Updated on 2022/01/24


Faculty of Science and Engineering, Information, Production, and Systems Center
Job title
Research Associate

Research Interests

  • 金属ナノ粒子接合

  • メッキ接合


  • An Embedded SiC Module with Using NMPB Interconnection for Chevron Shaped Cu Lead and Electrodes

    Naoki Fukui, Keiko Koshiba, Itaru Miyazaki, Isamu Morisako, Tomonori Iizuka, Tomoya Itose, Masayuki Hikita, Rikiya Kamimura, Kohei Tatsumi

    Proceedings - Electronic Components and Technology Conference   2020-June   2226 - 2229  2020.06

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    © 2020 IEEE. As for the IGBT power device based on Si used for the vehicle, the performance limit of the Si semiconductor has been pointed out, and the SiC semiconductor has been attracting attention as a next-generation semiconductor. The SiC semiconductor has advantages such as a wider band gap, a larger breakdown electric field, and high temperature operation (about 300 ° C.). If these features can be maximized, a SiC power semiconductor module that can be significantly improved in efficiency, downsized, and operable in a high-temperature environment as compared with a Si semiconductor can be more widely implemented.In this study, two sets of SiC-MOS and SiC-SBD devices are embedded in a ceramic substrate, and their electrodes and the copper electrodes of the substrate are interconnected by NMPB (Nickel Micro-plating Bonding) method, so that one-leg prototype inverter modules of a highly heat-resistant and ultra-small size (47x30x1.3mm) could be manufactured. The NMPB method is a technology that we have originally developed to connect a chip electrode and a lead formed in a chevron shape by Ni plating. High-temperature operation and excellent switching characteristics of the SiC power module were demonstrated.


  • High temperature resistant packaging technology for SiC power module by using Ni micro-plating bonding

    Kohei Tatsumi, Isamu Morisako, Keiko Wada, Minoru Fukuomori, Tomonori Iizuka, Nobuaki Sato, Koji Shimizu, Kazutoshi Ueda, Masayuki Hikita, Rikiya Kamimura, Naoki Kawanabe, Kazuhiko Sugiura, Kazuhiro Tsuruta, Keiji Toda


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    There is an increasing expectation to incorporate silicon carbide (SiC) as inverter power modules for hybrid electric vehicles (HEVs) and electric vehicles (EVs). In order to maximize the performance of SiC devices, new packaging technologies that can realize high-temperature heat resistance by replacing solder joint or Al wire bonding, have been strongly demanded. In order to meet these demands, we have developed a new interconnection technology named Nickel micro-plating bonding (NMPB), that enables the interconnection in a narrow gap between electrodes of SiC devices and substrates via our newly designed lead frame, whose lead surface is formed into chevron shape. The plating bath for NMPB is a sulfamic acid bath consisting of nickel sulfamate and several additives, and was specifically prepared to plate narrow areas at the bonding interface without plating defects. It was found that when columnar crystal grains grow from both facing electrode surfaces, a strong bond without defects such as micro-voids at the interface is obtained. The bonding strength of NMPB was confirmed by shear test to be higher than that of Pb free solder joints and not to deteriorate even after high temperature storage (HTS) tests at 250 degrees C for 1000hrs and after 1000cycle thermal cycle tests (TCTs, 250 degrees C/-45 degrees C). The NMPB was applied to the manufacture of one leg SiC inverter power module using two pairs of SiC MOS-FETs and SBDs, which were interconnected with a newly designed lead frame for double sided cooling structure. After molding resin copper heat spreaders were formed on the outer surfaces of both sides of the NMPB leads by additive method. Our newly developed SiC power module showed stable I-V characteristics over 250 degrees C and lower switching loss. The reliability of the modules was confirmed by TCTs and power cycle tests.


  • High temperature resistant interconnection for SiC power devices using Ni micro-electroplating and Ni nano particles

    Kohei Tatsumi, Yasunori Tanaka, Tomonori Iizuka, Keiko Wada, Minoru Fukumori, Isamu Morisako, Yoon Jeongbin, Norihiro Murakawa


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    Recently there are high expectations for incorporating silicon carbide (SiC) devices as power modules in hybrid electric vehicles (HEV) and electric vehicles (EV). The need fir new bonding technologies, which can deliver high-temperature thermal resistance that replaces solder bonding or Al wire bonding, has been strongly expected in order to maximize the performance of SiC power device. We developed a new micro plating interconnection technology named Nickel Micro Plating Bonding (NMPB) which enables the interconnection in a narrow space between electrodes and SiC devices via our new lead frame formed in chevron shape. As for the bonding strength of NMPB, sufficient joint strength value is confirmed by shear test. We also newly proposed low-temperature nickel nanoparticle sintering to form die bonding connections. We have confirmed that bonding at a bonding temperature of 400 degrees C or lower is possible, and that it is a bonding having long-term high heat resistance. We implemented heat resistant mounting of SiC schottky barrier diode (Slip) on the TO247 type package and confirmed the I-V characteristics even after the high temperature storage at 300 degrees C without any significant degradation. We clarified that these methods had adequate potential as an advanced heat resistant package in comparison with conventional interconnections.

  • Phase Field Simulation Analysis of Nitrogen Absorption-Phase Transformation Behavior in the High Temperature Stable Ferritic Stainless Steel

    Mitsui Hajime, Koshiba Keiko, Ohnuma Takashi

    Tetsu-to-Hagane   101 ( 6 ) 336 - 342  2015

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    The behavior of diffusion and phase transformation in a high temperature stable ferritic stainless steel (SUS444) nitrogen-absorbed at 1450 K for 4 hr under 0.4 MPa N2 gas was investigated with EPMA mapping. While Cr content in the nitrogen absorption layer (NA layer: γ phase) increased, Mo discharged from NA layer was enriched in the grain boundary of α/γ. Using a 1D-phase field simulation (PFS), the phenomenon during the NA treatment in the Fe-19Cr-2Mo-0.5Mn-N alloy was discussed. In the case of PFS with impurity diffusion (lattice diffusion) coefficients in Fe, since the diffusion velocity in γ phase was smaller than that of α phase, concentration distribution between NA layer and matrix α phase is caused by local phase equilibrium in depending on the composition of NA layer. Additionally, diffusion of substitutional atoms is slower than the growing velocity of NA layer that is depended on nitrogen diffusivity. This is the reason why Cr content in the NA layer fluctuates and why the average compositions in α phase and NA layer has the opposite trend with thermodynamic calculated and experimental results. On the other hand, in the case of the simulation under Dγ > Dα in consideration of the grain boundary diffusion of substitutional elements, the segregation behavior of solute elements was in good agreement with the results of EPMA mapping. Thus, it was confirmed that not only the diffusion of N atoms but also the grain boundary diffusion contributes greatly to the growing phenomenon of NA layer in a high stable ferritic stainless steel.

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  • Preferential growth orientation of laser-patterned LiNbO<inf>3</inf> crystals in lithium niobium silicate glass

    T. Komatsu, K. Koshiba, T. Honma

    Journal of Solid State Chemistry   184 ( 2 ) 411 - 418  2011.02

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    Dots and lines consisting of LiNbO3 crystals are patterned on the surface of 1CuO40Li2O32Nb2O528SiO 2 (mole ratio) glass by irradiations of continuous-wave Nd:YAG laser (wavelength: λ=1064 nm), diode laser (λ=795 nm), and Yb:YVO 4 fiber laser (λ=1080 nm), and the feature of laser-patterned LiNbO3 crystal growth is examined from linearly polarized micro-Raman scattering spectrum measurements. LiNbO3 crystals with the c-axis orientation are formed at the edge parts of the surface and cross-section of dots. The growth direction of an LiNbO3 along the laser scanning direction is the c-axis. It is proposed that the profile of the temperature distribution in the laser-irradiated region and its change along laser scanning would be one of the most important conditions for the patterning of crystals with a preferential growth orientation. Laser irradiation giving a narrow width is also proposed to be one of the important factors for the patterning of LiNbO3 crystal lines with homogeneous surface morphologies. © 2010 Elsevier Inc. All rights reserved.


  • Writing of crystal lines and its optical properties of rare-earth ion (Er3+ and Sm3+) doped lithium niobate crystal on glass surface formed by laser irradiation

    Tsuyoshi Honma, Keiko Koshiba, Yasuhiko Benino, Takayuki Komatsu

    Optical Materials   31 ( 2 ) 315 - 319  2008

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    A glass of Li2O-Nb2O5-SiO2-B2O3 with an addition of CuO or Sm2O3 crystallizing in nonlinear optical lithium niobate LiNbO3 is developed. Crystalline lines of Lithium Niobate have been fabricated by continuous wave laser irradiation of the glass surface. The crystalline laser written lines have been found, by means of micro-Raman and Second Harmonic experiments, to be well oriented with its c-axis pointing along the laser scanning direction. The analysis of the confocal micro luminescence spectra obtained at the crystalline line have confirmed the incorporation of rare-earth ions in the crystalline network. © 2008 Elsevier B.V. All rights reserved.


  • Patterning and morphology of nonlinear optical Gd<inf>x</inf>Bi <inf>1-x</inf>BO<inf>3</inf> crystals in CuO-doped glass by YAG laser irradiation

    K. Koshiba, T. Honma, Y. Benino, T. Komatsu

    Applied Physics A: Materials Science and Processing   89 ( 4 ) 981 - 986  2007.12

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    Dots and lines consisting of nonlinear optical GdxBi 1-xBO3 crystals were patterned on the surface of CuO-doped Gd2O3-Bi2O3-B2O 3 glass by heat-assisted (200 °C) Nd:YAG laser irradiations with a wavelength of λ=1064 nm, where the laser energy absorbed by Cu 2+ is converted to the local heating of the surrounding Cu 2+. The surface morphology and orientation of crystals in the patterned lines were clarified from confocal scanning laser microscope observations and polarized micro-Raman scattering spectra. Crystal lines with periodic bumps (i.e., ladder-shape like lines) were patterned by laser irradiations with a power of 0.79 W and a scanning speed of 60 μm/s, and the orientation of GdxBi1-xBO3 crystals in the lines was proposed. The present study demonstrates that the combination of Cu2+ and continuous wave Nd:YAG laser with λ=1064 nm is effective in inducting crystallization of oxide glasses. The mechanism of laser-induced crystallization in glass has also been discussed. © 2007 Springer-Verlag.


  • Patterning and characterization of ferroelectric crystal lines at the glass surface by laser-induced crystallization

    T. Komatsu, M. Sato, R. Nakajima, H. Sugita, K. Koshiba, T. Honma, Y. Benino

    IEEE International Symposium on Applications of Ferroelectrics     293 - 294  2007

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    A technique for the patterning of ferroelectric crystal lines such as Sr0.5Ba0.5Nb2O6, LiNbO3, β'-Gd2(MoO4)3 at the glass surface has been developed, i.e., transition metal atom heat processing, in which continuous wave lasers such as Nd:YAG (wavelength: λ=1064 nm) are irradiated to the glasses containing transition metal (TM: Cu2+, Ni2+) ions. The absorbed laser results in local heating of glass, consequently inducting crystallization. By scanning laser (power: < 1W) at constant speeds such as 10 μm/s, ferroelectric crystal lines are written successfully at the glass surface. The surface morphology and orientation of crystals in the lines are clarified from confocal laser microscope observations and polarized micro-Raman scattering spectra measurements. In some glasses, the patterning of crystal lines consisting of oriented ferroelectrics is possible.


  • Synthesis of novel photosensitive polymers from aromatic polyamides conaining hydroxyl group

    Kazuto Inoue, Keiko Koshiba, Yuhsuke Yoshida, Akihito Magara, Yoshiaki Itoh

    Polymer Preprints, Japan   54 ( 2 ) 4021  2005

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    Aromatic polyamides containing cinnamoyloxy group were prepared from the corresponding aramids having hydroxyl group and cinnamoyl chloride in pyridine. The polyamide obtained gave a negative-tone behavior by UV irradiation of 254 and 366 nm without a photosensitizer. Developing time was only 10 sec. in DMAc.

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  • LiNbO3 crystal patterning in Li2O-Nb2O5-SiO2 glass by transition metal atom heat processing

    Koshiba Keiko, Honma Tsuyoshi, Komatsu Takayuki

    Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan   2007 ( 0 ) 536 - 536  2007

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Specific Research

  • ニッケルメッキを用いた新規高耐熱実装技術の開発


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