Originally Posted by flying-llama
As far as I know:
if it has a "RoHS" marking (and it seems most electronics boards do these days), then lead-free solder was used to put it together.
Lead-free solder and leaded solder (like 60/40 rosin-core solder) are supposed to make an unusable mess when mixed, so it is best to use lead-free solder when dealing with an "RoHS" board (I have both types of solder).
From experience, I believe this is correct. In fact, you'd be best off not even using the same soldering iron that has been tinned with the leaded solder, when working lead-free solder joints.