• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1617-1620
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• 2007

This paper presents a magnetostrictive transpositioner and its fabrication process. To get a transposition movement without shifting or twisting, it is designed as an array type. To fabricate the suggested design, micromachining and selective DC magnetron sputtering processes are combined. TbDyFe film is sputter-deposited on the back side of the bulk micromachined transpositioner, with the condition as: Ar gas pressure below $1.2{\times}10^{-9}$ torr, DC input power of 180W and heating temperature of up to $250^{\circ}C$ for the wireless control of each array component. After the sputter process, magnetization and magnetostriction of each sample are measured. X-ray diffraction studies are also carried out to determine the film structure and thickness of the sputtered film. For the operation, each component of the actuator has same length and out-of-plane motion. Each component is actuated by externally applied magnetic fields up to 0.5T and motion of the device made upward movement. As a result, deflections of the device due to the movement for the external magnetic fields are observed.

• Journal of Sensor Science and Technology
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• v.14 no.6
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• pp.374-380
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• 2005

Vibration sensors have a wide scope of applications in the field of monitoring systems that needs to perceive an undesirable physical vibration before a critical failure occurs in a system, and then costly unplanned repairs can be avoided. The conventional vibration sensors developed so far have many disadvantages, such as complex manufacturing process, bulkiness, high cost, less reliability and so on. This paper reports a simple-structured vibration sensor, which has been developed using a commercialized conductive ball and silicon bulk-micromachining technology. The sensor consists of a conductive ball placed in $600{\mu}m$-deep micromachined silicon groove, in which Au thin film has been patterned using a shadow mask technique. Prior to the formation of the Au thin film, the sharp convex corner was rounded for smooth meatl deposition on the non-planar surface at the edge of the groove. The measurement results of the fabricated vibration sensor demonstrate a stable response characteristic to low-frequency vibration range ($1{\sim}30{\;}Hz$).

• Journal of the Korean Society for Precision Engineering
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• v.26 no.6
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• pp.50-58
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• 2009

Micro laser fabrication techniques can potentially be used for the manufacture of microstructures on the thin flat surfaces with large diameter that are frequently used in semiconductor industries. However, the large size of wafers can cause the degraded machining accuracy of the surface because it can be tilted or distorted by geometric errors of machines or the holding fixtures, etc. To overcome these errors the off-line focusing error compensation method is proposed. By using confocal autofocus system, the focusing error profile of machined surface is measured along the pre-determined path and can be compensated at the next machining process by making the corrected motion trajectories. The experimental results for silicon wafers and invar flat surfaces show that the proposed method can compensate the focusing error within the level of below $6.9{\mu}m$ that is the depth of focus required for the laser micromachining process.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.9 s.186
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• pp.164-173
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• 2006

The cooling capacity of a micro-heat pipe is mainly governed by the magnitude of capillary pressure induced in the wick structure. For microchannel wicks, a higher capillary pressure is achievable for narrower and deeper channels. In this study, a metallic micro-heat pipe adopting high-aspect-ratio microchannel wicks is fabricated. Micromachining of high-aspect-ratio microchannels is done using the laser-induced wet etching technique in which a focused laser beam irradiates the workpiece placed in a liquid etchant along a desired channel pattern. Because of the direct writing characteristic of the laser-induced wet etching method, no mask is necessary and the fabrication procedure is relatively simple. Deep microchannels of an aspect ratio close to 10 can be readily fabricated with little heat damage of the workpiece. The laser-induced wet etching process for the fabrication of high-aspect-ratio microchannels in 0.5mm thick stainless steel foil is presented in detail. The shape and size variations of microchannels with respect to the process variables, such as laser power, scanning speed, number of scans, and etchant concentration are closely examined. Also, the fabrication of a flat micro-heat pipe based on the high-aspect-ratio microchannels is demonstrated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.3
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• pp.222-229
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• 2009

A noble infrared sensor was studied for passenger conditional detection in vehicle, This research relates to uncooled infrared sensors for detecting the presence, type and temperature of occupants in vehicle. It sense that the occupants purpose to control the smart airbag for safety in the case of adult or child and to control the automatic air conditioning for convenience. This paper described the design and the fabrication of microbolometers which were composed of 2 by 8 elements using the surface micromachining technology. The characteristics of the array were investigated in the spectral region of $8{\sim}12{\mu}m$. The fabricated detectors exhibited the thermal mass of $7.05{\times}10^{-9}\;J/K$, the thermal conductance of $1.03{\times}10^{-6}\;W/K$, the thermal time constant of 6.8 ms, the responsivity of $2.96{\times}10^4\;V/W$ and the detectivity of $1.01{\times}10^9\;cmHz^{1/2}/W$, at the chopper frequency of 10 Hz and the bias current of $4.4{\mu}A$. We could successfully detect the human body condition in the divided zone. As a results, we concluded that microbolometer optimized in this research could be useful for the application of passenger conditional detection in vehicle.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.7
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• pp.991-996
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• 2002

This paper presents the fabrication method of a micro-riblet film (MRF) using MEMS technology and the experimental results of the drag reduction of an airfoil with MRFs. Riblets having grooved surface in the streamwise direction has been proven as an effective passive control technique of the drag reduction. A V-grooved pattern on (100) silicon wafer is etched with anisotropic bulk micromachining. The MRF is completed by replicating the V-grooved pattern with polydimethylsiloxane (PDMS). Experiments were performed by measuring a velocity field behind the trailing edge of a NACA 0012 airfoil with and without MRFs in a closed-type subsonic wind tunnel using particle image velocimetry (PlV) technique. The MRF provides about 3.8 % drag reduction compared to the drag on a smooth airfoil when the freestream velocity of wind tunnel is 3.3 m/s.

• Laser Solutions
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• v.12 no.1
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• pp.7-13
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• 2009

Engineering ceramics as sapphire are widely used in industry owing to their superior mechanical and corrosion properties. However, micromachining of sapphire is a considerable challenge due to its transparency. Recently, direct ablation of sapphire has been demonstrated with a visible laser pulse at sufficiently high laser intensity. In this work, the theoretical model for pulsed laser ablation of sapphire is suggested and numerical analysis is carried out using the model. Sapphire ablation begins with plasma generation by the laser interaction with surface defects, impurities and contaminations in the initial stage of machining. Subsequent absorption of the visible laser beam can be explained by three mechanisms: metalization of sapphire surface due to the EUV radiation from the hot plasma, increments of surface roughness and temperature-dependent absorption coefficient. Comparison of the computation results with experimental observation indicates that the proposed model of sapphire is reasonable.

• Journal of Sensor Science and Technology
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• v.6 no.6
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• pp.430-436
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• 1997

A piezoresistive acceleration sensor for 30 G has been fabricated by silicon micromachining method using SDB(silicon direct bonding) wafer. The structure of the piezoresistive acceleration sensor consists of a seismic square pillar type mass and four beams. This structure was fabricated by reactive ion etching and chemical etching using KOH-etchant. The rectangular square structure is used in order to compensate the deformation of the edges due to underetching. The fabricated sensor showed a linear output voltage-acceleration characteristics and its sensitivity was about $88{\mu}V/V{\cdot}g$ from 0 to 10 G.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.2
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• pp.140-148
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• 2000

In this paper, using surface micromachining technology with thick photoresist and aluminum, an SLM(Spatial Light Modulator), which is applied to the fields of adaptive optics and pattern recognition system, was fabricated and the electromechanical properties of the fabricated micro SLM are measured. In order to maximize fill-factor and remove mechanical coupling between micro SLM actuators, the micro SLM is composed of three aluminum layers so that spring structure and upper electrode are placed beneath the mirror plate, and $10\times10$ each mirror plate is individually actuated. Also, the micro SLM was designed to be able to modulate phase and amplitude of incoming light in order to have a continuity of phase modulation of incoming light. In the case of amplitude and phase modulation, maximum vertical displacement is 4$\mum$, and maximum angular displacement is $\pm4.6^{\corc}$ respectively. The height difference of the fabricated mirror plate was able to be reduced to 1100A with mirror plate planarization method using negative photoresist(AZ5214). The electromechanical properties of the fabricated micro SLM were measured with the optical measurement system using He-Ne laser and PSD(position sensitive device).

• Journal of the Semiconductor & Display Technology
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• v.5 no.3 s.16
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• pp.5-10
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• 2006

This paper investigates cutting qualities after laser dicing and predicts the problems that can be generated by laser dicing. And through 3 point bending test, die strength is measured and the die strength after laser dicing is compared with the die strength after mechanical sawing. Laser dicing is chiefly considered as an alternative to overcome the defects of mechanical sawing such as chipping on the surface and crack on the back side. Laser micromachining is based on the thermal ablation and evaporation mechanism. As a result of laser dicing experiments, debris on the surface of wafer is observed. To eliminate the debris and protect the surface, an experiment is done using a water soluble coating material and ultrasonic. The consequence is that most of debris is removed. But there are some residues around the cutting line. Unlike mechanical sawing, chipping on the surface and crack on the back side is not observed. The cross section of cutting line by laser dicing is rough as compared with that by mechanical sawing. But micro crack can not be seen. Micro crack reduces die strength. To measure this, 3 point bending test is done. The die strength after laser dicing decreases to a half of the die strength after mechanical sawing. This means that die cracking during package assembly can occur.