Surface Finish Selection Guide

PCB Surface Finishes

The finish you pick affects solderability, flatness, shelf life and cost. Here is when to use each of the seven mainstream finishes SmartFab offers.

HASL (Lead-Free)

Hot Air Solder Leveling with lead-free SAC alloy. Low cost, robust, RoHS compliant. The default choice for through-hole and standard SMT designs.

Pros

Lowest cost mainstream finish
Long shelf life (12+ months)
Strong solder joints
RoHS compliant

Trade-offs

— Surface is not perfectly flat — not ideal for fine-pitch BGA
— Higher reflow temperatures than leaded HASL

ENIG (Electroless Nickel Immersion Gold)

$$$

Flat gold-over-nickel finish. The standard for fine-pitch BGAs, QFNs and press-fit connectors. Excellent solderability and shelf life.

Pros

Perfectly flat surface — best for fine-pitch SMT
Long shelf life (12+ months)
Wire-bondable (aluminum)
Good for press-fit

Trade-offs

— Higher cost than HASL
— Risk of "black pad" defect if process is not well-controlled — choose a vetted supplier

ENEPIG (Ni / Pd / Au)

$$$$

Premium finish: nickel, palladium, then immersion gold. The "universal" finish for boards that mix soldering, gold and aluminum wire bonding.

Pros

Eliminates black pad
Excellent for mixed assembly (solder + wire bond)
Long shelf life

Trade-offs

— Highest-cost mainstream finish
— Overkill for purely solder-only designs

OSP (Organic Solderability Preservative)

Thin organic coating over bare copper. Extremely flat, very low cost, lead-free. Best for boards assembled and shipped quickly.

Pros

Very low cost
Perfectly flat — fine-pitch friendly
Lead-free, RoHS compliant

Trade-offs

— Short shelf life (~6 months)
— No re-work tolerance — limited reflow cycles
— Not visually distinguishable from bare copper

Immersion Silver

Thin layer of pure silver over copper. Flat, solderable, good for high-frequency RF where copper purity matters.

Pros

Flat surface for fine-pitch SMT
Excellent for RF / high-frequency
Lead-free

Trade-offs

— Tarnishes with humidity / sulfur exposure
— Shorter shelf life (~6 months) — store sealed

Immersion Tin

Thin tin layer over copper. Flat, lead-free, good wetting. Common in automotive and high-volume connector applications.

Pros

Flat — good for press-fit and fine pitch
Lower cost than ENIG
Lead-free

Trade-offs

— Whisker risk in humid storage
— Limited shelf life — assemble within ~6 months

Hard Gold (Edge Connectors)

$$$$

Electroplated gold over nickel, hardened with cobalt or nickel. Wear-resistant for repeatedly mated edge fingers and contact pads.

Pros

Wear-resistant — survives 1,000+ insertions
Standard for PCIe / card-edge connectors
Excellent contact reliability

Trade-offs

— Applied selectively (gold fingers only)
— High cost per square inch

Quick recommendation

• Prototype, through-hole or coarse SMT? Lead-free HASL.
• Fine-pitch BGA / QFN at any volume? ENIG.
• Mixed solder + wire-bond assembly? ENEPIG.
• RF or high-frequency designs? Immersion silver.
• Card-edge connectors? Hard gold on the fingers.
• High-volume, fast assembly turnaround? OSP.

Get a quote with your finish of choice

All seven finishes are pre-loaded in the quote tool. Pricing updates instantly when you change finish.

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