ENIG (Electroless Nickel Immersion Gold), also known as “nickel-gold plating” or “immersion gold PCB,” is a critical surface finishing process for printed circuit boards (PCBs). Widely adopted in high-end electronics—including smartphones, BGA carriers, and COB (Chip-On-Board) modules—ENIG combines excellent solderability, corrosion resistance, and wire bonding capability, making it a go-to choice for precision electronics. In this guide, we dive deep into ENIG’s technology, process flow, pros/cons, and why Jerico Multilayer PCB supplier stands out as a trusted partner for ENIG manufacturing.

ENIG PCB Surface Treatment

​What is ENIG? A Deep Dive into the Technology​

ENIG is a two-layer metal coating (nickel + gold) applied to copper pads via chemical plating, eliminating the need for electrolytic current. Unlike electroplated nickel-gold, ENIG skips wire bonding for each pad, simplifying production and reducing costs by up to 30%. Its core structure includes:

• ​Nickel (Ni/P) Layer: Acts as a diffusion barrier between copper and gold, preventing intermetallic compound (IMC) formation during soldering.
• ​Gold (Au) Layer: Protects nickel from oxidation and ensures reliable solder joints, even after multiple reflows.

​ENIG Process Flow: Precision at Every Step​

The ENIG process involves 10+ steps, each critical to ensuring coating uniformity and performance:

1. ​Pre-Treatment: Mechanical cleaning (brushing/sanding) and micro-etching remove copper oxide and surface defects, creating a rough profile for better adhesion.
2. ​Activation: Palladium (Pd) catalyst is applied to initiate nickel plating—copper’s higher reactivity reduces Pd ions to metallic Pd, forming a seed layer.
3. ​Chemical Nickel Plating: Nickel-phosphorus (Ni/P) alloy deposits uniformly, with phosphorus content (8-12%) optimizing hardness and solderability.
4. ​Immersion Gold: Gold replaces nickel atoms on the surface, forming a thin (0.05-0.1μm) protective layer—thicker gold (for COB) requires specialized processes.

Pro Tip: Over-etching during micro-etching can create deep grooves, risking gold layer penetration and “black pad” defects. Jerico Multilayer PCB uses automated micro-etching controls to minimize this risk.

​ENIG Advantages: Why It’s a High-Reliability Choice​

• ​Solder Joint Strength: Withstands 3+ reflows (260°C) without degradation, ideal for BGA and QFN packages.
• ​Wire Bonding Ready: The nickel layer’s smooth surface supports aluminum/gold wire bonding in COB applications.
• ​Corrosion Resistance: Gold’s inertness protects against oxidation, extending shelf life to 12+ months (under proper storage).
• ​Fine-Pitch Compatibility: Flat surface ensures uniform solder paste printing, critical for 01005 components and high-density interconnects (HDI).

Industry Case: Jerico Multilayer PCB’s ENIG boards are used in 5G smartphones, where 0.4mm-pitch BGA components require zero solder joint failures—ENIG’s precision delivers.

​ENIG Challenges & Solutions​

Despite its benefits, ENIG faces two key issues:

​1. Black Pad Syndrome​

Caused by excessive nickel oxidation during gold immersion, black pads weaken solder joints. Solution:

• Control gold layer thickness (0.05-0.1μm for most applications).
• Use ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold) for high-reliability needs (e.g., automotive electronics), though it’s costlier.

​2. Higher Cost Than OSP​

Gold’s price volatility makes ENIG pricier than organic solderability preservatives (OSP). Mitigation:

• Optimize gold thickness—thinner layers (0.05μm) suffice for most consumer electronics.
• Partner with manufacturers like Jerico Multilayer PCB, which leverages economies of scale to reduce costs by 15-20%.

​Why Choose Jerico Multilayer PCB for ENIG?​​

Jerico Multilayer PCB is a global leader in ENIG manufacturing, offering:

• ​Advanced Process Control: Automated line monitoring ensures nickel/gold uniformity (±5% thickness variation).
• ​Defect Prevention: Proprietary micro-etching and activation technologies reduce black pad rates to <0.1%.
• ​Custom Solutions: Supports ENIG for 1-20+multy layers PCBs, with flexible gold thickness options (0.05-0.3μm).

​ENIG FAQ: Your Top Questions Answered​

​Q1: Is ENIG suitable for high-temperature applications?​​
A: Yes. ENIG withstands up to 280°C for short periods (e.g., wave soldering) and 3+ reflows at 260°C, making it ideal for automotive and industrial electronics.

​Q2: How does ENIG compare to OSP in cost?​​
A: ENIG is 2-3x pricier than OSP due to gold usage, but its reworkability and reliability justify the cost for mission-critical applications.

​Q3: Can ENIG boards be reworked?​​
A: Yes. ENIG supports soldering/desoldering up to 3 times without significant coating degradation—critical for prototype iterations.

​Q4: What’s the ideal gold thickness for BGA pads?​​
A: 0.05-0.1μm balances cost and reliability. For COB or high-vibration environments, increase to 0.15-0.3μm.

​Q5: How long does ENIG last in storage?​​
A: Properly stored (dry, <25°C, <60% RH), ENIG boards remain solderable for 12+ months. Jerico Multilayer PCB provides 6-month shelf-life guarantees with proper packaging.

​Conclusion​

ENIG remains a cornerstone of high-reliability PCB manufacturing, offering unmatched solderability and corrosion resistance. By partnering with Jerico Multilayer PCB—experts in ENIG process optimization—you can mitigate common defects (e.g., black pads) and deliver boards that meet the demands of 5G, AIoT, and automotive electronics.