Comparative compliance of representative lead designs for surface mounted components

Equations for the directional spring constants for common compliant lead designs for surface-mounted (SM) components are given. The lead configurations include the straight J-lead, dimpled J-lead, gull-wing lead, butt-lead (I-lead), and S-bend lead. The updated lead geometries and analysis method represent an expanded treatment of previous lead compliance studies by the author. The present objectives are to demonstrate applications of the analytic tool developed and identify the directional stiffness parameters that should be considered when assessing the compliance of a specific lead design. Comparative lead compliance evaluation has been performed for different SM components tested using accelerated function cycling or circuit-board dynamic bending. The solder-joint cycles-to-failure data indicate that significant differences in attachment fatigue performance can be correlated with disparate lead compliance among the SM packages tested