ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold) is a type of surface plating applied on a Printed Circuit Board to protect it from environmental factors during storage and operation. ENEPIG is prepared by depositing electroless Nickel (Ni 3-5 μm), followed by electroless Palladium (Pd 0.05-0.1μm), and an immersion Gold layer (Au 0.03-0.05 μm). It is good for solder joint strength, gold wire bonding, aluminum wire bonding, and provides low contact resistance. It can easily be deposited on almost any PCB which is why it is also called the ‘Universal Finish’.

What are the advantages of ENEPIG over ENIG?

ENEPIG plating has an additional layer of Palladium when compared to the ENIG plating which consist of just Nickel and Gold. This additional layer helps avoid what is know as the ‘Black Pad’ syndrome i.e. the result of corrosion caused by the Gold to the Nickel layer.

Advantages of ENEPIG Finishes:

• Palladium layer totally covers the Nickel layer, and the amount of phosphorus in the palladium layer is less than in the Nickel layer, which inhibits the generation of black nickel (also called Black Pad syndrome).
• The Palladium fusion point (1,554°C) is higher than Gold (1,063°C). As a result of this, Palladium’s fusion speed at high temperatures is comparatively low, which allows more time for Nickel layer protection before going to the final assembly.
• Palladium is harder than Gold, which offers improved solder joint quality, wire bonding capacity, and antifriction.
• Using Palladium allows for the reduction in the thickness of the Gold layer, which eventually reduces the cost.
• It can withstand multiple reflow cycles
• Processing cost is comparatively lower than ENIG and ENEG surface finishes. 
• Very-well adjustable for Lead-free solder tendency

Limitation of ENEPIG Surface Finish: It is more prone to fractures due to the brittleness of the tin-palladium layers formed on top of the nickel plating.

Uses of ENEPIG Surface Finishes

ENEPIG Surface Finishies are ideal for Printed Circuits Boards that support various package types including THT (through-hole technology), SMT, BGA, wire bonding, etc. They are often used in the aerospace & defense industry as well as the medical industry. ENEPIG finishes are used in high density, high performance devices.