With the development of the PCB industry, the impedance requirements of various wires have become higher and higher, which inevitably requires more stringent control of the width of the wires. In order to enable the engineering management personnel of Rongxin Company, especially the process engineering personnel responsible for the etching process, to have a certain understanding of the etching process, this training material was written to help production management and monitoring, and to improve our products from the surface. quality.
- The basic principle of the etching machine
(1) Purpose of etching
The purpose of etching is to etch the unprotected non-conductor part of the copper on the patterned circuit board made in the previous process to form a circuit.
Etching includes inner layer etching and outer layer etching. The inner layer adopts acid etching, and the wet film or dry film is used as the resist; the outer layer adopts alkaline etching, and the tin-lead is used as the resist.
(2) Basic principle of etching reaction - Acidic copper chloride etching solution
- Features
－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
- The main reaction principle
During the etching process, CU2+ is oxidizing, and the copper on the board surface is oxidized to CU+: Cu+ CuCl2→2CuCl
The generated CuCl is insoluble in water, and soluble complex ions are generated in the presence of excess chloride ions:
2CuCl＋4Cl-→2[CuCl3]2-
As the reaction progresses, there are more and more CU+, and the copper etching ability decreases. The etching solution needs to be regenerated to make CU+ become CU2+. There are several regeneration methods: oxygen or compressed air regeneration (low reaction rate), chlorine regeneration (fast reaction, but toxic), electrolytic regeneration (copper can be directly recovered, but electrolysis regeneration equipment and higher power consumption are required. ), sodium hypochlorite regeneration (high cost, more dangerous in itself), hydrogen peroxide regeneration (fast reaction rate, easy to control).
Reaction: 2CuCl+2HCl+H2O2→2CuCl2+2H2O
Automatic control adding system: by controlling the etching speed, the adding ratio of hydrogen peroxide and hydrochloric acid, specific gravity and liquid level, temperature and other items, to achieve automatic continuous production.
