SGER: Organized organic thin films as "smart" nanointerconnects (Attn: Dr. Kishan Baheti)

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

PI: Rina Tannenbaum NSF - SGER PROJECT SUMMARY One of the key issues in the assembly of printed circuit boards is the precise positioning of the components and leads onto the metallic pads already present on the surface of the substrate. The state of the art technology in this area involves the use of the stencil-printing process, in which a thin layer of solder-paste is deposited on the surface of the substrate and pads, followed by the automatic positioning of the components onto their designated places. The continued demand for higher component density of integrated circuits has lead to an ever-shrinking size of these components, and hence, the positioning issue has become the major handicap, due the very rigid requirements on the assembly process. In particular, the height, area or volume of solder-paste bricks may affect placement accuracy because of the lateral movement of components as leads move through the matrix in the placement process, thus reducing the yield and reliability of the high-density circuits. It is therefore expected that the current surface-mount technologies will soon reach their maximum capability to accommodate the growing needs of the industry and the shrinking size of the components, and as a consequence, component density would have reached saturation as well. To eliminate this bottleneck, a new surface-mount placement technology, operative in the nanometer (or sub-micron) size regime is sought. Hence, a new paradigm for the surface-mount placement process will have to be implemented. At these sub-micron dimensions, the solder-paste technology will have to be replaced by a smart, selective adhesive, that can essentially operate at the molecular-level, and can selectively form precision molecular bridges between the nano-pads and the nanocomponents. This proposal focuses on the utilization of well-known techniques from the surface selfassembly field, in order to construct functional surfaces on the metallic nano-pads that will subsequently bind irreversibly and uniquely to the deposited nanocomponents with very low error and very few processing steps. The smart adhesive will comprise of molecules that will bind selectively to metallic surfaces, nanopads on one side and nanocomponents on the other, forming an interactive, bridging, conductive layer. The desired precision of the processes involved will also call for new ideas in feedback control. Measurements and evaluations of events at the molecular and nanoscale level will need to be translated into observable macroscopic quantities. Hence, mathematical models and resulting computer simulations of the type for which control/systems engineers have a particular expertise may be very helpful in driving some of the specific experiments. In particular, concepts of from particle systems and discrete Markov chains to model the processes involved may be useful. Therefore, the synergistic collaboration of a material scientist and a control theorist will constitute a great opportunity for a comprehensive nano-interconnect system development. The Intellectual Merit of the proposal lies in the bottom-up strategy for the design of an optimal system for a given application. Understanding, down to the molecular level, of the different requirements for the development of a surface-mount placement process that can successfully operate at the nanoscale regime, will afford the choice of the precisely correct building block for the synthesis and assembly of this system. The synergistic combination of experimental work and mathematical modeling will ensure that the process that will be developed will possess the optimal properties in terms of stability (chemical and thermal), selectivity and conductivity. The Broader Impacts of the proposal are both technical and educational. On the technical side, the success of this work will no doubt constitute a paradigm shift in the field of surface mount technology, since it will open up a new size regime and new opportunities for component densities that were unattainable with existing technologies. Moreover, on the educational side, it will expose the graduate students working in these fields to a broader perspective of their area of research, and ultimately generate engineers who are comfortable and well educated in interdisciplinary environments.