Kester 1630 is a water-soluble liquid flux for heat sink applications. It is a bromide based, chloride-free, inorganic salt activated flux containing less than 1% free of acid. 1630 is an excellent flux for soldering copper, brass and all types of tin-based solders from low tin to lead-free solders. - 1630 has a bromide activator that will not turn copper or brass green during normal soldering operations. 1630 is also used for soldering nickel and mild steel. 1630 was developed for soldering electrical connections like fuses, and can be used to solder all copper based alloy joints. The inorganic salt activation system gives 1630 great heat stability over a long period of time using a wide variety of heating techniques.