3D Integration Using Self-Assembly at Air-Water-Solid Interface

This paper presents the first proof-of-concept 3D integration using fluidic self-assembly of chip-scale parts (2000 × 2000 ×100 μm³ ) at an air-water-solid interface. Four-layer 3D integration is achieved by assembling new parts over previously assembled parts. Assembly proceeds as an assembly substrate is pulled up through an air-water interface and electrical and mechanical bonding are achieved by solder reflow. Magnetic fields and temporary Faraday waves are introduced for one-to-one part-to-site registration in proper orientation. The alignment accuracy degrades with increasing number of layers due to weaker magnetic force. The maximum number of layers that can be achieved is simulated and analyzed. Via resistance including the effect of degradation of solder over repeated reflow process is measured.