Effect of Epoxy Flux Underfill on Thermal Cycling Reliability of Sn-8Zn-3Bi Lead-Free Solder in a Sensor Application

M. Mostofizadeh, M. Najari, D. Das, M. Pecht, L. Frisk

    Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

    2 Citations (Scopus)


    The use of sensors has significantly increased in both domestic and industrial applications. In some applications, the sensor component is used along with a heat-sensitive component, therefore, the attachment process using common lead-free solders that have high melting temperature (e.g., Sn-Ag-Cu, Tm = 217 °C) may be challenging. Among lead-free solders with low melting temperature, Sn-8%Zn-3%Bi (wt.%), lead-free solder has a rather similar melting temperature to that of typical Sn-Pb solders. In addition, it offers good mechanical properties. However, the presence of Zn makes it prone to oxidation especially at high temperatures. In this paper, the reliability of sensor attachments using Sn-8%Zn-3%Bi solder and epoxy flux underfill was studied under thermal cycling. Thermal cycling results showed that the lifetime of the lead-free solder joint was lower than that of the Sn-Pb-2Ag solder joints. Failure analysis revealed that the dominant failure mode in lead-free samples was delamination of the sensor pad. In contrast, the failure mode of Sn-36%Pb-2%Ag samples was fatigue crack inside the solder. Additionally, it was found that Sn-Zn-Bi lead-free solder was compatible with epoxy flux underfill.

    Original languageEnglish
    Title of host publicationProceedings - ECTC 2016: 66th Electronic Components and Technology Conference
    Number of pages7
    ISBN (Electronic)9781509012039
    Publication statusPublished - 16 Aug 2016
    Publication typeA4 Article in conference proceedings
    EventIEEE Electronic Components and Technology Conference - , United States
    Duration: 1 Jan 2000 → …


    ConferenceIEEE Electronic Components and Technology Conference
    Country/TerritoryUnited States
    Period1/01/00 → …


    • Failure analysis
    • Sensor
    • Sn-Zn-Bi
    • Solder
    • Thermal cycling
    • Underfill

    Publication forum classification

    • Publication forum level 1

    ASJC Scopus subject areas

    • Electronic, Optical and Magnetic Materials
    • Electrical and Electronic Engineering


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