Inkjet printing technology for increasing the I/O density of 3D TSV interposers

Behnam Khorramdel, Jessica Liljeholm, Mika-Matti Laurila, Toni Lammi, Gustaf Mårtensson, Thorbjörn Ebefors, Frank Niklaus, Matti Mäntysalo

    Research output: Contribution to journalArticleScientificpeer-review

    14 Citations (Scopus)
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    Interposers with through-silicon vias (TSVs) play a key role in the three-dimensional integration and packaging of integrated circuits and microelectromechanical systems. In the current practice of fabricating interposers, solder balls are placed next to the vias; however, this approach requires a large foot print for the input/output (I/O) connections. Therefore, in this study, we investigate the possibility of placing the solder balls directly on top of the vias, thereby enabling a smaller pitch between the solder balls and an increased density of the I/O connections. To reach this goal, inkjet printing (that is, piezo and super inkjet) was used to successfully fill and planarize hollow metal TSVs with a dielectric polymer. The under bump metallization (UBM) pads were also successfully printed with inkjet technology on top of the polymer-filled vias, using either Ag or Au inks. The reliability of the TSV interposers was investigated by a temperature cycling stress test (−40 °C to +125 °C). The stress test showed no impact on DC resistance of the TSVs; however, shrinkage and delamination of the polymer was observed, along with some micro-cracks in the UBM pads. For proof of concept, SnAgCu-based solder balls were jetted on the UBM pads.
    Original languageEnglish
    Pages (from-to)17002
    JournalMicrosystems & Nanoengineering
    Publication statusPublished - 10 Apr 2017
    Publication typeA1 Journal article-refereed

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