Typically 3.0 μm to 6.0 μm (118 μin to 236 μin).
Evaluation of the use of ENEPIG in small solder joints - ResearchGate
Access to the official IPC-4556 PDF standard is critical for several stakeholders in the electronics ecosystem:
IPC-4556: Specification for ENEPIG Plating on PCBs (officially IPC-4556: Specification for Electroless Nickel/Electroless Palladium/Immersion Gold (ENEPIG) Plating for Printed Circuit Boards ) is the definitive industry standard for applying ENEPIG surface finishes. Developed by the IPC Plating Subcommittee (4-14) and amended in 2015, this standard provides strict requirements for ENEPIG layer thicknesses, quality assurance, solderability, and wire bonding performance.
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While the base standard was released in 2013, it has undergone updates.
| Feature | IPC-4552 (ENIG) | IPC-4556 (ENEPIG) | | :--- | :--- | :--- | | | Electroless Nickel / Immersion Gold (2 layers) | EN + EP + IG (3 layers) | | Wire Bonding | Primarily Aluminum wire bonding | Gold, Aluminum, and Copper wire bonding | | Key Weakness | Susceptible to "black pad" corrosion after soldering | Palladium layer prevents hyper-corrosion, offering higher reliability | | Gold Thickness | Minimum of 0.05 µm (with a maximum added in rev. A) | Tighter range: 0.03 - 0.07 µm |
The standard specifies the required thickness for each layer of the ENEPIG finish, which is critical for ensuring both performance and cost-effectiveness: