Papers by Author: Azman Jalar

Abstract: Average roughness is an increasingly important method in material sciences. The searching for a possible correlation between average roughness and impact energy are current interest. This paper present the results of an experimentally study made on the correlation between the average roughness and the impact energy in aluminum alloy by using scatted diagram. The impact energy of aluminum alloy was obtained by using Charpy Impact Test. The micrographs of fractured aluminum alloy were analyzed with the IFM (Infinite Focus Measurement) profile to determine the parameter of average roughness. The result shows the relationship maybe established between average roughness and impact energy.

Abstract: The changes of microstructure in eutectic sn-3.8ag-0.7cu during moderate current stressing have been investigated. The current stressing values were 102 and 103 a/cm2. The tests were carried out for 24, 216, 576 and 1008 hours. Sn-rich phases and eutectic phases appear immediately after soldering process. However, thermal rise during current stressing has coarsened sn-rich phases and altered the microstructure of the solder. Higher current density leads to larger snrich phase coarsening. The microstructures for current stressing test were also compared with the series of microstructure for isothermal annealing test since there is similarity in coarsening effect for both tests. The effect of thermal rising during current stressing as well as during isothermal annealing to sn-rich phase coarsening is established and will be discussed further.

Abstract: The corrosion of four Fe-Cr alloys (Cr: 9, 12, 20, and 25%) with different Cr contents were subjected to cyclic oxidation furnace in Ar-10%O2 atmosphere at 950oC for 120 h. The samples after oxidation were investigated by using X-ray diffraction (XRD), optical metallography and SEM/EDS. The results indicated that increasing Cr content reduced the oxidation rate and the scale cracking. Alloys with less Cr content occurred breakaway oxidation due to formation of Fe-rich oxide scale. However, a thin protective chromia scale was observed on alloys with Cr > 20%. The corrosion behaviour on Fe-Cr alloy was then discussed based on experimental observation.

Abstract: Several different groups of filler metal are known to be compatible in welding of AA6xxx series. The aim of this investigation is to study the effects of different filler alloys toward mechanical properties and microstructure of welded AA6061 aluminium alloy using gas metal arc welding. Single V butt joint configuration has been used for joining the plate’s. Butt-joint welds were made on 6 mm thick plates using 21 – 22 V arc voltage. Tensile test was carried out using 100kN, electro-mechanical controlled hydraulic Instron 8801 universal testing machine. The results showed that the yield strength of base metal were 330 MPa and while the yield strength of ER5356 joints and ER4043 joints were 200 MPa and 235 MPa, respectively. The difference properties of strength in both weld metal was due to the difference major element in the both filler composition. The amount of silicon content in ER4043(Al-Si5%) filler is believed to play a role in the mechanical strength on weld metal. Microstructural examination was carried out using a light optical and electron microscope. The different filler alloys give different weld metal microstructure.

Abstract: The Reduced Modulus value for the bonded Au ball bond that have undergone three different time intervals of high temperature storage (HTS) have been obtained by using nanoindentation test. Twelve indentations have been made at three different locations (Au, IMC and Si area) across the bonded ball bonds to evaluate the variation of Reduced Modulus with the location of indentation. It was shown that the Reduced Modulus value for the indentations at IMC area is increased with the increment of HTS time interval. It was also observed that the Reduced Modulus at the Au area was increased with the increment of the HTS exposure time. No particular pattern was noted to describe the changes of Reduced Modulus with the location of the indentations that have been made. It was also found that the average Reduced Modulus for Au obtained through nanoindentation with value of 107 GPa has higher value compared to that of the Young’s modulus value obtained through actual tensile test with value of 79 GPa.

Abstract: AA6061 Aluminum alloy welded joint using two different filler metals were studied by using X-ray CT-Scan. The filler metals ER 4043 and ER 5356 were used in this present work in order to investigate the effect of using different filler metals on the welded joint quality of AA 6061 aluminum alloy in welded zone microstructure. Gas metal arc welding (GMAW) technique and V grove butt joint with four layers and five passes welded joint were performed. From this investigation, it is found that AA6061 with ER 4043 showed less distribution of porosity compared to AA6061 with ER 5356 welded joint confirmed by X-ray Ct-Scan. The decreasing of porosities and presence of very fine grains in weld region area with ER 5356 compared to ER 4043 will be discussed in term of microstructure analysis.

Abstract: The filler metal used during welding process is believed to play an important role on porosity formation in aluminium alloy welded. The present investigation is aimed to study the effect of different fillers ER4043 (Al-5%Si) and ER5356 (Al-5%Mg) on porosity formation of AA6061 alloy welded joints. Butt-joint welds were made on 6 mm thick plates using 21 – 22 V arc voltages by using Gas Metal Arc Welding process (GMAW). The hardness profile of each types of AA6061 welded joints for both fillers were characterized by the Vickers microhardness test. In order to study the formation and distribution of porosity, the images of analysis were obtained using the X- ray CT-Scan. It was observed that, more porosities were found in the alloy AA6061 using ER4043 compared to ER5356 filler metals with the percentage area value of porosity about 18.3 and 8.4%, respectively. The hardness profile of ER5356 and ER4043 welded materials exhibited the similar hardness pattern profile. It is proposed that Si and Mg contents in the filler metal could play significant role in the distribution of porosity. No significant effect was observed on the hardness profile for both filler metals of welded materials.

Abstract: Nowadays, die attach film (DAF) gaining popularity in microelectronic packaging as integral part in facilitating the growth of wafer level packaging and stacked die packaging. DAF applied to the backside of wafers prior to saw have many advantages, such as the elimination of the epoxy dispensed process step and the reduction of epoxy related failure mode. However, the dicing process for DAF wafer usually associated with sidewall chipping, DAF whiskering and crack that will affect reliability of Quad Flat Non-Leaded (QFN) stacked die. Blade properties and characteristics are the crucial factor in analyzing the DAF dicing results. In this paper, we evaluate the blade characteristics before and after DAF wafer dicing process for our stacked die packaging. The qualitative measure by means of the Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray (EDX) analysis were performed in order to understand the lamination and dulling effect on blade surface. The obtained results showed that sawing polymeric material such as wafer laminated with DAF induces lamination of polymeric material onto the blade surface and reduce blade cutting edge. As a result, reduce the quality of DAF dicing process.

Abstract: A tin-lead solder is generally used to mount an electronic package on to a printed circuit board (PCB) of an electronic devices. In this study, we investigated the microstructure of the solder joint from a four years old used mobile phone. Microstructure and morphology of the joint was obtained using optical and scanning electron microscopy (OM and SEM) respectively. Cracks and voids can clearly be seen in the solder area for the most of the sample observed. Crack up to 10 μm wide appeared to be propagating along the solder line between Cu lead and Cu substrate. Energy dispersive X-ray (EDX) analysis revealed that cracks occurred at the richer tin content. It was not clear the exact mechanism that leads to the existence of the crack. However we believe that thermomechanical cause such as thermal fatigue, void formation and the thicker layer of intermetallic compound contributed to the failure of the solder joint.