• Journal of the Microelectronics and Packaging Society
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• v.20 no.2
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• pp.17-22
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• 2013

We investigated the optimum bonding conditions for thermo-compression bonding of electrodes between flexible printed circuit board(FPCB) and rigid printed circuit board(RPCB) with Sn-58Bi solder as interlayer. In order to figure out the optimum bonding conditions, peel test of FPCB/RPCB joint was conducted. The peel strength was affected by the bonding conditions, such as temperature and time. The fracture energies were calculated through F-x (Force-displacement) curve during peel test and the relationships between bonding conditions and fracture behaviors were investigated. The optimum condition for the thermo-compression bonding with Sn-58Bi solder was found to be temperature of $195^{\circ}C$ and time of 7 s.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2004.11a
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• pp.35-35
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• 2004

• Journal of the Microelectronics and Packaging Society
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• v.10 no.3
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• pp.19-27
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• 2003

Surface finishes of PCB laminates are important in the solder joint reliability of flip chip package because the types and thicknesses of intermetallic compound(IMC), and compositions and hardness of solders are affected by them. In this study, effects of surface finishes of PCB on the low cycle fatigue resistance of Sn-based lead-free solders; Sn-3.5Ag, Sn-3.5Ag-XCu(X=0.75, 1.5), Sn-3.5Ag-XBi(X=2.5, 7.5) and Sn-0.7Cu were investigated for the Cu and Au/Ni surface finish treatments. Displacement controlled room temperature lap shear fatigue tests showed that fatigue resistance of Sn-3.5Ag-XCu(X=0.75, 1.5), Sn-3.5Ag and Sn-0.7Cu alloys were more or less the same each other but much better than that of Bi containing alloys regardless of the surface finish layer used. In general, solder joints on the Au/Ni finish showed better fatigue resistance than those on the Cu finish. Cross-sectional fractography revealed microcracks nucleation inside of the interfacial IMC near the solder mask edge, more frequently on the Cu than the Au/Ni surface finish. Macro cracks followed the solder/IMC interface in the Bi containing alloys, while they propagated in the solder matrix in other alloys. It was ascribed to the Bi segregation at the solder/IMC interface and the solid solution hardening effect of Bi in the $\beta-Sn$ matrix.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.2
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• pp.25-30
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• 2018

Sn-Pb solder has been used in automotive electronics for decades. However, recently, due to the environmental and health concerns, some international environmental organizations such as the end-of-life vehicle (ELV) enacted legislation banning of the Pb usage in automotive electronics. For this reason, many studies to develop and promote Pb-free soldering have been significantly reported. Meanwhile, because of flexibility and lightweight, flexible printed circuit boards (FPCBs) have been increasingly used in automotive electronics for lightweight to improve fuel efficiency and space utilization. Although the properties of lead-free solders for automotive electronics have been widely studied, there is a lack of research on the reliability performance of the lead-free solder joint on FPCB under user conditions. This study reported the properties of solder joints between Pb-free solders such as Sn3.0Ag0.5Cu, Sn0.7Cu and Sn0.5Cu0.01Al (Si), and various FPCBs finished with organic solderability preservative (OSP) and electroless nickel immersion gold (ENIG). To evaluate on joint properties and reliabilities with different solder compositions and surface-finishing materials, pull strength test, thermal shock test, and bending cycle test were performed and analyzed. After the bending cycle test of solder joint on OSP-finishing, the fractures were occurred in solder and the lifetime of Sn3.0Ag0.5Cu solder joint was the longest.

• Journal of Welding and Joining
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• v.19 no.4
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• pp.406-412
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• 2001

This study is focussed on the numerical prediction of the thermal fatigue life of a ${\mu}BGA$(Micro Ball Grid Array) solder joint. Numerical method is used to perform three-dimensional finite element analysis for Sn-37mass%Pb. Sn-3.5mass%Ag solder alloys during the given thermal cycling. 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. In this study, a practical correlation for the prediction of the thermal fatigue life is suggested by using the dimensionless variable $\gamma$. As a result. it could be found that Sn-3.5mass%Ag has longer fatigue life than Sn-37mass%Pb in low cycle fatigue. In addition. the result with ${\gamm}ashow$a good agreement with the FEA results.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.3
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• pp.53-57
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• 2013

Although the lowering of Ag content in Sn-3.0Ag-0.5Cu is known to improve the mechanical shock reliability of the solder joint, it is also known to be detrimental to the solderbility. In this study, the quaternary alloying effect of In and the minor alloying effects of Mn and Pd on the solderability, thermal cycling and mechanical shock reliabilities of the low Ag content Sn-1.2Ag-0.7Cu solder were investigated using board-level BGA packages. The solderability of Sn-1.2Ag-0.7Cu-0.4In was proved to be comparable to that of Sn-3.0Ag-0.5Cu but its thermal cycling reliability was inferior to that of Sn-3.0Ag-0.5Cu. While the 0.03 wt% Pd addition to the Sn-1.2Ag-0.7Cu-0.4In decreased the solderability and reliabilities of solder joint, the 0.1 wt% Mn addition was proved to be beneficial especially for the mechanical shock reliability compared to those of Sn-3.0Ag-0.5Cu and Sn-1.0Ag-0.5Cu compositions. It was considered to be due that the Mn addition decreased the Young's modulus of low Ag content Pb-free solders.

• Journal of Welding and Joining
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• v.31 no.3
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• pp.22-30
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• 2013

Due to ELV banning, automotive electronics cannot use four kinds of heavy metal element (Pb, Hg, Cd, $Cr^{6+}$) from 2016. Therefore, this study was focused on degradation characteristics of Sn-3.0Ag-0.5Cu Lead-free solder joint with OSP and ENIG finsh under various reliability assessment method, as like to thermal shock test and high temeprature/high humidity test with test duration for cabin electronics. Also, we compared bonding strength degradation to other advanced research results of electronic control unit for engine room because of difference service temperature with mount location in automotive. Whisker growth phenomenon and mitigation method which were essentially consideration items for Pb-free car electronics were examined. Conformal coating is a strong candidate for mitigating whisker growth in automotive electronics. Necessary condition to adapt Pb-free in car electronics was shown.

• Proceedings of the KWS Conference
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• 2003.05a
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• pp.187-189
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• 2003

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.216-218
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• 2005

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.2
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• pp.187-192
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• 2011

UBM(Under Bump Metallurgy) is very important for successful realization of Flip-Chip technology. In this study, it is investigated the interfacial reactions between various Sn-Ag solder alloys and Ni-P/Au UBM and Cu plate finish. It is also evaluated the shear strength by using the micro shear-punch test method for Sn-37Pb alloy, binary and ternary alloys of environment-friendly Pb-free solder alloys which are applied in the electronic packages. In terms of interfacial microstructure, the Pb-free solder joints have thicker IMCs than the Sn-Pb solder joints. The thickness of IMC is related to Reflow time. The IMC has been observed to grow with the increase in Reflow time. As a result of the shear test, in case of Max. shear strength, Pb-free solder showed the highest strength value and Sn-37Pb showed the lowest strength value 10 be generally condition of Reflow time.