Overview

An etched light shield is a thin metal part that blocks stray light and defines one or more apertures inside an optical path. Photochemical machining suits the job because the part is usually 0.05–0.5 mm thick and carries apertures, slits and baffle arrays far finer than a stamping die can hold: a 0.1 mm stainless sheet can take a 0.08 mm aperture with a clean, vertical wall, and every opening in the array lands within ±0.01 mm of its nominal position. Common substrates are 304 and 301 stainless steel, 1100 and 5052 aluminum, and Alloy 42 where the shield must match the expansion of a glass or ceramic package.

Because the shield is metal through its full thickness, it is genuinely opaque — no pinholes, no fibre bleed and no gradual yellowing as a black film would show under heat or UV. Aperture rims can be half-etched from both faces so the bore is only 20–30 µm deep at the edge, producing a knife edge that suppresses the bright ring and veiling glare a thick square-cut wall reflects. Etched light shields also stay flat: sheets are processed without mechanical stress, so a 0.1 mm shield holds flatness inside 0.05 mm over 50 mm and stacks cleanly against sensor packages and lens barrels.

Parameter Window

• Available Materials: 301/304 stainless steel, 1100/5052 aluminum, Alloy 42 (Ni42Fe) for CTE matching, black-anodized aluminum
• Material Thickness Range: 0.05–0.5 mm; 0.03 mm foil on request for stacked baffles
• Tolerance: ±0.01 mm on aperture diameter and position, ±0.02 mm on outer profile, ±10% of stock on etch depth
• Minimum Feature: 0.08 mm round aperture and 0.05 mm slit width at 0.1 mm stock; 0.15 mm web between apertures
• Surface Options: matte black oxide, black dye anodize, black electroless nickel, bead-blast plus black passivation, gloss below 5 GU
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Optical Drawing Review — Check every aperture diameter, position and web against the light path, and confirm which edges must be knife-thin rather than square-cut.
2. Material & Finish Selection — Pick stainless for stiffness and corrosion resistance, aluminum for weight, Alloy 42 for matched expansion; fix the blackening route before etching.
3. Cleaning & Double-Side Lamination — Degrease and laminate resist on both faces so front and rear patterns can be etched independently.
4. Registered Exposure — Expose through film pinned to the sheet, with the aperture array and the outer contour on the same registration datum.
5. Development — Open the aperture and contour windows, then verify that no resist scum remains inside a 0.08 mm opening.
6. Controlled Etching — Etch to depth or through-cut with bath chemistry, temperature and conveyor speed logged; knife-edge rims are half-etched to a set remaining thickness.
7. Blackening & Cleaning — Blacken, seal and rinse in de-ionised water; the coating is applied after etching so it cannot close a fine aperture.
8. Optical Inspection & Packing — Measure aperture diameter, position, edge burr, gloss and flatness, then pack in clean trays under interleaving film.

Core Advantages

1. True opacity: The shield is solid metal, so no pinhole, fibre or coating degradation lets light leak through after thermal cycling.
2. Knife-edge apertures: Half-etched rims cut the wall thickness at the bore to 20–30 µm, which removes the bright ring and flare of a square-cut edge.
3. Aperture-to-aperture accuracy: All openings on a sheet etch together, so a 200-aperture array holds ±0.01 mm position without cumulative punch error.
4. Burr-free, non-scattering edges: Chemical removal leaves no roll-over to catch light or shed particles into a lens barrel.
5. Flat, stackable parts: No mechanical stress means flatness within 0.05 mm over 50 mm, so shims and baffles stack without tilting the optical axis.
6. One part replaces an assembly: Baffle arrays, spacer rings and aperture stops can be etched into a single shield, cutting part count and alignment steps.

Typical Applications

• Camera module baffles: Multi-aperture shields that sit above a lens stack and trim off-axis rays before they reach the sensor.
• Sensor aperture stops: Thin stainless stops with a single 0.2 mm opening that fixes the f-number of a compact imaging system.
• LiDAR and ranging receivers: Shields that isolate a detector from the emitter path and suppress internal reflection.
• Spectrometer and analyser slits: Narrow slit pairs etched to 0.05 mm width with parallel walls for consistent spectral resolution.
• Automotive HUD and lighting: Blackened shields that stop light bleed between segments of a head-up display or a matrix lamp.
• Medical and analytical instruments: Opaque masks over photodiodes and flow cells where stray light would shift a reading.

Design Notes & Process Considerations

1. Edge thickness drives stray light: Specify the remaining rim thickness at the aperture; 20–30 µm gives a knife edge, while a full-thickness wall reflects a visible ring.
2. Coating closes small holes: A 5 µm black coating narrows a 0.1 mm aperture by about 10%, so state whether the diameter is measured before or after finishing.
3. Gloss rather than colour: Matte black at 3–5 GU suppresses reflection better than a dark but glossy surface; give a gloss limit, not only a colour.
4. Web width between apertures: Keep at least 0.15 mm of metal between adjacent openings at 0.1 mm stock, or the web distorts during etching.
5. Flatness and mounting: Call out flatness per 50 mm and the datum face, because a shield that bows by 0.1 mm shifts the aperture in a short focal system.
6. Front-to-back registration: When apertures are etched from both sides, fix a registration tolerance of 0.02 mm; misregistration turns a round bore into a slit and changes the light cone.