Acidic etching solution is generally suitable for the inner circuit pattern production of multilayer printed boards. Compared with the FeCl3 etching method, the acidic CuCl2 etching method in the etching machine has a larger amount of molten copper, and the etching speed is easy to control. The etching solution is easy to regenerate and recycle. , less environmental pollution, the same scope of application to the resist layer.
The acidic CuCl2 etching solution is mainly composed of CuCl2, NaCl, HCL and so on. In this etching solution, because Cu2+ in CuCl2 is oxidizing, the copper on the surface of the part is oxidized to Cu+ in the Xinhengli vacuum etching machine, and Cu+ and Cl- combine to form Cu2Cl2. The chemical equation is: Cu+CuCl2= Cu2Cl2. The generated Cu2Cl2 is insoluble in water. In the presence of excess Cl-, this water-insoluble Cu2Cl2 and excess Cl- form complex ions to detach from the surface of the etched copper to complete the etching process. The chemical equation is: Cu2Cl2+4Cl-=2[CuCl3]2-
With more and more Cu+ in the etching machine, the etching ability will decrease rapidly, and eventually lose the etching ability. In order to ensure the corrosion ability of the etching solution, the etching solution can be regenerated in various ways to oxidize Cu+ into Cu2+. For the specific formula of the etching solution, please contact: 0757-86677701.
Effect of Cl- concentration in etching solution on etching rate: In acidic CuCl2 etching solution, both Cu2+ and Cu+ exist in Xinhengli etching machine in the state of complex ions. Copper is a friendly complex former due to its incomplete d-orbital electron shell. In general, four coordination bonds can be formed. When the etching solution in the etching machine contains a large amount of Cu-, Cu2+ exists in the form of copper tetrachloride ([CuCl4]2-), and Cu+ exists in the form of copper trichloride ([CuCl3]2-). Therefore, during the working process of the etching machine, the configuration and regeneration of the etching solution require a large amount of Cl- to participate in the reaction. At the same time, the concentration of Cl- also has a direct relationship with the etching speed, and the high concentration of Cl- is conducive to the formation of various copper complex ions, which accelerates the etching process.
The reason why adding Cl- can increase the etching rate is that when the etching reaction of copper occurs in the CuCl2 solution, the generated Cu2Cl2 is not easily soluble in water, and a layer of CuCl film is formed on the surface of the copper, which can prevent the further progress of the etching process. conduct. At this time, excess Cl- can complex with Cu2Cl2 to form soluble [CuCl3]2-, which dissolves from the surface of copper, thereby increasing the corrosion rate of Xinhengli etching machine.
Effect of temperature on etching process rate: As the temperature of the chemical solution in the etching machine increases, the etching rate increases. However, too high temperature will cause excessive volatilization of hydrochloric acid, resulting in an imbalance in the proportion of etching solution components, and too high temperature will damage the resist layer. Through many years of practical experience of Xinhengli, the temperature is controlled at 40 ℃~ 52°C is suitable.