• Tribology and Lubricants
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• 제11권5호
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• pp.162-171
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• 1995

The application of reciprocating engine crankshaft bearings is of particular importance and interest among the plain bearing, not only because the sheer volume of intemal combustion engines now produced, but because the severe operating conditions they are subjected to. Demands for better performances of crankshaft bearings have provide an important impetus in the development of bearings and bearing materials. As engine design progresses toward higher outpt and higher efficiency, crankshaft bearings must perform under more seveve operating conditions. Higher load, temperature, and speed as well as lower viscosity oil are applied to the bearing sysem, resulting in a smaller minimum oil film thickness. This means more solid-solid contact between the shaft and bearing, and the bearing is exposed to more danger of seizure. Some engines may experience bearing seizure problems. However, understanding about the seizure behavior and mechanism is far from being enough. Seizure resistance of a bearing-shaft system will be affected by the properties of the shaft and bearing, especially their materials and surface texture. Commonly used engine bearing materials include Al-Pb-Si, Al-Sn-Si, Al-Sn, and Cu-Pb with Pb-Sn-Cu overlay. These materials have very different properties. They showed different behaviors dering seizure tests and seizure may occur with different mechanism for different bearing material. Shaft materials also affect the seizure resistance of the system. Surface texture of the bearing and shaft have apparent effects on the lubrication and solid-solid contact pattern, and therefore will affect the seizure behavior of the system. Bearings and shafts which are made of different materials and have different surface textures have been tested and analyzed. Their effects on seizure resistance are discussed and possible seizure mechanisms for different beatings are presented in this paper.

• Journal of Welding and Joining
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• 제19권3호
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• pp.311-316
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• 2001

This paper presents that the affecting factors to the solderability and initial reliability. It is the factor that the coefficient of thermal expansion between package and PCB(Printed Circuit Board), the quantity of solder paste and reflow condition, and Au thickness of the solder ball pad on polyimide tape. As the reflow soldering condition for 48 ${\mu}BGA$ is changed, it is estimated that the quantity of Au diffusion at eutectic Sn-Pb solder surface and initial bonding strength of eutectic Sn-Pb solder and lead free solder. It is the result that quantitative measurement of Au diffusion quantity is difficult, but the shear strength of eutectic Sn-Pb solder joint is 842 mN at first reflow and increases 879 mN at third reflow. The major failure mode in solder is judged solder fracture. So, Au diffusion quantity is more affected by reflow temperature than by the reflow times.

• 한국주조공학회지
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• 제17권3호
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• pp.252-257
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• 1997

The 8 mm dia: Sn-38%Pb eutectic alloy rods were produced by use of the horizontal continuous casting process with the heated mold and chill cast process. The cast rods were rolled into 2.0${\sim}$0.5 mm thick plates and structural and mechanical properties were examined. The results revealed that the plates produced by the continuous casting process with the heated mold show much higher superplasticity at ambient temperature (1550% elongation at 0.5mm thick plate and 0.5mm/min strain rate) than the plates procuced by chill cast process (630% elongation). Such a high superplasticity of the continuous cast plates is due to the high-quality plates free from any inside and surface defects with fine and uniform distribution of eutectic phases.

• 보존과학연구
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• 통권6호
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• pp.121-196
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• 1985

Atomic absorption spectrophotometer was used for analyzing each 10elements(Cu, Pb, Sn, Zn, Sb, Fe, Ni, Ag, Co and Mn)on 64 Chinese coinsre covered from Shinan seabed sunken ship. The results show that Cu, Pb and Sn were found to be a major elements consisting of coins and its composition ratio was 6 to 2 to 1.The composition of trace elements on coins was classified 3 levels : Sb, Fe and Zn(0.02%-2.2%), Ag, Ni, and Co(50 ppm-5500 ppm) and Mn(Trace). Theam ount of major elements, Cu and Sn were decreased while increased in Pbby the passage of ages (10th - 13th century) in China. There seems to be no systematic compositional change in major elements but content in trace elements was confirmed to increase with age.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.19-21
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• 2005

The ball shea. tests for ball grid array (BGA) and flip chip packages were carried out with different displacement rates to find out the optimum condition of the displacement rate for this test. The BGA packages consisted of two different kinds of solder balls (eutectic Sn-37wt.%Pb and Sn-3.5wt.%Ag) and electroplated Au/Ni/Cu substrate, whereas the flip chip package consisted of electroplated Sn-37Pb solder and Cu UBM. The packages were reflowed up to 10 times, or aged at 443 K up to 21 days. The variation of the displacement rate resulted in the variations of the shear properties such as shear force, displacement rate at break, fracture mode and strain rate sensitivity. The increase in the displacement rate led to the increase of the shear force and brittleness of solder joints.

• 보존과학연구
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• 통권8호
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• pp.1-12
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• 1987

Fifty ancient Korean coins originated in Choson dynasty have been determined for 9 elements such as Sn, Fe, As, Ag, Co, Sb, Ir, Ru and Ni by instrumental neutron activation analysis and for 3 elements such as Cu, Pb, and Zn by atomicalsorption spectrometry. Bronze coins originated in early days of the dynasty contain as major constituents Cu, Pb and Sn approximately in the ratio 90 : 4 : 3, where as, those in latter days contain in the ratio 7 : 2 : 0. Brass coins which had begun in 17century contain as major constituents Cu, Zn and Pb approximately in the ratio 7 : 1: 1. The multivariate date have been analyzed for the relation among elemental contents through the variance-covariance matrix. The data have been fur theranalyzed by a principal component mapping method. As the results training set of 8class have been chosen, based on the spread of sample points in an eigenvector plotand archaeolgical data such as age and the office of minting.

• Transactions on Electrical and Electronic Materials
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• 제16권1호
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• pp.20-24
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• 2015

We studied the relationship between the surface smoothness of the internal Cu ribbon and the morphology of the Sn-Pb plating layer for solar cell modules. A bumpy surface was observed on the surface of the solar ribbon, which caused irregular reflection of light. Large, Pb-rich, primary ${\alpha}$-phases were found below the convex surface of the solar ribbon, passing from the surface of the internal Cu ribbon to the surface of the plating layer. The primary ${\alpha}$-phases heterogeneously nucleated on the convex surface of the Cu ribbon, and then largely grew to the convex surface of the plating layer. The restriction of the primary ${\alpha}$-phase's formation was enabled by enhancing the smoothness of the Cu ribbon's surface; it was also possible to increase the adhesive strength and decrease contact resistance. We confirmed that the solar ribbon's surface smoothness depends on the internal Cu ribbon's surface smoothness.

• Transactions on Electrical and Electronic Materials
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• 제11권4호
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• pp.182-185
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• 2010

$Pb_{0.99}[(Zr_{0.6}Sn_{0.4})_{0.9}Ti_{0.1}]_{0.98}Nb_{0.02}O_3$ (PNZST) thin films were deposited by radio frequency magnetron sputtering on a $(La_{0.5}Sr_{0.5})CoO_3$ (LSCO)/Pt/Ti/$SiO_2$/Si substrate using a PNZST target with an excess PbO of 10 mole%. The thin films deposited at the substrate temperature of $500^{\circ}C$ crystallized to a perovskite phase after rapid thermal annealing (RTA). The thin films, which annealed at $650^{\circ}C$ for 10 seconds in air, exhibited good crystal structures and ferroelectric properties. The remanent polarization and coercive field of the fabricated PNZST capacitor were approximately $20uC/cm^2$ and 50 kV/cm, respectively. The reduction of the polarization after $2.2\;{\times}\;10^9$ switching cycles was less than 10%.

• Journal of Mechanical Science and Technology
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• 제16권7호
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• pp.919-926
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• 2002

In this study, the numerical prediction of the thermal fatigue lie? of a $\mu$BGA (Micro Ball Grid Array) solder joint was focused. Numerical method was performed using the three-dimensional finite element analysis for various solder alloys such as Sn-37%Pb, Sn-3.5%Ag, Sn-3.5%Ag-0.7%Cu and Sn-3.5%Ag-3%In-0.5%Bi during a given thermal cycling. Strain values obtained by the result of mechanical fatigue tests for solder alloys, were used to predict the solder joint fatigue life using the Coffin-Manson equation. The numerical results showed that Sn-3.5%Ag with the 50-degree ball shape geometry had the longest thermal fatigue life in low cycle fatigue. A practical correlation for the prediction of the thermal fatigue life was also suggested by using the dimensionless variable γ. Additionally Sn-3.5Ag-0.75Cu and Sn-2.0Ag-0.5Cu-2.0Bi were applied to 6$\times$8$\mu$BGA obtained from the 63Sn-37Pb Solder. This 6$\times$8$\mu$BGA were tested at different aging conditions at 130$\^{C}$, 150$\^{C}$, 170$\^{C}$ for 300, 600 and 900 hours. Thickness of the intermetallic compound layer was measured thor each condition and the activation energy thor their growth was computed. The fracture surfaces were analyzed using SEM (Scanning Electron Microscope) with EDS ( Energy Dispersive Spectroscopy).

• 마이크로전자및패키징학회지
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• 제11권1호
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• pp.1-6
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• 2004

자동차 전장품의 시험환경 조건이 엄격해짐에 따라, 전장품 개발 기술자들은 이에 부합하는 성능, 신뢰성, 비용 등을 고려한 보다 효과적인 제품 설계를 위해 노력하고 있다. 본 논문에서는 ECM 알루미나 기판의 플라즈마 세척 영향과 리플로우 후 Sn-37wt%Pb 솔더와 패드 접합부 계면에서 형성되는 금속간 화합물을 관찰하였다. 기판의 플라즈마 세척은 계면 접착력을 저해하였던 C에 의한 유기 잔류물 층이 제거되어 계면 접착력을 향상시키는 효과가 있다. 또한 AFM 분석 결과 도체 패드의 표면 거칠기는 304 nm에서 330 m로 증가하였다. 리플로우 과정에서 솔더와 TiWN/Cu 패드 계면에서 형성된 $Cu_6/Sn_5$는 리플로우 횟수가 증가할 수록 결정립의 크기도 조대화되었다. 솔더와 Ag-Pd 도체패드 계면에서는 세포질 형태의 $Ag_3Sn$화합물이 관찰되었다. $Ag_3Sn$은 지름이 약 0.1∼0.6 $\mu\textrm{m}$이며, 솔더 내부에서는 침상 모양도 관찰되었다.