Zn diffusion and reflow behaviour of Sn-9Zn and Sn-8.5Zn-0.5Ag-0.01Al-0.1Ga solders on a Ni/Cu substrate under IR reflow

Mittal, Jagjiwan; Lin, Kwang‐Lung

doi:10.1108/ssmt-07-2013-0020

Cited by 2 publications

(1 citation statement)

References 33 publications

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“…Therefore, a coating of Ni over the Cu metallization is often used as a diffusion barrier (Chan et al, 2002). Studies have been reported on the reaction of different solders with Cu substrates (Ju et al, 2014;Zhu and Sun, 2017;Bi et al, 2012;Yan et al, 2016) and Ni/Cu substrates during reflow and ageing (Huang and Lin, 2004;Lee et al, 2005;Mittal and Lin, 2012;Mittal and Lin 2014;Tian et al, 2003). Reaction of Sn-Ag, Sn-Cu and Sn-Bi solders with Ni substrates leads to the formation of Ni 3 Sn 4 IMC, whereas the Sn-Zn solder alloy reacts with Ni to form the Ni 19 Zn 80 Sn IMC (Chan et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Diffusion of elements during reflow ageing of Sn-Zn solder in liquid state on Ni/Cu substrate – theoretical and experimental study

Mittal

Lin²

2018

SSMT

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Purpose This paper aims to study the diffusion of Zn, Ni and Sn in the liquid state during the reflow ageing of the Sn-Zn solder above its melting point on an Ni/Cu substrate in relation to the formation of intermetallic compounds (IMCs). Design/methodology/approach The Sn-Zn solder is reflowed on Ni/Cu substrates and is aged at 503 K. The formation of IMCs and their composition is characterized using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Diffusion coefficients and diffusion distances of Zn, Ni and Sn in the liquid state during reflow and ageing are theoretically calculated. Both experimental and theoretical behaviours for Ni and Zn diffusions are compared. Findings Calculations show a linear increment in the liquid-state diffusion coefficients of Ni, Zn and Sn in the solder matrix with a rise in temperature, but they remained constant during ageing. However, diffusion distances increased slowly with temperature but manifold with ageing time. The experimental results revealed segregation of Zn and Ni at the interface in the as-reflow aged specimens. The Zn was concentrated at the solder–substrate interface and it reacted with Ni diffusing from the substrate to form Ni-Sn-Zn IMCs. The rapid diffusion of Zn and Ni with the increase in ageing time increased their atomic concentrations in the IMCs against the reduction in Sn concentration owing to a comparatively slower diffusion. Originality/value The novelty of the paper is the detailed study of theoretical diffusion of Zn, Sn and Ni in the liquid state during reflow ageing of Sn-Zn above its melting points on a Ni/Cu substrate. This is compared with values obtained experimentally and related to the mechanisms of IMC formation.

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