Surface Finish Selector
Compare solder-pad finishes by flatness, nickel content and a documented wire-bond route. Treat wear contacts as a separate finish requirement.
Six solder-finish families.
Selective hard gold is reviewed separately.
Define the function of each surface.
A candidate finish family still needs a qualified chemistry, thickness, assembly process and acceptance plan.
No screening result until JavaScript loads.
Separate screening from qualification.
The rules first filter the solder-pad finish families. A separate contact-area message addresses repeated wear. Gold fingers must not silently turn every SMT pad into hard gold. Contact finish reference
Environmental exposure and reflow count create review flags. The tool does not invent a universal number of permitted cycles or a shelf-life guarantee.
Flatness and nickel are direct requirements
The flat-pad filter excludes HASL in this reference screen. A nickel-free requirement excludes ENIG and ENEPIG because nickel is part of their deposited stack. A nickel-free board-wide finish requirement also conflicts with the reference hard-gold-over-nickel contact process.
Wire bonding is process-specific
The curated gold-wire route is ENEPIG. Immersion-silver suitability must be qualified for the selected wire and bonding process. Other qualified combinations may exist, including process-specific ENIG or ENEPIG bonding. Not being in this reference set means “not established here,” not physically impossible.
Do not use blanket process rules
Modern OSP chemistries can support multiple reflows. Confirm actual chemistry, deposit thickness, storage and thermal history rather than assuming every OSP is limited to one cycle. OSP process source
What belongs in the fabrication drawing
Identify finish areas, specified chemistry or governing finish standard, thickness and acceptance criteria, bond pads, contact-finger wear requirements, masking boundaries, storage / packaging and qualification tests. All candidates require engineering approval.
Questions before
you use the result.
Know what the tool answers—and what still needs engineering review.
Why is hard gold not in the solder-pad list?
The reference hard-gold-over-nickel process is evaluated separately for repeated-mating contact fingers. It is not silently assigned to all solderable pads.
Is ENIG always unsuitable for wire bonding?
No. Wire bonding depends on the specific process, wire and deposit stack. This limited library only passes the wire-bond routes explicitly documented in its records.
Can the tool promise 12 months of shelf life?
No. Packaging, environment, chemistry, deposit thickness and prior thermal exposure matter. Agree the storage and solderability acceptance requirements with the supplier.
Technical references & data basis
- Würth Elektronik — Technical Delivery Specification, solder and contact surfaces (PDF)
- Würth Elektronik — How does your PCB layout influence the costs in PCB manufacturing? (PDF)
- Würth Elektronik — PCB Technology: Solder Surfaces (PDF), ENIG
- Uyemura — ENEPIG process
- Würth Elektronik — PCB Technology: Solder Surfaces (PDF), immersion silver
- MacDermid Japan — Final Surface Treatment, immersion tin
- MacDermid Japan — ENTEK PLUS HT OSP process information
Check the linked manufacturer data and calculation references when using your results. Confirm the exact material grade and applicable document revision before production.