Interfacial reactions between liquid Sn3.5Ag0.5Cu solders and Ag substrates

The morphology and growth kinetics of intermetallic compounds (IMCs) formed during the soldering reactions between Sn3.5Ag0.5Cu and Ag substrates at various temperatures ranging from 250 to 350 °C were investigated. The interfacial microstructure was quantified with scanning electron microscopy (SEM) for each processing condition. Experimental results show that the thickness of the scallop-shaped Ag3Sn IMCs layer increased with increasing soldering time and temperature. Furthermore, Cu6Sn5 particle precipitates were observed in the Ag3Sn IMCs layer around and thus suppressing the Ag3Sn IMCs layer growth. Furthermore, the large Cu6Sn5 IMCs tend to appear in the vicinity of interfacial wicker-Ag3Sn IMCs. Kinetics analyses showed that growth of the Ag3Sn intermetallic compound was diffusion controlled. The activation energies for the growth of Ag3Sn IMCs are calculated to be 66.7 kJ/mol.

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