_top_ - Ipc-4556 Pdf
is the industry standard specification for Electroless Nickel/Electroless Palladium/Immersion Gold (ENEPIG)
Gold Embrittlement in Vibration
An automotive supplier requested "thick gold" for durability, thinking more is better. The fabricator applied 0.25 µm of gold. During thermal cycling and vibration testing, the solder joints cracked due to gold embrittlement (formation of AuSn4 intermetallics). IPC-4556 caps gold at 0.125 µm to avoid this. ipc-4556 pdf
You can find the official document and its revisions through these sources: Thickness: 0
What is IPC-4556?
IPC-4556 is titled "Specification for Electroless Nickel/Immersion Gold (ENIG) Plating for Printed Circuit Boards." It was developed by the IPC (Association Connecting Electronics Industries) to provide a complete set of process control, performance, and inspection criteria for ENIG finishes. The IPC-4556 PDF is intended for: It was
2. Immersion Gold Layer (The Protector)
- Thickness: 0.05 – 0.125 µm (2 – 5 µin). Note: This is extremely thin. Gold is not the solderable surface; it dissolves into the solder joint to protect the nickel.
- Too Thin (< 0.05 µm): Porous nickel leads to oxidation.
- Too Thick (> 0.125 µm): Brittle joints (Gold Embrittlement). This is a common mistake beginner designers make—thicker gold is NOT better for soldering.
The IPC-4556 PDF is intended for:
It was developed by the IPC Electroless Nickel/Immersion Gold (ENIG) Task Group (7-11d) under the IPC Printed Board Processes Subcommittee. The standard is part of IPC’s series of surface finish specifications, which include IPC-4552 (ENIG for PCBs) — IPC-4556 is actually the latest revision that replaced and updated the older IPC-4552.
Here are the authorized ways to obtain the standard:
4. Solderability
- Must pass the wetting balance test per IPC-J-STD-003
- After multiple reflow cycles (simulating assembly), the surface must remain solderable