Overview

A custom spring sheet etching process forms flat spring contacts, clips and flexures by chemically dissolving the outline and any half-etched bend lines from spring-temper stainless steel, instead of blanking them with a die. Grades 301, 304 and 316L in 1/2H to 3/4H temper, 0.05–0.8 mm thick, are laminated with dry-film resist, exposed and developed, then sprayed with ferric chloride so the part edges come out burr-free and free of the work-hardened shear zone a punch leaves behind. Because the metal is removed rather than sheared, the grain structure at the edge stays intact, which is what gives a thin flexure its fatigue life.

For a spring, the properties that matter are elastic force and fatigue endurance, and custom spring sheet etching protects both by leaving no notch-like burr for a crack to start from. Half-etch pockets and crease lines are produced in the same operation by stopping the etch partway through the thickness, so a contact can be bent to a precise angle without a separate forming die. Artwork compensation of roughly 0.6–0.8 × thickness per side holds a ±0.02 mm profile tolerance, and because tooling is only a film, changing a leg width or a spring rate is a quick revision that keeps short runs economical.

Parameter Window

• Available Materials: stainless steel 301/304/316L (1/2H, 3/4H, H temper), beryllium copper C17200, phosphor bronze
• Material Thickness Range: 0.05–0.8 mm (0.1–0.3 mm typical for contacts)
• Tolerance: profile ±0.02 mm, half-etch depth ±10% of thickness, bend-line position ±0.03 mm
• Minimum Feature: 0.15 mm leg width, 0.2 mm slot, 0.1 mm radius at 0.15 mm stock
• Surface Options: passivated, electropolished, Ni/Au plating, formed and heat-set, adhesive backing
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Artwork & Compensation — Draw the developed flat pattern and shrink profiles by the measured side-etch factor, about 0.6–0.8 × thickness per side.
2. Material Selection — Pick 301 for high spring force, 316L for corrosion resistance or C17200 for conductivity, and confirm temper and grain direction.
3. Cleaning & Lamination — Degrease and laminate dry-film resist on both faces so narrow legs and bend lines are fully protected.
4. UV Exposure — Expose the outline and half-etch artwork through registered film, keeping the pattern aligned to the rolling direction.
5. Development — Wash out unexposed resist to open the cut areas and crease lands, then inspect fine legs for scumming.
6. Etching — Spray ferric chloride to cut through the outline while a timed second pass stops at the half-etch depth for bend lines.
7. Stripping & Forming — Strip resist, neutralize, then form, heat-set and passivate or plate to lock in spring force.
8. Inspection & Packaging — Verify profile, half-etch depth, flatness and force on a sample, then pack in trays that protect the legs.

Core Advantages

1. Burr-free edges for fatigue life: Chemical removal leaves no shear burr or micro-notch, so repeated flexing does not start a crack at the edge.
2. No work hardening: The grain structure at the cut edge is unchanged, so spring force and temper stay as specified across the whole part.
3. Half-etch bend lines in one pass: Creases and reduced-thickness hinges are etched with the outline, removing a separate forming or coining step.
4. Fine legs without a die: 0.15 mm legs and 0.2 mm slots hold on thin stock where a punch would distort or tear the strip.
5. Consistent force batch to batch: All parts on a sheet see the same etch depth and temper, so spring rate repeats from the first sample to volume.
6. Low-cost iteration: custom spring sheet etching changes a film to retune spring rate, so force tuning and prototype batches carry no die charge.

Typical Applications

• Battery and connector contacts: Spring-temper 301 contacts that hold force over thousands of mating cycles.
• EMI/RF shielding clips: Beryllium-copper or stainless fingers with burr-free edges that will not score the mating surface.
• Precision flexures and hinges: Half-etched crease lines for instruments and optical mounts that bend to a repeatable angle.
• Switch and relay springs: Thin 304 blades with controlled force and tight profile tolerance.
• Medical device clips: 316L spring parts for surgical tools and implantable accessories that need clean edges.
• Automotive sensor retainers: Formed spring clips that resist vibration fatigue under the hood.

Design Notes & Process Considerations

1. Grain direction: Orient legs along the rolling direction where flexing is heaviest, since transverse grain shortens fatigue life.
2. Edge quality: Call out burr-free edges and a maximum edge radius, because a notch is the usual fatigue-crack origin.
3. Half-etch depth: State the residual thickness at bend lines, typically 40–60% of stock, and allow a test coupon to set it.
4. Temper and force: Specify the temper and the target force at a defined deflection so forming and heat-set can be verified.
5. Minimum radius: Avoid sharp inside corners; keep the radius at least 0.1 mm to lower stress concentration.
6. Flatness and handling: custom spring sheet etching parts are thin and springy, so specify flatness and tray packaging to prevent permanent set.