Interfacial Reactions and Reliability of Sn-Zn-Bi-XCr Solder Joints with Cu Pads

摘要

In this paper, the interfacial reactions of Sn-8Zn-3Bi and Sn-8Zn-3Bi-0.3Cr solders with Cu pads and the growth of IMCs during long-term aging treatment were presented and discussed. Less than 3μm Cu{sub}5Zn{sub}8 IMC layer was found at the Sn-8Zn-3Bi-(0.3)Cr/Cu during the reflow at 230°C for 1 min. During solid state aging treatment at 150°C for 4, 9, 16, 25 days, the Cu{sub}5Zn{sub}8 IMC grown up with the extension of aging time, some of the IMCs were scattered into the bulk solders, Zn-poor layer was observed in the Sn-8Zn-3Bi solder joints. In the case of Cr-containing solders, the thickness of Cu{sub}5Zn{sub}8 IMC growth was much thinner than that of in the Sn-8Zn-3Bi solder joints, and no significant Zn-poor layer was found in Cr-containing solders. The growth rate of IMCs at the Sn-8Zn-3Bi-0.3Cr/Cu interface was about 1/2 times than that of in the Sn-8Zn-3Bi solder. During long-term aging, solid phase transition happened in Cr-containing solders, which indirectly and effectively controlled the diffusion of Zn atom to the interface, and thus slowed down the growth rate of Cu-Zn IMCs. It was supposed that Cr-containing Sn-Zn-Bi solders performed better long-term solder joint reliability.