Case study

Background of the Problem Spark occurs at a contact point. The measurement values cannot be obtained at all.
The tip shape seems melting.
Measurement Conditions
  • Electric Current - 90A Device Under Test (DUT) - Copper (Aurum plating)
  • Probe - CP50-F SPS (Carbon tool steel, Flat, 2/3 spring compression of 450g)


This tip type (Flat) was the cause of increasing contact resistance. It contributed to heat generation at the contact point.

A flat tip is a very effective shape to make contact resistance low only if the whole its surface contacts snugly to the target. However, it can also make contact resistance high if it hits the target in the slant way, or if contaminants exist between the tip and the target.

The high temperature which results from high contact resistance can soften and melt the surface material of the target and the probe.
The melted material turns to be contaminants and attach to the contact point. Furthermore, the contaminants are oxidized by the electric charge, and prevent the flow of the current. As a result, spark occurs at the contact point, which generates heat, softens the surface material again and leads to more contaminants at the contact point. These series of events are the ultimate cause of this problem.


These methods decrease contact resistance;

Strengthen the spring force
Strong force can improve the probes’ ability to break contaminants or the oxidation layer.
Change the tip shape
Change it to a serrated tip. The tip can penetrate the oxidation layer and contaminants on the DUT surface so that data would not be affected by these unwanted elements.
Change the tip material
Change it to conductive materials so that a temperature-rise would be prevented

※In case the slanting angle of the probe performance was excessive, a serrated tip withw multiple points may not be effective. In that case, we recommend a spear point which makes contacts at one point. Solution methods are different depending on the conditions of measurements under high current.