Development of Pb-Free Nanocomposite Solder Alloys

Animesh Basak,Hamidreza Riazi,Alokesh Pramanik,Angus Netting,Mahyar Silakhori

doi:10.3390/jcs2020028

Abstract

As an alternative to conventional Pb-containing solder material, Sn–Ag–Cu (SAC) based alloys are at the forefront despite limitations associated with relatively poor strength and coarsening of grains/intermetallic compounds (IMCs) during aging/reflow. Accordingly, this study examines the improvement of properties of SAC alloys by incorporating nanoparticles in it. Two different types of nanoparticles were added in monolithic SAC alloy: (1) Al2O3 or (2) Fe and their effect on microstructure and thermal properties were investigated. Addition of Fe nanoparticles leads to the formation of FeSn2 IMCs alongside Ag3Sn and Cu6Sn5 from monolithic SAC alloy. Addition of Al2O3 nano-particles do not contribute to phase formation, however, remains dispersed along primary β-Sn grain boundaries and act as a grain refiner. As the addition of either Fe or Al2O3 nano-particles do not make any significant effect on thermal behavior, these reinforced nanocomposites are foreseen to provide better mechanical characteristics with respect to conventional monolithic SAC solder alloys.

Highlights

The expansion of electronic packaging system in the context of miniaturization requires a number of factors to be taken into consideration such as wafer design, resist system, metal deposition techniques etc
The applicability of a solder alloy is attributed to its resistance under low cycle thermal fatigue which is governed by its underlying microstructure
This temperature difference took place over a very narrow range, i.e., between 220 ◦C and 230 ◦C. This confirms that the addition of nanoparticles in monolithic SAC solder alloy retain the melting temperature in desired range, which is suitable for their intended applications [25,26]

Summary

Introduction

The expansion of electronic packaging system in the context of miniaturization requires a number of factors to be taken into consideration such as wafer design, resist system, metal deposition techniques etc. Single grained Sn joint in solder fails to balance repeated thermal stress, near eutectic SAC at 80 ◦C underwent cyclic growth twinning all through solidification process [9] Reflowing of such SAC based solder on Cu substrate cause coarsening effect of IMCs and degrade mechanical properties. Recent investigations on nanoparticles reinforced Al-matrix composite exhibits superior mechanical properties of materials [10] in terms of limiting grain growth, strength and avoid grain coarsening. Among these reinforcing elements NiO [11], Al2O3 [12], TiO2 [13], pure elements such as Ni, Fe, Bi [14,15] and even rare earth elements has been reported [16] to extent its mechanical properties further without compromising thermal behavior. An experimental based approach was adopted to make fundamental understating and further development of durable Pb-free solder nanocomposites

Materials

Different Phases of Solder Alloys

Findings

Conclusions