(a) Cross-sectional micrograph showing a typical serrated interface due to excessive cathode dissolution. This joint is stressed with a current density of 4.5 × 104 A/cm2 at 50 °C for 1000 h. The electrons flow upward. (b) Schematic illustration showing one of the possible three-dimensional morphologies: rod-like dissolution. (c) Schematic illustration showing another possible three-dimensional morphology: thin-plate dissolution.
(a) Schematic drawing showing the flip chip solder joint used in this study. (b) Micrograph showing the as-assembly joint before current stressing.
Schematic drawing showing the temperature control setup used in this study.
Micrograph showing a joint that has been stressed with 4.5 × 104 A/cm2 at 50 °C for 1500 h.
(a) Schematic illustration showing the layer-by-layer polishing used in this study. (b) Drawing the relation between the distance to center line, d,and the width of the opening of a cross section, w.
(a)–(h) Cross-sections of the same joint that has been stressed with 4.5 × 104 A/cm2 at 50 °C for 1500 h. These eight cross sections are from the same joint but with different d values. Electrons entered the joint from the lower side and exited through the upper side.
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