Hot air solder leveling
Appearance
HASL or hot air solder leveling is a type of finish used on printed circuit boards (PCBs).
The PCB is typically dipped into a bath of molten solder so that all exposed copper surfaces are covered by solder. Excess solder is removed by passing the PCB between hot air knives.
Advantages of HASL
- Excellent wetting during component soldering
- Avoids copper corrosion.
Disadvantages of HASL
- Low planarity on vertical levelers may make this surface finish unsuitable for use with fine pitch components. Improved planarity can be achieved using a horizontal leveler.
- High thermal stress during process may introduce defects into PCB