High-Accuracy Pick-and-Place of Multiple Dies in Parallel Assisted by Capillary Self-Alignment

Abstract

Self-assembly of components driven by liquid surface tension is an attractive complement and even alternative to traditional high-accuracy pick-and-place as it offers high accuracy despite inaccurate robotic part placement. While capillary self-alignment through liquid solder is the standard technology for flip-chip processes, this work presents self-alignment of dies on wetted receptors on a temporary carrier: Low-viscosity liquid is jetted on each receptor where the liquid is contained through generation of hydrophilic and hydrophobic sections on the temporary carrier by plasma treatment. Deterministic die feeding by low-accuracy pick-and-place is conducted for single dies, as well as for batches of three dies and nine dies optimizing the equipment for best throughput to achieve both high accuracy and high productivity. The industry-ready and fully automated chip-to-wafer pick-and-place process is implemented into a fan-out wafer-level packaging production flow proving that self-alignment is capable of easing the stringent requirement for robotic alignment capability for pick-and-place systems in fan-out packaging for the single die-level step in this production chain. The self-alignment process is optimized, and failure modes such as poor liquid confinement, surface contamination, or excess force are identified and eliminated. Post-bond accuracy of <3 μm @ 3 σ at each point of the die is reached for dies of 3.1 mm x 3.1 mm in size. Using parallel die handling, high speeds of around 10 000 units per hour are made possible.