, "Specification for Electroless Nickel/Electroless Palladium/Immersion Gold (ENEPIG) Plating for Printed Circuit Boards," is the definitive industry standard for the ENEPIG surface finish. Released in 2013 and subsequently updated to the IPC-4556A revision , this document defines the quality requirements, deposit thicknesses, and testing protocols for ENEPIG-finished PCBs.
"A free PDF is fine because the spec hasn't changed in years." Fact: Without the latest revision, you might miss critical updates (e.g., Rev A added gold thickness upper limits to prevent embrittlement).
Use the standard’s recommended for incoming inspection:
The standard defines precise thickness ranges to ensure reliability. Typical specifications from 3.0 to 6.0 µm [118.1 to 236.2 µin] Palladium: 0.05 to 0.15 µm [2.0 to 12.0 µin] 0.030 to 0.070 µm [1.2 to 2.8 µin] Strategic Advantages of the ENEPIG Finish ipc4556 pdf
The brilliance of the ENEPIG finish lies in its three distinct layers, each governed by strict thickness requirements under IPC-4556 to prevent failures like hyper-corrosion:
Understanding which version of the standard you are referencing in an IPC-4556 PDF is essential for legal and manufacturing compliance. The Original Specification (2013) & Amendment 1 (2016)
Heavy copper layers are heavy. This creates unique issues during the lamination process (pressing layers together with epoxy/prepreg). The standard outlines the peel strength requirements to ensure the heavy copper tracks do not lift off the substrate under thermal stress. This creates unique issues during the lamination process
, this performance specification sets the definitive requirements for ENEPIG, a "universal" surface finish that addresses the diverse needs of modern electronic assemblies, including soldering, wire bonding, and electrical contact performance. Technical Composition and Requirements According to the IPC-4556 specification
Navigate to the IPC's online store. Search for "IPC-4556" or "ENEPIG". The product page for the Standard Only version includes details on abstract, date (January 2013), and price.
Defines the force and pull-test requirements for both aluminum (Al) and gold (Au) wire bonds. ENEPIG must demonstrate clean, strong bonds without brittle failures. date (January 2013)
A key part of many IPC-4556 PDF searches is comparing it with other finishes to determine the best choice for a project.
The core of IPC-4556 defines the precise thickness ranges for the three metal layers. These measurements are typically verified using X-ray fluorescence (XRF) on a standard 1.5 mm x 1.5 mm pad. IPC-4556 Specified Thickness
Guarantees a minimum of 12 months solderability (IPC-J-STD-003 Category 3) under proper storage conditions.