Reliability of press-fit pins in printed wiring boards

Stable electrical and mechanical interconnections can be made within the extreme tolerance limits of ±0.003″ of a specified hole diameter. Specifically, resistance value changes of less than 1 mΩ were obtained after all environmental tests and retention forces were maintained above 12 Ibs. Properly repaired pins had similar maximum resistance changes and minimum retention forces. For all but one resilient cross-section pin, maximum removal forces of over 50 Ibs. were obtained, so repair procedures must be carefully planned. These tests indicate that these limits are viable provided that (a) the drilled hole dimension is specified and controlled to within ± 0.001, (b) the diagonal of the contact is controlled to ±0.001, (c) copper plating shall be minimum 0.001″, (d) the hole size after copper plating shall insure a minimum 0.002″ interference fit, (e) solder plating should not be used to close the gap of tolerance limits unless all previous requirements have been met. Any proposed deviation from these recommendations would have to be justified on the basis of other tests.