Grain Growth and Microstructure of Silver Film Doped Finite Glass on Ferrite Substrates at High Annealing Temperature

The preferred orientation of silver grains was (111) plane, and the nucleation of silver films doped finite glass on ferrite substrates proceeded with a typical non-wetting mode according to X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. The silver grain growth exponent ( n ) at high annealing temperatures was 2.7–3.4, which increased as annealing temperatures increased. The activation energy ( Q ) of grain growth in silver was 33 ± 3 kJ/mol, indicating that the mechanism of grain growth was dominated by surface diffusion mass transport at high annealing temperatures (from 0.85 to 0.94 T m , where T m is the melting point of silver). SEM analysis showed that the grain boundaries in silver films undergo faceted-defaceted transitions from 820 to 900°C. The annealing temperature had a more pronounced impact on faceted grain boundaries than the holding time. Nickel particles were firstly electrodeposited at the upper corners of the silver film trench at an early stage of the recrystallization process, then grew laterally between the steps and eventually transformed the entire nickel film, which could prevent solder from eroding silver films at high package temperatures.