Nucleation and growth of Ag3Sn in Sn-Ag and Sn-Ag-Cu solder alloys

Journal article

This study addresses the critical need for lead-free solder alternatives in electronic manufacturing by investigating the microstructural characteristics of Sn-Ag solder alloys, focusing on the Ag3Sn intermetallic phase. Utilizing Small-Angle Neutron Scattering (SANS), the study explored the phase interface and grain structure within Sn-Ag alloy to identify attributes that influence mechanical stability and performance. The research was structured around a comprehensive SANS analysis, complemented by Electron Backscatter Diffraction (EBSD) to expose the morphology and orientation of crystalline phases within the material. The investigation revealed distinct scattering patterns indicative of a multi-phase structure with a homogeneous distribution of fine Ag3Sn precipitates within a β-Sn matrix. EBSD data confirmed these findings, showing a wide range of grain sizes and a random orientation distribution that matches theoretical models for polycrystalline materials. Notably, the SANS data uncovered a specific size distribution of the Ag3Sn phase, which was characterized by a sharp interface contrast against the β-Sn matrix, pivotal for understanding the solder's mechanical properties. Interpretation of the SANS and EBSD data sets suggests that the Sn-Ag alloy's performance is significantly influenced by the dispersion and morphology of the Ag3Sn phase. The presence of nanoscale Ag3Sn structures, exhibiting a needle-like surface, implies a material optimized for mechanical reinforcement, which is essential for robust electronic connections. The integrated approach offers a novel perspective on the nano structural arrangement of lead-free solders, contributing to the advancement of safer, more reliable electronic materials. The findings have significant implications for the development of next-generation electronic components, reinforcing the transition to environmentally benign manufacturing processes.

Authors: Cui, Y; Xian, JW; Zois, A; Marquardt, K; Yasuda, H

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Elsevier
• Journal: Acta Materialia
• Volume: 249
• Pages: 118831-118831
• Article number: 118831
• Publication date: 2023-03-06
• DOI: 10.1016/j.actamat.2023.118831
• EISSN: 1873-2453
• ISSN: 1359-6454
• Language: English
• Keywords: Nucleation; Branching (polymer chemistry); Composite material; Layer (electronics); Copper; Materials science; Supercooling; Metallurgy; Thermodynamics; Crystallography; Soldering