In this paper, a new sequential stacking self-assembly using interfacial tension of two different droplets of TEGDMA (Triethyleneglycol Dimethacrylate) and 42Sn-58Bi solder was proposed. TEGDMA with an additional thermal initiator is liquid at room temperature and hardens by heat. 42Sn-58Bi solder is solid at room temperature and melts at 138 °C. Since interfacial tension of TEGDMA and 42Sn-58Bi solder are selectively utilized by setting the process temperature at room temperature for TEGDMA and 150 °C for 42Sn-58Bi solder, the sequential self-assembly of different components can be realized. The feasibility of the proposed process and alignment accuracy were experimentally examined using 1 mm square silicon chips as test components. The first component assembly on a substrate was carried out at room temperature using TEGDMA as an adhesive agent, and the second component assembly on the assembled component was carried out at 150 °C using 42Sn-58Bi solder as an adhesive agent. Both self-assembly processes were carried out in EG (Ethylene Glycol) solvent with an additional sulfuric acid. It was confirmed that the first and second self-assembly was successfully done at room temperature and at 150 °C, and alignment accuracy of first and second self-assembly were 33 μm and a few μm, respectively.
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