Interfacial Reactions in Sn/Ag/Cu Sandwiched Structure

Sn/Ag/Cu sandwiched structures were fabricated to investigate the intermetallic compound growth at the contact interfaces. The Ag layer was prepared using electrodeposition with direct current (DC) and pulse current (PC). The DC-Ag exhibited a coarse-grained structure but the PC-Ag had a fine-grained structure. After the 6-µm-thick Ag layer was completely consumed to form Ag3Sn at 200 °C, the CU<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf>Sn<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf>and CU<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>Sn phases started to form at the Ag<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>Sn/Cu interface. The Ag<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>Sn phase formed in the PC-Ag case exhibited a smaller grained structure, offering a high density of grain boundary to facilitate the downward diffusion of Sn. As a result, the Cu-Sn phases grew at a faster rate in the PC-Ag case. The Ag<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>Sn phase shrank slightly, releasing Sn to support the growth of the Cu-Sn phases.