Electromigration behavior of the Cu/Au/SnAgCu/Cu solder combination

Abstract

The electromigration behavior of the Cu/Au/SnAgCu/Cu combination was investigated under 103 A/cm2 of current stressing at ambient temperature. The Au layer, when it acts as a cathode, was consumed continuously, and no significant compound was found at the interface. Meanwhile, Cu6Sn5 was formed at the anodic Cu layer, and the thickness of the compound increased with increasing time. The Au atoms were found to be trapped in Cu6Sn5 within the solder matrix. The AuSn4 compound precipitated while attaching to Cu6Sn5 at the Cu6Sn5/solder interface. The thermomigration effect was found to be insignificant in this work as no obvious reaction occurred at the cathode/anode sides or in the solder matrix without current stressing.

The difference in the types of intermetallic compound formed between the cathode and anode of an Sn–Ag–Cu solder joint under current stressing

“…6(b) tells that interfacial AuSn 4 was only observed for the current stressing specimen. The migration of Sn from the solder toward the anode upon current stressing was a reasonable explanation in our previous study [11]. According to Eq.…”

“…This occurrence implies an insignificant effect of chemical potential, and thus the parameter of J CP in Eq. (11) for Cu can be neglected; only J EM was considered for the consumption of Cu under current stressing. As a result, the total flux of Cu was approximately equal to that induced by EM (J total Cu z J EM Cu ).…”

“…(11), the atomic flux of Sn at the anode side was induced by the concentration gradient and EM (J CP Sn þ J EM Sn ). This resulted in a large amount of Sn migrating toward the anode and reacting with Au to form interfacial AuSn 4 during 120 h of current stressing [11]. The dissolution behavior of interfacial AuSn 4 was monitored for a long time of current stressing ( Fig.…”

“…Au-containing IMC may influence the mechanical properties or solder reliability. However, few studies have investigated the effects of EM between Au and solder [11]. The present study investigates the kinetics of cathodic reactions and microstructural evolution of a Cu/SnAgCu/Au/Cu joint under various current densities.…”

Effects of Electromigration on Interfacial Reactions in the Ni/Sn-Zn/Cu Solder Interconnect

“…Recently Chiu and Lin reported that the Au layer was consumed continuously in the Au/Sn-Ag-Cu/Cu solder combination when the electrons traveled from the Au side to the Cu side, and no microstructure evolution was found in the reverse direction of electron flow. 13 Other researchers also found that current-crowdinginduced electromigration failure would happen at the Cu side with electrons flowing from the Cu side to the Ni side, while the joint with electrons flowing from the Ni side to the Cu side survived the current stressing. [8][9][10][11] Chen and coworkers 14,15 investigated the electromigration effect upon the Sn/Cu, Sn/Ni, and Ni/Zn interfacial reactions and found the passage of electric current only had notable effect upon the Sn/Ni interfacial reactions.…”