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

The orientation of Cu
₆
Sn
₅
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 Cu
₆
Sn
₅
layer on Cu and Ni substrates. The crystallographic texture of the Cu
₆
Sn
₅
layer is measured by electron backscatter diffraction analysis (EBSD). It is shown that the Cu
₆
Sn
₅
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 Cu
₆
Sn
₅
growth texture changes to a {101̅0} fibre texture when Sn-3Ag-0.5Cu-xNi (wt.%) is soldered to Ni. The Cu
₆
Sn
₅
composition and nickel distribution are examined and the thickness, grain size and the growth facets of Cu
₆
Sn
₅
crystals in the layer are investigated to understand the effects of nickel content on the Cu
₆
Sn
₅
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.