Tips & Tricks #26: ENEPIG — When Should You Choose a Nickel–Palladium–Gold PCB Surface Finish?

The surface finish of a PCB affects solderability, corrosion resistance, suitability for wire bonding, and the reliability of connections throughout the product’s service life. ENEPIG (Electroless Nickel / Electroless Palladium / Immersion Gold) consists of three layers deposited onto copper:

  • electroless nickel,
  • electroless palladium,
  • immersion gold.

What sets ENEPIG apart from ENIG? The additional palladium layer acts as a barrier between nickel and gold, reducing the risk of nickel corrosion during the gold deposition process.

A key advantage of ENEPIG is its suitability for both soldering and wire bonding, particularly with gold wire. Its flat pad surface also supports the assembly of fine-pitch components.

ENEPIG is used in demanding aerospace, defense, medical, and industrial electronics projects, as well as assemblies that incorporate wire bonding. However, the choice of surface finish should be based on the specific requirements of the design and assembly process.

ENEPIG is generally more expensive than ENIG or HASL. It is therefore best suited to applications where its properties provide a clear technical benefit. The reliability of the finished product also depends on PCB manufacturing quality and a properly controlled assembly process.

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