What is the principle and process flow of an etching machine?

With the development of the PCBT industry, the impedance requirements for various wires are becoming increasingly high, which inevitably requires stricter control over the width of the wires. In order to provide the engineering management personnel of Rongxin Company, especially the process engineering personnel responsible for the etching process, with a certain understanding of her etching process, this training material is written to help with production management and monitoring, and to improve the quality of our company's products.

Etching machine The basic principles of

(1) The purpose of etching

The purpose of etching is to remove the unprotected non-conductive copper on the patterned circuit board made in the previous process, forming a circuit.

Etching includes inner layer etching and outer layer etching, with the inner layer using acidic etching and wet or dry film as the resist; The outer layer adopts alkaline etching, with tin lead as the resist.

(2) Basic principle of etching reaction

Acidic copper chloride etching solution

1. Characteristics

The etching speed is easy to control, and the etching solution can achieve high etching quality in a stable state

Large amount of copper corrosion

Etching solution is easy to regenerate and recycle

2. Main reaction principle

During the etching process, CU2 has oxidizing properties and oxidizes the surface copper to CU: Cu CuCl2→2Cucl

The generated CuCl is insoluble in water and forms soluble complex ions in the presence of excess chloride ions

2CuCl 4Cl-→2[CuCl3]2-

As the reaction progresses, the amount of Cl increases and the ability to corrode steel decreases. It is necessary to regenerate the Cu from liquid to CU2. There are several methods of regeneration, including oxygen or compressed air regeneration (with low reaction rate), chlorine gas regeneration (with fast reaction but toxic), electrolytic regeneration (which can directly recover copper but requires electrolytic regeneration equipment and high electricity consumption), sodium hypochlorite regeneration (with high cost and inherent danger), and hydrogen peroxide regeneration (with fast reaction rate and easy control)

Reaction: 2CuCl 2HCl H2O2→2CuCl2 2H2O

Automatic control addition system: By controlling the etching speed, the addition ratio of hydrogen peroxide and hydrochloric acid, specific gravity and liquid level, temperature and other items, automatic continuous production can be achieved.