Overview

Washer chemical etching is a photochemical machining process that forms a flat washer by dissolving unprotected metal, so the outer diameter, inner bore and any slots or tabs are all cut in a single pass. A photoresist mask is exposed with the washer outline on both sides of the sheet, developed, and the exposed metal is removed by a matched etchant. Because the inside and outside diameters are defined by the same film at the same time, the bore is automatically concentric with the outside, and both edges come out burr-free and square. Typical materials are stainless steel 304/316L, copper, brass and spring steel, in thicknesses from 0.05 mm to 1.0 mm.

The process itself is what makes these washers dependable. No punch-and-die force means no dish, no taper and no burr, so a washer stays flat against the fastener and spreads load evenly; no heat means no distortion and no change in temper, so spring-steel washers keep their hardness. Because a design change is only a new phototool, washer chemical etching also suits the short runs and frequent size revisions that stamping tools make expensive.

Parameter Window

• Available Materials: stainless steel 304/316L, copper, brass, spring steel
• Material Thickness Range: 0.05–1.0 mm
• Tolerance: ±0.05 mm on outer diameter, ±0.03 mm on inner bore
• Minimum Feature: 0.1 mm inner bore, 0.15 mm slot width at 0.2 mm stock
• Surface Options: as-etched, passivated, black oxide, zinc-plated, annealed for flatness
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Drawing Review — Convert the washer drawing to vector, confirm OD, ID and any slots or tabs, and freeze the size revision.
2. Material Selection — Match alloy, temper and gauge to the duty; spring steel for lock washers, copper for conductive seats, stainless for corrosion.
3. Cleaning & Lamination — Degrease the sheet and laminate dry film resist on both faces so the bore and OD etch symmetrically.
4. Double-Sided Exposure — Expose front and back film in register so the bore stays concentric with the outer edge.
5. Development — Wash out unexposed resist to open the OD, bore and any slots, then check fine features for full development.
6. Etching — Spray etchant from both sides at controlled temperature and speed; concentricity follows the film registration.
7. Stripping & Finishing — Remove resist, neutralize, then passivate, blacken, plate or anneal; annealing flattens very thin washers.
8. Inspection & Packaging — Verify OD, ID, concentricity, thickness and flatness, then pack flat on liners or in trays.

Core Advantages

1. Concentric bore by design: ID and OD come from the same film, so the bore is centered without a separate centering operation.
2. Burr-free and square edges: Dissolution leaves no burr, so washers seat flat and never scratch the mating surface.
3. Stress-free and flat: No blanking force means no dish or taper, so load spreads evenly under the fastener head.
4. No temper loss: Etching introduces no heat, so spring-steel washers keep their hardness and clamping behavior.
5. Tight, repeatable diameters: OD and ID hold ±0.05 mm and ±0.03 mm across a batch, with no die wear to drift the size.
6. No tooling, quick turns: A new washer size is a new phototool. Washer chemical etching is therefore the fast way to a flat, concentric washer in any small quantity.

Typical Applications

• Load-spreading washers: Flat stainless washers that distribute fastener load over soft or thin panels.
• Lock washers: Spring-steel washers with fine tabs that keep their springback and clamping force.
• Conductive washers: Copper or brass washers used as contact and grounding seats in electrical assemblies.
• Spacer washers: Precision-thickness washers that set an exact gap between stacked components.
• Shim washers: Thin stainless shims that correct alignment while acting as a bearing surface.
• Aperture washers: Washers with a fine central bore used as flow restrictors and metering orifices.

Design Notes & Process Considerations

1. Bore versus thickness: Keep the minimum inner bore at or above 1.0 × material thickness — 0.1 mm is realistic at 0.2 mm stock.
2. Concentricity callout: State the ID-to-OD concentricity tolerance; ±0.03 mm is realistic and comes free from the film.
3. Edge condition: Confirm whether a straight or slightly tapered edge is acceptable, and require square edges where the washer bears on its face.
4. Flatness and annealing: For thin washers under 0.1 mm, specify flatness per 100 mm and allow annealing after etching.
5. Surface and plating: Name the finish — passivation, black oxide or zinc — and state the environment to avoid hydrogen issues.
6. Size revision control: Freeze the diameter revision before making the phototool. Washer chemical etching keeps size changes cheap because tooling is film, not steel.