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Immersion gold vs gold plating PCB: specify function first

Immersion gold identifies a chemical deposition route; electroplated gold uses an external electrical current. Neither term alone fully specifies a PCB finish. For a useful engineering comparison, state the underlayer, deposit requirements and pad function. A solderable ENIG land, a wire-bond land and a wearing edge contact may all look gold, but their functional requirements are different.

On PCB drawings, 鈥渋mmersion gold鈥� commonly refers to ENIG, where gold caps an electroless nickel layer. 鈥淕old plating鈥� is much more ambiguous. It can mean selective hard gold for contacts, soft gold for an approved bonding process, or simply a loosely described gold-colored finish. Resolve that ambiguity before requesting a quote. An order based on color may receive a plausible-looking board that does not meet the intended interface requirement.

This article owns the terminology and functional comparison. The gold plating PCB page owns manufacturing specification and quotation preparation. The ENIG PCB page owns that particular nickel/gold surface finish. Use the relevant process page after identifying what the exposed land must do rather than treating every gold-related article as an interchangeable product catalogue.

Four descriptions that should not be confused

Hard and soft describe deposit properties, while immersion and electroplated describe processes. Do not collapse those two classifications into one. Likewise, ENEPIG is a nickel/palladium/gold stack and does not become an ordinary electroplated hard-gold contact simply because its outside surface is gold. The drawing should identify the complete intended finish, not leave the fabricator to infer it from a generic purchase description.

The two conceptual stacks can have similarly named metals while differing in deposit thickness, properties and processing. The diagram is deliberately not to scale. A real fabrication note should distinguish each layer and the corresponding acceptance basis. If a customer specification already defines the finish, preserve its document number and revision instead of replacing it with a shorter website term that loses important conditions.

Solder lands need an assembly-compatible interface

For an ordinary soldered land, begin with the component land pattern and the approved assembly route. ENIG is one candidate among several solderable finishes. More gold is not automatically better for a solder joint: the deposited metals become part of a changing interface during soldering, and the accepted process must account for that. Do not select thick contact gold across solder lands simply to make the board appear more premium.

If an assembly drawing already calls for a specific ENIG requirement, a proposal to use electroplated gold must identify the exact process and explain how assembly compatibility will be established. The reverse substitution also needs review. A finish change affects an interface; it is not a cosmetic change that purchasing can make solely on lead time or price. Keep the engineering change record connected to the board revision and supplier instructions.

The board photograph gives physical context for exposed gold-colored lands and masked copper regions. It is not a measurement of gold content, deposit hardness or corrosion resistance. For ordering, use controlled specifications and agreed evidence. For investigation, preserve the lot identity and actual process records. A website image cannot establish whether two apparently similar lots have equivalent metallization.

Wearing contacts need a mating-system requirement

For an edge connector or sliding switch contact, identify the mating contact, normal force, contact travel, environmental exposure and required service duty. The finish must be considered with the whole contact system. A thin immersion-gold layer should not be substituted for a wear-qualified hard-gold deposit merely because both are gold. Conversely, adding hard gold without reviewing the mating interface does not prove the desired service life.

The gold finger PCB guide is the closer manufacturing route for board-edge contacts. Specify the contact region, edge geometry and applicable deposit requirements there. Solder lands elsewhere on the board can have another qualified finish where appropriate. A zone drawing makes that intent far clearer than a note saying 鈥済old plating everywhere鈥� when only a narrow connector strip actually needs the contact process.

This existing site photograph illustrates a board-edge contact arrangement. The visible fingers do not reveal a measured wear rating. Retain that separation between an example of geometry and proof of performance. When a customer asks for a particular number of mating cycles, identify the corresponding test and contact system rather than converting the number into a guessed gold thickness from a generic table.

Turn a vague gold request into a useful finish brief

The function planner separates soldering, wire bonding and repeated sliding contact. It also asks whether the board has several functional zones and whether electroplating access has been considered. Its output recommends the next review documents. It does not select a chemistry, predict wear life or approve plating feasibility. Unknowns remain visible so the enquiry can ask a precise question.

As an example, choose repeated sliding contacts, different functional zones and unresolved electrical access. The result asks for a contact-system review, a selective zone map and a fabrication discussion about temporary bussing. That is a more useful starting point than assigning a finish from the word 鈥済old.鈥� You can enquire immediately if those documents do not exist yet; the worksheet is optional and creates a brief only from the inputs you supply.

Bond lands are a third functional category

Wire bonding introduces its own interface requirements. Identify wire material, ball or wedge technique, pad preparation, tooling access and the planned thermal and cleaning sequence. A deposit used successfully with one bonding process is not automatically qualified for another. Soft electroplated gold or ENEPIG may be relevant candidates, and some specified ENIG wedge-bond functions are possible; the exact approved process decides suitability.

Use the ENIG versus ENEPIG comparison when that is the actual shortlist. It separates the metal structures and evidence needed for bonding. Avoid using a simple hard-gold contact specification as a substitute for the bonding house's interface requirement. Deposit composition, preparation and the wire process need a coherent specification, not a mixture of values taken from unrelated application notes.

Electroplating access and selective coverage affect layout

Electroplating needs an electrical connection during deposition. The fabricator must determine how that access is provided and how temporary connections are removed or isolated in the finished product. Those choices can influence panel design and edge details. Do not add arbitrary plating buses to production artwork without coordinated review, because an overlooked connection can conflict with the final net isolation requirement.

For selective finishing, mark the intended regions clearly and describe transitions or keep-outs. Include both sides where necessary. Ask the fabricator how the sequence will be controlled and how finished coverage will be checked. The schematic shows the idea of separate zones; it is not a manufacturable panel prescription. Actual masking, tolerances and sequencing depend on the board and process.

The demonstrates why exact process families matter: several nickel, palladium and gold systems serve different application contexts. This is supplier background, not a declaration that a particular chemistry is installed for your order. Tie any selected chemical system or finish requirement to the fabrication quotation and controlled process evidence.

Compare functional scope before precious-metal cost

Gold area and thickness are only part of a fabrication price. Selective processing, masking, panel access, setup, inspection and special test evidence can materially affect the lot. A small selective contact area may be more appropriate than changing the entire board, but that route still needs a quote. Do not calculate purchase price from gold volume and a commodity price alone; it omits the work and controls needed to deliver the board.

When requesting alternatives, label each option by function and scope. One option might be ENIG on solder lands with selective contact gold on a marked edge. Another could use a different approved solderable finish outside the same contact zone. Keep the contact requirement fixed so the comparison does not hide a performance change. If an option removes selective plating, identify what evidence will establish that the replacement meets all required functions.

The two-option allowance worksheet can compare written amounts after those definitions are settled. It accepts a selective electroplated-gold option but does not invent its rate. Record whether each per-board amount is the whole board or just a finish allowance. Include known setup and other lot charges once. Leave qualification uncertainty as an open item until its actual scope is agreed.

Example: one board, three interface responsibilities

Imagine a sensor board with soldered components, a bonded die and an edge connector. First color-code the three functional regions on a drawing. Next, ask the assembly and contact-system owners for their requirements. Then discuss with fabrication whether a common finish can satisfy any regions and where selective processing is required. The correct answer may involve more than one process, and it should be supported by the actual interfaces rather than a universal preference for gold.

For the first build, define representative verification: finish records for each region, the agreed solder and bond evaluation, and the contact evidence relevant to the mating system. A single thickness reading from a convenient large pad cannot verify every region. After review, keep the chosen stack and coverage in controlled files so future procurement does not replace the design with an ambiguous 鈥済old PCB鈥� instruction.

Send the functional drawing, quantity and known finish requirements through Contact. An incomplete request is acceptable if its open questions are explicit. The useful next step is a review of the pad functions and manufacturing scope, followed by a quotation based on those requirements. The online planner does not send files or certify a finish on your behalf.

Questions about immersion and electroplated gold