Influence of Some Geometric Factors on Contact Resistance Probe Measurements

The effect of variations in the geometry and preparation of gold probe tips for contact resistance measurements has been evaluated. Tips prepared by melting and by machining and possessing shapes ranging from a point to hemispheres with radii from 0.9 mm to 3.2 mm were used. The contact resistance values are nearly independent of probe geometry on gold and on very lightly filmed (<5 to 10 Å) copper targets. On more heavily filmed copper and nickel targets, the contact resistance varies as much as 2½ orders of magnitude at a fixed contact force. The only known variable is the apparent contact area of the various tips, determined by examination in a scanning electron microscope (SEM) after use. It appears that contact pressure predicts contact resistance more reliably than does contact force.