Research Of The Steam Laser Cleaning Printed Circuit Board By Tea-CO₂ Pulse Laser

China is the second supplier of printed circuit boards(PCB) in the world now, and it is thought to be the largest supplier in the next year. During the process of PCB, cleaning is a very important step since the PCB surface absorbs a large amount of pollutant, such as micro particles and oxides. Since the traditional cleaning methods not only need using ODS solvent, but also are unable to remove the micron particles,they can't satisfy the requirements of modern electrical technology.Laser cleaning is considered as a promising cleaning method because of its advantages of non-pollution and non-contact.Steam laser cleaning(SLC) is a way to remove the particles by using laser radiating the liquid film. When the laser radiates, the liquid film on the PCB surface explodes, vaporizes, and produces force. The force is powerful enough to remove the particles .The theoretical and experimental investigations of SLC PCB have been carried out in this paper. Firstly,the adhere force between particles and the PCB surface was calculated. Secondly,the simulation of removing force produced by the exploding liquid using Ansys/Ls-dyna software was performed. Comparing with these two forces, it can be found that using SLC to clean PCB is feasible. Furthermore, the experimental studies of dry laser cleaning were also carried out. The results show that dry laser cleaning PCB is impossible because the cleaning threshold of the CuO is much higher than that of the damage threshold of the resin. The SLC PCB using neutral liquid is also impossible. Then, a new SLC PCB method was developed. By using the weak acid as the liquid film, the CuO on the surface of the Cu film and the micro-particles can be removed at the same time. Lastly, the influence of process parameters, such as energy density, composition of liquid and laser pulse number on the cleaning quality was also investigated in this paper. The result shows that the composition of liquid has significant effects on the cleaning efficiency. Among the three liquids, acetum has the best result.