How Much Gold Is Used in ENIG PCB in PCB Manufacturing?

Many customers believe that ENIG PCB is expensive because it uses a large amount of gold.

But is that really true?

In PCB manufacturing, the actual amount of gold used in an ENIG (Electroless Nickel Immersion Gold) surface finish is usually much less than most people expect.

The higher cost of ENIG PCB does not mainly come from gold material itself. The cost is related to the complete chemical process, including nickel plating, immersion gold deposition, chemical control, wastewater treatment, and quality management.

This article explains how much gold is actually used on a PCB and why ENIG remains a higher-cost surface finish compared with HASL or OSP.

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Understanding ENIG Surface Finish

ENIG is a two-layer surface finish consisting of:

1. Electroless Nickel Layer
2. Immersion Gold Layer

The nickel layer acts as a barrier between copper and gold, while the thin gold layer protects the nickel surface from oxidation and provides excellent solderability.

Typical ENIG thickness:

The gold layer is extremely thin.

Unlike hard gold plating, ENIG does not deposit a thick gold layer for wear resistance.

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How Much Gold Is Used on 1m² ENIG PCB?

To estimate gold consumption, we need several assumptions.

Calculation Assumptions

PCB area:

1 m²

Gold coverage ratio:

20%

(Most PCB surfaces are not completely covered with gold. Only exposed pads, fingers, and contact areas receive gold.)

Gold thickness:

• 1U” ENIG = 0.0254 μm
• 2U” ENIG = 0.0508 μm

Gold density:

19.32 g/cm³

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Simplified Formula

Gold Weight =

PCB Area × Gold Coverage Ratio × Gold Thickness × Gold Density

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Example 1: 1U” ENIG

PCB area:

1 m² = 10,000 cm²

Gold coverage:

20%

Effective gold area:

10,000 × 20%

= 2,000 cm²

Gold thickness:

0.0254 μm

= 0.00000254 cm

Calculation:

2,000 × 0.00000254 × 19.32

≈ 0.098 g gold

Therefore:

1m² PCB with 1U” ENIG uses approximately 0.1g gold

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Example 2: 2U” ENIG

Gold thickness:

0.0508 μm

Calculation:

2,000 × 0.00000508 × 19.32

≈ 0.196 g gold

Therefore:

1m² PCB with 2U” ENIG uses approximately 0.2g gold

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Gold Material Cost in ENIG PCB

Assuming gold price:

917 RMB/g

(Example market price)

1U” ENIG:

Gold weight:

0.098g

Gold material cost:

0.098 × 917

≈ 90 RMB

≈ USD 12–13

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2U” ENIG:

Gold weight:

0.196g

Gold material cost:

0.196 × 917

≈ 180 RMB

≈ USD 25

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Why Is ENIG PCB More Expensive?

Many people are surprised by this result.

If only the gold material is considered, the cost is not extremely high from PCB supplier.

The real ENIG cost comes from the complete manufacturing process.

Major cost factors include:

1. Electroless Nickel Plating

Nickel deposition requires:

• Chemical control
• Bath maintenance
• Thickness monitoring
• Process management

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2. Immersion Gold Process

The gold layer is deposited through a controlled chemical replacement reaction.

Process stability affects:

• Gold thickness
• Solderability
• Surface reliability

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3. Chemical Consumption

ENIG requires various chemicals, including:

• Nickel chemicals
• Gold salts
• Cleaning chemicals
• Process additives

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4. Wastewater Treatment

PCB chemical processes require strict environmental control.

Waste treatment and compliance management are also part of the manufacturing cost.

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ENIG Gold Thickness Does Not Mean More Gold Is Always Better

A common misunderstanding is:

Thicker gold always means better PCB performance.

This is not always true.

The correct gold thickness depends on the application.

For example:

Standard SMT / BGA applications

Usually:

• 1U”–2U” ENIG

is sufficient.

High reliability applications

May require:

• controlled nickel thickness
• controlled gold thickness
• additional reliability requirements

The best surface finish is the one that matches the application requirement.

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ENIG vs Other PCB Surface Finishes: Cost Perspective

The above is a relative process cost index, not the total PCB price.

Actual cost depends on:

• PCB size
• gold area
• gold thickness
• production quantity
• process requirements

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Key Takeaway

A 1m² ENIG PCB usually contains:

• Around 0.1g gold for 1U” ENIG
• Around 0.2g gold for 2U” ENIG

The reason ENIG is more expensive is not simply because it uses a lot of gold.

The real cost comes from:

• precision chemical processes
• nickel plating
• immersion gold control
• quality inspection
• environmental requirements

Understanding the real cost structure helps engineers and purchasing teams choose the right PCB surface finish instead of simply selecting the most expensive option.

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FAQ

How much gold is used in ENIG PCB?

Typically around 0.1–0.2 grams of gold per square meter PCB, depending on gold thickness and exposed area.

Is ENIG more expensive because of gold?

Not mainly. The major cost comes from the complete ENIG chemical process and quality control.

Is thicker ENIG gold always better?

No. Gold thickness should match the application requirements. Excessive gold thickness may increase cost without improving performance.

ENIG vs HASL, which one is better?

ENIG provides better flatness and is suitable for fine-pitch components such as BGA. HASL is more economical for many standard applications.