Tailoring the Cu6Sn5 layer texture with Ni additions in Sn-Ag-Cu based solder joints

The orientation of Cu6Sn5 in the reaction layer can influence the electrical conductivity and mechanical properties of solder joints. This paper explores the role of Ni on the growth orientation of the Cu6Sn5 layer on Cu and Ni substrates. The crystallographic texture of the Cu6Sn5 layer is measured by electron backscatter diffraction analysis (EBSD). It is shown that the Cu6Sn5 layer grows with a strong {0001} fibre texture when Sn-3.0Ag-0.5Cu-xNi (wt.%) alloys are soldered to Cu substrates, and that the Cu6Sn5 growth texture changes to a {1010} fibre texture when Sn-3Ag-0.5Cu-xNi (wt.%) is soldered to Ni. The Cu6Sn5 composition and nickel distribution are examined and the thickness, grain size and the growth facets of Cu6Sn5 crystals in the layer are investigated to understand the effects of nickel content on the Cu6Sn5 layer morphology and texture. The results are used to discuss the potential of using Ni as a means to control the texture of the intermetallic layer.