Slightly higher percentage of tin compared with the classic 60/40. This allows for a lower melting point making soldering, and especially desoldering less risky for your gear. In other words, the less time your soldering tip is applied onto a PCB,(be it a FC, an ESC or a RX), the less the whole PCB will heat up. This means fewer chances of overheating PCBs and other sensible electronic equipment.
If that was not enough, Armattan uses non-corrosive and non-conductive rosin core so that you never have to use flux again.