Overview

Spring sheet chemical etching forms contacts, clips and leaf springs from 301/304 stainless in spring temper or beryllium copper C17200, between 0.05 and 0.5 mm thick, without cutting heat or force into the material. A photoresist mask defines the outline, and the unprotected metal is dissolved so edges come out burr-free and free of the micro-cracks that a punched edge leaves behind. That matters because a spring fails at its stress risers: a clean etched edge keeps the elastic response and fatigue life the temper was chosen for. Half-etched bend lines or thinned flexure zones can be added in the same bath.

Unlike laser or stamping, the process adds no heat-affected zone and work-hardens nothing, so the as-supplied spring properties survive into the finished part. Designers use spring sheet chemical etching when a part needs a fine cantilever, a controlled preload or a complex outline that would need an expensive progressive die. Etch factor is compensated in the artwork, and after stripping the parts can be age-hardened, plated with nickel or gold, and shipped on a carrier web for automated placement. The result is a flat, repeatable spring with a predictable force-deflection curve.

Parameter Window

• Available Materials: stainless 301/304 spring temper, 316L, beryllium copper C17200, phosphor bronze C5100
• Material Thickness Range: 0.05–0.5 mm, with 0.1–0.3 mm typical for contact springs
• Tolerance: ±0.02 mm on profile, ±0.01 mm on flexure width, half-etch depth ±10% of stock
• Minimum Feature: 0.10 mm arm width, 0.15 mm gap at 0.1 mm stock
• Surface Options: bare, age-hardened, electropolished, Ni/Au plating, adhesive carrier web
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Force-Deflection Review — Convert the drawing to artwork and check arm width, length and thickness against the required spring rate and preload.
2. Temper Selection — Pick alloy and temper for the target modulus and fatigue life, then confirm the sheet is flat before imaging.
3. Cleaning & Lamination — Degrease and laminate dry film on both faces so flexure arms are protected symmetrically.
4. Dual-Side Exposure — Expose front and back artwork in register, indexing half-etch thinned zones to the spring outline.
5. Development — Develop both faces and inspect narrow arms for scumming, which would thin the flexure and change its rate.
6. Controlled Etching — Etch through the outline and stop half-etched zones at the set depth, holding undercut by Baume, temperature and time.
7. Stripping & Ageing — Strip resist, neutralize, then age-harden beryllium copper or stress-relieve stainless to lock in the spring properties.
8. Plating & Inspection — Apply Ni/Au plating if specified, then verify profile, half-etch depth and force-deflection against the sample.

Core Advantages

1. Burr-free edges: No rolled edge or micro-crack means stress is not concentrated at the arm root, so fatigue life is preserved.
2. Temper preserved: Chemical removal adds no heat and no work hardening, so the supplied spring properties reach the finished part.
3. Half-etch flexure zones: Thinned sections and bend lines are made in the same bath, tuning stiffness without a second operation.
4. Fine complex outlines: Narrow cantilevers and intricate clips need only a film, so prototypes and revisions avoid a progressive die.
5. Repeatable spring rate: ±0.01 mm control on flexure width keeps the force-deflection curve consistent across a full panel.
6. Predictable preload: A controlled spring sheet chemical etching line delivers flat parts whose contact force matches the simulation.

Typical Applications

• Connector contacts: Fine cantilever springs in board-to-board and battery connectors, plated with gold over nickel.
• Switch domes and clips: Snap-action elements for keypad and tactile switches, held to a tight force band.
• Relay springs: Thin movable arms in electromagnetic relays, 301 spring temper with half-etched flexure.
• Shielding fingers: EMI grounding clips around board edges, formed from etched and folded flat patterns.
• Medical device clips: Small burr-free spring jaws for endoscopic and catheter mechanisms.
• Precision leaf springs: Calibrated flexures in sensors and meters, supplied on a carrier web for automated assembly.

Design Notes & Process Considerations

1. Arm width from spring rate: Fix flexure width and length from the required force-deflection curve, then add the etch compensation to the artwork.
2. Half-etch depth: State thinned-zone depth as a fraction of thickness, typically 40–60%, since it sets the local stiffness.
3. Grain direction: Orient long arms with the rolling direction where fatigue life is critical, and note it on the drawing.
4. Burr and edge callout: Require burr-free edges and an electropolished finish at the arm root to remove any residual stress riser.
5. Ageing step: Specify age-hardening for beryllium copper and stress relief for stainless, and confirm the sequence does not distort the part.
6. Carrier delivery: Decide whether parts ship on a carrier web or loose, because handling a 0.05 mm spring by hand deforms it.