Zul Azhar Zahid Jamal

Temperature cycling analysis for ball grid array package using finite element analysis

Purpose – The purpose of this paper is to discuss the capability of finite element analysis (FEA) in performing the virtual thermal cycling reliability test to evaluate the reliability of solder joints in a ball grid array (BGA) package.Design/methodology/approach – Thermal cycling test has been used to evaluate the reliability or fatigue life of the solder joints in BGA package using commercially available FEA software, ANSYS™. The effect of different temperature cycling condition is studied by applying different value of dwell time and ramp rate. Two types of analyses are used namely, the physics‐based analysis and the statistical‐based analysis. Two screening design methods namely, central composite design (CCD) and Box‐Behnken Matrix Design method are used to isolate the most important factors amongst six selected design variables. The optimization process is carried out using response surface methodology (RSM).Findings – It is observed that changes in ramp rate produce significant effect in solder fa...

Microstructure Study on Gd-Doped BaTiO3 Sol-Gel Multilayer Thin Films Using AFM for Optoelectronic Applications

Gadolinium doped barium titanate (Gd-BaTiO3) thin films with the molar ratio of 70:30 have been fabricated on SiO2/Si substrates using sol-gel technique. The effect of number of deposited layers on the grain size and surface morphology has been investigated using an atomic force microscope in contact mode. AFM micro-images show that the films have well distributed grains, dense and crack free surface. In general, the results show that the grain size increases from ~170 nm to ~189 nm as the number of deposited layers increase from one to four layers which attributed to the grain growth mechanism during heating and annealing processes. However, the surface of the films is analysed through amplitude parameters to find out that the films surface is smooth with a predominant for peaks and relatively low number of high peaks and low valleys.

X-ray line profile analysis of BaTiO3 thin film prepared by sol-gel deposition

Barium titanate (BaTiO3) thin film was prepared using sol-gel method and spun-coated on SiO2/Si substrate. The phase and crystallinity of the synthesized film were identified using X-ray diffractometer (XRD), which scanned at the range of 20° to 60°. The phase and lattice parameters of the fabricated film were extracted from the recorded XRD patterns using lattice geometry equations. The crystallite size and lattice strain were determined using X-ray line profile analysis (XLPA) with various approaches. The Scherrer equation was applied to the perovskite peaks of the film to explore the size contribution on the peak broadening. Meanwhile, the Williamson-Hall and size-strain plot (SSP) methods were used to review two main independent contributions, i.e. crystallite sizes and lattice strain, on the X-ray line broadening. From the analysis, it is found that Scherrer method gives smallest crystallite size value by ignoring the strain-induced broadening effect. On the other hand, Williamson-Hall and SSP graphs revealed the existence of the lattice strain within the film, which contributes to the broadening in the Bragg peak. The results that analyzed via both techniques show a linear trend with all data points fitted. However, result obtained from SSP method gives better settlement due to the best fit of the data.Barium titanate (BaTiO3) thin film was prepared using sol-gel method and spun-coated on SiO2/Si substrate. The phase and crystallinity of the synthesized film were identified using X-ray diffractometer (XRD), which scanned at the range of 20° to 60°. The phase and lattice parameters of the fabricated film were extracted from the recorded XRD patterns using lattice geometry equations. The crystallite size and lattice strain were determined using X-ray line profile analysis (XLPA) with various approaches. The Scherrer equation was applied to the perovskite peaks of the film to explore the size contribution on the peak broadening. Meanwhile, the Williamson-Hall and size-strain plot (SSP) methods were used to review two main independent contributions, i.e. crystallite sizes and lattice strain, on the X-ray line broadening. From the analysis, it is found that Scherrer method gives smallest crystallite size value by ignoring the strain-induced broadening effect. On the other hand, Williamson-Hall and SSP graphs...

Oxide semiconductors for solar to chemical energy conversion: nanotechnology approach

The present work considers the application of oxide semiconductors in the conversion of solar energy into the chemical energy required for water purification (removal of microbial cells and toxic organic compounds from water) and the generation of solar hydrogen fuel by photoelectrochemical water splitting. The first part of this work considers the concept of solar energy conversion by oxide semiconductors and the key performance-related properties, including electronic structure, charge transport, flat band potential and surface properties, which are responsible to the reactivity and photoreactivity of oxides with water. The performance of oxide systems for solar energy conversion is briefly considered in terms of an electronic factor. The progress of research in the formation of systems with high performance is considered in terms of specific aspects of nanotechnology, leading to the formation of systems with high performance. The nanotechnology approach in the development of high-performance photocatalysts is considered in terms of the effect of surface energy associated with the formation of nanostructured system on the formation of surface structures that exhibit outstanding properties. The unresolved problems that should be tackled in better understanding of the effect of nanostructures on properties and performance of oxide semiconductors in solar energy conversion are discussed. This part is summarised by a list of unresolved problems of crucial importance in the formation of systems with enhanced performance. This work also formulates the questions that must be addressed in order to overcome the hurdles in the formation of oxide semiconductors with high performance in water purification and the generation of solar fuel. The research strategy in the development of oxide systems with high performance, including photocatalysts for solar water purification and photoelectrodes for photoelectrochemical water splitting, is considered. The considerations are focused on the systems based on titanium dioxide of different defect disorder as well as its solid solutions and composites.

A Brief Review of Layered Rock Salt Cathode Materials for Lithium Ion Batteries

Nowadays, many researchers have been studying on the layered rock salt-type structure as cathode materials for the lithium ion batteries. LiCoO2 is the most commonly used cathode material but Co is costly and toxic. Thus, alternative cathode materials which are cheaper, safer and having higher capacity are required. Replacing Co with Ni offered higher energy density battery but it raised interlayer mixing or cation disorder that impedes electrochemical properties of batteries. This paper has reviewed some recent research works that have been done to produce better and safer cathode materials from the structural perspective.

Influence of the Grain Size on the Conduction Mechanism of Barium Strontium Titanate Thin Films

Sol-gel barium strontium titanate ( Ba0.6Sr0.4TiO3) thin films with different grain sizes have been successfully fabricated as metal-insulator-metal (MIM) capacitors. The perovskite structure of the material has been confirmed via X-ray diffraction (XRD). In order to correlate the effect of the grain size to the conduction mechanisms of these films, atomic force microscopy (AFM) results are presented. The grain size shows an important effect on the conduction mechanism for the films. The results show that as the grain size increases, both the impedance and the permittivity of the films decrease, whereas the conductivity shows an inverse variation. The Z* plane for all films shows two regions, corresponding to the bulk mechanism and the distribution of the grain boundaries-electrodes conduction process.M´´ versus frequency plots reveal non-Debye relaxation peaks, which are not able to be observed in the e´´ plots. Alternating current (AC) conductivity versus frequency plots show three regions of conduction processes, i.e. a low-frequency region due to direct current (DC) conduction, a mid-frequency region due to translational hopping motion, and a high-frequency region due to localized hopping and/or reorientational motion.

Nano-silver microcavity enhanced UV GaN light emitter

We report results of measurements that help to clarify the role of silver in the reflection of UV emission light from GaN. A GaN as an active layer was sandwiched between two silver metal reflectors. GaN layer on sapphire showed a photoluminescence (PL) peak around 364 nm and its full width half maximum was about 6.7 nm. Two types of microcavity, were fabricated: half-cavity GaN/sapphire/silver and full-cavity silver/GaN/sapphire/silver. Photoluminescence measurements showed a two-fold intensity enhancement in half-cavity back mirror. In the full cavity samples, the amplitude of the photoluminescence is enhanced ten times when we used 50 nm silver as a front mirror. A tremendous more than 16-fold enhancement is obtained when silver mirror of 25 nm was used as a front mirror. The increase in the photoluminescence intensity is explained in terms of competition between increasing absorption in the cavity, silver surface plasmon coupling and increasing optical field-enhancement due to resonator.

Electrochemical Impedance Spectroscopy (EIS) Evaluation of Hydroxyapatite-Coated Magnesium in Different Corrosion Media

Magnesium corrosion has been identified as the main challenge that limits the implementation of this material into various applications, including biomaterials. Simple chemical conversion coatings have been employed in order to minimize the corrosion problems. In this paper, hydroxyapatite-coated magnesium were fabricated by using chemical conversion coatings and the corrosion behaviour of the coated samples were evaluated inside different corrosion media (Ringers, SBF, and PBS) by using electrochemical impedance spectroscopy (EIS). EIS reveals the electrical properties of the coatings towards corrosion attack by the corrosion media. The corrosiveness of the tested solutions was given by (from least to the most aggressive): PBS ˂ SBF ˂ Ringers.

Materialization of MEMS in a collaborative AMBIENCE: A UniMAP experience

Micro Electro Mechanical System (MEMS) is an emerging engineering field that owes so much to material and its processing technologies. It is proven to be capable of enhancing the performance of many devices traditionally produced using conventional microscale manufacturing methods. However, the manufacturing involves requires quite substantial investment in which is normally a major obstacle for universities. Universiti Malaysia Perlis (UniMAP), being a relative new in Malaysia, innovative and collaborative effort are explored with outside organization to overcome this obstacle. Leveraging on its close relationship with the industries, UniMAP collaborated with industries and other critical non-academic partners to plan set-up and launch the first industry driven MEMS based centre of excellent in Malaysian universities. It is named AMBIENCE (Advanced Multidisciplinary MEMS Based Integrated Electronic NCER Centre of Excellence). This paper elaborates in the collaboration history, contribution planning, physical set-up, capabilities and success stories of a new industry driven centre of excellence in UniMAP.

A brief review of calcium phosphate conversion coating on magnesium and its alloys

Recent developments have shown that magnesium is a promising candidate to be used as a biomaterial. Owing to its light weight, biocompatibility and compressive strength comparable with natural bones makes magnesium as an excellent choice for biomaterial. However, high reactivity and low corrosion resistance properties have restricted the application of magnesium as biomaterials. At the moment, several strategies have been developed to solve this problem. Surface modification of magnesium is one of the popular solutions to solve the problem. Among many techniques developed in the surface modification, conversion coating method is one of the simple and effective techniques. From various types of conversion coating, calcium phosphate-based conversion coating is the most suitable for biomedical fields. This paper reviews some studies on calcium phosphate coating on Mg and its alloys via chemical conversion method and discusses some factors determining the coating performance.