Research on Improving the Welding Strength of Pads by Laser Cleaning Based on 3D Integration

As an important process to realize 3D integration, the cleanliness of the pad affects the welding strength of laser-based solder jet bumping and wire bonding directly. Laser cleaning is a process for cleaning organic pollutants on pads. Its advantages are high precision, high efficiency, non-contact, and cleaning the slit of 3D integration. Firstly, a laser cleaning experimental platform was established to clean the organic pollutants on micro-printed circuit and the pads on the nickel- palladium gold substrates. The cleaned and non-cleaned areas were selected for SEM analysis, and the element mass ratio of were obtained for further analysis. Secondly, the 60um gold balls were planted on those cleaned and non-cleaned areas. The destructive shear force are tested to analyze welding strength. Finaly, the laser cleaning flatness were studied through the infiltration of eutectic with different laser parameter. The result of experiment and analysis is that the laser cleaning can effectively remove the organic pollutants and improve welding quality. The optimum cleaning parameters and flatness parameters were obtained.