Effect of Ag addition on the structures of intermetallic compounds and the adhesion strength of the Sn–9Zn– xAg/Cu interface

Abstract

The effect of Ag addition on the structures of the intermetallic compounds (IMCs) and the adhesion strength of the Sn–9Zn– xAg solder alloy/Cu interface has been investigated by X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, transmission electron microscopy and electron diffraction. The XRD patterns show that the η-Cu 6Sn 5, η′-Cu 6Sn 5 and Cu 5Zn 8 are found at the Sn–9Zn– xAg/Cu interface. The Ag 3Sn formed at the interface when Ag addition is above 2.5 wt%. Monoclinic and hexagonal Cu 6Sn 5 intermetallic compounds (IMCs) are formed at the interface close to the solder alloy. A high-resolution lattice image also shows the same result and the bi-structural Cu 6Sn 5 grows as a twin-like crystallite along the boundaries. The adhesion strength has an opposite relationship to the crystallite size of the Cu 6Sn 5 layer.