PWB Processes: EPIG

EPIG

Electroless Palladium, Immersion Gold (EPIG)

EPIG nickel-free PCB finish is gold wire bondable, solderable, and ideal for HF use. It has opened up a wide, new design avenue for high frequency applications and designs with reduced spacing.

The EPIG process deposits palladium directly onto copper. Eliminating the nickel means there’s less build-up on circuits, and circuits can be controlled with smaller geometries. It’s a perfect fit for applications that demand smaller features and better clearances.

EPIG offers unique and significant advantages for microwave applications, flex circuits, and end users requiring high purity levels. These advantages include:

  • No nickel to fracture on bending for flex circuits
  • Maintains solderability and wire bondability to copper circuits
  • Short process time
  • No EN to pose corrosion issues
  • No skin effect on low current, HF applications
  • Non-magnetic
  • Suitable for tight lines and spaces
  • Easy to visually inspect
  • Reworkable in most circumstances

Read “Characteristics of EPIG Deposits for Fine Line Application” by Don Gudeczauskas, George Milad, et al. in the Uyemura Library.

Talon 3 Electroless Palladium for EPIG

Uyemura has announced the commercial availability of Talon 3 electroless palladium, a groundbreaking technology in board chemistry that allows plating directly onto copper. This development effectively paves the way for EPIG – electroless palladium/ immersion gold, a nickel-free alternative that becomes more consequential as lines become tighter and space becomes more critical.

Talon 3 E-Pd was developed for applications that cannot tolerate nickel for other reasons as well. These applications are numerous, and fall into four main categories: medical sensors, where nickel is prohibited for reasons of patient sensitivity; flexible circuits, where there’s a risk of nickel fracturing creating gaps in the circuits; electronic products that cannot use nickel due to problems related to magnetics and frequency, and high frequency circuitry (particularly aerospace) where nickel can compromise signaling.

Talon 3 deposits an electroless / autocatalytic palladium that is solderable and gold wire bondable. The bath has a low palladium metal content and is highly stable. The rate of deposition and quality of the deposit are consistent throughout the product’s bath life.

The EPIG finish made possible with Talon 3 electroless palladium solders perfectly after eight hours of steam aging – a significant achievement.