Microscale self-assembly using molten alloys with different melting points
Schematic showing the dual alloy fluidic self-assembly process. The template schematic shows contact pads and interconnects for self-assembled solder contact characterization.
Template fabrication process.
Completed parts. “Sites” refer to those intended for binding to specific alloy regions on the template in Fig. 3.
Details of template solder alloy heights. (A) Optical image and scanning electron microscope image showing the side view of a deposited Bi–Sn solder “bump.” (B) Surface evolver model and experimental data for Bi–Sn height with the dashed line showing model predictions for assembled part height. Details of the template height. (C) Surface evolver model for predictions of the Pb–Sn solder alloy height before and after reflow with scanning electron microscope images showing side views of Pb–Sn features on templates.
Parts self-assembled on a template showing two types of defects. In many cases, intended Pb–Sn binding sites on the parts have assembled on Bi–Sn areas. The other type of defect in this image is that excessive tilt has prevented electrical contact on one side of an otherwise properly aligned part.
Scanning electron microscope images showing self-assembled electrical connections.
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