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PCB Fabrication & Surface Finishing

ENIG & ENEPIG PCB Surface Finishing Prepress Calculator

Calculate electroless nickel deposition rates, immersion gold displacement thicknesses, solder mask expansion opening offsets, and black pad hyper-corrosion risk indices for high-reliability HDI printed circuit boards.

Process Parameters & Inputs

Electroless nickel layer thickness in micrometers (µm) (IPC-4552 specifies 3.0–6.0 µm).
Immersion gold thickness in micrometers (µm) (IPC-4552B specifies 0.05–0.10 µm).
Fine-pitch BGA or QFN pad pitch in mm.
LDI solder mask exposure alignment capability in micrometers (µm).
Plating tank operating temperature in °C.

Calculated Engineering Metrics

Nickel Tank Dwell Time
22.5min
Gold Displacement Dwell
8.2min
Mask Clearance Expansion
55µm
Black Pad Corrosion Index
0.42(Safe)

Toolpath & Geometry Simulation

Engineering Reference:
→ Read the ENIG & ENEPIG PCB Surface Finishing Prepress Gerber/DXF Vector Guide

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Engineering Principles & Formula Reference

Electroless Nickel Immersion Gold (ENIG) deposits an autocatalytic nickel-phosphorus barrier ($7-10\text{ wt}\% \text{ P}$) followed by galvanic immersion gold ($Au^+ + e^- \rightarrow Au^0$) where nickel atoms are oxidized to provide electrons.

Deposition Rates & Solder Mask Expansion:
R_{Ni} = R_0 \cdot \exp\left(-\frac{E_a}{R T_{bath}}\right) \cdot [H_2PO_2^-]
t_{Au} = K_{galvanic} \cdot \sqrt{t_{immersion}}
\Delta W_{mask} = \Delta W_{reg} + 1.25 \cdot t_{Ni} + 12\text{ µm}
HCI = \frac{[P_{bath}] \cdot t_{Au}}{[Ni^{2+}]_{active} \cdot t_{Ni}} \le 1.0

Excessive immersion gold dwell causes hyper-corrosion of the nickel grain boundaries (Black Pad defect), leading to brittle solder joint fractures during BGA thermal cycling.