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명노훈(No-Hoon Myoung),김윤재(Yun-Jae Kim),박보규(Bo-Gyu Park),박치용(Chi-Yong Park) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
Analytical limit load solutions are available for straight pipes with rectangular and circular locally wallthinning, subject to internal pressure and global bending. Such solutions are based on equilibrium stress fields, and thus are lower bounds. Noting that accurate limit load solutions are essential for residual strength and life estimates, detailed finite element (FE) limit analysis is performed for straight pipes with locally wall-thinning, subject to internal pressure and global bending. Practically interesting ranges of pipe and defect geometries are considered. Based on the FE results, losed-form approximations of limit loads are proposed. Finally implication of the developed limit load solutions to defect assessment of locally wall-thinned pipes is discussed.his paper provides detailed plastic limit load solutions for wall thinning pipe under global bendig and inner pressure.
Ball Grid Array 63Sn-37Pb Solder joint 의 건전성 평가
명노훈(No-Hoon Myoung),이억섭(Ouk Sub Lee),김동혁(Dong-Hyeok Kim) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월
Generally, component and FR-4 board are connected by solder joint. Because material properties of components and FR-4 board are different, component and FR-4 board show different coefficients of thermal expansion (CTE) and thus strains in component and board are different when they are heated. That is, the differences in CTE of component and FR-4 board cause the dissimilarity in shear strain and BGA solder joint’s failure. The first order Taylor series expansion of the limit state function incorporating with thermal fatigue models is used in order to estimate the failure probability of solder joints under heated condition. A model based on plastic-strain rate such as the Coffin-Manson Fatigue Model is utilized in this study. The effects of random variables such as frequency, maximum temperature, and temperature variations on the failure probability of the BGA solder joint are systematically investigated by using a failure probability model with the first order reliability method(FORM).
명노훈(No Hoon Myoung),이억섭(Ouk Sub Lee),김동혁(Dong Hyeok Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.8
The thermal stresses induced by difference in Coefficient of Thermal Expansion between FR-4 board and 63Sn-37Pb solder joint directly affect the reliability of 63Sn-37Pb solder joint. This research, thus, focuses to investigate the change resistance and crack propagation behavior around solder joint by imposing a designed Acceleration Life Test Procedure on solder joint by using a newly manufactured Thermal Impact Experimental Apparatus. The fracture mechanism of the solder joint was found to be highly influenced by thermal stresses. The reliability of solder joint was evaluated by using a weibull distribution.
명노훈(No-Hoon Myoung),이억섭(Ouk-Sub Lee),김동혁(Dong-Hyeok Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
Generally, component and FR-4 board are connected by solder joint. Because material properties of components and FR-4 board are different, component and FR-4 board show different coefficients of thermal expansion (CTE) and thus strains in component and board are different when they are heated. That is, the differences in CTE of component and FR-4 board cause the dissimilarity in shear strain and solder joint’s failure. The first order Taylor series expansion of the limit state function incorporating with Tresca failure criterion is used in order to estimate the failure probability of solder joints under heated condition. Using shear stresses and shear strains appeared on the solder joint, we estimate the failure probability of solder joints with the Tresca failure criterion. The effects of random variables such as CTE, distance of the solder joint from the neutral point(DNP), temperature variation and height of solder on the failure probability of the solder joint are systematically studied by using the failure probability model with first order reliability method(FORM).
이억섭(Ouk Sub Lee),허만재(Man Jae Hur),명노훈(No Hoon Myoung),김동혁(Dong Hyeok Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
The chip and FR-4 board in electronic goods are generally connected by solder joint. In this case, the difference in coefficients of thermal expansion (CTE) in the chip and FR-4 board generates the shear strains in the solder joint and finally makes the solder joint fail when the chip and FR-4 are heated. The magnitude of shear strain and the final failure are influenced by boundary conditions such as the difference of CTE, the height of solder and the distance of the solder joint from the neutral point (DNP). In this paper, the effects of boundary conditions on the failure probability of solder joint are studied by using the failure probability model with the help of the first order reliability method (FORM). Furthermore, the sensitivity of boundary conditions has been estimated by change of Coefficient of Variation (COV).
FORM과 Monte Carlo Simulation을 이용한 솔더조인트의 신뢰성 평가
이억섭(Ouk Sub Lee),허만재(Man Jae Hur),명노훈(No Hoon Myoung),김동혁(Dong Hyeok Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.8
The chip and FR-4 board in electronic goods are generally connected by solder joint. In this case, the difference in coefficients of thermal expansion (CTE) in the chip and FR-4 board generates the shear strains in the solder joint and finally makes the solder joint fail when the chip and FR-4 are heated. The magnitude of shear strain and the final failure are influenced by boundary conditions such as the difference of CTE, the height of solder and the distance of the solder joint from the neutral point (DNP). In this paper, the effects of boundary conditions on the failure probability of solder joint are studied by using the failure probability model with the help of the first order reliability method (FORM) and the Monte Carlo Simulation (MCS).
이억섭(Ouk Sub Lee),허만재(Man Jae Hur),명노훈(No Hoon Myoung),김동혁(Dong Hyeok Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
It is well known that one of the unavoidable trouble factors for the most electronic goods is its on/off switch operation. Most electronic goods are generally known to be suffered by temperature shock due to the switch on/off. When the BGA package is heated by the environmental factors, the failure of solder joint is mainly influenced by the difference in coefficients of thermal expansion (CTE) between the substrate and BGA chips. In this paper, the reliability of lead-free solder used under a boundary condition of many time of changes in temperature is estimated. The BGA daisy-chain specimens consisted of 63Sn-37Pb solder and Sn-Ag-Cu solder balls are packaged onto FR-4 and tested under the accelerated temperature environment. The changes in resistance of terminals of the substrate in the specimens during the thermal impact test of -40℃~125℃ have been measured and the failure mechanism due to the connection damage has been investigated. An analytical aging model is utilized to predict the changes in resistance. Furthermore, the reliability of solder joints has been modeled as a linear fitting of the experimental data by the least-square method.