13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Core Shell Nanowire Surface Fastener Used for Mechanical and Electrical Room Temperature Bonding Peng Wang, Yang Ju*, Atsushi Hosoi Department of Mechanical Science and Engineering, Nagoya University, Nagoya 464-8603, Japan * Corresponding author: ju@mech.nagoya-u.ac.jp Abstract This paper presents a method of fabricating surface fastener for the application of mechanical and electrical room temperature bonding based on core shell nanowire array. This surface fastener consists of core shell nanowire array with the copper core and parylene shell. The copper nanowire array on the silicon substrate was prepared through template-assistant electro-deposition, which provided the electrical conductive function. The parylene shell was deposited on Cu nanowire array through CVD method, which provided surface compliance to increase contact areas, thereby realizing larger bonding strength. Through pressing core shell nanowire arrays against each other, the van der Waals forces between the interpenetrating nanowires had a contribution to the room temperature. This room temperature bonding technology may enable the exploration of a wide range applications involving assembly of components in the micro electronics. Keywords Core shell, Nanowire, Surface fastener 1. Introduction The continuous trend towards miniaturization and functional density enhancement makes an urgent demand to improve the bonding technology in the surface mount technology. The traditional bonding technology utilizes the solder. However, solder has relatively high electrical properties and copper-tin intermetallics have poor mechanical propertities[1]. An all-copper connection technology has been introduced, but the annealing temperature range of 350-450°C is too high for cost-efficient organic broads or substrates[2]. Moreover, the surface-activated bonding method has been reported, which can be performed at room temperature[3, 4].However, the high electrical resistance (above 1000Ω) may prohibit it application in electrical interconnection. Therefore, to create a bonding technology which not only has good mechanical and electrical property but also does not need high processing temperature is always a destination for the researchers. With the efficient utilization of von der Waals forces, the gecko can firmly attach to and rapidly detach from varied kinds of surfaces. Many methods have been used to replicate this adhesion mode by some well-arranged micro and nanostructure arrays. Some gecko-inspired adhesive designs with nanowire arrays were cast through porous membranes available from commercial suppliers[5, 6]. Moreover, some special polymer micro and nanostructures, such as mushroom-shaped fibers[7], wedge-shaped fibers[8], bent fibers[9], spatula tips[10], led to bigger strength but also a more complicated manufacturing process. Recently, by using vertically aligned multiwalled carbon nanotube (MWCNT) with curly entangled end segment[11], the extremely high shear adhesion (∼100 N/cm2) was obtained, which was ten times higher than gecko’s adhesion strength. Compared with the template method, the chemical vapor deposition method used to fabricate MWCNT is expensive and need high processing temperature. Recently, a new kind of bonding technique based on core/shell nanowire structure has been demonstrated[12]. Moreover, electrical connector can be obtained through depositing a thin metal film on the nanowires[13]. Although this structure can achieve mechanical interconnection at room room temperature, the high temperature in the fabrication process and the relatively high electrical resistance prohibit their application in the bonding technique in micro electronics. In this paper,
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