Metal etching, also commonly known as chemical etching or photochemical machining, is a subtractive cold manufacturing technology that removes unwanted material from metal sheets and foils by means of controlled chemical dissolution. Unlike stamping, CNC milling or laser cutting, metal etching requires no mechanical contact, no cutting force and minimal heat input during production. It can turn flat metal blanks into complex, burrfree, stressfree twodimensional precision parts, which makes it widely adopted across electronics, aerospace, medical devices, new energy, automotive and chemical industries.

At its core, metal etching works on a simple principle: selected areas of metal are exposed to corrosive etchant solutions, while the remaining functional areas are protected by a chemicalresistant masking layer, most typically UVcured photoresist. Only the unprotected exposed metal will react and dissolve away. By controlling etchant composition, temperature, spray pressure and processing time, manufacturers can precisely control etching depth, aperture size, feature width and overall component geometry. The process is mostly isotropic, which means metal dissolves both vertically downwards and sideways, creating predictable undercut that must be compensated at the design stage.

There are two primary industrial branches of metal etching: wet chemical etching and electrochemical etching. Wet chemical etching is the mainstream massproduction method, using liquid chemical etchant sprayed onto metal panels. Electrochemical etching applies direct current together with electrolyte to remove metal material, frequently used for surface texturing and shallow marking. Dry plasma etching is mostly confined to ultrathin wafers within semiconductor manufacturing and rarely applied for thick industrial metal sheet components.

1. Typical StepbyStep Workflow of Industrial Metal Etching

Step 1: DFM Design for Etching

Design for manufacturability review is the starting point. Engineers analyse customer CAD drawings, evaluate minimum hole size, web width, material thickness and panel nesting. Since side undercut is unavoidable for isotropic etching, appropriate geometric compensation is added to the phototool artwork to offset lateral material loss. Unrealistic tiny features are fed back for design adjustment.

Step 2: Surface PreTreatment

Metal substrates go through degreasing to eliminate oil, grease, fingerprints and surface contaminants. Cleaning and mild surface roughening create good surface condition for photoresist adhesion. Poor pretreatment will cause resist peeling, pattern distortion and reject parts.

Step 3: Dryfilm Photoresist Lamination

Acidresistant dryfilm photoresist is hotroll laminated onto both sides of the cleaned metal sheet. Lamination parameters are tightly controlled to eliminate bubbles and wrinkles. Bubbles allow etchant to penetrate under the mask and ruin part patterns.

Step 4: UV Exposure

The compensated phototool film is aligned to the resistcovered metal. Highintensity UV light cures the photoresist in the desired part areas. Cured resist becomes chemically inert against etchant and acts as protective mask. Unexposed regions remain soluble for later developing. Doublesided exposure is standard for throughetched components such as meshes and filters.

Step 5: Developing

Panels pass through alkaline developer solution. Uncured photoresist dissolves completely, opening clear windows where metal will be etched. Cured protective masking stays firmly bonded to the metal surface. Automatic optical inspection is often performed to catch pinholes or resist residues before etching.

Step 6: Chemical Etching (Core Stage)

Workpieces travel through a closedloop spray etching chamber. Customformulated etchant is sprayed onto exposed metal surfaces. Metal dissolves selectively in open windows. Conveyor speed, liquid temperature, pressure and chemical concentration are strictly monitored to achieve target depth or full throughetch. Once dimensions meet specifications, etching stops immediately to avoid overetching.

Step 7: Stripping and Rinsing

After etching, the protective photoresist mask is stripped off using hot alkaline solution. Multistage water rinsing removes residual etchant and stripping chemicals to prevent postprocess corrosion.

Step 8: PostTreatment and Quality Inspection

Depending on application requirements, parts may go through passivation, cleaning, drying or surface finishing. Metrology equipment verifies dimension, flatness and edge quality. AOI scanning checks for cracks and pattern defects. Batch production records are archived for traceability.

2. Common Etchable Metals

Metal etching supports a wide range of thingauge metallic materials:  Stainless steel: 304, 316, 430, widely used for gaskets, meshes and shims  Copper, brass, phosphor bronze: for EMI shielding, spring contacts and lead frames  Nickel and nickelbased superalloys: for hightemperature and corrosionresistant components  Titanium & titanium alloys: for medical, hydrogen energy and anticorrosion filter parts  Other special metals: niobium, tantalum, kovar and certain aluminium alloys

Process feasibility, etching rate and tolerances vary greatly for different metal grades. Each material requires matched etchant formula and process parameters.

3. Main Advantages of Metal Etching

Burrfree and stressfree: No mechanical stamping force; no burrs, workhardening or residual stress. Original material mechanical and chemical properties remain unchanged.

No expensive hard tooling: Part geometry is defined by phototool film. Design revisions only require new artwork, significantly lowering cost for prototypes and lowvolume runs.

High complexity capability: Intricate contours, dense microhole arrays, fine meshes and multifeature sheets can be produced in one single process step.

Consistent parttopart quality: Once process parameters are stabilised, metal etching delivers excellent repeatability for mediumtolargebatch production.

Broad material & thickness range: Works for ultrathin foils starting from 0.02 mm up to several millimetres thin metal sheets.

4. Process Limitations

Metal etching is isotropic subtractive manufacturing, so lateral undercut always occurs. There are practical limits for ultrasmall hole and ultranarrow web dimensions. Material thickness directly restricts minimum feature size. Etching consumes chemical solutions and requires wasteliquid treatment. For very thick metal plates or simple highvolume blanking parts, stamping or laser processing may be more economical.

5. Typical Industrial Applications

Metaletched components are extensively used for precision shims, gaskets, filter meshes, encoder discs, lead frames, spring contacts, flowfield plates, shielding parts, medical functional sheets and automotive microcomponents. It covers prototype verification, smallbatch trialrun and massvolume manufacturing.

Conclusion

Metal etching is a versatile cold subtractive manufacturing process for thin metal sheets. By using chemical dissolution with photoresist masking, it produces complex precision metal parts free of burrs and internal stress. Its toolfree characteristic brings great flexibility for custom geometries across multiple industries. Understanding material characteristics, isotropic undercut rules and DFM constraints is essential to obtain highquality etched metal components.