Ishak Hj. Abd. Azid

Neuro-Genetic Optimization of Temperature Control for a Continuous Flow Polymerase Chain Reaction Microdevice

In this study, a hybridized neuro-genetic optimization methodology realized by embedding finite element analysis (FEA) trained artificial neural networks (ANN) into genetic algorithms (GA), is used to optimize temperature control in a ceramic based continuous flow polymerase chain reaction (CPCR) device. The CPCR device requires three thermally isolated reaction zones of 94 degrees C, 65 degrees C, and 72 degrees C for the denaturing, annealing, and extension processes, respectively, to complete a cycle of polymerase chain reaction. The most important aspect of temperature control in the CPCR is to maintain temperature distribution at each reaction zone with a precision of +/-1 degree C or better, irrespective of changing ambient conditions. Results obtained from the FEA simulation shows good comparison with published experimental work for the temperature control in each reaction zone of the microfluidic channels. The simulation data are then used to train the ANN to predict the temperature distribution of the microfluidic channel for various heater input power and fluid flow rate. Once trained, the ANN analysis is able to predict the temperature distribution in the microchannel in less than 20 min, whereas the FEA simulation takes approximately 7 h to do so. The final optimization of temperature control in the CPCR device is achieved by embedding the trained ANN results as a fitness function into GA. Finally, the GA optimized results are used to build a new FEA model for numerical simulation analysis. The simulation results for the neuro-genetic optimized CPCR model and the initial CPCR model are then compared. The neuro-genetic optimized model shows a significant improvement from the initial model, establishing the optimization methods superiority.

Half cut stress concentration (HCSC) region design on MEMS piezoresistive cantilever for sensitivity enhancement

This work introduced a half cut stress concentration (HCSC) region on the surface of MEMS piezoresistive cantilever in order to improve the sensitivity of a cantilever sensor based on loading/force effect. From the available information, by increasing the stress occurred on the cantilever surface where piezoresistive region place the sensitivity will increase greatly. The designs were simulated using ANSYS 9.0 in order to study the stress distribution and displacement effect. Results obtain for solid cantilever and designed cantilever have been compared. As expected, stress that occurred was increased and highly concentrated at the HCSC region. The cantilever sensitivity also enhances by 4 times. This design of cantilever can obviously improve the sensitivity of the surface stress cantilever.

Development of Human Reliability Model for Evaluating Maintenance Workforce Reliability: A Case Study in Electronic Packaging Industry

Sophisticated and advanced technologies adopted in recent semiconductor industries have grown rapidly to some degree. The complex hardware and software embedded with automation control system and other technological advancement require the need for higher levels of maintenance system. In such technological advancements, one must consider that innovations also require humans in the maintenance system to acquire new skills and knowledge. This however may induce additional probable for human error; which is known as a primary contributor to equipment and plant failures. This paper reviewed several general approaches to the study of human error and the characteristics of work in various industries as a foundation for describing the nature, incidence, and consequences of human error in the maintenance area. The Human Reliability Model (HRrM) which integrates qualitative and quantitative assessments is proposed as a methodology to quantify maintenance workers reliability; or probability the worker successfully accomplishes a maintenance task without performing any erroneous activities. A set of individual factors which may influence to error occurrence is considered as the model variables in evaluating individual maintenance workers. The HRrM model is then been verified and applied in a case study conducted in an electronic packaging industry. The intention of this model is to assist the organization in evaluating and monitoring the maintenance workers performance in terms of their reliability and thus improving the effectiveness of organizations maintenance system.

Investigation of low-pressure bimetallic cobalt-iron catalyst-grown multiwalled carbon nanotubes and their electrical properties

A bimetallic cobalt-iron catalyst was utilized to demonstrate the growth of multiwalled carbon nanotubes (CNTs) at low gas pressure through thermal chemical vapor deposition. The characteristics of multiwalled CNTs were investigated based on the effects of catalyst thickness and gas pressure variation. The results revealed that the average diameter of nanotubes increased with increasing catalyst thickness, which can be correlated to the increase in particle size. The growth rate of the nanotubes also increased significantly by ∼2.5 times with further increment of gas pressure from 0.5 Torr to 1.0 Torr. Rapid growth rate of nanotubes was observed at a catalyst thickness of 6 nm, but it decreased with the increase in catalyst thickness. The higher composition of 50% cobalt in the cobalt-iron catalyst showed improvement in the growth rate of nanotubes and the quality of nanotube structures compared with that of 20% cobalt. For the electrical properties, the measured sheet resistance decreased with the increase in the height of nanotubes because of higher growth rate. This behavior is likely due to the larger contact area of nanotubes, which improved electron hopping from one localized tube to another.

Failure analysis for Copper Wire Bonding process from machine perspective

In fast changing and very competitive industry like semiconductor manufacturing, reliability or probability of failure always has been a crucial part in any processes and operation involving machine and equipment. One of many electronic manufacturing technologies is Wire Bond process, which entails a flexible and an accurate technology because of fast changing market demand for smaller electronic gadgets. Nature of wire bond process which is very delicate, usually makes any failures happen during this type of operation goes unnoticed for sometimes and this situation will cost the company a fortune. This paper aims to discuss equipment reliability based on failure occurrences in wire bond process using copper wire. Copper bonding has received attention because of its low cost, high electrical conductivity and resistance to wire sweep during plastic encapsulation. However, copper have hard properties thus more care is required during bonding as to avoid cratering problem. With the situation, this paper was written to find and analyze machine failure using Failure Mode and Effect Analysis (FMEA) technique to verify machine capability and problems faced when operating using Copper wire. Furthermore, general approach for improvement plan based on type of failure and failure causes are presented as conducted in a semiconductor company in Malaysia. The finding of the study provides evidence that failure analysis is an important task to be done in order to understand machine capability and reliability.

Development of a CMOS-compatible electrostatically actuated diaphragm chamber for micropump application

This paper presents the development of a diaphragm chamber actuated electrostatically utilizing CMOS-compatible silicon micromachining fabrication process. The process consists of six photolithography steps and five chemical vapor depositions. Etching of the sacrificial oxide layer for the diaphragm chamber is achieved using etch-release holes perforated on the diaphragm, similar to via holes used in IC-fabrication method. From the analysis, the best encapsulation has been successfully demonstrated by growing LPCVD silicon nitride of thickness 0.9¿m. Accomplishing this feat enables electrostatically actuated diaphragm chamber to be developed and in particular, will spur advancement in the development of a CMOS-compatible electrostatically actuated diaphragm micropump.

A coupled-field fluid-structure interaction (FSI) simulation of an electrostatically actuated diaphragm valveless micropump (EDVM)

In this study, a novel approach in designing an electrostatically actuated diaphragm valveless micropump (EDVM) based on CMOS-compatible surface micromachining (SMM) fabrication process has been presented. One major advantage of the designed EDVM using SMM process as compared to conventional EDVM fabricated using bulk micromachining process is that the actuation voltage is now applied across the working fluid. The working fluid must be included in the simulations as it will now have a major influence on the response and characteristics of the micropump. In view of that, a coupled-field electro-mechanical-fluidic model of the EDVM has been simulated using MemFSItrade, a fluid-structure interaction (FSI) solver available in CoventorWaretrade software package. Results obtained from the CoventorWaretrade simulations are compared with analytical studies for verification purposes. The designed EDVM with a diaphragm size of 1mm times 1mm times 0.5 mum is able to generate flow rates of up to 10nl/min for a low actuation voltage of 3V.

Artificial Neural Network Trained, Genetic Algorithms Optimized Thermal Energy Storage Heatsinks for Electronics Cooling

A thermal response model for designing thermal energy storage heatsink utilized for electronics cooling is developed in this paper. In this study, thermal energy storage (TES) heatsink made out of aluminum with paraffin as the phase change material (PCM) is considered. By using numerical simulation, stabilization time and maximum operating temperature to transition temperature difference is obtained for varying fin thicknesses, fin height, number of fins and PCM volume. The numerical simulation results were then compared with existing experimental work. The numerical results matched the melting temperature variation obtained by the experimental work. The validated numerical results are then used to train the artificial neural networks (ANN) to predict stabilization time and maximum operating temperature to transition temperature difference for new fin thicknesses, fin height, number of fins and PCM volume. Finally the optimization of the fin thickness, fin height, number of fins and PCM volume of the thermal energy storage heatsink is obtained by embedding the trained ANN as a fitness function into genetic algorithms (GA). The objective of optimization is to maximize stabilization time and to minimize maximum operating temperature to transition temperature difference. Finally the optimized results for the TES heatsink is used to build a new computer model for numerical analysis. The final optimized model results and the validated preliminary model results are then compared. The final results will show a significant improvement from the validated model. Further the study will show that by combining ANN and GA, a superior tool for optimization is realized.Copyright

The design and analysis of a proliferated-membrane of pressure sensor for low pressure applications

In this paper, the effect of incorporating a structure on the top of the membrane layer on the sensitivity and nonlinearity of pressure sensor are analysed using finite finite element analysis (FEA) software, CoventorWare which involved coupled analysis between MemMech and MemPZR. By considering the stress concentration region on the membrane structure, a newly developed design structure of proliferated membrane is compared to the typical structure. The optimum ratio of the beam width-to-the membrane length was obtained at 0.05. Additionally, the ratio of 1:1 in the beam-to-membrane thickness was significant in term of sensitivity. Simulation results showed that the sensitivity of the proliferated-CBM improves 40% whereas the nonlinearity reduces about 33 % in comparison to the flat membrane.

A novel CMOS-compatible fabrication method for development of an electrostatically actuated micropump

This paper presents the development of a novel micropump actuated electrostatically utilizing CMOS-compatible silicon micromachining fabrication process. The fabrication process consists of six photolithography steps and five chemical vapor depositions. Etching of the sacrificial oxide layer for the diaphragm chamber, microchannels and inlet/outlet reservoirs are achieved using etch-release holes perforated on the polysilicon layer, similar to via holes used in IC-fabrication method. The sacrificial oxide etching and encapsulation of the etch-release holes have been successfully accomplished by using BOE etchants for 17 minutes and by growing LPCVD silicon nitride of thickness 0.9 μm respectively. Accomplishing this feat enables CMOS-compatible electrostatically actuated micropump to be developed with potential integration with CMOS-based sensors, readout circuits and packaging, on a single wafer.