Overview

An etched spring contact is a flat, flexible contact finger cut from thin conductive alloy by photochemical machining. A photoresist is laminated, exposed with the finger profile and developed, then the unprotected metal is dissolved to leave the cantilever arm, tip and solder or mounting pad in one piece. Common materials are beryllium copper (C17200), phosphor bronze (C5191) and 300-series stainless steel, supplied between 0.05 mm and 0.4 mm thick. Because the profile is chemically removed rather than die-stamped, the etched edges are smooth and stress-free, with no burrs or micro-cracks to degrade electrical performance or fatigue life.

For connectors, sockets and battery interfaces, the contact must press against its mating surface with a controlled force while keeping resistance low over many insertion cycles. Etching lets the beam width, length and thickness be tuned precisely, so every finger in a batch deflects with the same force and travel. The flat, clean surface plates evenly, and the stress-free edge resists fatigue, keeping contact resistance stable across the product lifetime. This is why an etched spring contact is specified for high-density connectors and test sockets where stamped or wire-formed contacts cannot hold the same dimensional control.

Parameter Window

• Available Materials: beryllium copper (C17200), phosphor bronze (C5191), stainless steel 301
• Material Thickness Range: 0.05–0.4 mm
• Tolerance: ±0.01 mm on beam width, ±0.05 mm on finger length
• Minimum Feature: 0.05 mm beam width, 0.08 mm slot width
• Surface Options: gold plating, nickel plating, tin plating, passivation
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Contact Design — Convert the finger profile to vector artwork and check beam width, length and tip geometry against the mating pad.
2. Material Selection — Choose beryllium copper for low resistance and high spring, phosphor bronze for economy, stainless for corrosion.
3. Cleaning & Lamination — Degrease the sheet and laminate dry film with no bubbles so the fingers etch clean and straight.
4. UV Exposure — Expose the contact profile registered to the sheet edge for accurate tip-to-pad length.
5. Development — Wash out the unexposed resist to open the fingers, then inspect for under-developed narrow slots.
6. Etching — Spray etch at controlled temperature; finger width is set by time, pressure and conveyor speed.
7. Stripping & Finishing — Remove resist, neutralize, then plate gold, nickel or tin on the contact face.
8. Inspection & Packaging — Verify finger width, length and flatness, then pack on trays to protect the flexible arms.

Core Advantages

1. Controlled force: Beam dimensions are held to microns, so deflection force and travel repeat across every finger.
2. Low contact resistance: The flat, smooth surface plates uniformly and makes a stable, low-resistance contact.
3. High fatigue life: Stress-free etched edges resist cracking, so the finger survives many insertion cycles.
4. Fine pitch: Fingers down to 0.05 mm wide support high-density, fine-pitch connector designs.
5. No tooling cost: Each revision is a new film, keeping prototype and short runs economical.
6. Batch consistency: Every finger on a sheet etches at the same rate, so spring force stays uniform.

Typical Applications

• Board-to-board connectors: Contact fingers for high-density interconnects.
• Battery contacts: Leaf-spring fingers for coin-cell and rechargeable packs.
• Test sockets: Flexible contacts that grip IC pins and packages repeatedly.
• FPC connectors: Fine contact fingers for flexible printed circuit interfaces.
• Grounding contacts: EMI spring fingers for chassis and shielding contact.
• SIM and card readers: Low-profile contacts for card detection and readout.

Design Notes & Process Considerations

1. Beam versus force: Tune beam width, length and thickness to reach the target normal force; small changes shift deflection sharply.
2. Fatigue margin: Keep working stress below the endurance limit and add stress relief where fingers are long.
3. Plating callout: Name the plating and thickness on the contact face to hold resistance stable over life.
4. Insertion life: Specify the required mating cycles so the material and geometry are sized for it.
5. Edge condition: Require burr-free, crack-free edges, since edge defects are where fatigue begins.
6. Forming: State whether the contact is used flat or formed; etching suits flat profiles, with forming added downstream.