Improvement of PCB reliability under HAST conditions by enhancing adhesion of DFSR on PPG

The miniaturization trend in the contemporary electronics market continuously demands for printed circuit boards (PCBs) that are thinner and can house more electronic components, which makes manufacturing of PCBs of high reliability more challenging. Development efforts, accordingly, are deployed to reinforce stiffness of raw materials of PCBs, for example, adopting high stiffness dry film solder resists (DFSR) containing higher levels of inorganic fillers instead of using solder resist ink. This increase in the level of inorganic fillers, in contrast, results in the reduction of the resin content, which leads to decrease in the adhesion of the DFSR, thus reducing the reliability under high temperature and humidity conditions. In this study, Method to improve the reliability of PCBs with DFSR containing higher levels of fillers under high temperature and humidity conditions is proposed.