Poor solderability on printed boards may be seen more often with nickel gold and copper boards. They are a relatively new coating to assembly and some PCB manufacturers and care needs to be taken during their introduction and use.

In the example it is clear that the copper pad is not solderable as all the solder paste has reflowed to form a solder ball on the pad surface. Poor solderability on copper boards may be caused by ageing, poor handling, washing the board, excessive reflow temperature or it may have been poor when supplied.