Interfacial reactions between Sn‐Cu based multicomponent solders and Ni substrates during soldering and aging

Abstract

Purpose

The paper aims to investigate the interfacial reactions between two Sn‐Cu based multicomponent Pb‐free solders, Sn‐2Cu‐0.5Ni and Sn‐2Cu‐0.5Ni‐0.5Au (wt per cent), and Ni substrates during soldering and aging.

Design/methodology/approach

Differential scanning calorimetry (DSC) was performed to measure the melting behaviors of the solders and determine the temperature of soldering. DSC tests showed that the onset temperature were 227.47 and 224.787°C for Sn‐2Cu‐0.5Ni and Sn‐2Cu‐0.5Ni‐0.5Au, respectively. Two intermetallic compounds (IMCs), Cu₆Sn₅ and (Cu,Ni)₆Sn₅, were formed in Sn‐2Cu‐0.5Ni solder. While the IMCs detected in Sn‐2Cu‐0.5Ni‐0.5Au matrix were (Cu,Ni)₆Sn₅, (Cu,Au)₆Sn₅ and (Cu,Ni)₆Sn₅. The IMC layer formed at the both solder/Ni interfaces was (Cu,Ni)₆Sn₅ with stick‐lick morphology after soldering at 260°C.

Findings

The interfacial IMC layers became planar when aged at 170°C for 500 h. However, cracks were found in the IMC layers at both joints when the aging time reached 1,000 h, that implies reliability problem may exist in the joints. Moreover, Au‐containing IMCs were found on the top of the IMC layer in Sn‐2Cu‐0.5Ni‐0.5Au/Ni joint after for 1,000 h.

Originality/value

This study focuses on the interfacial reactions of Sn‐2Cu‐0.5Ni/Ni and Sn‐2Cu‐0.5Au/Ni during soldering and isothermal aging.

Citation

Zhao, N., Ma, H. and Wang, L. (2009), "Interfacial reactions between Sn‐Cu based multicomponent solders and Ni substrates during soldering and aging", Soldering & Surface Mount Technology, Vol. 21 No. 2, pp. 19-23. https://doi.org/10.1108/09540910910947435