Sep 11, 2026Technical Guide
PCB Surface Finish Comparison: HASL, ENIG, OSP and More
Compare common PCB surface finishes including HASL, ENIG, immersion silver and OSP to match finish to application and assembly needs.
The surface finish protects the copper before assembly and determines how well the board solders. Choosing the wrong one shows up as poor wettability, shelf-life problems or unnecessary cost. This comparison covers the finishes most buyers encounter and when each makes sense.
HASL: Lead-Free and Leaded
Hot air solder leveling coats the copper with solder and levels it with hot air. It is the most economical finish and offers good solderability, which is why it is common on general-purpose and high-volume boards. Lead-free HASL is the standard choice where RoHS compliance is required, while leaded HASL still appears in applications that permit it. The tradeoff is a less flat surface, which makes it a poor fit for fine-pitch components.
ENIG: Flat and Durable
Electroless nickel immersion gold deposits a nickel layer under a thin gold layer, giving a flat surface with excellent shelf life and good performance on fine-pitch assemblies. It is a common choice for HDI boards and for BGA and fine-pitch packages where surface flatness matters. Typical plating thicknesses run around 4-6um nickel with 0.1-0.5um gold for gold plating processes. The cost is higher than HASL, and the nickel layer should be managed carefully for high-reliability work.
OSP and Immersion Silver
Organic solderability preservative is a thin organic coating that protects copper and disappears during soldering. It is inexpensive, flat and suited to fine-pitch work, with the tradeoff of a shorter shelf life and sensitivity to handling. Immersion silver offers good solderability and a flat surface at moderate cost, and is a fit for fine-pitch assemblies where ENIG's nickel is not desirable.
Match the finish to the assembly process and the storage time, not to the finish you used on the last project.
Other Finishes in the Range
Immersion tin is used for press-fit and fine-pitch applications, and hard gold, or gold finger plating, is used for edge connectors where wear resistance matters. Aluminum substrate boards often use a narrower set that includes HASL, chemical tin, ENIG, OSP, IMT and plating silver, chosen for thermal and cost reasons.
How to Choose
Start with the assembly requirement and the shelf life you need. Choose HASL for cost-sensitive general boards, ENIG for flat, fine-pitch and long-shelf-life requirements, and OSP or immersion silver where flatness and economics matter more than storage time. Confirm the finish is available for your board type, then send your Gerber file and requirements and the manufacturer can confirm the finish and lead time before production.