The surface finish may be a task to consider when working with tantalum beads. Determination of a proper finish for a given application can be problematic, as there are no specific ball specification for tantalum. Commonly industry ball grades adapted from steel ball processing (like e.g. ABMA or ISO 3290) are also used to specify tantalum balls. When using the standards however, only reference to the basic diameter is given by manufactures, so purchasing a “good” grade bead is no guarantee for a suitable surface finish.
Determination of surface roughness
Traditionally Ra measurements are used to describe the surface finish of a component. When it comes small diameter balls, such measure may not be usable, as the reading “tip” of the equipment is often relative large compared to the roughness to be measured. It may therefore be difficult to use the Ra value to describe the actual roughness of the ball surface.
X-medics’ experience is that Scanning Electron Micrographs may be a suitable way to evaluate the finish of the tantalum surface for beads or balls. Is does not provide a quantitative figure, but offers a good visual idea about the surface quality. The SEM pictures below shows examples of 2 polished and a super-polished tantalum sphere.