Best probe tip material for delicate contact electrodes?

When characterizing a sample with delicate contact electrodes in a probe station, which type of probe tip material is best to use and ensure the best electrical contact performance?

Lake Shore offers three different types of probes distinguishable by their probe tip material. For delicate or softer contact materials (such as gold), beryllium copper (BeCu) probes are recommended. These are the softest probe tips offered, providing conventionally the lowest contact resistance and the smallest amount of deformation to the contact metallization. Over time, the BeCu material is known to form a semi-insulating layer which can diminish contact performance; see Section 6.2.7 of your probe station manual for maintenance protocols for this probe material. This probe material is available on both standard DC/RF and continuously variable temperature (CVT) probes.

At the other extreme, for aluminum, refractory metals, and other material contacts that develop oxides, a standard ZN50 tungsten probe will best puncture hard oxide material layers to make electrical contact with underlying layers and will not dull as quickly as softer probe materials. Because the spring member on the CVT probe reduces the pressure at the tip apex, tungsten CVT probes may have difficulty punching through hard insulating layers and are not recommended for oxidized contacts (such as aluminum).

A good intermediate solution between beryllium copper and tungsten is a paliney probe tip material offered on Lake Shore’s standard DC/RF probes. A paliney probe offers low contact resistance but a little bit stronger of a probe tip material (while also being the least reactive material and are least likely to form resistive oxides, especially at high temperatures).