Dynamic characterization of surface mount component leads for solder joint inspection

Vibration frequencies of soldered and unsoldered leads of surface mount 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 provided for a better understanding of their dynamic characteristics. It is found that the fundamental frequency of all the soldered leads is at least five times larger than that of the unsoldered leads. A laser Doppler vibrometer method has been developed to measure the frequency of soldered and unsoldered leads of these surface mount components. Experiment and theory are in close agreement. The results presented should be useful for determining the reliability of solder joints under shock and vibration conditions and for solder joint inspection during a controlled manufacturing process