• Journal of the Semiconductor & Display Technology
• /
• v.20 no.2
• /
• pp.126-130
• /
• 2021

The ball grid array is one of the packaging methods that used in high density printed circuit board. Solder void defects caused by voids in the solder ball during the BGA process do not directly affect the reliability of the product, but it may accelerate the aging of the device on the PCB layer or interface surface depending on its size or location. Void inspection is important because it is related in yields with products. The most important process in the optical inspection of solder void is the segmentation process of solder and void. However, there are several segmentation algorithms for the vision inspection, it is impossible to inspect all of images ideally. When X-Ray images with poor contrast and high level of noise become difficult to perform image processing for vision inspection in terms of software programming. This paper suggests the solution to deal with the suggested problem by means of using Mask R-CNN instead of digital image processing algorithm. Mask R-CNN model can be trained with images pre-processed to increase contrast or alleviate noises. With this process, it provides more efficient system about complex object segmentation than conventional system.

• Wind and Structures
• /
• v.32 no.3
• /
• pp.205-217
• /
• 2021

Cold regions with high air density and wind speed attract wind energy producers across the globe exhibiting its potential for wind exploitation. However, exposure of wind turbine blades to such cold conditions bring about devastating impacts like aerodynamic degradation, production loss and blade failures etc. A series of wind tunnel tests were performed to investigate the effect of icing on the aerodynamic properties of wind turbine blades. A baseline clean wing configuration along with four different ice accretion geometries were considered in this study. Aerodynamic force coefficients were obtained from the surface pressure measurements made over the test model using MPS4264 Simultaneous pressure scanner. 3D printed Ice templates featuring different ice geometries based on Icing Research Tunnel data is utilized. Aerodynamic characteristics of both the clean wing configuration and Ice accreted geometries were analysed over a wide range of angles of attack (α) ranging from 0° to 24° with an increment of 3° for three different Reynolds number in the order of 105. Results show a decrease in aerodynamic characteristics of the iced aerofoil when compared against the baseline clean wing configuration. The key flow field features such as point of separation, reattachment and formation of Laminar Separation Bubble (LSB) for different icing geometries and its influence on the aerodynamic characteristics are addressed. Additionally, attempts were made to understand the influence of Reynolds number on the iced-aerofoil aerodynamics.

• Journal of Ceramic Processing Research
• /
• v.13 no.spc1
• /
• pp.140-144
• /
• 2012

Ga-doped ZnO (GZO) was a limit of application on the photovoltaic devices such as CIGS, CdTe and DSSC requiring high process temperature, because it's electrical resistivity is unstable above 300 ℃ at atmosphere. Therefore, ZTO (zinc tin oxide) was introduced in order to improve permeability and thermal stability of GZO film. The resistivity of GZO (300 nm) single layer increased remarkably from 1.8 × 10-3Ωcm to 5.5 × 10-1Ωcm, when GZO was post-annealed at 400 ℃ in air atmosphere. In the case of the ZTO (150 nm)/GZO (150 nm) double layer, resistivity showed relatively small change from 3.1 × 10-3Ωcm (RT) to 1.2 × 10-2Ωcm (400 ℃), which showed good agreement with change of carrier density. This result means that ZTO upper layer act as a barrier for oxygen at high temperature. Also ZTO (150 nm)/GZO (150 nm) double layer showed lower WVTR compared to GZO (300 nm) single layer. Because ZTO has lower WVTR compared to GZO, ZTO thin film acts as a barrier by preventing oxygen and water molecules to penetrate on top of GZO thin film.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.7
• /
• pp.104-112
• /
• 2019

The material properties of the 3D printing cement composite mortar were evaluated, and the performance range in which printing was possible was calculated using the void ratio in a fresh state as a single index. As a results of the tests, as the water-binder ratio (W/B) increased, the mortar flow value increased and the density and strength decreased. As the sand-binder ratio (SS/B) increased, the mortar flow value decreased. However, strength and density increased and decreased up to a certain SS/B. As admixture-binder ratio (Ad/B) increased, mortar flow value, density, and strength decreased. These trends make it difficult to mix-design to meet the target performances of 3D printing mortars, represented by extrudability and buildability. The value of mortar flow increased proportionally with the void ratio, while the density and strength apparently decreased as the void ratio increased. This indicates that void ratio can be utilized as a single index for controlling the material properties in the design of mortar mixtures. It was found that mortar mixture could be printed by a 3D printer when the void ratio was in the range from 0.6 to 0.7. This was verified by printing a mortar which has the void ratio of 0.634. The mortar was produced with the mixture design of W/B 35.0%, SS/B 60.0%, and Ad/B 0.1%. Further research applying diverse admixtures is needed to improve the quality of 3D printing output mortars.

• Journal of the Microelectronics and Packaging Society
• /
• v.26 no.3
• /
• pp.81-88
• /
• 2019

In this study, the effects of graphene oxide (GO) addition on electromigration (EM) lifetime of Sn-3.0Ag-0.5Cu Pb-free solder joint between a ball grid array (BGA) package and printed circuit board (PCB) were investigated. After as-bonded, $(Cu,Ni)_6Sn_5$ intermetallic compound (IMC) was formed at the interface of package side finished with electroplated Ni/Au, while $Cu_6Sn_5$ IMC was formed at the interface of OSP-treated PCB side. Mean time to failure of solder joint without GO solder joint under $130^{\circ}C$ with a current density of $1.0{\times}10^3A/cm^2$ was 189.9 hrs and that with GO was 367.1 hrs. EM open failure was occurred at the interface of PCB side with smaller pad diameter than that of package side due to Cu consumption by electrons flow. Meanwhile, we observed that the added GO was distributed at the interface between $Cu_6Sn_5$ IMC and solder. Therefore, we assumed that EM reliability of solder joint with GO was superior to that of without GO by suppressing the Cu diffusion at current crowding regions.

• Journal of Internet of Things and Convergence
• /
• v.6 no.4
• /
• pp.21-26
• /
• 2020

An autonomous driving system is based on the deep learning system built by big data which are obtained by various IoT sensors. The miniaturization and high performance of the IoT sensors are needed for diverse devices including the autonomous driving system. Specially, the miniaturization of the sensors leads to compel the miniaturization of the fixer structures. In the viewpoint of the miniaturization, metallic structure is a best solution to attach the small IoT sensors to the main body. However, it is hard to manufacture the small metallic structure with a conventional machining process or manufacturing cost greatly increases. As one of solutions for the problems, in this work, metallic FDM (Fused depositon modeling) based on metallic filament was proposed and the FDM process was investigated to fabricate the small metallic structure. Final part was obtained by the post-process that consists of debinding and sintering. In this work, the relationship between infill rate and the density of the part after the post-process was investigated. The investigation of the relationship is based on the fact that the infill rate and the density obtained from the post-processing is not same. It can be said that this work is a fundamental research to obtain the higher density of the printed part.

• Journal of the Korean Society for Precision Engineering
• /
• v.31 no.11
• /
• pp.993-998
• /
• 2014

Silver (Ag) grid patterned PET substrates were manufactured by thermal roll-imprinting methods. We coated highly conductive layer (HCL) as a supply electrode on the Ag grid patterned PET in the three kinds of conditions. One was no-HCL without conductive PEDOT:PSS on the Ag grid patterned PET substrate, another was thin-HCL coated with ~50 nm thickness of conductive PEDOT:PSS on the Ag grid PET, and the other was thick-HCL coated with ~95 nm thickness of conductive PEDOT:PSS. These three HCLs in order showed 73.8%, 71.9%, and 64.7% each in transmittance, while indicating $3.84{\Omega}/{\Box}$, $3.29{\Omega}/{\Box}$, and $2.65{\Omega}/{\Box}$ each in sheet resistance. Fabrication of organic solar cells (OSCs) with HCL Ag grid patterned PET substrates showed high power conversion efficiency (PCE) on the thin-HCL device. The thick-HCL device decreased efficiency due to low open circuit voltage ($V_{OC}$). And the Ag grid pattern device without HCL had the lowest energy efficiency caused by quite low short current density ($J_{SC}$).

• Journal of the Microelectronics and Packaging Society
• /
• v.22 no.4
• /
• pp.37-46
• /
• 2015

In this paper, the heat transfer characteristics of PCB (Printed Circuit Board) with cabon CCL (Copper Claded Layer) were studied through experiments and numerical analysis to compare of PCBs with conventional the FR-4 core and heavy copper cores. For study, samples are producted with HDI (High Density Interconnection) PCB of mobile phone with variations of thickness of core materials and grades of carbon material to evaluate heat transfer characteristics respectively. From this research results, heat transfer characteristics of the carbon core was rather low than heavy copper, but better than FR-4 core. In addition, even though the carbon and heavy copper core contributed on the heat transfer characteristics as their thickness increases, FR-4 cores disturbed heat transfer characteristics as it's thickness increases. Therefore, carbon core is recommendable to improve the heat transfer characteristics of the PCB because heavy copper core has much disadvantages such as increasing of wear of drill, the weight of PCB, and manufacturing cost by additional insulation materials for electrical insulation.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.40 no.3
• /
• pp.194-202
• /
• 2003

To convert printed images into electronic ones automatically, it requires region analysis of document images and character recognition. In these, regional analysis segments document image into detailed regions and classifies thee regions into the types of text, picture, table and so on. But it is difficult to classify the text and the picture exactly, because the size, density and complexity of pixel distribution of some of these are similar. Thu, misclassification in region analysis is the main reason that makes automatic conversion difficult. In this paper, we propose region analysis method that segments document image into text and picture regions. The proposed method solves the referred problems using one dimensional median filter based method in text and picture classification. And the misclassification problems of boldface texts and picture regions like graphs or tables, caused by using median filtering, are solved by using of skin peeling filter and maximal text length. The performance, therefore, is better than previous methods containing commercial softwares.

• Transactions of the Korean hydrogen and new energy society
• /
• v.28 no.1
• /
• pp.63-69
• /
• 2017

In this work, two different platinum (Pt) counter electrodes have been prepared by spin coating a Pt solution and screen printing a Pt paste on fluorine doped tin oxide (FTO) glass substrate followed by sintering at $380^{\circ}C$ for 30 min. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) analyses of the Pt electrodes showed that the spin coated electrode was catalytically more active than the screen printed electrode. The above result agrees well with the surface morphology of the electrodes studied by atomic force microscopy (AFM) and the photovoltaic performance of the dye-sensitized solar cells (DSSCs) fabricated with the Pt electrodes. Moreover, calculation of current density-voltage (j-V) curves according to diode model with the parameters obtained from the experimental j-V curves and the EIS data of the DSSCs provided a quantitative insight about how the catalytic activity of the counter electrodes affected the photovoltaic performance of the cells. Even though the experimental situations involved in this work are trivial, the method of analyses outlined here gives a strong insight about how the catalytic activity of a counter electrode affects the photovoltaic performance of a DSSC. This work, also, demonstrates how the photovoltaic performance of DSSCs can be improved by tuning the performance of counter electrode materials.