Susumu Arai

Fabrication of Nickel–Multiwalled Carbon Nanotube Composite Films with Excellent Thermal Conductivity by an Electrodeposition Technique

Nickel-multiwalled carbon nanotube (MWCNT) composite films were fabricated by an electrodeposition technique, and their microstructure and thermal conductivity were characterized. Nickel-MWCNT composite films with a homogeneous dispersion of MWCNTs throughout the nickel matrix free of any significant voids were electrodeposited from a Ni plating bath containing effective additives and MWCNTs under galvanostatic conditions. The thermal conductivity of the composite films was as high as 109 Wm -1 K -1 , which is about twice that of a nickel film without MWCNTs.

Cu–MWCNT Composite Films Fabricated by Electrodeposition

Copper-multiwalled carbon nanotube (MWCNT) composite plating using a sulfuric base bath was studied. A dispersing agent was used to disperse the MWCNTs into the plating bath. The effects of electrodeposition conditions on the surface morphology, microstructure, and MWCNT content in the composite films were examined. The internal stress, hardness, electrical conductivity, and thermal conductivity of the composite films were also investigated. The current density remarkably affected the surface morphologies of the films, and a relatively smooth surface was obtained at lower current densities. The bath temperature affected the microstructure of the composite films; a compact microstructure was formed at a lower temperature. The MWCNT content in the composite film increased with increasing MWCNT concentration in the plating bath, reaching a maximum value of 0.55 mass %. However, MWCNTs in the composite films tended to agglomerate for high MWCNT concentrations in the plating bath. An internal tensile stress was induced in the films. The hardness of the films was around 150 HV, and the electrical resistivity was approximately 2-2.5 μΩ cm. The thermal conductivity of the Cu-0.42 mass % MWCNT composite film was 355 W m -1 K -1 .

Sn-Ag Solder Bump Formation for Flip-Chip Bonding by Electroplating

Pb-free Sn-Ag alloy solder bumps for flip-chip bonding were formed by electroplating with the aid of a photolithography. Pyrophosphate-iodide baths were used for the plating bath. Smooth, fine-grained Sn-Ag alloy films were obtained using a bath containing both polyethylene glycol (mean molecular weight 600, PEG600) and formaldehyde (HCHO) additives. Sn-Ag alloy films with near eutectic compositions (Sn-3.8 atom % Ag) were obtained under both galvanostatic and potentiostatic conditions. All of the Sn-Ag alloy films deposited consisted of β-Sn phase and e(Ag 3 Sn) phase. Straight-walled bumps and mushroom bumps were formed under both galvanostatic and potentiostatic conditions from the pyrophosphate-iodide bath containing both PEG600 and HCHO. Mushroom bumps with smooth surfaces and homogeneous composition were obtained under potentiostatic conditions.

Carbon Nanofiber-Copper Composites Fabricated by Electroplating

Carbon nanofiber-copper composites are fabricated by composite plating techniques using a plating bath containing an effective dispersing agent for carbon nanofibers. Carbon nanofibers disperse uniformly in the copper matrix, as observed by surface and cross-sectional scanning electron microscopy. By changing electrodeposition parameters, composites with microstructures resembling sea urchins are obtained.

Low-internal-stress nickel multiwalled carbon nanotube composite electrodeposited from a sulfamate bath

Nickel multiwalled carbon nanotube (MWCNT) composite plating was studied using a sulfamate-based bath. The effects of additives, current density, and bath temperature on the microstructure of Ni-MWCNT composite films were examined. The content of MWCNTs and internal stress of the composite films were also investigated. The addition of both sodium saccharin dihydrate and 2-butyne-1,4-diol caused a decrease in the voids formed in the composite films. The amount of voids in the composite films increased with increasing bath temperature. A Ni-MWCNT composite film with 0.4 mass % MWCNTs, no significant voids, and low internal stress was fabricated by adjusting the bath composition and electrodeposition conditions.

Effects of Additives on Cu-MWCNT Composite Plating Films

The effects of plating bath additives on copper-multiwalled carbon nanotube (MWCNT) composite platings were studied. An acidified cupric sulfate electrolyte containing MWCNTs and polyacrylic acid as a dispersing agent was used as the base plating bath. Chloride ions (Cl - ), poly(ethylene glycol), bis(3-sulfopropyl)disulfide (SPS), and Janus green B (JGB) were examined as additives. The surface morphologies and cross-sectional microstructures of the electrodeposited films were investigated, and the MWCNT content of the films was determined. Furthermore, the electrical resistivity and field emission properties of the films were evaluated. The simultaneous addition of Cl - , SPS, and JGB to the base plating bath was effective for forming smooth Cu-MWCNT composite films with a high MWCNT content over a wider range of current densities. The optimal bath composition was 0.85 mol dm -3 CuSO 4 ·5H 2 O + 0.55 mol dm -3 H 2 SO 4 + 100 ppm PA5000 + 2 g dm -3 MWCNTs + 2 ppm SPS + 2 ppm JGB +50 ppm Cl - . Cu-MWCNT composite films containing 0.15-0.33 mass % MWCNTs with smooth surface morphologies were formed in the current density range of 0.5-5 A dm -2 . The electrical resistivity of the films was around 2 μΩ cm, and they showed obvious field emission properties.

Cu/Multiwalled Carbon Nanotube Composite Films Fabricated by Pulse-Reverse Electrodeposition

Cu/multiwalled carbon nanotube (MWCNT) composite plating by a pulse-reverse (PR) electrodeposition method was investigated in order to increase the MWCNT content of the composite plating films. The electrodeposition and dissolution behaviors of the composite films were investigated using scanning electron microscopy and X-ray diffraction to determine the most suitable electrodeposition and dissolution current densities for PR electrodeposition. PR electrodeposition of the Cu/MWCNT composite films was conducted by varying the current reverse ratios at the most suitable electrodeposition and dissolution current densities. The surface morphology of the Cu/MWCNT composite films after dissolution was significantly changed by variation of the anodic current densities. The MWCNT content of the composite films formed by PR electrodeposition was greater than that obtained using a direct current (dc) electrodeposition method, and reached a maximum value of 0.59 mass %, which is a 40% increase over that for dc electrodeposition. Furthermore, the surface roughness of the composite films fabricated by PR electrodeposition was less than that by dc electrodeposition.

Electrodeposition of Ni–P Alloy–Multiwalled Carbon Nanotube Composite Films

Ni-P alloy-multiwalled carbon nanotube (MWCNT) composite films were fabricated by an electrodeposition technique, and their microstructure, hardness, and frictional properties were analyzed. Ni-P alloy-MWCNT composite films containing 20-22 atom % P and 0.7-1.2 mass % MWCNTs were electrodeposited from a composite plating bath. MWCNTs were embedded relatively uniformly in the Ni―P alloy matrix. The hardness of the composite films was higher than that of the Ni―P alloy films, both before and after heat-treatment, and the friction coefficient of the composite films was lower than that of the Ni-P alloy films.

Pure-Nickel-Coated Multiwalled Carbon Nanotubes Prepared by Electroless Deposition

Pure-nickel-coated multiwalled carbon nanotubes (MWCNTs) have been prepared by electroless deposition. Gluconic acid and hydrazine were respectively used as the complexing and reducing agents for nickel ions. The deposits were heat-treated. The microstructures and magnetic properties of the deposits were examined. The MWCNTs were homogeneously coated with pure nickel and their surfaces were relatively bumpy. These pure-nickel-coated MWCNTs exhibited ferromagnetism and had higher magnetizations and coercivities than eleclroless Ni-P alloy-coated MWCNTs. The bumpy morphology of the pure-nickel coating became relatively smooth on heat-treatment.

Fabrication of Various Electroless Ni–P Alloy/Multiwalled Carbon Nanotube Composite Films and Their Frictional Properties

Ni-P alloy/multiwalled carbon nanotube (MWCNT) composite films were fabricated using an electroless plating method, and their microstructures and frictional properties were studied. MWCNTs of various sizes were used and three kinds of electroless plating baths were prepared to form the Ni-P alloy matrix with varying phosphorus contents. Heat-treatments of the composite films were also carried out. The microstructures of the composite films were examined by scanning electron microscopy and X-ray diffraction. Frictional properties of the composite films were investigated using a ball-on-plate method. Ni-P alloy/MWCNT composite films with different phosphorus contents, classified as high phosphorus (12-13 mass,%), medium phosphorus (6-8 mass %), and low phosphorus (2-4 mass %) types, were fabricated using electroless deposition. The Ni-P alloy/MWCNT composite films showed lower friction coefficients compared to Ni-P alloy films with the same phosphorus content both before and after heat-treatment. The friction coefficients of the films were affected by the microstructure and size of the MWCNTs, the composition of the Ni-P alloy matrix, and the heat-treatment.