Interfacial Microstructure and Intermetallics Developed in the Interface between In Solders and Au/Ni/Ti Thin Films during Reflow Process

摘要

Intermetallic phases and microstructures formed between In solder and Au/Ni/Ti thin films during reflow were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Two types of two-step heat treatment were performed in a rapid thermal annealing (RTA) system or in a furnance to simulate the flip-chip solder-joining process. The AuIn_2 and In_27Ni_10 intermetallic phases were observed after the two-step heat treatment at the lower temperature. Additional In-Ni intermetallic layers formed between the In_27Ni_10 and Ni layer, which was two-step heat treated at the higher temperature. This phase was identified as metastable InNi of CsCl type with a = approx 3.1 A by convergent-beam electron diffraction (CBED).