Self-alignment of RFID dies on four-pad patterns with water droplet for sparse self-assembly

Bo Chang, Iiris Routa, Veikko Sariola, Quan Zhou

    Research output: Contribution to journalArticleScientificpeer-review

    19 Citations (Scopus)


    This paper reports an in-depth study of a water-droplet-assisted self-alignment technique that self-aligns radio frequency identification (RFID) dies on four-pad patterns. The segmented structure of four hydrophilic pads on a hydrophobic substrate brings freedom to the design of the electrical functionality and the surface functionality. The paper investigates the influence of the key parameters that may affect the self-alignment in theory and experiment. The theoretical model justifies that RFID dies can be reliably aligned on the segmented four-pad pattern even when the initial placement error is as large as 50% of the size of the die and the gap between the four pads is about 10% of the size of the die. A method has been introduced to estimate the sufficient droplet volume for self-alignment. A series of experiments have been carried out to verify the results of the model. The experiments indicate that the self-alignment between the 730 × 730 νm RFID dies and the pattern occurs reliably when the releasing bias between the RFID die and antenna is less than 400 νm for patterns with 50 and 100 νm gaps, and successful self-alignment is possible even with greater bias of 500 νm.

    Original languageEnglish
    Article number095024
    JournalJournal of Micromechanics and Microengineering
    Issue number9
    Publication statusPublished - Sept 2011
    Publication typeA1 Journal article-refereed

    ASJC Scopus subject areas

    • Electronic, Optical and Magnetic Materials
    • Mechanics of Materials
    • Mechanical Engineering
    • Electrical and Electronic Engineering


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