Etching Process in Sheet Metal

Etching process in sheet metal, commonly referred to as sheetmetal photochemical etching or photochemical machining (PCM), is a subtractive manufacturing method that creates intricate 2D and partial 2.5D features on thin metal sheets through controlled chemical corrosion. Instead of shearing, stamping, bending or thermal cutting, this technology uses photolithography to define protective masks and dissolves unmasked metal areas with chemical etchants. It is widely adopted for sheet metal ranging from 0.02 mm to 2.0 mm, solving many manufacturing pain points that traditional sheetmetal processes struggle with.

Conventional sheetmetal fabrication such as stamping, laser cutting and wire EDM often brings burrs, mechanical stress, material deformation or heataffected zones, especially for ultrathin sheets, dense microholes, fine slots and complex geometries. Etching process in sheet metal avoids these drawbacks. It can produce largeformat sheetmetal panels full of microfeatures while maintaining original material physical properties, suitable for prototyping, smallbatch trial runs and highvolume mass production across electronics, automotive, medical, newenergy and instrumentation industries.

1. Suitable Sheet Metal Materials for Etching

A broad range of sheetmetal alloys can be processed by etching, yet each material requires customised pretreatment, etchant formulation and process parameters to achieve stable dimension and surface quality.

Stainless steel sheet (301, 304, 316L): The most common sheetmetal material for etching. Surface activation is required to break the chromiumrich passive film. Widely used for filter meshes, gaskets, spring plates and decorative sheetmetal parts.

Copper sheet & brass sheet: Good etching performance, mainly used for EMI shielding sheets, conductive shims and decorative sheetmetal components. Antioxidation handling is essential in postprocessing.

Phosphor bronze sheet: Preferred for elastic sheetmetal spring contacts and conductive shims. Etch rate must be precisely controlled to retain elasticity.

Nickel sheet & nickelalloy sheet: Applied for batteryrelated sheetmetal electrodes and hightemperature resistant functional sheets. Special etchant prevents uneven corrosion.

Titanium sheet: Used for hydrogenenergy bipolar plates and medical sheetmetal parts. Highly stable passive surface film demands specialised etching chemistry.

Kovar / Invar sheet: For semiconductor packaging sheetmetal components; strict process control reduces dimensional variation.

Too thick sheets or sheet metal with heavy nonmetallic inclusions are not ideal for etching process in sheet metal. Most commercial production focuses on sheet thickness between 0.02 mm and 2.0 mm.

2. Full StepbyStep Etching Workflow for Sheet Metal

Step 1: DFM Review & Phototool Preparation

Process engineers review customer CAD drawings for sheetmetal parts. Critical factors including minimum feature width, holetosheetthickness ratio, feature spacing, throughetch or halfetch depth are analysed. Since sheetmetal etching is isotropic, lateral undercut compensation is calculated and added into phototool files. Unreasonable design points are fed back for revision to reduce scrap risk.

Step 2: SheetMetal Surface PreTreatment

Raw sheetmetal panels go through alkaline degreasing to remove rolling oil, grease and surface contaminants. Acid activation removes oxide layers and passive films. Multiplestage deionisedwater rinsing followed by hotair drying delivers a clean, uniformly microrough surface. Good surface condition is the foundation for reliable photoresist adhesion. Poor pretreatment leads to resist lifting, pattern peeling and spotetching defects on sheetmetal surfaces.

Step 3: DryFilm Photoresist Lamination

Sensitive dryfilm photoresist is hotroll laminated onto sheetmetal surfaces. Doublesided lamination is required for throughetched sheetmetal parts. Lamination temperature, roller pressure and feeding speed are tightly controlled to eliminate bubbles and wrinkles. Trapped air causes etchant penetration under resist and creates defective patterns. Laminated sheets rest for thermal stabilisation.

Step 4: UV Exposure

Compensated phototool films are precisely aligned against resistcovered sheetmetal panels. Highintensity UV light cures photoresist in transparent graphic zones to form chemicalresistant protective masks. Photoresist under opaque areas remains soluble. Doublesided exposure is used for highprecision throughetched sheetmetal workpieces to guarantee frontback pattern alignment.

Step 5: Developing

Panels pass through dilute alkaline developer solution. Unexposed photoresist dissolves completely and opens clear etching windows on sheetmetal substrates, while UVcured masking resist stays attached. Automatic optical inspection screens semifinished sheets for broken traces, residual resist and blocked microholes.

Step 6: Spray Etching (Core Material Removal)

Sheetmetal panels travel horizontally through conveyortype spray etching chambers. Pressured circulating etchant is sprayed onto one or both sides of sheets according to product requirements. Etchant chemistry matches the sheetmetal alloy. Conveyor speed, liquid temperature, spray pressure and dissolvedmetalion concentration are strictly monitored. Etching continues until full penetration or target halfetch depth is achieved. Isotropic corrosion happens both vertically and laterally, so precalculated undercut compensation is mandatory.

Step 7: Photoresist Stripping

After etching completion, sheetmetal panels enter hotalkali stripping tanks to remove all cured photoresist masks. Complete stripping prevents resistrelated staining. Workpieces receive thorough rinsing afterwards.

Step 8: PostTreatment

Neutralisation eliminates residual corrosive chemicals. Stainlesssteel sheetmetal parts normally go through passivation to restore corrosion resistance. Secondary optional processes include electropolishing, plating, colour filling, laser marking and paneltosinglepart separation.

Step 9: Quality Inspection

Video measuring systems check dimensional accuracy of holes, slots, contours and flatness of sheetmetal parts. AOI scanning detects pinholes, nicks and pattern distortion. Visual appearance inspection and batchrecord archiving finish the whole workflow.

3. Core Advantages of Etching Process in Sheet Metal

Burrfree & stressfree sheetmetal output: No mechanical stamping or cutting force. Ultrathin and elastic sheetmetal components keep original material properties without deformation.

No hardtooling investment: Pattern modification only needs updated phototool film. Fast iterations support quick sheetmetal prototyping and flexible product upgrades.

Superior for dense microfeatures: Thousands of microholes, fine slots and complex outlines can be created on sheetmetal panels within one etching cycle; manufacturing difficulty does not rise with feature quantity.

Supports throughetching and halfetching: Halfetching achieves controlleddepth textures, marking and structural weakening on sheetmetal surfaces.

Excellent batch repeatability: Automated sprayetching lines deliver stable dimensional consistency for largevolume sheetmetal orders.

4. Process Limitations

Etching process in sheet metal suffers from inherent isotropic undercut. Minimum feature size is restricted by sheet thickness. It is economically viable mainly for thingauge sheets; cost rises significantly for thick sheet metal. Different sheetmetal alloys require dedicated etchant and pretreatment parameters.

5. Typical SheetMetal Etching Applications

Etched sheetmetal products include filter mesh panels, precision gaskets, encoder discs, optical apertures, EMI shielding sheets, spring contact sheets, automotive grille sheets, medical functional sheetmetal components, newenergy sheetmetal electrodes and decorative metal nameplates. It covers prototype verification, smallbatch trials and massvolume manufacturing.

Conclusion

Etching process in sheet metal is a mature subtractive manufacturing solution for thingauge sheetmetal production. With DFM optimisation, standard pretreatment, photolithographic masking and controlled isotropic chemical dissolution, it delivers highquality, burrfree complex sheetmetal parts. Understanding material limits and isotropicetching rules helps engineers optimise sheetmetal drawings and maximise process value.