Overview

A custom copper optical slit is a thin copper foil carrying one or more extremely narrow, straight light-transmitting apertures for spectrometers, encoders and collimators, made by photochemical etching instead of mechanical scribing or laser cutting. A photoresist is imaged with the slit pattern on both faces, developed, and the exposed metal is dissolved, leaving a slit of uniform width with burr-free walls and no heat-affected zone. Stock is typically oxygen-free copper C10100 or C110 between 0.02 mm and 0.3 mm. Because copper is readily blackened for low reflectance, a custom copper optical slit avoids the stray-light bloom that laser slag creates at the aperture edge.

For optical engineers, the custom copper optical slit controls the hardest part of a light gate: a 0.02 mm slit chips under a blade, a slit tens of millimetres long must stay the same width end to end, and any edge burr generates diffraction artifacts. Etching forms the slit as artwork, so changing width or pitch is a new film, not a precision tool, keeping multi-specification prototypes economical. Spectrometer entrance slits, encoder slit arrays, collimating apertures and stray-light masks all rely on fine, clean, full-length-consistent etched copper slits.

Parameter Window

• Available Materials: oxygen-free copper C10100, copper C110, phosphor bronze, beryllium copper
• Material Thickness Range: 0.02–0.3 mm (0.05 mm and 0.1 mm foil for the finest slits)
• Tolerance: ±0.005 mm on slit width, ±0.02 mm on slit position, ±0.05 mm on outline
• Minimum Feature: 0.02 mm slit width, 0.05 mm web between slits, up to 40 mm slit length held to equal width
• Surface Options: bare, chemical blackening, Ni plating, anti-tarnish, matte anti-reflection coating
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Artwork Review — Vectorize the slit file, check width, length and web against foil thickness, and set alignment datums.
2. Material Selection — Choose oxygen-free copper grade and temper for the slit width and stiffness; reject foil with scratches or creases.
3. Cleaning & Lamination — Degrease and laminate dry film on both faces so no bubble sits under a fine slit, since lamination cleanliness sets edge quality.
4. UV Exposure — Expose both sides through high-resolution film registered to the sheet edge for top-to-bottom alignment and uniform width.
5. Development — Open the slit area and inspect under a microscope for residual resist that would leave a slit uncut.
6. Etching — Spray copper-matched chemistry with tightly controlled time and temperature to prevent side-etch widening the slit or tapering the wall.
7. Stripping & Finishing — Remove resist, neutralize, then blacken or apply matte coating, keeping ultra-thin foil on a carrier to avoid distortion.
8. Inspection & Packaging — Measure slit width along its full length on a vision system, verify edge cleanliness, then pack with interleaving and a measured report.

Core Advantages

1. Burr-free slit edges: Chemical dissolution leaves no blade chipping or laser slag, so the aperture stays clean and stray light stays low.
2. No precision tooling: A new width or pitch is a new film, so multi-spec small runs carry no cutter cost and sample quickly.
3. Extremely fine, equal width: 0.02 mm slits hold on 0.05 mm foil and stay equal over tens of millimetres.
4. No heat-affected zone: Etching adds no heat, so the copper is not annealed or warped and flatness and reflectance stay constant.
5. Easy to blacken: Copper takes chemical blackening well, so the slit edge and face are de-glared together for lower inner-wall reflection.
6. Dimensional stability: A custom copper optical slit combines the uniform etch response of oxygen-free copper with optical-grade edges for high-accuracy dispersion and encoding.

Typical Applications

• Spectrometer entrance and exit slits: The light gate of a dispersive system, where slit width sets resolution and throughput.
• Encoder slit plates: Transmissive slit arrays in optical encoders whose equal-width consistency shapes pulse uniformity.
• Collimating apertures: Narrow-slit plates that limit beam width and divergence, with straight edges to reduce diffraction artifacts.
• Stray-light masks: Baffles in imaging systems that, once blackened, absorb off-axis light around the aperture.
• Laser shaping masks: Copper masks that trim a beam into a line or defined section, thin enough to mount directly.
• Metrology standards: Reference plates with certified slit widths used to calibrate microscopic and optical measurement gear.

Design Notes & Process Considerations

1. Width-to-thickness ratio: Keep the finest slit near half the foil thickness or more; a 0.02 mm slit in 0.05 mm foil needs side-etch compensation.
2. Etch factor and compensation: Double-sided etching tapers the wall, so call out finished slit width and allow an etch factor rather than quoting film size only.
3. Full-length equal width: Dimension slit width at both ends and the midpoint on long slits to prevent local widening from hurting transmission uniformity.
4. Blackening allowance: Name the blackening or matte coating system; a thick coating shrinks the effective slit, so remeasure after finishing.
5. Carrier and flatness: Process and ship ultra-thin foil on a carrier, and specify the release method to avoid bending the slit edge during handling.
6. Sampling and parameter lock: Approve a sample by microscopic image for width, equal-width consistency and edge quality, then lock the etch parameters for a custom copper optical slit before volume.