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| Standard | Finish | Best For | vs. ENIG (IPC-4556) | | :--- | :--- | :--- | :--- | | IPC-4552 | ENEPIG | Gold wire bonding, long shelf life | More expensive, adds palladium layer. | | IPC-4554 | Immersion Silver | Low-cost, RF designs | Poorer shelf life, tarnishes. | | IPC-4555 | Immersion Tin | Press-fit connectors | Limited to single reflow. |
The choice between these finishes depends heavily on the application: is a general-purpose finish for soldering; ENEPIG is the versatile choice for mixed assemblies requiring soldering and wire bonding; and Hard Gold is the mandatory choice for edge connectors designed for frequent mating cycles. ipc4556 pdf
The document outlines visual inspection criteria, allowing for minor, non-functional cosmetic variations while restricting defects that affect reliability. IPC-4556A Revision: What's New?
The IPC-4556 PDF document is a valuable resource for: Authorized resellers of IPC documents
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(1.2 µin). The gold layer protects the palladium from contamination and maintains solderability. | | IPC-4554 | Immersion Silver | Low-cost,
The technical core of IPC-4556 is its stringent deposit thickness requirements:
Acts as a diffusion barrier preventing copper migration into the solder. 0.05 to 0.15 2.0 to 12.0
The IPC-4556 PDF offers numerous benefits to manufacturers, assemblers, and quality control specialists, including:
The IPC-4556 standard explicitly mandates that layer thickness be measured using X-Ray Fluorescence (XRF) methodology . During the standard's development, IPC used XRF extensively, establishing a detailed set of measurement criteria. XRF is the only IPC-approved non-destructive technique for this purpose. Key considerations for accurate XRF measurement include: