Reactions of solid copper with pure liquid tin and liquid tin saturated with copper

Hayashi, Akitoshi; Kao, C. R.; Chang, Ya-chun

doi:10.1016/s1359-6462(97)00129-2

Cited by 67 publications

(41 citation statements)

References 8 publications

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“…Lord and Umantsev identified the dissolution of the grain boundaries as the primary reason for the formation of undulations of the IMC layer in the form of scallops and confirmed the suggestion made in Ref. 5. Quantitative analysis of the growth rates of a continuous IMC layer showed that the early stages are controlled by the kinetics of dissolution of the copper, with the kinetic coefficient of dissolution of copper in pure tin being ϳ1 mm/ s mfr.…”

Section: A Experimentssupporting

confidence: 79%

“…However, observations of the intermetallic growth in the solid-Cu͑Ni͒/liquid-Sn system ͑above the melting point of the solder͒ instead of a smooth layer always show rough, strongly undulated compound layers with scallops of the intermetallic phase. [5][6][7] With time scallops grow larger but fewer, indicating that the coarsening process takes place. 6,7 The problem of IMC layer growth has many challenges, the reasons for roughness and coarsening, to name only a few.…”

Section: A Experimentsmentioning

confidence: 99%

“…To describe this process Kim et al 6,8 suggested a two-flux nonconservative Ostwald ripening model based on the assumption of rapid dissolution of Cu into the liquid solder. Hayashi et al 5 suggested the fast dissolution of Cu 6 Sn 5 along the grain boundary as the reason for scallopedge appearance. However, the suggestion of the predominant dissolution in the system remained unsubstantiated.…”

Section: A Experimentsmentioning

confidence: 99%

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Modeling of intermediate phase growth

Umantsev

2007

Journal of Applied Physics

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We introduced a continuum method for modeling of intermediate phase growth and numerically simulated three common experimental situations relevant to the physical metallurgy of soldering: growth of intermetallic compound layer from an unlimited amount of liquid and solid solders and growth of the compound from limited amounts of liquid solder. We found qualitative agreements with the experimental regimes of growth in all cases. For instance, the layer expands in both directions with respect to the base line when it grows from solid solder, and grows into the copper phase when the solder is molten. The quantitative agreement with the sharp-interface approximation was also achieved in these cases. In the cases of limited amounts of liquid solder we found the point of turnaround when the compound/solder boundary changed the direction of its motion. Although such behavior had been previously observed experimentally, the simulations revealed important information: the turnaround occurs approximately at the time of complete saturation of solder with copper. This result allows us to conclude that coarsening of the intermetallic compound structure starts only after the solder is practically saturated with copper. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2424530͔ I. BACKGROUND A. ExperimentPhysical metallurgy of soldering presents many interesting problems: transformations in the solder, transformations in the contacts, and mechanical and electrical properties of the joints. 1 One of the problems that is critical for soldering industry is the formation and growth of an intermediate phase between the solder and the contact. The occurrence of an intermediate phase near 50 at. % of Sn in the Cu-Sn system at temperatures below 415°C was observed in 1904. 2 This transformation was found to be associated with significant amount of heat of formation ͑first-kind transition͒, but details regarding the nature of the phase mostly have been unknown at the time. Later on this phase ͑ phase͒ was identified as an intermetallic compound ͑IMC͒ Cu 6 Sn 5 . 3 The compound Cu 6 Sn 5 undergoes another phase transformation at approximately 189°C, which was identified as a secondkind order-disorder transition ͑ ↔ Ј͒ associated with the formation of a long-period superlattice.The compound grows in the form of a layer with morphology strongly dependent on the temperature of soldering: Onishi and Fujibuchi 4 showed that the growth of IMCs from solid-state Cu-Sn diffusion couples results in a relatively planar layer of IMC. However, observations of the intermetallic growth in the solid-Cu͑Ni͒/liquid-Sn system ͑above the melting point of the solder͒ instead of a smooth layer always show rough, strongly undulated compound layers with scallops of the intermetallic phase. [5][6][7] With time scallops grow larger but fewer, indicating that the coarsening process takes place. 6,7 The problem of IMC layer growth has many challenges, the reasons for roughness and coarsening, to name only a few. To describe this process Kim et al. 6,8 suggeste...

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Section: A Experimentssupporting

confidence: 79%

Section: A Experimentsmentioning

confidence: 99%

Section: A Experimentsmentioning

confidence: 99%

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Modeling of intermediate phase growth

Umantsev

2007

Journal of Applied Physics

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“…In the tin/copper and tin-rich-alloys/copper joint systems, the intermetallic Cu 6 Sn 5 (h'-phase) formed immediately upon contact of the liquid solder with the copper substrate [7,8]. Then, the intermetallic compound grew rapidly [9,10]. The interface after thermal aging was found to be very different compared to the initial observations immediately following soldering, as shown in Figure 2, in the micrographs of the Cu/Solder interface at 150 o C for 500 hours.…”

Section: Joint Interface Characterizationmentioning

confidence: 99%

Effect of thermal aging on the interfacial reactions of tin-based solder alloys and copper substrates and kinetics of formation and growth of intermetallic compounds

Madeni

Liu

2011

Soldag. insp.

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“…The interfacial reactions between solders and UBMs as well as between solders and surface finishes had been studied quite intensively in the past [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Effects of the gold thickness of the surface finish on the interfacial reactions in flip-chip solder joints

Lin

Luo

Lin

et al. 2004

Journal of Elec Materi

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The effects of Au thickness on the flip chip solder joints with the Cu/Ni/Al UBM on one end and the Au/Ni surface finish on another was studied. Two different thicknesses, 0.1µm and 0.65 µm, were used for the surface finish. After assembly, the joints were subjected to thermal aging at 150. The difference in Au thickness had a strong effect on the consumption rate of the Ni layer in UBM as well as on the failure mode of the solder joints.When the Au layer was thin (0.1 µm), the dissolved Cu from the Cu/Ni UBM was able to inhibit the formation of AuSn 4 . When the Au layer was thick (0.65 µm), the dissolved Cu was not able to inhibit the formation of AuSn 4 . These AuSn 4 enhanced the Ni consumption rate of the UBM. The presence of large amount of AuSn 4 inside the solder also weakened the solder due to the Au-embrittlement effect. In view of these observations, the gold thickness on Au/Ni surface finish must be kept to the minimum controlled in order to prolong the service life of the flip chip packages.

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Reactions of solid copper with pure liquid tin and liquid tin saturated with copper

Cited by 67 publications

References 8 publications

Modeling of intermediate phase growth

Modeling of intermediate phase growth

Effect of thermal aging on the interfacial reactions of tin-based solder alloys and copper substrates and kinetics of formation and growth of intermetallic compounds

Effects of the gold thickness of the surface finish on the interfacial reactions in flip-chip solder joints

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