• 대한금속재료학회지
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• 제47권9호
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• pp.580-585
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• 2009

The effects of shear speed and tip height on the high speed shear test of Sn-3.0wt.%Ag-0.5wt.%Cu ball joints were investigated. Solder balls of $450{\mu}m$ in diameter were reflowed at $245^{\circ}C$ on a FR4 PCB (Printed Circuit Board) in order to obtain a sample for the high-speed shear test. The UBM was comprised of Cu/Ni/Au, and the shear speed and tip height varied from 0.5 to 3.0 m/s, and from 10 to $135{\mu}m$, respectively. According to the experimental results, faster shear speed enhanced the shear strength of the solder joints, regardless of the tip height. The fraction of ductile (solder) fracture decreased when the shearing speed was raised from 0.5 to 3.0 m/s. With an increasing tip height from 10 to 50 and $135{\mu}m$, the fracture mode changed from pad lift to mixed (ductile and brittle) and ductile fracture, respectively, while the shearing energy also increased in the same order. The shear energy had a proportional relationship with the fraction of the solder fracture.

• International Journal of Korean Welding Society
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• 제5권1호
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• pp.15-28
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• 2005

The ball shear test was investigated in terms of the effects of test parameters, i.e., shear height and shear speed, with an experimental and non-linear finite element analysis for evaluating the solder joint integrity of area array packages. Two representative Pb-free solder compositions were examined in this work: Sn-3.5Ag-0.75Cu and In-48Sn. The substrate was a common SMD type with solder bond pad openings of 460 $\mu$m in diameter. The microstructural investigations were carried out using SEM, and the IMCs were identified with EDS. Shear tests were conducted with the two varying test parameters. It could be observed that increasing shear height, at fixed shear speed, has the effect of decreasing shear force for both Sn-3.5Ag-0.75Cu and In-48Sn solder joints, while the shear force increased with increasing shear speed at fixed shear height. Too high shear height could cause some undesirable effects on the test results such as unexpected high standard deviation values or shear tip sliding from the solder ball. The low shear height conditions were favorable for screening the type of brittle interfacial fractures or the degraded layers in the interfaces. The shear speed conditions were discussed with the stress analyses of the solder ball, and we cannot find any conspicuous finding which is related to optimum shear speed from the stress analyses.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.250-255
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• 2008

This study utilized a high speed lap-shear test to evaluate the mechanical behavior of Sn-37Pb/Cu and Sn-37Pb/Electroless Nickel immersion Gold under bump metallization solder joints under high speed loading and hence the drop reliability. The samples were aged for 120 h at different temperatures ($120^{\circ}C,\;150^{\circ}C,\;170^{\circ}C$) and afterward tested at different displacement rates (0.01 mm/s to 500 mm/s) to examine the effects of aging on the drop life reliability. The combination of the stress-strain graphs captured from the shear tests and identifying a fracture mode dominant in the samples for different strain rates leads us to conclude that the drop reliability of solder joints degrades as the aging temperature increases, possibly due to the role of the IMC layer. This study successfully demonstrates that the analysis based on a high speed lap-shear test could be critically used to evaluate the drop reliability of solder joints.

• Structural Engineering and Mechanics
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• 제78권4호
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• pp.413-423
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• 2021

Piers are the main lateral force-resisting members of high-speed railway (HSR) bridges used in China and are characterized by low axial load ratios, low longitudinal reinforcement ratios, low stirrup ratios, and high shear span ratios. It is well known that flexural, flexural-shear, and shear failures of piers may occur during an earthquake. In this study, a new shear strength model was developed to simulate the seismic failure of HSR solid piers accurately. First, low cyclic-loading test data of solid piers obtained in recent years were collected to set up a database for model verification. Second, based on the test database, the applicability of existing shear strength models was evaluated. Finally, a new shear strength model for HSR solid piers with round-ended cross-sections was derived based on the truss model and ultimate equilibrium theory. In comparison with existing models, it was demonstrated that the proposed model could be used to predict the shear strength of HSR piers more accurately.

• 마이크로전자및패키징학회지
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• 제15권4호
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• pp.65-70
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• 2008

본 연구에서는 BGA(Ball Grid Array) 솔더 접합부에 high impact가 가해졌을 경우 접합부의 기계적 특성에 대해서 연구하였다. 시편은 ENIG(Electroless Nickel Immersion Gold) 표면 처리된 FR-4 기판 위에 직경이 500 ${\mu}m$인 Sn-37Pb 솔더볼을 BGA 방식으로 배열하고 리플로우(Reflow)를 통하여 제작하였다. HTS(High Temperature Storage) 테스트를 위해, 시편을 일정한 온도의 $120^{\circ}C$에서 250시간 동안 시효처리(Aging)를 실시하였다. 시효처리 후, 각각의 시편은 고속 전단 시험기(Dage-4000HS)를 이용하여 속도 변수는 0.01, 0.1, 1, 3 m/s로 설정하여 고속전단 시험을 실시하였다. 전단시험 후, 솔더 접합 계면과 파면을 주사전자현미경(Scanning Electron Microscope, SEM)을 통하여 관찰하였다. 솔더 접합 계면에는 $Ni_3Sn_4$의 금속간 화합물이 성장하였으며, 시효처리 후, 솔더 접합 계면에 생성된 금속간 화합물의 두께가 증가하는 것을 관찰 할 수 있었다. 전단 시험 결과, 전단 속도가 빨라짐에 따라 전단 강도값은 증가하는 경향을 나타내었다. 솔더 접합부의 파단은 전단 속도와 시효처리 시간에 따라 다양한 파괴 모드로 진행됨을 알 수 있었다. 또한, 파괴 모드는 연성파괴 형상을 보이다가 전단속도가 증가함에 따라 취성 파괴 형상으로 변하는 것을 알 수 있었다.

• 대한금속재료학회지
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• 제49권8호
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• pp.635-641
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• 2011

The effect of high shear speed on shear force, shear energy and fracture surface was investigated for the solder joint of a $Sn-_{3.0}Ag-_{0.5}Cu$ ball. For both ENIG and OSP pads, the shear force increased with an increase in shearing speed to 0.3 m/s. However, for an ENEPIG pad, the shear force increased with an increase in shear speed to 0.6 m/s and kept almost constant afterward. The shear energy decreased with an increase in shearing speed for ENIG and OSP pads. For the ENEPIG pad, however, the shear energy almost remained constant in a shearing speed range 0.3-3.0 m/s. The fracture mode analysis revealed that the amount of brittle fracture for the ENIG and the OSP pads increased with shearing speed, and a complete brittle fracture appeared at 1.0 m/s for ENIG and 2.0 m/s for OSP. However, the ENEPIG pad showed only a ductile fracture until 0.25 m/s, and a full brittle fracture didn't occur up to 3.0 m/s. The fracture mode matched well with the shear energy. The results from the high speed shear test of SAC305 were similar to those of SAC105.

• 한국생산제조학회지
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• 제18권5호
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• pp.449-454
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• 2009

This paper presents an experimental study on the failure characteristics of SnAgCu lead-free solder balls. To estimate the effect of Ag, three types of SnAgCu balls are first prepared by varying the weight percent of Ag(1.0, 3.0, 4.0 wt%) and then analyzed by reliability tests such as thermal shock, high speed ball shear, and drop tests. Thermal shock test reveals that the higher the weight percent of Ag is, the longer the fatigue lift becomes. To the contrary, high speed ball-shear test and drop test show that the shear strength and the fracture toughness of solder balls are inversely proportional to the weight percent of Ag, respectively, Reasons for these observations will be further investigated In the future work.

• 대한금속재료학회지
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• 제49권3호
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• pp.237-242
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• 2011

The effect of shearing speed on the shear force and energy of Sn-0Ag-0.5Cu solder ball was investigated. Various UBM (under bump metallurgy)'s on Cu pads were used such as ENEPIG (Electroless Nickel, Electroless Palladium, Immersion Gold; Ni/Pd/Au), ENIG (Electroless Nickel, Immersion Gold; Ni/Au), OSP (Organic Solderability Preservative). To fabricate a shear test specimen, a solder ball, $300{\mu}m$ in diameter, was soldered on a pad of FR4 PCB (printed circuit board) by a reflow soldering machine at $245^{\circ}C$. The solder bump on the PCB was shear tested by changing the shearing speed from 0.01 m/s to 3.0 m/s. As experimental results, the shear force increased with a shearing speed of up to 0.6 m/s for the ENIG and the OSP pads, and up to 0 m/s for the ENEPIG pad. The shear energy increased with a shearing speed up to 0.3 m/s for the ENIG and the OSP pads, and up to 0.6 m/s for the ENEPIG pad. With a high shear speed of over 0 m/s, the ENEPIG showed a higher shear force and energy than those of the ENIG and OSP. The fracture surfaces of the shear tested specimens were analyzed, and the fracture modes were found to have closer relationship with the shear energy than the shear force.

• 마이크로전자및패키징학회지
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• 제17권3호
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• pp.1-9
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• 2010

본고에서는 마이크로 접합을 위한 솔더볼 또는 범프의 기계적 신뢰성 평가에 사용되는 전단시험의 표준화 규격에 대해 고찰해 보았다. 전단시험에서 중요한 실험 조건 중 하나인 전단속도는 low speed shear test와 high speed shear test로 구분 된다. 전단속도가 빨라질수록 솔더볼에 가해지는 충격이 커지기 때문에, 소성변형에 대한 저항성이 커지게 되고, 전단강도가 커지게 된다. 그리고 이 결과는 전산모사를 통하여 확인할 수 있다. 또 하나의 중요한 실험 조건으로 전단툴의 높이가 있다. 일반적으로 전단툴의 높이가 높을수록 전단강도 값은 낮아지게 되는데, 여러 국제 규격에서 제시한 솔더볼 높이의 25% 지점을 초과한 높이에서 전단시험을 진행했을 때에는 전단시험이 진행되는 접합 계면의 면적이 줄어들어 실험결과의 신뢰도가 떨어지게 된다. 이와 같이 전단속도와 툴의 높이 등의 실험조건들이 구체적으로 규격화 되어있지 않은 채 진행 되면, 실험 결과의 신뢰도가 떨어지고, 각 계에서 진행된 연구결과를 상호 비교하기가 어렵다. 따라서 효율성을 고려한 간접 시험법 개발 및 최신 패키징기술을 반영된 특성평가 시험법의 규격, 그리고 다양한 시험 표준화는 결국 마이크로 전자패키지의 고 신뢰성으로 나타날 것이라 생각된다.

• Journal of Welding and Joining
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• 제32권6호
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• pp.56-63
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• 2014

To develop and understand dissimilar metals joining of Stainless steel and Copper, ultra-high speed laser lap welding was studied using single mode fiber laser in this study. SUS304 and Cu have large differences in materials properties, and Cu and Fe have no intermetallic compounds by typical binary phase of Cu and Fe system. In this study, ultra-high speed lap welds of SUS304 and Cu dissimilar metals using single-mode fiber laser was generated, and weldability of the weld fusion zone was evaluated using a tensile shear test. To understand the phenomenon of tensile shear load, weld fusion zone of interface weld area and fracture parts after tensile shear test were observed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analysis system. And it was confirmed that Cu was easily melting and penetrating in the grain boundaries of SUS304 because of low melting temperature. And high thermal conductivity of copper occurred dissipate heat energy rapidly. These properties cause the solidification cracking in weld zone.