Ipc4556 Pdf 2021 Page

Suitable for use in membrane switches and steel dome contact applications. Go to product viewer dialog for this item. IPC-4556 - Amendment 1

IPC-4556 specifies X-ray Fluorescence (XRF) as the primary method for verifying thickness. It mandates the use of Solid State Detectors (SSD) for better resolution on tri-level coatings and requires calibration against national standards.

ENEPIG was developed largely to solve the "black pad" corrosion issues sometimes found in ENIG (Electroless Nickel / Immersion Gold) finishes. The palladium layer acts as a buffer, preventing the immersion gold reaction from attacking the underlying nickel. ipc4556 pdf

is the primary industry standard defining requirements for Electroless Nickel / Electroless Palladium / Immersion Gold (ENEPIG) plating on printed circuit boards (PCBs). Often called the "universal finish," ENEPIG is unique because it supports multiple assembly processes—including soldering and various types of wire bonding—on a single surface. Core Layer Requirements

Excellent wetting for both lead-free (SAC305) and leaded (Sn63Pb37) alloys. Suitable for use in membrane switches and steel

High pull strengths for gold, aluminum, and even copper wire bonding.

According to the standard, boards with an ENEPIG finish must maintain a minimum shelf life of 12 months under proper storage conditions, adhering to IPC-J-STD-003 Category 3. Versatility in Assembly It mandates the use of Solid State Detectors

This critical update added a maximum gold thickness of 0.070 µm. This limit prevents "hyper-corrosion" of the nickel, which can occur if the gold plating process is too aggressive or prolonged.

A major advantage of following IPC-4556 is that it ensures the surface is compatible with diverse attachment technologies:

IPC-4556 establishes precise thickness ranges for each of the three metal layers. These specifications are designed to balance reliability, solderability, and cost. Plating Layer Thickness Range (µm) Thickness Range (µin) Primary Function 3.0 – 6.0 118.1 – 236.2 Diffusion barrier and structural support Electroless Palladium 0.05 – 0.15 2.0 – 12.0 Protects nickel from corrosion; enables wire bonding Immersion Gold 0.030 – 0.070 1.2 – 2.8 Prevents oxidation; maintains solderability Key Provisions and Amendments