Laser patterning of lead frames for electroplating

A novel dry manufacturing process is proposed to replace some of the processing steps in the existing wet silver plating process. It involves the combination of high speed laser patterning and ablation techniques on a polymer masked copper leadframe. A Q-switched Nd-YAG laser with high speed scanning mirrors was initially used in this study. The suitable polymer coating for the relevant electroplating bath has been identified by immersion test and scanning electron microscopy. Process parameters such as scanning rate, protection gas, laser powder, beam size, working distance etc., were investigated. The effect of laser ablation and residual heat input upon the microstructure and properties of the metallic substrate were studied. The plating quality after laser patterning was also examined. A transparent organic film about 1.5 μm thick was found to be loosely adhered on the copper substrate regardless of the ablation conditions. This film created a major obstacle to the YAG laser ablation process proposed. Excimer laser was used to overcome this problem.