Abstract
The thermal properties and interfacial reaction between the Sn-9Zn-xAg lead-free solders and Cu substrate, such as solidus and liquidus temperatures, heat of fusion, intermetallic compounds, and adhesion strength, have been investigated. Two endothermic peaks appear in the DSC curve when the Ag content in the Sn-9Zn-xAg solder alloy is above 1.5 wt pct. The solidus temperatures of the Sn-9Zn-xAg solder alloys are around 197 °C, but the liquidus temperatures decrease from 225.3 °C to 221.7 °C and 223.6 °C with increasing the Ag content in the solder alloy from 1.5 to 2.5 and 3.5 wt pct, respectively. Three intermetallic compounds, namely, Cu6Sn5, Cu5Zn8, and Ag3Sn are observed at the Sn-9Zn-xAg/Cu interface. The Cu5Zn8 is formed close to the Cu substrate, Ag3Sn is adjacent to it, and Cu6Sn5 is nearest the Sn-9Zn-1.5Ag solder alloys. A bi-structural Cu6Sn5 layer with hexagonal η-Cu6Sn5 and monoclinic η′-Cu6Sn5 is found at the Sn-9Zn-1.5Ag/Cu interface due to Ag dissolution. A maximum adhesion strength of 10.7±0.8 MPa is obtained at the Sn-9Zn-2.5Ag/Cu interface as soldered at 250 °C for 30 seconds.
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Chang, TC., Wang, MC. & Hon, MH. Thermal properties and interfacial reaction between the Sn-9Zn-xAg lead-free solders and Cu substrate. Metall Mater Trans A 36, 3019–3029 (2005). https://doi.org/10.1007/s11661-005-0074-7
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DOI: https://doi.org/10.1007/s11661-005-0074-7