• 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.

• 반도체디스플레이기술학회지
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• 제15권4호
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• pp.10-15
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• 2016

In this paper, novel ball grid array (BGA) interconnection process using solderable anisotropic conductive adhesives (SACAs) with low-melting-point alloy (LMPA) fillers have been developed to enhance the processability in the conventional capillary underfill technique and to overcome the limitations in the no-flow underfill technique. To confirm the feasibility of the proposed technique, BGA interconnection test was performed using two types of SACA with different LMPA concentration (0 and 4 vol%). After the interconnection process, the interconnection characteristics such as morphology of conduction path and electrical properties of BGA assemblies were inspected and compared. The results indicated that BGA assemblies using SACA without LMPA fillers showed weak conduction path formation such as solder bump loss or short circuit formation because of the expansion of air bubbles within the interconnection area due to the relatively high reflow peak temperature. Meanwhile, assemblies using SACA with 4 vol% LMPAs showed stable metallurgical interconnection formation and electrical resistance due to the favorable selective wetting behavior of molten LMPAs for the solder bump and Cu metallization.

• 마이크로전자및패키징학회지
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• 제26권3호
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• pp.43-49
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• 2019

본 연구에서는 그래핀 산화(graphene oxide, GO) 분말 복합 Sn-3.0Ag-0.5Cu(in wt.%) 솔더페이스트를 이용한 플렉시블 기판과 SOP(small outline package) 사이의 솔더 접합부의 굽힘 신뢰성 향상에 관한 새로운 접근을 제안하였다. 솔더페이스트에 GO의 첨가는 녹는점에 약간의 영향을 미치었으나 그 차이는 미미한 것으로 나타났다. 한편, GO의 첨가는 리플로우 공정 동안 솔더 접합부의 금속간화합물(intermetallic compound, IMC) 성장과 두께를 억제 할 수 있음을 확인하였다. 더욱이 접합부의 신뢰성에 미치는 영향을 살펴보고자 반복 굽힘 시험을 진행하였으며 GO 분말의 첨가로 솔더 접합부의 반복 굽힘 신뢰성 향상 시킬 수 있었다. 0.2 wt.%의 GO가 첨가된 솔더 접합부의 경우 GO가 첨가되지 않은 경우에 비하여 굽힘 수명은 20% 가량 증가하는 것으로 나타났다. GO가 첨가된 경우 솔더 접합부의 인장 강도와 연성이 증가하게 나타났는데 이러한 GO 첨가에 의한 기계적 특성 향상이 솔더 접합부의 반복 굽힘 신뢰성 향상에 기여한 것으로 추측된다.