Hot air solder leveling

HASL or HAL (for hot air (solder) leveling) is a type of finish used on printed circuit boards (PCBs).

"HASL" redirects here. For other uses, see HASL (disambiguation).

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.^[1]

HASL can be applied with or without lead (Pb), but only lead-free HASL is RoHS compliant.

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 the process may introduce defects into PCB.

See also

• Electroless Nickel Immersion Gold (ENIG)
• Immersion Silver (IAg)
• Organic Solderability Preservative (OSP)
• Reflow soldering
• Wave soldering