Overview

Custom slit plate etching turns a single sheet of thin metal into an optical aperture plate carrying several slits of defined width, spacing and position, all formed by photochemical machining rather than laser cutting or wire EDM. A photoresist mask is exposed with the customer's slit layout, developed, and the bare metal is dissolved in a matched etchant, so every slit opens with a straight, burr-free edge and no heat-affected zone. Materials are typically stainless steel 304/316L, molybdenum, nickel and titanium, supplied between 0.02 mm and 0.5 mm thick. Because the slit width is defined by the film artwork and the etch is isotropic and tightly controlled, slit-to-slit repeatability and panel-level pitch accuracy stay far tighter than with machined or punched apertures, and the same film delivers identical plates from first prototype to volume.

For optical designers, custom slit plate etching solves two recurring problems: stacked or grouped slits that must share one flat carrier, and very narrow slits that laser cutting burns or chatters. Etching opens slits down to about 0.02 mm wide with edge straightness better than 0.005 mm over the slit length, and a plate can carry a row of graduated slits, cross-hairs and registration fiducials in a single pass. Because the metal is removed chemically, the plate remains flat and stress-free, which matters when it is mounted as an entrance slit, a spatial filter or a mask in a spectrometer, monochromator or imaging system.

Parameter Window

• Available Materials: stainless steel 304/316L, molybdenum, nickel 200, titanium
• Material Thickness Range: 0.02–0.5 mm
• Tolerance: slit width ±0.005 mm, slit pitch ±0.01 mm, plate outline ±0.05 mm
• Minimum Feature: 0.02 mm slit width at 0.05 mm stock
• Surface Options: black oxide, matte anti-reflective, brushed, mirror, electropolished
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Slit Layout Review — Convert the aperture drawing to vector artwork, check slit width against material thickness and confirm pitch, spacing and fiducial marks.
2. Material Selection — Match alloy and temper to the wavelength and environment; molybdenum for high stiffness, stainless for corrosion resistance.
3. Cleaning & Lamination — Degrease the sheet and laminate dry film resist so no bubbles or dust sit along the fine slit edges.
4. UV Exposure — Expose through high-resolution film with the slit artwork registered to the sheet edge for panel-level pitch accuracy.
5. Development — Wash out unexposed resist to open the slit areas, then inspect each slit for under-developed or broken edges.
6. Etching — Spray-etch in chemistry matched to the alloy, controlling slit width and edge straightness through time, temperature and conveyor speed.
7. Stripping & Finishing — Remove resist, neutralize, then apply black oxide or anti-reflective coating; deburr-free edges are inherent to the process.
8. Inspection & Packaging — Measure slit width, pitch and straightness on an optical comparator, then pack plates on liner in rigid trays.

Core Advantages

1. Multiple slits on one carrier: A row of graduated slits, cross-hairs and fiducials etch in one pass with shared registration, so alignment stays coherent.
2. No thermal or mechanical damage: Chemical removal leaves no recast, micro-cracking or burr, so slit edges stay clean and pass light cleanly.
3. Tight width and pitch control: Slit width holds to ±0.005 mm and pitch to ±0.01 mm across the whole plate, far better than laser or punching.
4. No tooling cost: Each slit layout is a new film, so short runs and design iterations stay economical without a die or fixture.
5. Flat, stress-free plates: The plate leaves the bath flat, which keeps grouped slits coplanar when the plate is mounted in an optical bench.
6. Material flexibility: Stainless, molybdenum, nickel and titanium run on the same line, letting one project mix aperture substrates.

Typical Applications

• Spectrometer entrance slits: Narrow entrance apertures that define spectral resolution, etched in molybdenum or stainless.
• Monochromator slit arrays: Rows of graduated slits on one plate for wavelength selection and calibration.
• Spatial filters and masks: Slit apertures with alignment fiducials for beam shaping and imaging systems.
• Calibration reticles: Etched slit patterns and cross-hairs used as optical alignment and scale references.
• Optical sensor apertures: Slit windows over photodetectors that control the light acceptance angle.
• Fluorescence and imaging masks: Slit plates that restrict the field of view in detection optics.

Design Notes & Process Considerations

1. Slit width versus thickness: Keep the narrowest slit at 0.02 mm or about 0.4 × material thickness, whichever is larger, so the slit does not etch closed or ragged.
2. Edge straightness callout: State straightness over the slit length, typically 0.005 mm, when the slit defines a resolution-critical aperture.
3. Pitch and fiducials: Group slits with shared registration marks and specify pitch tolerance, so mounting alignment is repeatable.
4. Surface finish: Name black oxide or anti-reflective coating for stray-light control; specify the wavelength band if the plate must suppress reflection.
5. Flatness: Call out flatness per 100 mm for plates with grouped slits, since any bow tilts the slit plane and shifts the aperture.
6. Plate handling: Keep slit plates on liner and specify edge burr-free handling; custom slit plate etching should always state slit width, pitch and straightness on the drawing.