Overview

An etched stainless steel leaf spring is a flat, compliant component cut from spring-temper stainless foil by photochemical machining rather than by a stamping die. Used in micro switches, relays, battery contacts and latching clips, the part gets its shape from a photoresist image and a controlled etch bath, so complex outlines, slots, locating holes and half-etched bending zones all form in one operation. Typical stock is 301, 304, 316L or 17-7PH between 0.05 mm and 0.60 mm, with profile tolerance held to ±0.02 mm.

The reason engineers specify an etched stainless steel leaf spring over a stamped one is metallurgical. Stamping shears the edge, work-hardens the bend root and leaves a roll-over burr, all of which scatter the spring rate and shorten fatigue life. Chemical removal leaves a flat, burr-free, stress-free blank whose elastic response matches the design calculation, and half-etching lets a single part be thick at the mount and thin at the flexure. Because the tooling is film, a change in free height or force is a low-cost revision, not a new die.

Parameter Window

• Available Materials: stainless steel 301/304/316L spring temper, 17-7PH, 430
• Material Thickness Range: 0.05–0.60 mm
• Tolerance: ±0.02 mm on profile, ±10% of thickness on half-etched depth
• Minimum Feature: 0.10 mm line width, 0.15 mm slot, 0.20 mm hole at 0.20 mm stock
• Surface Options: passivation, bright anneal, electropolish, formed and pre-loaded, adhesive backing
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Load Case Review — Establish deflection, target force, cycle life and mounting geometry before drawing the flat pattern.
2. Flat Pattern Design — Lay out the outline, flexure, slots and holes, then add etch compensation to every edge.
3. Material & Temper Selection — Match alloy and spring temper to the required force; 301 for high strength, 316L for corrosion.
4. Cleaning & Lamination — Degrease the foil and laminate dry-film resist on both faces under controlled heat and pressure.
5. UV Exposure & Development — Expose through registered film, then develop to open the cut areas and the half-etch windows.
6. Etching & Half-Etching — Etch through the outline while timing a second, shallower step for the reduced-thickness flexure.
7. Stripping & Forming — Strip resist, passivate or electropolish, then form to free height and stress-relieve if needed.
8. Inspection & Packaging — Verify force-deflection curve, flatness and half-etch depth, then pack in trays or on liners.

Core Advantages

1. No die cost: A new force rating is a new film, so prototypes and revisions stay economical.
2. Burr-free, stress-free edges: No shear zone or work-hardened bend root, so fatigue life is predictable.
3. Half-etched stiffness zones: One blank can be thick at the clamp and thin at the flexure without a welded or bonded add-on.
4. Complex flat geometry: Slots, locators, markings and asymmetric arms form in the same pass as the outline.
5. Consistent spring rate: Whole-sheet etching keeps force-deflection behaviour uniform from part to part.
6. Fast tuning: An etched stainless steel leaf spring can be re-rated by a film change and re-sampled in days.

Typical Applications

• Micro switch and relay blades: Thin flexures that snap between contacts over millions of cycles.
• Battery and holder contacts: Pre-loaded leaf contacts that keep pressure on cells through vibration.
• Connector latch springs: Flat springs that retain a mating connector without a separate clip.
• EMI shielding fingers: Grounding contacts along enclosure seams that tolerate repeated opening.
• Precision instrument detents: Compliant arms that provide a defined click or holding force.
• Medical device clips: Burr-free, passivated springs for small disposable mechanisms.

Design Notes & Process Considerations

1. Feature size versus thickness: Keep slots and holes at 1.5 × stock thickness or larger, or walls will thin and distort.
2. Etch factor on both faces: Two-sided undercut changes the finished arm width, so confirm the compensation on a coupon.
3. Half-etch depth callout: State the residual thickness at the flexure; force scales roughly with the cube of thickness.
4. Temper and grain direction: Orient the flexure across the rolling direction and lock the temper at qualification.
5. Force-deflection test method: Define supports, loading point, deflection and acceptable force band on the drawing.
6. Forming and burr direction: Specify free height after forming and confirm burr-free seating surfaces; a well-made etched stainless steel leaf spring should sit flat without secondary deburring.