What is HASL Finish
HASL Finish, short for Hot Air Solder Leveling Finish, is a commonly used surface finish that involves immersing the circuit boards in a bath of molten solder, which covers the exposed copper surfaces. The excess solder is then removed, and the PCB is leveled using a hot air knife. The primary purpose of HASL Finish is to provide a solderable surface for the PCB’s components.
There are two types of HASL finishes: lead-based HASL and lead-free HASL. The lead-based HASL process is the conventional method, where molten solder containing lead is used. This results in a brighter appearance of the surface finish on the PCB. On the other hand, the lead-free HASL process is a newer alternative that does not contain lead. Instead, it utilizes an alloy with a tin-silver or tin-copper combination. The lead-free HASL finish offers high reliability, particularly in high-temperature and humidity conditions.
While HASL finishes have been widely used in the past, they are gradually being replaced by other lead-free surface finishes in the PCB industry. Examples of these alternative finishes include Electroless Nickel Immersion Gold (ENIG) and Immersion Tin, which are considered highly reliable and environmentally friendly.
English 
German