Some problems in lead-free assembly process of the miniature and large components on PCB

Some electronic assemblers are faced with the necessity to use heterogeneous assembly of both very large and very small components on the same board and use lead-free materials in soldering processes according to the the EU RoHS Directive (on the restrictions of the use of certain hazardous substances in electrical and electronic equipment). The implementation of lead-free pastes, PCB surface finishes and termination of components can generate a big impact on the mounting process and potentially on solder joints quality. Mainly it is caused by differences in a melting temperature, wetting characteristics and self-centering capability of lead-free alloy in comparison to tin lead materials. Some surface mount defects can arise especially for assembly of different types and sizes components also miniature one onto the PC board. From 1999, ITR has assisted Polish companies in transition to environmental friendly technologies of PCB production and mounting technologies. In the paper the results of investigation on lead-free technologies carried out during the UE project GreenRoSE as well as national projects are presented.