Break-up Process of Perturbed Molten Metal Jet and Preparation of Lead-Free Solder Balls

摘要

Solder balls, which are used in advanced electronics packages such as BGA (Ball Grid Array) and CSP (Chip Scale Package) to substitute the leads and realize the electrical and mechanical connections between substrate and chip, have severe specifications in diameter tolerance, roundness and surface quality, and therefore challenge the traditional technologies for fabrication of metallic particles and powders. The present work made a survey of perturbed molten metal jet break-up process, observed the formation and growth of capillary wave of tin-lead melt jet by way of rapid solidification, and on the basis of the above research, successfully obtained tin-lead eutectic and Sn-4.0Ag-0.5Cu lead free solder balls with tight distribution and good sphericity of particles through optimization of processing parameters, forming a solid base for cost effectively producing solder balls.