• Title/Summary/Keyword: Surface Mount

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Mirrors and Optomechanical Structures Design and Analysis for Linear Astigma-tism Free Three Mirror System (LAF-TMS)

  • Park, Woojin;Hammar, Arvid;Lee, Sunwoo;Chang, Seunghyuk;Kim, Sanghyuk;Jeong, Byeongjoon;Kim, Geon Hee;Kim, Daewook;Pak, Soojong
    • The Bulletin of The Korean Astronomical Society
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    • v.43 no.2
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    • pp.55.4-56
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    • 2018
  • Linear Astigmatism Free - Three Mirror System (LAF-TMS) is the linear astigmatism free off-axis wide field telescope with D = 150 mm, F/3.3, and $FOV=5.51^{\circ}{\times}4.13^{\circ}$. We report the design and analysis results of its mirrors and optomechanical structures. Tolerance allowance has been analyzed to the minimum mechanical tolerance of ${\pm}0.05mm$ that is reasonable tolerance for fabrication and optical alignment. The aluminum mirrors are designed with mounting flexure features for the strain-free mounting. From Finite Element Analysis (FEA) results of mounting torque and self-weight, we expect 33 - 80 nm RMS mirror surface deformations. Shims and the L-bracket are mounted between mirrors and the mirror mount for optical alignment. The mirror mount is designed with four light-weighted mechanical parts. It can stably and accurately fix mirrors, and it also suppresses some of stray light.

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STELLAR MAGNETIC ACTIVITY MEASURE BASED ON IUE MG II H+K EMISSION LINES OF MAIN-SEQUENCE G STARS

  • Kim, Dowoon;Choi, Hwajin;Yi, Yu
    • Journal of The Korean Astronomical Society
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    • v.55 no.2
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    • pp.59-66
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    • 2022
  • Stellar magnetic activity is important for formulating the evolution of the star. To represent the stellar magnetic activity, the S index is defined using the Ca II H+K flux measure from the Mount Wilson Observatory. Mg II lines are generated in a manner similar to the formation of Ca II lines, which are more sensitive to weak chromospheric activity. Mg II flux data are available from the International Ultraviolet Explorer (IUE). Thus, the main purpose of this study was to analyze the magnetic activity of stars. We used 343 high-resolution IUE spectra of 14 main-sequence G stars to obtain the Mg II continuum surface flux and Mg II line-core flux around 2,800 Å. We calculated S index using the IUE spectra and compared it with the conventional Mount Wilson S index. We found a color (B - V ) dependent association between the S index and the Mg II emission line-core flux. Furthermore, we attempted to obtain the magnetic activity cycles of these stars based on the new S index. Unfortunately, this was not successful because the IUE observation interval of approximately 17 years is too short to estimate the magnetic activity cycles of G-type stars, whose cycles may be longer than the 11 year mean activity cycle of the sun.

Improved kinematic mount design for bar type reference mirror for profilometric measurement large optical surface

  • Jung, Kil-Jae;Yang, Ho-Soon;Rhee, Hyug-Gyo;Jyun, Byoung-Hyug;Lee, Yun-Woo;Kim, Sug-Whan
    • Bulletin of the Korean Space Science Society
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    • 2010.04a
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    • pp.25.3-25.3
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    • 2010
  • Our previous study used a bar-type reference mirror to measure the relative distance to the target surface. The target measurement accuracy was required to $1{\mu}m$ PV for aspheric optical surface up to 1m in diameter. Earlier system suffers from the reference surface deformation when the measuring part moves. In order to reduce the deformation, measuring part and the reference part separated from each order in the new design. This system utilizes a kinematic support assembly using invar flexure to minimize the reference surface deformation under gravity and vibration. The surface deformation requirement of reference mirror is defined as of $0.2{\mu}m$ under gravity and 40Hz vibration. The finite element results, shows reference mirror deformation of $0.164{\mu}m$. The first resonance mode was computed to analysis 46.05Hz for reference part and 43.44Hz for measuring part. Thesis satisfies the frequency requirement.

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Thermo-Mechanical Reliability of Lead-Free Surface Mount Assemblies for Auto-Mobile Application (무연 솔더가 적용된 자동차 전장부품 접합부의 열적.기계적 신뢰성 평가)

  • Ha, Sang-Su;Kim, Jong-Woong;Chae, Jong-Hyuck;Moon, Won-Chul;Hong, Tae-Hwan;Yoo, Choong-Sik;Moon, Jeong-Hoon;Jung, Seung-Boo
    • Journal of Welding and Joining
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    • v.24 no.6
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    • pp.21-27
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    • 2006
  • This study was focused on the evaluation of the thermo-mechanical board-level reliability of Pb-bearing and Pb-free surface mount assemblies. The composition of Pb-bearing solder was a typical Sn-37Pb and that of Pb-free solder used in this study was a representative Sn-3.0Ag-0.5Cu in mass %. Thermal shock test was chosen for the reliability evaluation of the solder joints. Typical $Cu_6Sn_5$ intermetallic compound (IMC) layer was formed between both solders and Cu lead frame at the as-reflowed state, while a layer of $Cu_3Sn$ was additionally formed between the $Cu_6Sn_5$ and Cu lead frame during the thermal shock testing. Thickness of the IMC layers increased with increasing thermal shock cycles, and this is very similar result with that of isothermal aging study of solder joints. Shear test of the multi layer ceramic capacitor(MLCC) joints was also performed to investigate the degradation of mechanical bonding strength of solder joints during the thermal shock testing. Failure mode of the joints after shear testing revealed that the degradation was mainly due to the excessive growth of the IMC layers during the thermal shock testing.

A Study on Melting Phenomena of Solder Paste (솔더 페이스트의 용융현상 연구)

  • 김문일;안병용;정재필
    • Journal of the Microelectronics and Packaging Society
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    • v.8 no.1
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    • pp.5-11
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    • 2001
  • Melting behavior and bridge phenomenon of solder paste, which is essential for surface mount technology in pachaging, were investigated. Solder paste of Sn-37%Pb was printed on Cu-pattern of PCB, and heated over melting point. Melting behavior of the paste was observed using CCD-camera. In order to modelize the melting and agglomeration phenomena of paste, two solder balls of 0.76 mm diameter were used. As experimental results, the paste start to melt from the margin of the printed shape. The height of the melted paste decreased from 270 $\mu\textrm{m}$ to 200 $\mu\textrm{m}$ firstly, and finally recovered to 250 $\mu\textrm{m}$ During the melting procedure, pores were evolved from the molted paste. Concerning melting model of solder ball, relationship between contact area of solder ball and soldering time was derived as $\chi^2/t=4r \; \gamma/\eta=7.56 m^2$/s at $280^{\circ}C$.

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A Study on the Nonwet Defective Factors of the SMT Process (SMT 공정 Nonwet 불량 인자에 대한 연구)

  • Yun, Chanhyung
    • Journal of the Microelectronics and Packaging Society
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    • v.27 no.3
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    • pp.35-39
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    • 2020
  • Nonwet (Head in Pillow) defect is one of the defects in SMT (surface mount technology) process, the defect is caused by several factors, such as solder paste misalignment, reflow condition, package warpage and package ball size. This paper focused on ① reflow condition ② package ball & solder paste misalignment ③ package ball size for nonwet experiment. The first, on the case of reflow condition, there would be high risk of nonwet defect when the soldering time was increased, but N2 was adopted to reflow process, there could be no or low risk of nonwet defect because of oxidation barrier control. And when the contact depth between Solder ball and solder paste was below 20 ㎛, there could be high risk of nonwet defect. Also smaller package ball would have low risk of nonwet defect.

Research on Increasing the Production Yield Rate by Six Sigma Method : A Case of SMT Process of Main Board

  • Lin, Ching-Kun;Chen, Hsien-Ching;Li, Rong-Kwei;Chen, Ching-Piao;Tsai, Chih-Hung
    • International Journal of Quality Innovation
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    • v.10 no.1
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    • pp.1-23
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    • 2009
  • Face the process yield rate improvements of motherboard, although general enterprises finish deployment goal of each functions by overall quality managements, through quality improvement methods, industry engineering methods, plan-do-check-act (PDCA) methods and other improvement solutions, but it is only can be improved partially and unable to enhance the yield rate of product to the target. It only can takes one step ahead to enhance the process yield rate of motherboard with six sigma ($6{\sigma}$) overall DMAIC process and tactics. This research aimed to use six sigma quality improvement tactics by DMAIC systematic procedure and tactics, and find the key factors that effect to the process yield rate of surface mount technology. It also identified the keys input and process and output index to satisfy customer requirements and internal process index. The results showed that the major effective factors by fishbone and process failure modes and effects analysis (PFMEA). If the index of input and output that can be quantified, the optimum parameter can be found through design of experiment to ensure that the process is stable. If the factor of input and output that cannot be quantified, we found out the effective countermeasure by Mind_Mapping, make sure whole processes can be controlled stably, to reach the high product quality and enhance the customer satisfaction.

Efficient Mechanism for QFN Solder Defect Detection (QFN 납땜 불량 검출을 위한 효율적인 검사 기법)

  • Kim, Ho-Joong;Cho, Tai-Hoon
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2016.05a
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    • pp.367-370
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    • 2016
  • QFN(Quad Flat No-leads package) is one of the SMD(Surface Mount Device). Since there is no lead in QFN, there are many defects on solder. Therefore, we propose an efficient mechanism for QFN solder defect detection at this paper. For this, we employ Convolutional Neural Network(CNN) of the Machine Learning algorithm. QFN solder's color multi-layer images are used to train CNN. Since these images are 3-channel color images, they have a problem with applying to CNN. To solve this problem, we used each 1-channel grayscale image(Red, Blue, Green) that was separated from 3-channel color images. We were able to detect QFN solder defects by using this CNN. Later, further research is needed to detect other QFN.

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Development of a 3 kW Grid-tied PV Inverter With GaN HEMT Considering Thermal Considerations (GaN HEMT를 적용한 3kW급 계통연계 태양광 인버터의 방열 설계 및 개발)

  • Han, Seok-Gyu;Noh, Yong-Su;Hyon, Byong-Jo;Park, Joon-Sung;Joo, Dongmyoung
    • The Transactions of the Korean Institute of Power Electronics
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    • v.26 no.5
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    • pp.325-333
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    • 2021
  • A 3 kW grid-tied PV inverter with Gallium nitride high-electron mobility transistor (GaN HEMT) for domestic commercialization was developed using boost converter and full-bridge inverter with LCL filter topology. Recently, many GaN HEMTs are manufactured as surface mount packages because of their lower parasitic inductance characteristic than standard TO (transistor outline) packages. A surface mount packaged GaN HEMT releases heat through either top or bottom cooling method. IGOT60R070D1 is selected as a key power semiconductor because it has a top cooling method and fairly low thermal resistances from junction to ambient. Its characteristics allow the design of a 3 kW inverter without forced convection, thereby providing great advantages in terms of easy maintenance and high reliability. 1EDF5673K is selected as a gate driver because its driving current and negative voltage output characteristics are highly optimized for IGOT60R070D1. An LCL filter with passive damping resistor is applied to attenuate the switching frequency harmonics to the grid-tied operation. The designed LCL filter parameters are validated with PSIM simulation. A prototype of 3 kW PV inverter with GaN HEMT is constructed to verify the performance of the power conversion system. It achieved high power density of 614 W/L and peak power efficiency of 99% for the boost converter and inverter.

The Method to Reduce the Driving Time of Gentry (겐트리 구동시간의 단축 방법)

  • Kim, Soon Ho;Kim, Chi Su
    • KIPS Transactions on Software and Data Engineering
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    • v.7 no.11
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    • pp.405-410
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    • 2018
  • When more parts are mounted in the same time in a surface mount equipment, the total output will increase and will improve productivity. In this paper, we propose a method to reduce the gantry drive time from the suction to the mounting of the component to improve the productivity of the surface mount equipment. The method was to find a way to get the maximum velocity in front of the camera during the vision inspection. In this paper, we have developed a stop-motion, fly1-motion, and fly2-motion drive time calculation algorithms for vision inspection and calculated the driving time of 3 methods and compared them. As a result, the fly1-motion method shortened the time by 13% and the fly2-motion method shortened the time by 18% than the stop-motion method.