by Mario Scalzo , Todd O'Neil
Although many predicted the demise of through-hole components, they are alive and well with tens of billions used each year. In mixed SMT/through-hole PCBs, through-hole components, and especially connectors, are often used for their mechanical robustness. A typical example would be a USB connector in a laptop PC. Typically an SMT connection just doesn't have the mechanical robustness needed to support multiple connector plug-in and removals. However, performing a full wave soldering process to assemble a few through-hole components on a mostly SMT PCB doesn't usually make economic sense and may damage the PCB. In such situations, the best option is often to assemble the through-hole components and connectors with a selective soldering process.
This paper touches on identifying favorable flux properties, down-selecting low solids fluxes for lead-free selective wave soldering, the selective soldering process itself, and testing criteria. Topics reviewed will be the flux selection, optimizing the selective soldering process by varying the flux concentration, pre-heat parameters, soldering temperatures, and dwell time. The paper will finish with a summary of the work and a systematic process to select a flux and optimize the selective soldering process for high yields and quality.
flux, pb-free, lead-free, selective soldering, SMT, through-hole, PCB assembly, Apex 2011
[Permanent Link to this Paper ]
Posted on 11 Apr 2011
