T Ikeda

Kyushu University, Fukuoka-shi, Fukuoka-ken, Japan

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Publications (112)212.33 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Numerical methods such as the finite element method (FEM) have been used to evaluate the reliability of electronic packages. However, it is difficult to assure the accuracy of numerical analyses of electronic packages, which require nonlinear analyses. In this study, we evaluated the thermal strain of a test chip for three-dimensional stacked integrated circuits (3D SIC) with both measurement and analyses. First, the distribution of thermal strain on the cross-section of the test chip was measured using the digital image correlation method (DICM). Then, the distribution of strain on the surface of a cut test chip was also analyzed by the FEM while considering the viscoelasticity of underfill (UF) resin measured with the stress relaxation test and the elastic-plasticity of components measured with nanoindentation testing. Based on the comparison between the DIC measurements and the FEM analyses, we improved the accuracy of the nonlinear finite element analyses.
    3D Systems Integration Conference (3DIC), 2011 IEEE International; 01/2012
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    ABSTRACT: This paper presents a practical method of drift-diffusion device simulation for evaluating the effects of mechanical stress on n-type silicon semiconductor devices. The device simulation incorporates an electron mobility model for considering the effects of stress. In this paper, we focus on stress effects that are induced by applying inplane biaxial stress to the devices. Therefore, two physical phenomena that are attributed to mechanical stress are modeled in the electron mobility model, i.e., the changes in relative population and the momentum relaxation time (intervalley scattering) of electrons in conduction-band valleys. Stress-induced variations of direct-current characteristics on n-type metal-oxide-semiconductor (MOS) field-effect transistors are evaluated using a device simulation including the proposed electron mobility model. Then, the electron mobility model and the simulation method are verified by comparing with experimental results. It is demonstrated that experimental results can be reasonably estimated using this device simulation method. From discussions regarding the electron mobility model, it is suggested that the comprehensive stress sensitivity of MOS devices is larger than that of lightly doped silicon.
    IEEE Transactions on Electron Devices 09/2011; · 2.36 Impact Factor
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    ABSTRACT: The effects of uniaxial mechanical stress on the radio frequency (RF) performance of n- and p-metal-oxide-semiconductor field effect transistors (MOSFETs) fabricated on (100) Si wafer are investigated up to 10 GHz. Uniaxial mechanical stress is applied to the MOSFETs parallel to the direction of drain current flow using a four-point bending fixture. Under tensile stress, the gate transconductance (gm) increases in the n-MOSFETs while it decreases in the p-MOSFETs, whereas the results were vice versa for compressive stress. These tendencies are same to the effects of uniaxial mechanical stress on direct current (DC) transconductance of the MOSFETs, therefore, it is considered that the gm with RF is dependent on stress-induced sub-band splitting of Si. The total gate capacitance (CG) extracted from scattering parameters increases (decreases) under tensile (compressive) stress for both n- and p-MOSFETs, which is explained by the variation of the effective mass perpendicular to the Si/SiO2 interface. The cut-off frequencies (fT) estimated from the gm and the CG varies in inverse proportion to the gate capacitance variation.
    Electronic System-Integration Technology Conference (ESTC), 2010 3rd; 01/2010
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    ABSTRACT: We evaluated the stress-induced effect on electronic characteristics of nMOSFETs using mechanical stress simulation and drift-diffusion device simulation. The simulation model includes the electron mobility model that takes the stress effects into consideration. We evaluated the variation in the electronic characteristics of nMOSFET during the actual resin-molding packaging process (QFP process). The stress distribution in the nMOSFET was considered in the device simulation. As a result, the experimental results were evaluated reasonably using the proposed simulation method. It is demonstrated that the device simulation is useful and versatile for evaluating the stress-induced effect on electronic characteristics of a semiconductor device.
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    ABSTRACT: A polarizing plate, which is an important part of a liquid crystal display panel (LCD), is made by sandwiching an organic polarizer between protecting films. An organic polarizer is both a hygroscopic and orthotropic material. The hygroscopic swelling and drying shrinkage of the organic polarizer can cause the polarizing plate to crack and the liquid crystal display panel to warp. The diffusion coefficient and Henry's law coefficient were measured using a thermo-gravimetric analyzer (TGA) under controlled humidity, while the coefficient of moisture expansion (CME) was measured using a thermo-mechanical analyzer (TMA), also under controlled humidity. The thermo-mechanical and hygro-mechanical deformation of a polarizing plate was analyzed using the finite element method (FEM). This analysis was performed as follows. The distribution of the moisture concentration was analyzed according to Fick's law. The equation of Fick's law is similar to that of the transient heat conduction, and the FEM for the transient heat conduction was utilized for the transient diffusion analysis. The hygro-mechanical analysis was then carried out in a way similar to the thermal stress analysis. Thermal stress was analyzed separately using the FEM. Finally, the obtained hygro-mechanical strain and stress were added to the thermal strain and stress, respectively. The analyzed displacement of a polarizing plate using the CMEs of a polarizer and protecting films corresponds to the measured displacement. The warpage of a liquid crystal display panel sometimes causes light leakage along the frame of the display panel due to contact of the display panel with the bezel of the frame. The warpage was analyzed according to the thermo-mechanical strain and the hygro- mechanical strain.
    Electronic Materials and Packaging, 2007. EMAP 2007. International Conference on; 12/2007
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    ABSTRACT: A method for image correction is proposed for digital image correlation in conjunction with a laser scanning confocal microscope (LSCM). The scan lines of an LSCM have sub-pixel error in their position in the scanning direction (drift distortion). Drift distortion decreases the accuracy of the displacement measured using the DIC method. The correction method proposed here removes both drift distortion and spatial distortion. Drift distortion is removed using a pair of images, each of which has a different scanning direction. Spatial distortion removal is performed using a methodology that employs a series of in-plane rigid body motions and a generated distortion map. Numerical simulations demonstrated that these correction procedures can successfully detect drift distortion. The standard deviation (SD) of the obtained detection error for artificial noise with sub-pixel line-shift was 0.004 pixels. Experimental results involving rigid body motion indicate that, after the correction of drift and spatial distortions, (i) the standard deviation of the measured displacements was 0.03 pixels, and (ii) the measured displacement fields are unbiased and agree closely with those obtained using an optical microscope. The proposed correction method effectively removes the distortions of obtained images and improves the accuracy of the digital image correlation method using an LSCM.
    Electronic Materials and Packaging, 2007. EMAP 2007. International Conference on; 12/2007
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    ABSTRACT: The reliability of a stacked ball grid array (stacked BGA) package during the solder reflow process was examined using the finite element method (FEM). The stress intensity factors (SIFs) at an interfacial crack tip in the stacked BGA package were analyzed. Vapor pressure on the surfaces of an initial crack and thermal stress were considered. The vapor pressure during the solder reflow was estimated by moisture diffusion analysis. Initial cracks were assumed along interfaces between the die-attach paste/film and a solder resist (SR) layer, the epoxy molding encapsulant (EME) and a SR layer, and a cupper layer and a SR layer. The SIFs of these interfacial cracks were compared with the fracture toughnesses of respective interfaces. The effect of the sizes of the initial cracks on the SIFs was investigated. To measure the fracture toughnesses of the respective interfaces, we performed delamination tests. Finally, the crack extension was estimated by comparing the SIFs of each interfacial crack to its fracture toughness. In this study, we clarified that cracks tend to extend on the interface between the EME and a SR layer, and that vapor pressure during the solder reflow process significantly influences the crack propagation.
    Electronic Materials and Packaging, 2006. EMAP 2006. International Conference on; 01/2007
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    ABSTRACT: The element-free Galerkin (EFG) method is applied to the calculation of elastic-plastic fracture mechanics parameters such as the J-integral and T * -integral. The fields of displacement, strain and stress for a crack problem are obtained using the elastic-plastic EFG method. Then the elastic-plastic fracture mechanics parameters J-integral and T * -integral are calculated from path and domain integrals. In the finite element analysis, paths for the path integral and domains for the domain integral are selected depending on finite element mesh division. On the other hand, they can be arbitrarily selected in the EFG method, and we can use a simple integral path and domain such as a circular shape surrounding a crack tip, which can provide efficient numerical integral formulae for the path and domain integrals. In a crack growth problem, the simple integral path and domain can easily move together with the crack tip, as the crack tip advances. This paper presents a method for calculating the J-integral and T * -integral in a framework of the EFG method. The proposed method is applied to both a stationary crack problem and a stable crack growth problem. The results obtained from the EFG method are compared with those of the finite element method and experiments to show the effectiveness of the EFG method to the elastic-plastic fracture mechanics parameter analysis.
    Computer Modeling in Engineering and Sciences 01/2007; 17(2). · 1.18 Impact Factor
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    ABSTRACT: Computational mechanics approaches, especially computational fracture mechanics, have been utilized as a powerful tool for reliability studies of large-sized structures such as air crafts, pressure vessels, piping and so on. Electronic packages are considered as small-sized structures to protect electrical integrity of electronic devices. So the computational mechanics can be successfully applied to the reliability studies of electronic packaging. In the electronic packages, there exist a lot of interfaces between different materials, so that the interface fracture mechanics is very useful for such studies. In the first part of the present paper, we summarize the interface fracture mechanics, and then we provide two examples of the application of computational mechanics to the reliability studies of electronic packaging. One example is the strength evaluation of a plastic package during solder reflow process, and another is the delamination evaluation of anisotropic conductive adhesive films under moisture/reflow sensitivity tests. Key wordsinterface fracture mechanics–stress intensity factors–electronic package–plastic package–anisotropic conductive films–moisture absorption
    12/2006: pages 88-100;
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    ABSTRACT: Stress-induced shifts in the DC characteristics of nMOSFETs were investigated experimentally by the 4-point bending method. We measured the device shape dependence and load direction dependence of the DC characteristic shifts. We also carried out drift-diffusion device simulation in order to evaluate the experimental results. The simulation model includes the electron mobility model that takes the stress effects into consideration. The conduction band energy change induced by the shear deformation of silicon is considered in the mobility model. The experimental results were evaluated reasonably using the proposed mobility model
    Electronics Systemintegration Technology Conference, 2006. 1st; 10/2006
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    ABSTRACT: Recently, the sizes of electronic products have been decreasing rapidly, with many electronic devices embedded in print circuit boards (PCBs), a phenomenon known as system in package (SiP). In the near future, not only passive devices but also active devices are embedded in the PCBs. It is thought that stress and strain around embedded devices affects the functions of embedded devices. A measurement system of stress and strain in the microstructures of PCBs is needed. In this study, a system for measuring thermal strain in the micro region of PCBs using the digital image correlation method (DICM) in conjunction with an optical microscope was developed. The accuracy of the measurement of thermal strain was verified by measuring the distribution of strain on the surface of a homogeneous aluminum alloy that is heated uniformly. Then, the strain distribution in a PCB was measured using the developed system. Although the measured distribution of strain in the PCB using the DICM was very complicated, the warpage of the PCB calculated from the measured strain accurately corresponded with the macroscopic warpage measured using a laser displacement meter. The accuracy of measurement was affected by the image distortion caused by the optical system and by the nonlinearity of the image sensor of the complementary metal-oxide semiconductor (CMOS) camera. An error correction method was introduced into the present measurement system to increase the system's accuracy.
    Electronics Materials and Packaging, 2005. EMAP 2005. International Symposium on; 01/2006
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    ABSTRACT: The element-free Galerkin method (EFGM) is one of the meshless methods proposed by Belytschko et al. Since node-element connectivities used in the finite element method (FEM) are not needed in the EFGM, the EFGM is expected to be applied to many problems of the continuum mechanics and to be utilized for a tool in a CAE system instead of the FEM. However the EFGM requires more CPU time to search nodes of the MLSM than the FEM. In this paper, the method of the directed graph and the Delaunay triangulation are respectively used for searching nodes and the division of the integral domain respectively. These techniques are useful for saving the CPU time and the simplification of the analysis for the EFGM. Furthermore, the EFGM has not been applied to nonlinear problems such as creep problems under elevated temperature. In this paper, the EFGM using the method of the directed graph and the Delaunay triangulation is applied to several creep problems. The CPU times for the analyses are reduced by the proposed EFGM. The results obtained from the EFGM analyses agree well with those of the FEM.
    Computational Mechanics 07/2003; 31(6):489-495. · 2.04 Impact Factor
  • Journal of Materials Science Letters 01/2003; 22(3):229-233.
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    ABSTRACT: We performed a cross-sectional investigation on the impact of obesity on clinical manifestations in patients with obstructive sleep apnea/hypopnea syndrome (SAHS). The subjects were 87 patients who underwent overnight polysomnography with an apnea/hypopnea index (AHI) of 15/h or more. We divided these patients into non-obese (N) and obese (O) groups based on the median value of the body mass index (BMI), 27 kg/m2. Subjective symptoms, sleep quality and AHI were similar in both groups, but every parameter related to oxygen desaturation was worse in group O than in group N. There was no difference in the mean duration of apnea events between the two groups. The rate of fall in oxygen saturation during apnea events was highly correlated to the BMI (r = 0.72; p < 0.00001). Accordingly, we concluded that profound desaturation in group O is due to a rapid fall in oxygen saturation during apnea events compared with group N. Anthropometric measurements revealed that the rate of fall in oxygen saturation was more related to abdominal circumference (AC) than the neck circumference (NC), which is contrasted with the finding that AHI was more related to NC than AC. This fact suggests that abdominal obesity may deteriorate oxygenation during apnea events and may therefore aggravate the risk of cardiovascular disease in patients with SAHS.
    Nihon Kokyūki Gakkai zasshi = the journal of the Japanese Respiratory Society. 09/2001; 39(9):650-5.
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    ABSTRACT: The receptor activator of nuclear factor-kappaB ligand (RANKL; also known as tumor necrosis factor-related activation-induced cytokine [TRANCE], osteoprotegerin ligand [OPGL], and osteoclast differentiation factor [ODF]) is a transmembrane ligand expressed in osteoblasts and bone marrow stromal cells. It binds to RANK, which is expressed in osteoclast progenitor cells, and induces osteoclastogenesis. OPG, a decoy receptor for RANKL, also binds to RANKL, and competitive binding of RANKL with RANK or OPG is thought to regulate bone metabolism. To investigate roles of the RANKL/RANK/OPG system in pathophysiological conditions, the expression of RANKL, RANK, and OPG messenger RNA (mRNA) was analyzed in bones of aged and ovariectomized rats by means of in situ hybridization. In the control 8-week-old male and sham-operated female rat bones, the expression of RANKL mRNA was detected in hypertrophic chondrocytes of the growth plate and some periosteal and endosteal mesenchymal cells. The expression of RANK mRNA was detected in osteoclast-like cells and mononuclear cells in contact with the cortical and trabecular bones. The expression of OPG mRNA was detected in proliferating chondrocytes and osteocytes. In the 2.5-year-old rat bones, the expression of RANKL, RANK, and OPG mRNA tended to decrease except for the endosteal region. In the ovariectomized rat bones, the expression of RANKL, RANK, and OPG mRNA increased, and high expression of OPG mRNA was induced in resting chondrocytes and osteocytes. These results suggest that estrogen deficiency stimulates the RANKL/RANK/OPG system and induces OPG in cells that have been thought to be less important for bone metabolism.
    Journal of Bone and Mineral Research 09/2001; 16(8):1416-25. · 6.59 Impact Factor
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    ABSTRACT: The receptor activator of nuclear factor (NF)-kappaB ligand [RANKL; also known as tumor necrosis factor-related activation-induced cytokine, osteoprotegerin ligand, and osteoclast differentiation factor] is known to bind with the receptor activator of NF-kappaB (RANK) and act not only as a key factor for osteoclastogenesis but also as a regulator of lymphocyte development. In this study, we found two additional isoforms of RANKL. RANKL 2 has a shorter intracellular domain than the original RANKL (RANKL 1), and RANKL 3 lacks a transmembrane domain and was thought to act as a soluble form. In the bone marrow stromal cell line ST2 and preosteoblastic cell line MC3T3-E1, all three RANKL isoforms were detected, but the expression of RANKL 2 was preferentially suppressed by treatment with 1alpha,25-dihydroxyvitamin D(3) and dexamethasone. In young adult thymus, CD4(-)CD8(-) double-negative cells were positive for all three isoforms, CD4(+)CD8(+) double-positive cells were positive for RANKL 1 and RANKL 3 but negative for RANKL 2, and CD4(+)CD8(-) and CD4(-)CD8(+) single-positive cells were positive for all three isoforms. Immunofluorescence analyses of NIH3T3 cells transfected with each RANKL isoform indicated that the three RANKL isoforms were translated, and RANKL 2 protein predominantly stayed in the endoplasmic reticulum and Golgi networks. These results indicate that there are three kinds of RANKL-RANK pathways. The presence of multiple RANKL-RANK pathways suggests a more complicated RANKL-RANK system for osteoclastogenesis or T cell differentiation than previously thought.
    Endocrinology 05/2001; 142(4):1419-26. · 4.64 Impact Factor
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    ABSTRACT: A 65-year-old man was referred to our hospital due to abnormal chest roentgenograms showing bilateral hilar enlargement with diffuse micronodular opacities. He presented with uveitis and elevated serum ACE and tested negative for tuberculin response. Transbronchial lung biopsies as well as bronchoalveolar lavage were performed and yielded a diagnosis of sarcoidosis. Several months later, the patient showed multiple subcutaneous nodules around the knee joints and elbow joints with exacerbation of intrapulmonary lesions. A skin biopsy revealed multiple foci of typical non-caseating epithelioid cell granulomata. These pulmonary and subcutaneous lesions rapidly resolved in response to the systemic administration of corticosteroids. Subcutaneous sarcoidosis may be a subacute variant of sarcoidosis associated with systemic involvement.
    Nihon Kokyūki Gakkai zasshi = the journal of the Japanese Respiratory Society. 05/2000; 38(4):317-20.
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    ABSTRACT: Changes in bone modeling and remodeling in the tibia of growing rats within 30 days of ovariectomy (ovx) were evaluated by histomorphometric, mechanical; and biochemical means. Three days after ovx, suppressed bone formation was seen. This was shown by reduced osteoid volume, osteoblast surface, and bone formation rate in the secondary spongiosa, and a reduced longitudinal growth rate in the growth plate. In addition, the alkaline phosphatase and tartrate-resistant acid phosphatase activity in bone marrow supernatants was suppressed in conjunction with elevated serum sialic acid levels, indicating inflammation. Although estrogen deprivation itself may provoke the inflammatory process, the serum sialic acid level in the ovx group returned to the baseline level within 5 days after surgery, while that of estradiol in the ovx group remained consistently lower. This suggests that surgical stress, not estrogen deprivation, is the primary cause of the inflammatory response shortly after ovx. A significant difference (p < 0.01) between the ovx and sham rats was seen in the osteoclast surface, which peaked on day 7 in the ovx rats. On day 14 postovariectomy, the bone formation rate peaked and remained constant until day 30. In the ovx rats, there was a sustained reduction in the serum albumin level until day 30. Estrogen deprivation may be the primary cause of these changes, because both surgical ovx and medical oophorectomy with gonadotropin-releasing hormone agonist (G(nRHa) reduce the serum albumin level. In numerous studies dealing with changes after ovx in rats, we have observed: 1) a transient reduction in bone formation in relation to inflammatory changes evoked by ovx surgery, and 2) a sustained reduction in the serum albumin level for at least 30 days after ovx that is possibly due to estrogen deprivation.
    Bone 01/2000; 26(1):43-53. · 4.46 Impact Factor
  • Key Engineering Materials 01/2000; 183-187:73-78.
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    ABSTRACT: Osteopontin (OPN) is an Arg-Gly-Asp-containing phosphoprotein that is secreted by activated T cells. The concentration of serum OPN protein is elevated in autoimmune-prone MRL-lpr mice as well as in patients with systemic lupus erythematosus. Previously, it was shown that OPN induces the polyclonal activation of B cells, resulting in the augmented production of immunoglobulin, indicating that OPN plays some role in the development of autoimmune disease. However, the link between OPN and development of autoimmune disease remains unclear. To analyze the role of OPN in immune system and autoimmune diseases, we have generated two kinds of transgenic mice: one carries the immunoglobulin (Ig) enhancer/SV40 promoter and the other carries the cytomegalovirus enhancer/chicken beta-actin (CAG) promoter. In both groups of transgenic mice, the B1 cell population in peritoneal cavity was markedly increased and titer of IgM and IgG3 antibodies in the serum was considerably higher than that in wild-type mice. Most important, the titer of the IgM class of anti-double-stranded DNA antibody was significantly elevated in transgenic mice. These results strongly suggest that OPN may have an important role in the propagation and differentiation of B1 cells and production of autoantibodies.
    Laboratory Investigation 01/1999; 78(12):1523-33. · 3.83 Impact Factor

Publication Stats

2k Citations
212.33 Total Impact Points


  • 1991–2003
    • Kyushu University
      • • Department of Chemical Engineering
      • • Faculty of Medical Sciences
      Fukuoka-shi, Fukuoka-ken, Japan
  • 2000–2001
    • Tokyo Medical and Dental University
      • Department of Medicine
      Edo, Tōkyō, Japan
  • 1999
    • Fukuoka National Hospital
      Hukuoka, Fukuoka, Japan
  • 1991–1995
    • Showa University
      • • Department of Biochemistry
      • • School of Dentistry
      Shinagawa-ku, Japan
  • 1994
    • Tokyo Metropolitan Institute of Gerontology
      Edo, Tōkyō, Japan
  • 1988–1991
    • Kanazawa University
      • Department of Internal Medicine
      Kanazawa, Ishikawa, Japan