통합 검색 | Korea Science

장재원;방정환;유세훈;김목순;김준기
- 한국재료학회지
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- 제21권12호
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- pp.650-654
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- 2011
In this paper, the effects of conventional and newly developed elastomer modified underfill materials on the mechanical shock reliability of BGA board assembly were studied for application in mobile electronics. The mechanical shock reliability was evaluated through a three point dynamic bending test proposed by Motorola. The thermal properties of the underfills were measured by a DSC machine. Through the DSC results, the curing condition of the underfills was selected. Two types of underfills showed similar curing behavior. During the dynamic bending reliability test, the strain of the PCB was step increased from 0.2% to 1.5% until the failure circuit was detected at a 50 kHz sampling rate. The dynamic bending reliability of BGA board assembly using elastomer modified underfill was found to be superior to that of conventional underfill. From mechanical and microstructure analyses, the disturbance of crack propagation by the presence of submicron elastomer particles was considered to be mainly responsible for that result rather than the shear strength or elastic modulus of underfill joint.
https://doi.org/10.3740/MRSK.2011.21.12.650 인용 PDF KSCI

김종도;박현준
- Journal of Welding and Joining
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- 제24권2호
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- pp.71-78
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- 2006
It has been reported that good quality weld beads are not easily obtained during the $CO_2$ CW laser welding of primer coated plate. However, by introducing a small gap clearance in the lap position, the zinc vapor can escape through it and sound weld beads can be acquired. Therefore, this study examines for keyhole behavior by observing the laser-induced plasma and investigates the relation between keyhole behavior and formation of weld defect. Laser-induced plasma has accompanied with the vaporizing pressure of zinc ejecting from keyhole to surface of primer coated plate. This dynamic behavior of plasma was very unstable and this instability was closely related to the unstable motion of keyhole during laser welding. As a result of observing the composition of porosity, much of Zn element was found from inner surface of porosity. But Zn was not found from the dimple structure fractured at the weld metal. By analyzing of vaporizing element in laser welding, a component ratio of Zn was decreased by introducing a small gap clearance. Therefore we can prove that the major cause of porosity is the vaporization of primer in lap position. Mechanism of porosity-formation is that the primer vaporized from the lap position accelerates dynamic behavior of the key hole and the bubble separated from the key hole is trapped in the solidification boundary and romaines as porosity.
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백운봉;윤기봉
- 대한용접접합학회:학술대회논문집
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- 대한용접접합학회 2001년도 춘계학술발표대회 개요집
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- pp.104-107
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- 2001
Creep-fatigue crack growth behavior at the heat affected zone of 1Cr-0.5Mo steel weldment has been experimentally studied. Load hold times of the tests for trapezoidal fatigue wave-shapes were varied among 0, 30, 300 and 3,600 seconds. Time-dependent crack growth rates were characterized by the $C_{t}$ estimated with the equation proposed by the previous finite element analysis work. It was concluded that the $C_{t}$ values calculated from the properties of parent metal were quite comparable to the accurate $C_{t}$ values calculated from both of weld and parent metals.etals.
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