AgSnO2 vs AgNi vs AgCdO: Which Contact Material Is Right for You?
Choosing the right contact material is one of the most important decisions in relay, switch, and contactor design. The wrong material leads to premature failure, excessive warranty claims, or regulatory non-compliance.
This side-by-side comparison of the three most common silver-based contact materials helps you select the optimal alloy for your specific application.
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Quick Comparison Table
| Property | AgSnO2 | AgNi | AgCdO |
|---|---|---|---|
| Conductivity | Moderate | High | Moderate |
| Arc resistance | Excellent | Poor | Excellent |
| Anti-welding | Excellent | Poor | Excellent |
| Contact resistance | 2–5 mΩ | <2 mΩ | 1–3 mΩ |
| Mechanical ductility | Low | High | Moderate |
| Cost | Medium | Low | Medium |
| RoHS compliance | Yes | Yes | No (Cd) |
| Best for | Inductive/motor | Resistive/light | Legacy only |
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When to Choose AgSnO2
Choose AgSnO2 when switching inductive loads, high inrush currents, DC switching, frequent switching, anti-welding is critical, or RoHS compliance is required.
Typical applications: EV charging relays, industrial contactors, motor starters, solar inverter contactors, automotive power relays.
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When to Choose AgNi
Choose AgNi when switching resistive loads, low current with minimal arcing, cost is a primary constraint, complex geometries requiring high formability, or signal/auxiliary relays.
Typical applications: Household appliance relays, signal relays, timer contacts, light-duty switches.
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When AgCdO Was Used (Legacy)
AgCdO was historically chosen for heavy inductive loads and maximum anti-welding performance. It is being phased out due to cadmium toxicity and RoHS II restrictions with the general-use exemption expiring July 2025.
Migration path: Replace AgCdO with AgSnO2 of equivalent or higher oxide content.
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Cost Comparison
| Material | Relative Cost |
|---|---|
| AgNi 90/10 | 1.0× (baseline) |
| AgSnO2 90/10 | 1.2–1.4× |
| AgCdO 90/10 | 1.2–1.4× |
| Pure Ag | 1.0–1.1× |
Important: Material cost is only one factor. Total cost of ownership includes contact life, warranty claims, and field failures.
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Conclusion
For new designs in 2025 and beyond, the choice is essentially between AgSnO2 and AgNi. AgCdO should no longer be specified due to RoHS restrictions.
- AgSnO2 is the default for inductive, high-inrush, and DC applications.
- AgNi remains the economical choice for resistive, low-current, and signal applications.
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