Etching Process Steps

Photochemical etching (also called chemical etching) is a precision subtractive manufacturing technology for thin metal sheets. It uses photoresist masking and chemical dissolution to create burrfree, stressfree precision metal parts such as microhole meshes, encoder discs, gaskets, spring contacts and shielding components. Every etching process step directly impacts dimensional accuracy, edge quality, hole roundness and production yield. Strictly following each procedural stage enables consistent output from prototype sampling to highvolume mass production. Below breaks down the complete industrial etching process steps in detail.

Step 1: DFM Review & Artwork Preparation

The etching workflow starts before any physical material processing. Engineers perform DesignforManufacturing analysis based on customer CAD files. Key checking items include minimum feature width, holetothickness ratio, feature spacing, required etching depth and openarea ratio. Since wet chemical etching is isotropic, metal dissolves both vertically and laterally. Lateral undercut must be calculated and compensated into the production artwork. If drawings exceed technical boundaries such as overly small holes or extremely narrow gaps, engineers will provide optimized suggestions to avoid scrap. After DFM confirmation, productionready phototooling film is generated for the following exposure procedure.

Step 2: Raw Material Preparation and Surface PreTreatment

Qualified metal sheets or coils are selected according to project requirements. Common materials include stainless steel, copper, nickel, titanium, phosphor bronze and kovar alloy. Material thickness typically ranges from 0.02 mm to 1.5 mm. Surface pretreatment is one of the most critical etching process steps, which determines photoresist bonding performance.

Alkaline degreasing: Remove rolling oil, grease and organic contaminants. Oil residue will cause photoresist delamination, pattern peeling or missing features.

Acid pickling & activation: Remove oxide scale, tarnish and passive film.

Multistage rinsing and hot air drying. A uniformly microrough, clean surface is obtained for reliable dryfilm attachment. Poor pretreatment accounts for a large proportion of etching production defects.

Step 3: Photoresist DryFilm Lamination

Dryfilm photoresist is hotroll laminated onto the cleaned metal substrate. For throughetched parts with throughholes, doublesided lamination is adopted. Laminating temperature, pressure and speed are precisely controlled. Bubbles, wrinkles or incomplete bonding must be avoided. Trapped bubbles allow etchant to seep underneath resist, resulting in random spot defects on finished components. After lamination, panels rest for proper thermal stabilization before exposure.

Step 4: UV Exposure

The phototooling film is accurately aligned above the dryfilmcovered metal sheet inside UV exposure equipment. Highintensity ultraviolet light cures and hardens the photoresist in the regions that need to be protected from etching. Areas corresponding to slots, holes and outer contours remain unexposed and keep soluble properties. Precise alignment guarantees featureposition accuracy across the whole panel. Doublesided exposure is widely used for microhole products to improve holewall verticality and circularity.

Step 5: Developing

Exposed metal panels are conveyed through alkaline developer solution. The unexposed photoresist dissolves completely, opening clear windows that exactly match the areas intended for chemical etching. The UVcured photoresist remains intact as a protective mask. Intermediate inspection is essential at this stage. Operators use visual inspection or AOI automatic optical inspection to check for broken traces, residual photoresist and incomplete opening of microholes. Semifinished panels with pattern defects are eliminated before entering the etching bath.

Step 6: Core Chemical Etching

This is the central materialremoval step in the whole etching process. Masked workpieces travel through an automatic circulating spray etching line. Recirculating etchant is sprayed onto workpiece surfaces under controlled pressure. Through redox and complexation chemical reactions, etchant selectively dissolves unmasked exposed metal. Critical parameters including etchant temperature, spray pressure, conveyor speed and chemical concentration are digitally monitored and dynamically adjusted. Vertical etching depth and lateral undercut are balanced to meet drawing tolerance requirements. For fullpenetration parts, doublesided spraying delivers cleaner edges and better dimensional consistency. Etching time directly decides final depth or throughpenetration status.

Step 7: Photoresist Stripping

Once target etching depth or full penetration is achieved, parts move to the stripping tank. Hot alkaline stripping solution removes all cured photoresist mask from metal surfaces. Complete stripping must be ensured. Any remaining photoresist residue will interfere with subsequent postprocesses such as plating, passivation or electropolishing and cause surface blemishes.

Step 8: PostTreatment

After stripping, components go through multilevel rinsing and neutralization to wash away residual corrosive chemicals. Multiple optional secondary processes can be implemented based on customer specifications: passivation, electropolishing, nickel / gold plating, bending, forming, laser marking and sheet separation. Posttreatment improves corrosion resistance, surface smoothness, electrical conductivity or adapts parts for final assembly conditions.

Step 9: Comprehensive Quality Inspection

Quality inspection is the final etching process step before shipment. Finished parts undergo multidimensional verification:

Dimensional measurement via microscope or video measuring machine to verify hole size, line width and overall contour tolerance.

AOI optical scanning for microdefects such as nick, burr, missing hole and pattern distortion.

Flatness and surface appearance screening. Batch inspection reports can be supplied for customer incoming quality control requirements.

Key Notes Across All Etching Process Steps

Every step is interconnected. A minor defect in earlystage procedures will amplify in later stages and cause final part failure. DFM preevaluation, stable surface treatment, accurate pattern transfer and closedloop etchingparameter control together determine massproduction stability.

Common Products Made by Following These Etching Process Steps

The above etching process steps are applied to produce microperforated meshes, encoder discs, metal gaskets, automotive horn grilles, medical nebulizer plates, semiconductor shielding components, spring contacts and various precision thinmetal parts for electronics, medical, newenergy, automotive and instrumentation industries.

Conclusion

The standard industrial etching process steps include DFM artwork preparation, material & surface pretreatment, dryfilm lamination, UV exposure, developing, chemical etching, photoresist stripping, posttreatment and quality inspection. Different from stamping and laser cutting, photochemical etching relies on precise pattern transfer and controlled chemical dissolution, delivering burrfree lowstress thinmetal components. Understanding these etching process steps helps mechanical designers evaluate manufacturability and optimize drawings for better cost and yield performance.