Is electroless nickel / electroless palladium / immersion gold (ENEPIG) the solution of lead free soldering on PCB and IC packaging applications?

The higher soldering temperatures required for lead free manufacturing place greater demands on the surface finish of the circuit board. Electroless nickel/immersion gold (ENIG) has been a popular surface finish for many years and continues to offer significant advantages to the circuit board industry for applications in mobile phones, keypads and contacts. Despite the body of work undertaken and published by many companies to understand and resolve the issue of nickel pad corrosion by the immersion gold bath, concern remains whether the corrective actions are 100% effective to insure reliable long term use. A palladium deposit from an electroless bath has been known for quite some time, although its use has been limited due to the higher cost. The paper will present experimental data to justify the investigation of ENEPIG as a surface finish with the versatility and reliability to help offset the cost. Characteristics of the deposit and surface morphology will be presented along with test results for solderability, gold wire bonding and ball shear testing to demonstrate that ENEPIG is a viable alternative to ENIG and other final finishes. A brief description of the plating process and control parameters will be provided to demonstrate the potential for volume production of circuit boards with ENEPIG as the surface finish.