ENIG

The ENIG (Electroless Nickel Immersion Gold) finish has historically been the best fine-pitch (flat) surface and lead-free option worldwide. ENIG is a two-step process that layers a thin coating of gold over a thin coating of nickel. The nickel serves as a barrier to the copper and is the surface to which the components are actually soldered to while the gold protects the nickel during storage. Despite the fact that this coating process yields a long shelf life and is good for plated through holes, it is a complicated and an expensive process (remember that it’s a two-step process) that is not re-workable and is known to cause signal loss in RF circuits.