In Situ Observation of Liquid Solder Alloys and Solid Substrate Reactions Using High-Voltage Transmission Electron Microscopy

Xin F Tan; Flora Somidin; Stuart D McDonald; Michael J Bermingham; Hiroshi Maeno; Syo Matsumura; Kazuhiro Nogita

doi:10.3390/ma15020510

In Situ Observation of Liquid Solder Alloys and Solid Substrate Reactions Using High-Voltage Transmission Electron Microscopy

Materials (Basel). 2022 Jan 10;15(2):510. doi: 10.3390/ma15020510.

Authors

Xin F Tan^{1

2}, Flora Somidin^{1

2

3}, Stuart D McDonald^{1

2}, Michael J Bermingham², Hiroshi Maeno⁴, Syo Matsumura^{4

5}, Kazuhiro Nogita^{1

2}

Affiliations

¹ Nihon Superior Centre for the Manufacture of Electronic Materials (NS CMEM), School of Mechanical and Mining Engineering, The University of Queensland, St. Lucia, QLD 4072, Australia.
² Advanced Materials Processing and Manufacturing (AMPAM), School of Mechanical and Mining Engineering, The University of Queensland, St. Lucia, QLD 4072, Australia.
³ Centre of Excellence Geopolymer and Green Technology, Faculty of Chemical Engineering Technology, Universiti Malaysia Perlis (UniMAP), Taman Muhibbah, Jejawi, Arau 02600, Perlis, Malaysia.
⁴ The Ultramicroscopy Research Center, Kyushu University, Fukuoka 819-0395, Japan.
⁵ Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Fukuoka 819-0395, Japan.

Abstract

The complex reaction between liquid solder alloys and solid substrates has been studied ex-situ in a few studies, utilizing creative setups to "freeze" the reactions at different stages during the reflow soldering process. However, full understanding of the dynamics of the process is difficult due to the lack of direct observation at micro- and nano-meter resolutions. In this study, high voltage transmission electron microscopy (HV-TEM) is employed to observe the morphological changes that occur in Cu₆Sn₅ between a Sn-3.0 wt%Ag-0.5 wt%Cu (SAC305) solder alloy and a Cu substrate in situ at temperatures above the solidus of the alloy. This enables the continuous surveillance of rapid grain boundary movements of Cu₆Sn₅ during soldering and increases the fundamental understanding of reaction mechanisms in solder solid/liquid interfaces.

Keywords: Cu6Sn5; Pb-free solders; high voltage transmission electron microscopy.

Abstract

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