Overview

An etched stainless steel aperture is a precision optical stop, pinhole or slit made by photochemical machining rather than by drilling or laser cutting. The aperture artwork is exposed onto photoresist on ultra-flat foil, developed, and the unprotected metal is dissolved in a matched etchant, so the opening is defined by the film and the etch time. Substrates are typically stainless 304/316L/430, nickel or Invar between 0.02 mm and 0.3 mm. Because the process is chemical and force-free, it produces round, burr-free edges with no recast layer, no heat-affected zone and no residual stress — exactly the properties an optical system needs to avoid stray diffraction and scattered light.

For buyers, an etched stainless steel aperture solves the limits of mechanical and thermal methods at the micron scale. Drilled or punched pinholes below about 0.05 mm wander, carry burrs and work-harden thin foil; laser cutting leaves dross, taper and a heat tint that changes the edge; and any mechanical edge reflects light back into the optical path. Photochemical machining holds ±0.005 mm on hole or slit size, keeps roundness high, and can blacken the surface for low reflection. Dozens of identical stops fit on one sheet, so a multi-aperture wheel or an encoder disc etches as one stress-free part and repeats from prototype to volume without tooling wear.

Parameter Window

• Available Materials: stainless steel 304/316L/430; also nickel and Invar for low-expansion grades
• Material Thickness Range: 0.02–0.3 mm
• Tolerance: ±0.005 mm on pinhole/slit size, ±0.01 mm on center position
• Minimum Feature: 0.02 mm pinhole, 0.03 mm slit, high roundness with clean wall
• Surface Options: black oxide, black nickel plating, electropolishing, matte anti-reflection, clean passivation
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Artwork & Roundness Compensation — Size the pinhole or slit in the film to offset undercut, then lay out multi-aperture arrays with shared datums.
2. Ultra-Flat Foil Selection — Choose flat, low-inclusion foil, verify thickness and certificate, and handle in a clean area to avoid dust defects.
3. Cleaning & Lamination — Degrease and laminate fine-grain dry film resist under controlled conditions so micron features resolve sharply.
4. UV Exposure — Expose through high-resolution film with collimated light, registering every aperture to the sheet datum for positional accuracy.
5. Development — Wash out unexposed resist and inspect openings under magnification for residue that would distort the hole.
6. Precision Etching — Spray matched chemistry with tight time and temperature control to hold roundness and a straight, burr-free wall.
7. Stripping & Blackening — Remove resist, then black-oxide, black-nickel or electropolish the surface for low reflection and optical cleanliness.
8. Microscopic Inspection — Measure hole size, roundness, position and burr on a microscope or vision system, then pack in clean, non-shedding trays.

Core Advantages

1. Micron-scale openings: 0.02 mm pinholes and 0.03 mm slits are formed cleanly, beyond the stable range of drilling or punching thin foil.
2. Clean, round edges: Chemistry leaves no burr, recast layer or heat tint, so diffraction artifacts and stray scatter are minimized.
3. Stress-free and flat: With no force or heat, ultra-thin foil stays flat, so the aperture seats correctly in an optical mount.
4. Low-reflection finish: Black oxide, black nickel or matte treatments cut surface reflection that would otherwise pollute the beam path.
5. Multi-aperture consistency: Every stop on a sheet etches at the same rate, so aperture wheels and encoder discs match across the array.
6. Material flexibility: etched stainless steel aperture parts can use 304/316L, nickel or Invar to balance corrosion, flatness and thermal expansion.

Typical Applications

• Microscope and camera stops: Iris leaves and fixed stops that set numerical aperture without edge glare.
• Spectrometer slits: Straight, burr-free entrance and exit slits that define spectral resolution.
• Laser pinholes: Spatial-filter and alignment pinholes where roundness governs beam quality.
• Encoder discs: Multi-slot code wheels for rotary and linear encoders etched as one flat part.
• Mask and calibration targets: Resolution charts, reticles and alignment masks with dense, accurate openings.
• Beam-shaping arrays: Multi-aperture plates for uniform illumination, light homogenizing and sensor calibration.

Design Notes & Process Considerations

1. Hole-to-thickness ratio: Keep the opening at or above material thickness where possible, or undercut produces a tapered, conical wall instead of a straight one.
2. Roundness and position: State diameter, roundness and center-position tolerance separately, since optical performance depends on each.
3. Reflection and coating: Define the blackening or matte treatment and a reflectance target for the working wavelength.
4. Burr and cleanliness: Require burr-free edges and optical-grade cleanliness, as a particle at a 0.02 mm hole acts like a second aperture.
5. Thin-foil handling: For foil below 0.05 mm, specify a carrier frame, flatness and clean packing so the stop does not crease or collect dust.
6. Inspection datum: With etched stainless steel aperture work, fix the measurement datum and microscopic acceptance criteria for size, roundness and defects.