Medium- and low-voltage relays are widely used in industrial control, home appliances, automotive electronics, and other fields. Their operating voltages typically range from tens of volts to 1,000 volts, with currents ranging from milliamps to tens of amperes. As the core components of relays, the materials and structures of contacts directly affect product reliability and service life. Faced with the three mainstream silver-based contact types—solid rivet, bimetal rivet, and trimetal rivet—how can you make an accurate selection? This article provides a detailed analysis.

Technical Characteristics of the Three Contact Types

1. Solid Rivet

• Structure: Cold-forged from a single silver alloy material (such as pure silver, fine-grained silver, or silver-nickel) in a single piece.
• Advantages: Highest electrical conductivity (pure silver can reach 106% IACS), extremely low and stable contact resistance; simple manufacturing process, suitable for mass production.
• Disadvantages: High consumption of precious metals, resulting in higher costs; some silver alloys (such as silver-tin oxide) are difficult to form into solid rivetsdue to severe work hardening.
• Applications: Low-power signal relays, precision instrument relays, and applications with stringent contact resistance requirements.

2. Bimetal rivets

• Structure: Composed of two layers—a “silver alloy working layer” and a “copper matrix”—with the thickness of the working layer customizable to meet specific requirements.
• Advantages: Saves over 50% in precious metal usage, offering high cost-effectiveness; the working layer can utilize various silver alloys (such as silver-nickel or silver-tin oxide) to balance performance and cost; the copper matrix provides good weldability, facilitating subsequent assembly.
• Disadvantages: The strength of the composite interface must be strictly controlled; poor-quality bonding may lead to delamination.
• Applications: General-purpose medium-power relays, AC contactors, and automotive relays; the mainstream choice in industrial control applications.

3. TrimetalRivets

• Structure: Features a three-layer symmetrical structure of “silver alloy + copper + silver alloy,” or an asymmetrical composite with different materials at both ends.
• Advantages: Materials can be optimized separately for different loads at each end of the contact (e.g., one moving, one stationary); offers the best resistance to welding and ablation; suitable for harsh operating conditions requiring high current and long electrical life.
• Disadvantages: Complex manufacturing process; higher cost than dual-composite designs.
• Applications: High-power relays, high-voltage DC relays, and relays for motor loads with frequent on-off cycling.