What Is the Etching Process Step by Step

Etching, more precisely photochemical etching (also called chemical etching or photochemical machining), is a subtractive metalmanufacturing process. It uses photosensitive resist masks and chemical etchants to selectively remove unwanted metal material without mechanical cutting, stamping, or laser thermal damage. The process produces burrfree, stressfree complex thingauge metal components widely used in automotive, medical, newenergy, electronics and semiconductor industries. Below is the full industrial etching process explained step by step.

Step 1: DFM Review and Design Preparation

The etching process starts long before physical processing. Engineers perform Design for Manufacturability (DFM) review based on customer CAD or DXF files. Etching is an isotropic process: etchant attacks metal both vertically and sideways, creating undercut. Technicians calculate undercut compensation according to metal thickness. Normally, the minimum feature size cannot be smaller than the material thickness for reliable throughetching. At this stage, technicians confirm material grade, sheet thickness, hole layout, tolerance requirements, whether parts require throughetching or halfetching, and decide on panel layout and tab positions for easy handling during mass production. After design confirmation, highprecision phototools (exposure films) are produced for subsequent UV exposure.

Step 2: Metal Sheet Surface PreTreatment & Cleaning

Surface cleaning is critical for stable etching quality. Oil, grease, fingerprints, oxidation layers and dust will cause photoresist delamination, pinholes and pattern defects. Metal sheets go through alkaline degreasing to remove grease, multistage water rinsing, acid deoxidation and drying. Highprecision components may adopt ultrasonic cleaning to achieve an ultraclean surface. Any contamination left on the metal will lead to scrap in later stages.

Step 3: Photoresist Lamination

Inside a yellowlight workshop environment, dryfilm photoresist is thermally laminated onto both sides of the cleaned metal sheet under controlled temperature and pressure. The dryfilm photoresist is UVsensitive and chemicalresistant. It acts as a protective mask that covers areas which must remain untouched by etchant. For reeltoreel mass production, continuous metal coils are automatically laminated instead of individual sheets.

Step 4: UV Exposure

The prepared phototool is tightly aligned against the photoresistcovered metal surface. Under UV light irradiation, the exposed sections of photoresist undergo polymerization and become chemically stable and acidresistant. Unexposed areas stay soluble and will be removed later in developing. For doublesided throughetching, topside and bottomside phototools must maintain precise alignment. Misalignment will result in distorted holes and profiles.

Step 5: Developing

Workpieces are transported through a developing machine filled with alkaline developer solution. Unexposed, unpolymerized photoresist dissolves and washes away, exposing bare metal regions that need to be etched. Polymerized photoresist remains firmly bonded onto metal surfaces as the protective mask. Operators perform visual inspection after developing to check for broken resist, pinholes, incomplete development or pattern offset. Defective panels are rejected before entering the etching chamber.

Step 6: Core Chemical Etching

This is the core step of the whole etching process. Panels are fed into a fullyautomatic constanttemperature spray etching cabinet. Pressured chemical etchant sprays evenly onto exposed bare metal surfaces. The etchant dissolves unprotected metal into soluble metal ions. Areas covered by polymerized photoresist stay intact. Processing time controls etching depth: full penetration for throughetched parts; shorter dwelltime for halfetching (blind etching for grooves, marking or bend lines). Because of isotropic behaviour, lateral undercut occurs simultaneously with vertical etching. This effect has already been compensated in the earlier DFM design phase to guarantee final dimensional accuracy. Key parameters including etchant temperature, concentration, spray pressure and conveyor speed are strictly controlled to keep consistent quality across batches.

Step 7: Photoresist Stripping & MultiStage Rinsing

Once target depth is achieved, parts exit the etching zone. Hot alkaline stripping solution removes all remaining polymerized photoresist mask. Multicountercurrent rinsing thoroughly washes residual etchant and chemical contaminants away. Poor rinsing will cause surface discoloration, spot corrosion and premature rust on finished metal parts.

Step 8: Optional Secondary PostProcessing

Etched panels can receive further finishing operations according to project requirements: passivation, polishing, electrolytic polishing, plating, coloring, bending, forming, tab removal and precision cleaning. Many massproduced parts stay connected to the main sheet via small retaining tabs through etching and handling. Tabs are removed in postprocessing to separate individual components.

Step 9: Quality Inspection

Multiple inspection items are carried out for finished panels:

· Optical measuring instruments verify critical dimensions, hole sizes and feature positions;

· Visual inspection detects pinholes, incomplete etching, overetching and surface defects;

· Flatness check for thin foil components. For medical, automotive or semiconductorgrade products, material certificates and inspection reports can be generated upon request. Qualified goods are cleaned and packed for shipment.

Key Notes for the Etching Process

1. Material thickness limits minimum hole and feature size due to isotropic undercut;

2. Industrial etching works best for 0.02 mm1.5 mm thingauge metal sheets;

3. Halfetch blind depth tolerance is wider than throughetching tolerance;

4. Automated spray equipment, stable temperature control and clean yellowlight environment are essential for massproduction consistency.

Typical Applications

The etching process produces encoder discs, microporous filter meshes, precision gaskets, automotive spring plates, medical nebulizer plates, battery electrodes, hydrogenenergy flowfield plates, shielding components and metal nameplates.

Conclusion

To recap what the etching process is step by step: DFM design and phototool preparation → metal cleaning → photoresist lamination → UV exposure → developing → spray chemical etching → stripping and rinsing → optional postprocessing → quality inspection and delivery. Every step influences final part quality. Photochemical etching is ideal for thingauge, complexgeometry metal parts requiring burrfree and stressfree performance.