Do you know what is ENEPIG in PCB?

 What is ENEPIG？ENEPIG-Electroless Nickel Electroless Palladium Immersion Gold is a surface finish for Printed Circuit Boards.ENEPIG works well with lead free and conventional eutectic solder alloys.This is the best way for gold wire bonding. Advantages for ENEPIG:

  • “Black Nickel” free – no possibility of grain boundary corrosion of nickel surface by immersion gold
  • Palladium acts as an additional barrier layer to further reduce copper diffusion to surface, thus ensuring good solderability
  • Palladium completely dissolves into solder, without leaving an excessively high P% rich interface, exposing an oxide-free nickel surface allowing reliable formation of Ni/Sn intermetallic
  • Withstands multiple lead-free reflow soldering cycles
  • Demonstrates excellent gold wire bondability
  • Process costs substantially lower than electrolytic nickel gold or electroless nickel electroless gold

Here is an ENEPIG PCB ,60GHz Transceiver DC Board for Columbia University.
Thickness:Ni:3-5um +/-5%,  Pd:0.1um +/-10%, Au:0.05um +/-10%
Top layer with ENEPIG finish.
ENEPIG board,Bottom layer with bare copper

Comparison of Surface Finish Performance

Characteristics OSP ENIG Immersion Tin Immersion Siver ENEPIG
Shelf Life < 12 Months/td> > 12 Months 3-6 Months < 12 Months > 12 Months
Multiple Soldering Cycles Fair to good good Fair to good Fair to good good
No Clean Flux Usage PTH/via fill concerns No concerns No concerns No concerns No concerns
Solder Joint Reliability Good Good process control required to avoid "black pad Good Interfacial microvoid concerns Good
Gold Wire bonding NO NO NO NO YES
Corrosion Risk after Assembly YES NO NO NO YES
Corrosion Risk after Assembly YES NO YES NO NO
Contact Surface Applications NO YES NO NO YES
Total Coating Thickness (um) >0.15 Au:0.08-0.13,Ni:3.0-6.0 Tin:1.0-1.1 0.05-0.1 AU:0.03-0.05,Pd:0.05-0.1,Ni:3-5
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