Case study

CAUSE

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.

PROBLEM SOLUTION

These methods decrease contact resistance;

①Strengthen the spring force

Strong force can improve the probes’ ability to break contaminants or the oxidation layer.

②Change 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.

③Change the tip material

Change it to conductive materials so that a temperature-rise would be prevented