Along with the shift to lead-free products, the number of lead plating, solder, and other materials is increasing, and ion migration risks occurring in solder joints. The results of ion migration evaluation of various combinations of lead material, solder plating, and solder paste are shown below.
It was confirmed that no ion migration occurs with any of the combinations.

<Evaluation conditions>     • Package: 28 x 28mm, 208 pin QFP, 0.5mm pitch     • Printed wiring board: 125 x 125 x t1.6mm, FR-4, 4 layers        Wiring pattern as shown in figure below     • Flux: RMA type     • Cleaning after soldering: Non     • Temperature, humidity: 85°C, 85%     • Applied voltage: 50 V     • Judgment criterion of failure: Defective when 100 K or less