What is Lead Free HASL
Lead free HASL (Lead-Free Hot Air Solder Leveling) is a surface finish technique used in the PCB industry. It is an environmentally friendly alternative to the traditional HASL process, as it does not use lead in the solder alloy.
Lead free HASL involves applying molten solder to the circuit board, ensuring proper wetting and adhesion. Excess solder is then removed using air knives set at a temperature above the melting point of the lead-free solder, resulting in a smooth and level surface. The board is then washed to remove any flux residues that may impact performance and reliability.
Lead free HASL is in compliance with RoHS regulations, making it a preferred choice for environmentally conscious applications. It also offers good solderability and a relatively low cost compared to other surface finish techniques.
However, lead free HASL has limitations regarding smaller components, as the difference in thickness and topography between large and small pads can pose challenges during the soldering process. Additionally, the high processing temperature required for lead free HASL may not be suitable for components with a pitch of less than 20mil.