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A via reliability test of PCB board using embedded MLCC was evaluated by HALT and Pressure Cooker Test PCT. The reliability of HALT was evaluated at 125 , 4Vr, and 12Hr. The purpose of this test was to verify the stability of the MLCC by predicting the lifetime of the PCB. The PCBT conditions were measured at 85% humidity and 2 atm, and the reliability of the PCBs under severe conditions than HALT was evaluated. The basic characteristics of MLCC size are 0603 (600x300um), Capacitance 100nF, thickness 150µm. The initial electrical characteristics of the MLCC size are 0603 (600 x 300 um), Capacitance 100 nF, thickness 150 um. The initial electrical characteristics of the MLCC were measured at a rated voltage (10V) with a capacitance value of 98 ~ 103 nF, a loss rate of 0.048%, and an insulation resistance of 1.08 x 1010 (omega). The HALT test results showed that all the measured samples showed a value of 1 x 107 (omega) or more, and passed for the HALT test. The PCBT test resulted in failure, and the first sample fell below the poor insulation resistance at the start of the PCBT test. In the case of the second sample, the insulation resistance dropped to less than the defective insulation resistance for more than 30 hours, and the third sample has an appropriate insulation resistance of 1.0x106 even for more than 60 hours. It is confirmed that there is the greatest the possibility of failure in the part between the embedded chip and via that Cu plating is performed to form via by fill plating. Therefore, it is necessary to optimize the plating thickness and size conditions because the embedded MLCC has a high probability that defects mainly occur in VIA crack or delamination

The size-fractionated aerosol samples have been collected at Gosan Site of Jeju Island during the spring season of 2010, in order to examine the chemical composition characteristics of the Asian Dust and Non-Asian Dust particles. The concentrations of , Al, and nss- in had tremendously increased during the heavy Asian Dust (March 20, 2010). The concentration ratios of Asian Dust to Non-Asian Dust for the soil species (nss-, , Al, Fe, Ti, Mn) were 12.2~30.7, meanwhile those for the anthropogenic species (nss-, , , , Zn, Pb, and Cu) were 2.9~7.8. During the heavy Asian Dust event, the concentration increase of in were much more apparent than those of nss- and , and the soil species (nss- and ) showed much higher concentration increase. The neutralization factor of was higher than that of . However, the neutralization factor of in was exceptionally high during the heavy Asian Dust, showing the evidence of heavy migration of soil particles. From the study for size fractionated particles, it was found that nss- and were mostly distributed in fine particle mode, on the other hand, existed evenly in both fine and coarse particle modes, and the soil species (nss-, Al, Fe, etc.) were mainly in the latter mode. During the heavy Asian Dust, in particular, the concentrations of , nss-, , Zn, and Pb had increased in coarse particle mode as well.

Decaphenylcyclopentasilane (DPCPS), a solution-processable precursor, was used to develop inorganic thin films with variable electromechanical properties in terms of their surface hardness and dielectric constant through thermal treatment. By varying the thermal treatment temperature and environmental conditions, the organic covalent bonds in DPCPS disappeared via various chain scission reactions and, consequently, an SiCxOy hard-surface coating was achieved by the orbital hybridization of carbon and silicon. The inorganic thin film developed at thermal treatment temperatures over 700 °C in this study reached a pencil hardness of 7H and dielectric constant of around 2.3–2.5, which is lower than that of silica, seemingly because of the carbon atoms incorporated in the atomic lattice structure of SiO2. The thermal treatment in an air environment gave higher dielectric constants than that in argon at

We propose a spheroid chip that uses removable cell trapping barriers and that is capable of forming and extracting multicellular spheroids. By using a conventional well plate and flask, it is difficult to form small-sized spheroids, which resemble avascular 3D cell-cell interaction. It was difficult to extract spheroids using conventional microchips and fixed cell trapping barriers. The proposed chip, however, facilitates both formation and extraction of spheroids by using removable cell trapping barriers formed by membrane deflection. The cell trapping barriers, formed at the membrane pressure of 50 kPa, hold the cells in the trapping region at a cell inlet pressure of 145.155 Pa. After incubation for 24 h, the trapped cells form uniform spheroids. We successfully extract the spheroids at a cell inlet pressure of 5 kPa after removing the membrane pressure. The extracted spheroids have a diameter of with a viability of . Using the proposed chip, uniform spheroids can be formed and these spheroids can be safely extracted for carrying out the post-processing of spheroids.

We present a simple, cost-effective, and fast fabrication process for three-dimensional (3D) microstructures; this process is based on multi-step electrochemical etching of metal foils which facilitates the mass production of 3D microstructures. Compared to electroplating, this process maintains uniform and well-controlled material properties of the microstructure. In the experimental study, we perform single-step electrochemical etching of aluminum foils for the fabrication of 2D cantilever arrays. In the single-step etching, the depth etch rate and bias etch rate are measured as and , respectively. Using the results of single-step etching, we perform two-step electrochemical etching for 3D microstructures with probe tips on cantilevers. The errors in height and lateral fabrication in the case of the fabricated structures are and , respectively; the surface roughness is .

TSP and PM2.5 atmospheric aerosols have been collected at Gosan site of Jeju Island, and their compositions were analyzed to understand the pollution characteristics. The composition ratios of nss (non-sea salt)- and were higher in Gosan site than those in other Korean background and urban sites. However the composition ratio of was conversely lower in Gosan site. From the study of aerosol components according to particle sizes, the anthropogenic nss-, and components were mostly existed in the fine particles. But the nss-, , and originated from soil and marine sources were distributed relatively in the coarse particles. In the seasonal comparison, the concentrations of nss-, Al, Fe, Ca and increased in spring season, and nss- showed higher concentration in summer and spring seasons. Based on the factor analysis, the atmospheric aerosols in Gosan site have been found to be influenced largely by anthropogenic sources, and next by marine and soil sources. The backward trajectory analyses showed that the concentrations of nss-, , Pb and nss- increased when the air mass moved from Chinese continent to Jeju area. On the other hand, their concentrations decreased when the air mass moved in from the North Pacific Ocean.

A highly conductive polymer-based bipolar plate is fabricated using phenolic resin and graphite for proton exchange membrane fuel cells (PEMFCs). In order to load graphite fillers up to 90 wt% and minimize the void volume, the wetting properties of the graphite and phenolic resin are key factors for ensuring high electrical conductivity of the bipolar plates through good contact and uniform dispersion of graphite fillers. Since the surface free-energies of the phenolic resin and graphite are significantly different at 107.77 and 43.3 mJ m−2, respectively, to give a high contact angle of 87.1°, methanol with 19.6 mJ m−2 of surface energy is incorporated to decrease the contact angle between the matrix and graphite to 11.2°. By adjusting the surface energy of the matrix system, the conductivity of a composite containing 90 wt% of graphite reaches 379 S cm−1. The air permeability of the composite containing 80 wt% of graphite is less than 5 × 10−6 cm3 cm−2 s without open pores. The flexural modulus ranges from 6700 to 11000 MPa for graphite loads between 60 and 80 wt%, respectively.

Insulating films for hand-held phone printed circuit boards (HHP PCBs) were manufactured from a variety of epoxy resin formulations. The epoxy resin formulations were prepared by varying the curing accelerator content. The curing behavior was investigated by viscosity measurements under isothermal conditions using a rheometer. The films were used in a general PCB manufacturing process and their adhesiveness to the electroplating layer was confirmed by peel strength tests. Their surface morphology after desmearing was examined by SEM. The peel strength of the epoxy films with a copper layer was directly dependent on their surface roughness.

Poly(vinylidene chloride-co-acrylonitrile) (P(VDC-co-AN))/silica hybrid composite systems were successfully prepared by the sol–gel method using an appropriate coupling agent and solvent system (1:1 ratio of THF – tetrahydrofuran and NMP – N-methyl-2-pyrrolidone) to enhance their water vapor and oxygen barrier properties while maintaining their coating transparency. A silane coupling agent consisting of 3-glycidyloxypropyltrimethoxysilane (GPTMS) was used to suppress the phase separation between the P(VDC-co-AN) and inorganic SiO2. The gas permeabilities of the hybrid composites were minimized by adding the silica component in the range of 10–20 wt%, and a thin coating at ca. 1–2 μm lowered the permeabilities of oxygen and water vapor to 2.88 × 10−10 ml mm m−2 s−1 GPa−1 and 1.12 × 10−5 g mm m−2 s−1, corresponding to improvements of 94.14% and 25.38%, respectively, compared to that of the pristine PET film. The optical transmittance of the hybrid coating was over 85% in the visible range (380–800 nm) and the surface roughness was less than 86.3 nm.

Sintering in a furnace under different thermal atmospheres of air, nitrogen (N 2 ) or N 2 bubbled through formic acid (FA/N 2 ) was carried out for a spin-coated gold nanoparticle (NP) ink. Temperatures of 200, 250 and 290 °C were applied for each atmosphere. The size of the NPs was measured by transmission electron microscopy and the decomposition temperatures of the solvent and the organic capping molecules of the ink were determined by thermo-gravimetric analysis. The changes in the microstructure of Au NP films after sintering were studied using the field emission scanning electron microscopy, X-ray diffractometry, atomic force microscopy and focused ion beam analysis. Organic residues remaining on the film were detected by Fourier transform infrared spectroscopy and sheet resistance was measured using a four point probe for the calculation of resistivity. Wire bonding tests on the Au film were performed for bondability. The Au NP films sintered under air showed neck growth as temperature increased, while the films sintered under N 2 showed grain growth, except for the film sintered at 290 °C. Coalescence and grain growth as well as porosity were observed in the film sintered under FA/N 2 . The infrared absorption peaks of stretch and deformation were found as organic residues, with C–O stretch peak only being detected in the film sintered under FA/N 2 . All of the samples represented a preferred Au (1 1 1) orientation. The film sintered under N 2 showed good quality compared with those sintered under air or FA/N 2 and the resistivity was about twice the bulk value. Wire bonding tests were successful in all the films sintered under air, N 2 or FA/N 2 atmospheres.

We investigated the sintering and consolidation phenomena of silver nanoparticles under various thermal treatment conditions when they were patterned by a contact printing technique on polyimide substrate films. The sintering of metastable silver nanoparticles commenced at 180 °C, where the point necks were formed at the contact points of the nanoparticles to reduce the overall surface area and the overall surface energy. As the temperature was increased up to 250 °C, silver atoms diffused from the grain boundaries at the intersections and continued to deposit on the interior surface of the pores, thereby filling up the remaining space. When the consolidation temperature exceeded 270 °C, the capillary force between the spherical silver particles and polyimide flat surface induced the permanent deformation of the polyimide films, leaving crater-shaped indentation marks. The bonding force between the patterned silver metal and polyimide substrate was greatly increased by the heat treatment temperature and the mechanical interlocking by the metal particle indentation.

To maximize power density, the volume of a fuel cell stack should be reduced by miniaturizing the stack components. In this study, thin flexible printed circuit board was utilized as a current collector in order to reduce an air-breathing monopolar stack's volume. Also, the effects of varying the geometry and opening ratios of the ports to the cathode on stack performance were evaluated in order to determine the optimal cathode structure. Use of the thin current collector and cathode port optimization resulted in an output of 3.5 W from an 18 cm 3 stack (power density of 350 mW/cm 2 ). The effects of orientation under passive air-breathing operation were determined to be nearly negligible. All data was measured at ambient pressure and temperature, baseline conditions for mobile fuel cell intended for use in consumer electronics.

The intrinsic improvement of fuel cell stack design is to minimize the volume and weight of fuel cell and is to maximize energy density. However, the bulky and massive stack is one of the main factors to undermine the chances to realize the higher energy density. Though the using bolts and graphite bipolar plates are common in a conventional stack, it may obstruct realizing a light weight and thinner stack. In this paper, the graphite bipolar plate is substituted with the flexible PCB and lightweight polycarbonate plates are used to separate the reactant gas. By using the plastic material as a separator, an innovative boltless stack assembly is originally possible through an ultrasonic welding. Instead of the bolt, the sharp edge of one plate melts and adjacent cell plates are bonded by the ultrasonic welding, which realizes the boltless and light weight stack assembly.

B2Mg2/3Nb4/3O7 (BMN) thin films were deposited at low temperature (< 200°C) on Copper Clad Laminates (CCL) with various Ar/O2 flow ratios and film thicknesses by sputtering system. 200 nm-thick BMN thin films were deposited at Ar/O2 = 10: 10 had rms roughness of 54.3 AA, capacitance density of 155 nF/cm2 at 100 kHz, dissipation factor of 0.017 and leakage current density of ∼10− 5 at 3 V. Surface roughness of the BMN thin films increased a little with increasing the film thickness. However leakage current density decreased and the dielectric constant of that was maintained at 40.

Inkjet printing is considered one of the most promising methods for patterning and materials deposition. The feasibility of employing inkjet technology for the creation of conductive pathways on printed circuit boards is addressed herein. Prediction of the width, length, and thickness of printed lines as a function of the dot diameter, resolution, and volume fraction of the particles in the ink is presented. Surface treatment of the substrate to promote desirable adhesion and wetting properties as well as the adjustment of the curing process to reduce the surface roughness of the printed traces were studied. In a sintering study, samples sintered at 250°C for 20 min showed a resistivity of 4.2 μΩ cm, which is approximately 2.6 times that of bulk silver. A low-temperature sintering method through the reduction of a metal salt is presented. The resistivity of printed samples sintered at 140°C for 30 min in the presence of silver nitrate with N,N-dimethylformamide showed a resistivity of 22.5 μΩ cm.

The importance of micro-fuel cell has been increased with the demand for uninterrupted power source in today's power hungry portable electronics. Currently, there is aggressive research going on to commercialize the micro-fuel cell by many laboratories and companies. The three different fuels feeding systems, i.e. pure hydrogen, pure hydrocarbons (alcohol, i.e. methanol and ethanol; formic acid and ethylene glycol) and on-board hydrogen from reformed hydrocarbons like methanol or other compound like water can be used for operating the micro-fuel cells. The current status on the research and development of micro-fuel cell with all the above three types of fuels have been discussed. The different substrate materials used in micro-fuel cells for the suitability of the portable electronics have also been stated. The design aspects of micro-fuel cells and micro-reformers are discussed here. The current state of commercialization of micro-fuel cells for portable electronics has been reviewed based on the open literature. The hurdles to overcome in order to commercialize in full phase have been reported, whenever possible. Some very new technologies which can make the micro-fuel cell into a very promising system with a simple operation have also been focused.

MEMS (micro-electro-mechanical system) fabrication technology was used to reduce the size of reformer and steam reforming catalyst was coated on the wall of micro-channels by a novel process. The comparison of performance with the packing the catalyst inside the micro-channels was also carried out. For that purpose, a process for packing catalyst inside micro- channels was developed. Serpentine type of micro-channels was used for both cases. Different issues for packing and coating inside the micro-channels like stability of the coating and durability of the system were examined.

By the development of high power LED for solid states lighting, the requirement for driving current has increased critically, thereby increasing power dissipation. Heat flux corresponds to power dissipation is mainly generated in p-n junction of LED, so the effective removal of heat is the key factor for long lifetime of LED chip. In this study, we newly proposed the silicon package for high power LED using MEMS technology and estimated its heat dissipation characteristic. Our silicon package structure is composed of base and reflector cup. The role of base is that settle LED chip at desired position and supply electrical interconnection for LED operation, and finally transfer the heat from junction region to outside. For improved heat transfer, we introduced the heat conductive metal plated trench structure at the opposite side of LED attached side. The depth and the diameter of trench were 150 and 100um, respectively. Copper with high thermal conductivity than silicon was filled in trench by electroplating and the thickness of copper was about 100um. Reflector cup was formed by anisotropic wet etching and then, silicon package platform could be fabricated by eutectic bonding between base and reflector cup. The thermal resistance of silicon package was about 6 to 7K/W from junction to case, and also, thermal resistance reduction of 0.64K/W was done by metal plated trench. This result could be comparable to that of other high power LED package. Our silicon package platform is easy to be expanded into array and wafer level package. So, it is suitable for future high efficiency and low cost package.

In this study, we attempt to present a direct synthesis of narrowly dispersed silver nanoparticles in a highly concentrated organic phase ( > 2 M ) without the use of a size-selection process. The fully organic phase system contains silver nitrate as a silver precursor, n-butylamine as a medium dissolving the silver salt, dodecanoic acid as a capping molecule, toluene as a medium, and NaBH4 as a reducing reagent. Even using only generic chemicals, monodisperse silver nanocrystals with a size of 7 nm were easily synthesized on the 100-g scale in a 1-L reactor. In addition, systematic studies revealed that the silver nanocrystals synthesized through in situ ligand exchange were stabilized through bidentate bridging of carboxyl groups in dodecanoic acid.

The operation of a micro-electro-mechanical system (MEMS)-based micro-reformer was investigated for application in a cell phone. Different aspects like the time required to attain the desired temperature of the system, the time required to get the required hydrogen flow, catalyst durability, flow uniformity of the mixture of methanol and water and volume of the total system were considered. A loading procedure for the catalyst in the micro-reformer was developed. Catalyst deactivation was observed after operating continuously for 8 h, but it regained its original activity after the reformer was shut down for at least 2 h. The deactivation of the catalyst was analyzed by catalyst characterization. The comparison of the performance between a parallel channeled and serpentine channeled micro-reformer was carried out. The performance with the serpentine channeled micro-reformer was always higher than with parallel channeled micro-reformer. The shorter residence time in the parallel-channeled micro-reformer may be one of the reasons behind its low activity.

Gold nanoparticles and nanorods have been synthesized in the ionic cluster network of Nafion using a liquid-phase chemical impregnation/reduction process seemingly visualizing the phase-separated hydrated cluster network of Nafion. The spherical shape of the hydrated clusters is clearly seen by the replicated gold nanoparticles with diameters of 5-6 nm. The gold nanoparticles grow through the Nafion cluster network to form gold nanorods with diameters of 5-15 nm, which compare well to the previously reported small-angle X-ray scattering results. Tiny channels between adjacent spherical clusters are also observed, which expand to form a rod structure by a reorganization of ion exchange sites and an elastic deformation of Nafion polymer chains. The gold nanorods become interconnected in a cascadic feature, and a tripod-shaped nanorod structure is one of the most commonly observed structures of the replicated gold. Although further study should be performed, the synthesized gold may be used to visualize the hydrated cluster and the network structure of Nafion, which could be used as important information in identifying the morphology and ion transport phenomena of Nafion.

The ultra-drawing process of an ultra high molecular weight polyethylene (UHMWPE) gel film was examined by incorporating linear low-density polyethylene (LLDPE) and BaTiO3 nanoparticles. The effects of LLDPE and the draw ratios on the morphological development and mechanical properties of the nanocomposite membrane systems were investigated. By incorporating BaTiO3 nanoparticles in the UHMWPE/LLDPE blend systems, the ultra-drawing process provided a highly extended, fibril structure of UHMWPE chains to form highly porous, composite membranes with well-dispersed nanoparticles. The ultra-drawing process of UHMWPE/LLDPE dry-gel films desirably dispersed the highly loaded BaTiO3 nanoparticles in the porous membrane, which could be used to form multi-layered structures for electronic applications in various embedded, printed circuit board (PCB) systems.

The microstructure for high-density thermal inkjet (TIJ) is proposed to overcome the defect due to the limit of the nozzle density in conventional TIJs. To bring high-density TIJ, the heat transfer of diamonds by means of placing heaters on sidewall of ink inlet is used in order to minimize the area occupied by the heaters. In addition, manifold, inlet, pressure chamber and nozzle concerning the flow of ink are placed in-line. To demonstrate feasibility, TIJ for bubble visualization test is designed and fabricated. Diamond is deposited on the sidewall of inlet with Hot Filament CVD (HFCVD). The trench filling method and the side deposition method are executed for the vertical sidewall of diamond. To solve the problem for direct CVD deposition on Pt layer, Ta film is utilized as a passivation layer in the fabrication processing. The generated bubble confirms the possibility of the bubble formation by heat transfer of diamond.

This paper presents a failure analysis result for enhancing the reliability of thermal inkjet printhead. A novel inkjet printhead is fabricated using MEMS process, and we analyze the failure mechanism of inkjet head based on detailed experimental observations and numerical simulations. The failures presented in this work showed three primary factors influencing the failure modes and lifetime of printhead; bubble cavitation damage, thermal fatigue, and electromigration of heater. The design modification of micro heater to avoid an early stage of failure by electromigration yields the reliability enhancement of thermal inkjet printhead.

A test system to improve the reliability of a printhead was developed and various printheads was tested. We developed a thermally driven monolithic inkjet printhead comprising dome-shaped ink chambers, thin film nozzle guides and omega-shaped heaters integrated on the top surface of each chamber. In a durability test of an inkjet printhead, the test system automatically detects a heater failure using a Wheatstone bridge circuit. Various models were designed and tested to develop a more reliable printhead. Three design parameters of the thickness of heat-transmission layer, reinforcement layer, and insulation layer were investigated in the test. Specially, the reinforcement layer was introduced to improve the lifetime of printhead. The thicker the heat-transmission layer as well as the insulation layer, the longer the life of the printhead. The lifetime of a heater with a reinforcement layer was longer than the lifetime of a heater without a reinforcement layer.

This paper presents design modifications of a backshooter type inkjet printhead, DomeJet, to enhance the firing frequency. DomeJet is a thermally driven monolithic inkjet printhead that consists of dome-shaped ink chambers and omega-shaped heaters over the chambers. Since it is monolithic, the manufacturing is very cost effective. As the firing frequency increases, the residual heat accumulated in heater layer may cause unstable droplet ejection. Thus, an efficient heat passage is necessary to increase the firing frequency. Contrary to a roofshooter architecture printhead, a backshooter type printhead has disadvantage in heat release since the heater is confined to a thin film which has low thermal conductivity. In this study, four models are proposed and studied. Compared to the basic model of DomeJet, all the proposed models are found to improve heat dissipation capability. The best performing model is found to operate at a frequency of 40 kHz, a much higher frequency than 15 kHz of the basic model.

A novel thermal inkjet printhead with monolithically fabricated nickel nozzle plate on SOI wafer has been proposed for the first time. A chamber and a restrictor are implemented on the 40 μm thick top silicon layer, and a nozzle plate covering heater layers is monolithically fabricated on them. Unlike the general back-shooters, the inkjet printhead reported here is a kind of back-shooter, which has a chamber and a restrictor with arbitrary shape by utilizing the silicon dioxide etch-stop layers in the bottom and sidewalls of chamber. Moreover, the electroplating process for nozzle, followed by placing the chamber underneath the heater layer, is performed on a planar surface, resulting in more uniform and reliable control of nozzle size. The new design was applied for monochrome inkjet printhead, which has 56 nozzles in two columns with real 600 NPI (nozzle per inch), and showed good performances such as a drop velocity of 12 m/s, a drop volume of 30 pl, and a maximum firing frequency of 12 kHz for single nozzle ejection. From nozzle by nozzle inspection, we observed the uniformity variation of less than 4% in drop speed as well as drop volume. The monolithic fabrication process resulted in a good uniformity and is expected to have superior manufacturing yield to the nozzle assembly process.

A testing system was developed to improve the reliability of printhead and several printheads were tested. We developed a thermally driven monolithic inkjet printhead comprising dome-shaped ink chambers, thin film nozzle guides, and omega-shaped heaters integrated on the top surface of each chamber. To perform a fatigue test of an inkjet printhead, the testing system automatically detects a heating failure using a Wheatstone bridge circuit. Various models were designed and tested to develop a more reliable printhead. Two design parameters of the width of reinforcing layer and heater were investigated in the test. Specially, the reinforcing layer was introduced to improve the fatigue life of printhead. The life-span of heater with a reinforcing layer was longer than that without a reinforcing layer. The wider the heater was, the longer the life of printhead was.

A novel high-density thermal inkjet (TIJ) was proposed to overcome the defect due to the limitations of the nozzle density in conventional TIJs, and its feasibility was verified by a bubble visualization test. To develop the high-density TIJ, two concepts were introduced. One is an original method to use heat transfer from CVD diamond by means of placing heaters on the sidewall of the ink inlet in order to minimize the area that is occupied by the heaters. The other is the concept of placing some parts concerning the flow of ink (e.g. manifold, inlet, pressure chamber and nozzle) in line. In order to determine the dimensions of the suggested model, heat transfer analysis has been performed and shapes of the heater based on the analysis have been described. To demonstrate the feasibility of these concepts, the TIJ was designed and fabricated for the bubble visualization test. The CVD diamond on the sidewall was deposited using hot filament CVD (HFCVD). The bubble generated has a better symmetry as the power applied increases, which confirms the possibility of bubble formation by heat transfer from diamond. In addition, there was a difference in the rate of bubble growth between the top and the bottom of the CVD diamond.

This paper describes a thermally driven monolithic inkjet print head, DomeJet, that consists of dome-shaped ink chambers and thin film nozzle guides. Nozzle guides are fabricated by anisotropic etching after PECVD oxide passivation of their side walls. Each of the ink chambers and channels are fabricated by isotropic dry etching process using XeF/sub 2/. Omega or ring type polysilicon heaters are integrated on top of each chamber. Fifty-six nozzles are embedded at two columns on each chip where their pitch is 1/150 inch at each column. A pulse voltage of 2.6 /spl mu/s has been used in initial printing tests, resulting in 36 /spl mu/m diameter dots on a HP transparent film that was placed 1 mm away from the nozzle 18 /spl mu/m wide. The drop volume and velocity are measured to be 4 pl and 12 m/s, respectively. A printed image is successfully obtained using the fabricated head installed to a Samsung inkjet printer.

A surface-micromachined silicon accelerometer with a novel concept, which has a stiffness tuning capability to improve the sensor resolution, is developed. Imposing an electrostatic force to the electrodes reduces the stiffness of the sensor structure. By adopting the stiffness tuning, the initially stiff structure guarantees the stability of fabrication, and the reduced stiffness, only along the sensing direction, produces the improved resolution. One of the major improvements in the developed accelerometer is the branched comb-finger type electrode which senses the relative position between the mass and the electrode. Maintaining the same capacitance variation, such electrodes allow a larger initial gap between the mass and the electrode, so that the clash problem can be easily eliminated. The accelerometer was successfully fabricated with the active size of 650×530 μm 2 , the 7-μm thick polysilicon structure, and a proof mass of about 1 μg. Experimental results show that the equivalent noise level of the accelerometer is improved by 30 dB through the stiffness tuning. The accelerometer has the bandwidth of 350 Hz, linearity of 0.3% FS, and sensing range of 50 g.

A novel dual-axis microgyroscope fabricated by a surface micromachining process is developed. A 7.0-μm thick polysilicon layer deposited by LPCVD (Low Pressure Chemical Vapor Deposition) is used for the vibrating structure. The microgyroscope is based on the angular vibration of the four plates with closed-loop rate detection. The comb-driven rotational body tilts to each input-axis parallel to the substrate and the tilting motion is sensed with capacitance change between the bottom electrode and the structure. The two tilting modes enable the sensor to detect two-input axis angular rate simultaneously within a single-chip. In particular, the structure utilizes a simple force-balancing torsional torque which does not need another top electrode layer to reduce the intrinsic non-linearity of a capacitance-type sensor. The vibrating structure is strongly damped by air, so the gyroscope is tested in a high vacuum chamber for a high quality factor with hybrid signal-conditioning integrated circuit. The experiment resulted in a noise equivalent signal of 0.1°/s.

A tunable vibratory microgyroscope has been fabricated by surface-micromachining technology. The 7.5 μm thick polysilicon structural layer is deposited using LPCVD at 625 °C. The resonance frequency in the detection mode is designed to be higher than that in the driving mode so that the gyroscope could be matched to the resonance frequencies by applying an inter-plate d.c. bias. The gyroscope is driven in a resonant state by electrostatic force and the output detected is due to a capacitance change between the plate and the polysilicon electrode. The resonance frequencies of the gyroscope in the driving and detection directions are measured to be 10.48 and 10.93 kHz, respectively. The resonance frequency in the detection direction can be shifted to 10.52 kHz by applying a tuning voltage of 4.0 V. The quality factor and resonance frequency of the detection mode are significantly affected by ambient pressure. The electrical noise equivalent rate of this device is about 0.1 ° s −1 at 10 −2 torr.

This paper presents a multicellular spheroid chip capable of forming and extracting three-dimensional (3D) spheroids using removable cell trapping barriers. Compared to the conventional macro-scale spheroid formation methods, including spinning, hanging-drop, and liquid-overlay methods, the recent micro-scale spheroid chips have the advantage of forming smaller spheroids with better uniformity. The recent micro spheroid chips, however, have difficulties in extracting the spheroids due to fixed cell trapping barriers. The present spheroid chip, having two PDMS layers, uses removable cell trapping barriers, thereby making it easy to form and extract uniform and small-sized spheroids. We have designed, fabricated and characterized a 4 × 1 spheroid chip, where membrane cell trapping barriers are inflated at a pressure of 50 kPa for spheroid formation and are deflated at zero gauge pressure for simple and safe extraction of the spheroids formed. In this experimental study, the cell suspension of non-small lung cancer cells, H1650, is supplied to the fabricated spheroid chip in the pressure range 145-155 Pa. The fabricated spheroid chips collect the cancer cells in the cell trapping regions from the cell suspension at a concentration of 2 × 10(6) ml(-1), thus forming uniform 3D spheroids with a diameter of 197.2 ± 11.7 μm, after 24 h incubation at 5% CO(2) and 37°C environment. After the removal of the cell trapping barriers, the spheroids formed were extracted through the outlet ports at a cell inlet pressure of 5 kPa. The cells in the extracted spheroids showed a viability of 80.3 ± 7.7%. The present spheroid chip offers a simple and effective method of obtaining uniform and small-sized 3D spheroids for the next stage of cell-based biomedical research, such as gene expression analysis and spheroid inoculation in animal models.

This paper presents a multicellular tumor spheroid formation and extraction chip using removable cell trapping barriers. The previous spheroid formation chips using fixed cell trapping barriers have difficulties in extracting the formed spheroids. The present spheroid chip, however, achieves simple spheroid extraction using the removable cell trapping barriers formed by membrane inflation. A 4 by 1 array of the spheroid chips has been designed, fabricated and characterized. The experimental study demonstrates that the spheroid chip is capable to form, culture, and extract the multicellular tumor spheroids having the diameter of 197.2α11.7µm with the cell viability of 80.3α7.7%. The uniform size and viability of the extracted spheroids increase the continuity, effectiveness and reliability of the next stage of biomedical spheroid study.

The vapor-phase polymerization (VPP) of poly(3-hexylthiophene) (P3HT) was achieved successfully as an alternative method to conventional solution-based thin film fabrication. Using Fe(III)Cl(3).6H(2)O, a spontaneous reaction of 3-hexylthiophene monomers resulted in the rapid formation of conducting P3HT thin films directly on substrates, such as glass, indium-tin-oxide, and poly(ethylene terephthalate), at thicknesses ranging from 50 to 1000 nm. The VPP of P3HT was achieved using ferric chloride hexahydrate and a 1:1 ratio of a methanol/ethanol mixture as the solvent system. The developed VPP technique can provide good processing consistency with an electrical conductivity, a transmittance, and a surface roughness of approximately 10(-2) S/cm,90%, and10 nm, respectively.

In this paper, we report the catalytic activity of the Sn/Bi alloy beads and its acceleration of the exothermic epoxy curing reactions in various thermal conditions and bead compositions. As being used as low-melting solder balls in electronic interconnection processes with various epoxy systems, it was found that the Sn/Bi beads substantially lowered the exothermic peak temperature of the diglycidyl ether of bisphenol A (DGEBA)/anhydride systems in up to ca. 140 degrees C depending on different types of anhydride curing agents. The catalytic activation of Sn/Bi powder was initiated with a small amount of Sn/Bi powder, for example, lowering ca. 50 degrees C of the exothermic peak temperature by adding only 0.1 vol% of Sn/Bi powder. The catalytic capability of the powder was increased by using smaller sized beads corresponding to larger catalytic surface area at the same volume fraction. Exhibiting a latent catalytic effect, the catalytic activity of Sn/Bi powder was remained latent at temperatures lower than 100 degrees C in isothermal conditions.

We developed a low cost small port-count ROADM(Reconfigurable Optical Add-Drop Multiplexer) using simple MEMS (Micro Electro-Mechanical System) type 2times2 OSWs (Optical Switches) and VOAs (variable optical attenuators). The ROADM module consisting of components all developed in-house performed fast and reliable add/drop function with channel equalisation. The output power flatness was controlled to less than 0.5 dB over four CWDM channels

This paper presents a development of a 3D motion sensor IC which detects inertial movements and earth's magnetic fields for a compass heading. It consists of a 3-axis accelerometer, a 2-axis geomagnetic sensor, and a microcontroller. An automatic calibration and measurement system is developed to reduce test lead time. For the geomagnetic sensor part, an accuracy of plusmn5 degrees, a resolution of plusmn1 degrees, and a linearity of plusmn1% in full scale range have been achieved. The accelerometer has a full measurement range of plusmn2g. Both sensitivity of 819 count/g with a 12-bit analog-to-digital converter and a linearity of plusmn0.5% in full scale have been achieved. While driving voltage can operate between 2.7 and 3.3 V, current consumption is 3.2 mA at 2.8 V. Thorough reliability test is performed and the sigma level of geomagnetic sensor heading accuracy is 5.6, and that of accelerometer sensitivities are 4.6, 5.6, and 4.5 for x, y, and z axis respectively. The dimension of a packaged chip is 8.3 mm X 5.3 mm X 1.5 mm.

We have improved charge character on the surface of phosphor particles by dispersed sub micro miter size sulfonate polystryrene beads and polyelectrolyte dispersant. The surface of TAG phosphor was analyzed with SIMS-TOF. Many hydrocarbon molecules were existed on the TAG phosphor. We could exchange the hydrocarbon into polyelectrolyte and sulfonated polystyrene beads. Characterization of the chemical bonging of polystyrene beads adhered on the surface of the TAG phosphor was archieved with x-ray photoemission spectroscopy (XPS) and FT-Raman. We could measure light efficiency of the white LED with integrating sphere spectrophotometer. Adhering sub micro miter size sulfonated polystyrene beads on the surface of TAG phosphor has enhanced extraction efficiency of light from phosphor. The sulfonated ligand and reduced difference of refractive index between phosphor and encapsulant material are responsible for the enhancement of extraction efficiency light from phosphor. Additional increase of light extraction has been observed when the phosphor particles were coated only on and near the LED chip. Surface modified phosphor particle and phosphor layer have improved LED light efficiency about ten percents.

This paper presents the fabrication of a micro droplet ejector for the application of digital printing system. The ejector makes the ink droplets of approximately 80 squaremum diameter on demand. The ejecting system is the type of face-shooter. The method of actuating membrane is bending mode using d31 of PZT. The size of ejector is 27.6 mm x 27.75 mm x 1.1 mm, and the pitch between nozzles is 2.54 mm, 10 npi. The nozzle and restrictor are very important part for the performance of the ejector such as droplet size and velocity. Therefore, the roundness and straightness of nozzle and depth profile of the restrictor have an influence on the characteristic of droplet. Those are made by deep silicon etching technique for the accuracy and uniformity. The ejector is successfully operated and the measured ejection speed, size of droplet and the ejection frequency are 1 m/s, 80 mum and 1 kHz, respectively.

This paper presents the effect of driving waveform for piezoelectric bend mode inkjet printhead with optimized mechanical design. Experimental and theoretical studies on the applied driving waveform versus jetting characteristics were performed. The inkjet head has been designed to maximize the droplet velocity, minimize voltage response of the actuator and optimize the firing frequency to eject ink droplet. The head design was carried out by using mechanical simulation. The printhead has been fabricated with Si(100) and SOI wafers by MEMS process and silicon direct bonding method. To investigate how performance of the piezoelectric ceramic actuator influences on droplet diameter and droplet velocity, the method of stroboscopy was used. Also we observed the movement characteristics of PZT actuator with LDV(laser doppler vibrometer) system, oscilloscope and dynamic signal analyzer. Missing nozzles caused by bubbles in chamber were monitored by their resonance frequency. Using the water based ink of viscosity of 4.8 cps and surface tension of 0.025N/m, it is possible to eject stable droplets up to 20kHz, 4.4m/s and above 8pL at the different applied driving waveforms.

The demand for miniaturized magnetic passive devices in power modules has been rapidly growing with mobile handset technology. Thus, we developed a minimum construction and sized planar inductor for micro DC-DC converters with a ferrite plating method and conventional flexible PCB processes. The ferrite plating process made it possible to deposit Ni-Zn spinel ferrite on a Cu electroplated planar coil without a non-magnetic insulation layer. These samples of a planar inductor with ferrite layers achieved a high quality factor of 17/spl sim/24 at 3/spl sim/5 MHz and inductance of 1.25/spl sim/1-30 /spl mu/H in 6.0/spl times/6.0/spl times/0.19/spl sim/0.20 mm/sup 3/, respectively. In addition, the estimated power loss of this developed inductor at 5 MHz in a switching buck DC-DC converter was about 15.7%. It showed excellent capability for portable power systems.

This paper presents a failure analysis result for enhancing the reliability of thermal inkjet printhead. A novel inkjet printhead is fabricated using MEMS process, and we analyze the failure mechanism of inkjet head based on detailed experimental observations. The design modification of micro heater to avoid an early stage of failure yields the reliability enhancement of printhead.