Overview

Custom spring etching produces flat springs, cantilever contacts, spiral arms and diaphragm springs by photochemical machining rather than stamping or wire forming. The spring outline is imaged onto resist, developed, and etched out of tempered strip, so the finished part is a two-dimensional profile cut from the sheet with no die, no blanking shock and no tool contact on either face. Spring steels, beryllium copper and phosphor bronze are all processed between 0.05 mm and 0.8 mm, with slot widths down to 0.1 mm and arm widths sized to the load the spring must carry.

Spring rate depends on three things: the elastic modulus of the alloy, the section geometry and the free length. Etching controls geometry very tightly in the plane of the sheet, which is where a flat spring does most of its work, and it leaves the surface undisturbed, so the temper that was rolled into the strip survives the process. There is no sheared edge with a work-hardened burr to act as a crack starter, and no local deformation from a punch, which is why etched springs tend to repeat their rate from part to part and to survive more cycles before load loss.

Parameter Window

• Available Materials: spring steel 301/302, 17-7PH, beryllium copper C17200, phosphor bronze C51000, stainless 316L
• Material Thickness Range: 0.05–0.8 mm, supplied in rolled temper
• Tolerance: ±0.05 mm on profile and slot position, ±0.02 mm on arm width
• Minimum Feature: 0.1 mm slot, 1:1 width-to-thickness ratio for load-bearing arms
• Surface Options: passivation, nickel or gold plating, black oxide, deburr-free as-etched finish
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Load Case Review — Take working load, travel and allowed stress from the design, and confirm that the arm geometry can deliver the target rate in the chosen alloy.
2. Alloy and Temper — Select 301 for cost, 17-7PH where corrosion and fatigue both matter, beryllium copper where conductivity is required, and fix temper before etching.
3. Stress Relief — Low-temperature relief before coating removes slitting and levelling stress that would otherwise cause curl after etching.
4. Lamination — Apply dry film resist to both faces, keeping the film thin and even so arm width does not vary across the panel.
5. Exposure and Development — Expose both sides in registration, develop, and check arm width on a sample before the panel is etched.
6. Etching — Etch from both faces at matched rates so the wall profile stays symmetrical and the arm section remains rectangular.
7. Strip and Form — Remove resist, then bend, set or post-form where a three-dimensional shape is needed; stress relief after forming is optional.
8. Load Test and Pack — Measure rate and free height on a sample from each lot, record the values, and pack flat so arms are not preloaded in transit.

Core Advantages

1. No die, no tool marks: Nothing touches the working surface, so there are no punch marks, coining flats or die lines to alter stiffness or start a fatigue crack.
2. Burr-free edges: The etched edge is smooth and slightly tapered, removing the sheared burr that concentrates stress at the root of a stamped arm.
3. Geometry in one pass: Slots, spirals, folded arms and multiple spring rates can sit on one panel and be produced in a single etch.
4. Temper preserved: Because the process is chemical and near-ambient, the rolled temper of the strip is retained and the rate stays close to calculation.
5. Fast iteration: Changing an arm width to trim the rate means changing a film, which keeps prototype rounds short.
6. Batch consistency: All springs on a panel etch together, so rate spread within a lot is narrow. Custom spring etching therefore suits instruments that must be calibrated once.

Typical Applications

• Cantilever contacts: Gold-plated beryllium copper arms that carry signal and apply a defined contact force in connectors.
• Diaphragm springs: Spiral-cut discs that provide a linear rate in small valves and pressure regulators.
• Battery and shield contacts: Flat springs that ground a shield can or preload a cell in a handheld device.
• Instrument suspensions: Low-rate arms that centre a moving coil or mirror without friction.
• Detent and return springs: Flat springs that return a slider or latch in compact mechanisms.
• Medical and analytical clips: 316L springs that hold a vial or a sensor in a disposable cartridge.

Design Notes & Process Considerations

1. Rate versus thickness: Rate rises with the cube of thickness, so hold thickness tolerance before tightening arm width; a 5% thickness change moves rate about 15%.
2. Root radius: Give the arm root a radius of at least one material thickness; a sharp internal corner etches with a stress concentration that shortens fatigue life.
3. Slot width: Keep slots at 1:1 with thickness or wider, since narrower slots etch slowly and may not clear on thick stock.
4. Grain direction: Orient the long axis of a cantilever across the rolling direction where fatigue matters, and state the direction on the drawing.
5. Plating and set: Plate before forming where the bend line must stay free of cracked coating, and specify whether the spring is supplied flat or set.
6. Sample rate check: Ask for a load-deflection curve on the first article. Custom spring etching holds geometry, but the target rate still has to be confirmed on a real spring.