Bimetal Contact Rivets: Construction, Benefits & Applications (2026 Guide)

Bimetal contact rivets are the industry standard for cost-effective electrical switching. By bonding a thin layer of precious silver alloy to a copper or steel base, manufacturers achieve the electrical performance of silver at a fraction of the material cost—typically reducing silver usage by 60–80% compared to solid contact rivets.

Whether you are sourcing contact components for relay production, evaluating electrical contacts for a new switch design, or transitioning from solid to composite construction for cost optimization, understanding how bimetal contact rivets are manufactured and where they perform best is essential.

In this guide, we explain the construction, bonding methods, benefits, limitations, and key applications of bimetal contact rivets across the electrical engineering industry.

—

What Is a Bimetal Contact Rivet?

A bimetal contact rivet is a composite fastener consisting of two distinct metal layers: a contact face made from a silver alloy (such as AgSnO₂, AgNi, or pure silver) bonded to a base material (typically copper, brass, CuNi, or steel). The rivet geometry allows automated installation by staking, resistance welding, or orbital riveting onto carrier blades, springs, or terminals.

Unlike solid silver rivets where the entire component is precious metal, bimetal rivets place silver alloy only where the electrical arc occurs—the contact face—while the base provides structural support, electrical conductivity, and thermal dissipation at a much lower cost.

Typical Dimensions

Feature Typical Range Notes
Head Diameter 2.5–8.0 mm Larger heads for high-current applications
Face Thickness 0.3–0.7 mm Silver alloy layer; determines arc life
Shank Diameter 1.2–4.0 mm Matched to carrier hole and staking equipment
Shank Length 0.6–25+ mm Customizable for blade thickness and forming
Base Material Cu, Brass, CuNi, Steel Copper for conductivity; steel for magnetic applications

—

How Bimetal Contact Rivets Are Manufactured

Cold Bonding (Cold Heading)

The most common manufacturing method for high-volume bimetal contact rivets is cold bonding on multi-station forming machines:

  1. Wire feeding: Silver alloy wire and base material wire are fed simultaneously into the forming station.
  2. End facing: The silver wire end is squared to ensure clean bonding surface.
  3. Upsetting: The silver end is upset (compressed) to form a flat face, while the base wire is prepared for shank formation.
  4. Bonding: High pressure creates a metallurgical bond between the silver face and base material without heating.
  5. Heading: The combined billet is headed into the final rivet shape—round head, flat head, or custom geometry.
  6. Cut-off: The rivet is cut to length and ejected for inspection.

Cold bonding produces a strong, reliable interface with bond shear strengths typically exceeding 80 MPa. The process operates at speeds up to 300 rivets per minute, making it ideal for mass production.

Internal Oxidation + Bonding

For AgSnO₂ and other metal-oxide contact materials, an alternative process involves:

  1. Producing a silver-tin alloy billet by casting or powder metallurgy.
  2. Internal oxidation to convert tin to SnO₂ within the silver matrix.
  3. Bonding the oxidized face material to the copper base using rolling or extrusion.
  4. Heading the composite wire into final rivet form.

This method produces finer, more uniform oxide distribution, improving arc resistance and contact consistency.

Resistance Welding Attachment

In some applications, pre-formed solid silver contact tips are resistance-welded onto copper or steel carriers rather than formed as integral rivets. While not technically “rivets,” these welded contacts serve the same function and are often grouped under the bimetal contact category.

—

Benefits of Bimetal Contact Rivets

1. Cost Reduction

The primary advantage of bimetal construction is material cost savings. Silver prices have historically ranged from $20–$30 per troy ounce, while copper costs approximately $0.20–$0.30 per ounce. By replacing 60–80% of the silver volume with copper or steel, bimetal rivets reduce material costs proportionally.

For a relay manufacturer consuming millions of contacts annually, this cost difference directly impacts product competitiveness.

2. Optimized Material Utilization

In a switching device, only the contact face experiences arcing and mechanical wear. The shank and base serve primarily as electrical and thermal conductors. Bimetal construction places expensive silver alloy precisely where it is needed—nothing more, nothing less.

3. Good Electrical and Thermal Performance

Copper bases provide excellent electrical conductivity (100% IACS) and thermal conductivity (400 W/m·K), ensuring efficient heat dissipation from the contact interface. This reduces temperature rise during continuous operation and extends contact life.

4. Mechanical Strength

The base material provides the mechanical strength needed for staking, welding, and vibration resistance. Steel bases offer additional magnetic properties useful in certain relay designs, while copper and brass bases optimize conductivity.

5. Design Flexibility

Bimetal rivets can be produced with various face/base combinations:

Face Material Base Material Application
AgSnO₂ Cu / CuNi Motor controls, EV charging, contactors
AgNi Cu / Brass Household relays, appliance switches
Pure Ag Cu Signal relays, precision switches
AgW Cu High-voltage breakers
AgC Cu DC switching, EV pre-charge

—

Limitations and Considerations

Bond Integrity

The metallurgical bond between face and base must withstand:

  • Thermal cycling (expansion/contraction during switching)
  • Mechanical stress from staking and vibration
  • Electromigration under DC current

Poor bonding can lead to delamination, increased contact resistance, and premature failure. Quality control through shear testing and metallographic inspection is essential.

Galvanic Corrosion

When dissimilar metals are joined in the presence of moisture or contaminants, galvanic corrosion can occur at the interface. Silver-copper bonds are generally stable in dry environments but may require protective coatings or encapsulation in harsh conditions (marine, chemical, outdoor).

Current Density at Interface

Current must transfer from the face to the base through the bonded interface. If the bond area is too small or the bond resistance is high, localized heating can occur. Proper face thickness and bond quality control prevent this issue.

—

Key Applications

Power Relays and Contactors

Bimetal AgSnO₂/Cu and AgNi/Cu rivets dominate the power relay market. The combination of arc-resistant silver faces and conductive copper bases delivers the required electrical life (100,000–1,000,000 operations) at competitive cost.

Circuit Breakers

Molded-case circuit breakers (MCB, MCCB) use bimetal contacts for both the main current path and trip mechanisms. The high conductivity of copper bases ensures low voltage drop under rated current, while silver faces handle fault interruption.

Automotive Relays

Modern vehicles contain 20–40 relays controlling lighting, HVAC, fuel pumps, and power windows. Bimetal contacts meet automotive cost targets while delivering the reliability required for 15-year vehicle life.

Household Appliances

Washing machines, dishwashers, and air conditioners use bimetal contacts in thermostat controls, motor relays, and heater switches. Cost-sensitive designs favor AgNi/Cu combinations.

Solar Inverters and Energy Storage

Solar string inverters and battery management systems (BMS) use bimetal AgSnO₂ contacts in DC contactors that switch daily over 20+ year design lives.

—

How to Specify Bimetal Contact Rivets

When specifying bimetal contact rivets for your application, consider:

  1. Face material: Match to your load type (AgSnO₂ for inductive, AgNi for resistive, pure Ag for signal).
  2. Face thickness: 0.3–0.5 mm for light-duty; 0.5–0.7 mm for heavy-duty.
  3. Base material: Copper for conductivity; steel for magnetic or structural needs.
  4. Head geometry: Round head for general use; flat head for space-constrained designs.
  5. Bond strength: Specify minimum shear strength (typically ≥80 MPa).
  6. Regulatory compliance: Ensure RoHS and REACH compliance for face and base materials.
  7. Installation method: Confirm compatibility with your staking or welding equipment.

—

Conclusion

Bimetal contact rivets represent one of the most important innovations in electrical contact manufacturing. By combining the arc resistance and conductivity of silver alloys with the strength and economy of copper or steel bases, they enable high-performance switching at a fraction of the cost of solid silver alternatives.

For most relay, switch, and contactor applications, bimetal construction offers the optimal balance of performance, reliability, and cost. Understanding the manufacturing methods, benefits, and limitations empowers engineers and procurement teams to specify the right contact solution for their products.

—

Get a Quote for Bimetal Contact Rivets

At ContactRivets, we manufacture bimetal contact rivets in standard and custom configurations. Our capabilities include:

  • Face materials: AgSnO₂, AgNi, pure silver, AgW, AgC
  • Base materials: Copper, brass, CuNi, steel
  • Head geometries: Round, flat, flanged, grooved
  • Custom dimensions and tolerances
  • RoHS- and REACH-certified materials
  • High-volume production with consistent quality

Contact us today for samples, technical datasheets, and competitive quotations.

—

Related Articles