Alpha NR-205 is a halide-free, rosin/resin free, low solids, no-clean flux. It is formulated for wave soldering of through-hole, mixed technology and surface mount assemblies. The flux is particularly effective when soldering in an inert atmosphere. The flux produces a tack-free surface with high surface insulation resistance and very little residue to interfere with electrical testing. Alpha NR-205 fully conforms to the requirements of Bellcore TR-NWT-000078. The flux has been specifically formulated to resist degradation in surface insulation resistance and electromigration, even in situations where the flux does not experience soldering temperatures and when heavy levels of flux have been applied. The residues are non-corrosive and do not cause “greening” when in contact with copper or copper-bearing alloys. Alpha NR-205 is particularly well-suited for touch-up/rework when supplied in a flux pen.