Overview

A slit plate etching service produces precision optical slit plates by photochemical machining, forming one or more narrow apertures in a thin stainless steel or molybdenum sheet. The slit pattern is imaged onto a photoresist mask, developed, and the unprotected metal is dissolved in an alloy-matched etchant, leaving straight, burr-free slit edges with a tightly controlled width. Because the apertures are defined photographically, a plate can carry a single slit, a set of slits with different widths, or a coded aperture array, all formed in one pass with no stamping die or laser tooling.

For optical system builders, the service answers two recurring needs. First, precision: slit width, straightness and spacing must hold within microns so the instrument resolves the intended wavelength band and stays calibrated. Second, flexibility: slit geometry changes with each design iteration, and a photographic film is far cheaper and faster to revise than any mechanical tooling. Stainless steel and molybdenum foils give the stiffness and low thermal expansion optical benches require, and the flat, stress-free plates mount cleanly without shimming or bending.

Parameter Window

• Available Materials: stainless steel 304, molybdenum, nickel, Invar
• Material Thickness Range: 0.02–0.3 mm
• Tolerance: ±0.005 mm on slit width, ±0.02 mm on slit length and position
• Minimum Feature: 0.01 mm slit width, 0.05 mm spacing between adjacent slits
• Surface Options: black oxide, matte finish, electroless nickel, bare foil
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Slit Review — Convert the slit-plate drawing to vector artwork, confirm each slit's width, length and position, and check straightness requirements.
2. Material Selection — Choose molybdenum for low expansion, stainless 304 for stiffness, nickel or Invar where a specific CTE is required.
3. Cleaning & Lamination — Degrease the sheet and laminate dry film resist so no bubbles sit along the slit edges, which would spoil straightness.
4. UV Exposure — Expose through high-resolution film with the slit pattern registered to the sheet edge for panel-level accuracy.
5. Development — Wash out unexposed resist to open the slits, then inspect the resist edges for under-development or raggedness.
6. Etching — Spray-etch in alloy-matched chemistry; slit width and edge straightness are set by time, temperature and conveyor speed.
7. Stripping & Finishing — Remove resist, neutralize, then blacken or plate; optical measurement confirms width and straightness before release.
8. Inspection & Packaging — Verify slit width, straightness, spacing and surface finish against the approved sample, then pack in trays or sleeves.

Core Advantages

1. Micron-level width control: Slit width holds within ±0.005 mm along the full length, giving stable spectral resolution.
2. Straight, burr-free edges: Chemical removal leaves no recast, taper or burr, so the optical profile stays clean with low scatter.
3. Multi-slit capability: Several slits or a coded aperture array etch in one pass, with spacing controlled photographically.
4. Flat, stress-free plates: The process introduces no mechanical stress, so plates mount cleanly without shimming or bending.
5. Low-expansion materials: Molybdenum, Invar and stainless foils provide the stiffness and thermal stability optics demand.
6. Fast, low-cost revisions: A new slit layout is a new film — a slit plate etching service keeps iteration economical and quick.

Typical Applications

• Spectrometer slit plates: Plates carrying entrance and exit slits for grating and prism spectrometers.
• Monochromator slit sets: Multi-slit plates that select narrow wavelength bands for analysis.
• Spatial filter plates: Fine slit plates for laser spatial filtering and beam cleanup in optical benches.
• Encoder slit discs: Plates with radial slits for optical encoders and position sensors.
• Photometer aperture plates: Slit plates that limit the field of view in light measurement instruments.
• Coded aperture masks: Multi-slit plates for coded aperture imaging and multi-channel spectroscopy.

Design Notes & Process Considerations

1. Slit width and tolerance: State each slit's nominal width and tolerance, typically ±0.005 mm, and mark which slits are critical.
2. Edge straightness: Call out straightness per unit length and require burr-free edges, since ragged edges scatter light and widen the effective slit.
3. Material and CTE: Choose molybdenum or Invar for thermal stability, stainless where stiffness and cost lead.
4. Surface finish: Specify black oxide or matte finish to suppress stray reflections that add background to the signal.
5. Slit spacing: For multi-slit plates, give center-to-center spacing and require uniform width across all slits.
6. Datum and mounting: Define a datum edge for position tolerance and specify mounting holes, since alignment depends on both.