper...