Micro-structure analysis of solder joint using room temperature Laser-Assisted Bonding (LAB) process

We performed a bonding process of a daisy chain chip on a stage at room temperature using an epoxy-based, unique bonding material developed for the Laser-Assisted Bonding (LAB) process; the material is called ‘Laser Epoxy Paste’. This material is epoxy-based, contains certain additives to remove oxide of solder surface, and does not contain volatile components such as solvents, which are usually contained in conventional fluxes. Therefore, material does not generate fumes during process and is suitable for processes with short temperature profiles, such as LAB processes. This material does not require cleaning process after bonding, so it is eco-friendly, and it also acts as an underfill after post-curing. By controlling the laser power and irradiation time, we adjusted the stage temperature from 25°C to 100°C and adjusted the parameters so that the peak temperature became 260°C. Using an optical microscope (OM), scanning electron microscope (SEM), and Energy-dispersive X-ray spectroscopy (EDAX), we performed reliability tests of the bonded samples and analyzed microstructural changes before and after the reliability test.