Introduction to etching

1. Introduction to etching:

Etching is a technique in which material is removed by chemical reaction or physical impact. Etching techniques can be divided into two categories: wet etching and dry etching. It was first used to manufacture printed embossed plates such as copper plates and zinc plates. It is also widely used in the processing of instrument panels to reduce weight, nameplates and thin workpieces that are difficult to be processed by traditional processing methods.

After improvement and the development of process equipment, it can also be used for the processing of precision etching products of electronic thin parts in the aviation, machinery and chemical industries. Especially in the semiconductor process, etching is an indispensable technology.

Our etching is commonly referred to as photochemical etching, which refers to removing the protective film in the area to be etched after exposure to plate making and development, and contacting chemical solution during etching to achieve dissolution and corrosion, forming concave-convex or hollow molding effect.

2. Etching process:

Prepare materials according to the drawings—cleaning—drying—(vacuum gold plating—filming—drawing—cleaning—drying)—printing photosensitive adhesive—drying—exposure—development—drying—etching—decoating—drying

3. Etching process flow and precautions:

1. The preparation of materials is the key to the beginning, and the color, stripes, etc. must be consistent with the sample parts;

2. Whether the cleaning is clean or not directly affects the next step of vacuum gold plating. If the cleaning is not clean, the vacuum gold plating will fall off, and rework is time-consuming and laborious. Therefore, cleaning should be done carefully, the water in the sink should be replaced in time, and the coil in the dryer should also be replaced in time. , to ensure water quality;

3. The main purpose of printing photoresist is to maintain uniformity and thickness. Only when the photoresist is heated evenly can it ensure that the photoresist does not fall off during etching;

4. Exposure and development is also an important link. Only by controlling the energy and time can the exposure be perfect, and the speed should be well controlled during development;

5. Etching is the most important part of the project. Ferric chloride etching solution is a very widely used type of etching solution. The principle of etching is to use the oxidizing property of ferric ions to generate etched metal in an acidic solution. Redox reaction, so that metal ions leave the workpiece and enter the solution to complete the etching process.

Compared with other etching solutions, it has the characteristics of low cost, easy control, relatively small odor, and regenerable waste liquid. In continuous etching, the more consistent the etching rate is, the more uniformly etched boards can be obtained, to meet this requirement.

It must be ensured that the etching solution is always kept in the best etching state during the whole process of etching. The ferric chloride etching solution is easy to regenerate and compensate, and can meet the needs of etching. It is also necessary to provide constant operating conditions and various solution parameters. Processes and equipment that can be automatically controlled

It is realized by controlling the uniformity of etching solution concentration, PH value, temperature and solution flow rate. During the etching process, the etching rate of the upper and lower plates is often inconsistent. Generally speaking, the etching rate of the lower plate surface is higher than that of the upper plate surface, due to the accumulation of solution on the upper plate surface.

The progress of the etching reaction is weakened, and the problem of unevenness of the upper and lower plate surfaces can be solved by adjusting the spray pressure of the upper and lower nozzles. It is difficult to keep the plate completely clean at all times during etching, and the edge is etched faster than the center position. Draining the system and using the nozzle swing is an effective measure.

It can further improve the pressure at the center and edge of the plate, and the method of intermittent etching at the front and rear of the plate to achieve the etching uniformity of the entire layout. have certain technology;

6. Stripping is an important step after etching. The concentration, temperature and time of stripping solution also affect the effect of the product surface after etching. Only by controlling the above working conditions can the product be in good condition.