In answer to numerous industry requests for guidance on electroless nickel/immersion gold (ENIG), IPC-4552 was developed. Containing full color photographs, this specification sets the requirements for the use of ENIG as a surface finish for printed boards. It includes requirements for ENIG deposit thicknesses based on performance criteria. It is an invaluable resource for use by suppliers, board fabricators, electronics manufacturing service (EMS) providers and original equipment manufacturers (OEMs). The specification's Appendix also includes a FREE copy of the highly sought-after technical paper, “Standard Developments Efforts of Electroless Nickel Immersion Gold,” by George Milad and Gerard O’Brien. The ENIG board surface finish is an electroless nickel layer capped with a thin layer of immersion gold. The immersion gold protects the underlying nickel from oxidation or passivation over its intended life. It is a multifunctional surface finish, applicable to soldering, aluminum wire bonding, press fit connections, and as a contact surface. The addition of Amendments 1 & 2 to this document provides for the use of thinner immersion gold, down to 0.04 microns (1.58 microinches), than was previously allowed at 0.05 microns (1.97 microinches). However, such thinner gold can only be utilized when the electrical connection is to be made via soldering. Also, the rules by which rework and/or repair of a printed board's ENIG surface finish are now defined. 33 pages. Released December 2012.