The merits and demerits of common surface treatment in PCB industry (ENIG)
4.Electroless Nickel/Immersion Gold (ENIG)
The general process of ENIG is: Acid cleaning -> microetching -> presoaking -> activation -> electroless nickel -> immersion gold.There are six chemical channels in the process, involving nearly 100 chemicals, and the process is a little complicated.
The ENIG is coated with a thick and electrically nickel-gold alloy that could protect the PCB for a long period of time. It also has the tolerance to the environment that other surface treatment processes do not have. In addition, ENIG can also prevent the dissolution of copper, which will be beneficial to lead-free assembly.
Merits: Not easy to oxidize, it can be stored for a long time, surface is smooth and suitable for welding fine gap pin and small welding parts. It is the preferred technology for pressing PCB boards (such as mobile phone boards). It can be repeated several times that reflow soldering is less likely to reduce its weldability. It can be used as the base material for a Chip On Board.
Demerits: High cost and poor welding strength;Because of using electroless nickel process, so it’s easy to have black disk problem. Nickel exposure to air for too long will oxidize, so the long-term reliability is a problem.
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