Karl Suss, in cooperation with Rosenberger, has developed a high-frequency wafer probe tip. The tips are available for probing up to 65GHz; it is expected to accommodate frequency levels up to 110GHz soon. The Z-probe enables precise and safe contact with a unique planar-planar transition, making the transition from coax to planar within the probe body and isolating with air to assure minimal insertion loss, as other probes make the transition at the tip, which results in measurement interference that needs to be calibrated out of the result. High accuracy is critical for RF testing where the smallest reflections distort the measurement. Ac-curacy is maintained because the tips are manufactured with micromachining. This ensures that the contact springs have submicron accuracy, so the impedance can be controlled very precisely. Other tip designs need a significant overtravel to contact the device under test. In the Z-probe, the springs move independently of one another along the wafer ensuring perfect contact and requiring less overtravel. The tips showed almost no wear after over one million touchdowns.
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