• Korean Journal of Metals and Materials
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• v.47 no.8
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• pp.500-507
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• 2009

Pb-free solder has recently been used in electronics in efforts to meet environmental regulations, and a number of Pb-free solder alloy choices beyond the near-eutectic SnAgCu solder are now available. With increased demand for thin and portable electronics, the high cost of alloys containing significant amounts of silver and their poor mechanical shock performance have spurred the development of low Ag SnAgCu solder, which provides improved mechanical performance at a reasonable cost. Although low Ag SnAgCu solder exhibits significantly higher fracture resistance under high-strain rates, little thermal fatigue data exist for this solder. Therefore, it is necessary to investigate thermal fatigue reliability of low Ag SnAgCu solder under variation of thermal stress in order to allow its implementation in electronic products with high reliability requirements. In this study, the reliability of Sn0.3Ag0.7Cu(SAC0307), a low Ag solder alloy, is discussed and compared with that of Sn3Ag0.5Cu(SAC305). Three sample types and six samples size are evaluated. Mechanical properties and microstructure of the solder joint are investigated under thermal shock cycles. It was observed that the mechanical strength of SAC0307 dropped slightly with thermal cycling relative to that of SAC305. This reveals that the failure mode of SAC0307 is different from that SAC305 under this critical condition.

• Journal of the Korean institute of surface engineering
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• v.39 no.6
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• pp.302-311
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• 2006

Nowadays the open-type lead-acid battery for vehicle use is being replaced with the sealed-type because it needs no maintenance and has a longer cycle life. Thus researches on this battery are being conducted very actively by many advanced battery companies. There is, however, a serious problem with the maintenance free(MF) battery that its cathode electrode has a limited cycle life due to a corrosion of grid. In this study, it was aimed to improve a corrosion resistance of the cathode grid which is commonly made of Pb-Ca alloy for a mechanical strength. For this purpose, various amounts of alloying elements such as Sn, Ag and Ba were added singly or together to the Pb-Ca alloys and investigated their corrosion behaviors. Batteries fabricated by using these alloys as cathode grids were subjected to life cycle test and their corrosion layers appeared at the interface between the grids and the active materials were carefully observed in order to clarify effects of alloying elements.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.3 s.40
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• pp.1-8
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• 2006

Higher density integration and adoption of new materials in advanced electronic package systems result in severe electrochemical reliability issues in microelectronic packaging due to higher electric field under high temperature and humidity conditions. Under these harsh conditions, metal interconnects respond to applied voltages by electrochemical ionization and conductive filament formation, which leads to short-circuit failure of the electronic package. In this work, in-situ water drop test and evaluation of corrosion characteristics for SnPb solder alloys in D.I. water and NaCl solutions were carried out to understand the fundamental electrochemical migration characteristics and to correlate each other. It was revealed that electrochemical migration behavior of SnPb solder alloys was closely related to the corrosion characteristics, and Pb was primarily ionized in both D.I. water and $Cl^{-}$ solutions. The quality of passive film formed at film surface seems to be critical not only for corrosion resistance but also for ECM resistance of solder alloys.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.3 no.2
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• pp.110-114
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• 2002

The master pattern manufacturing process is one of the most important processes in jewelry industry because the process takes 20% of total jewelry manufacturing costs. The previous jewelry manufacturing process has many steps of "rough design${\leftrightarro}$ detailed drawing${\leftrightarro}$ wax pattern manufacturing ${\leftrightarro}$ lime soda flask mold manufacturing ${\leftrightarro}$ silver master pattern manufacturing ${\leftrightarro}$ mass production of wax pattern ${\leftrightarro}$ investment casting process ${\leftrightarro}$ final jewelry product." A novel process that reduces processing steps by using a rapid prototyping system (RP) has been suggested. The process is "3D CAD design ${\leftrightarro}$ DuraForm mold manufacturing by RP ${\leftrightarro}$ manufacturing master pattern by low melting alloy ${\leftrightarro}$ mass production of wax pattern ${\leftrightarro}$ investment casting process${\leftrightarro}$ final jewelry product." Molds are made with DuraForm powder, of which melting temperature is 19$0^{\circ}C$, by a selective laster sintering type RP. An alloy of Pb-Sn-Bi-Cd, of which melting temperature is $70^{\circ}C$, is casted in the DuraForm molds. Spheres and rings of diameter 20 mm are made by this process. The dimension deformation rate is less than 2%, and the post processing of the castings is convenient. The casting made by the suggested process can be used as a master pattern of jewelry products.of jewelry products.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.1
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• pp.1-7
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• 2010

Interfacial reaction characteristics of a Bi-10Cu-20Sb-0.3Ni Pb-free alloy on Cu pad was investigated by reflow soldering at $430^{\circ}C$. The thickness of interfacial reaction layers with respect to the soldering time was also measured. After the reflow soldering, it was observed that a $(Cu,Ni)_2Sb$, a $Cu_4Sb$ intermetallic layer, and a haze layer, which is consisted of Bi and $Cu_4Sb$ phases, were successively formed at the Bi-10Cu-20Sb-0.3Ni/Cu interface. The total thickness of the reaction layers was found to be linearly increased with increasing of the reflow soldering time up to 120 s. As the added Ni element did not participate in the formation of the thickest $Cu_4Sb$ interfacial layer, suppression of the interfacial growth was not observed.

• Journal of Conservation Science
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• v.33 no.3
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• pp.167-179
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• 2017

In this study, Sangpyeontongbo excavated at Bigyeongdo, Seosan, were investigated to determine the components of the corrosion products that were formed while they were buried underwater in an anaerobic environment. The causes of corrosion product formation were also determined. Microstructure observation, element mapping, principle component analysis for each year, and the detection of corrosion products were carried out. Results indicate that the concretions of corrosion products on the surface are needle-, hexahedral-, and octahedral-shaped; Pb, Cu, and S were among the elements detected. The Cu-S layer was clearly verified using element mapping. An analysis of major elements for each layer showed that Cu, S, and Pb were present and that most Zn was eliminated. The corrosion products detected were $PbCO_3$ (concretion) and $Cu_{1.96}S$ (metal). Accordingly, the anaerobic corrosion properties of Sangpyeongtongbo are summarized as follows: dezincification, copper sulfide, and lead compound.

• Journal of the Korean institute of surface engineering
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• v.15 no.4
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• pp.192-207
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• 1982

A study has been made of the interaction parameters of Zn other elements in dilute solutesd solution of molten cadmium alloys over the temperature range of 450 to 570$^{\circ}C$. The experi-mental measurementss were made in a touch instant cell using a fusedd Licl-KCl electrolyte. The activity of zinc in binary and ternary solutions sexhibiteds a strong positive deviation from Raoult's law. The addition of silver, indium or lead increased the activity of zinc whereas addition of copper, bismuth or tin decreased the zinc activity slightly. The results for all the metallic solutions showed a linear dependence of reciprocal of ab-solute temperature over the experimental range. The interaction parameters obtained are as follows.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.84-87
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• 2003

Since Pb-free solder alloys have been used extensively in microelectronic packaging industry, the interaction between UBM (Under Bump Metallurgy) and solder is a critical issue because IMC (Intermetallic Compound) at the interface is critical for the adhesion of mechanical and the electrical contact for flip chip bonding. IMC growth must be fast during the reflow process to form stable IMC. Too fast IMC growth, however, is undesirable because it causes the dewetting of UBM and the unstable mechanical stability of thick IMC. UP to now. Ni and Cu are the most popular UBMs because electroplating is lower cost process than thin film deposition in vacuum for Al/Ni(V)/Cu or phased Cr-Cu. The consumption rate and the growth rate of IMC on Ni are lower than those of Cu. In contrast, the wetting of solder bumps on Cu is better than Ni. In addition, the residual stress of Cu is lower than that of Ni. Therefore, the alloy of Cu and Ni could be used as optimum UBM with both advantages of Ni and Cu. In this paper, the interfacial reactions of Sn-3.5Ag-0.7Cu solder on Ni-xCu alloy UBMs were investigated. The UBMs of Ni-Cu alloy were made on Si wafer. Thin Cr film and Cu film were used as adhesion layer and electroplating seed layer, respectively. And then, the solderable layer, Ni-Cu alloy, was deposited on the seed layer by electroplating. The UBM consumption rate and intermetallic growth on Ni-Cu alloy were studied as a function of time and Cu contents. And the IMCs between solder and UBM were analyzed with SEM, EDS, and TEM.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.1
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• pp.137-143
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• 2008

Thermal fatigue life prediction for solder joints becomes the most critical issue in present microelectronic packaging industry. And lead-free solder is quickly becoming a reality in electronic manufacturing fields. This trend requires life prediction models for new solder alloy systems. This paper describes the life prediction models for SnAgCu and SnPb solder joints, based upon non-linear finite element analysis (FEA). In case of analyses of the SnAgCu solder joints, two kinds of shapes are used. As a result, it is found that the SnAgCu solder has longer fatigue life than the SnPb solder in temperature cycling analyses.

• International Journal of Precision Engineering and Manufacturing
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• v.2 no.4
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• pp.23-29
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• 2001

The compression behavior of semi-solid materials is studied from a viewpoint of yield criteria and analysis methods. To describe the behavior of materials in semi-solid state, several theories have been proposed by extending the concept of plasticity of porous compressible materials. In the present work, the upper-bound method and the finite element method are used to model the simple compression process using yield criteria of Kuhn and Doraivelu. Segregation between solid and liquid which cause defect of product is analysed for Sn-15%Pb and A356 alloys during deformation in semi-solid state. The comparison of analyses is made according to yield criteria and analysis methods. In addition, the analysis result for semi-solid dendritic Sn-15%Pb alloy is compared with the experimental result of Charreyron et al..