Pdf !free! — Ipc4556
Adherence to IPC-4556 helps PCB manufacturers deliver products that meet the under controlled storage conditions. The palladium layer is critical to achieving this reliability: it must be thick enough to impede nickel diffusion to the gold surface, helping to prevent hyper‑corrosion of the electroless nickel deposit, which results in unreliable solder joints. However, if the palladium layer is too thick, the solder joint can become brittle and may eventually fail.
is an industry specification titled "Performance Specification for Thick-Film Copper (Cu) Plating for High-Performance Applications." It was developed by IPC (Association Connecting Electronics Industries) to standardize the requirements for thick copper plating on PCBs, particularly for high-reliability sectors like aerospace, defense, medical devices, and high-power electronics.
The standard defines the acceptable thickness, adhesion, porosity, and thermal reliability of plated copper used as a surface finish. Unlike standard electrolytic copper, "thick-film" copper under IPC-4556 typically ranges from or more, depending on the application class. ipc4556 pdf
Barrier against copper diffusion; provides mechanical support for holes. (118.1 – 236.2 µin) Electroless Palladium (Pd)
The document serves as a guideline for fabricators, suppliers, and OEMs (Original Equipment Manufacturers). It dictates the thickness requirements, physical properties, and acceptance criteria for ENIPIG finishes, ensuring that the plating quality meets the rigorous demands of assembly processes like wire bonding and soldering. and copper (Cu) wire bonds.
High-power COB (Chip-on-Board) LEDs require thick copper for heat spreading. IPC-4556 defines copper thickness that doubles as a thermal diffuser.
The complete ENEPIG deposit involves three unique chemical layers plated sequentially over a clean copper substrate. IPC-4556 sets the mandatory thickness ranges for each element to balance manufacturing yield, process control, and joint longevity: Plating Layer IPC-4556 Thickness Range (Metric) IPC-4556 Thickness Range (Imperial) Primary Engineering Purpose 3.0 to 6.0 118.1 to 236.2 Barrier against copper diffusion
To conform to IPC-4556, manufacturers must employ precise testing methods. is the industry-standard tool for verifying that the nickel, palladium, and gold layers fall within the specified thickness ranges. Beyond thickness, the specification also covers: Visual references for surface quality. Adhesion and Solderability testing. Cleanliness and electrolytic corrosion standards. Conclusion
By introducing the palladium layer, ENEPIG effectively eliminates the hyper-corrosion of the nickel layer that frequently plagues ENIG finishes. Multifunctional Assembly: It is uniquely capable of supporting gold, aluminum, and copper wire bonding
: Supports gold (Au), aluminum (Al), and copper (Cu) wire bonds.
