Byung-Han Ko

Vibration reduction of MLCC considering piezoelectric and electrostriction effect

In this study, vibration of MLCC was analyzed considering nonlinear characteristic of BaTiO3. By construction of FE model of MLCC, total deformation was classified into piezoelectric and electrostrictive deformation. As piezoelectric coefficient is largely influenced by polarization of dipoles, poling process was proceeded to reduce the piezoelectric deformation. 4 variables were considered factors of poling process; heating temperature, poling voltage, dc voltage input time, and aging time. The effects of poling process were verified by experiment and FEA; vibration was reduced by 39.7%. For poled MLCC soldered on simple rectangular circuit board, sound pressure level was reduced by more than 4 times compared to unpoled state.

Study on effective piezoelectric coefficient for finite element analysis of multi-layer ceramic capacitor

Effective piezoelectric coefficient for finite element method of multi-layer ceramic capacitor was calculated in this study considering three factors; reduction ratio of the number of layer in finite element model, electrostriction, and applied DC voltage. Fundamental and second harmonic frequency of vibration response was measured when MLCC is operated under sinusoidal AC voltage and various DC voltage. Vibration measurements were separated into piezoelectric and electro-strictive vibration. Using finite element analysis, piezoelectric and electrostrictive coefficients were calculated and effective piezo-electric coefficients were also calculated.

Modal Analysis of Optical Disk Rotating at 15,000 rpm Close to a Rigid Wall

The rotational speed of optical disks must be above 15,000 rpm owing to the required high data-transfer rates. At these speeds, the airflow between the rotating disk and a rigid wall is important when identifying the dynamic characteristics of the disk in a slim optical disk drive. This airflow is simulated using a numerical model and examined by a closed-form modal analysis. The calculated dynamic characteristics of the rotating disk can be used to predict the nonrepeatable runout for the servo controller design.

Vibration Reduction of MLCCS Using Vibration-Canceling Effects of Poling Process

MLCC vibrates due to its piezoelectric characteristics and it makes circuit board vibrate and lead to acoustic noise. In order to reduce vibration, piezoelectric coefficient should be reduced. In this study, poling process was used to decrease piezoelectric coefficient. Due to the electrostriction coefficient, response at fundamental frequency can be cancelled by applying voltage to opposite direction. Through the experiment, vibration-cancelling voltage increases as the poling voltage increases. Also, vibration-cancelling voltage increase inversely proportion to MLCC’s capacitance. By applying proper DC bias after poling process, vibration can be reduced.Copyright

Characteristic Analysis and Design of a Precise Manipulation of Microparticle using Surface Acoustic Wave Device

Surface acoustic wave(SAW) device is used for transporting and patterning micro-scale particles such as cells. In this research, velocity of particles was investigated moved by SAW device with two types of interdigital electrode transducers(IDTs) under various conditions. SAW devices which have single IDTs and double IDTs were designed and fabricated. On the previous studies, resultant velocities of particles were predicted considering output power and power ratio between IDTs-shape. For more accurate prediction, power loss in SAW device and a power difference between two types of IDTs-shape were considered. Maximum error between the test results and predicted values was 5 % so the power loss must be considered in the velocity prediction of the particles.

Study on Soldering Method of Multilayer Ceramic Capacitors for Vibration Reduction

Owing to the excellent electrical characteristics, multilayer ceramic capacitors (MLCCs) are widely used in a variety of electronic devices nowadays. The accompanying acoustic noise of MLCC related to its vibration is one of the most important factors when selecting MLCCs for specific applications. To evaluate the noise more efficiently, this study investigates a method to build simplified finite element models of MLCC. In addition, vibration analysis has been performed with the simplified model to discuss how structural parameters influence the vibration of MLCC. According to the findings in the study, suggestions and optimized solder design are given to lower the vibration of MLCC. In short, the main aim of this study is to present a new soldering method for MLCC vibration and noise reduction.Copyright