Title: Effect of multiple reflow on IMC formation using various surface finishes

Authors: I. SitiRabiatull Aisha; A. Ourdjini

Addresses: Faculty of Mechanical Engineering, University Malaysia Pahang, 26600 Pekan Pahang, Malaysia ' Materials Department, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81300 Skudai, Johor, Malaysia

Abstract: In this paper, the results of a study on the effect of multiple reflow on the mechanism of intermetallic compounds (IMCs) formation of solder joints made from lead-free Sn-4Ag-0.5Cu (SAC405) on electroless nickel/electroless palladium/immersion gold (ENEPIG), electroless nickel/immersion gold (ENIG), immersion silver (ImAg) and copper surface finishes are presented. After the first reflow soldering, the well-known intermetallic Cu₆Sn₅ was observed in ImAg and Copper of surface finishes. While for ENEPIG and ENIG, mainly, (Ni,Cu)₃Sn₄ and (Cu,Ni)₆Sn₅ was formed respectively. By increasing the number of reflows up to three, the thickness of intermetallics increased gradually and their grain sizes coarsened. The intermetallics growth kinetics showed that the interfacial phase Cu₆Sn₅, (Ni,Cu)₃Sn₄ and (Cu,Ni)₆Sn₅ was controlled mainly by grain boundary diffusion and that the intermetallic growth on ENEPIG was found to be slowest among other surface finishes being used.

Keywords: multiple reflow; intermetallic compounds; IMC; surface finish; solder joints; reflow soldering; thickness; grain size; intermetallics growth kinetics; grain boundary diffusion.

DOI: 10.1504/IJMMP.2012.051230

International Journal of Microstructure and Materials Properties, 2012 Vol.7 No.6, pp.502 - 516

Published online: 28 Dec 2012 *

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