Welding reactions of lead free solder alloy for aluminum packaging electronic devices

In this study, we presented welding process between Rogers laminates and aluminum substrate with SAC305 alloy. The samples were characterized in terms of temperature cycling test, mechanical shock test and constant acceleration test. The characterizations were performed by using field emission scanning electron microscope, and the compositions were identified by energy dispersive spectroscopy. The results showed that some interesting changes of the solder layer took place after the test. Before the test, the thickness of solder was uniform and about 40 µm; the IMC layer was not obvious; there were voids in the solder itself and solders joints, but no cracks were found. After the test, the thickness of solder changed slightly; the IMC layer was obvious and the thickness was about 6 µm; the voids in the solder grew bigger, but there were no cracks yet. The intermetallic compounds of tree-like morphology run through the solders and the main composition was Au-Sn-Ni alloy. In the test each layer diffused to solder at different levels, but the degree of Au, Ni and Ag diffusion was the most prominent.