• 대한금속재료학회지
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• 제47권12호
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• pp.842-851
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• 2009

The long-term reliability of Sn-0.3wt%Ag-0.7wt%Cu solder joints was evaluated and compared with Sn-3.0wt%Ag-0.5wt%Cu under thermal shock conditions. Test vehicles were prepared to use Sn-0.3Ag-0.7Cu and Sn-3.0Ag-0.5Cu solder alloys. To compare the shear strength of the solder joints, 0603, 1005, 1608, 2012, 3216 and 4232 multi-layer ceramic chip capacitors were used. A reflow soldering process was utilized in the preparation of the test vehicles involving a FR-4 material-based printed circuit board (PCB). To compare the shear strength degradation following the thermal shock cycles, a thermal shock test was conducted up to 2,000 cycles at temperatures ranging from $-40^{\circ}C$ to $85^{\circ}C$, with a dwell time of 30 min at each temperature. The shear strength of the solder joints of the chip capacitors was measured at every 500 cycles in each case. The intermetallic compounds (IMCs) of the solder joint interfaces werealso analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results showed that the reliability of Sn-0.3Ag-0.7Cu solder joints was very close to that of Sn-3.0Ag-0.5Cu. Consequently, it was confirmed that Sn-0.3Ag-0.7Cu solder alloy with a low silver content can be replaced with Sn-3.0Ag-0.5Cu.

• 한국전기전자재료학회논문지
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• 제16권6호
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• pp.549-554
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• 2003

The purpose of this paper is to investigate the solder properties by the change of P mass percentage. Tension test, wetting balance test, spread test, and analysis of intermetallic compound after isothermal aging of Sn-2.5Ag-0.7Cu-0.005P, Sn-2.5Ag-0.7Cu-0.01P, Sn-2.5Ag-0.7Cu-0.02P, Sn-0.7Cu-0.005P were performed. Adding P in the solder alloys resulted in improvement of tensile strength, reduction of intermetallic compound growth, reduction of oxidization in fusible solders under wave soldering. After comparing solder alloy containing P with tin-lead eutectic solder alloy, P contained solders alloys showed much better solder properties than eutectic solder alloy. Furthermore, this solder alloy presented remarkable properties than any other lead-free solder alloy.

• 마이크로전자및패키징학회지
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• 제10권4호
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• pp.81-86
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• 2003

상부 칩과 하부 기판이 모두 Si으로 구성되어 있는 플립칩 패키지 시편을 제조하여 Sn-3.5Ag 솔더범프의 electromigration 거동을 분석하였다. Sn-3.5Ag 솔더범프의 electromigration 테스트 초기부터 파단이 일어나기 직전까지는 플립칩 시편의 저항이 거의 변하지 않았으나, 파단이 발생하는 순간 저항값이 크게 증가하였다. 전류밀도 $3\times 10^4$∼$4\times 10^4$A/$\textrm{cm}^2$에서 Sn-3.5Ag 솔더범프의 electromigration에 대한 활성화 에너지는 ∼0.7 eV로 분석되었다. Sn-3.5Ag 솔더범프의 cathode 부위의 솔더/UBM 계면에서 void의 형성 및 전파에 의해 솔더범프의 파단이 발생하였다.

• 한국전기전자재료학회논문지
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• 제30권2호
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• pp.119-125
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• 2017

We have studied the effects of Ag on the characteristics of $Sn_{43}Bi_{57}Ag_x$(wt%) lead-free solders for photovoltaic ribbon. Ag atoms in the solder formed an alloy phase of Ag3Sn after reacting with some part of Sn atoms, while they did not react with Bi atoms, but decreased the mean size of Bi solid phase and the thickness of solder. When Ag atoms of 3.0 wt% was added to eutectic $Sn_{43}Bi_{57}$(wt%) solder, it showed the optimally useful results that the peel strength of photovoltaic ribbon greatly increased and the sheet resistance of the solder decreased. In the meanwhile, the eutectic $Sn_{43}Bi_{57}$(wt%) solder showed a low melting temperature of $138.9^{\circ}C$, and showed a very similar result regardless of the added amount of Ag atoms.

• 마이크로전자및패키징학회지
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• 제18권2호
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• pp.49-55
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• 2011

전자기기에서의 고장 중 대부분은 작동 중 발생하는 열과 충격에 기인한다. 이 열과 충격은 PCB(Printed Board) 부품의 접합부 계면에 균열을 야기 시키고, 이 균열은 금속간 화합물(Intermetallic Compound: IMC)의 형성과 밀접한 관계를 가진다. 본 연구에서는 Sn-Ag-Cu계의 Ag함량을 변화한 Sn-1.0Ag-0.5Cu와 Sn-1.2Ag-0.5Cu 및 Sn-3.0Ag-0.5Cu의 3가지 조성의 솔더로 접합한 소재를 대상으로 1000시간 까지 등온시효(Isothermal Aging) 하였다. 등온시효 동 안 솔더(Solder)의 계면에 발생하는 IMC(Intermetallic Compound) 성장이 관찰되었으며, solder 접합부의 기계적 특성은 굽힘충격 시험법을 이용하여 평가되었다. 그 결과 시효처리 전에는 Ag 함량이 낮은 solder의 굽힘충격 특성이 우수하게 나타났으나, 시효처리 후에는 반대의 결과를 나타내었다. 이 결과는 IMC layer 주변에 생성된 미세한 $Ag_3Sn$ 및 조대한 $Cu_6Sn_5$와 관련되어, 미세한 $Ag_3Sn$이 충격을 완화한 것으로 나타나 이에 따라 굽힘충격 특성에 차이가 나타남을 알 수 있었다.

• 마이크로전자및패키징학회지
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• 제9권2호
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• pp.39-43
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• 2002

48 $\mu$BGA 패키지에 Sn-37Pb 공정 솔더와 Sn-0.7Cu, Sn-3.5 Ag, Sn-2.0Ag-0.75Cu, Sn-2.0Ag-0.7Cu-3.0Bi 4종류의 무연 솔더를 적용하여, 미세 솔더 볼의 경도와 조성에 따른 솔더 접합부의 전단강도에 대해서 연구하였다. 실험 결과, 솔더 볼의 짖눌림은 Sn-2.0Ag-0.7Cu-3.0Bi에서 0.043mm로 큰 경도값을 얻었다. 또한 전단 강도 값은 무연 솔더가 Sn-37Pb 솔더보다 높았으며, Sn-2.0Ag-0.7Cu-3.0 Bi에서 최대 52% 높은 값을 나타내었다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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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.

• Applied Science and Convergence Technology
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• 제23권6호
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• pp.345-350
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• 2014

The surface oxidation mechanism of lead-free solder alloys has been investigated with multiple reflow using X-ray photoelectron spectroscopy. It was found that the solder surface of Sn-Ag-Cu-In solder alloy is surrounded by a thin $InO_x$ layer after reflow process; this coating protects the metallic surface from thermal oxidation. Based on this result, we have performed a wetting balance test at various temperatures. The Sn-Ag-Cu-In solder alloy shows characteristics of both thermal oxidation and wetting balance better than those of Sn-Ag-Cu solder alloy. Therefore, Sn-Ag-Cu-In solder alloy is a good candidate to solve the two problems of easy oxidation and low wettability, which are the most critical problems of Pb-free solders.

• 한국재료학회지
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• 제8권11호
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• pp.1011-1019
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• 1998

Pb의 환경오염 문제를 발생하지 않는 저농도 Pb 솔도합금을 개발하기 위하여, 새로운 Sn-5%Pb-1.5%Ag-x%In계 합금 조성을 설계하고, 이 합금의 융점, 젖음성, 상분석, 경도, 인장강도, 드로스성을 평가하여, Sn-37%Pb 솔더오 대체 가능성을 타진하였다. Sn-37%Pb 솔도 합금의 Pbdldhs 용출농도는 국제규제치인 3ppm보다 훨씬 적은 0.46ppm이었고, 환경문제를 유발하지 않는 것으로 확인되었다. 이 합금계의 융점은 $183-192^{\circ}C$이고, 응고온도범위도 $5^{\circ}C$내외로 매우 좁았다. 젖음성은 In의 첨가양에 따라 큰 차이가 거의 없었으며, Sn-375Pb와 비슷하였다. 융점 및 젖음성 측면에서 Sn-37%Pb와 대체 가능한 것으로 판단되었다. 경도는 Sn-37%Pb의 약 1.5배이고, 인장강도는 Sn-37%Pb의 것보다 높고, In의 첨가량에 따라 증가하였지만, 연신율은 감소하였다. In이 1% 첨가된 합금에서는 수지 상정 경계에 Ag3Sn과 Pb가 정출되고, 3% 이상에서는 $Ag_3Sn$과 $Ag_3In$ 및 Pb가 정출되었다. 드로스 생성속도는 Sn-37%Pb 합금이 Sn-5%Pb-1.5%Ag 합금보다 빠르고, In을 첨가할수록 느리고 2%의 In을 첨가한 합금은 180분에서도 거의 드로스가 발생하지 않았다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년도 춘계 학술대회 개요집
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• pp.30-32
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• 2006

The interfacial reaction and reliability of eutectic Sn-Pb and Pb-free eutectic Sn-Ag ball-grid-array (BGA) solders with an immersion Ag-plated Cu substrate were evaluated following isothermal aging at $150^{\circ}C$. During reflowing, the topmost Ag layer was dissolved completely into the molten solder, leaving the Cu layer exposed to the molten solder for both solder systems. A typical scallop-type Cu-Sn intermetallic compound (IMC) layer was formed at both of the solder/Cu interfaces during reflowing. The thickness of the Cu-Sn IMCs for both solders was found to increase linearly with the square root of isothermal aging time. The growth of the $Cu_3Sn$ layer for the Sn-37Pb solder was faster than that for the Sn-3.5Ag solder, In the case of the Sn-37Pb solder, the formation of the Pb-rich layer on the Cu-Sn IMC layer retarded the growth of the $Cu_6Sn_5$ IMC layer, and thereby increased the growth rate of the $Cu_3Sn$ IMC layer. In the ball shear test conducted on the Sn-37Pb/Ag-plated Cu joint after aging for 500h, fracturing occurred at the solder/$Cu_6Sn_5$ interface. The shear failure was significantly related to the interfacial adhesion strength between the Pb-rich and $Cu_6Sn_5$ IMC layers. On the other hand, all fracturing occurred in the bulk solder for the Sn-3.5Ag/Ag-plated Cu joint, which confirmed its desirable joint reliability.