Effect of Co content on the microstructure, spreadability, conductivity and corrosion resistance of Sn-0.7Cu alloy. (April 2020)

• Record Type: Journal Article
• Authors: Fan, Jianglei; Liu, Zhanyun; Zhai, Hengtao; Wang, Xiao; Wang, Yan; Li, Ying; Zhou, Xiangkui; Wu, Shen; Liu, Jianxiu
• Is Part Of: Microelectronics and reliability. Volume 107(2020)
• Publication Date: 2020-04
• Subjects: Lead-free solder -- Sn-0.7Cu -- Microstructure -- Spreadability -- Conductivity -- Corrosion resistance; Electronic apparatus and appliances -- Reliability -- Periodicals; Miniature electronic equipment -- Periodicals; Appareils électroniques -- Fiabilité -- Périodiques; Équipement électronique miniaturisé -- Périodiques; Electronic apparatus and appliances -- Reliability; Miniature electronic equipment; Periodicals; 621.3815
• DOI: 10.1016/j.microrel.2020.113615
• Languages: English
• ISSNs: 0026-2714

Abstract

Abstract: The effect of Co content on the microstructure, spreadability, conductivity and corrosion resistance of Sn-0.7Cu (mass%, mass fraction except specified) based lead-free solder was studied in this paper. With the addition of Co, the microstructure of Sn-0.7Cu- x Co ( x = 0.5, 1.0, 1.5, 2.0) alloy consists of Cu6 Sn5, CoSn2 intermetallics, and β -Sn matrix. The morphology of CoSn2 phase changes from small blocks to flake like, short rod-like, and then to massive bulk shape with the increase of Co content. A small amount of CoSn phase formed in Sn-0.7Cu-2.0Co solder alloy. Adding Co reduce the spreading area of Sn-0.7Cu solder alloy slightly. The spread area decreases with the increase of Co content from 0.5% to 1.5%, and then increases again with the addition of 2.0% Co. Sn-0.7Cu-0.5Co solder obtains the largest spreading area among the Sn-0.7Cu- x Co solders. The thickness of reaction layer between Sn-0.7Cu- x Co solder alloys and copper plate is increased with the increase of Co content. The conductivity of the Sn-0.7Cu alloy decreases with the increase of Co content, but the leave of decrease is acceptable. Meanwhile, corrosion resistance of Sn-0.7Cu solder alloy is improved with the addition of Co under salt spray atmosphere. The mass loss rate of Sn-0.7Cu- x Co solder alloy decreases with the increase of Co content. Highlights: Co promotes the formation of CoSn2 phase in Sn-0.7Cu solder. Spread area of Sn-0.7Cu- x Co decreases first then increases with increase Co content. Conductivity of the Sn-0.7Cu alloy decreases slightly with the increase of Co content. Improved corrosion resistance Sn-0.7Cu solder with addition of Co under salt spray Mass loss rate of Sn-0.7Cu- x Co solder decreases with the increase of Co content.