High-frequency vibration tests of Sn-Pb and lead-free solder joints

There are many applications in which electronics devices are subjected to vibration. Yet while there has been much research into the effects of low-cycle fatigue, there has been very little in the field of high-cycle fatigue, despite this being of interest in critical fields such as the aerospace industry. In consequence, this work has been aimed at studying lead-free solder alloys in a high-frequency environment, above 100 Hz, using SnPb alloy as a benchmark. Many previous studies on high-cycle fatigue have been focused on studying the effects on a full printed circuit board. That assessment method, however, is not suitable for characterising the solder performance, as the approach is geometry and condition specific. In this work therefore, a more general approach has been adopted, using a reproducible model solder joint as the sample to which well-controlled vibrations have been applied. This study highlighted the different behaviour of the various alloys when subjected to vibration, and in particular the superiority of the SnPb alloy, especially at higher frequencies. This method has been shown to be useful in characterising and ranking various materials, and tests could be easily repeated with a range of conditions, targeted at specific industrial applications. The method is versatile, and the equipment could easily be modified for testing at high temperatures.