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68 PCB007 MAGAZINE I FEBRUARY 2020 Article by Matt Kreiner HITACHI HIGH-TECH One of the main challenges in PCB manu- facturing is to create a stable, long-term coat- ing of the copper surface to perform critical functions throughout the expected lifetime of the part. The surface coating is there to do two things: prevent the copper from oxi- dizing by coming in contact with the air, and form a reliable contact for a soldered joint or wire-bonded connector. Following IPC specifi- cations IPC-4552A, IPC-4553A, IPC-4554, and IPC-4556 will improve reliability and longev- ity. X-ray fluorescence (XRF) is a proven meth- od—and, for this reason, has been written into these four specifications—to control processes for plating thickness of substrates to address oxidation and solderability. XRF: An Essential Tool to Help PCB Manufacturers Meet IPC Specifications IPC and ENIG Specification: IPC-4552A The electroless nickel/immersion gold (ENIG) deposit is one of the most widespread surface finishes used in printed board manufacturing today. IPC released its first specification for ENIG in 2002, followed by revision A in August 2017. ENIG is an excellent surface finish for re- liable solder joints and aluminum wire bonds and has a relatively long shelf-life; however, its high performance depends on the quality of nickel and gold layers. The thin outer layer of immersion gold is very stable and prevents oxidation of the underlying nickel for the life of a component. The 2017 revision helps manufacturers to create a more reproducible and reliable ENIG surface finish and outlines printed board perfor- mance requirements, including the J-STD-003 solderability specification. The revision focuses Figure 1: XRF helps you conform to IPC specifications.

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