Chemical etching, also known as photochemical machining (PCM), is a subtractive manufacturing technology that uses controlled chemical reagents to selectively remove material from thin metal sheets to create complex, highprecision parts. Unlike mechanical stamping, laser cutting or CNC milling, it does not apply mechanical force to workpieces. There is no burr, material deformation or thermal distortion after processing, making it ideal for producing intricate patterns, microholes, meshes, shims, lead frames and other thinwall metal components across electronics, semiconductor, aerospace, new energy and medical industries.

The core working principle of chemical etching relies on photoresist masking technology. A designed part pattern is transferred onto the surface of flat metal material. Areas covered by cured photoresist are protected from corrosive chemicals, while exposed bare metal areas react with etchant and dissolve gradually. By controlling etchant concentration, temperature, spray pressure and processing time, manufacturers can accurately control etching depth and dimensional tolerance to meet strict precision requirements. Almost all etchable metals can be processed via this method, including stainless steel, copper, brass, beryllium copper, nickel, invar, kovar, titanium and special alloy foils ranging from 0.01 mm to 1.5 mm thickness.

The complete chemical etching process follows standardized sequential steps, from raw material preparation to final finishedpart inspection.

First step: Raw material selection and pretreatment. Suitable flat metal sheets or foils are selected according to drawing specifications for thickness, alloy grade and surface finish. Surface pretreatment is critical for stable photoresist adhesion. Oil, grease, oxidation layers and fingerprints must be fully removed through alkaline degreasing, water rinsing and microetch cleaning. Contaminant residues will cause photoresist peeling, pattern breakage or uneven etching defects. Cleaned metal panels are dried completely without water spots before next operation.

Second step: Photoresist laminating. Dryfilm photoresist is hotrolled and laminated on both sides of cleaned metal substrate under controlled temperature and pressure. Uniform lamination ensures full contact between dry film and metal surface; bubbles or wrinkles in photoresist will lead to defective patterns. Doubleside lamination is widely adopted for throughetch components, while singleside lamination applies for partialdepth etching requirements.

Third step: Exposure with phototool. Highprecision glass or film phototool containing customer CAD drawing patterns is aligned tightly onto photoresistcovered metal panel. Ultraviolet light passes through transparent zones of phototool to polymerize and harden corresponding photoresist. Regions under black opaque areas remain unpolymerized and keep soluble in developer solution. Precise alignment between topside and bottomside phototool directly determines dimensional accuracy of final parts, especially for fine features and dualsided etching structures.

Fourth step: Developing. After UV exposure, panels go through developing chemical solution. Unexposed, nonhardened photoresist dissolves away, exposing bare metal areas intended for etching. UVcured photoresist stays firmly bonded on metal surface as protective mask. Continuous water rinsing removes residual developer chemistry. Operators visually inspect panels to verify pattern integrity; short developing time leaves unwanted photoresist residue, while overdevelopment attacks protective mask edges and ruins feature precision.

Fifth step: Chemical etching core processing. Masked panels are conveyed into etching machine chamber. Pressured heated etchant solution is sprayed onto both workpiece sides. Etchant reacts chemically with exposed bare metal, dissolving metal atoms continuously. Spray pressure, liquid temperature, etchant composition and conveyor speed are tightly monitored production parameters. Conveyor speed defines total etching dwell time, which governs etching depth. For throughetch parts, metal material is fully dissolved through sheet thickness to separate individual parts from original panel. For partialdepth etching, controlled dwell time achieves defined cavity depth without penetrating metal base. During this chemical etching process, photoresist mask remains intact and shields nonprocessing metal zones from corrosion.

Sixth step: Stripping photoresist mask. Once target etching depth is achieved, workpieces enter stripping tank. Alkaline stripping solution strips off all hardened photoresist protective film completely, revealing full etched metal patterns. Multiple circulating water washes eliminate residual stripping chemical to prevent postprocess corrosion on finished metal surfaces.

Seventh step: Posttreatment and surface finishing. Depending on customer requirements, multiple optional posttreatments are available. Common options include deburring, passivation, pickling, electroplating, polishing, antitarnish coating. These procedures improve surface corrosion resistance, visual appearance or prepare components for subsequent assembly and welding.