Interfacial Behavior During Reactions Between Sn and Electroplated Co-Zn Alloys.
Chao-Hong Wang1, Che-Yang Lin1
1Department of Chemical Engineering, National Chung Cheng University, Chiayi 621301, Taiwan.
Materials (Basel, Switzerland)
|June 27, 2025
Summary
Adding zinc (Zn) to cobalt (Co) electroplating coatings significantly alters intermetallic compound (IMC) formation with tin (Sn) solder. Higher Zn content effectively suppresses IMC growth, enhancing interfacial stability.
Area of Science:
- Materials Science
- Electrochemistry
- Surface Engineering
Background:
- Cobalt-tin (Co-Sn) intermetallic compounds (IMCs) are critical in electronic packaging.
- Controlling IMC formation is essential for reliable solder joint performance.
- Electroplating offers a versatile method for fabricating Co-Zn alloy coatings.
Purpose of the Study:
- To investigate the electroplating characteristics of Co-Zn alloy coatings.
- To examine the influence of varying Zn content on IMC formation with Sn solder.
- To evaluate the interfacial stability of Co-Zn/Sn solder joints.
Main Methods:
- Fabrication of Co-Zn alloy coatings via electroplating with controlled Zn concentrations.
- Analysis of coating morphology, microstructure, and crystallinity using advanced techniques.
- Investigation of liquid-state (250 °C) and solid-state (160 °C) interfacial reactions with Sn solder.
Main Results:
- Anomalous co-deposition of Zn over Co observed during electroplating.
- Zn incorporation disrupts Co crystallinity, leading to decreased crystallinity and amorphization.
- Higher Zn content significantly reduces IMC formation, particularly in solid-state reactions (>85% suppression).
- Co-Zn coatings exhibit improved interfacial stability with Sn solder.
Conclusions:
- Zn doping is an effective strategy to control and suppress CoSn3 IMC formation.
- Co-Zn alloy coatings enhance interfacial stability in Sn solder joints.
- Optimized Co-Zn coatings hold promise for advanced electronic packaging applications.
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