What is photo etching
Photo etching, also commonly called photochemical machining (PCM), is a precision metal fabrication technique that uses light-sensitive photoresist and chemical etchant to selectively remove metal material. It is ideal for thin metal foils to create complex 2D geometries without hard tooling.
1. Core Working Principle
A thin layer of photoresist is coated onto the metal sheet. The artwork pattern is transferred onto the resist by UV exposure. After developing, the resist protects the areas that remain, while the bare metal regions are dissolved away by chemical etchant. The remaining resist is stripped off to get the finished part.
2. Step-by-Step Process
- Material selection: Thin metal foil such as stainless steel, copper, brass, nickel, titanium.
- Cleaning: Remove oil, dust and surface contaminants.
- Photoresist lamination: Apply light-sensitive resist film on both sides of the metal.
- Exposure: UV light transfers the CAD pattern onto the photoresist through a film mask.
- Developing: Wash away unexposed resist to reveal the metal areas to be etched.
- Etching: Chemical solution eats away the exposed metal from both sides simultaneously.
- Stripping: Remove the remaining protective photoresist.
- Inspection & post-treatment: Dimensional check, deburring, passivation, flattening, packaging.
3. Key Advantages
- No expensive hard tooling; low setup cost, fast prototyping.
- Excellent consistency for dense micro holes, fine meshes and encoder discs.
- Tight dimensional tolerance for ultra-thin metal (0.02 mm ~ 1.5 mm typical).
- Burr-free and stress-free parts, no mechanical deformation.
- Complex patterns cost almost the same as simple shapes.
4. Limitations
- Mainly for thin metal foils, not suitable for thick heavy plates.
- Material thickness limits feature size; minimum hole size is roughly equal to material thickness.
- Not recommended for deep 3D structures, only 2D flat components.
5. Typical Applications
Filter mesh, optical encoder discs, metal shims, bipolar plate flow field, lead frames, EMI shielding parts, coffee filter mesh, automotive oil filter screens.
