half‑etching photo etching
Photo etching (also known as photochemical machining / PCM) is a stress‑free subtractive manufacturing process for thin‑gauge metal sheets. Based on etching depth, mask layout and processing mode, photo etching can be divided into several core types. Each variant delivers unique geometry characteristics and fits different engineering requirements for filter mesh, encoder discs, shims, lead frames and bipolar platesMade-in-Ch….
1. Through‑Etching (Full Penetration Photo Etching)
Through‑etching is the most widely‑used photo etching type. Metal material is fully dissolved across sheet thickness to create complete cut‑outs, holes and part outlines.
‑ Process feature: Double‑sided photoresist masking, etchant attacks both top and bottom surfaces simultaneously, material penetrates completely.
‑ Key advantages: Burr‑free hole edges, zero mechanical stress, consistent aperture across thin foils.
‑ Typical applications: Microporous filter mesh, optical encoder discs, metal shims, gaskets, stencil sheets. ‑ Common material thickness range: 0.02 mm‑2.0 mm.
2. Half‑Etching (Partial‑Depth Etching)
Half‑etching removes partial material depth without penetrating the substrate. It creates recessed grooves, logos, text, channel patterns on one side while keeping base metal integrity. ‑ Process feature: Controlled etching time to achieve predefined depth, normally 20%‑70% of original sheet thickness. The opposite side remains intact.
‑ Key advantages: No through‑hole; can form flow channels, positioning grooves and marking features on flat metal blanks.
‑ Typical applications: Bipolar plate flow‑field channels, nameplate marking, positioning indentations, flexible circuit substrates.
‑ Note: Depth tolerance is affected by material thickness and etch time control.
3. Double‑Sided Photo Etching
Double‑sided photo etching applies patterned photoresist masks on both top and bottom sides of metal foil. Two‑sided spray etching proceeds synchronously. ‑ Process feature: Identical or different patterns can be designed on two sides. Balanced etching reduces undercut deviation and improves dimensional consistency.
‑ Key advantages: Symmetrical sidewall profile, high dimensional repeatability, ideal for through‑hole array production.
‑ Typical applications: Precision micro‑mesh, multi‑aperture filter components, high‑accuracy encoder code wheels.
4. Single‑Sided Photo Etching
Only one surface of the metal sheet is covered with patterned photoresist; the reverse side is fully protected by full‑area resist without graphic exposure. Etchant only attacks one face. ‑ Process feature: Etch proceeds from one direction only, leading to obvious tapered sidewall geometry.
‑ Key advantages: Suitable for one‑sided channel or cavity structure.
‑ Limitations: Larger undercut effect compared with double‑sided etching; less suitable for dense through‑hole arrays.
‑ Typical applications: Simple single‑sided half‑etched features, shallow cavity prototypes.
5. Taper‑Hole Photo Etching
Taper‑hole etching is a special derivative of double‑sided photo etching. Different aperture sizes are designed on top‑side and bottom‑side phototool patterns, generating conical tapered holes after etching.
‑ Process feature: Inlet hole dimension differs from outlet hole dimension, controllable taper angle.
‑ Typical applications: One‑way flow filter components, anti‑clogging sieve structures, special fluid‑control parts.
6. Bridge‑Free Photo Etching (Bridge‑Less Etching)
Bridge‑free photo etching removes all connecting micro‑bridges after etching. Individual finished parts are fully separated on the metal panel without residual tab connections.
‑ Process feature: Special phototool layout and process tuning; no break‑off bridges left on component edges.
‑ Typical applications: Ultra‑thin fragile micro‑parts, precision spring components that cannot retain bridge residues.
Quick Comparison Table for Photo Etching Types
| Etching Type | Core Feature | Key Application |
|---|---|---|
| Through‑Etching | Full material penetration | Filter mesh, encoder disc, shim, gasket |
| Half‑Etching | Partial depth, non‑penetration | Bipolar plate flow‑field, marking, groove |
| Double‑Sided Etching | Pattern on both sides, synchronous etching | Dense micro‑hole array, high‑precision parts |
| Single‑Sided Etching | Etch only from one surface | Shallow cavity, single‑sided groove prototype |
| Taper‑Hole Etching | Conical tapered through‑holes | Anti‑clog filter, one‑way fluid components |
| Bridge‑Free Etching | No connecting bridge left | Fragile ultra‑thin micro‑components |
How to Select Suitable Photo Etching Type
- If you need complete holes or separate parts: choose through‑etching, prefer double‑sided etching for dense micro‑holes.
- If you need grooves or channels without penetrating metal substrate: adopt half‑etching.
- Taper‑hole solution is recommended when fluid anti‑clog performance is required.
- For ultra‑thin fragile micro‑parts with no allowable bridge residue: specify bridge‑free photo etching.
Common Material for Photo‑Etched Components
Stainless steel 304 / 316L, copper, brass, nickel alloy, beryllium copper, titanium, spring steel.
If you have custom photo‑etched projects, provide your drawing with depth requirements, we will deliver DFM assessment and formal quotation.
