Influence of corrosion properties on electrochemical migration susceptibility of SnPb solders for PCBs

Abstract

Electrochemical migration is caused by the adsorption of water and the bias voltages between the electrodes or pads which form an electric circuit or in the solders used to connect the parts. This work focused on the elucidation of the mechanisms of electrochemical migration of pure Sn, Sn37Pb, and Sn55Pb solders in electronics. The electrochemical migration behavior was discussed on the basis of the polarization behavior of SnPb solders. After the water drop test, the time to failure decreased with increasing Pb content in Cl solution and increased with increasing Pb content in SO 4 2 solution. In the case of the SnPb solder alloys, the pitting potential, the passive current density, the cathodic current density and the efficiency of cathodic deposition of the alloying elements were closely related to the resistance of the electrochemical migration.

Electrochemical Migration on Electronic Chip Resistors in Chloride Environments

“…Yoo and Kim [28] have investigated the influence of varying Pb content on ECM using NaCl and Na 2 SO 4 solutions (all neutral pH conditions). In Na 2 SO 4 , the tendency for ECM is seen to decrease due to passivation of Pb, while in NaCl solution, no significant change in the tendency for ECM is observed when the Pb content is increased.…”

“…Noh and Jung [1] found that ECM migration is more likely to occur on a glass-epoxy FR-4 (flame resistant-4) PCB than on a polyimide PCB. Yoo and Kim [28] investigated the influence of the corrosion properties on ECM in varying Pb concentrations. Sample preparation was done by applying a solder paste of varying Pb content onto a silicon wafer and passing it through a reflow oven.…”

Electrochemical migration of Sn and Sn solder alloys: a review

“…This was ascribed to that a passive layer on Sn surface could be formed in NaCl solution, but not for Pb. Yoo et al 62,67 also found that the time-to-failure of Sn-Pb solder alloys decreased with increasing Pb content in chloridecontaining solution.…”

“…Lee et al and Yoo et al [60][61][62]67 performed respectively a series of ECM experiments of Pb, Sn and Sn-Pb solder alloys in sulfate-containing solution. They found that the time-to-failure increased with increasing Pb content, indicating that the addition of Pb increased the ECM resistance of Sn-Pb solder alloys in sulfate-containing solution.…”

“…According to the literature, three main environments were used including pure water or distilled water, 78,81 chloride-containing solution [60][61][62][63][64]67,68 and sulfate-containing containing solution. [61][62][63]67 It can be summarized that the time-to-failure which is proportional to the ECM resistance of Sn-Pb solder alloys decreases with increasing Pb content in a pure water or chloride-containing solution, whereas it increases with increasing Pb content in sulfate-containing solution. A few examples are given below.…”