Absorption of Ag3Sn on Cu6Sn5 Intermetallic Compounds at Sn-3.5Ag-xCu/Cu Interfaces

摘要

The absorption behavior of Ag3Sn particles on the surface of intermetallic compounds (IMCs) formed at Sn-3.5AgxCu/ Cu (x=0, 0.7, 1.5 wt.%) interfaces was studied. The Sn-3.5Ag-xCu/Cu solder joints were prepared by reflow soldering at 260℃ for different time. The X-ray diffraction results showed that the dominant IMCs formed at Sn-3.5AgxCu/ Cu interfaces were Cu6Sn5. For Sn-3.5Ag/Cu and Sn-3.5Ag-0.7Cu/Cu joints, when the reflow time reached 120s and 60s respectively, besides Cu6Sn5, Ag3Sn particles were also found at the interface. While for all the reflow time in this study, the Ag3Sn particles were always detected at Sn-3.5Ag-1.5Cu/Cu interfaces. To observe the morphology of the interfacial IMCs, scanning electron microscope were performed. It was found that with the increase of the grain size of Cu6Sn5 the amount of absorbed Ag3Sn particles increased. During the solidification, the Ag3Sn particles could play the role of surface energy reducer for the interfacial Cu6Sn5 grains. There should be a critical grain size at which the absorption behavior of Ag3Sn particles on Cu6Sn5 grains happened. According to this study, the critical grain size was determined to be about 2 μm.