• Proceedings of the KWS Conference
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• 2002.10a
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• pp.450-455
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• 2002

Cu-cored Sn-Ag solder balls were fabricated by coating pure Sn and Ag on Cu balls. The melting behavior and the solderability of the BGA joint with the Ni/Au coated Cu pad were investigated and were compared with those of the commercial Sn-Ag and Sn-Ag-Cu balls. DSC analyses clarified the melting of Cu-cored solders to start at a rather low temperature, the eutectic temperature of Sn-Ag-Cu. It was ascribed to the diffusion of Cu and Ag into Sn plating during the heating process. After reflow soldering the microstructures of the solder and of the interfacial layer between the solder and the Cu pad were analyzed with SEM and EPMA. By EDX analysis, formation of a eutectic microstructure composing of $\beta$-Sn, Ag$_3$Sn, ad Cu$_{6}$Sn$_{5}$ phases was confirmed in the solder, and the η'-(Au, Co, Cu, Ni)$_{6}$Sn$_{5}$ reaction layer was found to form at the interface between the solder and the Cu pad. By conducting shear tests, it was found that the BGA joint using Cu-cored solder ball could prevent the degradation of joint strength during aging at 423K because of the slower growth me of η'-(Au, Co, Cu, Ni)$_{6}$Sn$_{5}$ reaction layer formed at the solder, pad interface. Furthermore, Cu-cored multi-component Sn-Ag-Bi balls were fabricated by sequentially coating the binary Sn-Ag and Sn-Bi solders on Cu balls. The reflow property of these solder balls was investigated. Melting of these solder balls was clarified to start at the almost same temperature as that of Sn-2Ag-0.75Cu-3Bi solder. A microstructure composing of (Sn), Ag$_3$Sn, Bi and Cu$_{6}$Sn$_{5}$ phases was found to form in the solder ball, and a reaction layer containing primarily η'-(Au, Co, Cu, Ni)$_{6}$Sn$_{5}$ was found at the interface with Ni/Au coated Cu pad after reflow soldering. By conducting shear test, it was found that the BGA joints using this Cu-core solder balls hardly degraded their joint shear strength during aging at 423K due to the slower growth rate of the η'-(Au, Cu, Ni)$_{6}$Sn$_{5}$ reaction layer at the solder/pad interface.he solder/pad interface.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.260-260
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• 2009

In high-efficiency crystalline silicon solar cell, If high-efficiency solar cells are to be commercialized, It is need to develop superior contact formation method and material that can be inexpensive and simple without degradation of the solar cells ability. For reason of plated metallic contact is not only high metallic purity but also inexpensive manufacture. It is available to apply mass production. Especially, Nickel, Copper are applied widely in various electronic manufactures as easily formation is available by plating. Ni is shown to be a suitable barrier to Cu diffusin as well as desirable contact metal to silicon. Nickel monosilicide has been suggested as a suitable silicide due to its lower resistivitym lower sintering temperature and lower layer stress than $TiSi_2$. In this paper, Nickel as a seed layer and diffusion barrier is plated by electroless plating to make nickel monosilicide.

• Journal of the Korean Ceramic Society
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• v.51 no.5
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• pp.477-480
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• 2014

An $Al_2O_3$-CuO-ZnO (ACZ) precursor powder was synthesized by a facial sol-gel process using a nonionic surfactant span 80 as the chelating agent to improve the surface area and morphology. When creating a hydrogen membrane, several kinds of properties are required, such as easy dissociation of hydrogen molecules, fast hydrogen diffusion, high hydrogen solubility, and resistance to hydrogen embrittlement. ACZ-Ni composite membranes (cermet) were prepared with this precursor and pure Ni powder via the hot press sintering (HPS) method. The ACZ powder was characterized by XRD, BET, and FE-SEM. Hydrogen permeation experiments were performed by Sievert's type of hydrogen permeation membrane equipment. The hydrogen permeability of ACZ/Ni 10 wt% and ACZ/Ni 20 wt% was obtained as 7.2 and $10molm^{-2}s^{-1}$ at RT, respectively. These values of the corresponding membranes were slightly increased with increasing pressures.

• Transactions of Materials Processing
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• v.7 no.5
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• pp.481-488
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• 1998

The active metal brazing was applied to bond Alumina and Ni-Cr steel by Ag-Cu-Zr-Sn alloy and the interfacial microstructure and reaction mechanism were investigated. Polycrystalline monoclinic $ZrO_2$ with a very fine grain of 100-150 nm formed at the alumina grain boundary contacted with Zr segregation layer at the interface. The $ZrO_2$ layer containing the inclusions and cracks were developed at the boundary of inclusion/$ZrO_2$ due to the difference in specific volume. The development of $ZrO_2$ at the interface was successfully explained by the preferential penetration of $ZrO_2$ at the interface was successfully explained by the preferential penetration of Zr atoms a higher concentration of oxygen and a high diffusion rate of Al ions into molten brazing alloy.

• Journal of the Korean Magnetics Society
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• v.13 no.3
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• pp.109-114
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• 2003

The purpose of this study Is to investigate the effect of $V_2$O$_{5}$ addition on the microstructures and magnetic properties of 7.7${\times}$4.5${\times}$1.0 mm sized multi-layer chip inductors prepared by the screen printing method using 0∼0.5 wt％ $V_2O_{5}$-doped NiCuZn ferrite pastes. With increasing the $V_2O_{5}$ content, the exaggerated grain growth of ferrite layers was developed due to the promotion of Ag diffusion and Cu segregation into the grain boundaries oi ferrites, which affected significantly the magnetic properties of the chip inductors. After sintering at $900^{\circ}C$, the inductance at 10 MHZ of the 0.5 wt％ $V_2O_{5}$-doped chip inductor was 3.7 ${\mu}$H less than 4.2 ${\mu}$H of the 0.3 wt% $V_2O_{5}$-doped one, which was thought to be caused by the residual stress at the ferrite layers increased with the promotion of Ag diffusion and Cu segregation. The quality factor of the 0.5 wt% $V_2O_{5}$-doped chip inductor decreased with increasing the sintering temperature, which was considered to be caused by the electrical resistivity of the ferrite layer decreased with the promotion of Ag/cu segregation at the grain boundaries and the growth of the mean grain size of ferrite due to exaggerated grain growth of ferrite layers.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.81-89
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• 2022

The in-situ electromigration(EM) and annealing test were performed at 110, 130, and 150℃ with a current density of 1.3×10⁵ A/cm² conditions to investigate the effect of non-conductive film (NCF) on growth kinetics of intermetallic compound (IMC) in Cu/Ni/Sn-2.5Ag microbump. As a result, the activation energy of the Ni₃Sn₄ IMC growth in the annealing and EM conditions according to the NCF application was about 0.52 eV, and there was no significant difference. This is because the growth rate of Ni-Sn IMC is much slower than that of Cu-Sn IMC, and the growth behavior of Ni-Sn IMC increases linearly with the square root of time, so it has the same reaction mechanism dominated by diffusion. In addition, there is no difference in the activation energy of the Ni₃Sn₄ IMC growth because the EM resistance effect of the back stress according to the NCF application is not large.

• Journal of Welding and Joining
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• v.10 no.3
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• pp.63-72
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• 1992

The joining methods of ceramics to metals which can be expected to obtain high temperature strength are mainly classified into the solid-state diffusion bonding method and the active brazing method. Between these two, the solid-state diffusion bonding method is given attentions as substituting method for active brazing method due to being capable of obtaining higher bonding strength at high temperature and accurate bonding. In this paper, the solid-state diffusion bonding of $Al_{2}$O$_{3}$ ceramics to Ni-Cr-Mo alloy steel (SNCM21) using insert metal was carried out. The insert metal employed in this study was experimentally home-made, Ag-Cu-Ti alloy. Influence of several bonding parameters of $Al_{2}$O$_{3}$SNCM21 joint was quantitatively evaluated by bonding strength test, and microstructural analyses at the interlayer were performed by SEM/EDX. From above experiments, the optimum bonding condition of the solid-state diffusion bonding of $Al_{2}$O$_{3}$/SNCM21 using Ag-Cu-Ti insert metal was determined. Futhermore, high temperature strength and thermal-shock properties of $Al_{2}$O$_{3}$/SNCM21 joint were also examined. The results obtained are as follows. 1. The maximum bonding strength was obtained at the temperature of 95% melting point of insert metal. 2. The high temperature strength of $Al_{2}$O$_{3}$/SNCM21 joint appeared to bemaximum value at test temperature 500.deg.C and the bonding strength with increasingtemperature showed parabolic curve. 3. The strength of thermal-shocked specimens was far deteriorated than those of as-bonded specimens. Especially, water-quenched specimen after heated up to 600.deg. C was directly fractured in quenching.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.34-36
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• 2005

Copper wire bonding is an alternative interconnection technology that serves as a viable and cost saving alternative to gold wire bonding. In this paper, ultrasonic wedge bonding with $25{\mu}m$ copper wire on Au/Ni/Cu metallization of a PCB substrate was performed at ambient temperature. The central composite design of experiment (DOE) approach was applied to optimize the copper wire wedge bonding process parameters. After that, pull test of the wedge bond was performed to study the bond strength and to find the optimum bonding parameters. SEM was used to observe the cross section of the wedge bond. The pull test results show good performance of the wedge bond. Additionally, DOE results gave the optimized parameter for both the first bond and the second bond. Cross section analysis shows a continuous interconnection between the copper wire and Au/Ni/Cu metallization. The diffusion of Cu into the Au layer was also observed.

• Journal of the Korean institute of surface engineering
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• v.49 no.1
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• pp.54-61
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• 2016

Screen printing of commercially available Ag paste is the most widely used method for the front side metallization of Si solar cells. However, the metallization using Ag paste is expensive and needs high temperature annealing for reliable contact. Among many metallization schemes, Ni/Cu/Sn plating is one of the most promising methods due to low contact resistance and mass production, resulting in high efficiency and low production cost. Ni layer serves as a barrier which would prevent copper atoms from diffusion into the silicon substrate. However, Ni based schemes by electroless deposition usually have low thermal stability, and require high annealing process due to phosphorus content in the Ni based films. These problems can be resolved by adding W element in Ni-based film. In this study, Ni-W-P alloys were formed by electroless plating and properties of it such as sheet resistance, resistivity, specific contact resistivity, crystallinity, and morphology were investigated before and after annealing process by means of transmission line method (TLM), 4-point probe, X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM).

• Journal of the Korean Vacuum Society
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• v.5 no.3
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• pp.258-262
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• 1996

We have investigated the changes in magnetoresistive characteristics, interfacial roughness, and preferred orientation with the Fe buffer layer thickness, annealing temperature, and the stacking number of layers variation in Fe/[NiFe/Cu] multilayers by using the 3-gun d.c. magnetron sputtering method. Intensity of the (200) orientation was increased with the increment of the Fe-buffer layer thickness. We found a maximum magnetoresistance ration of 4.7%, when the buffer layer thickness was 70$\AA$, and the field sensitivity also showed a maximum value at the same thickness. We varied the stacking number of multilayers with fixing the Fe buffer layer thickness of 70$\AA$. When the stacking number was 40 layers, maximum MR ratio(5.3%) was observed. With the variation of annealing temperature no change in the MR ratio was found beyond $300^{\circ}C$. But decrement of MR ratio was observed above $300^{\circ}C$. This decrement of the MR ratio was responsible for the increment of paramagnetic mixed layer caused by the diffusion of Cu layer and the change of antiferromagnetic coupling.