SMTA International Conference Proceedings


FLUX SELECTION FOR LEAD-FREE WAVE SOLDERING

Authors: Douglas Watson, Jasbir Bath, Pan Wei Chi
Company: Solectron Corporation
Date Published: 10/11/2007   Conference: SMTA International


Abstract: A Design of Experiment (DoE) was performed to determine the best wave solder flux types for lead-free wave soldering, best available flux within each type, and to clarify the process limits for each type of flux. The 0.125” (3.2mm) thick OSP test vehicle board encompassed a wide range of through-hole characteristics from multiple copper planes, variable barrel diameters and component types and orientations to demonstrate the limits of wave process capability. The fluxes selected also covered a wide range of flux chemistries.

The design of experiment varied topside board preheat and conveyor speed. The solder qualities evaluated included vertical barrel fill, solder bridges, bottom side wave soldered surface mount device solder skips, and solder balls. General conclusions were drawn from statistical analysis of the solder quality to correlate improved results with optimum preheat, conveyor speed and, by correlation, solder contact time. This helped to clarify the different limits of liquid flux types used for lead-free SnAgCu wave soldering compared with tin-lead wave soldering, with gaps identified for future work by wave flux suppliers and board designers.

Key words: Flux, Pb-free, wave solder



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