Microstructure and Properties of Bi-Sn, Bi-Sn-Sb, and Bi-Sn-Ag Solder Alloys for Electronic Applications
Year: 2025
Type: article
Abstract: The Bi-Sn, Bi-Sn-Ag, and Bi-Sn-Sb solder alloy systems represent lead-free, environmentally friendly alternatives for reliable electronic assembly. These alloys comply with increasingly strict environmental and health regulations, while offering low melting points suitable for soldering temperature-sensitive components. The addition of Ag or Sb improves mechanical strength, hardness, wear resistance, and thermal stability. Microstructural analysis confirmed homogeneous, defect-free surfaces. Comprehensive microstructural characterization using optical microscopy, SEM, EDS, and BSE imaging revealed refined, heterogeneous microstructures with distinct phase segregation. Dendritic growth, eutectic formations, and intermetallic compounds were observed. Sb addition promoted granular intermetallics, while Ag induced needle-like precipitates along phase boundaries. EDS confirmed expected compositions, and BSE imaging enhanced contrast between Bi-, Sn-, Sb-, and Ag-rich regions. The study also reports the thermal and electrical conductivities of Bi60Sn40, Bi60Sn35Ag5, and Bi60Sn35Sb5 alloys over the 25–140 °C range. Bi60Sn40 showed an increase in thermal conductivity from 16.93 to 26.93 W/m·K, while Bi60Sn35Ag5 reached 18.28 W/m·K at 25 °C, and Bi60Sn35Sb5 exhibited 13.89 W/m·K. These findings underline the critical influence of alloying elements on microstructure, phase stability, and thermophysical behavior, supporting their application in low-temperature soldering technologies.
Source: Metals
DOI: 10.3390/met15080915
Authors: Andrei-Alexandru Ilie, Florentina Niculescu, Gheorghe Iacob, Ion Pencea, Florin Miculescu, Robert Bololoi, Dumitru-Valentin Drăguț, Alexandru-Cristian Matei, Mihai Ghiţă, Adrian Priceputu, Constantin Ungureanu
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,137
OpenAlex ID: W4413331043