The Optimum Surface Finish of Tantalum Beads

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.

Polished Ball – 1 (rough)

A polished (but still rough) tantalum bead. A cost optimized option for many applications

Polished Ball – 2 (normal)

Tantalum bead surface after super polishing

Super Polished Ball

Tantalum Sphere, that has undergone a super polishing step for a high-end surface finish

Controlling the finish during beads processing

During the ball manufacturing process from tantalum wire, the surface roughness’ may be affected by a number of parameter during processing including, exact equipment settings, timing, the type and concentration of the grinding/polishing media, lubrication, etc. Variations in the surface finish after a process step will therefore occur from batch to batch. For a well-controlled ball manufacturing process, the variation in the roughness will normally be less than illustrated by balls 1 and 2 above. The common way to reduce the surface roughness is to polish for a longer time and/or add additional polishing steps in processing. More processing on the other hand will add-on cost to production.

Cost optimized processing

The optimum surface quality is a trade-off between cost and product performance. The questions is satisfy the requirement without over-specifying the manufacturing process. To help customers, X-medics has introduced  2 surface qualities: a standard-polished and a super-polished. The standard polished beads undergo a single polishing step during bead processing and is a cost optimised option suitable for most applications. The super polished beads is a high-end option undergoing several final polishing steps after the grinding/lapping operation and may be used where the surface roughness of the beads are of importance (e.g. automated processing).

More information

Find information on X-medics’ products here

Tantalum Beads

Tantalum Balls

Tantalum Spheres

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