• Journal of the Microelectronics and Packaging Society
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• v.19 no.3
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• pp.31-36
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• 2012

In this study, the complex vibration reliability of Sn-3.5Ag and Sn-0.7Cu having a high melting temperature was investigated. For manufacturing of BGA test samples, Sn-3.5Ag and Sn-0.7Cu balls were joined on BGA chips finished by ENIG and the chips were mounted on PCB finished OSP by using reflow process. For measuring of resistance change during complex vibration test, daisy chain was formed in the test board. From the results of resistance change and shear strength change, the reliability of two solder balls was compared and evaluated. During complex vibration for 120 hours, Sn-0.7Cu solder was more stable than Sn-3.5Ag solder in complex vibration test.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.97-103
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• 2014

Among various lead-free solders, the Sn-58Bi solders have been considered as a highly promising lead-free solders because of its low melting temperature and high tensile strength. However, Sn-58Bi solder has the poor ductility. To enhance the mechanical property of Sn-58Bi solder, epoxy-enhanced Sn-58Bi solders have been studied. This study compared the microstructures and the mechanical properties of Sn-58Bi solder and Sn-58Bi epoxy solder with aging treatment. The solders ball were formed on the printed circuit board (PCB) with organic solderability preservative (OSP) surface finish, and then the joints were aged at 85, 95, 105 and $115^{\circ}C$ for up to 100, 300, 500 and 1000 hours. The shear test was conducted to evaluate the mechanical property of the solder joints. $Cu_6Sn_5$ intermetallic compound (IMC) layer grew with increasing aging time and temperature. The IMC layer for the Sn-58Bi epoxy solder was thicker than that for the Sn-58Bi solder. According to result of shear test, the shear strength of Sn-58Bi epoxy solder was higher than that of Sn-58Bi solder and the shear strength decreased with increasing aging time.

• Journal of Welding and Joining
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• v.33 no.3
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• pp.19-24
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• 2015

Joint properties of electric control unit (ECU) module using Sn-Cu-(X)Al(Si) lead-free solder alloy were investigated for automotive electronics module. In this study, Sn-0.5Cu-0.01Al(Si) and Sn-0.5Cu-0.03Al(Si) (wt.%) lead-free alloys were fabricated as bar type by doped various weight percentages (0.01 and 0.03 wt.%) of Al(Si) alloy to Sn-0.5Cu. After fabrications of lead-free alloys, the ball-type solder alloys with a diameter of 450 um were made by rolling and punching. The melting temperatures of 0.01Al(Si) and 0.03Al(Si) were 230.2 and $230.8^{\circ}C$, respectively. To evaluation of properties of solder joint, test printed circuit board (PCB) finished with organic solderability perseveration (OSP) on Cu pad. The ball-type solders were attached to test PCB with flux and reflowed for formation of solder joint. The maximum temperature of reflow was $260^{\circ}C$ for 50s above melting temperature. And then, we measured spreadability and shear strength of two Al(Si) solder materials compared to Sn-0.7Cu solder material used in industry. And also, microstructures in solder and intermetallic compounds (IMCs) were observed. Moreover, thickness and grain size of $Cu_6Sn_5$ IMC were measured and then compared with Sn-0.7Cu. With increasing the amounts of Al(Si), the $Cu_6Sn_5$ thickness was decreased. These results show the addition of Al(Si) could suppress IMC growth and improve the reliability of solder joint.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.8
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• pp.1931-1939
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• 1993

The wave propagation characteristics of laminated composites subjected to a transverse high-velocity impact of a steel ball is investigated. For this purpose, high-velocity impact experiments were conducted to obtain the strain response histories, and a finite element analysis based on the higher-order shear deformation theory in conjunction with the static contact law is used. Test materials for investigation are glass/epoxy laminated composite materials with $[0^{\circ}/45^{\circ}/0^{\circ}/-45^{\circ}]_{2s}$ and $[90^{\circ}/-45^{\circ}/90^{\circ}-45^{\circ}/90^{\circ}]_{2s}$ stacking sequences. As a result, the strain responses obtained from the experiments represented the wave propagation characteristics in the transversely impact, also the wave propagation velocities obtained from high-velocity impact experiments and wave propagation theory agree well.

• Journal of the Korean Society for Precision Engineering
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• v.7 no.4
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• pp.29-39
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• 1990

The purpose of this research is to analyze the impact behaviors of laminated composite plates subjected to the transverse low-velocity impact by the steel ball. A plate finite element model based on Whitney and Pagano's the first-order shear deformation theory (FSDT) in conjunction with experimental static contact laws is formulated and then compared with the results of the impact experiments. Because the input data and the output data printed at every integration time step are lots of amount, these are interactively poecessed by the developed pre-processor(PREPLOT) and postprecessor(POSTPLOT). All results from these procesors are automatically generated by CALCOMP plotter. Test materials are glass/expoxy composite materials. The specimens are composed of [$0^{\circ} /45^{\circ}/0^{\circ}/-45^{\circ}/0^{\circ}/]2s\ and \[90^{\circ}/45^{\circ}/90^{\circ}/-45^{\circ}/90^{\circ}/$]2s stacking sequences and have $4.5^t{\times}200^w{\times}200^l$(mm) and $4.5^t{\times}300^w{\times}300^l$(mm) dimensions.

• Journal of Welding and Joining
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• v.30 no.5
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• pp.64-69
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• 2012

Sn-Bi eutectic alloy has been widely used as one of the key solder materials for step soldering at low temperature. The Sn-58Bi solder paste containing chloride flux was adopted to compare with that using the chloride-free flux. The paste was applied on the electroless nickel-immersion gold (ENIG) surface finish by stencil printing, and the reflow process was then performed at $170^{\circ}C$ for 10 min. After reflow, the solder joints were aged at $125^{\circ}C$ for 100, 200, 300, 500 and 1000 h in an oven. The interfacial microstructures were obtained by using scanning electron microscopy (SEM), and the composition of intermetallic compounds (IMCs) was analyzed using energy dispersive spectrometer (EDS). Two different IMC layers, consisting of $Ni_3Sn_4$ and relatively very thin Sn-Bi-Ni-Au were formed at the solder/surface finish interface, and their thickness increased with increasing aging time. The wettability of solder joints was investigated by wetting balance test. The mechanical property of each aging solder joint was evaluated by the ball shear test in accordance with JEDEC standard (JESD22-B117A). The results show that the highest shear force was measured when the aging time was 100 h, and the fracture mode changed from ductile fracture to brittle fracture with increasing aging time. On the other hand, the chloride flux in the solder paste did not affect the shear force and fracture mode of the solder joints.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.25.1-25.1
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• 2011

Over the past few decades, metallic nanoparticles (NPs) have been of great interest due to their unique mesoscopic properties which distinguish them from those of bulk metals; such as lowered melting points, greater versatility that allows for more ease of processability, and tunable optical and mechanical properties. Due to these unique properties, potential opportunities are seen for applications that incorporate nanomaterials into optical and electronic devices. Specifically, the development of metallic NPs has gained significant interest within the electronics field and technological community as a whole. In this study, gold (Au) pads for surface finish in electronic package were developed by inkjet printing of Au NPs. The microstructures of inkjet-printed Au film were investigated by various thermal treatment conditions. The film showed the grain growth as well as bonding between NPs. The film became denser with pore elimination when NPs were sintered under gas flows of $N_2$-bubbled through formic acid ($FA/N_2$) and $N_2$, which resulted in improvement of electrical conductance. The resistivity of film was 4.79 ${\mu}{\Omega}$-cm, about twice of bulk value. From organic anlayses of FTIR, Raman spectroscopy, and TGA, the amount of organic residue in the film was 0.43% which meant considerable removal of the solvent or organic capping molecules. The solder ball shear test was adopted for solderability and shear strength value was 820 gf (1 gf=9.81 mN) on average. This shear strength is good enough to substitute the inkjet-printed Au nanoparticulate film for electroplating in electronic package.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.12
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• pp.1856-1863
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• 2004

In the last 50 years, lead-contained solder materials have been the most popular interconnect materials used in the electronics industry. Recently, lead-free solders are about to replace lead-contained solders for preventing environmental pollutions. However, the reliability of lead-free solders is not yet satisfactory. Several researchers reported that lead-contained solders have a good fatigue property. The others published that the lead-free solders have a longer thermal fatigue life. In this paper, the reason for the contradictory results published on the estimation of fatigue life of lead-free solder is investigated. In the present study, fatigue behavior of 63Sn37Pb, and two types of lead-free solder joints were compared using pseudo-power cycling testing method, which provides more realistic load cycling than chamber cycling method does. Pseudo-power cycling test was performed in various temperature ranges to evaluating the shear strain effect. A nonlinear finite element model was used to simulate the thermally induced visco-plastic deformation of solder ball joint in BGA packages. It was found that lead-free solder joints have a good fatigue property in the small temperature range condition. That condition induce small strain amplitude. However in the large temperature range condition, lead-contained solder joints have a longer fatigue life.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.521-524
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• 2008

Effect of prior deformation on the sliding wear of the ultra-fine grained (UFG) ferrite-martensite dual phase (DP) steel was investigated. The UFG DP steel was fabricated by the ECAP and subsequent intercritical annealing. The steel was cold rolled before the wear test, and the effect of the prior deformation on the wear was examined. The wear tests were carried out at various loads against a bearing steel ball. The wear rate of the UFG DP steel that did not experience the prior deformation was higher than that of the coarse-grained (CG) DP steel, because of more severe surface shear deformation. The wear rate of the specimens with prior deformation was much higher than that of the specimen without prior deformation. The deformed CG DP specimen showed higher rate than the deformed UFG DP specimen, and the rate-variation of the CG DP steel was much bigger under the same test condition.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.2
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• pp.41-47
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• 2010

The effect of PCB and BGA pad designs was investigated on the mechanical property of Pb-free solder joints. The mechanical property of solder joint was tested by three different test methods of drop impact tests, bending impact test, and high speed shear test. Two kinds of pad design such as NSMD (Non-Solder Mask Defined) and SMD (Solder Mask Defined) were applied with the OSP finished Pb-free solder (Sn-3.0Ag-0.5Cu, Sn-1.2Ag-0.5Cu). in the drop impact test and bending impact test, the characterized lifetime showed the same tendency, and SMD design showed better mechanical property of solder joint than NSMD regardless of test method, which was due to the different crack path. The fracture crack on SMD pad was propagated along the intermetallic compound (IMC) layer of solder joint, while the fracture crack on NSMD pad propagated through upper edge of land which shields pattern. In the high speed shear test, pad lift occurred on the solder joint of NSMD. SMD/SMD combination of pad design consequently illustrated the best mechanical property of BGA/PCB solder joint, followed by SMD/NSMD, NSMD/SMD, and NSMD/NSMD.