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ENEPIG stands for electroless nickel electroless palladium immersion gold. It is a PCB surface finish made of three plated layers on the copper pads: nickel, palladium and a thin layer of gold. The palladium layer makes ENEPIG suitable for both soldering and wire bonding, and it lowers the risk of black pad compared with ENIG. ENEPIG costs more than ENIG, so it is normally chosen for wire-bonded, mixed-technology and high-reliability boards.
This guide explains what ENEPIG is, how the layers are built, typical thickness, benefits and limits, where it is used and how to order it. If you are deciding between ENEPIG and ENIG, read ENIG vs ENEPIG; to compare every finish, start with the PCB surface finish guide.
ENEPIG is a multi-layer metallic finish applied to the exposed copper pads of a printed circuit board. Its job is the same as any finish: protect the copper from oxidation and give a surface that solders reliably. What sets it apart is the palladium layer between the nickel and the gold.
The nickel layer acts as a barrier between the copper and the solder. The palladium layer protects the nickel and provides a surface for wire bonding. The thin gold layer on top keeps the palladium clean until assembly. ENEPIG is sometimes called a universal finish because one surface supports soldering and wire bonding. Some sources count the copper and describe it as a four-layer stack.
| Layer | Typical thickness | Role |
|---|---|---|
| Immersion gold (top) | About 0.03–0.1 µm (1–4 µin) | Keeps the palladium clean and solderable; thicker gold may be needed for gold wire bonding |
| Electroless palladium | About 0.05–0.15 µm (2–6 µin) | Protects the nickel and gives a bondable surface |
| Electroless nickel | About 3–6 µm (118–236 µin) | Barrier between the copper and the solder; gives a flat, hard surface |
| Copper pad | Set by the board design | The conductor being finished |
These are general industry ranges. The thickness you need depends on the standard you design to and on the bonding process, so state your requirement when you request a quote.
ENEPIG is applied after solder mask, in a chemical line where boards pass through a series of baths. The steps below are the typical sequence; details vary by manufacturer.
| Step | What happens |
|---|---|
| 1. Clean and microetch | Oils and oxides are removed and the copper surface is prepared. |
| 2. Activate | A catalyst is deposited on the copper so the nickel will plate only on the pads. |
| 3. Electroless nickel | A nickel-phosphorus layer is deposited without electric current. |
| 4. Electroless palladium | A thin palladium layer is deposited over the nickel. |
| 5. Immersion gold | A very thin gold layer is deposited over the palladium. |
| 6. Rinse and dry | Boards are rinsed and dried before inspection and packing. |
Because no electric current is used, ENEPIG needs no plating bars, so it works on dense boards with isolated pads.
| Benefits | Limitations |
|---|---|
| Supports both soldering and wire bonding | Costs more than ENIG, HASL and OSP |
| Flat pads for fine-pitch BGA and QFN | Fewer manufacturers offer it, and it is usually quoted on request |
| Significantly lower black pad risk than ENIG | Does not remove the need for good nickel plating control |
| Works with lead-free assembly and multiple reflow cycles | Not designed for repeated insertion contacts such as gold fingers |
| Long shelf life, typically about 12 months sealed | Gold wire bonding may need a thicker gold layer |
For the black pad defect and how the palladium layer reduces it, see the black pad guide.
ENEPIG is chosen when a board has requirements that ENIG or a cheaper finish does not meet well. Typical uses include:
IPC-4556 is the industry specification for ENEPIG plating. It sets the requirements for the finish, including layer thickness and test methods. If your project must meet this standard, state it in your fabrication notes so the manufacturer can plan the process and inspection. The equivalent specification for ENIG is IPC-4552.
| Finish | Flat pads | Wire bonding | Cost | Best for |
|---|---|---|---|---|
| ENEPIG | Yes | Yes | Highest of these | Wire-bonded and high-reliability boards |
| ENIG | Yes | Generally not recommended | Medium to high | Fine-pitch soldered boards |
| Immersion silver | Yes | Limited | Medium | RF and high-frequency boards |
| OSP | Yes | No | Low | Fine-pitch parts assembled promptly in one pass |
| Lead-free HASL | No | No | Low | General-purpose and volume production |
For a detailed comparison with ENIG, see ENIG vs ENEPIG. For the other options, see the PCB surface finish options page.
| Topic | Tip |
|---|---|
| Specify the finish clearly | Write ENEPIG, and the standard if one applies, in your fabrication notes and in the quote request. |
| Mark wire-bonded pads | Tell the manufacturer which pads will be wire-bonded, the wire type and diameter, and the pad size. |
| State gold requirements | If gold wire bonding needs a specific gold thickness, give the value up front so it can be confirmed. |
| Plan storage and assembly | Keep boards sealed in their original packaging and follow your assembler's storage rules. |
| Use a different finish for contacts | For edge connectors and frequently mated contacts, use hard gold instead. |
For edge connectors, see the PCB gold fingers guide.
ENEPIG is available through NextPCB's advanced PCB quote, where our engineers review your files. If your board needs wire bonding or a specific layer thickness, tell the engineers before you order. For ENIG, which is available in both the standard and advanced quotes, see the ENIG PCB surface finish guide. You can also check what we can build in the advanced PCB manufacturing capabilities.
ENEPIG stands for electroless nickel electroless palladium immersion gold. It describes the three layers plated on the copper pads: nickel, palladium and gold.
ENEPIG plating deposits nickel, palladium and a thin immersion gold layer onto copper pads. It protects the copper from oxidation and gives a surface suited to both soldering and wire bonding.
Typical industry values are about 3–6 µm of nickel, 0.05–0.15 µm of palladium and 0.03–0.1 µm of gold. The exact requirement depends on the standard and the bonding process, so confirm it with your manufacturer.
ENEPIG is used for wire-bonded boards, boards that combine soldered parts and bare dies, fine-pitch BGA and QFN assemblies, RF modules and high-reliability industrial, medical, automotive and aerospace electronics.
Yes. The palladium and gold layers give a bondable surface for gold and aluminum wire, depending on the layer thickness. State your wire type and pad requirements so the thickness can be confirmed.
It reduces the risk significantly, because the palladium layer protects the nickel during gold deposition. It does not remove the need for good nickel plating control.
Yes. ENEPIG adds a palladium layer and an extra process step. The difference varies with board size and quantity, so quote the same design with both finishes to compare.
ENEPIG is the standard name and uses an electroless palladium layer. ENIPIG, with an immersion palladium layer, is a related variant that some suppliers use. Ask your manufacturer which process they run if it matters for your design.
IPC-4556 is the industry specification for ENEPIG plating on printed circuit boards. It covers requirements such as layer thickness and test methods.
A typical industry figure is about 12 months when boards are kept sealed in their original packaging, but it depends on packaging and storage conditions. Follow your assembler's storage rules.
Yes. ENEPIG is available through the advanced PCB quote, where engineers review your files.
Request ENEPIG through the advanced PCB quote and have our engineers review your wire bonding and reliability requirements.
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