• 마이크로전자및패키징학회지
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• 제20권3호
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• pp.45-51
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• 2013

3차원 적층 패키지를 위한 Cu/Sn-3.5Ag 미세범프의 솔더 구조에 따른 금속간화합물 성장거동을 분석하기 위해 솔더 두께가 각각 $6{\mu}m$, $4{\mu}m$인 서로 다른 구조의 미세범프를 $130^{\circ}C$, $150^{\circ}C$, $170^{\circ}C$ 조건에서 실시간 주사전자현미경을 이용하여 실시간 금속간화합물 성장 거동을 분석하였다. Cu/Sn-3.5Ag($6{\mu}m$) 미세범프의 경우, 많은 양의 솔더로 인해 접합 직후 솔더가 넓게 퍼진 형상을 나타내었고, 열처리 시간경과에 따라 $Cu_6Sn_5$ 및 $Cu_3Sn$금속간화합물이 성장한 후, 잔류 Sn 소모 시점 이후 $Cu_6Sn_5$가 $Cu_3Sn$으로 상전이 되는 구간이 존재하였다. 반면, Cu/Sn-3.5Ag($4{\mu}m$) 미세범프의 경우, 적은양의 솔더로 인해 접합 직후 솔더의 퍼짐 현상이 억제 되었고, 접합 직후 잔류 Sn상이 존재하지 않아서 금속간화합물 성장구간이 억제되고, 열처리 시간경과에 따라 $Cu_6Sn_5$가 $Cu_3Sn$으로 상전이 되는 구간만 존재하였다. 두 시편의 $Cu_3Sn$상의 활성화 에너지의 값은 Cu/Sn-3.5Ag($6{\mu}m$) 및 Cu/Sn-3.5Ag($4{\mu}m$) 미세범프가 각각 0.80eV, 0.71eV로 나타났고, 이러한 차이는 반응기구 구간의 차이에 따른 것으로 판단된다. 따라서, 솔더의 측면 퍼짐 보다는 접합 두께가 미세범프의 금속간화합물 반응 기구를 지배하는 것으로 판단된다.

• 한국생산제조학회지
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• 제20권2호
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• pp.187-192
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• 2011

UBM(Under Bump Metallurgy) is very important for successful realization of Flip-Chip technology. In this study, it is investigated the interfacial reactions between various Sn-Ag solder alloys and Ni-P/Au UBM and Cu plate finish. It is also evaluated the shear strength by using the micro shear-punch test method for Sn-37Pb alloy, binary and ternary alloys of environment-friendly Pb-free solder alloys which are applied in the electronic packages. In terms of interfacial microstructure, the Pb-free solder joints have thicker IMCs than the Sn-Pb solder joints. The thickness of IMC is related to Reflow time. The IMC has been observed to grow with the increase in Reflow time. As a result of the shear test, in case of Max. shear strength, Pb-free solder showed the highest strength value and Sn-37Pb showed the lowest strength value 10 be generally condition of Reflow time.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2003년도 춘계학술발표대회 개요집
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• pp.193-195
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• 2003

Micro-structure and shear properties with reflow conditions, reflow temperature and time, for In-48Sn solder on BGA package were examined at the temperature between 140 and 170$^{\circ}C$ for 10 to 3600sec. With increasing reflow temperature and time, the thickness of intermetallic compound formed between solder and pad increased. Shear test indicated shear force increased in the range to a critical value of reflow time, and decreased over a critical reflow time. With increasing reflow temperature and time, the crater occurred on fracture surface because of a increase of crater by voids and IMC particles precipitated in solder.

• Journal of Welding and Joining
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• 제30권2호
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• pp.65-69
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• 2012

Environmental and health concerns over the lead have led to investigation of the alternative Pb-free solders to replace commonly used Pb-Sn solders in microelectronic packaging application. The leading candidates for lead-free solder alloys are presently the near eutectic Sn-Ag-Cu alloys. Therefore, extensive studies on reliability related with the composition have been reported. However, the insufficient drop property of the near eutectic Sn-Ag-Cu alloys has demanded solder compositions of low Ag content. In addition, the solder interconnections in automobile applications like a smart box require significantly improved vibration resistance. Therefore, this study investigated the effect of alloying elements (Ag, Bi, In) on the vibration fatigue strength. The vibration fatigue was conducted in 10~1000Hz frequency and 20Grms. The interface of the as-soldered cross section close to the Cu pad indicated the intermetallic compound ($Cu_6Sn_5$) regardless of solder composition. The type and thickness of IMC was not significantly changed after the vibration test. It indicates that no thermal activities occurred significantly during vibration. Furthermore, as a function of alloying composition, the vibration crack path was investigated with a focus on the IMCs. Vibration crack was initiated from the fillet surface of the heel for QFP parts and from the plating layer of chip parts. Regardless of the solder composition, the crack during a vibration test was propagated as same as that during a thermal fatigue test.

• 마이크로전자및패키징학회지
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• 제27권3호
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• pp.29-34
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• 2020

본 연구에서는 무전해 니켈 도금액 pH 변화에 따른 electroless nickel immersion gold (ENIG)/Sn-3.0wt.%Ag-0.5wt.%Cu(SAC305) 솔더 접합부 취성 파괴 거동에 대하여 평가하였다. ENIG 표면처리를 위한 무전해 니켈 도금액의 pH는 4.0에서 5.5로 변화 시켰다. 무전해 니켈 도금 후 Ni-P 표면 관찰 결과, 도금액의 pH가 낮아질수록 Ni-P 층 nodule 표면에 핀홀이 증가하였다. 솔더링 후 접합부 계면에서는 (Cu,Ni)6Sn5 금속간화합물이 형성되었으며, 무전해 니켈 도금액의 pH가 증가할수록 솔더접합부의 계면 금속간화합물의 두께는 증가하였다. 고속전단 시험을 통하여 ENIG/SAC305 솔더 접합부의 취성파괴 거동을 확인하였으며, 무전해 니켈 도금액의 pH가 증가할수록 솔더접합부의 전단강도는 감소하는 경향을 보였다. 또한, 솔더 접합부의 취성 파괴율은 pH가 5일 때 가장 높은 값을 보였다.

• Current Photovoltaic Research
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• 제7권3호
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• pp.65-70
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• 2019

As a demand of higher power photovoltaic modules, shingled, multi-busbar, half-cell, and bifacial techniques are developed. Multi-busbar module has advantage for large amount of light havesting. And, half-cell is high power module for reducing resistive losses and higher shade tolerance. Recently, researches on multi-busbar is focused on reliability according to adhesion and intermetallic compound between Sn-Pb solder and Ag electrode. And half-cell module is researched to comparing with full-sized cell module for structure difference. In this study, we investigated the factors affecting to efficiency and adhesion of multi-wires half-cell module according to wire thickness, solder thickness, and flux. The results of solar simulator and peel test was that peel strength and efficiency of soldered cell is not related. But samples with flux including high solid material showed high efficiency. The results of FE-SEM and EDX line scan on cross-section between wire and Ag electrode for different flux showed thickness of solder joint between wire and Ag electrode is increasing through solid material increasing. Flux including high solid material would affect to solder behavior on Ag electrode. Higher solid material occurred lower growth of IMC layer because solder permeate to sider of wire ribbon than Ag electrode. And it increased fill factor for high efficiency. In soldering process, amount of solid material in flux and solder thickness are the factor related with characteristic of soldered photovoltaic cell.

• 마이크로전자및패키징학회지
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• 제21권4호
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• pp.97-103
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• 2014

다양한 무연솔더합금 가운데 Sn-58Bi solder는 저융점이며 상대적으로 높은 인장강도를 갖고 있지만 취성적이라는 단점을 갖고 있다. 이러한 Sn-58Bi 솔더의 기계적 강도를 보완하기 위해 epoxy를 함유한 Sn-58Bi 솔더가 연구되어져왔다. 본 연구는 Sn-58Bi 솔더와 Sn-58Bi 에폭시 복합솔더를 이용하여 PCB 기판에 접합한 후, 시효처리에 따른 솔더/기판 계면 미세구조와 기계적 특성변화를 연구하였다. OSP 표면처리된 PCB 기판에 솔더볼을 형성 한 후 85, 95, 105, $115^{\circ}C$에서 100~1000 시간동안 시효처리하였으며, 기계적 특성평가로 저속전단시험을 진행하였다. 시효 처리 시간 및 온도의 증가에 따라 Cu6Sn5 금속간화합물층은 성장하였으며 Sn-58Bi 솔더 금속간화합물층이 Sn-58Bi 에폭시 복합솔더보다 두꺼웠다. 전단시험 결과, Sn-58Bi 에폭시 복합솔더가 Sn-58Bi 솔더보다 약 2배 높은 전단강도 값을 나타냈으며 시효시간이 증가할수록 전단강도 값은 감소하였다.

• 마이크로전자및패키징학회지
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• 제24권1호
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• pp.45-50
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• 2017

본 연구에서는 Sn-0.7Cu-xZn 무연솔더와 OSP 표면처리 된 솔더접합부의 전단강도를 Zn 함유량에 따라 평가하였다. 다섯 종류의 Sn-0.7Cu-xZn (x=0, 0.5, 1.0, 1.5, 2.0 wt.%) 솔더페이스트를 제작한 뒤, OSP(organic solderability preservative) 표면처리 한 PCB(printed circuit board) 기판의 전극에 리플로우 공정으로 180 um 직경의 솔더볼을 형성하였다. 전단강도는 두 가지 조건의 전단속도(0.01, 0.1 m/s)로 고속전단시험(high speed shear test)을 통해 측정하였고, 고속전단시험 시에 측정된 F-x(Force-distance) curve를 통해 파괴에너지(fracture energy)를 계산하였다, SEM(주사전자현미경, scanning electron microscopy)과 EDS(energy dispersive spectroscopy) 분석을 통하여 단면과 파단면을 관찰하였고, 금속간 화합물(intermetallic compound, IMC) 층을 분석하였다. Zn 함유량이 증가함에 따라 금속간 화합물 층의 두께는 감소하였고, Zn 함유량이 0.5 wt.%일 때 가장 높은 전단 강도(shear strength)를 나타내었다. 전체적으로 높은 전단속도 조건의 전단강도 값이 낮은 전단속도 조건의 전단강도보다 높았다.

• Journal of Welding and Joining
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• 제23권3호
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• pp.61-67
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• 2005

Since lead (Pb)-free solders for electronics have higher melting points than that of eutectic Sn-Pb solder, they need higher soldering temperatures. In order to decrease the soldering temperature we tried to coat Sn-Bi layer on $Sn-3.5\%Ag$ solder by electroplating, which applies the mechanism of transient liquid phase bonding to soldering. During heating Bi will diffuse into the $Sn-3.5\%Ag$ solder and this results in decreasing soldering temperature. As bonding samples, the 1608 capacitor electroplated with Sn, and PCB, its surface was finished with electroless-plated Ni/Au, were selected. The $Sn-95.7\%Bi$ coated Sn-3.5Ag was supplied as a solder between the capacitor and PCB land. The samples were reflowed at $220^{\circ}C$, which was lower than that of normal reflow temperature, $240\~250^{\circ}C$, for the Pb-free. As experimental result, the joint of $Sn-95.7\%Bi$ coated Sn-3.5Ag showed high shear strength. In the as-reflowed state, the shear strength of the coated solder showed 58.8N, whereas those of commercial ones were 37.2N (Sn-37Pb), 31.4N (Sn-3Ag-0.5Cu), and 40.2N (Sn-8Zn-3Bi). After thermal shock of 1000 cycles between $-40^{\circ}C$ and $+125^{\circ}C$, shear strength of the coated solder showed 56.8N, whereas the previous commercial solders were in the range of 32.3N and 45.1N. As the microstructures, in the solder $Ag_3Sn$ intermetallic compound (IMC), and along the bonded interface $Ni_3Sn_4$ IMC were observed.

• 한국재료학회지
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• 제24권3호
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• pp.166-173
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• 2014

The effects of printed circuit board electroless nickel immersion gold (ENIG) and organic solderability preservative (OSP) surface finishes on the electromigration reliability and shear strength of Sn-3.5Ag Pb-free solder bump were systematically investigated. In-situ annealing tests were performed in a scanning electron microscope chamber at 130, 150, and $170^{\circ}C$ in order to investigate the growth kinetics of intermetallic compound (IMC). Electromigration lifetime and failure modes were investigated at $150^{\circ}C$ and $1.5{\times}10^5A/cm^2$, while ball shear tests and failure mode analysis were conducted under the high-speed conditions from 10 mm/s to 3000 mm/s. The activation energy of ENIG and OSP surface finishes during annealing were evaluated as 0.84 eV and 0.94 eV, respectively. The solder bumps with ENIG surface finish showed longer electromigration lifetime than OSP surface finish. Shear strengths between ENIG and OSP were similar, and the shear energies decreased with increasing shear speed. Failure analysis showed that electrical and mechanical reliabilities were very closely related to the interfacial IMC stabilities.