• Journal of the Korean Society for Precision Engineering
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• v.21 no.7
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• pp.171-178
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• 2004

Techniques and procedures are presented for measuring mechanical properties on thin-film Polysilicon. Narrow platinum lines are deposited 250 ${\mu}{\textrm}{m}$ apart on tensile specimens that are 3.5 ${\mu}{\textrm}{m}$ thick and 600 ${\mu}{\textrm}{m}$ wide. Load is applied by a piezo-actuator and by hanging weights. Strain is measured by an ISDC at temperatures up to 500 $^{\circ}C$. Measurements of the elastic modulus with jig modifications, loading speed and temperature change are presented first. And then, the preliminary data for the coefficient of thermal expansion and creep behavior are presented as a reference.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.4
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• pp.83-87
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• 2022

Recently, as the thickness of the semiconductor package becomes thinner, warpage has become a major issue. Since the warpage is caused by differences in material properties between package components, it is essential to precisely evaluate the material properties of the EMC(Epoxy molding compound), one of the main components, to predict the warpage accurately. Especially, the cure shrinkage of the EMC is generated during the curing process, and among them, the effective cure shrinkage that occurs after the gelation point is a key factor in warpage. In this study, the gelation point of the EMC was defined from the dissipation factor measured using the dielectric sensor during the curing process similar with actual semiconductor package. In addition, DSC (Differential scanning calorimetry) test and rheometer test were conducted to analyze the dielectrometry measurement. As a result, the dielectrometry was verified to be an effective method for monitoring the curing status of the EMC. Simultaneously, the strain transition of the EMC during the curing process was measured using the FBG (Fiber Bragg grating) sensor. From these results, the effective cure shrinkage of the EMC during the curing process was measured.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.6
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• pp.15-20
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• 2017

In this study, the fracture energy and displacement fields characteristics of particulate reinforced composite is evaluated. Wedge splitting test was performed at various temperatures. Fracture energy of material is calculated at room temperature, $-40^{\circ}C$ and $-60^{\circ}C$. Displacement and strain fields of specimen surface were visualized by using digital image correlation. The surface displacement fields of the specimens were analyzed by mark tracking method using digital image correlation. The results showed that, the fracture energy was decreased as temperature decreased. The surface displacement fields at room temperature were similar to there at $-40^{\circ}C$. The surface displacement fields at $-60^{\circ}C$ was significantly reduced because of the brittle behavior. The strain fields of the specimen surface decreased as temperature decreased form room temperature to $-60^{\circ}C$.

• Journal of the Korean Society for Nondestructive Testing
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• v.16 no.4
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• pp.225-233
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• 1997

This study is performed to establish a non-destructive evaluation method for metal matrix composite using ultrasonic technique. The specimen is made of SiC/AC8A metal matrix composite by squeeze-casting method. Three kinds or reinforced particles are prepared as 4.86, 8.09 and $11.44{\mu}m$ to investigate the effect of size on the mechanical and ultrasonic properties of metal matrix composite. In addition, four different volume fractions (14, 22.5, 27.5, 35%) of reinforced particles are prepared per each size to examine the effect of volume fraction on the ultrasonic properties. From this specimen, the availability and precision of measurement of Young's modulus are examined and the evaluation method for microstructure of metar matrix composite using the speed of sound and attenuation factor is also reviewed. The results show that the Young's modulus measured by ultrasonic method is as effective as that measured by mechanical method. It is also known that the size and volume fraction of reinforced fiber are precisely evaluated using the speed of sound and attenuation factor.

• Journal of Korean Society of Steel Construction
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• v.17 no.6 s.79
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• pp.681-688
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• 2005

This study investigates an existing steel plate girder railroad bridge after superstructure rehabilitation to monitor static and dynamic responses using Fiber Bragg Grating (FBG) sensors. This paper also presents an experimental technique to estimate the vertical deflection of the bridge using FBG sensors. Seven FBG sensors are multiplexed in a single optical fiber and installed in parallel pairs along the length of the bridge, with one set at the top flange and the other at the bottom flange. In addition to FBG sensors, a conventional electric strain gauge and anLVDT are installed at the mid-span of the bridge for comparison. A test train consisting of one locomotive is placed at the center of the bridge to produce the maximum static effect. The train is also made to pass over the bridge at different speeds ranging from 10 km/h to 90 km/h to monitor the dynamic response of the bridge. This study demonstrates that the measured strains using the FBG sensor compared well with the readings from the electric strain gauge. The results show that the proposed instrumentation technique is capable of estimating the vertical deflection of the bridge for various loading conditions, which is crucial in structural health monitoring. Several dynamic characteristics of the bridge were also identified.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.2
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• pp.46-51
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• 2002

Cold expansion of fastener holes is a mechanical process widely used in the aerospace industry. This treatment leads to an improvement of fatigue behavior due to the developed compressive residual stresses on the hole surface. The residual stress profile depends on the parameters of cold expansion, which are expanding rate, inserting direction of mandrel, material properties dtc. Despite its importance to aerospace industiries, little attention has been devoted to the accurate modeling of the process. In this paper, three-dimensional finite element simulations have been conducted for the cold expansion in an aluminium plate in order to predict the magnitude and distribution of the residual stress. To prove the results of FE analysis, the residual strain was measured by strain gage in cold expansion test. Maximum compressive residual stress could be increase about 7 percentage using the 2-step cold expansion method.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.5
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• pp.484-493
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• 2012

Since the 1980s, there have been many research activities devoted to quantitatively characterizing and imaging human tissues based on sound speed, attenuation coefficient, density, nonlinear B/A parameter, etc., but those efforts have not yet reached the stage of commercialization. However, a new imaging technology termed elastography, which was proposed in the early 1980s, has recently been implemented in commercial clinical ultrasound scanners, and is now being used to diagnose prostates, breasts, thyroids, livers, blood vessels, etc., more quantitatively as a complementary adjunct modality to the conventional B-mode imaging. The purpose of this article is to introduce and review various elastographic algorithms for use in quasistatic or static compression type elasticity imaging modes. Most of the algorithms are based on the crosscorrelation or autocorrelation function methods, and the fundamental difference is that the time shift is estimated by changing the lag variable in the former, while it is directly obtained from the phase shift at a fixed lag in the latter.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.3
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• pp.89-93
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• 2020

Complex warpage behavior of the electronic packages causes internal stress so many kinds of mechanical failure occur such as delamination or crack. Efforts to predict the warpage behavior accurately in order to prevent the decrease in yield have been approached from various aspects. For warpage prediction, silicon is generally treated as a homogeneous material, therefore it is described as showing no warpage behavior due to thermal loading. However, it was reported that warpage is actually caused by residual stress accumulated during grinding and polishing in order to make silicon wafer thinner, which make silicon wafer inhomogeneous through thickness direction. In this paper, warpage behavior of the single-side polished wafer at solder reflow temperature, the highest temperature in packaging processes, was measured using 3D digital image correlation (DIC) method. Mechanism was verified by measuring coefficient of thermal expansion (CTE) of both mirror-polished surface and rough surface.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.5
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• pp.90-97
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• 2001

An electronic speckle pattern interferometry (ESPI) system for measuring tensile properties under micro-tensile testing has been developed. The system consists of an optical system and an image processing system. In the optical system, optical components for measurement of in-plane deformation are arranged on the path of He-Ne laser. In the image processing system, the window-based program for acquiring speckle pattern interferometric image was developed and deformation in a small specimen is continuously evaluated during the test. Using this system, tensile strain of copper foil was measured during tensile testing. Tensile specimen had the thickness and width of 22 and 500 ${\mu}{\textrm}{m}$, respectively. Tensile properties, including the elastic modulus, yielding strength and tensile strength, of the copper were evaluated and also plastic exponent and coefficient in the Ramberg-Osgood relationship were evaluated from the stress-strain curve.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.5
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• pp.498-504
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• 2014

Displacements and strains are very important for material evaluation as critical factors to a machine's life cycle and safety. Typically, the strain gauge has been employed to measure displacement and strain. However, this contact-type measurement method has disadvantages that are not quantified under the test conditions of a specific object shape, surface roughness, and temperature. In this paper, the measurement of deflection and flexural strain due to the three-point bending test is presented, employing Digital Image Correlation (DIC) methods. In order to ensure measurement reliability, DIC and universal test machine methods were compared by measuring the deflections and flexural strains developed by such bending tests.