Incorrect Material Set
One of the more common mistakes that is still occurring today is the preference to specify a High Glass Transition Tg laminate material over a high decomposition temperature Td laminate material for RoHS compliant applications. This is done inadvertently in the belief that the higher Tg material will somehow survive better the increased assembly temperatures associated with Pb-free assembly. A high Tg material can still have a low decomposition temperature that may be below the peak reflow temperatures. This can result in catastrophic internal damage to the PWB that may be seen during assembly or else is returned as a field failure.