stay brite is the only low temp solder i know of aproved for refrigerant lines and should be used with stay clean flux. their may be others but havent heard of any yet
you dont need nito because the melting point is low and flaking does not ocure. very little flux is needed and works well. by memorie it will hold 10,000 lb and hell i forget the vibrations. compressors should be brazed but have seen very few dummies solder them to
if nitrogen is flowed with staybrite the solder will be pushed out and not alowed to flow into the fitting properly