Electroless Nickel Immersion Gold (ENIG) is a very thin amount of Gold applied over Nickel. The nickel is plated onto the copper prior to the application of Gold and acts as a barrier to prevent the Gold and the Copper from migrating into one another. The gold will disappear when soldered, as it is absorbed in the process. Excellent for very fine pitched components. In PCB manufacturing, ENIG is most widely applied in high-end PCBs, like HDI boards, flex circuits, rigid-flex boards, multilayer boards, embedded passive PCBs and etc.
