US Patent 7733101 Knee probe having increased scrub motion

Improved probing is provided using a knee probe where the knee curves away from the probe axis and then curves back to connect to the probe tip, crossing the probe axis on the way to the tip. The resulting lateral offset between the probe tip and the probe axis is a key geometrical parameter for predetermining the scrub motion provided by the probe in response to a predetermined contact force. The scrub motion preferably includes both a sliding motion and a rocking motion, where the sliding motion acts to clean the contact pad and the rocking motion acts to bring a clean part of the probe tip into contact with the freshly cleaned part of the contact pad. In preferred embodiments, the probe tip can include one or more relatively narrow “skates” for making contact to the contact pad. A dual skate configuration is especially appropriate when small dimples are at the centers of the contact pads.