Investigation of surface mechanical properties of the copper-solder interface by atomic force microscopy

In this work, the possibility to characterize the mechanical surface properties of solder-joints with AFM techniques was studied. A SAC305 solder joint cross-section was investigated with contact-mode point-spectroscopy to determine the elastic modulus, while tapping-mode imaging was used to calculate the tip-sample dissipation map. A clear advantage of these proposed methods would be the possibility to distinguish the various micro- and nanoscale components of the solder joint structure (intermetallic compounds) and measure their properties individually, which is not possible with other currently widespread methods (e.g. indentation). Our presented preliminary results show, that the mechanical properties of the Cu6Sn5 compound at the solder interface are closer to Cu compared to the much less harder Sn. The difficulties to obtain precise quantitative results with these proposed methods will also be discussed.