Precision metal components are core foundational parts for aerospace, electronic communication, food medical equipment, new energy and precision instrument industries, putting forward ultra-high requirements for dimensional tolerance, surface smoothness, structural uniformity and material mechanical stability. Chemical etching, also known as photochemical machining (PCM), is a non-contact, stress-free subtractive manufacturing technology for micro-precision metal parts, which breaks through the processing bottlenecks of traditional stamping, laser cutting and CNC milling for ultra-thin, micro-hole and complex pattern metal components. This paper systematically expounds the reaction mechanism, applicable metal substrate classification, standardized industrial processing flow, core process parameter control, technical advantages, common processing defects, defect optimization schemes and industrial application scenarios of precision metal component chemical etching. It compares chemical etching with mainstream precision metal machining technologies, analyzes the adaptability of etching process for ultra-thin alloy, micro-mesh, micro-slot and irregular profile metal parts, and summarizes green manufacturing upgrading direction and future industry development trends. The research verifies that optimized photochemical etching can realize ±1μm dimensional precision of metal components, no burr, no thermal deformation and no internal residual stress, which perfectly meets the batch production demand of high-end precision metal components, and has irreplaceable industrial application value compared with traditional mechanical processing.

1. Introduction

With the iterative upgrading of high-end intelligent manufacturing and micro-electronic technology, modern equipment is developing towards miniaturization, lightweight and high integration, which drives the market demand for precision metal components with micron-level precision, ultra-thin substrate and complex planar structure to surge sharply. Precision metal components cover metal micro-meshes, sensor metal substrates, aerospace gaskets, medical metal accessories, battery current collectors and electronic shielding sheets, most of which adopt thin stainless steel, copper alloy, aluminum alloy, nickel alloy and titanium alloy as raw materials. Traditional precision machining methods have obvious inherent defects in processing such components: CNC milling is prone to tool wear and edge collapse for micro-size parts; mechanical stamping will produce extrusion deformation, work hardening and residual stress on parts; laser cutting forms heat-affected zones, oxidation burn marks and micro-cracks on cutting edges, destroying the fatigue resistance and corrosion resistance of precision parts.

As a mature cold chemical processing technology, precision metal chemical etching relies on photolithography masking technology and controllable redox corrosion reaction to selectively remove redundant metal materials without changing the original metal mechanical properties. It is especially suitable for batch manufacturing of 0.02mm-2mm ultra-thin metal sheets, dense micro-hole arrays, asymmetric special-shaped patterns and ultra-flat precision parts. At present, chemical etching has become the preferred process for high-precision metal components in medical implantation equipment, 5G communication electronic parts and new energy battery components. Combined with industrial production pain points of high precision, low defect rate and food/medical safety standards, this paper conducts an in-depth discussion on the whole process system of precision metal component chemical etching, and provides technical reference for process optimization and green production of precision metal manufacturing enterprises.

2. Fundamental Reaction Mechanism of Precision Metal Chemical Etching

The core principle of precision metal component chemical etching is selective anisotropic/isotropic chemical corrosion, which combines photoresist lithography pattern masking and acidic etching solution redox reaction to complete precise material removal. Most alloy metal surfaces form dense natural passivation oxide films in atmospheric environment, which can isolate chemical corrosive media; the etching process uses patterned polymer photoresist to cover the reserved finished area of metal components, and exposes the area that needs to be removed to the etching solution.

Industrial mainstream etching solutions are divided into two categories according to metal materials: ferric chloride mixed acidic solution for stainless steel, nickel alloy and copper alloy; special buffered hydrofluoric acid mixed solution for aluminum alloy and titanium alloy high-precision components. Chloride ions and hydrogen ions in the etching solution first break the surface passivation film of exposed metal substrates, then oxidize metal elemental substances into soluble metal cations through oxidizing components in the solution, and the dissolved metal ions diffuse into the circulating etching solution to complete material stripping. For conventional precision stainless steel and copper components, the process adopts isotropic etching, with consistent vertical depth corrosion and horizontal side wall corrosion, forming smooth and vertical part edges; for aerospace titanium alloy precision parts, anisotropic controlled etching is adopted to reduce lateral undercut and improve dimensional precision.

Different from thermal processing and mechanical processing, the whole chemical etching process is carried out at low temperature below 60℃, no mechanical force impact and no thermal radiation, so the metal matrix will not produce phase change, internal residual stress, metal work hardening and edge burrs. This core mechanism advantage ensures that precision metal components maintain original tensile strength, toughness and corrosion resistance after processing, which is the key reason why etched parts are applicable to high-end precision equipment with strict performance requirements.

3. Standard Production Process for Precision Metal Etched Components

Industrial batch production of chemically etched precision metal components adopts unified 9-step standardized process, which is optimized for micron-level dimensional precision and surface cleanliness, adapting to electronic, medical and aerospace grade product standards.

First, raw material cutting and surface pretreatment. Cut coiled precision alloy metal sheets into fixed-size blanks, remove surface machining oil, dust, rust and heterogeneous oxide film through alkaline electrolytic degreasing and weak acid pickling, improve the bonding force between metal surface and photoresist, and avoid uneven etching and pattern deviation caused by surface impurities. Second, double-sided dry film photoresist lamination. Use high-resolution alkali-resistant and acid-resistant polymer dry film photoresist for hot pressing lamination on metal surface, select different photoresist thickness according to component pore size and pattern precision to improve pattern reduction rate.

Third, CAD pattern layout and UV exposure. Import precision component digital drawing for typesetting and plate making, realize double-sided alignment UV exposure; the exposed photoresist undergoes cross-linking polymerization to form anti-corrosion mask layer, which fits the final contour of precision parts completely. Fourth, alkaline developing treatment. Spray sodium carbonate developing solution to wash away unexposed photoresist, expose the metal area to be etched, and realize 1:1 reduction of micron-level pattern design. Fifth, circulating spray chemical etching. Adopt closed constant-temperature spray etching equipment instead of static immersion etching, control spray flow rate and liquid pressure to ensure uniform corrosion of the whole board, stabilize component dimensional tolerance.

Sixth, photoresist stripping. Use alkaline stripping agent to completely remove surface cured photoresist without damaging polished metal base surface. Seventh, multi-stage neutralization and ultra-pure water cleaning. Neutralize residual acidic etching liquid on component surface to prevent post-processing oxidation and rusting, remove trace chemical residues to meet medical and electronic grade cleanliness standards. Eighth, surface passivation and polishing. Carry out electrochemical passivation to repair metal passivation film, improve component oxidation resistance and service life; fine polishing for ultra-high precision electronic parts. Ninth, die cutting and full inspection. Cut integrated board into single finished precision components, conduct full inspection on dimensional tolerance, hole blockage, surface scratch and chemical residue via optical microscope and elemental detection equipment.

4. Material Adaptation and Key Process Parameter Control

4.1 Common Precision Metal Substrate Classification

304/316L stainless steel: the most widely used material, for food, medical and electronic precision components, strong corrosion resistance, low etching difficulty; oxygen-free copper alloy: for communication shielding parts and battery conductive components, fast etching speed, high surface flatness; 5052 aluminum alloy: lightweight aerospace precision gaskets, need special anti-corrosion additive etching solution; titanium alloy and nickel-titanium alloy: medical implant precision parts, high chemical stability, low etching rate, high process difficulty.

4.2 Core Optimized Process Parameters

Etching solution concentration, constant temperature and spray pressure determine component precision and yield. For conventional stainless steel precision components, 42-46°Bé ferric chloride etching solution, processing temperature 45-53℃, spray pressure 0.25-0.32MPa are the optimal parameters; excessive temperature will cause lateral undercut and dimensional out-of-tolerance, too low temperature leads to incomplete penetration and low production efficiency. For micro-hole precision components with aperture less than 50μm, slow-speed circulating etching and filter residue treatment are required to avoid micropore blockage; the overall dimensional tolerance of mass-produced parts can be controlled within ±1μm after parameter optimization.

5. Process Advantages, Defects and Optimization Strategies

5.1 Unique Technical Advantages

First, ultra-high pattern precision and zero-stress forming. Realize micron-level micro-hole, micro-slot and complex special-shaped contour processing, no internal stress, no part warping after long-term use. Second, no damage to metal matrix. Burr-free, crack-free and heat-free processing, retain original metal physical and chemical properties. Third, low batch customization cost. Digital photolithography mold realizes fast pattern switching, no die cost compared with stamping process, suitable for multi-variety small-batch precision parts production. Fourth, uniform batch consistency. Uniform etching reaction ensures identical size and surface quality of thousands of components, improving assembly matching rate.

5.2 Existing Defects and Optimization Schemes

The main limitations include limited processing thickness of metal substrates, poor processing efficiency for thick plates; traditional etching wastewater contains heavy metal ions and chloride pollutants, high sewage treatment cost; excessive lateral undercut restricts ultra-small micro-component production. Corresponding optimization measures: add organic corrosion inhibitors to reduce lateral corrosion; adopt membrane filtration regeneration technology to recycle etching solution, reduce wastewater discharge; combine micro-polishing post-process to improve surface finish of precision parts.

6. Industrial Application and Future Development Trend

At present, chemically etched precision metal components cover three major high-end industries: medical device industry including surgical metal gaskets and micro-filter parts; new energy industry including lithium battery pole piece and fuel cell metal substrates; 5G electronic communication industry including electromagnetic shielding sheets and micro-channel heat dissipation components. Compared with other processes, etched precision parts have longer service life and higher assembly yield rate, which reduce the overall manufacturing cost of terminal equipment.

In the future, precision metal chemical etching will develop in three directions: nano-level ultra-precision composite etching technology, green low-carbon closed-loop etching production line, and one-step integrated etching and surface functional modification technology. With the expansion of high-end precision manufacturing market, photochemical etching will become the mainstream processing technology for thin-wall and micro-structure precision metal components, replacing part of laser and mechanical processing market.

7. Conclusion

Chemical etching is a high-efficiency, high-precision and low-defect manufacturing technology for precision metal components, which solves the processing pain points of thin-plate, micro-structure and complex-profile metal parts in traditional machining. Relying on photolithography masking and controllable chemical redox reaction, this technology realizes stress-free, burr-free and thermal-damage-free forming of precision metal parts, with stable dimensional tolerance and excellent batch consistency. Reasonable matching of metal substrate, etching solution formula and process parameters can greatly improve product yield and component comprehensive performance. Although the technology has limitations in thick metal plate processing and wastewater treatment, green etching regeneration and parameter optimization technology effectively make up for technical shortcomings. Driven by high-end equipment manufacturing demand, chemical etching of precision metal components will achieve further technical iteration, and occupy a core position in the field of micro-precision metal manufacturing in the long run.