• Journal of Welding and Joining
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• 제16권3호
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• pp.157-166
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• 1998

Recently as environmental pollution caused by Pb has posed a serious threat to the global environment, the trend to regulate the usage of Pb in electronic industry is one the rise. Currently, the solder alloy with high Pb content, Sn-37%Pb, is utilized in the electronic assembly therefore, the objective of this study is to develop an alternative solder alloy for the existing Sn-37%Pb solder alloy. First thing, this work choosed Sn-5%Pb-1.5%Ag, Sn-5%Pb-1.5%Ag-x%Bi(x=1~5%) for candidate solder alloys, and examined their properties such as melting range, wettability, microhardness, tensile property, oxidation behavior and microstructure. Wettability was on the same level of Sn-37%Pb. Dissolution of Pb ion in Sn-5%Pb solder was 0.46ppm. This solder alloy revealed cellular dendrite microstructure $\beta$-Sn matrix, Pb-rich phase, Ag/Sn, and Cu/Sn Intermetallic compounds. The range of solidification temperature was within 3$0^{\circ}C$. Also these alloy displayed higher tensile strength and lower elongation than Sn-37%Pb. The resistance of oxidation in Sn-5%Pb-1.5%Ag solder alloy was superior to that of Sn-37%Pb solder alloy. But that of Sn-5%Pb-1.5%Ag-5%Bi solder alloy was equal to that of Sn-37%Pb solder alloy.

• Journal of Welding and Joining
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• 제16권3호
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• pp.148-156
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• 1998

The purpose of this study is to investigate the characteristics of Pb-Free Sn-2%Ag-Bi solder alloys. The solder alloys used in this study is Sn-2%Ag-(3,5,7,9%) Bi It is examined that their properties such as melting range, wettability, microstructure, microhardness, and tensile property. The addition of Bi(3,5,7,9%) lowered the melting point of the solder and the melting range was 196~203$^{\circ}C$. The wettability of the solder as equal to that of Sn-37% Pb solder. The morphology of structure did not change largely by addition of Bi. But the structure of cellular dendrite of linear type displayed. The tensile strength of the solder was superior to that of Sn-37%Pb solder. But the elongation was inferior to that of Sn-37%Pb solder. The hardness of Sn-2%Ag solder was tow times and that of Sn-2%Ag-Bi solder was three times of that in Sn-37%Pb solder. But the effect of increment of Bi content did not change largely.

• 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.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2001년도 추계 기술심포지움
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• pp.67-73
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• 2001

To investigate the relationships of solder joint characteristics with solder composition and A:V ratio (solder volume per pad area), Sn-37Pb and Sn-4.0Ag-0.5Cu solder balls with 330, 400, 450 and $457{\mu}{\textrm}{m}$ size were reflowed on same substrate. Sn-37Pb and Sn-4.0Ag-0.5Cu was reflowed at $220^{\circ}C$ and $240^{\circ}C$ respectively by IR-type soldering machine. As a result of reflowed solder- ball diameter(D) and height(H) measurement, D/H was decreased with solder ball size increment in range of 330~450 ${\mu}{\textrm}{m}$. But, D/H was increased in the solder joint for 457 ${\mu}{\textrm}{m}$ size, it was caused possibly by decrement of solder ball height increment compared with solder volume increment. As a result of shear and pull test, joint strength with A:V ratio was high. Joint strength of Sn-4.0Ag-0.5Cu was higher than Sn-37Pb. However, Sn-37Pb had more stable solder joint of small standard deviation. A thick and clean scallop type Ni-Cu-Sn intermetallic compound layer was formed in high A:V ratio and Sn-4.0Ag-0.5Cu solder joint interface.

• 한국표면공학회지
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• 제28권2호
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• pp.67-76
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• 1995

The microstructure of 95wt.%Pb/5wt.%Sn and 63wt.%Sn/37wt.%Pb solders for flip chip bonding process has been characterized. Solders were deposited by thermal evaporation and reflowed in the conventional furnace or by rapid thermal annealing(RTA) process. As-deposited films show columnar structure. The microstructure of furnace cooled 63Sn/37Pb solder shows typical lamellar form, but that of RTA treated solder has the structure showing an uniform dispersion of Pb-rich phase in Sn matrix. The grain size of 95Pb/5Sn solder reflowed in the furnace is about $5\mu\textrm{m}$, but the grain size of RTA treated solder is too small to be observed. The microstructure in 63Sn/37Pb solder bump shows the segregation of Pb phase in the Sn rich matrix regardless of reflowing method. The 63Sn/37Pb solder bump formed by RTA process shows more uniform microstructure. These result are related to the heat dissipation in the solder bump.

• 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.

• 한국진공학회지
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• 제13권3호
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• pp.127-131
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• 2004

BGA(ball grid array) package에서 솔더볼의 피로강도에 대한 솔더 조성에 대한 영향을 조사하기 위하여 패키지 신뢰성 시험을 실시하였다. 공정조성 솔더 63Sn/37Pb, 62Sn/36Pb/2Ag, 63Sn/34.4Pb/2Ag/0.5Sb 솔더를 이용하여 제조된 시편을 MRT Lv3 (moisture resistance test level) 조건에서 전처리 후 T/C(temperature cycle test) 실험을 수행하였다. 각각의 신뢰성 시험에 대하여 전단강도를 측정하였으며, 미세 조직 사진을 얻었다. 또한, SEM (scanning electron microscope)과 EDX (energy dispersive X-ray)를 이용하여 파괴 기구에 대한 분석을 실시하였다. Sn63Pb34.5Ag2Sb0.5 솔더에서 Au-Sn 성장비는 63Sn/37Pb, 62Sn/36Pb/2Ag 솔더에 비해 느리다 솔더 조성에 따른 솔더볼의 전단응력 저하에 대하여 논의하였다.

• 마이크로전자및패키징학회지
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• 제11권2호
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• pp.53-58
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• 2004

63Sn-37Pb 공정솔더의 electromigration 현상을 용이하게 관찰하기 위해 63Sn-37Pb 공정솔 더를 증착하여 스트립 형태의 시편을 제작 후 electromigration 테스트를 실시하였다. $80{\sim}150^{\circ}C$의 온도 및 $1{\times}10^4{\sim}1{\times}10^5\;A/cm^2$의 전류밀도에서 electromigration 테스트시 스트립 형상의 63Sn-37Pb 솔더 합금에서 hillock과 void의 발생이 관찰되었으며, 온도와 전류밀도가 높아질수록 void의 형성이 빨라져서 평균파괴시간이 단축되었다. 평균파괴시간을 이용하여 Black의 식으로부터 구한 63Sn-37Pb 솔더 스트립의 electromigration에 대한 활성화 에너지는 $0.16{\sim}0.5\;eV$이었다.

• 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.

• 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.