Post by Professor Lake Shore on Jan 31, 2017 17:26:36 GMT -5
I don’t want to damage the tips of the probe as well as my sample by needlessly trying to make electrical contact with a sample under test in my probe station. When landing a probe for the first time, how can I tell when sufficient contact is made?
First, always remember to raise the probe tips before cooling or warming the system or applying vacuum, and when moving probes in the x or y direction. When using a standard (non-CVT) ZN50R probe, follow this procedure to manipulate a probe to the sample and make contact:
1. Swing the microscope away from the viewport.
2. Use the z-axis micrometers to raise all probes 3 to 4 mm above the sample (failure to do so will potentially cause damage to the probe tip or scratch the sample surface).
3. Position the probe tips over the sample or landing pads using the x-axis hand dial and y-axis micrometer.
4. Swing the microscope over the viewport.
5. Adjust the microscope to fill the monitor with the sample image and focus at the height of the landing pads or landing surface.
6. Use the z-axis micrometer to move the probe tip up and down until the tip begins to come into focus (at this point, the tip is only 30 to 60 μm away from the sample).
7. Continue lowering the probe slowly, stopping to position it as needed so the tip lands on the outside edge of the landing pad.
8. Once it lands on the pad (which is indicated by a forward movement known as skating), continue lowering it until it skates on the pad by a consistent amount. A typical amount of skating is 20 to 25 μm, which is roughly the same as two scale graduations on the z-axis hand dial.
9. The desired position of the probes with respect to the edge of the pads and the desired amount of skating should be determined and used as a lab standard to ensure consistent results.
For more on this, watch this “Landing a DC Probe” video.
If you are using a CVT probe, however, the procedure is rather different. The very important difference is that no skating occurs (and, if it does, skating can destroy the probe). Instead, the spring member and probe wire will flex. Users should watch for this flexing movement when beginning to make contact. Too much downward Z-travel after making contact can result in too much force on the probe tip and cause damage. However, too little downward Z-travel can result in too little force exerted, reducing the variable temperature performance. Too little force can also cause poor or inconsistent electrical contact. The step-by-step procedure can be found here. For additional help landing a CVT probe, watch this video.