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High contact resistance exhibited by test contactors is the result of contact contaminants and contactor surface finish degradation. Because of this unwanted resistance, the integrity of device testing is affected, resulting in yield and/or yield-to-grade problems. The amount of contact resistance exhibited by a contactor is in direct proportion to the number of contact cycles that it has already undergone. A 500 milli-ohm contact resistance can be acquired after 1,024,511 contacts. It will take 177,222 contacts before an SOIC contactor will wear out. Cleaning the contactors with deionized water and baking it for 10 minutes at 125 deg C will effectively remove contaminants that increase contact resistance. To do effective testing, this paper recommends that the contact resistance be maintained below 50 milli-ohms. This is equivalent to 102,000 contacts, so the contactors must be cleaned before this number of contacts is reached.
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