SMTA International Conference Proceedings

IMC Study of Mid-Phosphorous and High-Phosphorous ENIG Finishes

Authors: Sandra Nelle, Thiago Pugliesi-Garcia, Britta Schafsteller, Gustavo Ramos
Company: Atotech Deutschland GmbH
Date Published: 9/22/2019   Conference: SMTA International

Abstract: ENIG with mid-phosphorous (MP) nickel is used for soldering and Al wire bonding applications. ENIG with high-phosphorous (HP) nickel serves the niche of environmental corrosive environments.

However, an unspoken fear in the industry concerning high-phosphorous nickel is a poor soldering performance and creation of an extended P-rich layer. This paper aims a comparison in regards of the soldering performance to shed light towards the real soldering performance of MP vs. HP nickel.

Soldering performance will be evaluated by wetting balance, wave soldering and HSS testing. The IMC as a major indicator of solder joint reliability will be evaluated comparing both phosphorus systems. Different reflow conditions will contribute to the formation of different solder alloys and simulate different ageing and soldering conditions.

Apart from solderability, environmental corrosion will be evaluated by gas chamber testing. Further, nickel corrosion performance will be checked as further indication of the quality of the solder joint.

It is also the intention of this paper to evaluate whether there are any further unintended benefits of an HP ENIG.

To evaluate the impact of the different electroless nickel baths in combination with reduction assisted immersion gold, data generated by Design of Experiment (DOE) will be used.

The results are expected to be production applicable and it is hoped that they may clarify myths or misunderstandings within the PCB manufacturing environment.

Key Words: 

IMC, Highest reliability, Corrosion resistance, Solderability, Black pad, High-phosphorous nickel, Mid-phosphorous nickel, 0,2 1 2

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