• 자원리싸이클링
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• 제31권3호
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• pp.61-72
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• 2022

주요성분이 Sn(93.0 %)-Ag(3.26 %)-Cu(0.89 %)로 구성되는 SAC 폐무연솔더로부터 주석과 은을 회수하기 위한 전기화학적인 방법을 연구하였다. 폐무연솔더의 건식용해, 주조를 통해 제조한 작업전극을 사용하여 분극거동 조사와 정전류 전해용해를 실시하였다. 분극시험 시 활성화영역의 산화전류피크는 전해액의 황산 농도가 높아질수록 감소하였으며, 1 molL^-1 황산농도가 전해용해를 위해 가장 적절한 것으로 나타났다. 정전류 용해 시 전극표면의 부동태층인 양극슬라임이 두꺼워짐에 따라 전극전위가 지속적으로 높아졌으며, 10 mAcm^-2에서 25시간동안 지속적인 전해용해가 가능한 반면 50 mAcm^-2에서는 2.5 시간 이후부터 전극전위가 급상승하여 전해용해반응이 중단되었다. 정전류 전해용해 시 은은 양극슬라임에 농축되었으며, 전해액내 염소이온의 농도가 0.3 molL^-1인 경우 농축율이 미첨가 조건보다 12.7% 높은 94.3%를 나타내었다. 또한 염소이온의 첨가에 의해 전해액내 주석이온의 안정성을 높이고 주석의 전착전류효율을 향상시킬 수 있었다.

• Tribology and Lubricants
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• 제24권1호
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• pp.27-33
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• 2008

A micro-impression creep machine was designed and developed, adopting a small punch in diameter of 150 um, displacement gage with an accuracy of sub-${\mu}m$ scale, and load-cell with an accuracy of mN scale in order to investigate creep behavior of small solder ball in diameter of less than 1 mm. Creep behavior of lead-free solder ball(Sn-3.0Ag-0.5Cu) in diameter of $760\;{\mu}m$ was investigated in the stress range of $8{\sim}60\;MPa$ and at $303\;K{\sim}393\;K$. The applied load became decreased slightly and continuously in the creep rate of $10^{-4}/s$ range during the current experiments. Also, the machine frame was so sensitive to the environmental temperature that nm scaled displacement recording was unstable according to the change in environmental temperature.

• Journal of Welding and Joining
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• 제24권6호
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• pp.21-27
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• 2006

This study was focused on the evaluation of the thermo-mechanical board-level reliability of Pb-bearing and Pb-free surface mount assemblies. The composition of Pb-bearing solder was a typical Sn-37Pb and that of Pb-free solder used in this study was a representative Sn-3.0Ag-0.5Cu in mass %. Thermal shock test was chosen for the reliability evaluation of the solder joints. Typical $Cu_6Sn_5$ intermetallic compound (IMC) layer was formed between both solders and Cu lead frame at the as-reflowed state, while a layer of $Cu_3Sn$ was additionally formed between the $Cu_6Sn_5$ and Cu lead frame during the thermal shock testing. Thickness of the IMC layers increased with increasing thermal shock cycles, and this is very similar result with that of isothermal aging study of solder joints. Shear test of the multi layer ceramic capacitor(MLCC) joints was also performed to investigate the degradation of mechanical bonding strength of solder joints during the thermal shock testing. Failure mode of the joints after shear testing revealed that the degradation was mainly due to the excessive growth of the IMC layers during the thermal shock testing.

• International Journal of Korean Welding Society
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• 제5권1호
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• pp.15-28
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• 2005

The ball shear test was investigated in terms of the effects of test parameters, i.e., shear height and shear speed, with an experimental and non-linear finite element analysis for evaluating the solder joint integrity of area array packages. Two representative Pb-free solder compositions were examined in this work: Sn-3.5Ag-0.75Cu and In-48Sn. The substrate was a common SMD type with solder bond pad openings of 460 $\mu$m in diameter. The microstructural investigations were carried out using SEM, and the IMCs were identified with EDS. Shear tests were conducted with the two varying test parameters. It could be observed that increasing shear height, at fixed shear speed, has the effect of decreasing shear force for both Sn-3.5Ag-0.75Cu and In-48Sn solder joints, while the shear force increased with increasing shear speed at fixed shear height. Too high shear height could cause some undesirable effects on the test results such as unexpected high standard deviation values or shear tip sliding from the solder ball. The low shear height conditions were favorable for screening the type of brittle interfacial fractures or the degraded layers in the interfaces. The shear speed conditions were discussed with the stress analyses of the solder ball, and we cannot find any conspicuous finding which is related to optimum shear speed from the stress analyses.

• 마이크로전자및패키징학회지
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• 제18권2호
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• pp.17-27
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• 2011

본 논문에서는 솔더의 온도 변화에 따른 변형 거동을 평가하기 위하여 솔더 재료의 열변형 거동을 파악할 수 있는 전단시편을 고안하여 온도변화에 따르는 열변형 실험과 유한요소해석을 수행하였다. 전단시편은 열팽창계수가 다른 두 금속 막대와 그 사이 공간에 접합된 솔더로 구성되어 있으며, 솔더는 유연 솔더 (Sn/36Pb/2Ag)와 무연 솔더 (Sn/3.0Ag/0.5Cu) 두가지를 대상으로 하였다. 실시간 무아레 간섭계를 이용하여 세 온도 사이클 동안의 각 온도단계에서 변 위 분포를 나타내는 간섭무늬를 얻고 그로부터 온도에 따른 유연 솔더와 무연 솔더의 열변형 특성을 비교하였다. 유한요소해석을 통하여 여러 연구자가 제시한 솔더의 점소성 물성치를 평가하였으며 유연 솔더의 경우에는 Darveaux가 제안한 Anand 모델, 무연 솔더의 경우 Chang이 제안한 Anand 모델을 사용한 해석 결과가 실험 결과와 가장 일치한다는 것을 밝혔다. 평가된 재료 모델을 사용하여 무연 솔더와 유연 솔더가 포함된 전단시편을 유한요소 해석하고 솔더의 점소성 거동 을 자세하게 분석하였다.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2003년도 기술심포지움 논문집
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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.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.24-24
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• 2009

ENIG(Electroless Nickel Immersion Gold) is the surface treatment method that is used most widely at fine pitch's SMT and BGA packaging process. In this paper, we have studied the effect of P content variation during ENIG process on those phenomena related to the solder joint. The effect of P content was discussed using the results obtained from FE-SEM, EPMA, EDS and FIB. Finally, it was concluded that the more P-content in Ni layer, the thicker P-rich layer.

• 한국표면공학회지
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• 제36권5호
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• pp.373-378
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• 2003

With increasing environmental concerns, application of lead-free solder and fluxless soldering process have been taken attention from the electronic packaging industry. Plasma treatment is one of the soldering methods for the fluxless soldering, and it can prevent environmental pollution cased by flux. On this study fluxless soldering process under $Ar-H_2$plasma using lead free solders such as Sn-3.5 wt%Ag, Sn-3.5 wt%Ag-0.7 wt%Cu and Sn-37%Pb for a reference was investigated. As the plasma reflow has higher soldering temperature than normal air reflow, the effects of UBM(Under Bump Metallization) thickness on the interfacial reaction and bonding strength can be critical. Experimental results showed in case of the thin UBM, Au(20 nm)/Cu(0.3 $\mu\textrm{m}$)/Ni(0.4 $\mu\textrm{m}$)/Al(0.4 $\mu\textrm{m}$), shear strength of the soldered joint was relatively low as 19-27㎫, and it's caused by the crack observed along the bonded interface. The crack was believed to be produced by the exhaustion of the thin UBM-layer due to the excessive reaction with solder under plasma. However, in case of thick UBM, Au(20 nm)/Cu(4 $\mu\textrm{m}$)/Ni(4 $\mu\textrm{m}$)/Al(0.4 $\mu\textrm{m}$), the bonded interface was sound without any crack and shear strength gives 32∼42㎫. Thus, by increasing UBM thickness in this study the shear strength can be improved to 50∼70%. Fluxed reflow soldering under hot air was also carried out for a reference, and the shear strength was 48∼52㎫. Consequently the fluxless soldering with plasma showed around 65∼80% as those of fluxed air reflow, and the possibility of the $Ar-H_2$ plasma reflow was evaluated.

• Journal of Welding and Joining
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• 제31권1호
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• pp.6-10
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• 2013

• Journal of Welding and Joining
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• 제32권6호
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• pp.75-81
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• 2014

Usage of heavy metal element (Pb, Hg and Cd etc.) in electronic devices have been restricted due to the environmental banning of the European Union, such as WEEE and RoHS. Therefore, it is needed to develop the Pb-free solder plated ribbon in photovoltaic (PV) module. This study described that degradation characteristics of PV module under damp heat (DH, $85^{\circ}C$ and 85% R.H.) condition test for 1,000 h. Solar cell ribbons were utilized to hot dipping plate with Pb-free solder alloys. Two types of Pb-free solder plated ribbons, Sn-3.0Ag-0.5Cu (SAC305) and Sn-48Bi-2Ag, and an electroless Sn-40Pb solder hot dipping plated ribbon as a reference sample were prepared to evaluate degradation characteristics. To detect the degradation of PV module with the eutectic and Pb-free solder plated ribbons, I-V curve, electro-luminescence (EL) and cross-sectional SEM analysis were carried out. DH test results show that the reason of maximum power (Pm) drop was mainly due to the decrease fill factor (FF). It was attributed to the crack or oxidation of interface between the cell and the ribbon. Among PV modules with the eutectic and Pb-free solder plated ribbon, the PV module with SAC305 ribbon relatively showed higher stability after DH test than the case of PV module with Sn-40Pb and Sn-48Bi-2Ag solder plated ribbons.