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Since lead-free soldering is initiated in the electronic industry in 1st of July 2006, studying the behaviour of lead-free solders in depth is more important than ever. The small chip components of present day demand for very accurate component placement machines, in order to prevent common reflow failures such as skewing or tombstoning. The ability of components to be self-aligned during soldering works against these failures, therefore it matters to what extent the solder promote this effect. Dynamic behaviour of SMT (surface mount technology) chip components during lead-free reflow soldering is demonstrated in the paper, especially focusing on movement. A force model is given by the virtue of the four forces, which have effect on the chip during reflow soldering, namely: the force originating from hydrostatic and capillary pressure, the force of gravity, the force of dynamic friction and the force originating from the surface tension. The self-alignment of 0603 size chip components has been investigated in our experiment. The experiments were carried out using lasercut stainless steel stencil and SAC305 type lead-free solder paste. The results have shown that the self-alignment of components does occur even in the case of 400-500 mum misplacements.
Date of Conference: 9-13 May 2007