Cu 에 대한 Sn-3.5Ag 계 땜납의 젖음성 및 계면반응

백대화(Dae Hwa Baek),이경구(Kyung Ku Lee),박효병(Hyo Byeong Park),정명준(Myung Jun Geong),이도재(Doh Jae Lee) 한국주조공학회 1999 한국주조공학회지 Vol.19 No.3

The wettability and interfacial reaction between Sn-3.5Ag solders and Cu-substrate were examined as a function of alloying element (1Pb, 1Sb) and soldering time. Cu/solder joints were subjected to aging treatments for up to 60 days at 150˚C to observe interfacial compounds and changes of microstructure by optical microscopy, SEM and EDS. The addition of 1Pb to the Sn-3.5Ag solder improves the wetting characteristics of the alloy and lowers the melting temperature. The growth rate of the Cu_6Sn_5 layer in the Sn-3.5 Ag solder/Cu was faster than that in the Sn-3.5Ag-1Sb solder/Cu. The activation energy for Cu_6Sn_5 growth was estimated as 31∼35 kJ/mole. (Received January 15, 1999)

Sn-3.5wt.%Ag- 1wt.%Zn 땜납과 Cu 기판간의 미세조직 및 계면반응

백대화(Dae Hwa Baek),서윤종(Youn Jong Seo),이경구(Kyung Ku Lee),이도재(Doh Jae Lee) 한국주조공학회 2002 한국주조공학회지 Vol.22 No.2

N/A This study examined the effects of adding Zn to Sn-3.5Ag solder on the microstructure changes and behavior of interface reaction of the solder joint with Cu substrate. The solder/Cu joints were examined with microscope to observe the characteristics of microstructure changes and interfacial reaction layer with aging treatment for up to 120 days at 150℃. Results of the microstructure changes showed that the microstructures were coarsened with aging treatment, while adding 1%Zn suppresses coarsening microstructures. The Sn-3.5Ag/Cu had a fast growth rate of the reaction layer in comparison with the Sn-3.5Ag-1Zn at the aging temperature of 150℃. Through the SEM/EDS analysis of solder joint, it was proved that intermetallic layer was Cu_6Sn_5 phase and aged specimens showed that intermetallic layer grew in proportion to t^1/2, and the precipitate of Ag_6Sn occur to both inner layer and interface of layer and solder. In case of Zn-containing composite solder, Cu_6Sn_5 phase formed at the side of substrate and Cu-Zn-Sn phase formed at the other side in double layer. It seems that Cu-Zn-Sn phase formed at solder side did a roll of banrier to suppress the growth of the Cu_6Sn_5 layer during the aging treatment.

건강 중심의 도시 계획을 위한 잠재적 지하공간 거주자들의 관점에서 본 인식에 관한 종합적 분석

백대화(Baek, Dae-Hwa),백정엽(Baek, Jeong-yeop),노재창(Noh, Jae-Chang),임리사(Lim, Lisa) 대한건축학회 2023 대한건축학회 학술발표대회 논문집 Vol.43 No.2

Utilizing underground spaces presents a promising solution to the urban challenges faced by many countries. These challenges include congestion and the need for disaster preparedness. Underground spaces inherently offer protection from environmental extremes and serve as potential safe havens from threats, such as natural disaster. However, public perception of underground living remains a significant obstacle. A recent survey highlighted this issue, showing that many people hold negative views about the prospect of residing in underground spaces. To address these concerns, design recommendations for underground facilities have been proposed. To ensure the successful integration of these spaces into urban planning, it is imperative that future research focuses on refining these guidelines, with a particular emphasis on enhancing public perception of underground living.

사례기반 건축물 리모델링 지원용 데이터베이스 시스템

백대화(Dae Hwa Baek),백정엽(Jeong Yeop Baek),장성주(Sung Ju Chang) 대한설비공학회 2022 대한설비공학회 학술발표대회논문집 Vol.2022 No.6

This research aims to develop personalized solutions that could cut construction costs by up to 30 percent and heating and cooling loads in existing buildings by up to 50 percent by making low-carbon, energy-efficient renovations. To reach this goal, research and development of the foundation for the optimal model for low-carbon energy efficiency in existing buildings with detailed technology, development of low-carbon energy efficiency technology packages for existing buildings, customization of low-carbon energy efficiency technology, and distribution of the optimal model for low-carbon energy efficiency based on demand are all required as making a database system that collects and sorts cases of remodeling in Korea and other countries. This will help them figure out the best way to make existing buildings use less energy and produce less carbon. Based on this, guidelines are made for future building remodeling to make the best remodeling plan. This study collected domestic and foreign remodeling design/construction cases, made a remodeling case database, made a web-based interface for the remodeling case database, and tested the applicability of remodeling targets on a test-bed.

가변형 차양장치의 적용실태에 관한 탐색 - 해외 건축물의 사례분석을 중심으로 -

백대화(Baek, Dae-Hwa),장성주(Chang, Seong-Ju) 대한건축학회 2021 대한건축학회 학술발표대회 논문집 Vol.41 No.1

This study is to analyze three overseas cases representing notable technological combinations and practical designs of kinetic solar shading devices which are aesthetically compelling but show insufficient performance in terms of building energy reduction and occupants’ visual comfort. Each selected shading device is virtually combined with a campus building located in Daejeon to simulated and analyze its strengths and weaknesses. As a consequence, this exploration on kinetic shading devices could provide a useful insight for optimizing the design of solar shading device targeting effective sunshade and solar control in the future.

PCA 적용 데이터 차원 변화에 따른 LSTM 기반 건물 전력 소비량 예측 - 대전 캠퍼스 건물을 중심으로 -

백정엽(Baek, Jeong-Yeop),민세웅(Min, Sae-Woong),백대화(Baek, Dae-Hwa),장성주(Chang, Seong-Ju) 대한건축학회 2021 대한건축학회논문집 Vol.37 No.9

Building energy demand currently accounts for 30% of the total energy consumption, which has a great influence on the planning and operation of the energy market managed by energy suppliers. Furthermore, its importance has increased significantly with the advent of smart grid. Variables affecting building energy consumption include identified various environmental conditions that cast sophisticated effect on the energy performance of the buildings. However, due to a large number of potentially associated environmental variables, it is needed to extract embedded features so as to improve building energy prediction capability through adopting Principle Component Analysis which could reduce input data dimension. The primary objective of this study is to propose a high-precision building energy demand prediction model by reducing the dimensionality through PCA. Machine learning is implemented by using LSTM model, and prediction accuracy and performance are verified through R², RMSE, MAE, as well as computation time. The improvement ratio showed 14.93% increase when dimension-reduced dataset and normalized raw data were combined in comparison with the predicted case tested by using only normalized raw data. This study could support optimum building energy operation planning and design by promoting the creation and implementation of energy-efficient smart grid systems in the future.

Bi 를 첨가한 Sn-3.5wt.%Ag 땜납의 미세조직 및 기계적 성질

이경구(Kyung Ku Lee),백대화(Dae Hwa Baek),서윤종(Youn Jong Seo),이도재(Doh Jae Lee) 한국주조공학회 2001 한국주조공학회지 Vol.21 No.4

N/A Microstructure and mechanical properties of Sn-3.lwt% Ag-6.9wt% Bi system solders on Cu-substrate were studied. The Sn-3.1wt% Ag-6.9wt% Bi alloy was designed by phase diagram and chemical properties and was prepared by melting in argon atmosphere. The mechanical properties of solder/Cu joints were examined by shear strength test, and also creep test. The microstructure of Sn-3.1wt% Ag-6.9wt% Bi alloy consists of Bi-rich phase and Ag₃Sn precipitate in β-Sn matrix phase. The shear strength of the joint was decreased with aging treatment. Crack path under shear test was through the solder. Similar crack path change mode was observed at the creep test of solder/Cu joint. The creep behavior of Sn-3.1wt% Ag-6.9wt% Bi alloy represented the inverse primary creep behavior at all test condition. It is suggested that the inverse primary creep behavior is induced from Bi solute atoms in Sn-matrix. The creep resistance of Sn-3.1 Ag-6.9Bi alloy is better than that of Sn-3.5wt% Ag alloy at all test conditions.

Hf 가 첨가된 Fe-30at.%A1-5at.%Cr 합금의 미세조직 및 열간압연가공 특성

윤계림(Kye Lim Yoon),이도재(Doh Jae Lee),백대화(Dae Hwa Baek),이경구(Kyung Ku Lee) 한국주조공학회 2001 한국주조공학회지 Vol.21 No.6

N/A This study was carried out to examine the effects of adding 0.3at.%Hf in Fe-30at.%Al-5at.%Cr alloy on the variation of microstructures and hot workability. The effect of hot rolling on mechanical properties was estimated by measuring the elongation and tensile strength after rolling at 800 and 1000 respectively. Microstructure of Fe-30at.%Al-5at.%Cr alloy was consisted of large equiaxed grains and it was changed to quasi-equiaxed or columnar structures by adding 0.3at.%Hf to Fe-30at.%Al-5at.%Cr alloy. Every specimens showed a decreased tensile strength after hot rolling compared to that of before rolling. The elongation was increased by hot rolling. Remarkable changes in elongation by hot rollong was observed such as from 1.4% to 4.5% elongation at the specimen of 0.3at.%Hf added to Fe-30at.%Al-5at.%Cr. Fe-30at.%Al-5at.%Cr alloy showed typical cleavage fracture on tensile failure and hot rolling has negligible effects on fracture mode in this alloy. However at the alloy containing Hf fracturemode was changed by hot rolling from intergranular to mixed intergranular and transgranular fracture mode.

In , Bi 가 첨가된 Sn-9wt.%Zn/Cu 접합부의 납땜성 및 기계적 성질

이도재,이경구,백대화 한국주조공학회 2000 한국주조공학회지 Vol.20 No.2

Interfacial reaction and mechanical properties between Sn-Zn-X ternary alloys(X : 3wt.%In, 4wt.%Bi) and Cu-substrate were studied. Cu/solder joints were subjected to aging treatments for up to 50days to see interfacial reaction at 100℃ and then were examined changes of microstructure and interfacial compound by optical microscopy, SEM and EDS. Cu/solder joints were aged to 30days and then loaded to failure at cross head speed of 0.3㎜ min^(-1) to measure tensile strength. According to the results of the solderability test, additions of In and Bi in the Sn-9wt.%Zn solder improve the wetting characteristics of the alloy and lower the melting temperature. Through the EDS and XRD analysis of Cu/Sn-9wt.%Zn solder joint, it was concluded that the intermetallic compound was the γ-Cu_5Zn_8 phase. Cu-Zn intermetallics at Cu/solder interfaces played an important role in both the microstructure evolution and failure of solder joints. Cu/solder joint strength was decreased by aging treatment, and those phenomenon was closely related to the thickening of intermetallic layer at Cu/solder joints.