Overview

An etched molybdenum grating is a fine-pitch optical or X-ray grating cut into thin molybdenum sheet by photochemical machining, chosen where thermal stability and stiffness matter more than conductivity. A photoresist mask is exposed with the grating artwork, developed, and the unprotected molybdenum is dissolved in a controlled alkaline or acidic spray, so line width, pitch and duty cycle are set by the artwork and etch time rather than by a ruling engine or die. Typical stock is pure molybdenum (Mo 99.95% min) and TZM molybdenum alloy between 0.03 mm and 0.25 mm, valued for a melting point above 2600 C, low thermal expansion and high modulus that keep the pitch stable under heat load.

For spectroscopy and metrology buyers, an etched molybdenum grating solves three recurring problems: mechanically ruled lines carry burrs and edge waviness that add stray-light noise, pitches down to 0.04 mm are hard to hold over a long scale, and molybdenum is brittle and refractory so stamping or laser cutting cracks foils and leaves a recast layer. Chemical machining forms every line on a sheet at the same rate, holding pitch and duty cycle consistent from the first sample through volume production, while leaving the grating flat, stress-free and dimensionally stable in high-temperature or vacuum instruments.

Parameter Window

• Available Materials: pure molybdenum Mo 99.95% min, TZM molybdenum alloy, molybdenum-copper; also stainless and nickel for mixed builds
• Material Thickness Range: 0.03–0.25 mm
• Tolerance: ±0.004 mm on line width, ±0.008 mm on pitch and position
• Minimum Feature: 0.015 mm line/slot width, 0.04 mm grating pitch
• Surface Options: electropolishing, acid pickling, vacuum anneal, matte blackening, ultrasonic cleaning
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Artwork & Nesting — Convert the grating pattern to vector art, verify line-to-thickness and pitch rules, and lay out panels with shared fiducials.
2. Material Certification & Prep — Verify Mo purity, mill certificate and thickness, inspect for cracks and flatness, then shear to exposure size.
3. Cleaning & Lamination — Degrease and laminate dry-film resist on both faces under matched heat and pressure without trapped bubbles.
4. UV Exposure — Expose the grating artwork through high-resolution film, registered to the sheet edge for panel-level pitch accuracy.
5. Development — Wash out unexposed resist to open the slot areas and inspect for residue that would blur line edges.
6. Controlled Etching — Spray molybdenum-matched chemistry, tuning time, temperature and conveyor speed to hold line width and avoid undercut.
7. Stripping & Anneal — Strip resist, neutralize, then vacuum-anneal and electropolish or blacken for a stable, low-scatter surface.
8. Inspection & Packaging — Measure line width, pitch and duty cycle on a vision system, verify flatness, then pack between liners in clean trays.

Core Advantages

1. Burr-free line edges: Chemical removal leaves no rolled burr or recast layer, so stray-light scatter at the grating stays low.
2. No hard tooling: Each pitch or duty cycle is a new film, keeping one-off scales and frequent revisions economical without a ruling die.
3. Thermal pitch stability: Molybdenum's low expansion and high modulus hold pitch under heat load in vacuum and high-temperature instruments.
4. Fine, uniform pitch: 0.015 mm lines and 0.04 mm pitches hold ±0.004 mm across a full panel with consistent duty cycle.
5. Stress-free flatness: With no shear or heat input, thin foil stays flat, so bonding to a holder will not warp the grating.
6. Repeatable custom patterns: An etched molybdenum grating can combine multiple pitches, index marks and code tracks on one part, reproduced from first article to volume.

Typical Applications

• X-ray & EUV gratings: Diffraction and dispersion elements that must stay dimensionally stable under high radiant load.
• Spectrometer diffraction plates: Fine-slit and grating plates for wavelength separation in compact analytical instruments.
• High-temperature metrology scales: Moiré and linear scales for stages and fixtures operating in heated environments.
• Optical encoder discs: Rotary and linear code tracks where edge quality sets signal contrast and resolution.
• Laser beam-splitting masks: Aperture and grating plates for structured-light and beam-shaping optics.
• Vacuum instrument baffles: Low-outgassing, heat-stable slit arrays inside electron and vacuum optical systems.

Design Notes & Process Considerations

1. Line-to-thickness ratio: Keep line and slot width at or above roughly the foil thickness; very fine lines in thick stock distort from undercut.
2. Pitch and duty cycle: State line width, pitch, duty cycle and total track length, rather than only a line count, for reliable diffraction performance.
3. Grade selection: Choose pure Mo for maximum temperature stability, or TZM for strength, and note the purity and certificate needs.
4. Surface and scatter: Define electropolish, blackening and vacuum-anneal state, since surface finish and stress strongly affect stray light.
5. Tie bars and borders: Leave adequate tie bars and process borders, and specify final singulation so fine lines survive stripping and cleaning.
6. Handling and cleanliness: With an etched molybdenum grating, specify liner packaging, fingerprint control and residual-ion limits for clean vacuum assembly.