The two biggest problems I've seen with lead-free solder are the difficulty in distinguishing a good joint from a cold one and also the higher temperature needed to melt it. I was fascinated by a problem I had in a car once. I had owned the car since it was new and after 11 years the heater control started behaving erratically. I took it apart and found eventually that the problem was a bad or broken solder joint on a 1206 size resistor in the power supply which fed the microcontroller (a PIC interestingly ). It amazed me that this would only appear after 11 years and was not on a large component which was subject to vibration. The joint was not visibly cracked - I suppose it is possible that part of the end termination of the resistor was bad - my recollection is that simply re-heating and adding solder fixed it. Sean On Dec 6, 2015 5:25 PM, wrote: > > I don't believe the difference is in the mechanical bond. I believe tin > was > > originally used but lead had to be added to prevent "whiskering" which > > caused problems even in the old circuits. > > Yes, whiskers are a real problem with pure tin, they grow in seconds - > really - I have seen real time videos of them growing and the speed at > which they grow is astonishing. > > SMD solders use silver and other metals as part of the alloy to stop > whiskers (as well as stop silver leaching from terminations). Apparently = it > doesn't need a lot of other metal in the alloy to stop whiskers. > > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .