Interfacial reactions between SnAg1.0Ti and Ni metallization

The effect of Ti on the solid state reactions between Sn and Ni has been investigated in this work. Based on the experimental results the following statements can be made: Firstly, the presence of Ti does not have measurable effects on the thickness evolution of Ni₃Sn₄ during solid state annealing. Secondly, the results from long term heat treatments show that there is no marked solubility of Ti to Ni₃Sn₄. Rather Ti reacts with Sn to form large Ti₂Sn₃ platelets inside the solder matrix. The Sn-rich part of the Ni–Sn–Ti phase diagram was assessed in order to rationalize the experimental results. By utilizing this information, the absence of any marked effects of Ti on the growth of Ni–Sn intermetallic compounds (IMC) was analysed. As there is no solubility of Ti to SnAg solder or to Ni–Sn IMC’s, Ti cannot change activities of components in the solder nor influence the stability of the IMC layers. Hence, these results throw significant doubts over the concept of trying to influence the Ni–Sn IMC layer thickness or quality by Ti alloying.