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Auto Nick Gold Plating Line — ENIG (Electroless Nickel Immersion Gold) Production Line
Automated PCB / FPC surface finishing line for ENIG (Electroless Nickel Immersion Gold). 21-stage conveyor line: electro-clean, activator, electroless nickel, post-rinse cascade, immersion gold, and final rinse/dry. Available in 1-shift, 2-shift, and 3-shift configurations for 50–500 m²/month target output. Same supplier as your etching and exposure lines for single-warranty, single-commissioning, single-spare-parts support.
Auto ENIG plating line installed in a Korean PCB shop — 21-stage conveyor with PLC control.
What Is ENIG and Why Use It?
ENIG (Electroless Nickel Immersion Gold) is a two-layer surface finish applied over the copper pads of a PCB. A 3–5 µm electroless nickel layer is deposited first to act as a barrier against copper diffusion and to provide a hard, flat surface. A 0.05–0.1 µm immersion gold layer is then deposited on top of the nickel to prevent oxidation and to provide a highly solderable surface that survives 12 months of shelf storage. ENIG is the preferred finish for fine-pitch BGA, QFN, and wire-bonding applications, and is widely used in medical, automotive, and aerospace electronics.
Compared to other finishes, ENIG is flat (no meniscus or co-planarity issues like HASL), lead-free, RoHS compliant by default, and gives a long shelf life. The trade-off is cost — ENIG uses more chemistry and a longer line than HASL or OSP, but the per-board cost is competitive for fine-pitch and high-reliability work. For more on the chemistry and the role of gold, see our ENIG plating machine product page and the related OSP coating line for comparison.
21-Stage Process Flow
The full ENIG sequence is performed in a single horizontal conveyor line. Each station is a separate process tank with its own chemistry, temperature control, and rinse cascade. The panels travel through the line on a continuous stainless-steel rack.
01
Load.
PCB panels loaded on horizontal rack, 50–100 panels per rack.
02
Electro-clean.
Anodic + cathodic alkaline cleaner to remove organics, oils and oxides from copper.
03
Drag-out rinse.
Recovered DI water; the rinse returns to the electro-clean tank to extend chemistry life.
04
CW rinse 1 / 2 / 3.
Three-stage counter-flow city-water cascade to remove cleaner residue.
05
Acid activator.
10% sulfuric acid or proprietary activator to activate the copper surface for nickel deposition.
06
Drag-out rinse.
Recovered DI water returning to the acid tank.
07
CW rinse 1 / 2.
Counter-flow city-water cascade.
08
Electroless nickel.
3–5 µm Ni-P deposit from sodium hypophosphite-reduced bath at 85–90 °C, pH 4.5–5.0, 20–25 minutes.
09
Drag-out rinse.
Recovered DI water; returns to the nickel bath to extend life.
10
CW rinse 1 / 2 / 3.
Counter-flow cascade.
11
Pre-dip.
Dilute gold bath chemistry to condition the nickel surface.
12
Immersion gold.
0.05–0.1 µm Au deposit by galvanic displacement, 7–12 minutes at 85–90 °C.
13
Drag-out rinse.
Recovered DI water returning to the gold bath.
14
CW rinse 1 / 2.
Counter-flow cascade.
15
Second pre-dip.
Conditioning bath before final rinse.
16
Final DI rinse.
18 MΩ·cm DI water cascade.
17
Hot DI rinse.
50–60 °C DI water, final surface preparation.
18
Hot air dry.
80–100 °C air-knife drying.
19
Cooling.
Ambient air to room temperature.
20
Unload.
Automatic rack unloader; racks return to the load station.
Same supplier as your etching and exposure lines. The ENIG line, the etching machine, the exposure machine, and the developing machine are all from Golden Eagle. One commissioning engineer, one warranty, one set of spare parts, one shipping container.
21-stage full sequence. Most competitors cut the line to 14–16 stages; we include the full pre-dip cascade and the second activator bath that are critical for consistent gold thickness on inner layers and high-aspect-ratio plated holes.
Counter-flow DI cascade. 3-stage counter-flow rinse reduces DI water consumption by 60% and extends the gold bath life by 30–40%.
On-site chemistry commissioning. The chemistry supplier (Uyemura or Atotech equivalent) is on-site for the first 5 days of production to dial in the bath parameters for your panel format and via aspect ratio.
Spare parts from stock. Pumps, heaters, filters, spray nozzles stocked in our Beijing warehouse and ship by DHL within 3–5 days worldwide.
Frequently Asked Questions
What is the difference between ENIG and ENEPIG?
ENIG (Electroless Nickel Immersion Gold) is a two-layer finish: Ni-P + immersion Au. ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold) adds a 0.05–0.1 µm electroless palladium layer between the nickel and the gold. ENEPIG is preferred for wire bonding and for high-reliability applications where nickel corrosion ("black pad") is a concern. The line we ship is ENIG; the ENEPIG option is available as an upgrade with 3 additional tanks.
How often do I need to replace the gold bath?
The gold bath is replenished continuously based on ampere-hours or panel count; the bath itself is dumped and rebuilt every 3–6 months depending on workload. With proper maintenance, gold consumption is 0.5–0.8 g per 100 m² of PCB. For a 150 m²/month line, plan on 1–2 kg of gold per year and a chemistry cost of USD 30,000–50,000/year. We can supply gold recovery service through a third-party refiner if you want to recycle the drag-out.
What is "black pad" and how do I avoid it?
"Black pad" is a nickel corrosion phenomenon that occurs when the immersion gold reaction is too aggressive or when the nickel deposit has excessive phosphorus segregation. It appears as dark spots on the gold surface and leads to solderability failures. It is avoided by: (1) keeping the gold bath at 85–90 °C and pH 4.5–5.0, (2) using a moderate gold concentration (1–2 g/L), (3) limiting immersion time to 7–12 minutes, and (4) controlling the nickel bath phosphorus content to 6–9%. Our line ships with a dedicated pre-dip step that minimizes black pad risk on inner layers.
Can the same line be used for both ENIG and OSP?
Yes — the ENIG line and the OSP line share the same pre-treatment section (electro-clean, acid activator, rinse cascade). The chemistry switching is done by replacing the nickel + gold tanks with the OSP tanks, which takes about 4 hours. Most commercial PCB shops run ENIG and OSP on the same line, decided by the daily production plan. For details on the OSP option see our OSP coating line product page.
How much does a 21-stage ENIG line cost?
A 21-stage semi-automatic ENIG line costs USD 280,000–400,000 ex-works. A fully automatic version with PLC, MES interface, automatic dosing pumps, and robotic load/unload runs USD 500,000–700,000. Plan on USD 30,000–50,000/year for chemistry, USD 1,000–2,000/year for spare parts, and a one-time commissioning fee of USD 5,000–10,000 for the chemistry supplier on-site visit. The line is delivered in 90–120 days and installed in 30–45 days.
Do you supply the upstream exposure and downstream etching as well?
Yes — we supply the full PCB imaging and surface finishing line as a turnkey package: cutting, drilling, deburring, dry-film lamination, UV-LED or LDI exposure, developing, etching, ENIG (this line), OSP, and HASL. For details on the upstream exposure step see our PCB exposure machine buyers guide and for the downstream HASL option see our HASL machine product page.
_plating_machine_for_PCB.jpg "Electroless Nickel Immersion Gold production line")
