Kester R500 is a water-soluble solder paste formula specifically designed as a consistent dot dispensing paste for automated dispense equipment. This solder paste exhibits excellent wetting characteristics in a wide range of profiles. The activator package in this formula is extremely aggressive. It is active enough to remove tenacious oxide layers or to solder to OSP coated boards. R500 is a water-soluble formula that maintains its activity and tackiness characteristics for up to 8 hours.