Designing a High Performance Electroless Nickel and Immersion Gold
It was the goal of this paper to overcome myths and misunderstandings within the PCB manufacturing environment regarding the HP ENIG finish.
Materials Tech
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Authored By:
Robert Spreemann
Rick Nichols
Sandra Nelle
Atotech Deutschland GmbH
Berlin, Germany
Summary
The latest highest reliability requirements demand a high performance electroless nickel and immersion gold (HP ENIG). The new IPC specification 4552A has refocused the industry with reference to nickel corrosion. The interpretation of the existing specification, that judges corrosion on 3 levels, is complex and if misinterpreted can lead to phantom failures. An obvious way to avoid any potential misinterpretation is to eradicate any evidence of corrosion completely.
Solderability and environmental corrosion resistance are also highly significant prerequisites when discussing Highest Reliability. These will be evaluated by High Speed Shear testing (HSS) and gas chamber testing respectively.
In addition to the more demanding requirements of the HP ENIG to satisfy High Reliability requirements, the system needs to exhibit good basic layer characteristics.
It is also the intention of this paper to evaluate whether there is any ‘value added’ or unintended benefits to a HP ENIG. An example of this would be superior gold distribution and associated gold saving potential. Data generated by Design of Experiment (DOE) will be used to evaluate the impact of electroless nickel variables in combination with traditional and cyanide free immersion gold on recognized quality expectations. The results are expected to be practical and production applicable solution underpinned by solid data and it is hoped that they may dispel myths or misunderstandings within the printed circuit board (PCB) manufacturing environment.
Initially Published in the SMTA Proceedings
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