Study on Electromigration Effects and IMC Formation on Cu–Sn Films Due to Current Stress and Temperature

Abstract

In this study, the effects of electromigration on a solder/copper substrate due to temperature and current density stress were investigated. The copper–tin (Cu–Sn) film samples were subjected under a fixed current and various heating conditions (130 °C and 180 °C) and current densities (different cross-sectional areas). The micro-structural changes and intermetallic compound (IMC) formation were observed, and failure phenomena (brittle cracks, voids, bumps, etc.) on the structures of samples were discussed. The results showed that the IMC thickness increased as the temperature and current density increased. Moreover, it was found that the higher the temperature and current density was, the greater the defects that were observed. By adjusting the designs of sample structures, the stress from the current density can be decreased, resulting in reduced failure phenomena, such as signal delay, distortion, and short circuiting after long-term use of the material components. A detailed IMC growth mechanism and defect formation were also closely studied and discussed.

Solid-Solution or Intermetallic Compounds: Phase Dependence of the Li-Alloying Reactions for Li-Metal Batteries

“…We consider here the movement of the Li and M atoms during an electrochemical cycle. From the point of view of a thermodynamically driven atomic diffusion, atom migration into a metal alloy is dependent on the chemical potential gradient, as described by eq . J i = prefix− D ∂ μ i ∂ x where J i is the transfer rate of species i , D is the average diffusion coefficient, x is the distance from the bulk phase to alloy surface, and ∂ μ i ∂ x is the chemical potential gradient. In the following, we discuss the transfer of species according to (i) the D of the different alloy systems considered and (ii) the variation in chemical potential of the different species.…”

“…We consider here the movement of the Li and M atoms during an electrochemical cycle. From the point of view of a thermodynamically driven atomic diffusion, atom migration into a metal alloy is dependent on the chemical potential gradient, 34 as described by eq 1.…”

Interfacial intermetallic compound modification to extend the electromigration lifetime of copper pillar joints

“…This means that higher current densities and temperature may occur in the solder joints, giving rise to EM. Thus, EM has become a more and more important indicator of joints reliability, which will determine the lifetime of the service time of electronic products (Song et al, 2020;Wang et al, 2020;Yue et al, 2021). In addition, copper pillar bump needs to be joined to pad by Sn96.5Ag3.5 solder in industry, and intermetallic compound (IMC) is formed through the interfacial reaction between solder and surface-finishing pad material during joining process (Mokhtar et al, 2021) , (Xu et al, 2022).…”