ENIG
Encyclopedia
Electroless nickel immersion gold (ENIG) is a type of surface plating used for printed circuit board
s. It consists of an electroless nickel plating
covered with a thin layer of immersion gold, which protects the nickel from oxidation.
ENIG has several advantages over more conventional (and cheaper) surface platings such as HASL
(solder), including excellent surface planarity (particularly helpful for PCB's with large BGA
packages), good oxidation resistance, and usability for untreated contact surfaces such as membrane switch
es and contact points.
Early ENIG processes suffered from reliability issues which caused the ENIG finish to separate from the copper pads, taking the parts with them. ENIG also does not wet as evenly or easily as HASL.
IPC
Standard IPC-4552 covers the quality and other aspects of ENIG finish on printed circuit boards.
Printed circuit board
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...
s. It consists of an electroless nickel plating
Electroless nickel plating
Electroless nickel plating is an auto-catalytic chemical technique used to deposit a layer of nickel-phosphorus or nickel-boron alloy on a solid workpiece, such as metal or plastic. The process relies on the presence of a reducing agent, for example hydrated sodium hypophosphite which reacts with...
covered with a thin layer of immersion gold, which protects the nickel from oxidation.
ENIG has several advantages over more conventional (and cheaper) surface platings such as HASL
HASL
HASL or Hot Air Solder Leveling is a type of finish used on printed circuit boards .- Description :The PCB is typically dipped into a bath of molten solder such that all exposed copper surfaces are covered by solder. Excess solder is removed by scraping the PCB with hot air knives.The HASL process...
(solder), including excellent surface planarity (particularly helpful for PCB's with large BGA
Ball grid array
A ball grid array is a type of surface-mount packaging used for integrated circuits.- Description :The BGA is descended from the pin grid array , which is a package with one face covered with pins in a grid pattern. These pins conduct electrical signals from the integrated circuit to the printed...
packages), good oxidation resistance, and usability for untreated contact surfaces such as membrane switch
Membrane switch
A membrane switch is an electrical switch for turning a circuit on and off. It differs from a mechanical switch, which is usually made of copper and plastic parts: a membrane switch is a circuit printed on PET or ITO...
es and contact points.
Early ENIG processes suffered from reliability issues which caused the ENIG finish to separate from the copper pads, taking the parts with them. ENIG also does not wet as evenly or easily as HASL.
IPC
IPC (electronics)
IPC, the Association Connecting Electronics Industries, is an organization whose aim is to standardize the assembly and production requirements of electronic equipment and assemblies. It was founded in 1957 as the Institute for Printed Circuits...
Standard IPC-4552 covers the quality and other aspects of ENIG finish on printed circuit boards.