Overview

A custom copper slit plate is a copper sheet carrying a set of parallel rectangular long slits or a regularly spaced slit array for collimation, baffling and spectroscopy. A dry-film resist is imaged with the array pattern, developed, and the exposed metal is dissolved, leaving slits of uniform width with straight, burr-free walls. Stock is typically oxygen-free copper C10100 or C110 between 0.05 mm and 0.5 mm. Because whole-sheet chemical removal adds no heat-affected zone or mechanical stress, a custom copper slit plate keeps its pitch and slit width consistent from sample to volume, and the copper face takes blackening well for stray-light control.

For optical and equipment engineers, the custom copper slit plate controls what a multi-slit array makes hardest: adjacent pitch held to a few tenths of a millimetre over the full length, dozens of slits kept strictly parallel, and any edge burr producing diffraction fringes that disturb the signal. Etching forms the whole array in one operation, so changing width or slit count is a new film rather than cutting each slit, which keeps multi-spec prototypes economical. Collimator slit arrays, multi-channel spectrometer apertures, encoder masking plates and imaging baffles all rely on dense, parallel, clean etched copper slit plates.

Parameter Window

• Available Materials: oxygen-free copper C10100, copper C110, phosphor bronze, brass as an alternative
• Material Thickness Range: 0.05–0.5 mm (0.1 mm, 0.2 mm and 0.3 mm for most arrays)
• Tolerance: ±0.01 mm on slit width, ±0.02 mm on pitch, ±0.05 mm on outline
• Minimum Feature: 0.05 mm slit width, 0.1 mm web between slits, parallelism 0.02 mm per 10 mm
• Surface Options: bare passivated, chemical blackening, Ni plating, matte anti-reflection coating
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Artwork Review — Vectorize the slit array, check width, pitch, web and parallelism requirements, and set registration datums.
2. Material Selection — Choose copper grade for slit width and stiffness, and reject sheet with scratches or creases that break fine webs.
3. Cleaning & Lamination — Degrease and laminate dry film on both faces so no bubble or residue sits under fine slits and narrow webs.
4. UV Exposure — Expose through high-resolution film registered to the sheet edge so all slits stay parallel across the plate.
5. Development — Open the slit areas and inspect each slit under a microscope for complete development and through-cut.
6. Etching — Spray copper-matched chemistry with controlled time and temperature to stop side-etch narrowing webs or widening slits.
7. Stripping & Finishing — Remove resist, neutralize, then blacken or apply matte coating, and flatten if needed to hold pitch.
8. Inspection & Packaging — Measure slit width, pitch and parallelism on a vision system, then pack with interleaving and a measured report.

Core Advantages

1. Precise pitch: One-shot whole-sheet imaging shares a single datum, so pitch and parallelism beat slit-by-slit machining.
2. Burr-free slit edges: Chemical removal leaves no slag or chipping, so clean apertures cut diffraction fringes and stray light.
3. No per-slit tooling: A new width or slit count is a new film, so multi-spec small runs avoid cutter cost.
4. No thermal distortion: Etching adds no heat, so fine webs do not anneal or warp and plate flatness stays stable.
5. Easy to de-glare: Blackened copper de-glares slit edges and face together, suppressing reflection between slits.
6. Array consistency: A custom copper slit plate combines copper's uniform etch response with multi-slit array accuracy for multi-channel optics.

Typical Applications

• Collimator slit arrays: Slit sets that shape a source into parallel lines, where pitch sets the line spacing.
• Multi-channel apertures: Multi-channel spectrometer entrance plates whose equal widths unify channel response.
• Encoder masking plates: Transmissive slit arrays in optical encoders whose parallelism shapes signal phase consistency.
• Imaging baffles: Baffles in front of cameras and detectors that, once blackened, absorb out-of-field light.
• Beam-shaping masks: Copper masks that trim an area source into strips or spot arrays and mount easily.
• Metrology standards: Reference plates with certified pitch used to calibrate imaging and displacement measurement gear.

Design Notes & Process Considerations

1. Width-to-thickness ratio: Keep the finest slit near half the foil thickness or more; a 0.05 mm slit in 0.1 mm sheet needs side-etch review.
2. Web and parallelism: Hold the web at or above stock thickness and call out parallelism per 10 mm on the drawing.
3. Etch factor: Double-sided etching tapers the wall, so specify finished slit width and allow a side-etch compensation.
4. Blackening allowance: Name the blackening or matte coating system; a thick coating shrinks effective slit width, so remeasure after finishing.
5. Flatness and carrier: Call out flatness and ship thin plates on a carrier so narrow webs are not bent during handling.
6. Sampling and lock: Approve a sample for slit width, pitch and parallelism, then lock the etch parameters for a custom copper slit plate before volume.