Etching processing methods mainly include the following types:

Chemical - etching

1. **Principle**
- It uses a chemical solution to react with the surface of the metal or non - metal material. The chemical solution selectively dissolves the material at different rates according to the composition and structure of the material, so as to achieve the purpose of material removal and shape processing. For example, in the circuit board manufacturing process, ferric chloride solution is often used to etch copper layers on the substrate to form circuit patterns.
2. **Process steps**

Pre - treatment: Clean the surface of the workpiece to remove oil, oxide scale and other contaminants to ensure that the chemical solution can contact the surface of the workpiece evenly.

Masking: Apply a mask (such as a photoresist film) on the surface of the workpiece. The mask can protect the parts that do not need to be etched, and only expose the parts that need to be etched. The mask is usually patterned through photolithography technology.

Etching: Immerse the masked workpiece in the etching solution or spray the etching solution on the workpiece surface. The chemical reaction occurs at the exposed areas, gradually removing the material.

Post - treatment: After etching, remove the mask and clean the workpiece to remove the residual chemical solution and reaction products, and then may be followed by other surface treatment processes such as passivation.

Electrochemical - etching

1. **Principle**
- Based on the electrochemical principle, the workpiece is used as the anode, and an appropriate electrolyte solution is used. Under the action of an external electric field, anodic dissolution occurs on the surface of the anode (workpiece), so as to achieve the purpose of material removal and processing. Different from chemical etching, electrochemical etching can better control the etching rate and precision by adjusting the current density and other parameters.
2. **Process features**
- High precision: It can achieve very fine processing of micro - structures, especially suitable for processing high - precision parts such as micro - mechanical components and micro - electronic devices.
- Good surface quality: The surface of the processed parts has good surface roughness and no obvious burrs.

Plasma - etching

1. **Principle**
- Plasma is a state of matter composed of ions, electrons, free radicals and neutral atoms or molecules. In plasma etching, the gas is ionized to form plasma under the action of an external electric field or other energy sources. The active species in the plasma, such as ions and free radicals, react with the surface of the workpiece material, causing the material to be removed through physical sputtering and chemical reactions. For example, in semiconductor manufacturing, plasma etching is widely used to etch silicon wafers and other materials to form device structures.
2. **Process advantages**
- High selectivity: It can selectively etch different materials with high precision, which is crucial for complex semiconductor device manufacturing.
- High - aspect - ratio processing: It can effectively process deep and narrow structures, meeting the requirements of modern micro - and nano - scale device manufacturing for high - aspect - ratio processing.
These etching methods have their own characteristics and application scenarios, and are widely used in the fields of semiconductor manufacturing, printed circuit board production, and micro - mechanical processing.