Etching Process in Metal

Etching process in metal is a subtractive manufacturing technology that removes unwanted metal material through chemical or electrochemical reaction, instead of cutting, stamping or mechanical grinding. By applying protective masking layers on metal surfaces, only exposed unmasked areas are dissolved, producing accurate twodimensional patterns, microholes, complex outlines, fine meshes, engraved texts and depthcontrolled recessed features. This stressfree, burrfree fabrication method works for sheets, foils and some formed conductive metal parts, widely deployed in electronics, automotive, medical devices, hydrogen energy, aerospace and instrumentation industries.

Two dominant industrial branches belong to metal etching process: wet photochemical etching (chemical etching) and electrochemical / electroetching. Their working principles, suitable scenarios, processing capacity and cost structure differ significantly.

1. Photochemical Wet Etching Process for Metal

Photochemical wet etching is the most widelyused etching process in metal for massproduction of thingauge precision components. It uses photoresist film as antietch mask and corrosive liquid etchant to selectively dissolve bare metal.

Step 1: DFM Design Review & Artwork Preparation

Engineers analyze customer CAD drawings, evaluate metal thickness, minimum hole size, trace width and spacing. Since wet etching is isotropic, etchant attacks metal both vertically and horizontally, generating undercut. DFM calculation adds undercut compensation into CAD artwork to guarantee final dimensional tolerance. Processlimitation issues are fed back for drawing optimization before production starts. The confirmed graphic data is output to UV exposure film.

Step 2: Metal Surface PreTreatment

Metal panels are cut to working size. Common processable metals cover stainless steel, copper, brass, nickel, Kovar, titanium and their alloys. Surface contaminants including rolling oil, fingerprints, dust and oxide films must be completely eliminated.

l Alkaline degreasing removes organic grease under heating and spray circulation.

l Multistage water rinsing washes away alkaline residues.

l Acid activation dissolves thin natural oxide layers and creates uniform microrough surface to boost photoresist adhesion.

l Pure water overflow rinsing removes acid residues. Poor cleaning directly causes photoresist delamination and batch defects.

Step 3: Dryfilm Photoresist Lamination

Dryfilm photoresist is hotlaminated onto both sides of clean metal substrate under precise temperature and pressure control. No air bubbles are allowed between resist and metal. Trapped bubbles let etchant penetrate underneath and destroy graphic patterns. Laminated panels cool down for stable resist performance.

Step 4: UV Exposure

Exposure film is closely aligned against photoresist surface. Highintensity UV light passes through transparent graphic zones to crosslink and cure photoresist. Areas covered by black film remain unpolymerized. Exposure energy must be strictly controlled: overexposure blurs graphic edges; underexposure leads to insufficient resist curing and mask failure during etching. Doublesided parts require highprecision frontback alignment.

Step 5: Developing

Panels pass through spray developer tank with dilute alkaline solution. Unexposed soft photoresist is rinsed away, exposing bare metal areas ready for etching. UVhardened resist remains as protective mask. Concentration, temperature, spray pressure and conveyor speed determine pattern resolution. After developing, thorough water rinsing and magnified visual inspection confirm pattern integrity.

Step 6: Spray Chemical Etching

Panels enter enclosed horizontal spray etching equipment. Custommatched etchant is continuously sprayed onto workpiece surfaces. Maskprotected metal remains intact; exposed metal reacts and dissolves. Ferric chloride etchant is standard for stainless steel, copper and nickel alloys. Aluminum uses alkaline etchant; titanium and highnickel superalloys adopt special mixedacid formulations.

Etching depth is controlled by conveyor speed, etchant temperature, spray pressure, solution concentration and circulating filtration system. For throughetch products, metal material is fully dissolved through sheet thickness. For blindetch jobs, immersion time inside etching chamber defines target depth. After reaching required depth, parts are immediately rinsed to eliminate residual corrosive liquid.

Step 7: Photoresist Stripping

Heated alkaline stripping solution breaks polymer structures of cured photoresist mask, so protective film peels off completely from metal components. Process time and temperature are carefully adjusted to avoid corrosion of soft metals. Multicascade water rinsing removes all chemical residues.

Step 8: PostTreatment and Quality Control

Optional secondary operations include passivation, polishing, plating, coloring and depaneling. Final inspection measures dimension, aperture, sidewall quality and surface appearance. Qualified metal parts go for packaging and delivery.

2. Electrochemical (Electro) Etching Process in Metal

Electrochemical etching, also known as electrolytic etching, combines directcurrent electricity with conductive electrolyte solution. The conductive metal workpiece acts as anode. When electric current flows through electrolyte, unmasked metal surface dissolves via anodic reaction. Insulated mask shields regions that need preservation.

This metal etching process is mainly applied for shallow engraving, marking logos, serial numbers and scale texts. It works well for flat or bent, stamped formed metal parts. It does not rely on highlyconcentrated corrosive acid as the primary driving force. However, it is less efficient for full throughetch of thickgauge metal components.

Main workflow: workpiece degreasing and activation → mask or stencil application → fixture connection for anodecathode circuit → controlled current density electrolytic etching → rinsing and mask removal → posttreatment and inspection.

Material Compatibility for Metal Etching Process

l Excellent compatibility: 304 / 316 stainless steel, copper, brass, phosphor bronze, nickel, Kovar alloy. Most suitable for massvolume photochemical wet etching.

l Conditional processing: aluminum alloy, titanium alloy. Require dedicated etchant or electrolyte formulas. Process window is narrower.

l Not applicable: nonmetallic materials and nonconductive coated metals without prior coating removal.

Core Advantages of Etching Process in Metal

1. Zero burr, zero mechanical stress: No cutting force applied. Ultrathin metal foils will not deform.

2. No expensive hard tooling: Pattern modification only needs CAD file update. Short leadtime for prototypes and smallbatch orders.

3. High resolution for complex features: Capable of microholes, dense meshes, intricate profiles that are difficult for stamping or laser cutting.

4. Dualsided uniform processing: Photochemical etching achieves consistent features on both sides of metal sheet.

5. Wide material adaptability: Supports multiple ferrous and nonferrous metal alloys.

Key Limitations of Metal Etching Process

1. Inherent isotropic effect creates unavoidable undercut (side erosion). DFM compensation is mandatory for precise finefeature production.

2. Best performance for thinsheet metal. As material thickness increases, etching cycle extends and undercut value rises.

3. Wet photochemical etching is primarily for 2dimensional planar structures, not fit for complex deep 3D geometries.

4. Electrochemical etching suits shallow marking rather than deep or full throughetch mass production.

Typical Industrial Applications of Metal Etching Process

l Electronics industry: encoder discs, shielding components, lead frames, precision contact springs

l New energy: hydrogenenergy flowfield plates, filter meshes for battery systems

l Medical industry: nebulizer microorifice plates, surgical instrument components

l Automotive: horn grilles, spring contact pieces, precision gaskets

l Instrumentation: fine meshes, shims, custom metal filters, scale marking parts

Conclusion

Etching process in metal covers two major industrial routes: photochemical wet etching and electrochemical etching. Wet photochemical etching dominates highvolume manufacturing of thingauge intricate metal components. Electrochemical etching shines for shallow marking and engraving, especially on preformed metal workpieces. Stable production output depends on DFM compensation, strict surface pretreatment, proper mask selection and precise control over liquid or electrical parameters. When stamping, laser cutting or CNC machining encounter bottlenecks on thin, complex, burrfree precision metal parts, metal etching process provides a reliable and economical manufacturing alternative.