title: In situ imaging of microstructure formation in electronic interconnections.
abstract: The development of microstructure during melting, reactive wetting and solidification of solder pastes on Cu-plated printed circuit boards has been studied by synchrotron radiography. Using Sn-3.0Ag-0.5Cu/Cu and Sn-0.7Cu/Cu as examples, we show that the interfacial Cu6Sn5layer is present within 0.05 s of wetting, and explore the kinetics of flux void formation at the interface between the liquid and the Cu6Sn5layer. Quantification of the nucleation locations and anisotropic growth kinetics of primary Cu6Sn5crystals reveals a competition between the nucleation of Cu6Sn5in the liquid versus growth of Cu6Sn5from the existing Cu6Sn5layer. Direct imaging confirms that the β-Sn nucleates at/near the Cu6Sn5layer in Sn-3.0Ag-0.5Cu/Cu joints.
authors.affiliation: Nihon Superior Centre for the Manufacture of Electronic Materials (NS CMEM), School of Mechanical and Mining Engineering, The University of Queensland, 4072 St Lucia, Queensland, Australia.|Centre of Excellence Geopolymer and Green Technology, School of Materials Engineering, Universiti Malaysia Perlis (UniMAP), Taman Muhibbah 02600, Jejawi, Arau, Perlis, Malaysia.|Department of Materials, Imperial College, London SW7 2AZ, United Kingdom.
authors.forename: M A A Mohd
authors.initials: MA
authors.lastname: Salleh
authors.affiliation: Department of Materials, Imperial College, London SW7 2AZ, United Kingdom.
authors.forename: C M
authors.initials: CM
authors.lastname: Gourlay
authors.affiliation: Department of Materials, Imperial College, London SW7 2AZ, United Kingdom.
authors.forename: J W
authors.initials: JW
authors.lastname: Xian
authors.affiliation: Department of Materials, Imperial College, London SW7 2AZ, United Kingdom.
authors.forename: S A
authors.initials: SA
authors.lastname: Belyakov
authors.affiliation: Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Yasuda
authors.affiliation: Nihon Superior Centre for the Manufacture of Electronic Materials (NS CMEM), School of Mechanical and Mining Engineering, The University of Queensland, 4072 St Lucia, Queensland, Australia.
authors.forename: S D
authors.initials: SD
authors.lastname: McDonald
authors.affiliation: Nihon Superior Centre for the Manufacture of Electronic Materials (NS CMEM), School of Mechanical and Mining Engineering, The University of Queensland, 4072 St Lucia, Queensland, Australia.
authors.forename: K
authors.initials: K
authors.lastname: Nogita