Metal etching procedure refers to the complete industrial workflow of photochemical machining that transforms flat metal sheets into precision parts through controlled chemical subtraction. The whole procedure follows a fixed sequence, from drawing evaluation to finishedpart inspection. Every stage directly influences dimensional accuracy, edge quality, flatness and yield rate. Even minor deviation in any procedure may cause resist peeling, pattern distortion, overetching or broken fine features. This procedure applies to stainless steel, copper, nickel, titanium and other thingauge metallic foils and sheets for mesh, shims, gaskets, spring contacts and microcomponents.

Step 1: DFM Review & Phototool Preparation

The metal etching procedure starts with designformanufacturability analysis. Process engineers check customer CAD files, evaluating material thickness, minimum hole size, narrow web width, feature layout and panel nesting arrangement. Since wet etching is isotropic, lateral undercut will happen while metal dissolves vertically. Corresponding undercompensation is added into phototool artwork to offset side erosion. Features beyond practical process limits will be marked and fed back for drawing optimisation. Once confirmed, the compensated phototool film is produced for subsequent UV exposure. Without proper DFM adjustment, finished parts will suffer dimension deviation regardless of downstream processing.

Step 2: Substrate Surface PreTreatment

Clean metal surface is the foundation for stable photoresist bonding. Raw metal sheets go through multistage pretreatment procedure. First, alkaline degreasing removes rolling oil, grease, fingerprints and surface particles. Then rinsing washes away detergent residues. Mild chemical microetching creates uniform microroughness on metal surface to enhance dryfilm adhesion. After that, deionised water rinsing and hotair drying are performed. Surface contamination or uneven roughness will trigger dryfilm lifting, etchant penetration under mask and mass rejection. For reactive alloys such as titanium or niobiumtitanium alloys, pretreatment formula must be specially tuned to avoid excessive passivation.

Step 3: Dryfilm Photoresist Lamination

Acidresistant dryfilm photoresist is hotroll laminated onto both sides of cleaned metal substrate. Temperature, roller pressure and feeding speed are strictly controlled during this procedure. Operators must eliminate all trapped air bubbles and surface wrinkles. Bubbles allow corrosive etchant to seep underneath masking film and destroy fine patterns, especially for dense micromesh parts. Bothside lamination is standard for throughetched products. Singleside lamination can be adopted for blinddepth etching requirements. After lamination, panels stay for thermal stabilisation before entering exposure station.

Step 4: Precision UV Exposure

The compensated phototool is precisely aligned against dryfilmcovered metal sheet. Highintensity ultraviolet light transfers part pattern onto photoresist. The areas representing final components receive UV radiation, so photoresist cures and becomes resistant to chemical etchant. Unwanted openwindow regions remain uncured and keep soluble for developing. Doublesided alignment exposure is critical for throughetched meshes and perforated sheets to guarantee symmetric geometry on top and bottom surfaces. Misalignment will produce deformed holes and uneven webs.

Step 5: Developing & PreEtching AOI Inspection

Panels are conveyed through alkaline developer solution in this procedure. Unexposed, uncured photoresist dissolves completely, opening clean windows where metal will be removed. Cured protective masking remains firmly attached to metal surface. After developing, thorough water rinsing removes developer liquid residue. Automatic Optical Inspection (AOI) is implemented here to detect pinholes, incomplete development, resist residues and pattern shift. Defective panels are eliminated before etching to save material and chemical cost.

Step 6: Core Chemical Etching Procedure

This is the materialremoval core of whole metal etching procedure. Clamped panels pass through closedloop spray etching chamber. Custommatched etchant is continuously sprayed onto exposed metal windows. Metal dissolves selectively by chemical reaction. Key process variables including conveyor speed, etchant temperature, spray pressure and chemical concentration are monitored in realtime. According to product requirement, processing continues until target blind depth or full throughetch is achieved. Workpieces exit etching chamber immediately once dimensions hit specification to prevent overetching and finefeature fracture. Different metal materials require dedicated etchant formula: ferricchloride system for stainless steel; HFHNO₃ mixed acid for titaniumbased alloys.

Step 7: Photoresist Stripping & MultiStage Rinsing

After etching completes, panels enter stripping procedure. Hot alkaline solution strips off all cured photoresist protective mask from both metal surfaces. Multiple circulating water rinses follow immediately to wash away stripping agent and residual corrosive etchant trapped inside microholes and narrow gaps. Insufficient rinsing leaves chemical residues, which lead to laterstage oxidation, discoloration and corrosion on finished parts.

Step 8: PostTreatment

Posttreatment procedure varies depending on material and application scenarios. Common operations include passivation, chemical polishing, ultrasonic cleaning and vacuum drying. Medicalgrade, newenergygrade components adopt highpurity deionised water cleaning. For titaniumseries alloy parts, optional degassing heat treatment can reduce hydrogenembrittlement risk. Secondary surface finishing such as anodising can be added upon customer request.

Step 9: Quality Inspection & Batch Archiving

The final procedure is comprehensive quality verification. Metrology tools check critical dimension, aperture tolerance, web width and flatness. AOI fullscan detects broken webs, pinholes and pattern defects. Additional performance tests such as saltspray test, flowrate test can be carried out for filtermesh products. Qualified parts are separated, packed and delivered. All batchrelated process parameters and inspection records are archived for full traceability.

Influencing Factors for Metal Etching Procedure Quality

 Material grain status and surface condition of incoming metal blanks  Accuracy of DFM compensation and phototool artwork  Pretreatment effect and dryfilm lamination quality  Stability of etching temperature, pressure and chemical concentration  Rinsing thoroughness after etching and stripping

Advantages of Standardised Metal Etching Procedure

Following complete standard metal etching procedure delivers burrfree, stressfree precision metal parts. Tooling comes from phototool film instead of expensive hard dies, supporting fast prototype iteration and mediumbatch production. Complex microstructures such as dense meshes can be manufactured in one integrated set of procedures.

Limitations

The whole metal etching procedure consumes chemical liquids and requires wasteliquid treatment. Isotropic side undercut is inherent, so minimum feature size is restricted by material thickness. For thick metal plates or extremely highvolume simple blanks, stamping may provide better economic benefit.

Typical Applications

Parts manufactured by this metal etching procedure cover precision shims, sealing gaskets, filter mesh sheets, encoder discs, spring contacts, lead frames, flowfield plates, medical functional sheets and automotive microcomponents across electronics, new energy, medical, aerospace and chemical industries.

Conclusion

Metal etching procedure is a systematic multistage subtractive manufacturing chain. Every single step from DFM review to final inspection interconnects with each other. Strict execution of each procedure is essential to achieve stable dimension, clean edge and high yield for precision etched metal components.