• Journal of Welding and Joining
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• 제21권3호
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• pp.92-98
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• 2003

This paper describes the numerical prediction of the thermal fatigue life of a $\mu$BGA(Micro Ball Grid Array) solder joint. Finite element analysis(FEA) was employed to simulate thermal cycling loading for solder joint reliability. Strain values, along with the result of mechanical fatigue tests for solder alloys were then used to predict the solder joint fatigue life using the Coffin-Manson equation. The results show that Sn-3.5mass%Ag solder had the longest thermal fatigue life in low cycle fatigue. Also a practical correlation for the prediction of the thermal fatigue life was suggested by using the dimensionless variable ${\gamma}$, which was possible to use several lead free solder alloys for prediction of thermal fatigue life. Furthermore, when the contact angle of the ball and chip has 50 degrees, solder joint has longest fatigue life.

• 한국운동역학회지
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• 제29권4호
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• pp.213-217
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• 2019

Objective: The purpose of this study was to investigate the ratio of carrie's and run's distance in golf running approach using 52° and 48° wedges. Method: 2 women's professional golfers from the LKPGA were given the running approach in the 5 m, 10 m, 15 m respectively. The variables were analyzed through a golf analyzer and actual measurement. Results: If you send 5 m with 52° and 48° wedges, the ball run about 5 m, 10 m respectively, if you carry 10 m with 52° and 48° wedges, the ball run about 10 m, 13 m respectively. And if you carry 15 m with 52° and 48° wedges, the ball run about 13 m, 15 m respectively. Conclusion: Based on the results, if you are confident in distance, if you choose the club properly and if you are confident, if you try to send the correct distance to the hole cup, then you will have a more confident approach, which will lead to better results.

• 한국공작기계학회논문집
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• 제17권4호
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• pp.75-80
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• 2008

This paper presents an atomic force probe for triggering coordinate measuring machines(CMMs). A rigorous comparison is made between touch trigger probe and atomic force probe for CMMs. Typical CMMs(touch trigger probe based CMMs) often lead to some errors associated with object curvature and difference in triggering sensitivity. Their applicability is limited only to hard objects. The aim of this work is to develop a trigger sensor for CMMs using atomic force. In order to show the applicability of atomic force as a trigger sensor, a cylindrical shape is measured with a CMM and an atomic force microscope. Three different touch probe heads with different ball sizes are tested. The experiments show that smaller ball provides better results for curved objects. The experimental results also show that the performance of atomic force as a trigger sensor is about that of the smallest ball probe. In addition, experiments are also performed to measure soft objects. Finally, this paper suggests and verifies a trigger sensor using atomic force for CMMs.

• 대한기계학회논문집A
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• 제22권3호
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• pp.545-553
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• 1998

Recently a new process known as the magnetic fluid grinding has been developed, which can remove material from the surface of ceramic balls by fifty to one hundred times more rapidly than the conventional lapping process. In this study, the ceramic balls with various compositions are made and ground by using the magnetic fluid grinding technique with various machining parameters. In order to make well-round shaped balls by using the magnetic fluid grinding technique, the fundamental research to find out the machining factors has been carried out. Developing an equipment with higher efficiency and reliability in the machining could certainly lead to the higher productivity with excellent quality of ceramic balls.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
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• pp.221-226
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• 1999

It can be acquired the high effective productivity through of high speed, precision of machine tools, and then, machine tools will be got a competitive power. Industrially advanced countries already developed that the high speed feed is 50m/min using the high speed ball screw. Also, a lot of problems have happened the feed and servo drive system. It is necessary to study about the character of positioning accuracy, heat generation and high speed/accuracy control for feed/servo drive system of high speed/accuracy. In this study, we make use of high performance vertical machine center with a ball screw of large-scale-lead. Also, we'll apply the high-speed/accuracy control technology in this part of feedforward control, multi-buffering block size, etc. Using the design of the mechanical element and high-speed precision control, the basic design concept can be established.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.279-284
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• 2000

It can be acquired the high effective productivity through of high speed, precision of machine tools, and then, machine tools will be got a competitive power. Industrially advanced countries already developed that the high speed feed is 60m/min using the high speed ball screw. Also, a lot of problems have happened the feed drive system. It is necessary to study about the character of positioning accuracy, heat generation and high speed control for feed drive system of high speed. in this study, we make use of the feed drive system with a high lead ball screw. We'll develop the feed drive system at the speed of 60m/min. Using the design of the mechanical element and the high speed control, the basic design concept can be established. After manufacturing one-shaft feed drive system and then conducting the performance test, It'll be analyzed properties of the high speed feed drive system.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1277-1282
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• 2008

Recently LCD panels have becom very important components for portable electronics. In the high density interconnection material, ACF's are used to connect the outer lead of the tape automated bonding to the transparent indium tin oxide electrodes of the LCD panel. ACF consists of an adhesive polymer matrix and randomly dispersed conductive balls. In this study, we analyzed Failure Mode / Mechanism of ACF which is identified Conductive ball Corrsion, Delamination, Crack and Polymer Expansion / Swelling. In ALT(Accelerated Life Test), we select primary stress factors as temperature and humidity. As time passes by, an increase of connection resistance was observed. In conclusion, we have found that high temperature / humidity affects the adhesion.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 춘계학술대회 논문집
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• pp.39-44
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• 1999

It can be acquired the high effective productivity through of high speed, precision of machine tools, and then, machine tools will be got a competitive power. Industrially advanced countries already developed that the high speed feed is 60m/min using the high speed ball screw. Also, a lot of problems have happened the feed drive system. It is necessary to study about the character of positioning accuracy, heat generation and high speed control for feed drive system of high speed. In this study, we make use of the feed drive system with a ball screw of large-scale-lead. We'll develop the feed drive system at the speed of 60m/min. Using the design of the mechanical element and the high speed control, the basic design concept can be established. After manufacturing one-shaft feed drive system and conducting the performance test, it'll be analyzed properties of the high speed feed drive system.

• 대한두개안면성형외과학회지
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• 제24권6호
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• pp.288-291
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• 2023

This case report describes our treatment of a persistent periantral abscess in a 35-year-old woman. The abscess developed following a zygoma-reduction surgery, during which a preexisting fungal ball had not been addressed. Our comprehensive treatment approach included functional endoscopic sinus surgery, fungal ball removal, abscess drainage, and debridement. Two weeks postoperatively, the patient's symptoms had resolved. A 6-month postoperative follow-up revealed no signs of recurrence or complications, and the patient reported satisfactory functional and aesthetic results. This case underscores the importance of thorough preoperative evaluations and raises awareness about the potential risks of untreated asymptomatic pathologies, which can potentially progress and lead to further complications.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.155-160
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• 2002

Recently, the development of aerospace and automobile industries has brought new technological challenges, rebated to the growing complexity of products and the new geometry of the models. High speed milling with a 5-Axis milling machine has been widely used fur 3D sculptured surface parts. When turbine blades are machined by a 5-axis milling, their thin and cantilever shape causes vibrations, deflections and twists. Therefore, the surface roughness and the waviness of the workpiece are not good. In this paper, the effects of cutter orientation and the lead/tilt angle used to machine turbine blades with a 5-axis high speed ball end-milling were investigated to improve geometric accuracy and surface integrity. The experiments were performed using a lead/tilt angle of 15$^{\circ}$ to the workpiece with four cutter directions such as horizontal outward, horizontal inward, vertical outward, and vortical inward directions. Workpiece deflection, surface roughness and the machined surface were all measured with various cutter orientations such as cutting directions, and lead/tilt angle. The results show that the best cutting strategy for machining turbine blades with a 5-axis milling is horizontal inward direction with a tilt angle.