Chemical Etching Process StepbyStep

Chemical etching, also widely known as photochemical machining or photo etching, is a subtractive precision manufacturing technology that selectively removes unwanted metal material by controlled chemical reaction instead of mechanical cutting, stamping or laser ablation. Without physical contact, high pressure or thermal impact on workpieces, this process produces burrfree, stressfree intricate metal components with micronlevel dimensional accuracy, which are extensively adopted in electronics, semiconductor packaging, newenergy equipment, medical instruments, aerospace and automotive industries. Shenzhen Zhuolida, as an experienced manufacturer specialized in precision chemical etching, has optimized every production procedure to stabilize tolerance within ±0.01 mm for massproduction sheets ranging from 0.01 mm to 2.0 mm thickness. This article breaks down the complete chemical etching workflow stepbystep, explaining core principles, critical control points and practical production considerations.

Step 1: Material Selection & Rigorous Surface Precleaning

The whole chemical etching workflow begins with material confirmation and surface preparation, and poor cleaning is the top cause for defective etching parts in mass production. Engineers first verify raw metal sheet specifications including alloy grade, material temper, sheet thickness, grain orientation and panel dimension. Usable metals cover stainless steel, copper, brass, nickel alloys, kovar 4J42, aluminium, titanium and special hightemperature alloys. Even ultrathin soft metal foils that cannot withstand stamping deformation are suitable for chemical etching processing.

Subsequently, multistage chemical degreasing and ultrasonic cleaning remove rolling oil, fingerprint residues, dust particles and surface oxide layers thoroughly. Mixed alkaline detergent and deionized water sequentially wash metal panels, followed by full rinsing and hotair drying. Zero residual contamination is mandatory, otherwise photoresist will lose adhesion locally, generating resist lifting, underetching or pattern distortion in later stages. Cleaned metal sheets are transferred into dustcontrolled cleanroom environment for next processing.

Step 2: Photoresist Lamination

Lamination is to cover both sides of cleaned metal substrate with UVsensitive dryfilm photoresist under constant temperature and pressure conditions. Most industrial chemical etching factories adopt dryfilm laminating equipment rather than liquid photoresist spraying, for better coating uniformity and repeatability in batch orders. Rolled dryfilm photoresist is thermocompressed onto metal surface, eliminating internal bubbles between resist film and metal base. The resist thickness is selected according to target etching depth, commonly ranging from 15 μm to 35 μm.

Adhesion quality decides pattern fidelity. Any tiny bubble, scratch or foreign particle trapped underneath photoresist will become defect sources. Shenzhen Zhuolida implements realtime visual inspection after lamination, rejecting panels with bad lamination before moving forward. After laminating, sheets go through short tempering dwell time to stabilize photoresist polymer status before UV exposure.

Step 3: UV Pattern Exposure (Image Transfer)

Digital CAD drawings are converted into highprecision glass phototools containing negative patterns of target components. The laminated metal sheet is positioned between two aligned phototools inside doublesided UV exposure machine, achieving accurate toptobottom pattern registration critical for throughholes and symmetric profiles. Highintensity 365 nm UV light passes through transparent areas of phototool, triggering crosslinking polymerization and hardening corresponding photoresist zones. Regions covered by opaque graphic parts of phototool remain unpolymerized and keep soluble.

Alignment accuracy is extremely vital for finefeature parts such as semiconductor mask sheets and micro filter screens. Misalignment will create asymmetric side profiles or misplaced openings. Advanced exposure equipment supports positioning precision lower than ±5 μm, which enables manufacturing ultrafine slots and dense microhole arrays. Exposure energy must be strictly calibrated; insufficient energy leads to incomplete resist curing, while overexposure brings pattern swelling and blurred graphic edges.

Step 4: Developing

After UV exposure, sheets enter spray developer chamber. Warm dilute alkaline developer solution (sodium carbonate solution) is sprayed across both surfaces to wash away unexposed, nonpolymerized photoresist completely. Only UVhardened photoresist stays firmly bonded onto metal surface as protective mask. Bare metal areas that need chemical dissolution are fully exposed.

Process parameters including developer concentration, liquid temperature, spray pressure and conveying speed require precise closedloop control. Underdevelopment leaves residual photoresist film blocking etching channels; overdevelopment erodes hardened resist edge and worsens feature resolution. Operators carry out sample checks frequently to confirm clean, sharp graphic edges without resist residue before entering etching station.

Step 5: Core Chemical Etching

Etching station is the heart of whole workflow. Panels are horizontally conveyed through enclosed etching tunnel, where heated ferricchloride or cupricchloride etchant is highpressure sprayed from top and bottom nozzles simultaneously onto exposed bare metal surface. Chemical etchant reacts with unprotected metal, dissolving material vertically and slightly laterally. Vertical etching depth defines final part thickness, while lateral material removal is known as undercut. Design engineers precompensate undercut value on original phototool artwork to counteract side erosion and guarantee finished dimension compliance.

Multiple key variables jointly govern etching quality: etchant concentration, working temperature, nozzle spray pressure and sheet transportation speed. Realtime sensor systems continuously monitor solution status, automatically replenish etchant chemicals and stabilize temperature around 4555 °C. Doublesided synchronized spraying ensures uniform etch depth over entire largesize sheet, avoiding uneven depth between sheet centre and edges. Depending on metal type and target depth, etching cycle time varies from several minutes to over twenty minutes. Halfetching for partialdepth channels and fullthrough etching for complete component separation can both be realized within the same production line.

Step 6: Photoresist Stripping & MultiStage Rinsing

Once target etching depth is achieved, sheets exit etching tunnel and receive full cascade deionized water rinsing to flush off corrosive etchant liquid quickly and prevent overetching from residual chemical liquid. Then panels go through caustic stripping bath, where alkaline stripper dissolves and peels off all remaining hardened photoresist protective mask from metal surface. After stripping, another series of thorough rinses remove stripping chemical residues entirely. Finally filtered hot air knives dry workpieces, delivering bare etched metal parts without polymer coverage. Residual chemical left on metal surface will cause later corrosion spots and compromise surface quality, so complete rinsing cannot be skipped for highend applications like medical and semiconductor components.

Step 7: Inspection, Sorting and PostTreatment

Finished parts enter comprehensive qualitycontrol phase. Automatic optical inspection equipment scans every panel, checking dimensional tolerance, holeposition accuracy, edge quality and surface defects. Manual sampling verification supplements automatic detection, measuring critical feature sizes with highprecision microscope and micrometre gauge. Unqualified products are screened out.

According to customer requirements, optional posttreatments include deburring, polishing, electroplating, passivation and tape laminating. Parts are separated from base sheet frame, counted and packed. Shenzhen Zhuolida implements fullprocess traceability, recording parameter logs of each batch to maintain stable repeatability for prototype development and largevolume serial production.

Core Advantages of Chemical Etching Technology

Compared with stamping, laser cutting and CNC milling, chemical etching delivers distinct strengths. Firstly, zero mechanical stress and burrfree edges preserve original metal material mechanical properties, no heataffected zones appear on workpiece surface. Secondly, complicated 2D geometry, dense microholes, ultranarrow slots and halfetched structures can be manufactured without expensive hard stamping dies; revision only needs phototool adjustment, cutting prototype iteration cost and shortening lead time greatly. Thirdly, processing difficulty and manufacturing cost are independent of graphic complexity, ideal for highdensity microcomponents.

Nevertheless, chemical etching also has limitations. It mainly suits thin sheet metal below 2.5 mm thickness; thicker material will generate excessive undercut and degrade finefeature precision. Design teams need to follow photochemicalmachining DFM guidelines to optimize drawing before production.

Industrial Applications

Reliable chemical etching output serves diverse hightech sectors. Semiconductor industry uses etched metal mask, flux mask and ball mask for chip packaging process. Newenergy field adopts etched metal flowfield plates for hydrogenfuelcell stacks. Medical devices utilize precision etched surgical components and microfilter meshes. Consumer electronics apply etched shielding sheets, spring contacts and decorative metal parts. Aerospace and sensor sectors also widely rely on this mature subtractive manufacturing solution.

To sum up, successful chemical etching depends on strict execution of every sequential step: material precleaning, photoresist lamination, UV exposure, developing, controlled chemical etching, stripping and multilevel inspection. Each single step influences final dimensional accuracy, surface finish and batch consistency. As a professional chemical etching manufacturer, Shenzhen Zhuolida optimizes equipment, chemical formula and operation standards, helping global customers turn complex CAD designs into qualified highprecision metal parts from prototype to mass production.