Here is some interesting information on the topic lead free soldering. This information originates from a specialist on soldering of a big international distributor.

• Unlike with leaded solder you need to be very careful how to solder and what materials you use. Lead free oldering is much more challanging and error-prone.
• For lead free soldering you should use a soldering station with at least 80 W. Addionally the soldering temparature should be adjustable.
• Lead free solder has a higher melting point as leaded solder. During the soldering there are continuous temperature drop, e.g. caused by contact with the cold solder or the cold printed circuit board (PCB). Thats why you should use a soldering tip as short as possible and as wide as possible. That ensures that the temparature drops are quite small.
• If the soldering tip is to hot the flux contained in the solder will burn up. Thats why you should set the temparature of the soldering station about 140 Kelvin higher than the melting poind of the solder.
• If the solder contains less than 1% of flux you should add flux.
• The soldering tip is best cleand with a dry cleaner and not with a wet sponge. After cleaning the tip you should apply solder to it immidiately.
• If you want to use a sponge you should use only demineralized water and wring it, so that the sponge is only moist not wet. The wetness of the sponge causes temparature drop on the top that lead to tiny cracks that eventually will destroy the tip.
• A special cleaner should only be used if the tip is very worn and no good soldering results are possible. After using the special cleaner immediatally apply solder to the tip to prevent corroding of the tip.