Metastable eutectic in Pb-free joints between Sn–3.5Ag and Ni-based substrates

Belyakov, S. A.; Gourlay, C.M.

doi:10.1016/j.matlet.2015.02.073

Cited by 17 publications

(25 citation statements)

References 23 publications

(17 reference statements)

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“…Shallow etching ( Figure 6C,D) shows that solidification occurred by primary Sn dendrite growth followed by eutectic reactions. With higher magnification analytical SEM, we have found a surprising result: the eutectic is Sn-Ag3Sn-NiSn4 and not the Sn-Ag3Sn-Ni3Sn4 expected of equilibrium solidification [47]. That is to say, metastable NiSn4 forms during the solidification of Sn-3.5Ag/Ni joints.…”

Section: Tin Grain Structure In Solder Balls On Common Substratesmentioning

confidence: 71%

“…Note that, in Figure 6, the substrate is 99.9% pure Ni to make the point that metastable NiSn4 forms when only Sn, Ag and Ni are present. Further details of metastable NiSn4 in Sn-3.5Ag/Ni and more complex Ni(P)/Au/Sn3.5Ag joints including phase identification by combining EBSD and EDX are given in our past work [47,48]. We have also shown that a binary metastable SnNiSn4 eutectic grows over a wide range of solidification conditions in the Sn-Ni system which is discussed in refs [48,49].…”

Section: Tin Grain Structure In Solder Balls On Common Substratesmentioning

confidence: 74%

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Nucleation and Growth of Tin in Pb-Free Solder Joints

Gourlay

Belyakov

et al. 2015

JOM

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The solidification of Pb-free solder joints is overviewed with a focus on the formation of the Sn grain structure and grain orientations. Three solders commonly used in electronics manufacturing, Sn-3Ag-0.5Cu, Sn-3.5Ag and Sn-0.7Cu-0.05Ni, are used as case studies to demonstrate that growth competition between primary dendrites and eutectic fronts during growth in undercooled melts is important in Pb-free solders, and that a metastable eutectic containing NiSn4 forms in Sn-3.5Ag/Ni joints. Additionally, it is shown that the substrate (metallization) has a strong influence on the nucleation and growth of tin. We identify Co, Pd and Pt substrates as having potential to control solidification and microstructure formation. In the case of Pd and Pt substrates, Sn is shown to nucleate on the PtSn4 or PdSn4 IMC reaction layer at relatively low undercooling of ~4K, even for small solder ball diameters down to <200 m. IntroductionThe transition to Pb-free electronic interconnections has been underway for more than a decade and despite the exemptions to the RoHS Directive there are few applications where Pb-free solders are not being used. At the same time, electronic packaging technologies have been advancing and there is an ongoing need to develop next-generation Pb-free solders and substrates that are better suited to smaller joints that can operate at higher temperature and that are more reliable.The most commonly used Pb-free solders are hypoeutectic or near-eutectic compositions from the Sn-Ag-Cu (SAC), Sn-Ag or Sn-Cu-Ni alloy systems. These compositions solidify with significant differences to the near-eutectic Sn-Pb solders used previously. For example, where the Sn-37Pb

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Section: Tin Grain Structure In Solder Balls On Common Substratesmentioning

confidence: 71%

Section: Tin Grain Structure In Solder Balls On Common Substratesmentioning

confidence: 74%

Nucleation and Growth of Tin in Pb-Free Solder Joints

Gourlay

Belyakov

et al. 2015

JOM

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“…Accordingly, most fillers should be lead free. As lead-free fillers, tin-based alloys have been developed (Lu et al 2014;Kotadia et al 2014;Yu et al 2014;Belyakov and Gourlay 2015). However, these alloys have low melting points, so they remelt at relatively low temperatures (above their melting point), thereby breaking the joints they form.…”

Section: Introductionmentioning

confidence: 99%

Metal–metal bonding using silver/copper nanoparticles

et al. 2015

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A method for producing nanoparticles composed of silver and copper and a metal-metal bonding technique using the silver/copper nanoparticles are proposed. The method consists of three steps. First, copper oxide nanoparticles are produced by mixing Cu(NO 3 ) 2 aqueous solution and NaOH aqueous solution. Second, copper metal nanoparticles are fabricated by reducing the copper oxide nanoparticles with hydrazine in the presence of poly(vinylpyrrolidone) (PVP). Third, silver/copper nanoparticles are synthesized by reducing Ag ? ions with hydrazine in the presence of the copper metal nanoparticles. Initial concentrations in the final silver/copper particle colloid, composed of 0.0075 M Cu 2? , 0.0025 M Ag ? , 1.0 g/L PVP, and 0.6 M hydrazine, produced silver/copper nanoparticles with an average size of 49 nm and a crystal size of 16.8 nm. Discs of copper metal were successfully bonded by the silver/copper nanoparticles under annealing at 400°C and pressurizing at 1.2 MPa for 5 min in not only hydrogen gas but also nitrogen gas. The shear force required to separate the bonded discs was 22.3 MPa for the hydrogen gas annealing and 14.9 MPa for the nitrogen gas annealing (namely, 66.8 % of that for hydrogen gas annealing).

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“…eutectic as expected from equilibrium solidification [14], i.e. a metastable NiSn4 forms during solidification of Sn-3.5Ag/Ni solder joints.…”

Section: A B Cmentioning

confidence: 72%

“…Further details of metastable NiSn4 in Sn-3.5Ag/Ni and more complex Ni(P)/Au/Sn3.5Ag joints including phase identification by combining EBSD and EDX are given in our past work. [14][15][16][17]. Fig.…”

Section: A B Cmentioning

confidence: 97%

Influence of Bi additions on the distinct βSn grain structure of Sn-0.7Cu-0.05Ni-xBi (x = 0–4wt%)

Belyakov

Nishimura

Sweatman

et al. 2016

2016 International Conference on Electronics Packaging (ICEP)

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Abstract-Effects of Bi addition to the Ag-containing leadfree solders have been the focus of a considerable amount of past investigations, however, influence of Bi on Sn-Cu-Ni system has not been studied so extensively. In the present study we aimed to reveal the influence of Bi on microstructure formation of Sn-0.7Cu-0.05Ni/Cu solder joints both in the bulk and at the interface. It is shown that (i) Sn-0.7Cu-0.05Ni solidifies to produce a markedly different grain structure to Ag-containing lead-free alloys; (ii) Bi additions to Sn-0.7Cu-0.05Ni had no discernible effect neither on the βSn grain structure nor on (Cu,Ni)6Sn5 interfacial intermetallic layers or primary intermetallic crystals in solder joints.

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Metastable eutectic in Pb-free joints between Sn–3.5Ag and Ni-based substrates

Cited by 17 publications

References 23 publications

Nucleation and Growth of Tin in Pb-Free Solder Joints

Nucleation and Growth of Tin in Pb-Free Solder Joints

Metal–metal bonding using silver/copper nanoparticles

Influence of Bi additions on the distinct βSn grain structure of Sn-0.7Cu-0.05Ni-xBi (x = 0–4wt%)

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