Scott,

For wave soldering, if the lead-free alloy is one with a high tendency to
generate dross, e.g. the Sn-Ag-Cu alloys, then a nitrogen atmosphere, full or
just over the wave, is worthwhile to reduce solder loss.

Otherwise the nitrogen is needed not so much for the sake of the solder but
for protection of an OSP finish or the flux system from degradation by the
generally greater temperature and overall greater heat input to the process
(longer times).

Japanese experience, where fairly robust high solids fluxing systems are
still used is that nitrogen is generally not needed.   Whether nitrogen will be a
permanent feature of lead-free soldering when minimal residue flux systems are
used will depend on how robust the manufacturers can make these flux systems.

Keith Sweatman
Nihon Superior Co., Ltd

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