Chemical etching, also widely known as photochemical machining (PCM), is a mature precision subtractive manufacturing technology designed for producing intricate, burr-free, and stress-free metal components. Unlike stamping, laser cutting, or CNC machining, chemical etching relies on controlled chemical corrosion rather than physical force or thermal ablation, making it ideal for ultra-thin metal sheets, microstructures, and complex patterned parts that traditional methods struggle to fabricate. The entire chemical etching process follows a strict step-by-step workflow, from substrate pretreatment to final post-treatment inspection. Each sequential step determines the pattern accuracy, surface quality, dimensional tolerance, and batch consistency of finished metal parts. Understanding the standardized step-by-step chemical etching workflow is essential for optimizing production quality, stabilizing process parameters, and improving manufacturing efficiency in industrial precision metal processing. This article systematically elaborates on every core procedure of the chemical etching process, explains key operational points, analyzes technical principles, and summarizes industrial application values and process characteristics.

Step 1: Metal Substrate Surface Pretreatment. Pretreatment is the foundational and prerequisite step of the entire chemical etching process, directly affecting the adhesion of photoresist materials and the uniformity of subsequent chemical corrosion. Industrial metal substrates, including stainless steel, copper, aluminum, and alloy sheets, inevitably carry surface contaminants such as oil grease, dust, oxidation layers, and uneven passivation films during rolling, transportation, and storage. If these impurities are not completely removed, the photoresist will fail to bond tightly to the metal surface, resulting in pattern peeling, local missing etching, uneven corrosion, and blurred part contours. The standardized pretreatment workflow includes three core operations: alkaline degreasing, acid activation, and multi-stage pure water rinsing. Alkaline solution effectively removes organic oil stains and surface attachments; dilute acid activation thins dense oxide and passivation layers on the metal surface to improve surface hydrophilicity; continuous pure water cleaning eliminates residual chemical solutions to avoid cross-contamination. Only a clean, smooth, and hydrophilic metal surface can ensure uniform photoresist coverage and stable subsequent processing.

Step 2: Photoresist Coating and Drying. After qualified pretreatment and drying, the metal substrate enters the photoresist coating stage, which is the core preparation step for pattern masking. Industrial production adopts two mainstream photoresist materials: dry film photoresist and wet photoresist. Dry film lamination is suitable for mass production of conventional metal sheets with a thickness of 0.1mm to 3mm, featuring uniform coating thickness, stable bonding performance, and high production efficiency. Wet photoresist is mainly used for ultra-thin metal plates and ultra-fine micro-nano patterns, as it can fit tiny surface gaps and achieve higher pattern resolution. During coating, the photoresist is evenly covered on the single or double sides of the metal substrate according to processing requirements. After coating, low-temperature constant drying is carried out to volatilize excess solvent, solidify the photoresist, and enhance the bonding force between the photoresist and the metal substrate, laying a solid foundation for subsequent UV exposure and pattern transfer.

Step 3: UV Pattern Exposure. Exposure is the key step to transfer design patterns from photomasks to the metal substrate surface. After drying, the coated metal sheet is precisely aligned with a customized high-precision photomask, which carries the component’s preset hollow, hole, and special-shaped patterns. The aligned substrate is placed in a professional UV exposure machine for uniform ultraviolet irradiation. The light-transmitting areas of the photomask allow UV light to penetrate and trigger a photopolymerization reaction of the photoresist, forming a dense, acid-resistant, and corrosion-stable protective layer. In contrast, the photoresist in the light-shielding areas does not receive UV irradiation and remains in an unreacted, soluble state. Precise exposure time and light intensity control are critical at this stage. Excessive exposure will cause pattern expansion and edge blurring, while insufficient exposure will lead to incomplete photoresist curing and easy peeling, affecting the final etching precision.

Step 4: Pattern Development and Inspection. The development process is responsible for revealing the target processing pattern and separating the protective area from the etching area. After UV exposure, the substrate is placed in a constant-temperature sodium carbonate developing solution for uniform cleaning. The soluble unexposed photoresist is completely dissolved and washed away, while the cured photoresist remains firmly attached to the metal surface. After development, the preset processing pattern is accurately displayed on the metal substrate, with exposed metal areas to be etched and photoresist-protected areas to be retained. After development, strict manual and machine visual inspection is required to check for incomplete development, pattern deviation, edge serration, and residual photoresist impurities. Unqualified substrates will be reworked or eliminated to ensure zero defects before entering the formal etching process, which is an important quality control link to avoid batch defective products.

Step 5: Core Chemical Etching Processing. As the most critical forming step of the entire workflow, chemical etching determines the dimensional accuracy, contour definition, and surface quality of finished parts. The inspected qualified substrate is sent to an automatic spray etching machine for industrial etching. The mainstream industrial etching solution takes ferric chloride as the main corrosive agent, matched with customized additives, stabilizers, and lateral etching inhibitors. According to different metal materials such as stainless steel, copper, and aluminum, the solution concentration, temperature, and spraying parameters are adjusted adaptively. The automatic spraying system ensures uniform and synchronous impact of the etching solution on the double-sided metal surface, realizing consistent atomic-level material removal. The core controllable parameters include etching temperature, solution Baume degree, spraying pressure, and processing time. Standard industrial etching temperature is controlled at 45–52℃ to ensure stable reaction speed and uniform corrosion. Precise parameter control can effectively suppress excessive lateral undercutting and stabilize the dimensional tolerance of precision parts within ±0.01mm. The whole process belongs to cold chemical reaction, with no mechanical extrusion and thermal deformation, ensuring the structural integrity of ultra-thin and micro components.

Step 6: Stripping, Cleaning and Post-Treatment. After completing chemical etching, the workpiece enters the final post-treatment stage to remove residual substances and optimize surface performance. Firstly, alkaline stripping solution is used to completely remove the cured protective photoresist on the metal surface. Then neutralization cleaning is performed to eliminate residual acidic etching solution and chemical reaction residues, preventing secondary corrosion and oxidation of the metal substrate. For high-end precision components used in optics, medical devices, and precision electronics, fine polishing and secondary passivation treatment can be added to remove tiny etching traces and micro burrs, improving surface flatness and corrosion resistance. Finally, multi-stage high-purity water cleaning and constant-temperature hot air drying are carried out to ensure no chemical residue on the workpiece surface, meeting industrial assembly and long-term service standards.

Step 7: Final Quality Inspection and Finishing. The last step of the complete chemical etching process is dimensional detection and quality screening. Professional precision measuring instruments such as micrometers, projectors, and tolerance detectors are used to detect part thickness, hole diameter, pattern spacing, and overall dimensional tolerance. Meanwhile, surface inspection is conducted to check for pitting, uneven etching, edge defects, and surface scratches. Qualified products are sorted, packaged, and put into storage, while unqualified products are classified and reworked or scrapped. This final inspection step ensures the batch stability and qualified rate of etched parts, meeting the precision manufacturing requirements of automobiles, optics, electronics, and aerospace industries.

In summary, the step-by-step chemical etching process is a systematic, standardized, and controllable precision manufacturing system. Each sequential procedure from pretreatment, coating, exposure, development, etching, post-treatment to final inspection is closely linked and mutually restricted, jointly determining the final product quality. Compared with traditional mechanical processing, the standardized step-by-step chemical etching workflow has prominent advantages of no stress deformation, no burrs, high precision, and strong flexibility. It can efficiently manufacture complex micro-precision metal parts without expensive mold opening, greatly reducing customized production costs. With the continuous upgrading of high-end precision manufacturing requirements, the standardized chemical etching step-by-step process will be further optimized towards intelligence, high efficiency, and green environmental protection, providing reliable technical support for modern precision metal component manufacturing.