Eliminating Preferred Orientation and Refining Grain Size with Ni Doping in Cu/Sn-3.0Ag-0.5Cu/Cu TLP Bonding under Isothermal Aging Treatment

Transient liquid phase (TLP) bonding has been demonstrated to provide strong and reliable joining capabilities at high temperatures in chip stacking applications. However, traditional Cu/Sn/Cu transient liquid phase bumps had certain limitations, such as smooth phase boundaries and grain coarsening. The research focuses on the microstructure and mechanical strength of Cu/Sn-3.0Ag-0.5Cu/Cu, Ni/Sn 3.0Ag-0.5Cu/Cu, and Cu/Sn-3.0Ag-0.5Cu/Ni transient liquidphase (TLP) bonding before and after long-term aging. It is demonstrated that the Ni substrate, whether at the cold or hot end, tends to diversify the orientation and refine the grain structure of Cu
6
Sn
5
. After 1000 hours of aging treatment, Cu
6
Sn
5
still retains multi-oriented structures, while the Cu
3
Sn IMCs layer has been partially suppressed. Moreover, elemental mapping reveals the network-like morphology of Cu3Sn IMCs, which impedes the propagation of cracks along the interface of Cu
3
Sn IMCs/(Cu,Ni)
6
Sn
5
. These factors indicate that the addition of Ni results in higher shear strength as compared to that without the presence of Ni. In short, this approach shows a promising and effective approach for advanced electronic packaging.