An Innovative Flux-Less Solder Ball Attachment Technology (FLAT) for Advanced BGA Assembly

In this study, we introduced flux-less solder ball attachment Technology (FLAT), a novel and eco-friendly approach that eliminates flux residues during mass reflow while significantly reducing substrate warpage. Unlike conventional methods that depend on flux to remove oxides for bonding, the FLAT process bypasses flux altogether. Instead, it uses plasma to remove oxides and a liquid binder to secure the solder balls, which completely volatilizes at soldering temperatures. Moreover, an area laser beam is selectively applied for soldering, irradiating for just a few seconds, efficiently mitigating the issue of substrate warpage.