Dendritic Growth at Constant Voltage Between Electrodes Coated by SnBiAg, SAC, SnCu and SnPb Solder

In this work, dendritic growth between electrodes coated by Sn42Bi57Ag1, SAC 305, Sn99.3Cu0.7 and Sn63Pb37 Solder was studied. The water drop test method with a 0.02 ‰ concentration of NaCl dissolved in the deionized and purified water was used to support the growth of dendrites on the samples corresponding to the IPC-B-24 standard. The dendritic growth was induced under the constant low voltage DC bias (1.5 V) between the electrodes and the results between different alloys were compared. The solder alloys electro-chemical migration resistance was compared with respect to their Tin content, however the low temperature solder paste with 42wt% tin content showed similar results as the solder alloy with 99.3wt% of Tin. The change of surface insulation resistance (SIR) in time during the dendritic growth was observed. The dendrites were subjected to an EDX analysis on the electron microscope and the fern dendrite structure material analysis was conducted.