Maria Abu Bakar

Effect of gamma radiation on micromechanical hardness of lead-free solder joint

Lead-free solders are important material in nano and microelectronic surface mounting technology for various applications in bio medicine, environmental monitoring, spacecraft and satellite instrumentation. Nevertheless solder joint in radiation environment needs higher reliability and resistance to any damage caused by ionizing radiations. In this study a lead-free 99.0Sn0.3Ag0.7Cu wt.% (SAC) solder joint was developed and subjected to various doses of gamma radiation to investigate the effects of the ionizing radiation to micromechanical hardness of the solder. Averaged hardness of the SAC joint was obtained from nanoindentation test. The results show a relationship between hardness values of indentations and the increment of radiation dose. Highest mean hardness, 0.2290 ± 0.0270 GPa was calculated on solder joint which was exposed to 5 Gray dose of gamma radiation. This value indicates possible radiation hardening effect on irradiated solder. The hardness gradually decreased to 0.1933 ± 0.0210 GPa and 0.1631 ± 0.0173 GPa when exposed to doses 50 and 500 gray respectively. These values are also lower than the hardness of non irradiated sample which was calculated as 0.2084 ± 0.0.3633 GPa indicating possible radiation damage and needs further related atomic dislocation study.

Synthesis of Porous MgO into Sheet-Like Structure via Solution Routes

A simple solution route employing the reaction of magnesium acetate tetrahydrate ((CH3COO)2Mg.4H2O) and hexamethylenetetramine (C6H12N4) has been demonstrated to successfully grown MgO thin film on both Mg and MgO substrates at two different temperature i.e 90 °C and 150 °C for 4 h. Morphological observations revealed that the porous structure of MgO film was obtained on Mg substrate while sheet-like structure film was observed when using MgO substrate. EDX indicated only Mg and O were present in all films. The MgO bandgap obtained varies with type of substrate used and temperature. The MgO film growth on Mg substrate bandgap increased from 5.18 eV to 5.27 eV with temperature increased from 90 °C to 150 °C. Similar increased was also observed with MgO film growth on MgO substrate. However the results obtained are well below of MgO bulk energy bandgap. This was probably due to non-stoichiometry of deposited layers and crystallinity of the samples as shown by EDX and XRD results respectively.

Morphology and optical properties of nickel oxide nanostructure from aqueous solution

In this paper, porous flower-like nickel oxide (NiO) on glass substrates were prepared by an aqueous chemical growth based technique. The morphology and optical observed were found to be influence by the reaction time. Field Emission Scanning Electron Microscopy (FESEM) revealed a porous flower-like structure growth on the substrates investigated. The optical band gap for NiO thin film calculated from transmission spectra has increased from 3.72 eV to 3.91 eV with the increasing of reaction time. This result shows that the growth time have some influence on morphology and optical of NiO films.

Nanoindentation of Sn3.0Ag0.5Cu/ENIG Solder Joint after High Temperature Storage

This study used nanoindentation technique in order to examine the micromechanical properties of Sn3.0Ag0.5Cu (SAC305) on Electroless Nickel Immersion Gold (ENIG) surface finished Cu substrate subjected to high temperature storage. Lead free solder paste of SAC305 were soldered on ENIG substrate by reflow soldering at 215 °C for 8 second. The soldered samples were exposed to high temperature storage at 180 °C for 0, 200, 400, 600, 800 and 1000 hours. Micromechanical properties show that the solder hardness is decreasing with the HTS time from 239.13 MPa for 0 hour to 178.96 MPa for 1000 hours while the reduce modulus results has increased from 62. 16 x 103 MPa for 0 hour to 82.13 x 103 MPa for 1000 hours. The value of hardness and reduced modulus from nanoindentation approach indicate the occurrence of plastic and elastic deformation throughout the test.

Directional growth behaviour of intermetallic compound of Sn3.0Ag0.5Cu/ImSn subjected to thermal cycling

Directional growth behavior of intermetallic compound (IMC) layer of Sn3.0Ag0.5Cu (SAC305) on immersion tin (ImSn) surface finished Cu substrate was investigated. The samples of SAC305 on ImSn/Cu substrate were subjected to thermal cycling at temperatures between 0 °C and 100 °C for 0 cycle up to 500 cycles. The cross-sectioned microstructures of soldered samples, SAC305 on ImSn/Cu were observed using optical microscope. The shape and orientation of IMC growth on the SAC305 on ImSn/Cu indicates that the orientation of IMC growth were observed to be non-uniform and dispersed throughout the solder joint with longer thermal cycling test.

Bondability of Second Copper Wire Bonds on Silver and Nickel-Palladium–Gold-Silver Metallization

Several types of metallization have been used in order to enhance the bondability of wire bond. The introduction of copper (Cu) wire bond further increases the requirement of finding the suitable metallization. In this paper, two types of metallization, namely silver (Ag) and nickel-palladium-gold-silver (Ni/Pd/Au/Ag), deposited on Cu substrate were used as the bond pad for the second Cu wire bond. Wire pulling test was conducted on the Cu second bond by placing the hook near the second bond in order to obtain consistence stich of Cu wire bond. The characteristic remaining area of stich was obtained using the image processing software Image J. It was observed that the pull strength of the Cu second bond was higher for Ag metallization compared with that of Ni/Pd/Au/Ag metallization. It was also shown that the Cu second bond on the Ag metallization has higher contact diameter compared with that of Ni/Pd/Au/Ag metallization. The contact diameter of the Cu second bond on Ag metallization has higher value and it can be correlated with its higher value of pull strength. The characteristic area was found to be proportionally related with the pull strength of second bond.

Morphology and Optical Properties of Zinc Oxide Films Grown on Metal Coated Glass Substrates by Aqueous Chemical Growth

Zinc oxide films were deposited on three different metal coated substrates (gold, nickel and platinum) by aqueous chemical growth method. This paper discusses the effect of metal coated substrates on the morphology and optical properties of grown ZnO films. X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM) and UV-visible spectroscopy (UV-vis) were employed to characterize the samples. All the as-deposited ZnO films exhibit crystalline hexagonal wurzite structure. The crystallite size of the ZnO films were in the range of 29 to 32 nm. FESEM micrographs revealed hexagonal rod, oval-like and flower-like ZnO structures formed on all metal coated substrates. The Pt coated film contains higher density hexagonal rod as compared to others metal coated substrate. Most probably the Pt lattice parameter is the nearest to ZnO compared to nickel and gold. The optical band gap energy, Eg of ZnO films were estimated to be 3.30 eV which is near to bulk Eg, 3.37 eV. This indicates that the ZnO grown by aqueous chemical growth is able to produce similar quality properties to other conventional method either films or bulk size.

Transformation nanostructured nickel hydroxide to nickel oxide film by aqueous chemical growth

Nickel hydroxide, [Ni(OH)2] has been used extensively as the positive electrode material in rechargeable nickel-based batteries. Several approaches are known to be able for Ni(OH)2 growth including dc reactive magnetron sputtering, chemical spray pyrolysis, thermal evaporation, etc. This study discusses about nanostructured Ni(OH)2 film growth by aqueous chemical growth based technique. Ni(OH)2 film grown at 150 °C has a coral-like morphology whereas converted to NiO film by oxidation of Ni(OH)2 at 400 °C, confirmed by X-ray diffraction (XRD). Field Emission Scanning Electron Microscopy (FESEM) revealed a coral-like structure of Ni(OH)2 were grown on the glass substrates. Flake-like morphology was obtained for NiO film. The XRD pattern reveals that the intensity of observed peaks increased with the longer reaction time and film thickness which indicated an improvement in crystallinity. The optical band gap for Ni(OH)2 film calculated from transmission spectra increased from 3.72 eV to 3.91 eV with the inc...

The Effect of Substrate Position of Zinc Oxide Growth by Thermal Evaporation

Zinc oxide films were grown on silicon substrate by heating Zn pellet at 930° C under the flow of mixed argon and oxygen gas. X‐Ray Diffraction (XRD) spectra show well‐defined peaks which indicate crystalline sample that matched very well with those of standard zinc oxide. Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X‐rays (EDX) reveal needle like structure while EDX confirming that mainly Zn and O elements are present in the sample. The effect of substrate position on the morphology of thin film was investigated. It shows that the distribution of needle likes ZnO structure decrease with decreasing distance from its evaporation source.