Report on Connector Miniaturization - The Effect of Contact Miniaturization on Sensitivity to Tolerances.

The connector industry is moving toward higher contact density at an increasing rate. As a result, electrical contacts need to be made smaller. A consequence of this trend is the increased sensitivity of the reduced contact to tolerances in geometric and material parameters. We will examine this effect for three different contact types that cover a broad range of product: thin beam-like contacts, press-fit compliant contacts, and insulation displacement contacts. Closed-form and finite element techniques are used in this analysis. We find that the increase in sensitivity for beam-like contacts is greatest for tolerances in length; for most designs, however, thickness will be the critical parameter in reduction. Also, the tolerance in a given parameter has to be reduced by the scaling factor in that parameter to maintain the same resulting normal force variation. For C-shaped compliant sections, normal force is most sensitive to backwall thickness. Scaling down the current design to meet the METRAL requirements is possible if hole size is kept to +- 2 mils, and other dimensions are kept within a 1 mil range. (By comparison, current production allows for a 5 mil range in hole size, and about a 2 mil range in the compliant section thickness and radius). The "needle-eye" compliant section is less sensitive to thickness variations than the C-section, and this sensitivity is nearly constant as we scale down. Also, the needle-eye section is able to tolerate a larger range of hole sizes than the C- section. However, a needle- eye section dimensioned for METRAL may not be manufacturable, because of stamping constraints. Finally, decreased normal force and increased sensitivity to slot width make it unlikely that a scaled down "tuning-fork" IDC contact is feasible for termination of 0.025" pitch ribbon cable.