Ripening Growth Kinetics of Cu_6Sn_5 Grains in Sn-3.0Ag- 0.5Cu-xTiO_2/Cu Solder Joints During the Reflow Process

摘要

The ripening growth kinetics of interfacial Cu _( 6 ) Sn _( 5 ) grains between Cu substrates and Sn-3.0Ag-0.5Cu-xTiO _( 2 ) (x = 0, 0.02, 0.05, 0.1, 0.3, and 0.6 wt %) (SAC305-xTiO _( 2 ) ) solders were investigated. The results show that the Cu _( 6 ) Sn _( 5 ) grain morphology is affected by the solder composition and the reflow time. The Cu _( 6 ) Sn _( 5 ) grain size decreases upon addition of TiO _( 2 ) and shows a significant decrease when the TiO _( 2 ) nanoparticle fraction is increased to 0.1 wt %. At higher TiO _( 2 ) nanoparticle fractions, the Cu _( 6 ) Sn _( 5 ) grain size increases slightly. The growth of the Cu _( 6 ) Sn _( 5 ) grains is mainly supplied by the flux of the interfacial reaction and the flux of ripening; the ripening flux plays a dominant role because it is approximately one order of magnitude greater than the interfacial reaction flux. The ripening growth of the Cu _( 6 ) Sn _( 5 ) grains in the TiO _( 2 ) -containing solder joints is reduced more effectively than that of the Cu _( 6 ) Sn _( 5 ) grains in the TiO _( 2 ) -free joint. For the SAC305/Cu and SAC305-0.6TiO _( 2 ) /Cu solder joints, the particle size distribution (PSD) of the Cu _( 6 ) Sn _( 5 ) grains is well fit with the Marqusee and Ross (MR) model when the normalized size value of r/ is less than 1, and it is consistent with the flux-driven ripening (FDR) model when the value of r/ is greater than 1. On the other hand, for the SAC305-0.1TiO _( 2 ) /Cu solder joint, the Cu _( 6 ) Sn _( 5 ) grains with a nearly hemispheric scallop shape and the PSD of the Cu _( 6 ) Sn _( 5 ) grains show good agreement with the FDR model.