• Journal of Welding and Joining
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• 제15권2호
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• pp.36-42
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• 1997

In this paper, stability of initial strength at solder joint with lead free solders, such as Sn-In (52-48%) and Sn-Ag (96.5-3.5wt%) was studied. To obtain at solder joint with high quality, it is very important to control the temperature at the interface of solder joints. It is found that the thermal EMF (electro motive force) occurs betwee lead frame and copper pad on a substrate during reflow soldering process using heated tip. As a result of control the temperature at interface of solder joints, variation of initial strength at solder joint decreases from about $\pm40%$ to $\pm20%$, and it is realized Pb free soldering process using Sn/In and Sn-Ag solder paste.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2001년도 추계 기술심포지움
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• pp.89-98
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• 2001

Pb-free wave soldering process of AC Adapter was implemented by six sigma method using Sn-Cu-Ni type solder. The solder joint appearance, microstructural change, a lift-off phenomenon and reliability were evaluated through thermal shock teal. $(Cu,Ni)_6Sn_5$-type intermetallic compound of which thickness is about 5 micron was found at solder joint between Sn-Cu-Ni solder and copper land. After applying the thermal shock test of as-soldered product up to 750 cycles, no crack was found at the solder joint and the newly developed product was superior to conventions; one in terms of productivity and reliability.

• 마이크로전자및패키징학회지
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• 제8권4호
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• pp.47-52
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• 2001

Sn-Cu-Ni계 솔더를 이용한 AC Adapter의 Pb-Free Wave 솔더링 공정을 Six Sigma기법으로 개발하였다. 솔더 접합부의 외관, 미세조직, Lift-off현상 및 Crack발생 유.무를 관찰하여 접합기구를 규명하고자 하였으며 열 충격시험을 통하여 신뢰성평가를 수행하였다. 솔더 접합부의 Sn-Cu-Ni계 솔더와 Cu Land 사이에는 약 5 $\mu\textrm{m}$ 두께의 $(Cu,Ni)_6/Sn_5$ 형태의 금속간화합물이 발견되었고 열 충격후 750사이클까지는 Crack이 발견되지 않았다. 본 연구로 개발된 제품은 기존의 Sn-Pb솔더를 사용한 제품에 비해서 양산성 및 신뢰성 측면에서 우수한 특성을 나타내었다.

• Journal of Welding and Joining
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• 제19권4호
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• pp.406-412
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• 2001

This study is focussed on the numerical prediction of the thermal fatigue life of a ${\mu}BGA$(Micro Ball Grid Array) solder joint. Numerical method is used to perform three-dimensional finite element analysis for Sn-37mass%Pb. Sn-3.5mass%Ag solder alloys during the given thermal cycling. Strain values, along with the result of mechanical fatigue tests for solder alloys were then used to predict the solder joint fatigue life using the Coffin-Manson equation. In this study, a practical correlation for the prediction of the thermal fatigue life is suggested by using the dimensionless variable $\gamma$. As a result. it could be found that Sn-3.5mass%Ag has longer fatigue life than Sn-37mass%Pb in low cycle fatigue. In addition. the result with ${\gamm}ashow$a good agreement with the FEA results.

• 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.

• 한국자동차공학회논문집
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• 제21권1호
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• pp.145-153
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• 2013

In this study, shear punch-creep (SP-Creep) at Sn-4Ag/Cu pad the joint was tested by using environment-friendly Pb-free solder alloy Sn-4Ag of electronic components. Pb eutectic alloy (Sn-37Pb) joints limited to environmental issues with reflow time (10sec, 30sec, 100sec, 300sec) according to two types of solder alloy joints are compared and evaluated by creep strain rate, rupture time and IMC (Intermetallic Compound) behavior. As the results, reflow time increases with increasing thickness of IMC can be seen at overall 100sec later in case of two solder joints on the IMC thickness of Sn-4Ag solder joints thicker than Sn-37Pb solder joints. In addition, when considering creep evaluation factors, lead-free solder alloy Sn-4Ag has excellent creep resistance more than Pb eutectic alloy. For this reason, the two solder joints, such as in the IMC (Cu6Sn5) was formed. However, the creep resistance of Sn-4Ag solder joints was largely increased in the precipitation strengthening effect of dispersed Ag3Sn with interface more than Sn-37Pb solder joints.

• 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.

• Journal of Welding and Joining
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• 제18권3호
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• pp.89-96
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• 2000

As solder becomes small and fine, the reliability and solderability of solder joint are the critical issue in present electronic packaging industry. Besides the use of lead(Pb) containing solders for the interconnections of microelectronic subsystem assembly and packaging has enviromental problem. In this study, using Sn/Pb and Sn/Ag eutectic solder paste, in order to obtain decrease of solder joint strength with increasing aging time, initial solder joint strength and aging strength after 1000 hour aging at $100^{\circ}C$ were measured by peel test. And in order to obtain the growth of intermetallic compound(IMC) layer thickness, IMC layer thickness was measured by scanning electron microscope(SEM). As a result, solder joint strength was decreased with increasing aging time. The mean IMC layer thickness was increased linearly with the square root of aging time. The diffusion coefficient(D) of IMC layer was found to $1.29{\times}10^{-13}{\;}cm^2/s$ at using Sn/Pb solder paste, 7.56{\times}10^{-14}{\textrm}{cm}^2/s$ at using Sn/Ag solder paste.

• Journal of Welding and Joining
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• 제20권2호
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• pp.77-81
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• 2002

Many kinds of Pb-free solder have been investigated because of the environmental concerns. Sn-Ag-Cu system is well blown as most competitive Pb-free solder. However, since Sn-Ag-Cu system has relatively high melting point compared to Sn-Pb eutectic, it may a limitation, the some application. In this study, Bi and In contained solder of $Sn_3Ag_8Bi_5In$ which has relatively lower melting point, $188~204^{\circ}C$, was investigated. $Sn_3Ag_8Bi_5In$ solder ball of $500\mu\textrm{m}$ diameter was set on the Ni/Cu/Cr-UBM and reflow soldered in the range of $220~240^{\circ}C$ for 5~15s. The maximum shear strength of the solder ball was around 170mN by reflowing at $240^{\circ}C$ for 10s. Intermetallic compound formed on the UBM of Si-wafer was analysed by SEM(scanning electron microscope) and XRD(X-ray diffractometer).

• 마이크로전자및패키징학회지
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• 제25권2호
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• pp.25-30
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• 2018

Sn-Pb솔더는 그동안 자동차 전장품에서 많이 사용되어 왔다. 그러나 최근에 환경과 인체에 대한 유해성 때문에 end-of-life vehicle (ELV)과 같은 국제 환경 규제로 인하여 Pb의 사용이 금지되었다. 이러한 이유로 자동차 전장품을 위한 Pb-free 솔더링에 관한 많은 연구들이 보고 되어 왔다. 한편, 자동차의 연료 효율성과 공간 활용을 위하여 유연성과 경량의 특성을 가지는 플렉시블 기판이 자동차 전장품에 사용되고 있다. 자동차 전장품에 대한 Pb-free 솔더 접합부 특성에 관한 연구들이 많이 진행되었음에도 불구하고 자동차의 사용 환경을 고려한 플렉시블 기판 솔더 접합부에 대한 신뢰성 특성에 관한 연구는 아직 부족한 실정이다. 본 연구에서는 organic solderability preservative (OSP) 및 electroless nickel immersion gold (ENIG) 표면처리 된 플렉시블 기판 위 Sn3.0Ag0.5Cu, Sn0.7Cu, Sn0.5Cu0.01Al(Si) 세 가지 Pb-free 솔더 접합부에 대한 특성을 보고 하였다. 솔더 조성과 기판 표면처리에 따른 접합부의 특성 및 신뢰성을 비교 평가 하기 위하여 인장 강도 시험, 열 충격 시험과 반복 굽힘 시험을 진행 하고 그 결과를 분석하였다. OSP 표면처리 된 기판 접합부에 대한 반복 굽힘 시험 결과 세 종류의 솔더 접합부 모두 파괴는 솔더 내부에서 일어 났으며 Sn3.0Ag0.5Cu 솔더의 접합부에서 반복 굽힘 수명이 가장 길게 나타났다.