From Microjoining to Nanojoining

Abstract

A review is provided of the recent advances and challenges in nanojoining, as compared to microjoining and even regular joining processes. Nanojoining examples are given and analyzed in various joining categories such as solid- state bonding, soldering/brazing and fusion welding. Proposed strategies for nanoassembly and nanojoining, e.g., self- organization and inkjet printing, are also highlighted. Joining (welding, brazing, soldering, bonding, etc.), whether at macro-, micro- or nano-scale, is an essential step of man-made product manufacturing and assembly, providing mechanical support and integration, electrical connection, optical coupling, environmental protection, etc. (1) This review focuses only on joining processes that aim to produce permanent unions between macro-, micro- and nano-sized building blocks to be assembled, through the formation of primary (and occasionally secondary) chemical bonds between the faying surfaces. The exception to this metallurgical definition is mechanical joining (fastening, riveting, crimping, etc.), in which the original free surfaces of the parts are retained mostly unaltered in mechanical joints. The continuing miniaturization of engineered devices and systems, coupled with ever-growing demands for cost reduction, enhanced performance and reliability, etc. brings