Foil-to-Foil System Integration Through Capillary Self-Alignment Directed by Laser Patterning

This paper introduces a new integration technology for cost-effective high-precision mechanical and electrical integration of mesoscopic functional foil components onto foil substrates. The foil-to-foil assembly process is based on topological surface structuring via laser patterning that enables accurate capillarity-driven self-alignment of foil dies. The concurrent establishment of high-yield electrical interconnections is obtained through conductive adhesives. The foil surface energy controls the acceptance window of initial offsets for optimal self-alignment performance. The proposed topological patterning and system design enable alignment accuracies for centimeter-sized foil dies as high as 15 μm, barely influenced by the evaporation of the assembly liquid and curing of the conductive paste. Full foil-to-foil system integration is demonstrated through the electrically functional assembly of an array of Au-sputtered capacitive humidity sensors onto a patterned base foil circuitry.