Hot air solder leveling of hasl pcb, which is a process of coating molten tin-lead solder on the surface of the PCB and leveling (blow-out) with heated compressed air to form a coating layer that is resistant to copper oxidation and provides good solderability.
Hot air leveling is divided into two types: vertical and horizontal. Generally, the horizontal type is considered to be better. The horizontal hot air leveling coating is relatively uniform, which can realize automatic production. The general process is: micro-etching-> preheating-> coating flux-> spraying tin-> cleaning.
Currently, about 25% -30% of PCBs use the hot air leveling process. Hot air leveling is a dirty, unpleasant, and dangerous process, so it has never been a favorite process, but hot air leveling is an excellent process for larger components and larger spacing wires. In high-density PCBs, the flatness of hot air leveling will affect subsequent assembly; therefore, HDI boards generally do not use the hot air leveling process.