One standard increasingly used (e.g. in the United States) is J-STD-004. It is very similar to DIN EN 61190-1-1.
Four characters (two letters, then one letter, and last a number) represent flux composition, flux activity, and whether activators include halides:
* First two letters: Base
** RO: rosin
** RE: resin
** OR: organic
** IN: inorganic
* Third letter: Activity
** L: low
** M: moderate
** H: high
* Number: Halide content
** 0: less than 0.05% in weight (“halide-free”)
** 1: halide content depends on activity:
*** less than 0.5% for low activity
*** 0.5% to 2.0% for moderate activity
*** greater than 2.0% for high activity
Any combination is possible, e.g. ROL0, REM1 or ORH0.
J-STD-004 characterizes the flux by reliability of residue from a surface insulation resistance (SIR) and electromigration standpoint. It includes tests for electromigration and surface insulation resistance (which must be greater than 100 MΩ after 168 hours at elevated temperature and humidity with a DC bias applied).