Intermetallic Evolution of Sn-3.5Ag-1.0Cu-0.1Zn/Cu Interface under Thermal Aging

Abstract

Due to environmental concerns, lead-free solders were introduced in replacing the lead-based solders in microelectronics devices technology. Although there are many lead-free solder available, the Sn-Ag-Cu is considered the best choice. But the solder has its draw backs in terms of melting temperature and intermetallic formations. To improve the solder, a fourth element Zn was added into the solder. The new composite solders were synthesized via powder metallurgy route. This research studies the effect of 0.1wt% Zn addition on the hardness and intermetallic formation on Cu substrate. For the hardness results, the micro Vickers values were reported. For intermetallic, the solders were melted at 250°C and aged at 150°C until 400 hours. The microhardness value for Zn based composites solder shows higher micro Vickers hardness compared to un-doped counterparts. The phases formed and its growth was studied under SEM and by energy dispensive x-ray (EDX). The SEM results show the presence of Cu6Sn5and Cu3Sn intermetallics and the Cu5Zn8intermetallic was not detected. The addition of 0.1wt% Zn has retarded the growth of the Cu3Sn intermetallic but not the total intermetallic thickness.

Influence of nanoparticle addition on the formation and growth of intermetallic compounds (IMCs) in Cu/Sn–Ag–Cu/Cu solder joint during different thermal conditions

“…Amagai [23] and Yahya et al [90] reported that by adding 0.05 and 0.1 wt% of Zn nanoparticles in the solder joint did not introduce any effect on the IMC layer thickness and grain size even after thermal cycling and thermal aging. When the addition amount increased to 1 wt%, a Cu 6 Sn 5 IMC layer is observed but its thickness is thinner than that of the Zn-free solder joint [87].…”