• Journal of Welding and Joining
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• 제23권4호
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• pp.34-40
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• 2005

There have been numerous approaches to examine the bonding strengths of solder joints. However, despite the technical and practical limitations, the precedent test methods such as the ball shear and ball pull tests are being used in industrial applications. In this study, the optimum jaw pressure with the modified protrusion jaw was introduced in order to obtain higher successful rate f3r ball pull testing. Furthermore, the pull strengths and fracture modes of Sn-8Zn-3Bi, Sn-4Ag-0.7Cu, and Sn-37Pb eutectic solder after isothermal aging tests ($100^{\circ}C,\;150^{\circ}C$), were evaluated with the protrusion jaw. The pull strength-displacement hysteresis curves and fracture surfaces were carefully investigated to evaluate the correlation between the pull strengths and the fracture modes of each solder. In conclusion, it is verified that Au-Zn IMCs (Intermetallic Compounds) have a detrimental effect on the pull strengths and changed fracture modes of Sn-8Zn-3Bi solder. Meanwhile, the microstructure transformation influences the degradation of pull strengths of Sn-4Ag-0.7Cu and Sn-37Pb solders.

• 마이크로전자및패키징학회지
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• 제6권3호
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• pp.9-18
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• 1999

본 연구에서는 융점 이상에서의 유지시간에 따른 Sn-3.5Ag 및 Sn-37Pb 공정솔더볼과 Au/Ni/Cu 기판 사이의 야금학적 특성을 고찰하였다. 현재 상용되는 리플로 솔더링 장비를 사용하여, 최고 솔더링 온도와 Conveyor 속도를 변화시킴으로써 융점이상에서의 유지시간을 측정하였다. 결과로서 접합부 계면에서 스캘럽 형태의 $Ni_3Sn_4$금속간화합물이 형성되었고, Cu-Sn계 화합물은 관찰되지 않았다. Ni층이 Cu의 확산 장벽으로 작용하였다. 최고 솔더링 온도가 증가함에 따라 금속간화합물 층의 두께가 최고 2.2$\mu\textrm{m}$까지 성장하였다. 스캘럽의 형상은 반구형에서 지름이 더 작은 볼록한 형상으로 변하게 된다. 접합부의 미세경도값은 Sn-3.5Ag와 Sn-37Pb의 공정조직이 성장함에 따라 감소하였다.

• 한국재료학회지
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• 제9권3호
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• pp.288-294
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• 1999

솔더 범프를 사용하는 플립 칩 접속기술에서 범프와 칩 사이에 위치하는 금속 충들의 조합을 UBM(Under Bump Metallurgy)라고 부르며 이 UBM을 어떤 조합으로 사용하는 가에 따라 접속의 안정성이 크게 좌우된다. 본 연구에서는 UBM중에서 솔더 접착 층으로 사용되는 구리 층의 두께를 $1\mu\textrm{m}와 5\mu\textrm{m}$로 하는 한편 barrier 층으로 사용되는 금속 층을 Ti, Ni, Pd으로 변화시키면서 이들 UBM과 공정 납-주석 사이의 계면반응을 살펴보았다. 이를 위해 $100\mu\textrm{m}$ 크기의 솔더 범프를 전해도금법을 사용하여 제작하고 리플로 횟수와 시효시간에 따른 각 UBM에서의 금속간 화합물의 성장을 관찰하였다. $Cu_6Sn_5 \eta'$-상 금속간 화합물이 모든 조건에서 형성되었고 Cu층의 두께가 $5\mu\textrm{m}$로 두꺼운 경우에는 $Cu_3Sn \varepsilon$-상도 관찰되었다. Pd을 사용한 UBM 구조에서는 시효 처리시에 $Cu_6Sn_5$ 상 아래쪽에 $PdSn_4$상이 형성되었다. 또한 이들 계면에서의 금속간 화합물의 성장은 솔더 범프의 접속강도 값과 밀접한 관계를 가진다.

• Archives of Metallurgy and Materials
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• 제65권4호
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• pp.1329-1333
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• 2020

In this study, we have developed Sn-Ag alloy by a simple high energy ball milling technique. We have ball-milled the eutectic mixture of Sn and Ag powders for a period of 45 h. The milled powder for 45 h was characterized for particle size and morphology. Microstructural investigations were carried out by scanning electron microscopy and X-ray diffraction studies. The melting behavior of 45 h milled powder was studied by differential scanning calorimetry. The resultant crystallite size of the Sn(Ag) solid solution was found to be 85 nm. The melting point of the powder was 213.6℃ after 45 h of milling showing depression of ≈6℃ in melting point as compared to the existing Sn-3.5Ag alloys. It was also reported that the wettability of the Sn-3.5Ag powder was significantly improved with an increase in milling time up to 45 h due to the nanocrystalline structure of the milled powder.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.439-449
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• 2002

This paper reviews our recent research works on the interconnection technologies in electronic packaging and assembly. At the aspect of advanced joining methods, laser-ultrasonic fluxless soldering technology was proposed. The characteristic of this technology is that the oxide film was removed through the vibration excitated by high frequency laser change in the molten solder droplet. Application researches of laser soldering technology on solder bumping of BGA packages were carried out. Furthermore, interfacial reaction between SnPb eutectic solder and Au/Ni/Cu pad during laser reflow was analyzed. At the aspect of soldered joints' reliability, the system for predicting and analyzing SMT solder joint shape and reliability(PSAR) has been designed. Optimization design method of soldered joints' structure was brought forward after the investigation of fatigue failure of RC chip devices and BGA packages under temperature cyclic conditions with FEM analysis and experimental study. At the aspect of solder alloy design, alloy design method based on quantum was proposed. The macroproperties such as melting point, wettability and strength were described by the electron parameters. In this way, a great deal of the experimental investigations was replaced, so as to realize the design and research of any kinds of solder alloys with low cost and high efficiency.

• 마이크로전자및패키징학회지
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• 제12권4호통권37호
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• pp.307-313
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• 2005

선형구조의 시편을 사용하여 Sn96.5Ag3.0Cu0.5의 electromigration 특성을 살펴보고 공정 조성의 SnPb의 electromigration특성과 비교, 분석하였다. SnAgCu의 electromigration에 관한 특성 중 시간에 따른 물질의 이동 양상과 여러 가지 electromigration 매개변수 (활성화 에너지, 임계 전류밀도, 확산계수와 유효전하수의 곱)을 살펴보았다. 임계 전류 밀도는 $140^{\circ}C$에서 $2.38{\times}10^4A/cm^2$ 이고 이 값은 $140^{\circ}C$에서 electromigration에 의한 물질 이동이 발생하지 않는 최대 전류 밀도를 나타낸다. 활성화 에너지는 $110-160^{\circ}C$ 온도 범위에서 0.56 eV가 측정되었다. DZ$\ast$의 값은 $110^{\circ}C$에서 $3.12{\times}10^{-10}\;cm^2/s$, $125^{\circ}C$에서 $4.66{\times}10^{-10}\;cm^2/s$, $140^{\circ}C$에서 $8.76{\times}10^{-10}\;cm^2/s$, $160^{\circ}C$에서 $2.14{\times}10^{-9}cm^2/s$ 이었다. 그리고 SnAgCu와 공정 조성의 SnPb 물질의 electromigration 거동 특징은 크게 다른데, SnPb의 경우 음극에서 보이드(void) 형성이 발생하기 전에 잠복 시간이 존재하고 SnAgCu의 경우 잠복 시간이 존재하지 않는다는 점이다. 이는 각 원소들의 확산 기구(diffusion mechanism)의 차이에 기인한 것이라 생각된다.

• 한국주조공학회지
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• 제18권6호
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• pp.570-577
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• 1998

An investigation has been conducted to describe solidification characteristics in Sn-Zn binary system and Sn-Zn-Ag ternary system added by Ag produced by the continuous casting process using heated mold as a basic study for developing Pb-free solder materials. To obtain the continuous casting rods with mirror surface and near net shape at higher casting speed, water flow rates must be increased and mold temperature must be lowered. However, surface tearing in the casting rods occured at lower continuous casting speed while break out occured at higher continuous casting speed even if optimum conditions such as water flow rate and heated mold temperature are determined. Primary ${\alpha}Sn$ and eutectic structure in unidirectioally solidified Sn-Zn alloys were finer with increased casting speed. But, directionality may not be expected for primary Zn in hypereutectic Sn-Zn alloy. It was found that the addition of $0.2{\sim}0.8%$ Ag promoted the growth of primary ${\alpha}Sn$ dendrites. The changes of tensile strength and elongation in Sn-Zn binary alloys were not observed while the increase of tensile strength and the decrease of elongation in Sn-Zn-Ag ternary alloys were observed with increased casting speed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1740-1743
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• 2007

In this study, two types of fatigue tests were conducted. First, cyclic bending tests were performed using the micro-bending tester. A four-point bending test method was adopted, because it induces uniform stress fields within a loading span. Second, thermal fatigue tests were conducted using a pseudo power cycling machine which was newly developed for a realistic testing condition. The pseudo-power cycling method makes up for the weak points in a power cycling and a chamber cycling method. Two compositions of solder are tested in all test condition, one is lead-free solder (95.5Sn4.0Ag0.5Cu) and the other is eutectic lead-contained solder (63Sn37Pb). In the cyclic bending test, the solder that exhibits a good reliability can be reversed depending on the load conditions. The lead-contained solders have a longer fatigue life in the region where the applied load is high. On the contrary, the lead-free solder sustained more cyclic loads in the small load region. A similar trend was detected at the thermal cycling test. A three-dimensional finite element analysis model was constructed. A finite element analysis using ABAQUS was performed to extract the applied stress and strain in the solder joints. A constitutive model which includes both creep and plasticity was employed. Thermal fatigue was occurred due to the creep. And plastic deformation is main damage for bending failure. From the inelastic energy dissipation per cycle versus fatigue life curve, it can be found that the bending fatigue life is longer than the thermal fatigue life.