Electrodeposition and Characterization of Nanocrystalline Ni–B with Low Boron Content for MEMS Applications

Abstract

We fabricated and characterized three kinds of nanocrystalline (NC) Ni-B electrodeposits with low boron content (i.e., 0.05, 0.12, and 0.19 wt.%) for micro-electromechanical system (MEMS) applications. The fabrication was performed by electrodeposition in a nickel sulfamate solution, adjusting the concentration of the boron source, dimethyleamine borane (DMAB). The electrodeposits exhibited high thermal stability, being able to maintain their grain size at 573 K, whereas pure NC Ni started recrystallizing at 473 K. This can be explained by the formation of Ni x B precipitators in the nickel matrix, which then migrate to the grain boundary region and effectively impede grain growth at high temperatures. Furthermore, the mechanical properties of NC Ni-B electrodeposits were significantly enhanced and they exhibited excellent mechanical performance. The hardness and elastic modulus of Ni-0.19B with 573 K heat treatment are 251.4 and 12.6 GPa, respectively, which are much higher than those of pure NC Ni. These outstanding properties show the potential applicability of NC Ni-B electrodeposits as microgears, micocantilevers, microactuators, and MEMS probe cards, which require high mechanical performance and thermal stability.

A Numerical Study of Joule Heating Effect in Electrodeposition Process-Case of Copper Electrodeposition

“…The third relates to the electrodeposit properties, where previous studies suggest that increasing the temperature to 60 0 C increases surface roughness or dendrite formation (Gonçalves et al, 2021;Jeon et al, 2022). Kwon et al (2017) found that increasing temperature reduces the hardness of some deposits and increases the grain size.…”

Electrodeposition of Ni–B Alloy Film: Effect of Current Density and Heat Treatment on Micro-Mechanical Property

“…9,10 It is also reported that Ni-B alloys have a better performance in the under bump metallization (UBM) packaging process comparing to Ni-P. 11 In addition, Kwon et al have reported Ni-B MEMS-based micro-probe for wafer-level integrated circuit tests with a higher stiffness than conventional Ni-Co probe. 12 Furthermore, heat treatment or thermal annealing is a common process applied in fabrication of electronic components, such as the fabrication of MEMS accelerometer. 13 Mechanical properties of electrodeposits are expected to be affected by the heat treatment process.…”