Overview

An aperture plate etching service forms circular, slot and profiled openings in thin metal by photochemical machining, so the bore is created by controlled chemical dissolution rather than by a punch, a drill or a laser. The artwork is exposed onto photoresist on both faces of the sheet, developed, and the panel is sprayed from each side at matched rates so the two etch fronts meet near the centre line. What comes out of the bath is a near-vertical bore with a clean square edge and no roll-over, which is exactly what an optical aperture needs.

Optical designers care about three things on these parts. Concentricity between the clear hole and the outer datum sets the optical axis; an offset of a few hundredths of a millimetre shows up as vignetting at the field edge. Edge sharpness sets stray light, because a burr or a rounded lip scatters grazing rays back into the image path. Flatness sets the installed angle, since a warped foil tilted inside a barrel behaves like a displaced stop. Photochemical machining addresses all three at once: no mechanical stress is applied, so thin stock stays flat, and the edge is a straight cut rather than a torn or melted one.

Parameter Window

• Available Materials: molybdenum, nickel 200, stainless steel 304/316L, titanium foil
• Material Thickness Range: 0.02–0.5 mm
• Tolerance: ±0.05 mm on outside profile, ±0.02 mm on hole position, concentricity within 0.02 mm
• Minimum Feature: 0.05 mm hole diameter on 0.03 mm foil, 0.06 mm web between holes
• Surface Options: chemical blackening, black nickel plating, passivation, matte bead blast
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Optical drawing review — Check bore diameter, hole position and the concentricity datum, and confirm whether tolerance is called on the edge or the centre.
2. Material selection — Molybdenum for high-energy beams, 304/316L for visible paths, titanium foil where thin and tough is required.
3. Cleaning and double-sided lamination — Degrease and hot-roll dry film on both faces to equal thickness so the two etch fronts advance symmetrically.
4. Registered double-sided exposure — Expose top and bottom film through the same target marks so hole centres stay within 0.01 mm of each other.
5. Development and inspection — Wash out unexposed resist and inspect every plate for residual film, nicks and pinholes before etching.
6. Synchronised etching — Spray both faces at matched pressure and temperature so the fronts meet at mid-thickness and leave a straight wall.
7. Stripping and blackening — Remove resist, neutralise, then blacken or plate black nickel to suppress reflection at the bore edge.
8. Optical inspection — Measure bore size, position, concentricity and foil flatness on a vision system, and check edges for burr or taper.

Core Advantages

1. Clean edge, low scatter: Chemical removal leaves no burr and no rolled lip, so the bore edge is a true right angle and edge scatter drops well below punched parts.
2. Concentricity under control: Registered two-sided exposure keeps the bore centred on the outer datum, holding 0.02 mm across a production lot.
3. Thin foil stays flat: No mechanical force is applied at any step, so 0.05 mm molybdenum leaves the line flat and needs no levelling or re-fixturing.
4. No tooling charge: A new bore size is a new film, so a trial set of stops in several diameters can share one panel at very low cost.
5. Complex profiles at the same accuracy: Fan-shaped openings, slits and baffle outlines etch to the same tolerance as round holes, in a single pass.
6. Stable across small batches: All stops on a panel etch together, and lot-to-lot bore size is held by locked bath parameters — useful when a prototype becomes a production order.

Typical Applications

• Iris diaphragm blades: Individual leaves and fixed stops for lens irises, etched in 0.05 mm stainless and blackened before assembly.
• Microscope field stops: Round or square masks at an intermediate image plane, positioned to ±0.02 mm with burr-free rims.
• Spectrometer entrance slits: Slit pairs with 0.05 mm gaps where wall verticality directly sets spectral resolution.
• Laser beam shaping: Molybdenum apertures for high-power paths, where the edge must not melt back or sputter.
• Sensor light masks: Window apertures in front of image sensors, aligned to the die cavity to cut oblique rays.
• Telescope baffle stops: Lightweight stop rings stacked inside a tube to kill wall reflections stage by stage.

Design Notes & Process Considerations

1. Wall verticality: Single-sided etching produces a visible taper that dominates small bores; specify two-sided etching and state the taper you can accept.
2. Edge chamfer: Say whether a chamfer is wanted. Optical parts usually need a sharp rim, because a chamfer enlarges the clear aperture and adds scatter.
3. Blackening choice: Name the process and a reflectance ceiling. Black anodising does not apply to molybdenum or nickel, so black nickel or chemical blackening is used instead.
4. Flatness callout: State bow per 20 mm, typically 0.02 mm or better, and ask for a temporary frame on foils under 0.05 mm to survive handling.
5. Panel and marking: When several stops share a panel, etch a notch or a part number so diameters cannot be mixed at assembly.
6. Datum consistency: The hole position datum and the mounting datum must be the same face and the same edge; writing that into the drawing on an aperture plate etching service order removes most first-article queries.