The main purpose of PCB bath solution control is to keep all chemical components within the range specified by the process. Because the chemical and physical properties of the coating can be ensured only within the parameters specified in the process. There are many types of process methods used for control, including chemical decomposition, physical tests and acid value determination of solution, solution specific gravity or colorimetric determination. These processes are designed to ensure the accuracy, consistency and stability of the parameters of the tank. The choice of control method depends on the type of deposit. For example, the parameters of high dispersion capacity, bright high acid and low copper electroplating bath are determined by means of the split data provided by chemical methods to adjust or adjust; In addition to chemical analysis of copper solution, PH value or colorimetric determination should be carried out. If its chemical composition is within the process range after analysis; It is necessary to pay great attention to the changes of other parameters and the surface state of the plated substrate, such as bath temperature, current density, mounting method and substrate surface treatment state on the bath. In particular, it is necessary to control the inorganic impurity - zinc in bright acidic copper plating solution. If the allowable value is exceeded, the surface state of the copper layer will be directly affected. The content of copper impurities must be strictly controlled in the bath of electroplating tin lead alloy. If it exceeds a certain amount, it will affect the wettability, weldability and protection of tin lead alloy coating. Although the analytical method is reliable for bath control, it does not guarantee a good coating. Therefore, electroplating test must also be used. In particular, in order to ensure that the coating has good electrical and mechanical properties, many plating tanks add organic additives to improve the coating structure and performance. These additives by che