Fabrication of Copper / Single-Walled Carbon Nanotube Composite Plating Films By Electrodeposition
Copper has many excellent properties such as high electrical conductivity and good thermal conductivity and ductility, resulting in the wide use of copper plating in the electronics industry. Single-walled carbon nanotubes (SWCNTs) also exhibit attractive characteristics such as stable electrical resistance in the presence of high currents and good thermal conductivity and field emission properties, resulting in their application in a wide range of fields. Cu/SWCNT composites would therefore be expected to have excellent electrical and thermal conductivity properties.Our laboratory previously reported the fabrication of electroless Cu/SWCNT composite plating films, 1)but the fabrication of Cu/SWCNT composite plating films by electrodeposition has not been reported.Here we describe an attempt to fabricate Cu/SWCNT composite plating films with homogeneously distributed SWCNTs using electrodeposition.
The Cu/SWCNT composite plating bath comprised 0.1 M CuSO4･5H2O, 0.2 M EDTA･2Na, SWCNTs (Super-growth SWCNTs, Zeon Co.) and dispersants. EDTA･Na was used as a copper chelating agent. A magnetic stirrer, an ultrasonic homogenizer and a mechanical atomizer (Star Burst Labo, SUGINO MACHINE Co.) were used to fragment the SWCNT bundles. The dispersibility of the SWCNTs was evaluated using a particle size distribution analyzer. Electrodeposition was conducted under galvanostatic conditions. A pure copper plate and a phosphorus-containing copper plate were used as cathode and anode, respectively. The morphologies of the composite films were observed by field emission scanning electron microscopy (FE-SEM) and the phase structures of the films were analyzed by X-ray diffraction. The thermal and electrical conductivities of the composite films were also evaluated. In addition, the SWCNTs were quantitatively analyzed.
Results and Discussion
The results demonstrated that fragmentation of the SWCNTs was improved significantly by using a mechanical atomizer. The content of SWCNTs in the films increased with increasing SWCNT concentration in the plating bath. Fig. 1 shows a surface SEM image of a prepared Cu/SWCNT composite plating film and indicates that the SWCNTs are incorporated relatively uniformly into the Cu film. The diameter of the SWCNTs is ca. 15 nm or less, indicating that the bundles of SWCNTs are highly fragmented.