Dendritic Growth and its Dependence on Various Conditions

Printed circuit board (PCB) as a basic supporting structure of electronic devices is a significant reliability factor in electronic manufacturing. The miniaturization in electronics leads to lower gaps between pads with different electrical potential and that increases the probability of fault caused by dendritic growth. Not just the ambient environment has influence on electrochemical migration, but the surface finish, the solder mask, used solder and the cleaning process influences the dendritic growth and its composition and thus the reliability of PCBs and the final product. The results indicate, that the use of suitable soldering mask without any doubt hinders, though not fully the dendritic growth. An unexpected result is that the dendritic growth was also hindered when the flux residues were present. The lowest resistance against dendritic growth was discovered with organic solderability preservatives (OSP) surface finish, the highest with electroless nickel immersion gold (ENIG). The element analysis showed that the dendrites do not grow directly from the soldering pads. The surface finish therefore does not have a direct influence on dendrites, but rather on the chemical compound that is formed between the surface finish and the solder. These compounds are then prone to electrochemical migration.