---
type: process
name: "Photo Etching"
category: "Finishing"
subcategory: "Subtractive"
materials: ["Metal"]
tolerances: "±10–20% of material thickness is standard; approximately ±0.001 in (±0.025 mm) achievable on thin foil. Half-etch depth is controlled to a residual thickness rather than to a depth dimension"
volumes: "1 to several hundred thousand parts; the same tooling serves prototype and production"
lead_time: "3–10 business days including phototool; prototypes in 1–3 days at some suppliers"
url: https://manufacturingprocesses.org/processes/finishing/photo-etching
---

# Photo Etching

Photo etching masks a surface photographically and etches shallow detail into it for decoration, marking or texture.

- **Category**: [Finishing](https://manufacturingprocesses.org/processes/finishing.md)
- **Family**: Subtractive
- **Materials**: Metal
- **Typical tolerances**: ±10–20% of material thickness is standard; approximately ±0.001 in (±0.025 mm) achievable on thin foil. Half-etch depth is controlled to a residual thickness rather than to a depth dimension
- **Surface finish**: Etched surfaces come out uniformly matte; the incoming sheet finish is preserved on unetched areas
- **Typical volumes**: 1 to several hundred thousand parts; the same tooling serves prototype and production
- **Lead time**: 3–10 business days including phototool; prototypes in 1–3 days at some suppliers

## Overview

Photo etching masks a metal surface photographically and dissolves the unmasked areas with a chemical etchant. Because a photoresist can resolve fine detail and an etchant does not care how complicated the pattern is, artwork complexity costs nothing — a surface covered in thousands of individual features etches in the same time as a single one.

Used as a finishing process, it produces shallow decorative texture, logos, scales, grip patterns and permanent part marking in a controlled depth, typically half-etched to 30–50% of material thickness. Used as a cutting process, the same chemistry produces complete parts from foil 0.001–0.060 in (0.025–1.5 mm) thick. In both roles the defining advantages are that nothing touches the workpiece: no burrs, no work hardening, no heat-affected zone, no cutting forces and no distortion. Tooling is a photographic film rather than a hardened die, so lead time is days and cost is a small fraction of a stamping tool.

## How it works

1. **Make the phototool.** The artwork is imaged onto a film or glass phototool, in a matched pair for double-sided work. This is the only tooling in the process and it is inexpensive and fast to revise.

2. **Clean and laminate.** The sheet is chemically cleaned, then a photosensitive dry-film resist is laminated to one or both faces under heat and pressure. Cleanliness governs resist adhesion and therefore edge quality.

3. **Expose and develop.** UV light through the phototool polymerizes the resist in the areas that must survive. Developing washes away the unexposed resist and leaves bare metal exactly where etching should occur.

4. **Etch.** The sheet passes through a spray etcher. Ferric chloride at roughly 120–130 °F (49–54 °C) is the standard etchant for stainless, carbon steel, copper alloys and nickel; aluminum and titanium use different chemistries. Etch time controls depth. Because chemical attack is essentially isotropic, the etchant cuts sideways as fast as it cuts down, producing a characteristic undercut beneath the resist edge.

5. **Strip and inspect.** The remaining resist is chemically stripped, and the part is rinsed and dried.

### Etch factor and the cusped edge

Isotropic attack means that a through-etched feature is never a straight-sided cut. Etching from one side produces a tapered wall; etching from both sides produces an hourglass profile with a small ridge, or cusp, at mid-thickness. This is the geometric reason minimum feature size scales with material thickness — a rule of thumb is that the smallest reliable hole or slot is about 1.0–1.2 times the sheet thickness.

### Half etching

Stopping the etch part way through gives a controlled recess. Etching to 30–50% of thickness is used for surface decoration, permanent marking, bend lines that let a flat part fold accurately by hand, and countersinks and pockets that would otherwise require machining.

## Design guidelines

### Scale every feature to material thickness

Minimum hole diameter and slot width run about 1.0–1.2 times the material thickness, and minimum web or land width follows the same rule. Achievable tolerance is typically expressed as a fraction of thickness — on the order of ±10–20% of material thickness — with roughly ±0.001 in (±0.025 mm) achievable on thin foils. Thicker material means coarser everything.

### Expect a tapered or cusped edge

A one-sided etch leaves a taper; a two-sided etch leaves an hourglass with a small ridge at mid-thickness. Where a square edge is required — a bearing surface, a press fit, a precision aperture — photo etching is the wrong process or the feature needs a secondary operation.

### Use half etching deliberately

Etching to 30–50% of thickness gives decorative texture, permanent identification that cannot rub off, and fold lines that make an accurate hand-formed part from flat stock. Specify the residual thickness rather than the etch depth, because the process controls how much is removed and the remaining web is what matters structurally.

### Design for the sheet, not the part

Photo etching processes a whole panel at once, so cost scales with panel area and the number of panels, not with the number of features. Nest densely, put every variant on one panel, and add tabs to hold parts in the sheet if they must ship as a array.

### Choose an etchable material

Stainless steels, copper alloys, brass, beryllium copper, nickel alloys, molybdenum and spring steels all etch well and cover most applications. Aluminum and titanium require different etchants and are less commonly offered. Hardened, plated and heavily cold-worked surfaces etch unevenly.

### Take advantage of what it does not do

Because there is no tooling contact and no heat, the material comes out with its temper unchanged and no burr — which is why photo etching is chosen for spring elements, shims, EMI shielding, lead frames, encoder discs and fine mesh where a stamped or laser-cut edge would need deburring or would alter the material.

| Feature | Recommended | Limit | Why |
| --- | --- | --- | --- |
| Material thickness | 0.001–0.060 in (0.025–1.5 mm) | Thicker material coarsens every feature | Etch time and undercut scale with depth |
| Minimum hole / slot | 1.2 × material thickness | 1.0 × thickness | Isotropic undercut limits aspect ratio |
| Tolerance | ±10–20% of material thickness | ±0.001 in (±0.025 mm) on thin foil | Etch rate variation across the panel |
| Half-etch depth | 30–50% of thickness | Specify residual web, not depth | Remaining material carries the load |
| Edge profile | Tapered or cusped | Not square | Chemical attack is isotropic |
| Tooling | Photographic film | Revised in hours | No hard tooling exists |

## Cost drivers

Photo etching is priced by panel area and the number of process passes, which produces a cost structure unlike any mechanical cutting process: complexity is free, and area is everything.

- **Panel area and nesting.** The cost of a panel is fixed, so parts per panel is the dominant variable. A dense nest can cut unit cost several-fold.
- **Material.** Thickness and alloy affect both raw material cost and etch time. Stainless etches slower than copper.
- **Number of etch stages.** A simple through-etch is one pass. A part with half-etched features on one side and through-etched features elsewhere needs additional resist and etch steps.
- **Tooling.** A phototool costs a small fraction of a stamping die and can be revised in hours, which is why photo etching dominates prototyping and design iteration for thin metal parts.
- **Secondary operations.** Forming, plating, tab removal and passivation are all separate operations after etching.

Cost-reduction tactics:

1. Nest as many parts per panel as the geometry allows — this is the single biggest lever.
2. Add features rather than removing them if it improves nesting; complexity genuinely costs nothing.
3. Use a single etch depth across the whole part where possible to avoid extra masking stages.
4. Specify the loosest tolerance the function permits; the tightest tolerances require slower, more controlled etching.
5. For high-volume simple parts, compare against stamping — above roughly a hundred thousand pieces the die cost amortizes and stamping wins on unit price, while photo etching wins everywhere below that and on any burr-free requirement.

## FAQ

### What tolerance can photo etching hold?

Typically ±10–20% of material thickness, with about ±0.001 in (±0.025 mm) achievable on thin foils. Minimum hole and slot sizes run roughly 1.0–1.2 times the material thickness, because chemical attack is isotropic and undercuts sideways as fast as it etches down.

### Why do photo-etched edges have a taper or a ridge?

Etching is isotropic — it removes material sideways at the same rate it removes it downward. A one-sided etch leaves a tapered wall; a two-sided etch leaves an hourglass profile with a small ridge at mid-thickness. Where a square edge is required, the feature needs a secondary operation.

### What is half etching used for?

Etching to 30–50% of material thickness produces decorative surface texture, permanent identification that cannot rub off, bend lines that let a flat part be folded accurately by hand, and shallow pockets or countersinks. Specify the residual web thickness rather than the etch depth, since the remaining material is what carries load.

### Does photo etching leave burrs or change the material?

No on both counts. Nothing touches the workpiece and there is no heat input, so the material comes out with no burr, no work hardening, no heat-affected zone and its temper unchanged. That is why the process is used for spring elements, shims, EMI shielding, encoder discs and fine mesh.

### Which materials can be photo etched?

Stainless steels, carbon and spring steels, copper alloys, brass, beryllium copper, nickel alloys and molybdenum all etch well in ferric chloride at roughly 120–130 °F (49–54 °C). Aluminum and titanium need different etchants and are less commonly offered. Hardened, plated or heavily cold-worked surfaces etch unevenly.

### How does photo etching compare to laser cutting or stamping on cost?

Photo etching prices by panel area rather than by cut length, so pattern complexity is free and dense nesting is the main cost lever. Tooling is a photographic film that costs a small fraction of a stamping die and can be revised in hours. Above roughly a hundred thousand simple parts, a stamping die amortizes and wins on unit price.

## Alternative processes

- [Photochemical Machining](https://manufacturingprocesses.org/processes/cutting/photochemical-machining.md): Photochemical machining masks sheet metal photographically and etches away the unmasked areas, cutting burr-free flat parts with no hard tooling.
- [Laser Cutting](https://manufacturingprocesses.org/processes/cutting/laser-cutting.md): Laser cutting melts, burns or vaporises a narrow kerf through flat stock with a focused beam, producing profiles from a 2D file with no tooling.
- [Punching and Blanking](https://manufacturingprocesses.org/processes/cutting/punching-and-blanking.md): Punching and blanking shear sheet metal between a punch and a die, producing holes and flat outlines at very high speed.
- [Laser Marking and Engraving](https://manufacturingprocesses.org/processes/finishing/laser-marking-and-engraving.md): Laser marking alters the surface with a focused beam — annealing, etching or engraving it — to make permanent, contact-free marks.
- [CNC Engraving](https://manufacturingprocesses.org/processes/finishing/cnc-engraving.md): CNC engraving cuts text and artwork into a surface with a small pointed or ball-nose tool following a programmed path.

## Related processes

- [Photochemical Machining](https://manufacturingprocesses.org/processes/cutting/photochemical-machining.md): Photochemical machining masks sheet metal photographically and etches away the unmasked areas, cutting burr-free flat parts with no hard tooling.
- [Laser Marking and Engraving](https://manufacturingprocesses.org/processes/finishing/laser-marking-and-engraving.md): Laser marking alters the surface with a focused beam — annealing, etching or engraving it — to make permanent, contact-free marks.
- [CNC Engraving](https://manufacturingprocesses.org/processes/finishing/cnc-engraving.md): CNC engraving cuts text and artwork into a surface with a small pointed or ball-nose tool following a programmed path.
- [Electropolishing](https://manufacturingprocesses.org/processes/finishing/electropolishing.md): Electropolishing reverses plating: current dissolves the surface fastest at the peaks, leaving a bright, deburred, passive finish.
- [Passivation](https://manufacturingprocesses.org/processes/finishing/passivation.md): Passivation removes free iron from a stainless steel surface with an acid bath so the chromium oxide layer can reform unbroken.

---

*Source: [Manufacturing Processes](https://manufacturingprocesses.org/processes/finishing/photo-etching)*

*Last updated: August 11, 2026*