How does metal etching work?

Metal etching works by selectively removing material from the surface of a metal using chemical or physical processes. The specific method used may vary depending on the desired outcome and the type of metal being etched.
Chemical etching typically involves the following steps:
1. Cleaning: The metal surface is thoroughly cleaned to remove any contaminants such as dirt, oil, or oxidation, ensuring proper adhesion of the etching mask.
2. Masking: A protective mask, often made of acid-resistant material such as photoresist or vinyl, is applied to the metal surface. The mask is designed to expose only the areas that need to be etched while protecting the rest of the surface.
3. Exposure: The masked metal is exposed to an etchant, usually an acid or chemical solution. The etchant selectively reacts with and dissolves the exposed areas of the metal, leaving behind the desired design or pattern.
4. Rinsing and Finishing: After the desired etching depth is achieved, the metal is thoroughly rinsed to remove any remaining etchant. The protective mask is then removed, and the surface may undergo additional treatments like cleaning, polishing, or coating to enhance its appearance and durability.

Physical etching methods, such as laser or mechanical etching, involve the following steps:
1. Masking: Similar to chemical etching, a protective mask is applied to the metal surface, exposing only the areas that need to be etched.
2. Etching Process: In laser etching, a high-energy laser beam is directed at the masked metal, vaporizing or ablating the exposed areas. Mechanical etching methods, such as engraving or abrasive blasting, involve physically removing material through mechanical force or abrasive particles.
3. Finishing: Once the etching process is complete, the protective mask is removed, and the metal surface may be cleaned, polished, or treated to achieve the desired appearance and functionality.
In both chemical and physical etching, the precision and detail of the final result are determined by the accuracy of the masking technique and the control of the etching process. These factors play a crucial role in achieving the desired design or pattern on the metal surface.

Below FAQ are some common concerns of our clients before custom metal parts via photo etching.
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Chemical etching process: 10 frequently asked questions

The chemical etching process is a sheet metal machining process that is used to manufacture complex components with high levels of accuracy.Comprising nine steps, it works by printing the component design onto a photoresist mask which is laminated onto the metal. The areas of photoresist which have not been printed are developed, exposing the metal, which is subsequently etched away.

Almost any metal and metal alloy can undergo chemical etching. This includes steel and stainless steels, nickel, copper, aluminium. What makes photochemical etching so effective is that it works well on hard-to-machine metals, including highly corrosive-resistant metals such as titanium and its alloys.

Most metals are etched using ferric chloride, a safe to use, recyclable etchant. Ferric chloride can be regenerated and reused. Other proprietary etchants such as nitric acid, are used for specialist metals and alloys.

Sheet metals between 0.010mm and 1.5 mm thick can be etched. The thicker the sheet the longer it takes to etch, meaning metals above 1.5mm are uneconomical to process.

Excellent accuracy can be achieved with photochemical etching. Standard minimum etching tolerances are ±10% of the metal thickness being etched, to a minimum of ±0.025 mm. With development, greater accuracy can be achieved so it is encouraged that customers partner with TONGJIN Etching early in the design phase so an appropriate etching method can be developed.

Chemical etching is highly advantageous and offers many benefits. This process does not use mechanical force, unlike stamping which subjects sheet metals to extreme pressures. Nor does it put thermal stress on the cutting edge, unlike laser cutting. Alongside this, chemically etched parts remain flat, burr- and stress-free, leaving the material properties unaffected. Chemical etching can also produce very accurate engraved features at the same time the material is being profiled, such as fluidic channels, logos or part numbers. These features come at no additional cost.

The minimum standard etched opening achievable is 0.1 mm, but with development, etching can achieve even finer features.

Chemical etching uses digital tooling which is inexpensive, very easy to adapt and does not wear out, unlike presswork tooling. Material thickness and component size are key cost drivers as you pay by the sheet, not by the part – the more parts per sheet, the lower the unit price. Thicker sheets take longer to etch and this is reflected in the cost of the component.

There is no maximum quantity that chemical etching can produce. Low-cost digital tooling ensures prototype quantities can be supplied quickly and economically. As one of the largest sheet metal etching companies in the world, TONGJIN Etching supplies its customers with component quantities measured in the millions.

Chemical etching lead times are measured in days, not weeks or months, unlike traditional metal machining technologies. Subject to quantities required and capacity, standard components which require no additional post-processing can be supplied in less than two working weeks. Urgent demands can be supplied even quicker.

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