Abstract
Surface-mount techniques primarily depend on soldering. However, soldering techniques have encountered some challenges in recent years. These challenges include rare metal recycling, thermal problems, and Pb toxicity. We recently developed a metallic nanowire surface fastener (NSF) to resolve the abovementioned problems. This fastener can be used to connect electronic components on a substrate at room temperature using the van der Waals force between each nanowire. This study demonstrates a 64-pin NSF that behaves like a ball grid array (BGA) for application to actual electronic devices. The adhesion strength and electrical properties of the NSF were investigated by adjusting the nanowire parameters, such as diameter, length, density (number per area), preload, and shape. The shape control of the nanowires greatly contributed to the improvement of the properties. A maximum adhesion strength of 16.4 N/cm2 was achieved using a bent, hook-like NSF. This strength was 4–5 times the value of the straight NSF. The contact resistivity was 2.98 × 10−2 Ω∙cm2. The NSF fabricated through the simple template method showed the room temperature bonding ability and adaptability to a highly ordered electrode like the BGA.
Highlights
Thermal cracks[12,13,14,15,16] in the connecting part of the electric circuits, which are mainly caused by power devices[10,17] because of the low thermal conductivity of the connecting part
We recently proposed a nanowire surface fastener (NSF)[26,27,28,29], which applies a conductive method that utilizes the van der Waals force between each nanowire to connect to the electronic components
Ju et al developed an NSF composed of an Au nanowire array for which mechanical and electrical bonding was realized at room temperature[26]
Summary
We recently proposed a nanowire surface fastener (NSF)[26,27,28,29], which applies a conductive method that utilizes the van der Waals force between each nanowire to connect to the electronic components. Metallic nanowires, such as Cu and Au, contribute to the high electrical and thermal conductivities. The tops of the nanowires were permanently bent by applying a shear force with the film (Fig. S2(a) in the supplementary information) This process caused the hooked nanowires (e.g., Velcro) to improve the adhesion strength of the NSF. The hooked nanowire array on each electrode pad was bent in several directions to strongly lead them to any direction (Fig. S2(b) in the supplementary information)
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