Cu6Sn5 Morphology Transition and Its Effect on Mechanical Properties of Eutectic Sn-Ag Solder Joints

Abstract

The morphologies of Cu 6 Sn 5 grains formed at the interface between Sn-3.5Ag (wt.% unless otherwise specified) and Cu substrates were studied in this work. Reflow experiments were performed for 60 s at peak temperatures of 513 K, 533 K, 543 K, and 553 K. Two morphologies of interfacial Cu 6 Sn 5 grains were observed in wetting reactions: prism type, above 543 K, and scallop type, below 533 K. During aging, the two morphologies gradually transitioned to layer type. These three morphologies could be transformed into each other as long as the corresponding condition changed. The morphology transition of Cu 6 Sn 5 in the wetting reaction was explained by the change in Jackson's parameter with temperature. In addition, the effect of the Cu content in molten solder on interfacial Cu 6 Sn 5 grains was examined. Significant differences in shear strength were observed for solder joints with different interfacial Cu 6 Sn 5 morphologies in the case of a lower shear height. Joint strength is discussed in terms of the microstructure of the solder matrix and the morphology of interfacial Cu 6 Sn 5 grains.

Morphology transformation on Cu3Sn grains during the formation of full Cu3Sn solder joints in electronic packaging

“…For analyzing the morphology transformation on the Cu 3 Sn grains during the formation of full Cu 3 Sn solder joints, it is necessary to expose the Cu 3 Sn grains within joints of different soldering time. However, in consideration of Cu 3 Sn layers growing below Cu 6 Sn 5 layers (as shown in Figure 1) and very good etch resistance of Cu 6 Sn 5 (Yang et al, 2010;Yao et al, 2017a), it is impossible to expose the Cu 3 Sn grains within joints, which leads to the infeasibility in observing the morphology of the Cu 3 Sn grains within joints. As a result, it becomes impossible to intuitively study the morphology transformation on the Cu 3 Sn grains during the formation of full Cu 3 Sn solder joints.…”

In situ study on the effect of thermomigration on intermetallic compounds growth in liquid-solid interfacial reaction

“…According to the facet growth kinetics proposed by Brice, 23 the undercooling for different morphologies is different, in particular, the undercooling for two-dimensional nucleation growth mechanism is larger than that for rough interface growth mechanism. 24 Moreover, it can be derived from previous studies [25][26][27] that the faceted IMC is dominated by the two-dimensional nucleation growth mechanism, and the scallop-type IMC is dominated by the rough interface growth mechanism.…”

Epitaxial growth of intermetallic compounds formed at eutectic Sn37Pb/polycrystalline Cu interface during solid-state aging

“…5 shows the dependence of the thickness of interfacial IMCs on the aging time for the two sets of joints. It can be clearly seen that the thickness of the IMCs increases linearly with the square root of the aging time, which is similar to the reaction between most solders and Cu substrate [12][13][14][15]. Generally speaking, the growth kinetics of the IMCs follows the diffusion-controlled Fick's law:…”

“…To date, numerous studies of the solid-state IMC growth have been reported [9][10][11][12][13][14][15]. However, almost all the studies about the interfacial IMCs published to date focus on their crystal structures [9][10][11], growth kinetics [12][13][14][15], and effects on mechanical properties [14,15].…”

“…However, almost all the studies about the interfacial IMCs published to date focus on their crystal structures [9][10][11], growth kinetics [12][13][14][15], and effects on mechanical properties [14,15]. Little information is available about their growth orientations.…”