Cher Ming Tan - Academia.edu (original) (raw)

Papers by Cher Ming Tan

Applied sciences, Jan 10, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Materials Advances

Novel fracture/fatigue resistant nickel–niobium oxide (crystalline–amorphous) sandwich nanolayers... more Novel fracture/fatigue resistant nickel–niobium oxide (crystalline–amorphous) sandwich nanolayers on a polyimide (PI) substrate as a potential candidate for electrodes or interconnects for flexible electronic or energy devices.

YMER Digital

Electromigration in chip level interconnect is commonly described by atomic drift due to electron... more Electromigration in chip level interconnect is commonly described by atomic drift due to electron-wind force that arises from electron-ion momentum transfer. As an alternative to this model, in early 1980’s, Sah proposed a two dimensional analytical ‘void-surface bond-breaking’ model by dropping the atomic drift term that resulted from electron-wind force (in his book ‘Fundamentals of Solid-State Electronics’) and the rate of change of area of void is computed. Due to the continuous down scaling and evolution of interconnect patterning technologies, the void growth process in modern interconnect becomes more complex and electromigration failures are found to be catastrophic in nature instead of gradual type failures observed in early days. In this work, Sah’s model is revisited from the perspective of its applicability to modern submicron copper interconnects. The electromigration-induced resistance change behavior is analytically derived considering a three-dimensional atomic drift...

Applied Sciences, 2022

A printed circuit board (PCB) is an essential element for practical circuit applications and its ... more A printed circuit board (PCB) is an essential element for practical circuit applications and its failure can inflict large financial costs and even safety concerns, especially if the PCB failure occurs prematurely and unexpectedly. Understanding the failure modes and even the failure mechanisms of a PCB failure are not sufficient to ensure the same failure will not occur again in subsequent operations with different batches of PCBs. The identification of the root cause is crucial to prevent the reoccurrence of the same failure. In this work, a step-by-step approach from customer returned and inventory reproduced boards to the root cause identification is described for an actual industry case where the failure is a PCB burn-out. The failure mechanism is found to be a conductive anodic filament (CAF) even though the PCB is CAF-resistant. The root cause is due to PCB de-penalization. A reliability verification to assure the effectiveness of the corrective action according to the identi...

2017 Annual Reliability and Maintainability Symposium (RAMS), 2017

Automotive Electronics is growing ever since the technological advancement has brought about a re... more Automotive Electronics is growing ever since the technological advancement has brought about a revolution in the Automotive Semiconductor and Telematics industry, especially in the past decade. Utilization of microelectronics and hence circuits' complexity is increasing continuously in automotive industry. Advancement in electronic technology increases the dominance of electronics in automotive markets, and reliability requirements for Automobile Electronics have grown over the past many years. However, the faults and rate of defects is also increasing as indicated by proportion of number of recalls made by large automobile companies, and this poses a difficult ‘Paradox’ to understand and curb. One of the reasons is that the increase in technological advancements makes the vehicles' system more complex and difficult to test for reliability. Also, operating parameters such as temperature, humidity, etc. are increasingly stringent with the continuous development of the electronic systems in vehicles. Short time to market and ineffective design for reliability methodology employed, including various misconceptions on reliability testing, have rendered a lag in providing components and systems that match the increasing reliability requirements for vehicles. Therefore, a call for greater effort in reliability understanding and systematic design for reliability methodology is essential if continuous engagement of advanced electronic technologies is to be continued. The transition from Mechanical Automotive system to Electronics Automotive system and its effect on the Automotive industry is discussed in this work. The fact that technological benefits are not helping in improving reliability of the Automotive Electronics system is explained by studying the worldwide automotive recalls and the Paradox of Automotive Electronics Reliability is presented and explained.

Light-Emitting Diodes - New Perspectives [Working Title]

Applications of LEDs have increased significantly, and increasing outdoor applications are observ... more Applications of LEDs have increased significantly, and increasing outdoor applications are observed. Some outdoor applications require high reliability as their failure can lead to hazardous consequences. Examples are their applications in automotive, street lamp lighting etc. To ensure the reliability of LEDs in outdoor applications, reliability test that include humidity on the LEDs must be done. However, it is found that accelerated life test of LEDs at high humidity level cannot be extrapolated to standard condition of lower humidity as the mechanism of degradation depends critically on humidity level. In fact, the degradation of LEDs in outdoor applications is mainly due to the degradation of their encapsulation and housing materials (or called packaging material as a whole) instead of the semiconductor chip itself. The decrease in lumen is the results of crack and discoloration of the LED packaging material. Detail understanding of the failure physics of the packaging material...

Applied Sciences, 2021

Prompt gamma imaging is one of the emerging techniques used in proton therapy for in-vivo range v... more Prompt gamma imaging is one of the emerging techniques used in proton therapy for in-vivo range verification. Prompt gamma signals are generated during therapy due to the nuclear interaction between beam particles and nuclei of the tissue that is detected and processed in order to obtain the position and energy of the event so that the benefits of Bragg’s peak can be fully utilized. This work aims to develop a gallium nitride (GaN)-based readout system for position-sensitive detectors. An operational amplifier is the module most used in such a system to process the detector signal, and a GaN-based operational amplifier (OPA) is designed and simulated in LTSpice. The designed circuit had an open-loop gain of 70 dB and a unity gain frequency of 34 MHz. The slew rate of OPA was 20 V/μs and common mode rejection ratio was 84.2 dB. A simulation model of the readout circuit system using the GaN-based operational amplifier was also designed, and the result showed that the system can succes...

Sensors and Materials, 2021

Advances in semiconductor technology have enhanced the functionality of sensor arrays with reduce... more Advances in semiconductor technology have enhanced the functionality of sensor arrays with reduced feature sizes. Owing to the spread of the Internet of Things, sensors can now be found in many applications operating in various environments. Proton and neutron radiation are always present around us but have not been detrimental to electronics at sea level. With the decreasing size of transistors and sensor elements and the increasing density of transistors in ICs of sensors and actuators, the effect of radiation on the reliability of semiconductor devices, sensors, and their electronic circuits (collectively called sensing systems) is no longer negligible, even at sea level. However, the knowledge of radiation physics and that of semiconductor physics are very different, and merging of the two sets of knowledge is necessary to evaluate the effect of radiation on the reliability of sensing systems. In this work, we summarize the extensive studies of the effects of radiation on semiconductor devices from space and avionics investigations, and we apply their results to study the radiation reliability of sensing systems in standard industry applications. In this work, we also illustrate how one can perform radiation reliability analysis for electronics in a proximity sensor, which we investigated by performing radiation experiments.

2007 IEEE International Conference on Communications, 2007

Precise measurement and modelling of the Direction of Arrival (DoA) and Direction of Departure (D... more Precise measurement and modelling of the Direction of Arrival (DoA) and Direction of Departure (DoD) in the Multiple-Input Multiple-Output (MIMO) channel based on their correlation properties and joint distributions have not been investigated properly. Our main contribution in this paper is two fold. Firstly, based on a modified Gumbel's bivariate exponential approach, we propose a generic indoor MIMO channel modelling framework particularly for the double-directional 'general trend' that has been observed in these dual-spatial domains. Secondly, we propose a transformation technique to generate the pair wise DoA and DoD components incorporating the correlation properties of the variates around the full azimuth range. Results show that the newly proposed modelling approaches provide a good match to the real data, offering an alternative hassle-free method to generate realistic directional-based stochastic MIMO channel responses in different indoor environments.

10th Electronics Packaging Technology Conference, EPTC 2008, 2008

explain the physical mechanism during creep. Both Arrhenius The paper presents improved constitut... more explain the physical mechanism during creep. Both Arrhenius The paper presents improved constitutive models for and hyperbolic models ignore the microstructure change SnAgCu solder. In the present study, the constitutive behavior during the creep deformation. In fact, microstructure such as s for creep perfonance of 95.8Sn-3.5Ag-0.7Cu lead-free solder dislocation structures and crystallographic texture in materials for creep performance of 95.85n-3.5Ag-0.7Cwu lead-free solder ' was investigated. The secondary creep stage was focused on. strongly affect inelastic deformation [11]. This leads to the It is shown that the stress exponent n can be well-defined into conclusion that a model of creep deformation behavior must two stress regimes: low stress and high stress. A new consider not only the macroscopic deformation behavior but constitutive model, which considered back stress, is proposed also the dislocation structures.

Archives of Physics Research, 2018

Moisture is found to be a major cause of LED lumen degradation along with various other factors. ... more Moisture is found to be a major cause of LED lumen degradation along with various other factors. In this work, a method is proposed to prevent moisture from penetrating into the LED’s internal structure by having diamond like carbon (DLC) films coated on the LED’s encapsulant as a moisture barrier sheet via RF sputtering system at room temperature. However, we found that the DLC coating is not suitable for this role as it underwent structural changes with time that lower its moisture resistance ability. The LED encapsulant expansion is found be the reason for the DLC’s structural changes. Consequently, higher lumen degradation is observed for LEDs coated with DLC coating as compared to its non- DLC counterpart.

International Series on Advances in Solid State Electronics and Technology, 2010

Page 1. ASSET rnlematiotial S*riea on Advances in Solid Stale Electronics and Technology Founding... more Page 1. ASSET rnlematiotial S*riea on Advances in Solid Stale Electronics and Technology Founding Eclilcr: Chili-Tartg fi.ih ELECTROMIGRATION IN ULSI INTERCONNECTIONS etc iim ii IHt in Cher Ming Tan World Scientific Page 2. ...

Progress In Electromagnetics Research Letters, 2019

Advancements in functionalities and operating frequencies of integrated circuits lead to the nece... more Advancements in functionalities and operating frequencies of integrated circuits lead to the necessity to study Electromagnetic Compatibility/Electromagnetic Emissions (EMC/EMEs) from these devices. In this work, a methodology is developed, which combines near field electromagnetic measurements and 3D layout simulation of an Integrated Circuit (IC), to identify the sources of EME from a commercial IC. This methodology can help to narrow down the area of key importance with respect to EME sources, instead of the entire IC, before it is fabricated. Consequently, IC designers can optimize their design to minimize the EME before fabrication, saving cost and time significantly.

Scientific Reports, 2018

Increasing phosphor layer thickness and concentration can enhance the lumen flux of white LED (W-... more Increasing phosphor layer thickness and concentration can enhance the lumen flux of white LED (W-LED). In this work, we found that increasing the phosphor layer thickness and concentration can increase its temperature, and there is also a maximum thickness and concentration beyond which their increase will not lead to lumen increase, but only temperature increase. Higher thickness and higher concentration also results in warm light instead of White light. The maximum thickness and concentration are found to be limited by the scattering of light rays with higher % decrease of blue light rays than the yellow light rays. The results obtained in this work can also be used to compute the temperature and thermo-mechanical stress distribution of an encapsulated LED, demonstrating its usefulness to the design of encapsulated LED packages. Simulation software like ANSYS and TracePro are used extensively to verify the root cause mechanisms.

Applied Sciences, 2016

Flip chip technology has been widely adopted in modern power light-emitting diode (LED) fabricati... more Flip chip technology has been widely adopted in modern power light-emitting diode (LED) fabrications and its output efficiency is closely related to the submount material properties. Here, we present the electrical, optical and thermal properties of flip chip light-emitting diodes mounted on transparent sapphire and borosilicate glass which have shown a higher output luminous flux when compared to the traditional non-transparent mounted LEDs. Exhibiting both better thermal conductivity and good optical transparency, flip chip LEDs with a sapphire submount showed superior performance when compared to the non-transparent silicon submount ones, and also showed better optical performance than the flip chip LEDs mounted on transparent but poor-thermal-conducting glass substrates. The correspondent analysis was carried out using ANSYS 14 to compare the experimental thermal imaging with the simulation results. TracePro software was also used to check the output luminous flux dependency on different LED mounting designs.

Applied Sciences, 2021

Single event upset, or Single Event Effect (SEE) is increasingly important as semiconductor devic... more Single event upset, or Single Event Effect (SEE) is increasingly important as semiconductor devices are entering into nano-meter scale. The Linear Energy Transfer (LET) concept is commonly used to estimate the rate of SEE. The SEE, however, should be related to energy deposition of each stochastic event, but not LET which is a non-stochastic quantity. Instead, microdosimetry, which uses a lineal calculation of energy lost per step for each specific track, should be used to replace LET to predict microelectronic failure from SEEs. Monte Carlo simulation is used for the demonstration, and there are several parameters needed to optimise for SEE simulation, such as the target size, physical models and scoring techniques. We also show the thickness of the sensitive volume, which also correspond to the size of a device, will change the spectra of lineal energy. With a more comprehensive Monte Carlo simulation performed in this work, we also show and explain the differences in our results ...

Ekspolatacja i Niezawodnosc - Maintenance and Reliability, 2019

Optimal maintenance strategy On medical instruments used fOr haemOdialysis prOcess Optymalna stra... more Optimal maintenance strategy On medical instruments used fOr haemOdialysis prOcess Optymalna strategia kOnserwacji urządzeń medycznych wykOrzystywanych w prOcesie hemOdializy Haemodialysis machines are one of the important medical equipment which is used to treat renal failures and minimum downtimes are thus essential. Uninterrupted and constant use of these machines in hospitals worldwide makes them vulnerable to failures if not maintained properly. Consequently, the maintenance cost for dialysis machine is high. A method to implement a cost effective maintenance strategy is demonstrated in this work. Root Cause Based Maintenance (RCBM) strategy is employed at the component level to optimize the Reliability Based Maintenance schedules derived from the existing maintenance and failure data. In order to minimize the average cost of maintenance for Haemodialysis machines and ensure their high operational availability, a Cost-Model is derived, and Genetic Algorithm is employed for optimization in this work. The application of RCBM strategy results in cost saving of about 60% of the cost incurred using current maintenance scheme. Statistical and optimization calculations are performed using Reliasoft's Weibull++ and MATLAB tools respectively.

Scientific Reports, 2017

Growth mechanism for synthesizing PVD based Graphene using Amorphous Carbon, catalyzed by Copper ... more Growth mechanism for synthesizing PVD based Graphene using Amorphous Carbon, catalyzed by Copper is investigated in this work. Different experiments with respect to Amorphous Carbon film thickness, annealing time and temperature are performed for the investigation. Copper film stress and its effect on hydrogen diffusion through the film grain boundaries are found to be the key factors for the growth mechanism, and supported by our Finite Element Modeling. Low temperature growth of Graphene is achieved and the proposed growth mechanism is found to remain valid at low temperatures. Graphene has been a material of great interest since its conception due to its extraordinary properties such as its single atomic thickness 1 , high current density tolerance 2 of about 10 8 A/cm 2 , extremely high mobility 3,4 of about 15,000 cm 2 /Vs, high thermal conductivity 5 in the order of 5 × 10 3 W/mK, high optical transmittance of about 97% within the visible light wavelength-range of 400 to 700 nm 6 , high mechanical strength with breaking strength of 42 Nm −1 and second and third-order elastic stiffness of 340 Nm −1 and − 690 Nm −1 respectively 7. Over a decade, Graphene synthesis methods have witnessed many pathways in order to produce high quality Graphene with a high degree of coverage area. Currently, the Graphene synthesis method used is Chemical vapor deposition (CVD) technique 8-11 which produces uniform, large area, relatively low defect Graphene films and is known to be the cheapest for mass production and can meet the semiconductor industry requirement 11. Growth of Graphene on Copper using CVD has been demonstrated by Li et al. 11,12 and others 13,14. However, this method uses expensive carbon source which is also wasted considerably during chamber cleaning. This method also have no control over number of layers of synthesized Graphene when it comes to few-layered and multi-layered graphene growth. On the other hand, a simpler and low cost technique to obtain non-transferable Graphene using amorphous carbon as solid source and Nickel or Cobalt thin film as catalyst annealed at elevated temperatures has been reported 15-17. This technique can be instrumental in controlling the number of Graphene layers, eliminates the need for Graphene transfer and is economical as it uses amorphous carbon as the carbon source. Non-transferable Graphene synthesis is important especially for ULSI Interconnects which are used in BEOL (back-end-of-line) process and transfer of Graphene is quite infeasible. Moreover, the transfer of Graphene introduces many structural inhomogeneities which causes degradation of properties of graphene such as the mobility, electrical and thermal conductivity etc 18-20. However, such Graphene synthesis method was reported to be not possible with Copper due to the very low solubility of Carbon in Copper 16,17. As the applications of Copper material is vast and important, such as printed circuit boards, transmission wires and cables, its application in ULSI interconnects, etc, the growth of Graphene on Copper (Cu) can overcome

The use of general descriptive names, registered names, trademarks, service marks, etc. in this p... more The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.

Applied sciences, Jan 10, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Materials Advances

Novel fracture/fatigue resistant nickel–niobium oxide (crystalline–amorphous) sandwich nanolayers... more Novel fracture/fatigue resistant nickel–niobium oxide (crystalline–amorphous) sandwich nanolayers on a polyimide (PI) substrate as a potential candidate for electrodes or interconnects for flexible electronic or energy devices.

YMER Digital

Electromigration in chip level interconnect is commonly described by atomic drift due to electron... more Electromigration in chip level interconnect is commonly described by atomic drift due to electron-wind force that arises from electron-ion momentum transfer. As an alternative to this model, in early 1980’s, Sah proposed a two dimensional analytical ‘void-surface bond-breaking’ model by dropping the atomic drift term that resulted from electron-wind force (in his book ‘Fundamentals of Solid-State Electronics’) and the rate of change of area of void is computed. Due to the continuous down scaling and evolution of interconnect patterning technologies, the void growth process in modern interconnect becomes more complex and electromigration failures are found to be catastrophic in nature instead of gradual type failures observed in early days. In this work, Sah’s model is revisited from the perspective of its applicability to modern submicron copper interconnects. The electromigration-induced resistance change behavior is analytically derived considering a three-dimensional atomic drift...

Applied Sciences, 2022

A printed circuit board (PCB) is an essential element for practical circuit applications and its ... more A printed circuit board (PCB) is an essential element for practical circuit applications and its failure can inflict large financial costs and even safety concerns, especially if the PCB failure occurs prematurely and unexpectedly. Understanding the failure modes and even the failure mechanisms of a PCB failure are not sufficient to ensure the same failure will not occur again in subsequent operations with different batches of PCBs. The identification of the root cause is crucial to prevent the reoccurrence of the same failure. In this work, a step-by-step approach from customer returned and inventory reproduced boards to the root cause identification is described for an actual industry case where the failure is a PCB burn-out. The failure mechanism is found to be a conductive anodic filament (CAF) even though the PCB is CAF-resistant. The root cause is due to PCB de-penalization. A reliability verification to assure the effectiveness of the corrective action according to the identi...

2017 Annual Reliability and Maintainability Symposium (RAMS), 2017

Automotive Electronics is growing ever since the technological advancement has brought about a re... more Automotive Electronics is growing ever since the technological advancement has brought about a revolution in the Automotive Semiconductor and Telematics industry, especially in the past decade. Utilization of microelectronics and hence circuits' complexity is increasing continuously in automotive industry. Advancement in electronic technology increases the dominance of electronics in automotive markets, and reliability requirements for Automobile Electronics have grown over the past many years. However, the faults and rate of defects is also increasing as indicated by proportion of number of recalls made by large automobile companies, and this poses a difficult ‘Paradox’ to understand and curb. One of the reasons is that the increase in technological advancements makes the vehicles' system more complex and difficult to test for reliability. Also, operating parameters such as temperature, humidity, etc. are increasingly stringent with the continuous development of the electronic systems in vehicles. Short time to market and ineffective design for reliability methodology employed, including various misconceptions on reliability testing, have rendered a lag in providing components and systems that match the increasing reliability requirements for vehicles. Therefore, a call for greater effort in reliability understanding and systematic design for reliability methodology is essential if continuous engagement of advanced electronic technologies is to be continued. The transition from Mechanical Automotive system to Electronics Automotive system and its effect on the Automotive industry is discussed in this work. The fact that technological benefits are not helping in improving reliability of the Automotive Electronics system is explained by studying the worldwide automotive recalls and the Paradox of Automotive Electronics Reliability is presented and explained.

Light-Emitting Diodes - New Perspectives [Working Title]

Applications of LEDs have increased significantly, and increasing outdoor applications are observ... more Applications of LEDs have increased significantly, and increasing outdoor applications are observed. Some outdoor applications require high reliability as their failure can lead to hazardous consequences. Examples are their applications in automotive, street lamp lighting etc. To ensure the reliability of LEDs in outdoor applications, reliability test that include humidity on the LEDs must be done. However, it is found that accelerated life test of LEDs at high humidity level cannot be extrapolated to standard condition of lower humidity as the mechanism of degradation depends critically on humidity level. In fact, the degradation of LEDs in outdoor applications is mainly due to the degradation of their encapsulation and housing materials (or called packaging material as a whole) instead of the semiconductor chip itself. The decrease in lumen is the results of crack and discoloration of the LED packaging material. Detail understanding of the failure physics of the packaging material...

Applied Sciences, 2021

Prompt gamma imaging is one of the emerging techniques used in proton therapy for in-vivo range v... more Prompt gamma imaging is one of the emerging techniques used in proton therapy for in-vivo range verification. Prompt gamma signals are generated during therapy due to the nuclear interaction between beam particles and nuclei of the tissue that is detected and processed in order to obtain the position and energy of the event so that the benefits of Bragg’s peak can be fully utilized. This work aims to develop a gallium nitride (GaN)-based readout system for position-sensitive detectors. An operational amplifier is the module most used in such a system to process the detector signal, and a GaN-based operational amplifier (OPA) is designed and simulated in LTSpice. The designed circuit had an open-loop gain of 70 dB and a unity gain frequency of 34 MHz. The slew rate of OPA was 20 V/μs and common mode rejection ratio was 84.2 dB. A simulation model of the readout circuit system using the GaN-based operational amplifier was also designed, and the result showed that the system can succes...

Sensors and Materials, 2021

Advances in semiconductor technology have enhanced the functionality of sensor arrays with reduce... more Advances in semiconductor technology have enhanced the functionality of sensor arrays with reduced feature sizes. Owing to the spread of the Internet of Things, sensors can now be found in many applications operating in various environments. Proton and neutron radiation are always present around us but have not been detrimental to electronics at sea level. With the decreasing size of transistors and sensor elements and the increasing density of transistors in ICs of sensors and actuators, the effect of radiation on the reliability of semiconductor devices, sensors, and their electronic circuits (collectively called sensing systems) is no longer negligible, even at sea level. However, the knowledge of radiation physics and that of semiconductor physics are very different, and merging of the two sets of knowledge is necessary to evaluate the effect of radiation on the reliability of sensing systems. In this work, we summarize the extensive studies of the effects of radiation on semiconductor devices from space and avionics investigations, and we apply their results to study the radiation reliability of sensing systems in standard industry applications. In this work, we also illustrate how one can perform radiation reliability analysis for electronics in a proximity sensor, which we investigated by performing radiation experiments.

2007 IEEE International Conference on Communications, 2007

Precise measurement and modelling of the Direction of Arrival (DoA) and Direction of Departure (D... more Precise measurement and modelling of the Direction of Arrival (DoA) and Direction of Departure (DoD) in the Multiple-Input Multiple-Output (MIMO) channel based on their correlation properties and joint distributions have not been investigated properly. Our main contribution in this paper is two fold. Firstly, based on a modified Gumbel's bivariate exponential approach, we propose a generic indoor MIMO channel modelling framework particularly for the double-directional 'general trend' that has been observed in these dual-spatial domains. Secondly, we propose a transformation technique to generate the pair wise DoA and DoD components incorporating the correlation properties of the variates around the full azimuth range. Results show that the newly proposed modelling approaches provide a good match to the real data, offering an alternative hassle-free method to generate realistic directional-based stochastic MIMO channel responses in different indoor environments.

10th Electronics Packaging Technology Conference, EPTC 2008, 2008

explain the physical mechanism during creep. Both Arrhenius The paper presents improved constitut... more explain the physical mechanism during creep. Both Arrhenius The paper presents improved constitutive models for and hyperbolic models ignore the microstructure change SnAgCu solder. In the present study, the constitutive behavior during the creep deformation. In fact, microstructure such as s for creep perfonance of 95.8Sn-3.5Ag-0.7Cu lead-free solder dislocation structures and crystallographic texture in materials for creep performance of 95.85n-3.5Ag-0.7Cwu lead-free solder ' was investigated. The secondary creep stage was focused on. strongly affect inelastic deformation [11]. This leads to the It is shown that the stress exponent n can be well-defined into conclusion that a model of creep deformation behavior must two stress regimes: low stress and high stress. A new consider not only the macroscopic deformation behavior but constitutive model, which considered back stress, is proposed also the dislocation structures.

Archives of Physics Research, 2018

Moisture is found to be a major cause of LED lumen degradation along with various other factors. ... more Moisture is found to be a major cause of LED lumen degradation along with various other factors. In this work, a method is proposed to prevent moisture from penetrating into the LED’s internal structure by having diamond like carbon (DLC) films coated on the LED’s encapsulant as a moisture barrier sheet via RF sputtering system at room temperature. However, we found that the DLC coating is not suitable for this role as it underwent structural changes with time that lower its moisture resistance ability. The LED encapsulant expansion is found be the reason for the DLC’s structural changes. Consequently, higher lumen degradation is observed for LEDs coated with DLC coating as compared to its non- DLC counterpart.

International Series on Advances in Solid State Electronics and Technology, 2010

Page 1. ASSET rnlematiotial S*riea on Advances in Solid Stale Electronics and Technology Founding... more Page 1. ASSET rnlematiotial S*riea on Advances in Solid Stale Electronics and Technology Founding Eclilcr: Chili-Tartg fi.ih ELECTROMIGRATION IN ULSI INTERCONNECTIONS etc iim ii IHt in Cher Ming Tan World Scientific Page 2. ...

Progress In Electromagnetics Research Letters, 2019

Advancements in functionalities and operating frequencies of integrated circuits lead to the nece... more Advancements in functionalities and operating frequencies of integrated circuits lead to the necessity to study Electromagnetic Compatibility/Electromagnetic Emissions (EMC/EMEs) from these devices. In this work, a methodology is developed, which combines near field electromagnetic measurements and 3D layout simulation of an Integrated Circuit (IC), to identify the sources of EME from a commercial IC. This methodology can help to narrow down the area of key importance with respect to EME sources, instead of the entire IC, before it is fabricated. Consequently, IC designers can optimize their design to minimize the EME before fabrication, saving cost and time significantly.

Scientific Reports, 2018

Increasing phosphor layer thickness and concentration can enhance the lumen flux of white LED (W-... more Increasing phosphor layer thickness and concentration can enhance the lumen flux of white LED (W-LED). In this work, we found that increasing the phosphor layer thickness and concentration can increase its temperature, and there is also a maximum thickness and concentration beyond which their increase will not lead to lumen increase, but only temperature increase. Higher thickness and higher concentration also results in warm light instead of White light. The maximum thickness and concentration are found to be limited by the scattering of light rays with higher % decrease of blue light rays than the yellow light rays. The results obtained in this work can also be used to compute the temperature and thermo-mechanical stress distribution of an encapsulated LED, demonstrating its usefulness to the design of encapsulated LED packages. Simulation software like ANSYS and TracePro are used extensively to verify the root cause mechanisms.

Applied Sciences, 2016

Flip chip technology has been widely adopted in modern power light-emitting diode (LED) fabricati... more Flip chip technology has been widely adopted in modern power light-emitting diode (LED) fabrications and its output efficiency is closely related to the submount material properties. Here, we present the electrical, optical and thermal properties of flip chip light-emitting diodes mounted on transparent sapphire and borosilicate glass which have shown a higher output luminous flux when compared to the traditional non-transparent mounted LEDs. Exhibiting both better thermal conductivity and good optical transparency, flip chip LEDs with a sapphire submount showed superior performance when compared to the non-transparent silicon submount ones, and also showed better optical performance than the flip chip LEDs mounted on transparent but poor-thermal-conducting glass substrates. The correspondent analysis was carried out using ANSYS 14 to compare the experimental thermal imaging with the simulation results. TracePro software was also used to check the output luminous flux dependency on different LED mounting designs.

Applied Sciences, 2021

Single event upset, or Single Event Effect (SEE) is increasingly important as semiconductor devic... more Single event upset, or Single Event Effect (SEE) is increasingly important as semiconductor devices are entering into nano-meter scale. The Linear Energy Transfer (LET) concept is commonly used to estimate the rate of SEE. The SEE, however, should be related to energy deposition of each stochastic event, but not LET which is a non-stochastic quantity. Instead, microdosimetry, which uses a lineal calculation of energy lost per step for each specific track, should be used to replace LET to predict microelectronic failure from SEEs. Monte Carlo simulation is used for the demonstration, and there are several parameters needed to optimise for SEE simulation, such as the target size, physical models and scoring techniques. We also show the thickness of the sensitive volume, which also correspond to the size of a device, will change the spectra of lineal energy. With a more comprehensive Monte Carlo simulation performed in this work, we also show and explain the differences in our results ...

Ekspolatacja i Niezawodnosc - Maintenance and Reliability, 2019

Optimal maintenance strategy On medical instruments used fOr haemOdialysis prOcess Optymalna stra... more Optimal maintenance strategy On medical instruments used fOr haemOdialysis prOcess Optymalna strategia kOnserwacji urządzeń medycznych wykOrzystywanych w prOcesie hemOdializy Haemodialysis machines are one of the important medical equipment which is used to treat renal failures and minimum downtimes are thus essential. Uninterrupted and constant use of these machines in hospitals worldwide makes them vulnerable to failures if not maintained properly. Consequently, the maintenance cost for dialysis machine is high. A method to implement a cost effective maintenance strategy is demonstrated in this work. Root Cause Based Maintenance (RCBM) strategy is employed at the component level to optimize the Reliability Based Maintenance schedules derived from the existing maintenance and failure data. In order to minimize the average cost of maintenance for Haemodialysis machines and ensure their high operational availability, a Cost-Model is derived, and Genetic Algorithm is employed for optimization in this work. The application of RCBM strategy results in cost saving of about 60% of the cost incurred using current maintenance scheme. Statistical and optimization calculations are performed using Reliasoft's Weibull++ and MATLAB tools respectively.

Scientific Reports, 2017

Growth mechanism for synthesizing PVD based Graphene using Amorphous Carbon, catalyzed by Copper ... more Growth mechanism for synthesizing PVD based Graphene using Amorphous Carbon, catalyzed by Copper is investigated in this work. Different experiments with respect to Amorphous Carbon film thickness, annealing time and temperature are performed for the investigation. Copper film stress and its effect on hydrogen diffusion through the film grain boundaries are found to be the key factors for the growth mechanism, and supported by our Finite Element Modeling. Low temperature growth of Graphene is achieved and the proposed growth mechanism is found to remain valid at low temperatures. Graphene has been a material of great interest since its conception due to its extraordinary properties such as its single atomic thickness 1 , high current density tolerance 2 of about 10 8 A/cm 2 , extremely high mobility 3,4 of about 15,000 cm 2 /Vs, high thermal conductivity 5 in the order of 5 × 10 3 W/mK, high optical transmittance of about 97% within the visible light wavelength-range of 400 to 700 nm 6 , high mechanical strength with breaking strength of 42 Nm −1 and second and third-order elastic stiffness of 340 Nm −1 and − 690 Nm −1 respectively 7. Over a decade, Graphene synthesis methods have witnessed many pathways in order to produce high quality Graphene with a high degree of coverage area. Currently, the Graphene synthesis method used is Chemical vapor deposition (CVD) technique 8-11 which produces uniform, large area, relatively low defect Graphene films and is known to be the cheapest for mass production and can meet the semiconductor industry requirement 11. Growth of Graphene on Copper using CVD has been demonstrated by Li et al. 11,12 and others 13,14. However, this method uses expensive carbon source which is also wasted considerably during chamber cleaning. This method also have no control over number of layers of synthesized Graphene when it comes to few-layered and multi-layered graphene growth. On the other hand, a simpler and low cost technique to obtain non-transferable Graphene using amorphous carbon as solid source and Nickel or Cobalt thin film as catalyst annealed at elevated temperatures has been reported 15-17. This technique can be instrumental in controlling the number of Graphene layers, eliminates the need for Graphene transfer and is economical as it uses amorphous carbon as the carbon source. Non-transferable Graphene synthesis is important especially for ULSI Interconnects which are used in BEOL (back-end-of-line) process and transfer of Graphene is quite infeasible. Moreover, the transfer of Graphene introduces many structural inhomogeneities which causes degradation of properties of graphene such as the mobility, electrical and thermal conductivity etc 18-20. However, such Graphene synthesis method was reported to be not possible with Copper due to the very low solubility of Carbon in Copper 16,17. As the applications of Copper material is vast and important, such as printed circuit boards, transmission wires and cables, its application in ULSI interconnects, etc, the growth of Graphene on Copper (Cu) can overcome

The use of general descriptive names, registered names, trademarks, service marks, etc. in this p... more The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.