Fractal Description of Dendrite Growing During Electrochemical Migration

The electrochemical migration (ECM) is an important physical-chemical failure mechanism which limits the realization of fine pitch structures in the manufacturing technology of printed wiring boards (PWB). The cause of ECM is the material transport that leads to dendrite formation. Electrical shorts will grow between pads or leads in fine pitch applications. The mechanism of ECM can be described by electrochemical principles. Dendrites are treatable as a fractal phenomenon because these special formations are in accordance with the most significant criteria of the fractal theory. We have observed in pursuance of our experiment-series that there is relationship between the materials of selective surface finishes of printed wiring boards, mean time to failure (MTTF) done to the migration process and the shape and form of dendrites grown on the top of the substrates in lateral arrangement. If the result of failure analysis is shortage caused by ECM in form of dendrite structure then it is worth to examine the shape and form of dendrites. According to our conclusion the reason of failure can be found with simply and cheap methods and the most efficient protection can be applied if we apply the above-mentioned relationship.