Nano-porous structure control under electrodeposition and dealloying conditions for low-temperature bonding

We investigated a low-temperature bond formation process, wherein nanoporous structures were formed on electrode surfaces by electrodeposition and dealloying. The morphology control of a nanoporous Au-Ag structure was investigated using electrochemical deposition and electrochemical methods. The ligament size of the electrodeposited Au-Ag films after dealloying increased upon annealing. The ligament size of 10-20 nm for as-deposited increased to 50-100 nm for films annealed at 150 °C. The samples that were annealed at 50 °C before dealloying indicated a finer nanoporous structure, which corresponded to the highest bond strength of the evaluated samples. The volume of selective dissolution was small on as-deposited samples despite the anodic current being the largest of the examined films. Inductively coupled plasma mass spectrometry (ICP-MS) analysis showed that the change of the Ag content of the films after dealloying of as-deposited samples was the smallest of the examined films. Small ligament size with a finer nanoporous structure resulted in high bond strength.