Developing the knowledge-based human resources that support the implementation of the National Dual Training System (NDTS): evaluation of TVET teacher's competency at MARA Training Institutions

Development in the world of technical and vocational education and training (TVET) on an ongoing basis is a challenge to the profession of the TVET-teachers to maintain their performance. The ability of teachers to identify the competencies required by their profession is very critical to enable them to make improvements in teaching and learning. For a broader perspective the competency needs of the labour market have to be matched by those developed within the vocational learning processes. Consequently, this study has focused on developing and validating the new empirical based TVET-teacher competency profile and evaluating teacher’s competency. This study combines both quantitative and qualitative research methodology that was designed to answer all the research questions. The new empirical based competency profile development and TVET-teacher evaluation was based upon an instructional design model. In addition, a modified Delphi technique has also been adopted throughout the process. Initially, 98 elements of competencies were listed by expert panel and rated by TVET institutions as important. Then, analysis using manual and statistical procedure found that 112 elements of competencies have emerged from seventeen (17) clusters of competencies. Prior to that, using the preliminary TVET-teacher competency profile, the level of TVETteacher competencies was found to be Proficient and the finding of 112 elements of competencies with 17 clusters was finally used to develop the new empirical based competency profile for MARA TVET-teacher. Mean score analysis of teacher competencies found that there were gaps in teacher competencies between MARA institutions (IKM) and other TVET institutions, where MARA-teacher was significantly better than other TVET teacher. ANOVA and t-test analysis showed that there were significant differences between teacher competencies among all TVET institutions in Malaysia. On the other hand, the study showed that teacher’s age, grade and year of experience are not significant predictors for TVET-teacher competency. In the context of mastering the competency, the study also found that three competencies are classified as most difficult or challenging, twelve competencies are classified as should be improved, and eight competencies are classified as needed to be trained. Lastly, to make NDTS implementation a reality for MARA the new empirical based competency profile and the framework for career development and training pathway were established. This Framework would serve as a significant tool to develop the knowledge based human resources needed. This will ensure that TVET-teachers at MARA are trained to be knowledgeable, competent, and professional and become a pedagogical leader on an ongoing basis towards a world class TVET-education system

Characterization of Thermo-Mechanical Damage in Tin and Sintered Nano-Silver Solders

abstract: Increasing density of microelectronic packages, results in an increase in thermal and mechanical stresses within the various layers of the package. To accommodate the high-performance demands, the materials used in the electronic package would also require improvement. Specifically, the damage that often occurs in solders that function as die-attachment and thermal interfaces need to be addressed. This work evaluates and characterizes thermo-mechanical damage in two material systems – Electroplated Tin and Sintered Nano-Silver solder. Tin plated electrical contacts are prone to formation of single crystalline tin whiskers which can cause short circuiting. A mechanistic model of their formation, evolution and microstructural influence is still not fully understood. In this work, growth of mechanically induced tin whiskers/hillocks is studied using in situ Nano-indentation and Electron Backscatter Diffraction (EBSD). Electroplated tin was indented and monitored in vacuum to study growth of hillocks without the influence of atmosphere. Thermal aging was done to study the effect of intermetallic compounds. Grain orientation of the hillocks and the plastically deformed region surrounding the indent was studied using Focused Ion Beam (FIB) lift-out technique. In addition, micropillars were milled on the surface of electroplated Sn using FIB to evaluate the yield strength and its relation to Sn grain size. High operating temperature power electronics use wide band-gap semiconductor devices (Silicon Carbide/Gallium Nitride). The operating temperature of these devices can exceed 250oC, preventing use of traditional Sn-solders as Thermal Interface materials (TIM). At high temperature, the thermomechanical stresses can severely degrade the reliability and life of the device. In this light, new non-destructive approach is needed to understand the damage mechanism when subjected to reliability tests such as thermal cycling. In this work, sintered nano-Silver was identified as a promising high temperature TIM. Sintered nano-Silver samples were fabricated and their shear strength was evaluated. Thermal cycling tests were conducted and damage evolution was characterized using a lab scale 3D X-ray system to periodically assess changes in the microstructure such as cracks, voids, and porosity in the TIM layer. The evolution of microstructure and the effect of cycling temperature during thermal cycling are discussed.Dissertation/ThesisDoctoral Dissertation Materials Science and Engineering 201

Microstructural Response of Highly Porous Sintered Nano-silver Particle Die Attachments to Thermomechanical Cycling

This paper deals with the performance of sintered nano-silver bonds used as wide-bandgap power module die attachment technology. The paper specifically explores the fine-scale microstructures of highly porous sintered attachments under power cycling to provide a deeper understanding of the significance of porosity as a reliability-related microstructural parameter. Attachments prepared at 220°C using a pressure of 6 MPa for 1 s (parameters known to generate approximately 50% porosity from previous work) and subsequently subjected to 650,000 power cycles between 50°C and 200°C are assessed. A correlative workflow integrating x-ray computed tomography, focused ion beam (FIB) and electron backscatter diffraction (EBSD) data is applied to merge meso- and nanoscale microstructural features to illuminate the degradation mechanisms. The as-sintered Ag layer has a high volume of heterogeneously distributed pores, and consists of randomly oriented equiaxed grains whose sizes vary depending on the local density of the region sampled. Power cycling promotes grain growth and the loss of twin boundaries, and these changes are more pronounced within more dense regions of the Ag attachment. In contrast, the copper substrate appears to undergo some grain refinement, with deformation twins visible within finer-grained zones during power cycling. Cracks, which appear to start off within the Ag layer, propagate across the Ag-Cu boundary and transgranularly through fine-grained regions within the copper with little tortuosity. These observations are discussed within the context of reliability behaviour

Retention and application of Skylab experiences to future programs

The problems encountered and special techniques and procedures developed on the Skylab program are described along with the experiences and practical benefits obtained for dissemination and use on future programs. Three major topics are discussed: electrical problems, mechanical problems, and special techniques. Special techniques and procedures are identified that were either developed or refined during the Skylab program. These techniques and procedures came from all manufacturing and test phases of the Skylab program and include both flight and GSE items from component level to sophisticated spaceflight systems

Antioxidative copper sinter bonding under thermal aging utilizing reduction of cuprous oxide nanoparticles by polyethylene glycol

Durability of sintered Cu joints under thermal aging in the air was investigated for the reduction of Cu₂O using Cu₂O/polyethylene glycol (PEG) mixture. Thermal analysis of the Cu₂O/PEG paste showed that the molecular weight of PEG influences the redox reaction and the subsequent bonding related to the combustion of the reducing organic solvent. Sintered Cu joints using PEG 400 exhibited high joint strength (above 30 MPa) in shear tests, even for the bonding temperature of 280 °C. The sintered Cu joints exhibited slightly increased strength during thermal aging at 250 °C in air, which was also confirmed by the microscale tensile test used for evaluating the fracture behavior of the sintered Cu structure. Microstructural analysis, including the evaluation of the crystal orientation, revealed a small change in the microstructure of sintered joints during aging. Transmission electron microscopy revealed the presence of organic membranes on slightly oxidized sintered Cu grains before thermal aging, and additional oxidation was observed after thermal aging. The progress of sintering during thermal aging in vacuum was different than that in air. It was considered that the formation of a thin Cu₂O layer, controlled by the presence of organic membranes, contributed to the suppression of Cu sintering.The version of record of this article, first published in Journal of Materials Science, is available online at Publisher’s website: https://doi.org/10.1007/s10853-023-08976-

Copper to copper bonding by nano interfaces for fine pitch interconnections and thermal applications

Ever growing demands for portability and functionality have always governed the electronic technology innovations. IC downscaling with Moore s law at IC level and system miniaturization with System-On-Package (SOP) paradigm at system level, have resulted and will continue to result in ultraminiaturized systems with unprecedented functionality at reduced cost. However, system miniaturization poses several electrical and thermal challenges that demand innovative solutions including advanced materials, bonding and assembly techniques. Heterogeneous material and device integration for thermal structures and IC assembly are limited by the bonding technology and the electrical and thermal impedance of the bonding interfaces. Solder - based bonding technology that is prevalent today is a major limitation to future systems. The trend towards miniaturized systems is expected to drive downscaling of IC I/O pad pitches from 40µm to 1- 5µm in future. Solder technology imposes several pitch, processability and cost restrictions at such fine pitches. Furthermore, according to International Technology Roadmap for Semiconductors (ITRS-2006), the supply current in high performance microprocessors is expected to increase to 220 A by 2012. At such supply current, the current density will exceed the maximum allowable current density of solders. The intrinsic delay and electromigration in solders are other daunting issues that become critical at nanometer sized technology nodes. In addition, formation of intermetallics is also a bottleneck that poses significant mechanical issues. Similarly, thermal power dissipation is growing to unprecedented high with a projected power of 198 W by 2008 (ITRS 2006). Present thermal interfaces are not adequate for such high heat dissipation. Recently, copper based thin film bonding has become a promising approach to address the abovementioned challenges. However, copper-copper direct bonding without using solders has not been studied thoroughly. Typically, bonding is carried out at 400oC for 30 min followed by annealing for 30 min. High thermal budget in such process makes it less attractive for integrated systems because of the associated process incompatibilities. Hence, there is a need to develop a novel low temperature copper to copper bonding process. In the present study, nanomaterials - based copper-to-copper bonding is explored and developed as an alternative to solder-based bonding. To demonstrate fine pitch bonding, the patterning of these nanoparticles is crucial. Therefore, two novel self-patterning techniques based on: 1.) Selective wetting and 2.) Selective nanoparticle deposition, are developed to address this challenge. Nanoparticle active layer facilitates diffusion and, thus, a reliable bond can be achieved using less thermal budget. Quantitative characterization of the bonding revealed good metallurgical bonding with very high bond strength. This has been confirmed by several morphological and structural characterizations. A 30-micron pitch IC assembly test vehicle is used to demonstrate fine pitch patternability and bonding. In conclusion, novel nanoparticle synthesis and patterning techniques were developed and demonstrated for low-impedance and low-cost electrical and thermal interfaces.M.S.Committee Chair: Rao R. Tummala; Committee Member: C. P. Wong; Committee Member: P. M. Ra