Hi,  In the process of using the new lead free solder so that the RoboGuts™ circuit boards are 100% RoHS compliant I found out that the soldering pen tips wear out about 100x faster than when using lead.  

I've gone though trying several different soldering pens and after a little research online I find that it's the reactions during the soldering that cause the iron on the tips to move into the soldering joint.