HASL is an acronym that stands for Hot Air Solder Leveling, a type of finish for printed circuit boards (PCB). Description The PCB is typically dipped into a bath of molten solder such that all exposed copper surfaces are covered by solder. Excess solder is removed by scraping the PCB with hot air knives. Advantages of HASL Excellent wetting during component soldering Disadvantages of HASL Low planarity makes this surface finish unsuitable for use with fine pitch components High therma… (More on Hasl)