Advanced surface protection for improved reliability PCB systems (ASPIS)

摘要

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.