The standard (with its latest amendments) defines specific plating thickness ranges for the three layers: Nickel (Ni): 3 to 6 μm [118.1 to 236.2 μin]. Palladium (Pd): 0.05 to 0.15 μm [2 to 6 μin]. Gold (Au):
IPC-4556 specifies that the electroless nickel layer must have a phosphorus content of 8–10 weight percent (mid-to-high phosphorous) to enhance corrosion resistance without becoming too brittle. 3. Inspection and Performance Testing
Environmental and reliability guidelines to prevent defects like "black pad." Why ENEPIG? The Need for IPC-4556 ipc-4556 pdf
The IPC-4556 specification outlines a precise four-layer metallic stack-up over the copper board trace: The underlying PCB conductive trace.
Many novices use the rigid PCB standard for flexible circuits. IPC-4556 refers to IPC-6013 for flex, which requires lower internal stresses in the nickel. Do not use a standard rigid ENIG stack-up on a flex board—it will crack. The standard (with its latest amendments) defines specific
ENEPIG is a superior choice for designs requiring , especially with fine-pitch components and aluminum wire bonding. In contrast, ENIG remains a cost-effective workhorse for general soldering and standard PCB assembly.
The standard applies to PCBs intended for , including aerospace, medical, automotive, telecommunications, and industrial controls. Many novices use the rigid PCB standard for
Just because a manufacturer says "We meet IPC-4556" does not guarantee no black pad. You must audit their bath chemistry logs to verify . The standard requires the nickel to be consistent across the whole panel.