Comparison of the fracture toughness of Cu6Sn5 intermetallic compound as measured by nanoindentation and other methods

• Nanoindentation tests are performed for a Cu6Sn5 intermetallic compound (IMC).
• Effects of the strain rate on the mechanical properties of Cu6Sn5 are evaluated.
• Fracture toughness of Cu6Sn5 is determined.
• Results on the nanoindentation fracture toughness are compared to others.

In this work, nanoindentation tests using a three-sided Berkovich indenter were performed for a Cu6Sn5 intermetallic compound (IMC) in interfacial specimens of lead-free Sn–3Ag–0.5Cu solder ball joints at room temperature to investigate effect of the strain rate on the mechanical properties of this IMC. The fracture toughness was found to have an approximately linear relationship with the logarithmic nanoindentation strain rate, implying that the fracture toughness decreased in a range of (1.64–0.63) MPa m0.5 with an increase in the strain rate ranging from 0.01 s−1 to 0.33 s−1. This characteristic was similar to the KC values of Cu6Sn5 under shear or tensile tests. It was, however, when measured by nanoindentation tests, found to be less sensitive to the strain rate compared to measurements gained through shear or tensile tests. The results here were discussed and compared to those from other studies.