Because the device is inside the board, the board itself acts as the device package. IPC-4556 requires tests for flexural strength and vibration. If the PCB bends, the rigid silicon die inside creates a stress concentration point. The standard defines acceptable warpage limits and bend radii to prevent die cracking.
For engineers, procurement teams, and quality assurance personnel, possessing the official document is essential for daily compliance and technical auditing. How to Obtain an Official Copy
The current active version is , which supersedes IPC-4552 (2002) and its amendments.
Developed by the Plating Processes Subcommittee (4-14) of the IPC Fabrication Processes Committee (4-10) and, as of 2025, in its Revision A phase, this document establishes the performance, quality, and thickness requirements. Why ENEPIG Matters (The Scope of IPC-4556) ipc-4556 pdf
The revision introduced several critical updates to address modern manufacturing challenges:
Note: The and Revision A introduced an absolute maximum for the gold layer ( 0.0700.070
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. Because the device is inside the board, the
ENEPIG is a tertiary or multi-layered metallic surface coating deposited over exposed copper PCB traces. Unlike simpler surface finishes like Organic Solderability Preservatives (OSP) or Electroless Nickel Immersion Gold (ENIG), ENEPIG introduces a thin barrier layer of palladium between the underlying nickel and top gold layer.
is the industry standard developed by the Plating Processes Subcommittee (4-14) of the IPC that defines the requirements for ENEPIG surface plating 1.2.1. Released in January 2013 and subsequently updated, this specification addresses the growing need for a versatile surface finish that supports multiple soldering and wire bonding technologies 1.2.3. ENEPIG consists of three layers:
: Compatible with heavy-gauge aluminum wire. The standard defines acceptable warpage limits and bend
The IPC-4556 PDF is an essential document for electronics manufacturers, particularly those involved in surface mount technology (SMT) assembly. By following the guidelines and requirements outlined in the standard, manufacturers can:
What is the for your board (e.g., SMT reflow, gold wire bonding, or aluminum wire bonding)?
The palladium layer acts as a barrier, preventing the immersion gold chemistry from aggressively attacking and oxidizing the underlying nickel.