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Articles by I. Ahmad
Total Records ( 9 ) for I. Ahmad
  M.K. Md Arshad , A. Jalar , I. Ahmad and G. Omar
  This study reports a number of experiments that were designed to characterize aluminum bond pad surfaces prior to electroless nickel immersion gold (ENIG). In the ENIG process, aluminum bond pads need special treatment to achieve successful nickel deposition and provide reliable interconnection of under bump metallurgy in advanced packaging. During this treatment process, the aluminum pad was cleaned, activated and then coated with a layer of zinc. Systematic study was carried out to determine the best parameters, through multiple and various exposure times of the zincation process and zincation solution concentration effect on the Ni/Au surface roughness and aluminum dissolution rate on the bond pad during multiple zincation process. The ball shear strength was evaluated between eutectic 37Pb/63Sn solder ball and under bump metallurgy (UBM) interfaces across multiple zincation process. Scanning Electron Microscope (SEM), Energy Dispersive X-Ray (EDX), Atomic Force Microscopy (AFM), Focused Ion Beam (FIB) and ball shear tester were used as analytical tools. The results suggest that the multiple zincation process consistently produces a smoother surface of ENIG UBM and consequently provides a better shear strength.
  H. Abdullah , A. Lennie , M.J. Saifuddin and I. Ahmad
  Problem statement: This project discusses on the method to resolve the optical losses problem that have been hindering the totality efficiency of the photovoltaic. Solar cell simulation could be useful for time saving and cost consumption. The Silvaco software is not widely used in designing the 2D solar cell devices because there is lots of 1D, 2D and 3D-simulation beside Silvaco software such as MicroTec, SCAPS-1D. Approach: The different models surface texturing on GaAs solar cell had been simulated by using the Virtual Wafer Fab (VWF), SILVACO software in this project. Results: It was expected that modification of surface texturing might distinctly improved the spectral sensitivity of the photovoltaic by reducing the light reflection and improving the light trapping. There are four models surface texture of photovoltaic devices. It is the simple structure, V-trench structure, fours-sided structure and semi-sphere structure. Hence, the incoming light will hit the GaAs surface several times. Light, which is not absorbed in its first passage through the cell, has the additional opportunities to be absorbed into the cell. It had been shown that modified surface of GaAs solar cell had improved the efficiency up to more than 2% and its quality application performance about 10%. Conclusion: From the simulation result, the V-trench structure is the best surface texture for GaAs solar cell compared to the others, which has Jsc is 3.575 mA cm-2, Voc is 0.807 V and efficiency is 23.07% in 90° incident light.
  S.H. Shah , I. Ahmad and Samiullah
  Field trials were conducted on black cumin (Nigella sativa L.), sprayed with either deionized water (control) or 10-5 M GA3 at 40 (vegetative stage) or 60 (flowering stage) Days after Sowing (DAS) to characterize the effects of hormone treatment on the mentioned parameters and select the suitable growth stage for spray in order to achieve desired results. Shoot length/plant, leaf number/plant, leaf area/plant, branch number/plant, dry weight/plant and accumulations of N, P and K were assayed at 70 DAS. Capsule number/plant, seeds capsule-1, 000 seed weight, seed yield q ha-1, harvest index and Seed Yield Merit (SYM) were analyzed at harvest (130 DAS). It was noted that growth, NPK accumulation and seed yield were maximal when spraying of GA3 was carried out at 40 DAS. However, spraying at 60 DAS was not much effective in terms of the parameters studied. Moreover, there was a significant difference in spray treatments at various growth stages only when GA3 was sprayed and not when water was sprayed.
  I. Ahmad and S. Sulaiman
  Soft tissue simulation is very important in medical simulation and learning procedures. But such simulations require intensive computing. Besides the fact that haptic devices allow touch and feel the virtual objects which increases realism in virtual environment, this imposes much higher requirement on speed and accuracy of computation. The reason is refresh rate for realistic visualization is 25 Hz while the refresh rate of the realistic haptic rendering is 1000 Hz. In this study, an efficient approach for refining a varied area triangular mesh for Visio haptic deformation is presented. The mesh refines adaptively upon contacted by a force feedback device. The proposed algorithm guarantees smooth local deformation as the triangles with larger area are divided more as compared to small area triangles. After subdividing the contacted region, new masses, mass spring constants and dampers are assigned to maintain the original mesh properties. The proposed method is most suitable for manually designed model in 3D modeling software. We integrate our algorithm with the physics based Mass Spring Model for real time deformation.
  H. Abdullah , A. Lennie and I. Ahmad
  In this study, simulated single layer Anti-Reflective Coating (ARC) on silicon solar cell that based on the refractive index limit of silicon dioxide (SiO2), zinc oxide (ZnO) and zinc sulphide (ZnS) are presented. Two simulations of ZnO and ZnS coating were simulated to compare with SiO2 ARC on silicon solar cell surface. These simulations carried out with variable coating thickness that is 50, 60, 70 and 80 nm by using ATLAS simulator. From the simulation obtained, it was found that the value of Voc and Jsc are 397.69 mV and 15.646 mA cm-2, respectively, from silicon solar cell with 0.05 μm SiO2 coating. For the Fill Factor (FF) and power conversion efficiency (η) of this solar cell is 0.758 and 4.72% were computed. As for the ARC simulation, the spectral response of ZnO and ZnS coating was increased around 600 and 700 nm, respectively, which are capable of reducing the refractivity over a wide range of wavelengths compared to SiO2 increased around 400 nm wavelength. This can be concluded that when the refractive index value is high, the available photocurrent also can be high in wide range wavelength and more reducing the refractivity. In ARC analysis, the ZnS coating could perform more efficiency on wide range of wavelength compared to SiO2 and ZnO ARC.
  N. Amin , A.Y. Cheah and I. Ahmad
  This study investigated the plasma cleaning effect on two different commercially available packaging substrates used in the flip chip PBGA substrates for integrated circuit packaging. Investigation and related evaluation have been carried out to determine the wettability of the substrate surface. Contact angles on each substrate are measured by observing the spreading area of the water droplets that referred to the surface tension of the droplets towards the substrate surface. Further investigation has also been conducted by applying plasma cleaning and prebake process before and after flux reflow process together with the staging process. Moreover, substrates are subjected to prebake process followed by plasma cleaning and vice versa. Investigated result shows that plasma cleaning at later time has shown significant improvement (a quantitative 70% decrease in contact angle) in achieving better wettability of the solder bumps on packaging substrates.
  F.Y. Lim , S. Abdullah and I. Ahmad
  In the present analysis, a microchannel heat sinks configuration was simulated by modelling the stacked microchannel heat sinks in a macroscopic scale as if it is a fluid saturated porous medium. The numerical solutions were obtained using the Brinkman and the general heat transfer based formulation. In order to accurately predict the permeability and heat transfer of the stacked microchannels, the simulations were compared with the simulation of a single microchannel heat sink assuming incompressible flow. The advantage of the proposed method is that no assumption on the laminar or fully develop nature of the flow is required. Therefore, this approach can also be used for developing flows in the channel. The important entrance effect which was neglected by previous researchers was also considered in the current simulation. Besides that, in the simulation of large microchannels stack, the proposed method reduce the computing time by approximately one order of magnitude when compared to the conventional approach of simulating individual microchannels. The extended works of the verified porous-media-like-microchannels were combined to be part of a computational domain of a CFD simulation. In the simulations, two cases were conducted under the same pump and the same pressure drops limitations. Good agreements were found with the simulations with discrepancy of 0.25-0.38%. The results were compared with numerical solutions and experimental results from the past reports. The fluid flow and thermal performance of microchannel heat sinks were well predicted with less than 5% discrepancy.
  F. Salehuddin , I. Ahmad , F.A. Hamid and A. Zaharim
  This study reports on an investigation of the effect and optimization of process parameter variability on poly sheet resistance (RS) and leakage current (ILeak) in 45 nm PMOS device. The experimental studies were conducted under varying four process parameters, namely Halo implantation, Source/Drain Implantation, Oxide Growth Temperature and Silicide Anneal Temperature. Taguchi Method was used to determine the settings of process parameters. The level of importance of the process parameters on the poly sheet resistance and leakage current were determined by using Analysis of Variance (ANOVA). Virtual fabrication of the devices was performed by using ATHENA module. While the electrical characterization of the devices was implemented by using ATLAS module. The optimum process parameter combination was obtained by using the analysis of Signal-to-Noise (S/N) ratio. The confirmation tests indicated that it is possible to decrease the poly sheet resistance and leakage current significantly by using the Taguchi method. The results show that the RS and ILeak after optimizations approaches are 67.53 Ω sq-1 and 0.1850 m A μm-1, respectively. In this study, S/D implantation was identified as one of the process parameters that has the strongest effect on the response characteristics.
  M. Ayub , R. Ahmad , A. Tanveer and I. Ahmad
  Response of maize (Zea mays L.) cultivars viz., Sadaf, Sultan, Sarhad White and Golden to two sowing methods, i.e., broadcast and line sowing was studied under field conditions. Significant differences were observed amongst the cultivars for plant height, leaf area per plant, stem diameter, fresh fodder yield and ether extractable fat percentage. Cultivar ‘Sultan’ proved superior to all other cultivars with respect to higher fodder yield of better quality. Plant population was significantly higher under line sowing where as fodder yield and all other yield parameters studied were not significantly affected by sowing methods.
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