Direct observation of stray crystal formation in unidirectional solidification of Sn–Bi alloy by X-ray imaging

Yasuda, Hideyuki; Ohnaka, Itsuo; Kawasaki, K.; Sugiyama, A.; Ohmichi, Tetsutaro; Iwane, Jun; Umetani, Keiji

doi:10.1016/j.jcrysgro.2003.09.052

Cited by 196 publications

(103 citation statements)

References 13 publications

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“…In addition, the solute enrichment of mush melt could cause local remelting of the Al-Si eutectic, with potential detachment of fragments from the fine dendrite network, as documented in several previous studies. [25][26][27]34] …”

Section: Resultsmentioning

confidence: 99%

“…Over the last decade, an increasing number of real-time X-ray imaging studies of solidification microstructures and phenomena in real metals have been reported, addressing a broad variety of topics such as dendritic growth, [20][21][22][23] coarsening, [24] morphological transitions, [23] dendrite fragmentation, [25][26][27] solute diffusion and convection, [22,28] and momentum transfer relations in eutectics [29] and monotectics. [30] Most of these, and other recent in-situ studies, have been carried out with high-brilliance synchrotron radiation, where X-ray absorption-and near-field phase contrast is combined to bring about 2-D or 3D time-resolved data.…”

Section: Introductionmentioning

confidence: 99%

“…[30] Most of these, and other recent in-situ studies, have been carried out with high-brilliance synchrotron radiation, where X-ray absorption-and near-field phase contrast is combined to bring about 2-D or 3D time-resolved data. [20][21][22][23][24][25][26][27]29,30] …”

Section: Introductionmentioning

confidence: 99%

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X-Ray Videomicroscopy Studies of Eutectic Al-Si Solidification in Al-Si-Cu

Mathiesen

Arnberg

et al. 2010

Metall Mater Trans A

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Al-Si eutectic growth has been studied in-situ for the first time using X-ray video microscopy during directional solidification (DS) in unmodified and Sr-modified Al-Si-Cu alloys. In the unmodified alloys, Si is found to grow predominantly with needle-like tip morphologies, leading a highly irregular progressing eutectic interface with subsequent nucleation and growth of Al from the Si surfaces. In the Sr-modified alloys, the eutectic reaction is strongly suppressed, occurring with low nucleation frequency at undercoolings in the range 10 K to 18 K. In order to transport Cu rejected at the eutectic front back into the melt, the modified eutectic colonies attain meso-scale interface perturbations that eventually evolve into equiaxed compositestructure cells. The eutectic front also attains short-range microscale interface perturbations consistent with the characteristics of a fibrous Si growth. Evidence was found in support of Si nucleation occurring on potent particles suspended in the melt. Yet, both with Sr-modified and unmodified alloys, Si precipitation alone was not sufficient to facilitate the eutectic reaction, which apparently required additional undercooling for Al to form at the Si-particle interfaces.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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X-Ray Videomicroscopy Studies of Eutectic Al-Si Solidification in Al-Si-Cu

Mathiesen

Arnberg

et al. 2010

Metall Mater Trans A

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“…The real time observation experiments were performed at BL20XU beamline in the SPring-8 synchrotron using an in-situ synchrotron X-ray real time solidification observation setup developed in previous research [39][40][41][42]. The parameters were chosen to allow a high degree of coherence, absorption contrast and phase contrast enabling boundaries in the sample to be …”

Section: Synchrotron X-ray Radiography Imagingmentioning

confidence: 99%

Suppression of Cu 6 Sn 5 in TiO 2 reinforced solder joints after multiple reflow cycles

et al. 2016

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In the current generation of 3D electronic packaging, multiple reflows are often required during soldering. In addition, electronic packages may be subjected to additional solder rework or other heating processes. This paper investigates the effects of multiple reflow cycles on TiO2 reinforced Sn-0.7Cu solder fabricated by a powder metallurgy microwave sintering technique.Compared to TiO2-free equivalents, a relative suppression of the Cu6Sn5 phase, both as primary crystals and as an interfacial layer was observed. The likely mechanism relates to the TiO2 nanoparticles promoting nucleation and decreasing the amount of time that liquid is in contact with the interfacial layer. The TiO2 particles appear to stabilise the interfacial Cu6Sn5 layer and result in a more planar morphology. The suppression of Cu6Sn5 results in TiO2 reinforced solder joints having a higher shear strength after multiple reflow cycles compared to Sn-0.7Cu solder joints. IntroductionSolder alloys play a crucial role in determining performance and reliability in the assembly and interconnection of electronic products and have electrical, thermal and mechanical functions [1,2]. The relative importance of solder alloy properties has increased due to continued miniaturization of microelectronic circuitry and the use of finer pitch interconnects. Higher functional densities in printed circuit boards (PCB) have been made possible by surface mount technology (SMT) using reflow soldering, often with multiple reflow cycles. Other heating cycles can be present in manufacturing such as additional solder rework [3]. One challenge associated with current generation Pb-free solder alloys is that during multiple thermal cycles, the joint strength may degrade due to the rapid growth of the interfacial layer of intermetallic compounds [4][5][6][7][8][9][10][11][12]. In a typical Pb-free solder joint, Cu6Sn5, which may form either as primary crystals or an interfacial layer during soldering can play a determining role in solder joint strength. There is evidence that by suppressing the Cu6Sn5 interfacial layer, solder joint properties could be improved [13][14][15][16][17] and as such there are benefits associated with controlling the growth of this layer during multiple reflows.It has recently been reported that additions of reinforcement to a variety of solder matrices, with compounds including silicon carbide (SiC) [18][19][20], nickel oxide (NiO) [21], alumina (Al2O3) [22][23][24], zirconia (ZrO2) [25][26][27][28], titanium oxide (TiO2) [29][30][31][32][33][34] and silicon nitride (Si3N4) [35,36] result in suppression of the growth of the interfacial layer during soldering [37]. In our recent study [38], we developed a method of fabricating a reinforced solder using a powder metallurgy microwave sintering method that results in a homogeneous distribution of TiO2 in the solder material and an improvement in the bulk solder material thermal and mechanical properties. However, properties related to the solder joint strength after multiple reflows of t...

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“…Sn-Bi alloys, as a kind of representative binary eutectic alloy and lead-free solder, have important research and application values [20][21][22]. In prior works, anomalous temperature dependence of internal friction [13], electrical resistivity [15], and viscosity [14] of liquid Sn-Bi alloys have suggested that the structural relaxation occurred.…”

Section: Introductionmentioning

confidence: 99%

Change of solidification behaviors in the superheating Sn-40wt.%Bi alloy from the viewpoint of the relaxation of properties

Ding¹,

Li²,

Chen³

2021

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The effects of melt overheating treatment on solidification of Sn-Bi alloys are studied from the viewpoint of the relaxation of properties. The results reveal that the change trends of cooling rate, undercooling degree of the primary and eutectic nucleation and maximum solidification rates of primary phase of melts not undergoing the relaxation are contrary to those of melts undergoing the relaxation. However, the change of these parameters could not explain the change on the microstructures. The present paper suggests the increasing of the apparent primary undercooling during solidification can be used to describe the refinement of primary phase after melts undergoing the relaxation. Our study may open new possibilities for the control of solidification process, which governs the microstructure, mechanical and physical properties of solids.K e y w o r d s : structural relaxation, alloys, crystal growth

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Direct observation of stray crystal formation in unidirectional solidification of Sn–Bi alloy by X-ray imaging

Cited by 196 publications

References 13 publications

X-Ray Videomicroscopy Studies of Eutectic Al-Si Solidification in Al-Si-Cu

X-Ray Videomicroscopy Studies of Eutectic Al-Si Solidification in Al-Si-Cu

Suppression of Cu 6 Sn 5 in TiO 2 reinforced solder joints after multiple reflow cycles

Change of solidification behaviors in the superheating Sn-40wt.%Bi alloy from the viewpoint of the relaxation of properties

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