Key Takeaways & Executive Findings
- •• A novel SnAgCu composite solder with hybrid nano-ZrO2 and micro-T-ZnOw reinforcements was successfully fabricated via ultrasonic-assisted casting. • Surface modification of reinforcements using pyrolysis method ensured a clean interface with no gaps or new phases, promoting atomic inter-diffusion. • The composite solder exhibited a high proportion of eutectic structures and minimal coarse IMCs, enhancing mechanical properties. • Optimal Zn/Zr molar ratio of 2:3 yielded a 30.5% increase in ultimate tensile strength and 47.4% increase in elongation compared to plain Sn1.0Ag0.5Cu solder.
Abstract
A novel SnAgCu composite solder with multi-phase and multi-scale hybrid reinforcement was developed. Initially, surface modification of nano-sized ZrO2 and micro-sized tetra-needle-like ZnO whisker (T-ZnOw) was performed using pyrolysis method. Subsequently, the modified ZrO2 and T-ZnOw were incorporated into Sn1.0Ag0.5Cu composite solders using an ultrasonic-assisted casting method. The microstructure evolution, interface between solder matrix and reinforcements, and mechanical properties were systematically investigated. The results indicated that the composite solder exhibited a high proportion of eutectic structures with minimal coarse intermetallic compounds. Furthermore, at the interface between the reinforcements and Sn1.0Ag0.5Cu, no gaps, micropores, or new phases were observed, while atomic inter-diffusion was detected. When the Zn/Zr molar ratio was set to be 2꞉3, the composite solder achieved an ultimate tensile strength of 35.9 MPa and an elongation of 31.4%, representing improvements of 30.5% and 47.4%, respectively, compared to plain Sn1.0Ag0.5Cu solder.
1. Introduction
SnAgCu series solders are extensively utilized in the interconnection between chip/electronic components and integrated circuits in electronic packaging field due to the comprehensive performance [1,2]. With the emergence of harsh operating conditions and the demand for multifunctional, miniaturized electronic products, electronic packaging has evolved towards integration, miniaturization, and high density [3,4]. Examples include 3D packaging and SiP (system in package) technologies, which demand ultra-fine pitches and reliable bonding [5,6]. Consequently, conventional SnAgCu solders can no longer meet the requirements of next-generation electronic product development. Therefore, there is an urgent need for novel low Ag lead-free solders with high strength and ductility.
To further enhance the performance of lead-free solder, microalloying and composite soldering methods are primarily employed [7−12]. Both methods enhance the properties of the solder matrix. However, the microalloying method suffers from microstructural stability issues, including element segregation and IMC coarse, which degrade solder joint performance and ultimately cause failure [13−15]. Since the reinforcements in composite solders neither react with the solder matrix nor coarsen, composite solders exhibit excellent microstructural stability during long-term service. Consequently, it has become a focal point of research in developing advanced lead-free solders [16−18]. Designing high-strength, high-ductility SnAgCu-based lead-free composite solders is a complex system engineering task, involving the appropriate selection of reinforcements, regulation of the interface between reinforcements and the solder matrix, and optimization of the composite solder preparation method. Addressing the above-mentioned challenges simultaneously is essential to successfully fabricate high-strength, high-ductility lead-free solders.
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Fu-peng HUO, Chuan-tong CHEN, Zhi JIN, Xun-da LIU, Ke-ke ZHANG, Hiroshi NISHIKAWA (2025). Synergistic enhancement of strength−ductility in Sn1.0Ag0.5Cu composite solder via surface-modified nano-sized ZrO2 and micro-sized T-ZnOw hybrid reinforcements. SinoTechIntel Verified Research. https://doi.org/10.1016/S1003-6326(25)67026-9
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Frequently Asked Questions
What is the main innovation of this study?
The study develops a novel SnAgCu composite solder using hybrid reinforcements of surface-modified nano-sized ZrO2 and micro-sized T-ZnOw, achieving synergistic enhancement of strength and ductility.
How were the reinforcements incorporated into the solder?
The reinforcements were surface-modified via pyrolysis method and then incorporated into Sn1.0Ag0.5Cu solder using an ultrasonic-assisted casting method.
What were the key mechanical property improvements?
With a Zn/Zr molar ratio of 2:3, the composite solder achieved an ultimate tensile strength of 35.9 MPa and elongation of 31.4%, representing improvements of 30.5% and 47.4% over plain solder.
What was observed at the interface between reinforcements and solder matrix?
No gaps, micropores, or new phases were observed, and atomic inter-diffusion was detected, indicating a clean and strong interface.
Why is this research significant for electronic packaging?
It addresses the need for high-strength, high-ductility lead-free solders for next-generation electronic packaging, which demands miniaturization and high reliability.
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