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PCB gold fingers (also called edge fingers, edge connectors or golden fingers) are the gold-plated contact pads along the edge of a printed circuit board. They plug into a socket and carry power and signals between two boards, such as a graphics card or memory module and a motherboard. Gold fingers are normally made with electroplated hard gold over nickel, which resists the wear of repeated insertion far better than the thin immersion gold used for soldering pads.
This guide covers what gold fingers are, hard gold vs ENIG, typical applications, design specifications, the plating and beveling process, DFM tips and how to order gold finger PCBs. To see how gold fingers fit with the other finishes on the same board, read the PCB surface finish guide or the surface finish options NextPCB supports.
Gold fingers are a row of gold-plated copper pads at the edge of a PCB. When the board is inserted into a female connector, the fingers press against spring contacts in the socket and complete the electrical connection. The gold plating keeps the contact resistance low, resists corrosion and survives repeated mating cycles.
| Attribute | Gold fingers |
|---|---|
| Also called | Edge fingers, edge connector contacts, golden fingers |
| Location | Along the edge of the board, facing outward |
| Plating | Electroplated nickel, then hard gold (gold alloyed with a hardening metal such as cobalt) |
| Purpose | Repeated plug-in connection with low contact resistance and wear resistance |
| Typical gold thickness | About 30–50 µin (0.76–1.27 µm), depending on the application class |
| Edge treatment | Beveled (chamfered), typically at 30° or 45° |
| Common uses | PCIe, M.2, DIMM, ISA, PCI and AGP cards, backplanes and plug-in modules |
A common misconception when sourcing PCBs is to treat all gold finishes the same. For gold fingers, the type of plating decides whether a board survives a handful of insertions or many.
>> Recommended reading: HASL vs ENIG: An Ultimate Guide on Surface Finish
Gold fingers primarily use electroplated nickel gold, commonly called "hard gold".
ENIG is an excellent surface finish for soldering pads, but it is generally too thin and soft for edge connectors. The immersion gold layer wears through quickly under repeated insertion, exposing the nickel beneath. For cost-sensitive prototypes that will rarely be unplugged, some designers choose ENIG, but hard gold is recommended for any connector that will be mated repeatedly.
| Factor | Hard gold (electroplated) | ENIG (immersion) |
|---|---|---|
| Deposition | Electrolysis (needs a plating bar) | Chemical reaction, no current |
| Gold thickness | Thick, typically 30–50 µin | Very thin, typically 1–3 µin |
| Wear resistance | High (alloyed, hardened gold) | Low |
| Designed for | Repeated plug-in contact | Soldering |
| Cost | Higher | Lower |
| Use on gold fingers | Recommended | Only for rarely mated prototypes |
Most boards with gold fingers also have soldering pads that need their own finish. Hard gold is plated on the fingers only, while the rest of the board uses a soldering finish such as ENIG or HASL or lead-free HASL. State both finishes in your order notes, and see the OSP guide if you are considering OSP for the other pads.
Gold fingers act as the plug-in connectors between boards. With PCIe generations moving to higher data rates, the precision of these contacts matters more than ever.
| Application | Examples |
|---|---|
| Expansion cards | ISA, PCI, PCI Express (PCIe) and AGP cards that plug into a motherboard slot |
| Memory and storage | DIMM memory modules and M.2 SSDs |
| Graphics and audio | GPUs and high-fidelity sound cards |
| External connections | Peripherals such as scanners, speakers and industrial monitors that connect through edge connector slots |
| Industrial and embedded | Backplanes, plug-in modules and test fixtures |
To keep your project on schedule, your design must follow the manufacturing rules for plated edge connectors. NextPCB checks these details during its DFM (Design for Manufacturing) analysis.
| Item | Rule |
|---|---|
| Gold thickness | Typically 30–50 µin. About 32 µin is a common balance of cost and durability for standard mating. |
| Hardness | Use hard gold (alloyed with cobalt or nickel) for plug-in contacts. |
| Visual quality | Per IPC-A-600, the surface must be smooth and clean, free of burrs, nickel foot and exposed copper. |
| Keep-out zone | No plated through-holes, SMD pads or silkscreen within 1.0 mm of the gold fingers. |
| Solder mask | The solder mask must not cover the fingers; define an opening (window) over them. |
| Orientation | Fingers must face outward from the board edge to allow insertion. |
| Bevel angle | Typically 30° or 45°; specify the angle your connector needs. |
Gold fingers need steps that standard boards do not, so they add processing time and cost compared with an ordinary PCB.
| Step | What happens |
|---|---|
| 1. Plating bar (tie-bar) | A bar along the panel edge connects every finger so current can flow during electroplating. |
| 2. Masking | Areas that should not be plated are protected, so only the fingers are exposed. |
| 3. Nickel and hard gold plating | Nickel is plated first as a barrier layer, then hard gold is electroplated on top. |
| 4. Other surface finish | The rest of the board receives its soldering finish, such as ENIG or HASL. |
| 5. Beveling | The board edge is cut at an angle so it slides into the connector without damaging the contacts. |
| 6. Plating bar removal | The tie-bar is routed off after plating. |
Because hard gold is electroplated, current must reach every finger. The plating bar is added at the panel edge and removed after plating. If your gold fingers are not on the board edge, electroplating becomes difficult or impossible without special lead lines.
Beveling lets the board fit easily into a female connector, such as a PCIe slot, without damaging the contacts.
| Tip | Why it matters |
|---|---|
| Pull copper back from the finger edge (usually about 3 mm on inner layers) | Prevents copper being exposed by beveling, which could cause short circuits. |
| Plan staggered fingers for hot-swap designs | Some fingers are shorter so power connects before or disconnects after data. Confirm your manufacturer can hold the tolerances on segmented fingers. |
| Match impedance through the finger transition | Gold fingers are part of the high-speed signal path, and a mismatch causes reflection. |
| Avoid fingers on multiple edges unless needed | Each extra edge adds plating and beveling steps and cost. |
| Keep fingers on the board edge | Fingers away from the edge are hard to electroplate without special lead lines. |
Hard gold, electrolytic gold and gold fingers are available through the advanced PCB quote. Upload your files, select the gold finger option and state the bevel angle your connector needs. NextPCB engineers review gold finger designs against the rules above before production. For current limits on layer count, board thickness and other parameters, see the advanced PCB manufacturing capabilities, and for turnkey projects see PCB assembly services. You can also check your Gerber files for free with the DFM analysis tool before you order.
PCB gold fingers are the gold-plated contact pads along the edge of a board. They plug into a socket to connect two boards, for example a graphics card to a motherboard.
Immersion gold (ENIG) is a chemical process that deposits a very thin gold layer, typically 1–3 µin, mainly for soldering. Gold fingers use electrolysis to deposit a thick layer of hard gold, typically 30 µin or more, for mechanical wear and repeated insertion.
Hard gold is electroplated gold alloyed with a small amount of a hardening metal such as cobalt or nickel. It is plated over nickel and is used where contacts are mated repeatedly.
Gold fingers are typically plated to about 30–50 µin of hard gold depending on the application class, with about 32 µin a common balance of cost and durability. Confirm the thickness your connector requires.
Beveling tapers the board edge, usually at 30° or 45°, so the board slides into the connector without catching or damaging the contacts.
Yes, double-sided gold fingers are common, for example on memory modules. Fingers on more than one edge add plating and beveling steps and increase cost.
Only for prototypes that will rarely be unplugged. The immersion gold in ENIG is very thin and wears through quickly under repeated insertion, so hard gold is recommended for production boards.
Cost is driven by the price of gold and the extra processing steps: masking, electroplating and beveling. Placing fingers on only one edge and using efficient panelization keeps costs down.
Repair is difficult but possible with plating rework kits or gold conductive epoxy. A repaired finger will not be as durable as the original electroplated gold, so replacement is usually required for production batches.
Gold fingers are a small part of the board, but they decide how reliable the connection is. Get your gold finger design checked and quoted at NextPCB, where engineers review every gold finger design before production.
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