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Assaneesarntiwong Roongroj, Hideo Koguchi
Article type: Article
Session ID: 3242
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Dissimilar materials are frequently used in industrial products, such as electronic devices, welded joints and composite materials. The characteristics of the stress fields around a vertex in three-dimensional joints are investigated using a boundary element method. It is shown that the order of stress singularity between two sides of free surface in three-dimensional joints increases when the vertex angle decreases. The position of maximum stress intensity factor also depends on the slant angle of side surface.
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Tadao KAGIWADA, Hiroyuki HARADA, Akihiko YOSHIDA
Article type: Article
Session ID: 3243
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Loosening of the wheel nuts may be the cause of accidents where the wheel falls off while the automobile is running. When the transverse force of wheel bolts exceeds a certain proportion of the bolt shaft force, the wheel nut begins to loosen. The results of 3-dimensional numerical analysis established that the transverse force was influenced by the bolt shaft force caused by the bolt fastening. When the transverse force of wheel bolt exists, disproportional force acts the nut seat and it appears as pressure distribution in the contact surface of nut seat. In this study, the pressure distribution in the nut seat is measured using the pressure measuring film to obtain the transverse force of wheel bolt. It is clear that the results, the pressure in the contact area of nut seat when whole 8 wheel nuts are tightened is far larger than that when only one wheel nut is tightened although the bolt shaft force are identical with each other, and the fact indicates that the transverse force of wheel bolt caused by the bolt shaft force exists.
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Yoji KITAMURA, Masaru ISHIZUKA, Shinji NAKAGAWA, Katsuhiro KOIZUMI
Article type: Article
Session ID: 4319
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In this paper are presented the results of a numerical study on the chimney in a natural air-cooled electronic equipment casing. In order to promote the natural convective air-cooling capability, we have focused on about chimney effect by casing inclining. Moreover, we came up with assembling the chimneys on an inclined casing. For evaluating thermal behavior of inclination and chimney, experiments and numerical simulations have been carried out using a different material chimneys and a thin electronic equipment casing that has inlet and outlet in front-top side. As a result, we obtained the numerical simulation results for the thermal behavior inside the thin electronic casing, and it was in good agreement with experimental ones.
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Toshio TOMIMURA, Seiji NOMURA, Masaaki OKUYAMA
Article type: Article
Session ID: 4320
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In the electronic equipment like personal computers with high heat fluxes for instance, an interstitial material is often introduced between the heat sink and the heat source to reduce the thermal contact resistance (TCR). In the present study, the effect of silicone grease layer with the thermal conductivity 1.1W/(m-K) on TCR between flat rough surfaces has been investigated under relatively low mean nominal contact pressure p_m from about 0.01 to 0.07MPa. As a result, a fairly good reduction effect of TCR has been obtained for about p_m>0.04MPa.
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Katsuhiro KOIZUMI, Masaru ISHIZUKA
Article type: Article
Session ID: 4321
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This paper describes the effect of shape parameters on the flow resistance of perforated plates used in electronic equipment. In order to demonstrate the influence of hole shape on the flow resistance of perforated plates, measurement of 16 perforated plates and analysis of the results were conducted using the Design of Experiments (DoE) method. In the range of levels of DoE analysis assumed for electronic equipment, it was found that hole shape has little effect on flow resistance.
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Masaru ISHIZUKA, Shinji NAKAGAWA, Yoji KITAMURA, Katsuhiro KOIZUMI
Article type: Article
Session ID: 4322
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This paper describes experimental results on thermal behavior in sealed natural air-cooled electronic equipment casing. One of the authors has already proposed a simple practical equation for thermal design of a sealed natural convection air-cooled electronic equipment casing. However in that study the casing was made of plastic and had a cube shape of side length of 0.4m. Therefore, in the present work, an aluminium casing having length, width and height of 0.1m, 0.4m, and 0.3m, respectively, was used. The temperature of casing surfaces and air inside the casing were measured with various inclinations and for three different ways of casing setting on the floor. Results indicated only a small change in value of the coefficients used in the equation developed by one of the author.
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Hiroyuki Tsuritani, Toshihiko Sayama, Takeshi Takayanagi, Yoshiyuki Ok ...
Article type: Article
Session ID: 4323
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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An X-ray micro-tomography system developed in SPring-8 was applied to the evaluation of microstructural evolution ; that is phase growth, appearing as thermal fatigue damage in solder micro-bumps of flip chip interconnects. The obtained CT (Computed Tomography) images show that components of the flip chip such as interconnecting patterns, pads, or bumps are identified with high spatial resolution of about 1μm. Especially, in the the solder bumps, characteristic microstructure is clearly observed, while such information has not been obtained at all by industrially used X-ray CT systems. Remarkable phase growth is also observed clearly as thermal cycle proceeds. This result shows the possibility that nondestructive testing by micro CT system is useful for the evaluation of the thermal fatigue damage in micro-joints.
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Takao MORI, Hiroshi MINAMI, Toshihiko SAYAMA, Takeshi TAKAYANAGI
Article type: Article
Session ID: 4324
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This paper describes phase growth of Sn-3.0Ag-0.5Cu solder joints by mechanical cyclic loading. Lap joint type shear specimens were used to evaluate the influence of temperature and strain on the phase growth process of solder joints. The mechanical cyclic loading was carried out under constant temperature condition. The phase growth processes of β-Sn phase in the solder joint were observed by the scanning electron microscope (SEM). Consequently, various phase growth processes were observed under different strain rate conditions.
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Masafumi AKAKAMTSU, Kazuhiko NAKANE, Nobutada OHNO
Article type: Article
Session ID: 4325
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In this study, a linearization approach is used to develop an implicit integration scheme for the high-temperature inelastic constitutive models based on non-linear kinematic hardening. A non-unified model is considered in which inelastic strain rate is divided into the transient and steady parts driven, respectively, by effective stress and applied stress. By discretizing the constitutive relations using the backward Euler method, and by linearizing the resulting discretized relations, a tensor equation is derived to iteratively achieve the implicit integration of constitutive variables. The integration scheme is then programmed as a subroutine in a finite element code and applied to a lead-free solder joint analysis. It is thus demonstrated that the integration scheme affords the quadratic convergence of iteration even for considerably large increments.
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Kisho ASHIDA, Kenya KAWANO, Naotaka TANAKA, Hiroyuki NAKAMURA
Article type: Article
Session ID: 4326
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Strength evaluation of Ag paste for die bonding during reflow soldering is an important issue, because fracturing of Ag paste is one of the main causes of plastic package failure. First, we estimated that the cause of fracturing was vapor pressure at the interface between resin and Cu frame and thermal stress caused by the thermal mismatch between Si chip and Cu frame. Next, we obtained the fracture strength by three-points bending test of a bonded specimen with Ag paste. Finally, by calculating the stress of Ag paste during moisture absorption and reflow soldering, and comparing it to the fracture strength, we estimated the probability of Ag paste fracturing.
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Nobuki Ueta, Hideo Miura
Article type: Article
Session ID: 4327
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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We performed a finite element analysis in order to make clear the residual stress distribution in stacked chips mounted by flip chip technology using area array metallic bumps. The maximum value of the normal stress changes about 200MPa by changing the assembly structure from a wire bonding structure to a flip chip structure. The amplitude of the local stress of about 90MPa also appears between two bumps. The residual stress in the stacked two chips varies depending on the distance from a bending neutral axis of the stacked structure. In addition, the local stress distribution between two bumps was confirmed by using a stress sensor chip that includes about 160 strain gauges with 10-μm length.
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Kenya KAWANO, Yasuo OSONE, Yuji SHIRAI
Article type: Article
Session ID: 4328
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The structural reliability for Cu-bump joint was studied analytically by using a design of experiments. Moreover, the influence of mechanical property of underfill resin on the fatigue life of Cu-bump interconnect under the thermal cycle test was also studied. In conclusion, it was found that the thermal stress at the interface between the Cu-bump and the UBM increases as the increase in thickness and length of Cu-bump. The interface stress especially depends on the length of Cu-bump. The length of Cu-bump was thus important design factor to be compatible both the joint reliability and the highly heat dissipation. It was also found that the existing mechanical property of underfill resin for solder-bump joint was appropriate for Cu-bump joint connected to the substrate using solder.
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Yuki Sato, Hideo Miura
Article type: Article
Session ID: 4329
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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We have proposed a new nondestructive evaluation method for detecting the delamination between a Si chip and metallic bumps by applying a measurement of local surface deformation of the Si chip. Since the local deformation decreased when an underfill material is filled in the delaminated space, it is important to measure the surface deformation of a Si chip before and after filling the underfill. To confirm the local deformation at a Si chip surface, we made test flip chip structures. The predicted local displacement at the samples surface was detected by a white light interferometer.
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Masaaki KOGANEMARU, Toru IKEDA, Noriyuki MIYAZAKI, Hajime TOMOKAGE
Article type: Article
Session ID: 4330
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Stress-induced electronic characteristic shifts in resin-molded electronic packages (QFP) were evaluated experimentally. The drain current shifts and transconductance shifts of nMOSFETs were measured. We also investigated the device shape dependence and molding resin dependence of the characteristics shifts. The experimental results were evaluated reasonably using the results of residual stress evaluation in QFP and results of stress sensitivity evaluation of nMOSFETs.
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Nobuyiki SHISHIDO, Toru IKEDA, Noriyuki MIYAZAKI
Article type: Article
Session ID: 4331
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In this study, a system for measuring thermal strain in micro region of electronic packages using the digital image correlation was developed, and applied for measuring the distribution of strain in a cross-section of a print circuit board (PCB) during thermal cycle test. The warpage of the PCB expected from the measured strain accurately corresponded with the macroscopic warpage measured using a laser displacement meter. The accuracy of measured displacements was affected by image distortion caused by an optical system. An error correction method using a piezo stage was proposed to improve the accuracy of the system.
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Nagatoshi Okabe, Xia Zhu, Keiji Ogi, Nobuhoru Settsu
Article type: Article
Session ID: 4332
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In this research, we did thermal cycle test, four point bend test, and the simulation analysis by finite element method (FEM) to DBC and AMC semiconductor substrate. We examined influence of thermal-residual stress on the life reliability of the substrates, and did the basic research for establishing a profitable strength evaluation method through the comparison with the two kinds of joint methods. It is clarified that the AMC substrate is more excellent than the DBC substrate from the viewpoint of strength and the longevity reliability of the semiconductor substrate.
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Hideo KOGUCHI, Atsushi UENO
Article type: Article
Session ID: 4333
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Recently, an advanced chip size packaging technology is important for developing portable electronic devices. Chip size package (CSP) is composed of metal, IC, and the polymeric material. Thermal fatigue occurs often due to the difference of thermal properties between a substrate and a chip. Thermal and mechanical loads cause the warpage of CSP. In this study, a simple theory on the bases of a multi-layer plate theory considering a viscoelastic property in substrate and resin sheet is presented. The thermo-viscoelastic analysis for the deflection of CSP is performed. The amount of warpage is predicted when temperature cooled down from 453K of the bonding temperature to 298K in the room temperature. Finally, the results of this study are compared with experimental results.
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Norihiro WATANABE, Atsushi MICHIMORI, Takashi KOJIMA, Yoshio KONO, Hir ...
Article type: Article
Session ID: 4334
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In recent years, home use televisions become thinner, lighter and more inexpensive, and therefore the demand for home use television's replacement has been increasing. And because they can be hung from the ceilings or on the wall, we can set them for fitting with our lifestyle. On the other hand, because many and various people use televisions in the home, they must be designed with the safety for users. Even if they are damaged by accident, the users must not suffer any harm. Furthermore, the realization of a lower cost thin television is necessary, and some new problems have been obvious. In this report, we introduce our new technology which solves the problems in making the thin, light and safety television sets in low cost. And we show some results of simulations and experiments.
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Article type: Appendix
Pages
App4-
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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