Electromigration induced ductile-to-brittle transition in lead-free solder joints

Abstract

The effect of electromigration on ductile-to-brittle transition in flip chip solder joints has been studied using one-dimensional bamboo-type samples of eutectic 95.5Sn–3.8Ag–0.7Cu solder joined by Cu wires at two ends. Both electrical current and tensile stress were applied to the samples either in serial or in parallel. In serial tests, the strain rate was 6×10−3. In parallel test, the creep stress was 7MPa. The current density applied was (1–5)×103A∕cm2. The working temperature was 100–150°C. In both tests, the authors observed the ductile-to-brittle transition in which the fracture migrates from the middle to the cathode interface of the joint with increasing current density and time. The transition is explained by the polarity effect of electromigration, especially the accumulation of vacancies at the cathode interface.

Reduction of electromigration damage in SAC305 solder joints by adding Ni nanoparticles through flux doping

“…On the other hand, directional migration of Cu atoms toward the anode side creates vacancy, cracks, and voids at the cathode side [9]. Serrated cathode dissolution phenomenon [24] can be seen in Fig. 3d.…”

“…Gradually, Cu atoms begin to form a thicker layer of IMCs such as Cu 6 Sn 5 at anode side by reacting with Sn atoms [23]. If IMCs become thicker, it could reduce the mechanical reliability of solder joint because of the brittleness of the IMC [24]. On the other hand, directional migration of Cu atoms toward the anode side creates vacancy, cracks, and voids at the cathode side [9].…”

Nanostructure–property relations for phase‐change random access memory (PCRAM) line cells

“…[10], a current density of 10 6 A cm À2 was sufficient to melt much larger sized Ge 2 Sb 2 Te 5 lines and when this current density was continuously maintained during a few milliseconds breakage of the line due to electromigration occurred. Typical current density values for electromigration are indeed 10 6 -10 7 A cm À2 for Al or Cu metallization lines and can be even as low as 10 4 A cm À2 for solder joints [11]. Therefore, it is remarkable that the line cells can still be switched typically 10 7 times with our high current densities of 10 8 A cm À2 .…”

Effect of Intermetallic on Electromigration and Atomic Diffusion in Cu/SnAg3.0Cu0.5/Cu Joints: Experimental and First-Principles Study

“…1. After that, a simple low-cost rectangle groove method, which is similar to the V-groove method proposed by Tu et al, 11 was used to fabricate our solder joints. First, a rectangle groove of 150 lm in width was etched on a glass surface or constructed by piling up three pieces of glass with clean surfaces.…”