Now showing 1 - 7 of 7
  • Publication
    Effect of Ni on the suppression of sn whisker formation in Sn-0.7Cu solder joint
    ( 2021) ; ;
    Andrei Victor Sandu
    ;
    ; ;
    Noor Zaimah Mohd Mokhtar
    ;
    Jitrin Chaiprapa
    The evolution of internal compressive stress from the intermetallic compound (IMC) Cu6Sn5 growth is commonly acknowledged as the key inducement initiating the nucleation and growth of tin (Sn) whisker. This study investigates the effect of Sn-0.7Cu-0.05Ni on the nucleation and growth of Sn whisker under continuous mechanical stress induced. The Sn-0.7Cu-0.05Ni solder joint has a noticeable effect of suppression by diminishing the susceptibility of nucleation and growth of Sn whisker. By using a synchrotron micro X-ray fluorescence (µ-XRF) spectroscopy, it was found that a small amount of Ni alters the microstructure of Cu6Sn5 to form a (Cu,Ni)6Sn5 intermetallic layer. The morphology structure of the (Cu,Ni)6Sn5 interfacial intermetallic layer and Sn whisker growth were investigated by scanning electron microscope (SEM) in secondary and backscattered electron imaging mode, which showed that there is a strong correlation between the formation of Sn whisker and the composition of solder alloy. The thickness of the (Cu,Ni)6Sn5 IMC interfacial layer was relatively thinner and more refined, with a continuous fine scallop-shaped IMC interfacial layer, and consequently enhanced a greater incubation period for the nucleation and growth of the Sn whisker. These verification outcomes proposes a scientifically foundation to mitigate Sn whisker growth in lead-free solder joint.
  • Publication
    Effect of isothermal annealing on Sn whisker growth behavior of Sn0.7Cu0.05Ni solder joint
    This paper presents an assessment of the effect of isothermal annealing of Sn whisker growth behavior on the surface of Sn0.7Cu0.05Ni solder joints using the hot-dip soldering technique. Sn0.7Cu and Sn0.7Cu0.05Ni solder joints with a similar solder coating thickness was aged up to 600 h in room temperature and annealed under 50 °C and 105 °C conditions. Through the observations, the significant outcome was the suppressing effect of Sn0.7Cu0.05Ni on Sn whisker growth in terms of density and length reduction. The fast atomic diffusion of isothermal annealing consequently reduced the stress gradient of Sn whisker growth on the Sn0.7Cu0.05Ni solder joint. It was also established that the smaller (Cu,Ni)6Sn5 grain size and stability characteristic of hexagonal η-Cu6Sn5 considerably contribute to the residual stress diminished in the (Cu,Ni)6Sn5 IMC interfacial layer and are able to suppress the growth of Sn whiskers on the Sn0.7Cu0.05Ni solder joint. The findings of this study provide environmental acceptance with the aim of suppressing Sn whisker growth and upsurging the reliability of the Sn0.7Cu0.05Ni solder joint at the electronic-device-operation temperature.
  • Publication
    Effect of Ni on the suppression of Sn whisker formation in Sn-0.7Cu solder joint
    ( 2021) ; ;
    Andrei Victor Sandu
    ;
    ; ;
    Noor Zaimah Mohd Mokhtar
    ;
    Jitrin Chaiprapa
    The evolution of internal compressive stress from the intermetallic compound (IMC) Cu6Sn5 growth is commonly acknowledged as the key inducement initiating the nucleation and growth of tin (Sn) whisker. This study investigates the effect of Sn-0.7Cu-0.05Ni on the nucleation and growth of Sn whisker under continuous mechanical stress induced. The Sn-0.7Cu-0.05Ni solder joint has a noticeable effect of suppression by diminishing the susceptibility of nucleation and growth of Sn whisker. By using a synchrotron micro X-ray fluorescence (µ-XRF) spectroscopy, it was found that a small amount of Ni alters the microstructure of Cu6Sn5 to form a (Cu,Ni)6Sn5 intermetallic layer. The morphology structure of the (Cu,Ni)6Sn5 interfacial intermetallic layer and Sn whisker growth were investigated by scanning electron microscope (SEM) in secondary and backscattered electron imaging mode, which showed that there is a strong correlation between the formation of Sn whisker and the composition of solder alloy. The thickness of the (Cu,Ni)6Sn5 IMC interfacial layer was relatively thinner and more refined, with a continuous fine scallop-shaped IMC interfacial layer, and consequently enhanced a greater incubation period for the nucleation and growth of the Sn whisker. These verification outcomes proposes a scientifically foundation to mitigate Sn whisker growth in lead-free solder joint.
  • Publication
    A 12 GHz LC-VCO Implemented with S’ shape Inductor using silicon-on sapphire substrate
    A voltage-controlled oscillator (VCO) is an electronic oscillator whose oscillation frequency is controlled by a voltage input. In a VCO, low-phase noise while consuming less power is preferred. The tuning gain and noise in the control signal produce phase noise; more noise or tuning gain implies more phase noise. Sources of flicker noise (1/f noise) in the circuit, the output power level, and the loaded Q factor of the resonator are all crucial factors that influence phase noise. As a result, creating a resonator with a high Q-factor is essential for improving VCO performance. As a result, this paper describes a 12 GHz LC Voltage- Controlled Oscillator (VCO) employed with a ‘S’ shape inductor to improve phase noise and power performance. The phase noise for the VCO was reduced using a noise filtering technique. To reduce substrate loss and improve the Q factor, the inductor was designed on a high-resistivity Silicon-on Sapphire (SOS) substrate. At 12 GHz, the optimised S’ shape inductor has the highest Q-factor of 50.217. At 10 MHz and 100 MHz, the phase noise of the 12 GHz LC-VCO was -131.33 dBc/Hz and -156.71 dBc/Hz, respectively. With a 3.3 V power supply, the VCO core consumes 26.96 mW of power. Based on the findings, it is concluded that using an ‘S’ shape inductor in the VCO circuit will enable the development of low-cost, high-performance, very low-power system-on-chip wireless transceivers with longer battery life.
  • Publication
    Effect of isothermal annealing on Sn whisker growth behavior of Sn0.7Cu0.05Ni solder joint
    This paper presents an assessment of the effect of isothermal annealing of Sn whisker growth behavior on the surface of Sn0.7Cu0.05Ni solder joints using the hot-dip soldering technique. Sn0.7Cu and Sn0.7Cu0.05Ni solder joints with a similar solder coating thickness was aged up to 600 h in room temperature and annealed under 50 °C and 105 °C conditions. Through the observations, the significant outcome was the suppressing effect of Sn0.7Cu0.05Ni on Sn whisker growth in terms of density and length reduction. The fast atomic diffusion of isothermal annealing consequently reduced the stress gradient of Sn whisker growth on the Sn0.7Cu0.05Ni solder joint. It was also established that the smaller (Cu,Ni)6Sn5 grain size and stability characteristic of hexagonal η-Cu6Sn5 considerably contribute to the residual stress diminished in the (Cu,Ni)6Sn5 IMC interfacial layer and are able to suppress the growth of Sn whiskers on the Sn0.7Cu0.05Ni solder joint. The findings of this study provide environmental acceptance with the aim of suppressing Sn whisker growth and upsurging the reliability of the Sn0.7Cu0.05Ni solder joint at the electronic-device-operation temperature.
  • Publication
    Analysis on square and circular inductor for a high Q-factor inductor
    This paper presents the high-quality (Q) factor inductors using Silicon-on-sapphire (SOS) for the 10GHz to 20GHz frequency band. Inductors are designed on SOS because of their advantages, including high resistivity and low parasitic capacitance. This paper compares square and circular inductor topologies for high-quality (Q) factor inductors using HFSS software for the high-frequency band. Both inductors have been designed with the same width and thickness to make them comparable with each other. The comparison shows that a circular inductor achieves the highest Q-factor. Furthermore, the circular and square inductor's Q-factor, inductance, and resistance are analyzed. As a result, the circular inductor has the maximum Q-factor of 89.34 at 10.6GHz for 0.29nH, while the square inductor has obtained a maximum Q-factor of 80.72 at 10GHz for 0.40nH inductance.
  • Publication
    A study on physical separation processes for recovery metals from waste printed circuit boards (PCBs)
    In view of increasing the waste PCBs, a physical separation process has been carried out to recover metals from waste PCBs. This research is aimed to implement an effective and environmental friendly recovery particularly cooper (Cu) of waste PCBs. The physical separation process begins with comminution to produce controlled particle size. Then, the separation process was divided into two parts according optimum efficiencies at specific size range. The size fraction -600+300µm and -1180+600µm were separated by gravity separation using Mozley laboratory separator. Afterwards, an enrichment step of concentrate fraction was done by magnetic separation using rare-earth roll magnetic separator. Meanwhile, the size fraction -150µm, -300+150µm, and -600+300µm were separated to froth flotation using Denver D-12 laboratory flotation cell. Characterisations of waste PCBs were performed by micrographic analysis and elemental analysis. A qualitative micrographic analysis was conducted using stereo- zoom microscope, optical microscope, and scanning electron microscopy. An elemental analysis was conducted using atomic absorption spectroscopy (AAS) analysis and energy dispersive spectrometer (EDS). Regarding on the particle size analysis, maximising recovery of physical separation is done by targeting recovery in a controlled four size range fraction; -150µm, -150+300µm, - 300+600µm and -600+1180µm. A qualitative liberation assessment of the waste PCBs particle was establish unliberated particles still remain in the waste PCBs fines (-75µm). As the highest metal element in waste PCBs, copper (Cu) recovery (R) and enrichment ratio (ER) was discussed with more emphasis in this project. By Mozley laboratory separator, Cu recovery increase from 80.85% (ER 2.07) at -600+300µm size fraction to 89.65% (1.93) at -1180+600µm size. Thus, the efficiency of gravity separation increases with increasing particle size. A significant of the low recovery at finer size fraction implies valuable metal loss at this size range, thereby be evidence that it is not very effective for finer particles (- 300µm) was recovered by Mozley laboratory separator. For enrichment step using Rareearth roll magnetic separator showed the enrichment ratio (ER) was highly improved. At - 600+300µm non-magnetic fraction, Cu enrichment ratio is 2.51 and 2.15 at -1180+600µm size fraction. Through the reverse froth flotation, higher Cu recovery (R) and lower Cu enrichment ratio (ER) are noticeably with increasing particle size fraction for both flotation conditions (with and without frother). Thus, the efficiency of froth flotation is higher at finer size fraction. At -75µm size fraction, Cu recovery is 84.66% (ER 3.03) under natural hydrophobic responds (without frother). Meanwhile with frother addition, Cu recovery is 82.16% (ER 3.37). In view of frother addition, there is improved in enrichment ratio but poor recovery percentage. Overall, the approach physical separation has high efficiency, easy to run and at same could recover metals and non-metals. It is expected that physical separation process will be developed for the upgrading of metals recovery in waste PCBs.