HASL was the predominant surface finish used in the industry. The process consists of immersing circuit boards in a molten pot of a tin/lead alloy and then removing the excess solder by using ‘air knives’, which blow hot air across the surface of the board.
One of the unintended benefits of the HASL process is that it will expose the PCB to temperatures up to 265°C which will identify any potential delamination issues well before any expensive components are attached to the board.

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Printed Circuit Board with HASL / Lead Free HASL Surface Finish

Advantages

  • “Nothing Solders Like Solder”
  • Easily Applied
  • Lengthy Industry Experience
  • Easily Reworked
  • Multiple Thermal Excursions
  • Good Bond Strength
  • Long Shelf Life
  • Easy Visual Inspection

Disadvantages

X – Huge Co-Planarity Difference

X – Resulting in Off-Contact Printing and

Assembly Defects

X – Contains Lead (although Lead Free available)

X – Not Suited for High Aspect Ratios

X – Not Suited for < 20 Mil pitch SMT and

BGAs

X – PWB Dimensional Stability Issues

X – Bridging Problems on Fine Pitch

Assemblies

X – Inconsistent Coating Thicknesses (on

Varying Pad Sizes)