Hot air solder leveling

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

See also

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