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Article
Publication date: 3 February 2012

Andy Ballantyne, Greg Forrest, Martin Goosey, Asta Griguceviciene, Jurga Juodkazyte, Rod Kellner, Aleksandr Kosenko, Rimantas Ramanauskas, Karl Ryder, Algirdas Selskis, Rima Tarozaite and Erik Veninga

The purpose of this paper is to detail progress on the European Commission supported FP7 ASPIS project that is undertaking a multi‐faceted approach to develop novel and improved…

Abstract

Purpose

The purpose of this paper is to detail progress on the European Commission supported FP7 ASPIS project that is undertaking a multi‐faceted approach to develop novel and improved nickel‐gold (ENIG) solderable finish chemistries and processes in order to overcome issues such as “black pad” that are known to cause reliability issues.

Design/methodology/approach

The ASPIS project has four key and discrete approaches; research into “black pad” formation mechanisms, development of new aqueous chemical deposition methods, formulation of new processes based on ionic liquids and the development of prognostic screening tools to enable early prediction of reliability issues.

Findings

Key factors influencing “black pad” formation include immersion gold bath pH value, concentration of citrate and thickness of the immersion gold layer. In addition, copper substrate preparation is also important. Work to develop new metal deposition processes using ionic liquids has also been demonstrated and may provide a viable alternative to more conventional aqueous based chemistries, thereby enabling some of the conditions that lead to “black pad” to be avoided.

Research limitations/implications

This paper summarises the work carried out in the first year of a three‐year project and so the outputs to date are relatively limited. The project is continuing for another two years, when further progress will be made. It is hoped to report this progress in a future update paper.

Originality/value

The ASPIS project has undertaken multiple approaches to the development of new high reliability nickel gold finishes and this combination of approaches should offer synergies over more discrete traditional methodologies. As well as undertaking a detailed analysis of the mechanisms causing reliability problems, radical new formulation and prognostic approaches are also being developed.

Article
Publication date: 16 August 2013

Rimantas Ramanauskas, Algirdas Selskis, Jurga Juodkazyte and Vitalija Jasulaitiene

The purpose of this paper is to verify the principal conclusions, done during the implementation of FP7 ASPIS project objectives in fundamental research of ENIG‐related failures…

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Abstract

Purpose

The purpose of this paper is to verify the principal conclusions, done during the implementation of FP7 ASPIS project objectives in fundamental research of ENIG‐related failures by investigating real problematic PCB samples of different suppliers.

Design/methodology/approach

SEM, EDS and XPS techniques were applied for morphology and composition studies of ENIG coatings of three PCB samples (A, B and C), while electrochemical measurements were used to determine the porosity of EN and IG layers.

Findings

The surface morphology analysis of the un‐soldered pads of PCB A disclosed the fact that the surface of substrate was not pre‐treated in a proper manner before EN deposition, which generated structural defects such as cracks and opening pores in the EN layer, which in turn could produce the voids in the solder layer during the soldering process. The results of PCB B analysis confirmed the authors' observation that Au layers deposited on EN substrate from IG solution contaminated with Cu ions are highly porous and loosely adhering to EN coating, which, in addition, undergoes serious corrosion damages and may be the principal reason for the black pad defect occurrence. High porosity of IG deposit and the presence of the intermediate layer between Au and Ni‐P, which was enriched in Cu and O, were the main reasons for the black pad issue in the case of PCB C.

Originality/value

The gained knowledge on the mechanism of ENIG‐related failures, which cause reliability problems in PCB manufacture, makes it possible to elaborate potential non‐destructive techniques for detecting ENIG problems.

Details

Circuit World, vol. 39 no. 3
Type: Research Article
ISSN: 0305-6120

Keywords

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