Name: Enig Immersion Gold PCB
Brand: PCB Printed Circuit Board and PCBA manufacturing
Availability: InStock
Rating: 5 (1 reviews)

Description
Data Sheet

ENIG (Electroless Nickel Immersion Gold) delivers superior surface flatness, coating uniformity, solderability and corrosion resistance. It is widely adopted as the mainstream surface treatment solution for circuit boards in consumer electronics, industrial control, communication and high-precision electronic products.

ENIG Material & Layer Classification

ENIG is commonly referred to as immersion gold. Standard PCB electroless nickel adopts medium-phosphorus formula with 7%~9% phosphorus content. According to phosphorus proportion, chemical nickel is divided into three grades: low-phosphorus (matte), medium-phosphorus (semi-gloss) and high-phosphorus (bright). Higher phosphorus content provides stronger resistance to acidic corrosion. Typical process types include conventional copper-deposited nickel and nickel-palladium-gold integrated plating.

Common ENIG quality defects cover black pad (black disc) and mud crack fracture. Black pad refers to local corrosion of the nickel layer turning gray-black, which seriously weakens solderability.

Immersion gold is classified by thickness:

Thin gold (displacement gold): 1~5 μin, the mainstream specification for mass production;
Thick gold (reduction gold): over 25 μin, with non-reddish pure gold surface.
Maxipcb focuses on high-quality thin ENIG gold PCB manufacturing to balance cost and performance.

Standard ENIG Process Flow

Pretreatment (brushing / sandblasting)

→ Acid Degreasing

→ Double-Stage Water Rinsing

→ Micro-etching (Sodium Persulfate System)

→ Double-Stage Water Rinsing

→ Sulfuric Acid Pre-immersion

→ Palladium Catalyst Activation

→ Ultrapure Water Cleaning

→ Acid Pickling

→ Pure Water Rinsing

→ Electroless Nickel Plating (Ni/P Alloy)

→ DI Water Rinsing

→ Immersion Gold Deposition

→ Pure Water Rinsing

→ Hot Ultrapure Water Cleaning

→ Drying

Core Process Control Key Points

1. Acid Degreasing Tank

Special acidic degreasing agents are used to remove residual surface oil and copper oxide, improving substrate wettability and ensuring uniform bonding of subsequent nickel layers.

2. Micro-etching Tank

Adopts mixed solution of sodium persulfate and sulfuric acid: sodium persulfate 80~120 g/L, sulfuric acid 20~30 ml/L.

Micro-etching removes surface oxide and process residues to expose fresh copper, enhancing nickel layer adhesion. The controlled etching depth is 0.5~1.0 μm. A certain proportion of old solution is retained to stabilize copper ion concentration and ensure consistent etching effect.

3. Pre-immersion Tank

Matched sulfuric acid solution is used to maintain the same acidity as the activation tank, avoiding cross-contamination and protecting the activity of palladium catalyst.

4. Activation Tank

Palladium forms a nano-scale catalytic film on the copper surface via displacement reaction, providing crystal nuclei for self-catalytic nickel deposition. Partial coverage design optimizes cost and avoids risks such as nickel penetration and peeling. Regular nitric acid cleaning is required to eliminate gray-black sediment on tank walls.

5. Electroless Nickel Tank

Relying on palladium catalytic reaction, nickel-phosphorus alloy is evenly deposited on exposed copper areas. Conventional nickel thickness: 100~250 μin, controlled deposition rate: 6~8 μin/min. Regular tank cleaning and liquid replacement are required to prevent solution aging and sediment accumulation.

6. Immersion Gold Tank

Gold coating is formed by chemical displacement reaction. The reaction reaches saturation in 30 minutes, with gold thickness controlled at 0.025~0.1 μm and deposition rate at 0.25~0.45 μm/min. The gold liquid concentration is maintained at 0.5~2.0 g/L. Gold thickness can be adjusted by optimizing temperature, soaking time and liquid concentration to meet customized requirements.

ENIG Production Operation Precautions

For high-density flexible circuits with line spacing less than 0.1 mm, activation time is controlled at 60~90 seconds and Pd²⁺ concentration at 10~15 PPM to prevent missing plating and incomplete coating.
Standard activation effect presents uniform off-white copper surface; over-activation causes blackening, while insufficient activation leads to exposed copper defects.
Anode protection voltage is stably controlled at 0.8~1.2 V; the nickel bath production load is limited to 0.3~0.8 dm²/L to avoid solution decomposition and rough coating.
Reasonably configure circulating filtration and air agitation; perform regular tank dragging and liquid maintenance after shutdown to stabilize bath activity.
Strictly control phosphite content in the nickel tank (＜120 g/L). Excessive concentration will cause nickel layer graying and reaction stagnation.
After gold plating, boards must be dried within 30 minutes with isolation protection and anti-static operation to prevent gold oxidation induced by acid mist and moisture.
Heavy metal ion contamination shall be strictly controlled: Ni²⁺ in gold bath ≤ 500 ppm and Cu²⁺ ≤ 20 ppm, to avoid coating discoloration, poor adhesion and solution failure.

Defect Analysis & Process Optimization

Common ENIG abnormal issues such as dark gold surface, nickel missing, whitening, layer cracking and corrosion are mainly caused by bath aging, impurity accumulation, parameter drift and non-standard operation.

Scientific tank maintenance, precise reagent ratio, real-time parameter monitoring and standardized operating procedures can effectively reduce defective rate, stabilize long-term production quality, cut waste cost and improve overall production efficiency for ENIG circuit boards.

FAQ

What customization options are available for ENIG Immersion Gold PCBs?
We offer tailored solutions for your custom PCB needs, including layer count, copper thickness, and finished thickness ranging from 0.6–2.0 mm. Our expertise ensures optimal solderability and corrosion resistance using ENIG surface treatment for various industrial applications.

Can you manufacture multilayer PCBs with ENIG surface finish?
Yes, we specialize in multilayer PCB fabrication with ENIG immersion gold finish to provide flat, solderable surfaces. Our production process supports high-density multilayer boards, ensuring consistent quality and performance for complex electronic assemblies.

What quality standards do you follow for your PCBs?
Our PCB products comply with IPC standards and certifications such as ISO9001, UL, and RoHS. We maintain strict process controls and real-time monitoring throughout manufacturing to guarantee that each printed circuit board meets customer specifications and industry benchmarks.

How do you handle delivery and after-sales support for PCB board orders?
We coordinate global logistics to ensure timely delivery of your PCB board orders. Our technical team remains available post-delivery to assist with installation guidance and address any production-related inquiries, aiming for long-term trust and product reliability.

Model: Enig Immersion Gold PCB

Material: TG130-TG180 FR-4

Layer: 2-Layer-Multilayer

Color: Green/Blue/White

Finished Thickness: 0.6-2.0mm

Copper Thickness: 0.5-3OZ

Surface Treatment: Immersion Gold, Enig

Min Trace: 4mil(0.1mm)

Min Space: 4mil(0.1mm)

Application: Various electronic products

Enig Immersion Gold PCB

Description

Data Sheet