New trends for PWB surface finishes in mobile phone applications

Claus Würtz Nielsen, Rajan Ambat, Anette Alsted Rasmussen, Per Møller

    Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review

    Abstract

    Immersion Ni/Au has been the overall dominant surface finish on PWB's for the last 10 years. During the last 5 years Mobile Phones have been extremely popular and spread all over the world in different climate zones in very high volumes. At the same time the Mobile Phone terminal for many people has become a necessity that is brought with them in any activity they practice. These changes in user behaviour have heavily changed the impact from moisture, sweat, corrosive atmospheres and mechanical drop. As a result of this the requirement to solder joint reliability, corrosion stability and wear resistance are heavily increasing to keep a high reliability of the terminal. A paradigm shift to avoid use of Immersion Ni/Au is ongoing nowadays because the thin and porous Imm. Ni/Au can't address these challenges in a satisfactory way. Already some years ago OSP has replaced Immersion Ni/Au on solder pads in terminals from Nokia with positive impact on solder joint reliability. Theoretical electrochemical studies, experimental work and full scale high volume production has now demonstrated that Carbon surface finish for Key- and spring contact-pads, combined with the right concept design will make use of Imm. Ni/Au unnecessary in the near future. The end result is higher reliability with less expensive and simpler processes. This paper will discuss the various considerations for choice of surface finish and results from the extensive feasibility studies performed by Nokia Mobile Phones, supplemented by theoretical electrochemical studies performed by IPU/DTU.
    Original languageEnglish
    Title of host publicationProceedings of Pan Pacific Microelectronic Symposium
    Publication date2005
    Publication statusPublished - 2005
    EventPan Pacific Microeletronics Symposium -
    Duration: 1 Jan 2005 → …

    Conference

    ConferencePan Pacific Microeletronics Symposium
    Period01/01/2005 → …

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