A minimum of 0.030 μm [1.2 μin]. Modern amendments often cap gold at 0.07 μm [~2.8 μin] to prevent issues with solder joint reliability.
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Many websites offer free PDF downloads of this standard. Most of these are either obsolete revisions (Revision A from 2003), incomplete drafts, or illegal copies. Using an outdated standard can lead to manufacturing defects. ipc-4556 pdf
The IPC (Association Connecting Electronics Industries) is the global trade association that establishes standardized requirements for the manufacture of electronic equipment and assemblies. When ENEPIG emerged as a viable commercial finish, the IPC Plating Processes Subcommittee formed a dedicated task group to establish a reliable, repeatable metric for its application. The result was the publication of IPC-4556. This document does not merely dictate thickness requirements; it provides a comprehensive framework for process control, quality assurance, and failure analysis. A minimum of 0