Mohd Rafie Johan

Addition of cobalt nanoparticles into Sn‐3.8Ag‐0.7Cu lead‐free solder by paste mixing

Purpose – The purpose of this paper is to investigate the effects of addition Co nanoparticles on the characteristic properties of Sn‐3.8Ag‐0.7Cu solder.Design/methodology/approach – Cobalt (Co) nanoparticles were added to Sn‐Ag‐Cu solders by thoroughly blending various weight percentages (0‐2.0 wt%) of Co nanoparticles with near eutectic SAC387 solder paste. Blending was done mechanically for 30 min to ensure a homogeneous mixture. The paste mixture was then reflowed on a hot plate at 250°C for 45 s. The melting points of nanocomposite solder were determined by differential scanning calorimetry. Spreading rate of nanocomposite was calculated following the JIS Z3198‐3 standard. The wetting angle was measured after cross‐sectional metallographic preparation.Findings – No significant change in melting point of the solder was observed as a result of Co nanoparticle addition. The wetting angles of the solder increased with the addition of nanoparticles, while the spreading rate decreased. Although the wetting...

Preparation and Low-Temperature Sintering of Cu Nanoparticles for High-Power Devices

One of the fundamental requirements for high-temperature electronic packaging is reliable silicon attach with low and stable electrical resistance. This paper presents a study conducted on Cu nanoparticles as an alternative lead-free interconnect material for high-temperature applications. Cu nanoparticles were prepared using pulsed wire evaporation technique in water medium. Pure Cu nanoparticles without any organic mixture were used in this paper. An economical approach to extract the nanoparticles from water was established. In situ Cu nanoparticles oxide reduction was successfully done using forming gas (N2-5%H2). Cross-section analysis on bonded interface shows onset of Cu nanoparticles sintering at 400°C. We successfully demonstrated the possibilities of using Cu nanoparticles as silicon die attach material for high-temperature electronic devices.

Synthesis and growth mechanism of silver nanowires through different mediated agents (CuCl 2 and NaCl) polyol process

Silver nanowires (AgNWs) have been synthesized by polyol process through different mediated agents (CuCl2 and NaCl). The presence of cations and anions (Cu(II), Na+, and Cl-) has been shown to have a strong impact on the shape of silver nanostructures. The field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) show uniform nanowires. The UV-vis spectra show that plasmon peak indicated the formation of nanowires. The X-ray diffraction (XRD) pattern displayed that final product was highly crystallized and pure.The growth mechanism of AgNWs was proposed.

Interfacial reaction and dissolution behavior of Cu substrate in molten Sn-3.8Ag-0.7Cu in the presence of Mo nanoparticles

Purpose – In electronic packaging, when solid copper comes in contact with liquid solder alloy, the former dissolves and intermetallic compounds (IMCs) form at the solid‐liquid interface. The purpose of this paper is to study the effect of the presence of molybdenum nanoparticles on the dissolution of copper and the formation of interfacial IMC.Design/methodology/approach – Cu wire having a diameter of 250 μm is immersed in liquid composite solders at 250°C up to 15 min. Composite solder was prepared by adding various amount of Mo nanoparticles into the Sn‐3.8Ag‐0.7Cu (SAC) solder paste. The dissolution behavior of Cu substrate is studied for SAC and Mo nanoparticles added SAC solders. The IMCs and its microstructure between the solder and substrate are analyzed by using conventional scanning electron microscope (SEM) and field emission SEM. The elemental analysis was done by using energy‐dispersive X‐ray spectroscopy.Findings – Generally, the dissolution of the substrate increases with increasing immersi...

Concentration-dependent properties of amorphous carbon nanotube/silica composites via the sol–gel technique

Amorphous carbon nanotube (α-CNT)/silica composites were synthesized by using the sol–gel technique. Fourier transform infrared spectroscopy (FT-IR) reveals the formation of an α-CNT/silica gel network through covalent bonding. Ultraviolet-visible (UV-Vis) spectroscopy shows a strong absorption band of the composites near the UV region. The amorphous structures of the composites are confirmed by X-ray diffraction (XRD) broad peaks. Field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) show a smooth surface at lower weight percentage (wt%) of α-CNTs but a rough surface at higher wt% of α-CNTs. The dielectric properties of the composites have slightly improved by incorporating α-CNTs in the silica.

Temperature-dependent properties of silver-poly(methylmethacrylate) nanocomposites synthesized by in-situ technique

Ag/PMMA nanocomposites were successfully synthesized by in-situ technique. Transmission electron microscopy (TEM) images show that the particles are spherical in shape and their sizes are dependent on temperature. The smallest particle achieved high stability as indicated from Zeta sizer analysis. The red shift of surface plasmon resonance (SPR) indicated the increases of particle sizes. X-ray diffraction (XRD) patterns exhibit a two-phase (crystalline and amorphous) structure of Ag/PMMA nanocomposites. The complexation of Ag/PMMA nanocomposites was confirmed using Raman spectroscopy. Fourier transform infrared spectroscopy spectra confirmed that the bonding was dominantly influenced by the PMMA and DMF solution. Finally, thermogravimetric analysis (TGA) results indicate that the total weight loss increases as the temperature increases.

Quantum size effect in ZnO nanoparticles via mechanical milling

ZnO nanocrystals were successfully produced by mechanical milling. It is shown that mechanical milling is very effective and simple to produce ZnO nanoparticles with the possibility of obtaining large quantities of materials. Size effects in ZnO nanoparticles were probed by XRD and UV-vis and photoluminescence (PL) spectroscopy. Absorption due to free electron was clearly observed, whereas strong PL lines were recorded in the UV and blue region. The absorbance and photoluminescence were found to increase with reduction in particle size. Blueshift of excitonic and emission peaks was observed as a consequence of the size quantization effect. Formation of pure ZnO phase was confirmed from XRD pattern and the optical spectroscopy.

Optical and thermodynamic studies of silver nanoparticles stabilized by Daxad 19 surfactant

Abstract A method for the reduction of AgNO3 in aqueous Daxad 19 solution is presented in this study. The relationships between the size, shape and optical properties of silver nanoparticles are highlighted while controlling synthesis. The variation of size and shape of silver nanoparticles with the change in reactant temperatures are obtained from the transmission electron microscopy images. Ultra violet-visible spectra show that the Surface Plasmon Resonance peak is shifted to the lower wavelength with decreases in particle size. Gibbs free energies (Gf) of silver nanoparticles were calculated by using the data obtained from UV-Vis spectra. Calculation results proved that the Gf of silver nanoparticles have an intimate relationship with the particle size and shape. Gf increases significantly with decrease in particle size. However, the value dropped significantly after the increase in particle size.

Tunable optical properties of Mn-doped CdSe quantum dots synthesized via inverse micelle technique

Manganese-doped cadmium selenium quantum dots (Mn-doped CdSe QDs) were successfully synthesized in the absence of trioctylphosphine (TOP) at various ripening temperatures and times. The TEM image shows the QDs with average particles size of 5.3nm with almost spherical shape. The optical properties of Mn-doped CdSe QDs were investigated using ultraviolet-visible and photoluminescence spectroscopy. The behavior of Mn-doped CdSe QDs was monitored using the red-shift characteristics in the UV-Vis absorption spectra, and their size variations were estimated by the quantum confinement theory. The PL emission spectra of Mn-doped CdSe QDs shows similar evolution behavior as in the absorption behavior. Quantum confinement allows tuning of the CdSe bandgap energy across the Mn excited-state energies. The origin of stokes shift were discovered.

Synthesis, characterisation and stability of superparamagnetic maghemite nanoparticle suspension

Abstract Maghemite nanoparticles were synthesised using the co-precipitation method and characterised by various techniques, including X-ray diffraction, transmission electron microscopy, alternating gradient magnetometry, dynamic light scattering and zeta potential. The stability of the suspension was monitored by measuring the particle size distribution and zeta potential using dynamic light scattering over a period of few months. The pattern obtained from X-ray diffraction confirmed that the particles were maghemite with crystallite size of 9·4 nm. Transmission electron microscopy observations and analyses showed that the mean physical size of the nanoparticles was 9·5 nm. The nanoparticles show superparamagnetic behaviour with magnetisation value at ±10 kOe of 32·18 emu g−1. The intensity averaged particle size of as-synthesised maghemite nanoparticles was 45·3 nm. The suspension was stored for periods of 2, 4 and 8 months. The intensity averaged sizes were 47·1, 50·5 and 52·1 nm respectively. No sedimentation was observed. The suspensions zeta potential value was 44·6 mV for as-synthesised sample and 43·3, 42·7 and 41·8 mV for sample after storage period of 2, 4 and 8 months, respectively. This indicated that the suspension was very stable.