Phase Stability, Phase Transformations, and Reactive Phase Formation in Electronic Materials XVI: Poster Session
Sponsored by: TMS Functional Materials Division, TMS: Alloy Phases Committee
Program Organizers: Shih-kang Lin, National Cheng Kung University; Chao-hong Wang, National Chung Cheng University; Jae-Ho Lee, Hongik University; Ikuo Ohnuma, National Institute for Materials Science (NIMS); Chih-Ming Chen, National Chung Hsing University; Thomas Reichmann, Karlsruhe Institute of Technology; Yu Zhong, Florida International University; Shijo Nagao, Osaka University; Shien Ping Tony Feng, The University of Hong Kong; Yee-wen Yen, National Taiwan Univ of Science & Tech

Tuesday 6:00 PM
February 28, 2017
Room: Hall B1
Location: San Diego Convention Ctr

Session Chair: Shih-kang Lin, National Cheng Kung University

L-174: Investigation on Interfacial Reactions between the Multi-walled Carbon Nanotubes Reinforced Sn-Ag-Cu Composite Solders with Cu: Gita Hermana1; Shu Fu1; Yee Yen1; 1National Taiwan University of Science and Technology
    The 0-0.07 wt.% multi-walled carbon nanotubes (MWCNTs) added into the Sn-3.0Ag-0.5Cu (SAC) solder to react with Cu substrate aged at 100-200C for 5-30 h has been studied. The scalloped Cu6Sn5 and layered Cu3Sn phases were observed at the interface. When the reaction temperature was greater than 150C, the scalloped Cu6Sn5 phase was transferred to the layered structure. Adding MWCNTs into the SAC solder inhibited the formation of the Cu6Sn5 and Cu3Sn phases. Thus, when the more MWCNTs were added into the SAC solders, the lower growth rate and higher action energy in the SAC-MWCNTs/Cu system were found. According to the wetting test results, the 0.05 wt% MWCNTs added into the Sn-3.0Ag-0.5Cu solder has the lowest contact angle and the best wettability with the Cu substrate.

L-175: Application of Computational Thermodynamics in SOFCs: Shadi Darvish1; Yu Zhong1; 1Florida International University
     From the application point of view, selection of a perovskite oxide, as solid oxide fuel cell (SOFC) cathode, requires to meet specific criteria, such as the phase stability, high electrical conductivity and thermo-mechanical properties. Various perovskite oxides were experimentally investigated by the trial and error approach. However, due to the complex of the problem and also the wide composition range of perovskites, it is still a challenge to find the optimal candidates. In order to suppress these limitations, thermodynamic database development followed by the quantitative calculations, utilized by the CALculation of PHAse Diagram (CALPHAD) approach, is represented as an outstanding method to predict the phase stability, electrical conductivity and thermo-mechanical properties in the wide range of temperature, atmosphere and composition for the doped lanthanum perovskite oxides.

L-177: Calorimetric Investigation of the Liquid Sn-3.8Ag-0.7Cu Alloy with Minor Additions of Mn and Ni: Andriy Yakymovych1; Hans Flandorfer1; Herbert Ipser1; 1University of Vienna
    To date, additions of pure metals, such as Co, Mn or Ni, in bulk and nanosized forms is one of the most widespread procedures to reinforce the microstructure and improve the mechanical properties of Sn-based Sn-Ag-Cu solder alloys. However, the scientific activity related to the development of novel lead-free solders should not be limited to studies of mechanical properties only. For instance, solidification behavior, interfacial diffusion and reaction as well as microstructure of multi-component alloy systems can be estimated from a proper thermodynamic and kinetic data base. This research deals with the heat effects observed on mixing of Mn and Ni with liquid Sn-3.8Ag-0.7Cu alloy using drop calorimetry. From this the integral and partial enthalpies of mixing for the quaternary (Sn-3.8Ag-0.7Cu)-Mn and (Sn-3.8Ag-0.7Cu)-Ni alloys are estimated. The microstructure and phase composition of furnace cooled samples after calorimetric runs were examined using SEM and X-ray diffraction.

L-178: Degradation Mechanism of Piezoelectric Materials: Hooman Sabarou1; Yu Zhong1; 1Florida International University
    The disappearance of polarization hysteresis characteristics occurs for piezoelectric (PZT) materials so that the performance of the materials is being degraded. To avoid this problem, finding the origin of this issue is necessary. This research approaches to the problem from a new aspect for the first time and mainly focuses on perovskite structure of PZT materials. The several tests have been designed to scrutinize the structural evolution of perovskite under various oxygen partial pressures and temperatures and to simulate working conditions of PZT materials. PZT pellets have been annealed under different temperatures and oxygen partial pressures. The evolution of crystal structure has been studied via XRD. Thermal analysis tests also exhibit changes in perovskite structure and truly justify the degradation in polarization characteristics of PZT materials. The mechanism of the structural evolution is discussed and promoted to real PZT applications.

L-179: Effect of Silver Precursor Addition on Shear Strength of Cu-Cu Joints with Silver Nanoparticle Paste: Hung-Tao Chen1; 1National Cheng Kung University
    Silver nanoparticle paste has become a promising candidate for three-dimensional integrated circuit (3D-IC) bonding because of its low process temperature, low contact resistance, and lack of Pb. In addition, interconnects joined by Ag nanoparticles have high heat resistance, high thermal conductivity, and high fatigue resistance. In this study, to enhance mechanical strength, silver nanoparticle-based paste was synthesized from a mixture of a silver precursor and silver nanoparticles. Shear tests followed by a thermo-compression process (250oC, 10MPa, 30min) were carried out to investigate the effects of the addition of the silver precursor on the shear strength, microstructure, and fracture mechanism. After the addition of the precursor, the shear strength increased from 14.0 to 31.2 MPa, microstructure became denser and interlocking joints were observed at the copper-silver interface. Adding a silver precursor thus improves sintering among silver nanoparticles, leading to the formation of interlocking joints at the interface, which increase shear strength.

L-180: Investigating Mixed Crystal Solid Solution of High Performance Scintillators KBa2I5:Eu & KSr2I5:Eu: Jesse Johnson1; Luis Stand1; Mariya Zhuravleva1; Merry Koschan1; Chuck Melcher1; 1University of Tennessee-Knoxville
    Previously we have demonstrated crystals of compositions KBa2I5:Eu and KSr2I5:Eu have light yields of ~90,000 ph/MeV and energy resolution of 2.4% for ~ 0.01 cm3 crystals, comparable to the highest performing scintillators. The higher density and Zeff of KBa2I5:Eu is desired for radiation detection, however it is difficult to grow while KSr2I5:Eu is easy. Both KSr2I5:Eu and KBa2I5:Eu have monoclinic crystal structures, space group (P21/c), therefore a mixed crystal solid solution strategy was viable for improving scintillation properties. A nominal composition of KSrBaI5:Eu was grown which separated into multiple phases, one of which produced an energy resolution of 2.20% from a ~0.2 cm3 crystal. It was determined this composition was KSr1.3Ba0.7I5 by applying Vegard’s Law to characteristic peaks from X-ray powder diffraction patterns. A single crystal of KSr1.3Ba0.7I5:Eu was successfully grown via Bridgman method displaying an energy resolution of 2.4% from a ~0.63 cm3 crystal extracted from the boule.

L-182: Stretchability Characteristics of Thin Metal Films on Polydimethylsiloxane Substrates with the Parylene Adhesion Layer for Stretchable Electronic Packaging: Donghyeon Park1; Soo Jin Shin1; Jae-Ho Lee1; Tae-Sung Oh1; 1Hongik University
     Electronic packaging technologies with strtechabilty and flexibility have been investigated for advanced wearable devices. For various methods proposed to form stretchable circuitry with thin films, Cr has been used to promote adhesion of metal films to elastomeric polydimethylsiloxane (PDMS) substrates. However, strong adhesion between a metal film and an elastomeric substrate would not always be the most splendid method to enhance the stretchability of a thin film. In this study, we used the parylene instead of Cr as an adhesion layer between a metal film and PDMS. We sputtered Au, Pt, and Cu films on PDMS with parylene or Cr as an adhesion layer, and characterized their resistance-change behaviors on the PDMS/parylene and PDMS/Cr substrates with stretching up to 30% elongation. Acknowledgement: This work was supported by the ICT R&D programs of MSIP/KEIT of Korea (Project No. B0101-16-0420, Development of Transformational and Slap-on Wearable Device and UI/UX).