Every finish is a compromise between solderability, flatness, shelf life, wire-bondability and price. There is no "best" one — there is the one that matches your assembly process, component pitch and shelf logistics. Here is how we talk customers through it.

ENIG — the default for fine pitch

Flat, corrosion-resistant, works for BGA and 0.3 mm-pitch QFP, stores for a year. It costs more than HASL and has one known failure mode: black pad, where the nickel corrodes before gold plating and the joint later cracks. We control it with bath-chemistry monitoring and a phosphorus-content check; if your board is high-reliability, ask for the coupon report.

HASL — still the cheapest good option

Lead-free HASL is durable, reworkable and forgiving. Its weakness is flatness: the meniscus leaves domed pads that are wrong for 0.4 mm-pitch parts and for any press-fit pin. For through-hole and coarse-pitch work, it remains the value choice.

OSP — flat, cheap, and on a clock

OSP (organic solderability preservative) is the flattest and cheapest finish, with two constraints: shelf life measured in months, and it survives limited reflow passes. Perfect for high-volume single-side SMT runs that ship straight to your line; wrong for boards that sit in a drawer.

Immersion silver and immersion tin

Silver solders beautifully and stays flat, and is friendlier to high-frequency skin effect than nickel-bearing finishes — the trade is tarnish management in packaging. Tin is flat and press-fit friendly; watch for whisker risk on pure-tin systems in fine-pitch, long-shelf-life applications.

Hard gold and ENEPIG — specialist tools

Hard gold over nickel belongs on edge connectors and keypads, where contact resistance and insertion cycles dominate. ENEPIG (electroless nickel electroless palladium immersion gold) adds palladium and solves black pad while staying wire-bondable — the premium answer for gold-wire assemblies. Neither is a general-purpose finish; both price accordingly.

Quick pick

Your caseFinish
BGA or <0.5 mm pitchENIG
Coarse pitch, cost-drivenLead-free HASL
High-volume SMT, fast consumptionOSP
RF front endImmersion silver
Edge connector / keypadHard gold
Gold-wire bondingENEPIG

Questions we get about this

What is black pad and how is it prevented?
Black pad is corrosion of the electroless nickel under the gold in ENIG, which weakens the solder joint. It is controlled by bath chemistry monitoring and phosphorus-content verification; high-reliability builds should ask for the coupon report.
Is HASL really acceptable for modern boards?
For through-hole and coarse-pitch SMT, yes — it is durable, reworkable and the cheapest finish. It is the wrong choice below roughly 0.4 mm pitch or for press-fit pins because the pads are not flat.
Which finish for a board that sits in stock for a year?
ENIG or immersion silver with proper packaging. OSP's shelf life is measured in months and it tolerates limited reflow passes.