The effect of cooling rate on grain orientation and misorientation microstructure of SAC105 solder joints before and after impact drop tests

Payam Darbandi, Thomas R. Bieler, Farhang Pourboghrat, Tae Kyu Lee

    Research output: Research - peer-reviewArticle

    • 10 Citations

    Abstract

    The effect of different cooling rates on as-assembled Sn1.0Ag0.5Cu (wt.%) solder joints was investigated by using orientation imaging microscopy to characterize evolution of the microstructure and orientation distribution on test samples before and after shock testing. Evolution of the microstructure of joints located near the corners after shock testing differed substantially for samples cooled at different rates after fabrication. After shock and impact testing, much recrystallization was observed for the rapidly cooled samples; this led to polycrystalline microstructures that were effective in absorbing impact energy, by incorporating a growing crack into the recrystallized tin microstructure rather than the lower-energy intermetallic interface, and thus prolonging life. The slowly cooled samples contained large amounts of (301)[103] mechanical twins, which also led to an increased number of interfaces that were effective in absorbing energy. The smallest amount of new interface generation after shock testing occurred in the normal cooling rate microstructures, which had the shortest life. Analysis of the crack-propagation paths associated with different cooling rates indicates that development of interfaces from either twinning or polycrystalline microstructure favors crack propagation through the solder rather than the intermetallic layer interface, which toughens the joint.

    LanguageEnglish (US)
    Pages2521-2529
    Number of pages9
    JournalJournal of Electronic Materials
    Volume43
    Issue number7
    DOIs
    StatePublished - 2014

    Profile

    drop tests
    solders
    misalignment
    cooling
    microstructure
    Soldering alloys
    Cooling
    Microstructure
    shock
    Shock testing
    energy
    crack propagation
    intermetallics
    Intermetallics
    Crack propagation
    twinning
    tin
    cracks
    microscopy
    fabrication

    Keywords

    • mechanical Shock
    • OIM
    • Pb free solder
    • recrystallization
    • Sn orientation

    ASJC Scopus subject areas

    • Electrical and Electronic Engineering
    • Electronic, Optical and Magnetic Materials
    • Condensed Matter Physics
    • Materials Chemistry

    Cite this

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    abstract = "The effect of different cooling rates on as-assembled Sn1.0Ag0.5Cu (wt.%) solder joints was investigated by using orientation imaging microscopy to characterize evolution of the microstructure and orientation distribution on test samples before and after shock testing. Evolution of the microstructure of joints located near the corners after shock testing differed substantially for samples cooled at different rates after fabrication. After shock and impact testing, much recrystallization was observed for the rapidly cooled samples; this led to polycrystalline microstructures that were effective in absorbing impact energy, by incorporating a growing crack into the recrystallized tin microstructure rather than the lower-energy intermetallic interface, and thus prolonging life. The slowly cooled samples contained large amounts of (301)[103] mechanical twins, which also led to an increased number of interfaces that were effective in absorbing energy. The smallest amount of new interface generation after shock testing occurred in the normal cooling rate microstructures, which had the shortest life. Analysis of the crack-propagation paths associated with different cooling rates indicates that development of interfaces from either twinning or polycrystalline microstructure favors crack propagation through the solder rather than the intermetallic layer interface, which toughens the joint.",
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    author = "Payam Darbandi and Bieler, {Thomas R.} and Farhang Pourboghrat and Lee, {Tae Kyu}",
    year = "2014",
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    AU - Darbandi,Payam

    AU - Bieler,Thomas R.

    AU - Pourboghrat,Farhang

    AU - Lee,Tae Kyu

    PY - 2014

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    N2 - The effect of different cooling rates on as-assembled Sn1.0Ag0.5Cu (wt.%) solder joints was investigated by using orientation imaging microscopy to characterize evolution of the microstructure and orientation distribution on test samples before and after shock testing. Evolution of the microstructure of joints located near the corners after shock testing differed substantially for samples cooled at different rates after fabrication. After shock and impact testing, much recrystallization was observed for the rapidly cooled samples; this led to polycrystalline microstructures that were effective in absorbing impact energy, by incorporating a growing crack into the recrystallized tin microstructure rather than the lower-energy intermetallic interface, and thus prolonging life. The slowly cooled samples contained large amounts of (301)[103] mechanical twins, which also led to an increased number of interfaces that were effective in absorbing energy. The smallest amount of new interface generation after shock testing occurred in the normal cooling rate microstructures, which had the shortest life. Analysis of the crack-propagation paths associated with different cooling rates indicates that development of interfaces from either twinning or polycrystalline microstructure favors crack propagation through the solder rather than the intermetallic layer interface, which toughens the joint.

    AB - The effect of different cooling rates on as-assembled Sn1.0Ag0.5Cu (wt.%) solder joints was investigated by using orientation imaging microscopy to characterize evolution of the microstructure and orientation distribution on test samples before and after shock testing. Evolution of the microstructure of joints located near the corners after shock testing differed substantially for samples cooled at different rates after fabrication. After shock and impact testing, much recrystallization was observed for the rapidly cooled samples; this led to polycrystalline microstructures that were effective in absorbing impact energy, by incorporating a growing crack into the recrystallized tin microstructure rather than the lower-energy intermetallic interface, and thus prolonging life. The slowly cooled samples contained large amounts of (301)[103] mechanical twins, which also led to an increased number of interfaces that were effective in absorbing energy. The smallest amount of new interface generation after shock testing occurred in the normal cooling rate microstructures, which had the shortest life. Analysis of the crack-propagation paths associated with different cooling rates indicates that development of interfaces from either twinning or polycrystalline microstructure favors crack propagation through the solder rather than the intermetallic layer interface, which toughens the joint.

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    KW - Sn orientation

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