Overview

A copper spring contact is a thin, high-conductivity elastic component photochemically etched from copper-alloy foil, used as a battery tab, connector finger, grounding spring, shielding finger or the moving contact of a tact switch. Instead of being punched, the part is defined by a photoresist mask: cantilever beams, multi-finger arrays, stress-relief slots and half-etched bend lines are exposed and developed on both faces, then the unprotected alloy is dissolved in a controlled etchant. The result is a flat, burr-free spring with no roll-over, no work hardening and no springback distortion. Stock is usually beryllium copper C17200, phosphor bronze C51900/C52100, brass C2600 or copper-nickel-tin, most often 0.10–0.30 mm thick, balancing restoring force against current-carrying capacity.

For sourcing and mechanical engineers, the appeal is consistency and safe assembly. A stamping die leaves burrs on fine fingers that can scrape the mating plating, jam the counterpart or shed particles that cause a short, and thin-gauge stamping introduces springback and twist that make contact force drift from piece to piece. Chemical removal carries no punch stress, so beam width and finger gap stay uniform across a full sheet and contact force and travel hold tightly within a batch. A new part number needs only a new phototool: engineering samples ship in days, and elasticity, plating and tape-and-reel packaging can all be validated at the prototype stage before parameters are locked for volume.

Parameter Window

• Available Materials: beryllium copper C17200, phosphor bronze C51900/C52100, brass C2600, CuNiSn, C1100 copper
• Material Thickness Range: 0.05–0.80 mm (springs most often 0.10–0.30 mm)
• Tolerance: ±0.02 mm on beam width, ±0.03 mm on finger pitch, ±0.05 mm on outer profile
• Minimum Feature: 0.08 mm finger width / 0.15 mm gap at 0.15 mm stock, plus half-etch bend lines
• Surface Options: Ni, Au, Sn or Ag plating, BeCu age hardening, anti-tarnish, tape-and-reel packing
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Alloy & Temper Selection — Choose BeCu or phosphor bronze for the target force and conductivity, then fix temper, hardness and gauge.
2. Artwork & Phototool — Draw cantilevers, multi-finger arrays, relief slots and half-etch bend lines, compensating finger width for undercut.
3. Cleaning & Lamination — Degrease and micro-etch the foil, then laminate dry-film resist on both faces so no bubble sits under a fine finger.
4. UV Exposure — Expose a high-resolution phototool registered to the sheet datum for accurate finger-array position.
5. Development & Inspection — Develop and inspect fingers and gaps under magnification for residue or broken lines before etching.
6. Controlled Etching — Spray copper-alloy chemistry, holding finger width and sidewall straightness by time, temperature and conveyor speed.
7. Stripping & Heat Treat — Strip resist, age-harden BeCu to restore spring properties, then plate Ni, Au or Sn for conductivity and wear.
8. Forming & Verification — Bend to shape if required, measure contact force, springback, flatness and plating thickness, then pack on tape or trays.

Core Advantages

1. Burr-free mating face: Chemical removal leaves no piercing burr or roll-over, so fingers never scrape the mating plating or shed conductive debris.
2. Complex springs in one pass: Multi-finger arrays, shaped cantilevers and relief slots form in the same etch cycle without a family of dies.
3. Accurate bend location: Half-etched thinning lines put the bend into the material, giving consistent angles and low springback.
4. No hard tooling: A new part is a new phototool, so pilot runs and frequent revisions stay fast and economical.
5. Spring plus conductivity: Copper alloys combine restoring force and current capacity, with Au, Ni or Sn plating to suit the contact environment.
6. Sample-to-volume continuity: copper spring contact prototypes and production run on one line, so the signed sample sets the contact-force standard.

Typical Applications

• Battery tabs: Positive and negative contacts for handheld devices, etched thin and nickel plated for stable spring force.
• Board-to-board connectors: Dense multi-finger arrays with fine pitch and uniform height for high-density signal and power links.
• Grounding & shielding fingers: Elastic fingers across enclosure gaps, providing EMI shielding and low-impedance bonding.
• Tact switch domes: Ultra-thin moving contacts with short travel and consistent feel across the service life.
• Charging & pogo contacts: Spring contacts in cradles and magnetic docks, gold plated to resist mating wear and sweat.
• Antenna springs: Elastic feed points between RF modules and the main board, small enough for automated placement.

Design Notes & Process Considerations

1. Fix material state first: Select BeCu or phosphor bronze grade by force, fatigue life and conductivity, then set temper and aged hardness.
2. Beam aspect ratio: Match cantilever length and width to stock thickness; too slender yields on assembly, too wide loses spring.
3. Finger gap and undercut: Size the finest finger and gap against thickness with allowance for side etch, to avoid bridging or broken fingers.
4. Bend-line depth: Call out half-etch depth as a fraction of thickness; too deep tears, too shallow increases springback.
5. Force and plating: State contact force over working deflection and name the plating system, including Ni underplate and Au thickness.
6. Panel & tape layout: copper spring contact designs benefit from shared datums and a panel grid matched to tape-and-reel feeders.