Etching of metals, also widely named chemical etching or photochemical machining, is a subtractive cold manufacturing process that removes unwanted material from thin metal sheets and foils by controlled chemical dissolution. Unlike stamping, CNC machining or laser cutting, etching of metals does not rely on mechanical cutting force or highheat melting. It protects the required part geometry with corrosionresistant masking material and only dissolves unprotected metal areas. This technology can produce complex twodimensional precision components with burrfree edges and zero residual stress, and is extensively used in electronics, new energy, medical devices, aerospace, automotive and chemical industries.

The core working principle of etching of metals belongs to isotropic chemical corrosion. Selected metal surfaces are covered with acidresistant photoresist mask, while the areas to be removed are fully exposed to special etchant solution. Metal substrates react with etchant and dissolve away both vertically and laterally. The etching depth, aperture size and feature width are controlled by adjusting etchant composition, temperature, spray pressure and processing dwell time. Lateral undercut is an inherent feature of isotropic etching, which must be compensated at the phototool design stage to guarantee final dimensional accuracy.

Industrial etching of metals is mainly divided into two categories: wet chemical etching and electrochemical etching. Wet photochemical etching is the dominant massproduction solution for thin metal components. Electrochemical etching uses electrolyte plus direct current for material removal, mostly applied for shallow surface marking and texturing. Dry plasma etching is mainly applied for ultrathin semiconductor wafers and seldom used for general industrial metal sheets.

1. Complete Industrial Workflow for Etching of Metals

Step 1: DFM Review and Phototool Making

Engineers review customer CAD drawings for manufacturability, assess material thickness, minimum hole dimension, web width and panel nesting layout. Add corresponding compensation for lateral undercut into phototool artwork. Features beyond process limits will be fed back for drawing optimisation. Confirmed phototool film will be prepared for UV exposure.

Step 2: Surface PreTreatment

Raw metal panels go through alkaline degreasing to eliminate oil, fingerprints and surface contaminants. Subsequent rinsing and mild microroughening build uniform surface condition for reliable photoresist adhesion. Poor pretreatment will trigger resist peeling, pattern seepage and mass rejection. Reactive alloys such as titanium and niobiumtitanium need customtuned pretreatment formula.

Step 3: Dryfilm Photoresist Lamination

Acidresistant dryfilm photoresist is hotroll laminated onto both sides of cleaned metal substrate. Lamination temperature, roller pressure and feeding speed are precisely adjusted to eliminate bubbles and wrinkles. Bubbles will cause etchant penetration under mask and destroy fine patterns, especially for dense micromesh structures. Panels remain stationary for thermal stabilisation after lamination.

Step 4: UV Exposure

Compensated phototool is precisely aligned with resistcovered metal sheet. Highintensity UV light cures photoresist on reserved part regions, forming a stable corrosionproof protective mask. Unexposed areas keep soluble for developing. Doublesided alignment exposure is required for throughetched mesh and perforated sheets to achieve symmetric topbottom geometry.

Step 5: Developing and Preetch AOI Inspection

Panels pass through alkaline developer solution. Uncured photoresist dissolves completely and opens clean etching windows. Cured masking stays firmly bonded on metal surface. Automatic optical inspection checks pinholes, resist residues and pattern offset. Defective panels are eliminated before etching to save production cost.

Step 6: Core Chemical Etching

Clamped workpieces travel through closedloop spray etching chamber. Materialmatched etchant is sprayed continuously onto exposed metal windows. Selective chemical dissolution takes place. Realtime monitoring covers conveyor speed, liquid temperature, spray pressure and chemical concentration. Etching stops immediately once target blind depth or full throughetch is achieved to avoid overetching and fracture of tiny features. Different metal materials require dedicated etchant formulations.

Step 7: Stripping and Multistage Rinsing

Hot alkaline solution strips off all photoresist masking after etching. Multicycle circulating rinsing thoroughly washes residual corrosive chemicals trapped inside microholes and narrow gaps. Inadequate rinsing will lead to later oxidation, discoloration and corrosion on finished parts.

Step 8: PostTreatment

Posttreatment options include passivation, ultrasonic cleaning and precision drying. Medicalgrade and newenergygrade parts adopt highpurity deionisedwater cleaning. For titaniumseries alloys, optional degassing heat treatment can mitigate hydrogenembrittlement risk. Additional surface treatments such as anodising are available upon customer requirements.

Step 9: Quality Inspection & Batch Record Archiving

Critical dimensions, aperture tolerance, web width and flatness are verified by metrology equipment. Fullarea AOI scanning detects broken webs, pinholes and pattern distortion. Filtermesh products can carry out saltspray test or flowrate performance test. Qualified products are sorted and packaged. All batch process and inspection data are archived for complete traceability.

2. Common Metals Suitable for Etching of Metals

 Stainless steel (304, 316, 430): shims, gaskets, filter meshes  Copper, brass, phosphor bronze: EMI shielding parts, spring contacts, lead frames  Nickel and nickelbased alloys: hightemperature and corrosionresistant functional components  Titanium & titanium alloys: medical devices, hydrogenenergy filter elements  Special refractory metals: niobium, tantalum, kovar for highend scientific instruments

Each metal material has unique etching rate and tolerance performance, requiring matched etchant formula and process parameters.

3. Key Advantages of Etching of Metals

Burrfree and stressfree: No mechanical impact during processing, avoiding burrs, workhardening and residual internal stress, preserving original material properties.

No expensive hard tooling: Part shapes are defined by phototool film. Design modifications only need updated artwork, lowering prototype and smallbatch cost.

High capability for complex microfeatures: Onestep manufacturing for intricate contours, dense microhole arrays and fine mesh structures.

Excellent batch repeatability: Stable process parameters deliver consistent dimensional performance for mediumvolume production.

Wide thickness adaptability: Process ultrathin foils starting from 0.02 mm up to severalmillimetre thin metal sheets.

4. Process Limitations

Etching of metals is isotropic subtractive manufacturing with unavoidable lateral undercut. Minimum feature size is restricted by material thickness. Chemical consumption and professional wasteliquid treatment are required. For thick plates or simple highvolume blanks, stamping or laser cutting may bring better economic benefits.

5. Typical Industrial Applications

Etched metal components are widely used for precision shims, sealing gaskets, filter mesh sheets, encoder discs, spring contacts, lead frames, flowfield plates, medical functional sheets and automotive microcomponents across multiple industries. It supports prototype verification, smallbatch trialrun and mediumvolume mass manufacturing.

Conclusion

Etching of metals is a flexible cold subtractive manufacturing technology for thingauge metallic materials. By combining photoresist masking and controlled chemical dissolution, it produces highprecision complex metal parts without burrs and residual stress. Understanding isotropic undercut rules, DFM constraints and material characteristics is essential for achieving qualified etched metal components.