Black pad phenomenon is found to be one of the major failures occurring in electroless nickel immersion gold (ENIG) printed circuit boards finishes. It is believed to be caused on the Au/Ni-P finish production level but the reliability problem appears in the final product. So far several pointers were given to overcome it, however there are still some unclearness. Therefore, complex scanning and transmission electron microscopy examination have been undertaken to reveal the black pad occurrence on ENIG finishes either unsoldered or covered by PbSn solder.
Acknowledgments
This work has been supported by the Polish Governmental funds and structural funds of EC under Project No UDA-POIG.01.03.01-00-103/09-00 “The improvement of reliability of lead-free solder joints in electronic devices”.