• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.231-231
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• 2015

무전해 Ni의 Metal turnover (MTO)가 증가함에 따라, Ni과 Sn-Ag-Cu솔더간 계면 금속간화합물층의 두꺼워지고, Ni-Sn-P층에 형성된 Nano void의 수가 많아지게 되어 취성파괴가 증가한다.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.72-72
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• 2009

전자부품의 내부접속 및 파워반도체의 다이본딩과 같은 1차실장에는 고온환경에서의 사용과 2차실장에서의 재용융방지를 위해 높은 액상선온도 및 고상선온도를 필요로 하여, Pb-5wt%Sn, Pb-2.5wt%Ag로 대표되는 납성분 85%이상의 고온솔더가 널리 사용되고 있다. 생태계와 인체에 대한 납의 유해성이 보고된 이래, 무연솔더에 대한 연구가 활발히 진행되어 왔으나, Sn-Ag-Cu계로 대표되는 Sn계 합금으로 대체 중인 중온용 솔더와는 달리, 고온용 솔더에 대해서는 대체합금에 대한 연구가 미흡한 실정이다. 대체재의 부재로 인해 기존의 납을 다량함유한 솔더로 1차실장이 지속됨으로서, 2차실장의 무연화에도 불구하고 전자부품 및 기기의 재활용에 큰 어려움을 겪고 있다. 지금까지 고온용 무연솔더로서는 융점에 근거해 Au-(Sn, Ge, Si)계, Bi-Ag계, Zn-(Al, Sn)계의 극히 제한된 합금계만이 보고되어 왔다. Au계 솔더는 현재 플럭스를 사용하지 않는 광학, 디스플레이 분야 등 고부가가치 공정에 사용되고 있으나, 합금가격이 매우 비싸며 가공성이 나빠 대체재료로서는 적합하지 않다. Bi-Ag계 솔더 또한 취성합금으로 와이어 및 박판으로 가공하는데 어려움이 크며, 솔더로서 중요한 특성중 하나인 전기전도도 및 열전도도가 나쁜 편이다. 이에 비해, Zn계 합금은 비교적 낮은 합금가격, 적절한 가공성과 뛰어난 인장강도, 우수한 전기전도도 및 열전도도를 지녀, 고온용솔더 대체재료의 유력한 후보로 생각된다.이전 연구에서, 필자의 연구그룹은 Zn-Sn계 합금을 고온용 무연솔더로서 제안한 바 있다. Zn-Sn계 합금은 충분히 높은 융점과 함께, 금속간화합물이 없는 미세조직, 우수한 기계적 특성, 높은 전기전도도 및 열전도도 등의 장점을 나타내었다. 본 연구에서는 기초합금특성상 고온솔더로서 다양한 장점을 지닌 Zn-30wt%Sn합금을 고온용 솔더의 대표적인 적용의 하나인 다이본딩에 적용하여, 접합부의 강도 및 미세조직, 열피로 신뢰성에 대해 분석을 함으로서 실제 공정에의 적용가능성에 대해 검토하였다. Zn-30wt%Sn을 이용해 Au/TiN(Titanium nitride) 코팅한 Si다이를 AlN-DBC(aluminum nitride-direct bonded copper)기판에 접합한 결과, 양측에 완전히 젖은 기공이 없는 양호한 다이접합부를 얻었으며, 솔더내부에는 금속간화합물을 형성하지 않았다. Si다이와의 계면에는 TiN만이 존재하였으며, Cu와의 계면에는 Cu로부터 $Cu_5Zn_8,\;CuZn_5$의 반응층을 형성하였다. 온도사이클시험을 통한 열피로특성평가에서, Zn-30wt%Sn를 이용한 다이접합부는 1500사이클 지점에서 Cu와 Cu-Zn금속간화합물의 사이에서 피로균열이 형성되며, 접합강도가 크게 감소하였다. 열피로특성 향상을 위해 Cu표면에 TiN코팅을 하여 Zn-30wt%Sn 솔더로 다이접합한 결과, Si다이와 기판 양측에 TiN만으로 구성된 계면을 형성하였으며, TEM관찰을 통해 Zn-30wt%Sn과 극히 미세한 접합계면이 형성하고 있음을 확인하였다. Zn-wt%30Sn솔더와 TiN층의 병용으로 2000사이클까지 미세조직의 변화 및 강도저하가 없는 극히 안정된 고신뢰성의 다이접합부를 얻을 수가 있었다.

• Journal of the Microelectronics and Packaging Society
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• v.5 no.1
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• pp.7-18
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• 1998

In the flip chip interconnection on organic substrates using eutectic Pb/Sn solder bumps highly reliable Under Bump Metallurgy (UBM) is required to maintain adhesion and solder wettability. Various UBM systems such as 1$\mu$m Al/0.2$\mu$m Pd/1$\mu$m Cu, laid under eutectic Pb/Sn solder were investigated with regard to their interfacial reactions and adhesion proper-ties. The effects of numbers of solder reflow and aging time on the growth of intermetallic compounds (IMCs) and on the solder ball shear strength were investigated. Good ball shear strength was obtained with 1$\mu$m Al/0.2$\mu$m Ti/5$\mu$m Cu and 1$\mu$m Al/0.2$\mu$m ni/1$\mu$m Cu even after 4 solder reflows or 7 day aging at 15$0^{\circ}C$. In contrast 1$\mu$m Al/0.2$\mu$m Ti/1$\mu$m Cu and 1$\mu$mAl/0.2$\mu$m Pd/1$\mu$m 쳐 show poor ball shear strength. The decrease of the shear strength was mainly due to the direct contact between solder and nonwettable metal such as Ti and Al resulting in a delamination. In this case thin 1$\mu$m Cu and 0.2$\mu$m Pd diffusion barrier layer were completely consumed by Cu-Sn and pd-Sn reaction.

• 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 the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.121-128
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• 2005

Solder joints in microelectronic devices are frequently operated at an elevated temperature in service. They also experience plastic deformation caused by temperature excursion and difference in thermal expansion coefficients. Deformed solders can go through a recovery and recrystallization process at an elevated temperature, which would alter their microstructure and mechanical properties. In this study, to predict the changes in mechanical properties of Pb-free solder joints at high temperatures, the high temperature microhardness of several Pb-free and composite solders was measured as a function of temperature, deformation, and annealing condition. Solder alleys investigated include pure Sn, Sn-0.7Cu, Sn-3.5Ag, Sn-3.8Ag-0.7Cu, Sn-2.8Ag-7.0Cu (composite), and Sn-2.7Ag-4.9Cu-2.9Ni (composite). Numbers are all in wt.$\%$ unless specified otherwise. Solder pellets were cast at two cooling rates (0.4 and $7^{\circ}C$/s). The pellets were compressively deformed by $30\%$ and $50\%$ and annealed at $150^{\circ}C$ for 2 days. The microhardness was measured as a function of indentation temperature from 25 to $130^{\circ}C$. Their microstructure was also evaluated to correlate with the changes in microhardness.

• Resources Recycling
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• v.14 no.1
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• pp.17-25
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• 2005

In order to recover valuable metals from the waste electronic scrap, bioleaching of Cu, Zn, Al, Co, Ni, Sn and Pb was carried out using Thiobacillus ferrooxidans as a leaching microorganism in a shaking flask. In a preliminary study, to obtain the data on the leaching of Cu, Zn, Al, Co and Ni, the metal leaching was accomplished using metal powers instead of electronic scrap. The leaching percentaga of Cu, Zn, Co, Al and Ni powers was reduced with the increase of metal power concentration in solution. Below the metal concentration of 0.5 g/L, more than 85% of Cu, Co and Zn powers was leached out. At the electronic scrap concentration of 100 g/L, Thiobacillus ferrooxidans were able to leach more than 90% of the available Cu and Co while Al, Zn and Ni were able to leach less than 40%. Pb and Sn were not detected in the leachate. Pb was precipitated as PbSO$_4$, whereas Sn precipitated probably as SnO.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.246-249
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• 2000

The effects of Zr on the mechanical workability and tensile strength of Cu-Ni-Mn-Sn-Al alloys have been investigated and the following results were obtained. The mechanical workability of Cu-Ni-Mn-Sn-Al alloys are increased with addition of Zr. And the surface cracks of specimen were not produced in Zr added Alloys. Especially in condition of hot-worked beyond the 90% working ratio, Zr contained specimen showed intra-granule crack propagation but Zr-free specimen showed inter-granule mode. The tensile strength have maximum value in 0.05% Zr contained alloy. The aging mechanism of Cu-Ni-Mn-Sn-Al alloys were varied by Zr addition.

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

• Conservation Science in Museum
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• v.2
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• pp.57-68
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• 2000

This study is a scientific analysis of 12 bronze materials which were excavated from Sanoisa temple in Chongju. Analysis of crystalline shape, size and distribution of the each sample metal suggested that they can be classified as tableware(wrought), vessels for memorial service(casting) and bell bronze, which is the same result as classification based on elemental composition. Most of the tableware are forging wares with composition of 8:2:0 in Cu:Sn:Pb, and vessels for memorial service are casting wares whose composition is 7:1:2 in Cu:Sn:Pb, and bell bronze's composition is Cu:Sn:Pb = 85:10:5/9:1:0. The result clearly shows that composition is closely related with usage and manufacturing method of wares. Trace elements such as Co, Fe and As are the elements with high correlation coefficient with Cu, which means they exist as impurities in Cu, and the content of As showed an increase in the order of tableware, memorial service vessels and bell bronze. In addition, the analysis of lead isotope ratio showed that 3 bronze materials with high lead content were made from the lead coming from Japan and China. The composition of the solder was Cu:Sn:Pb = 83:12:5 where small Pb crystals were distributed evenly.

• Korean Journal of Materials Research
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• v.19 no.1
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• pp.13-17
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• 2009

A semi-empirical method to estimate the surface tension of molten alloys at different oxygen partial pressures is suggested in this study. The surface tension of molten Ag-Sn and Ag-Cu alloys were calculated using the Butler equation with the surface tension value of pure substance at a given oxygen partial pressure. The oxygen partial pressure ranges were $2.86{\times}10^{-12}$－$1.24{\times}10^{-9}$ Pa for the Ag-Sn system and $2.27{\times}10^{-11}$－$5.68{\times}10^{-4}$ Pa for the Ag-Cu system. In this calculation, the interactions of the adsorbed oxygen with other metallic constituents were ignored. The calculated results of the Ag-Sn alloys were in reasonable accordance with the experimental data within a difference of 8%. For the Ag-Cu alloy system at a higher oxygen partial pressure, the surface tension initially decreased but showed a minimum at $X_{Ag}$ = 0.05 to increase as the silver content increased. This behavior appears to be related to the oxygen adsorption and the corresponding surface segregation of the constituent with a lower surface tension. Nevertheless, the calculated results of the Ag-Cu alloys with the present model were in good agreement with the experimental data within a difference of 10%.