• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.10
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• pp.805-811
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• 2000

Reliability of PBGA(plastic ball grid array) package is weak compared with normal plastic packages. The low reliability is caused by low resistance to the popcorn cracking, which is generated by moisture absorption in PCB(prited circuit board). In this paper, plasma treatment process was used and we analyzed its effects to interface adhesion. The contents of C and Cl decrease after plasma treatment but those of O, Ca, N relatively increase. The plasma treatment improves the adhesion between EMC(epoxy molding compound) and PCB(solder mask). The grade of improvement was over 100% Max, which depends on the properties of EMC. The RMS(root mean square) roughness value of the solder mask surface increases to plasma treatment. There is little difference of adhesion in RF power and treatment time.

• The KIPS Transactions:PartA
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• v.8A no.3
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• pp.269-278
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• 2001

Routing region modeling method of auto_routing systems are use the grid and the non-grid type. Though grid type has a few electrical and physical element on PCB, grid type has disadvantage which decrease the auto-routing speed dur to constraint with board and gird size. Thus it increase the memory capacity, Non-grid type(Shape baed type) use the region processing type, so it has 44.2% memory decrease effect than grid type in routing region. Thus, via number has 55% decrease effect, total routing time is increased 83.8% than conventional PCB system. In this paper we developed high speed PCB auto-routing system without memory waste by using shaped type applicant with auction algorithm which reaching the destination from one-point with best speed and solving the path problem. Also, this system developed by Visual C++ in IBM Pentium computer Window environment, and compatible with other PC.

• The KIPS Transactions:PartA
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• v.11A no.4
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• pp.267-276
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• 2004

The modeling methods of routing region used in the automatic placement/routing system are a grid and non-grid. Because the gird method is curbed by its size and a board if the electrical and physical elements on PCB are of small quantity, it has many memories. Therefore, it has demerit which decreases the speed of automatic placement/routing. The Shape-based type, non-grid method, makes the shapes exist as an in dividual element in a memory by using a region-processing method. Each individual element needs very small memory since it has its unique data size. Therefore, this paper aimed to develope the automatic placement/routing system which can automatically place and route the PCB without dissipation of memory at a high speed. To this aim, the auction algorithm method was applied which can make the memories be most rapidly reached from the original point to various destinations. Also, this system was developed by the Visual C++ in the Widows environment of IBM Pentium computer in order to use it in an individual PC system.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.1
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• pp.40-45
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• 2014

This study examines the system and process of battery stored energy in vehicles and suggest the effective area for the use of V2G(vehicle-to-grid) from Jeju Smart Grid Demonstration Project. V2G means technology of electric power transmission from the battery of electric-drive vehicles to state grid. As for the increasing of effectiveness for demand-side control, V2G is a very good alternative. In the U.S., the utilization of electric vehicles is under 40% on average. In this case, we can use he battery of electric vehicle as role of frequency regulation or generator of demand-side resource. V2G, which is the element of Smart Transportation, consists of electric vehicle battery, BMS(battery management system), OBC(on-board charger), charging infrastructure, NOC(network operating center) and TOC(total operation center). V2G application has been tested for frequency regulation to secure the economical efficiency in the United States. In this case, the battery cycle life is not verified its disadvantage. On the other hand, Demand Response is required by low c-rate of battery in electric vehicle and It can be small impact on the battery cycle life. This paper concludes business area of demand response is more useful than frequency regulation in V2G application of electric vehicles in Korea. This provides the opportunity to create a new business for power grid administrator with VPP(virtual power plant).

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.2005-2006
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• 2011

Due to the advantages of small sizes, more I/O ports, etc., Ball Grid Array (BGA) has been used in the production of printed circuit board (PCB). However, BGA voids can degrade the performance of the board and cause failure. To automatically detect the voids in X-ray image, a novel blob filter that makes use of the local image gradient magnitude is proposed in this paper. The utilization of the local image gradient magnitude makes the proposed filter invariant to the image brightness, void shape, void position, and component interference. Furthermore, different sizes of box filters are employed to analyze the image in multi-scale, and as a result, the proposed blob filter is robust to void size. Experimental results show that the proposed method can obtain void detection accuracy up to 96.104% while keep low false ratio.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.1
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• pp.92-98
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• 2014

In this paper, the reconfigurable frequency selective surface for C-band was designed using patch array and grid structure. Frequency reconfigurability was obtained by varying the capacitance from varactor diode. From the optimized design parameters, we fabricated the reconfigurable frequency selective surface using the FPCB(Flexible Printed Circuit Board) and commercial varactor diode and measured the frequency reconfigurability for different bias voltage. From the measurement results, proposed structure has the wideband operating frequency of 6.6~7.6 GHz. We can applied this proposed structure to the smooth curved surface like as radome of aircraft or warship.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.05a
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• pp.138-141
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• 2002

There are continuous efforts in the electronics industry to a reduced electronic package size. Reducing the size of electronic packages can be achieved by a variety of means, and for ball grid array(BGA) packages an effective method is to decrease the pitch between the individual balls. Chip scale package(CSP) and BGA are now one of the major package types. However, a reduced package size has the negative effect of reducing board-level reliability. The reliability concern is for the different thermal expansion rates of the two-substrate materials and how that coefficient CTE mismatch creates added stress to the BGA solder joint when thermal cycled. The point of thermal fatigue in a solder joint is an important factor of BGA packages and knowing at how many thermal cycles can be ran before failure in the solder BGA joint is a must for designing a reliable BGA package. Reliability of the package was one of main issues and underfill was required to improve board-level reliability. By filling between die and substrate, the underfill could enhance the reliability of the device. The effect of underfill on various thermomechanical reliability issues in $\mu$BGA packages is studied in this paper.

• IEMEK Journal of Embedded Systems and Applications
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• v.17 no.2
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• pp.123-128
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• 2022

This paper proposes a mobile robot platform for education that can experiment with various autonomous driving algorithms such as obstacle avoidance and path planning. The platform consists of a robot module and a remote controller module, both of which are based on the Arduino Nano 33 IoT embedded board. The robot module is designed as a differential drive type using two encoder motors, and the speed of the motor is controlled using PID control. In the case of the remote controller module, a command to control the robot platform is received with a 2-axis joystick input, and an elliptical grid mapping technique is used to convert the joystick input into a linear and angular velocity command of the robot. WiFi and Zigbee are used for communication between the robot module and the remote controller module. The proposed robot platform was tested by measuring and comparing the linear velocity and angular velocity of the actual robot according to the linear velocity and angular velocity commands of the robot generated by the input of the joystick.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.323-324
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• 2016

In this paper a high efficiency bidirectional resonant converterfor Vehicle-to-Grid applications (V2G) is proposed.The proposed converter has adopted an LC auxiliary circuit in the third winding of the transformer. With the proposed method full softswitching can be ensured in all switches over a wide range of loadsand the secondary ringing can be removed with no additional snubber or clamp circuitry.In addition, since the proposed resonant converter is able to operate at an almost constant resonant frequencyregardless of the load, CC/CV charge of the battery can be simply implemented with high efficiency. A 3.3 kW bidirectional converter for On-Board Charger of Electric Vehicle is implemented to verify the validity of the proposed method. The experimental results show the high efficiency characteristics of the proposed converter over the wide range of load in both charge and discharge mode. The maximum efficiency of the proposed system was 98.13 % at 2.3 kW during the constant voltage mode charge operation.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.192-194
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• 2018

In this paper a new single-stage ac-dc converter with high frequency isolation and low components count is introduced. The proposed converter is constructed using two interleaved boost circuits in the grid side and non-regulating full bridge in the DC side. An optimized switching is implemented on the two interleaved boost circuits resulting in a ripple-free grid current without a ripple cancellation network; hence very small filter inductors are used. A simple and reliable closed-loop control system is easily implemented, since the phase-shift angle is the only independent variable. Moreover, current imbalance is avoided in the presented topology without current control loop in each phase. The proposed charger charges the battery with a sinusoidal-like current instead of a constant direct current. ZVS turn on of all switches is achieved throughout the operation in both directions of power flow without any additional components.