Dynamic characterization of surface-mount component leads for solder joint inspection

Vibration frequencies of soldered and unsoldered leads of surface-mount wide and narrow small outline integrated circuits (SOICs), plastic leaded chip carriers (PLCCs), and plastic quad flat packs (PQFPs) are calculated using the finite-element method. The corresponding mode shapes of the leads and solder joints are also provided for a better understanding of their dynamic characteristics. It is found that the fundamental frequencies of all the soldered leads are at least five times larger than those of the unsoldered leads. A laser Doppler vibrometer method is developed to measure the frequency of soldered and unsoldered leads of these four surface-mount components. Experiments and theory are in close agreement. The results presented should be useful for theoretically determining the reliability of solder joints under shock and vibration conditions, and for developing a solder joint inspection system for use in a controlled manufacturing process