The etching of printed circuit board

Etching is the process of evenly spraying the etching solution onto the surface of copper foil under certain temperature conditions through a nozzle, which undergoes an oxidation-reduction reaction with copper without the protection of an etching inhibitor. Unneeded copper is removed, and the substrate is exposed before being peeled off to form the circuit. The main components of etching solution: copper chloride, hydrogen peroxide, hydrochloric acid, soft water.

 

The characteristics of printed circuit board etching are relatively low manufacturing costs, high efficiency, and the ability to manufacture complex printed circuit boards.

 

But it also has some points to pay attention to, first of all, the selection and ratio of etching liquids, as different liquids have different adaptability to different printed circuit boards.

 

Secondly, for the treatment of processed etching liquids, it is necessary to pay attention to environmental issues and not discard them directly into nature. In addition, it is also necessary to control the appropriate etching time and temperature, and excessive etching is not allowed, otherwise it will affect the quality of the pritned circuit board.

 

Usually, the longer the printed circuit board is immersed in the etching solution, the more severe the side corrosion situation. Side erosion will seriously affect the accuracy of wires, and severe side erosion will make it impossible to produce fine wires. When the lateral erosion and protrusion decrease, the etching coefficient will increase, and a high etching coefficient indicates the ability to maintain thin wires, allowing the etched wires to approach the original scale.

 

There are many factors that affect side corrosion

1.Etching method

Soaking and bubbling etching can cause larger side corrosion, while splashing and spray etching have smaller side corrosion, with spray etching having the best effect.

 

2.Type of etching solution

Different etching solutions have different chemical compositions, resulting in different etching rates and etching coefficients.

For example, the etching coefficient of the calculated winning copper chloride etching solution is 3, while the etching coefficient of the alkaline copper chloride can reach 4.

 

3.Etching rate

Slow etching rate can cause severe lateral corrosion. Improving the etching quality is closely related to accelerating the etching rate. The faster the etching rate, the shorter the time the substrate stays in the etching process, the smaller the amount of side etching, and the clearer and more orderly the etched patterns.

 

4.PH value of etching solution

When the pH value of alkaline etching solution is high, etching will increase.

If the density of alkaline etching solution is too low, it will aggravate side corrosion. Choosing an etching solution with high copper concentration is very beneficial for reducing side corrosion.

 

5.Copper foil thickness

It is best to use thin copper foil for etching thin wires with minimal side erosion. The thinner the wire width, the thinner the copper foil thickness should be.

 

 

In order to achieve high-quality printed circuit board etching, it is also necessary to master some techniques, such as selecting appropriate etching solution and enhancing exposure time. In addition, printed circuit board etching also requires the use of some auxiliary equipment, such as exposure machines, developers, etc.