The Effect of Fluid Flow on Particle Codeposition in Electrolessly Plated Nickel-Diamond Composite Films

Abstract

The composite plating codeposition mechanism is important to control the volume fraction of particles embedded in plated films. Effects of the plating bath fluid flow on particles adsorbed onto a deposition frontier must be considered because particle embedding occurs during agitation. For this study of fluid flow effects using a rotating disk electrode（RDE）during rotation at 0-1200 rpm, we prepared diamond particles of various diameters with a homogeneous surface state. Dependence of the volume fraction of embedded particles on the rotation rate was investigated. Results show that the volume fraction of 5 nm and 20 nm diameter particles increased concomitantly with the flow rate because mass transport was promoted. In contrast, 100 nm, 200 nm, 500 nm, and 1000 nm diameter particles decreased concomitantly with increase of the flow rate. We inferred Magnus force as the factor which decreased the volume fraction of the particle in this case. The force was estimated as sufficiently stronger than gravity and buoyancy. Accordingly, that force dominated the codeposition process for particles with 100 nm or greater diameter.