Controlling Bulk Cu6Sn5 Nucleation in Sn0.7Cu/Cu Joints with Al Micro-alloying

Xian, J.W.; Belyakov, S. A.; Gourlay, C.M.

doi:10.1007/s11664-015-4092-y

Cited by 20 publications

(20 citation statements)

References 18 publications

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“…Primary Cu6Sn5 has been reported to grow with various morphologies such as needles [10][11][12], hollow rods [11,13], X-shapes [9,14,15], Y-shapes [8,9], H-and M-shapes [16,17] and as dendrites [6,18]. Since many of these studies have been based on arbitrary 2D cross sections, it is not clear how many of these morphologies are separate growth forms in 3D.…”

Section: Introductionmentioning

confidence: 99%

“…The growth direction of the rod-like Cu6Sn5 is reported to be [0001] and the growth facets are usually {11 ̅ 00}-type Cu6Sn5 planes [15,16,19,20]. The crystallographic directions and facets of the other growth forms are not known.…”

Section: Introductionmentioning

confidence: 99%

“…The crystallographic directions and facets of the other growth forms are not known. Although markedly different primary Cu6Sn5 morphologies have been observed [8][9][10][11][13][14][15][16][17], there has been little work on the transitions between these growth forms nor on the mechanisms responsible for the range of Cu6Sn5 morphologies.…”

Section: Introductionmentioning

confidence: 99%

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Cu6Sn5 crystal growth mechanisms during solidification of electronic interconnections

et al. 2017

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The growth mechanisms of primary Cu6Sn5 are studied in Sn-Cu alloys and solder joints by combining EBSD, FIB-tomography and synchrotron radiography. With increasing cooling rate and Cu content, Cu6Sn5 crystals developed from faceted hexagonal rods to grooved rods, in-plane branched faceted crystals and, finally, to nonfaceted dendrites. This range of growth morphologies has been rationalised into a kinetic microstructure map. Cu6Sn5 hexagonal rods grew along [0001] bounded by {101 ̅ 0} facets and Cu6Sn5 dendrites branched along <405> in the {101 ̅ 0} planes. The faceted to nonfaceted transition indicates a kinetic interface roughening transition and a gradual change in mechanism from lateral growth governed by anisotropic attachment kinetics to continuous growth governed by diffusion and curvature. Finally, it is shown that the full range of Cu6Sn5 morphologies that grew for different composition and cooling rate combinations in bulk alloys can be engineered to grow in solder joints made with a single composition (Sn-0.7wt%Cu/Cu) by altering the peak temperature and the cooling rate.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Cu6Sn5 crystal growth mechanisms during solidification of electronic interconnections

et al. 2017

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“…[52] indicate that large intermetallics, which includes the primary and interfacial intermetallic compound layer, could promote crack initiation in solder joints. Xian et al [54] report that primary Cu6Sn5 formation in the bulk solder is shown to be affected by the increasing Cu content of the liquid due to the Cu dissolution, the change in phase equilibria and the degree of undercooling for β-Sn.…”

Section: Fabrication Methods Of Reinforced Soldersmentioning

confidence: 99%

Microstructure Formation in Reinforced Sn-Cu Lead-free Solder Alloys

Salleh¹,

Anuar²

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Electronics manufacturers are pushing the limits in reducing the physical size of circuitry while simultaneously increasing the number of transistors to satisfy Moore's Law [1]. This includes investing in new materials, and configuring new ways to manufacture complex 3D (three dimensional) electronic packaging [1]. One key requirement of new materials and techniques is ensuring the high reliability of the resultant products in various challenging operating environments including thermal and mechanical extremes [2][3][4]. A viable method to enhance the properties and performance of a solder joint is by incorporation of reinforcement particles to the solder matrix, either by intrinsic or extrinsic methods. In this thesis a series of Sn-Cu Pb-free solder alloys with extrinsic or intrinsic phase reinforcement were manufactured and the microstructure and soldering behavior were investigated in detail.Additions of extrinsic reinforcement in the form of nano-sized ceramic material were made using a microwave sintering powder metallurgy (PM) method, which is a viable method to improve the mechanical and thermal properties of Pb-free solder materials. In addition, the advanced processing routes ensures a homogenous distributions of reinforcement particles is present. To investigate the performance of the reinforced bulk solders including thermal and mechanical properties and relate this to the microstructure, samples were investigated using techniques such as synchrotron micro-XRF, HRTEM, SEM, XPS, dilatometery, DSC and shear and microhardness testing. A hypothesis of how reinforcement improves solder properties is developed and discussed. Synchrotron X-ray radiography imaging (SXRI) was used to analyse the development of microstructure and the complex interactions occurring in the solders. Based on the properties of the fabricated solder, the microwave sintering PM route was discussed as a promising method for the reinforcement of Pb-free solders.The initial formation of interfacial IMC products was studied in Sn-Cu based solder alloys by in situ experiment techniques such as SXRI and UHV-TEM. The results provide direct experimental evidence of real-time initial Cu6Sn5 layer development during soldering and also the stress creation and release events that arise due to the polymorphic transformations of the Cu6Sn5 phase and the associated volumetric change.ii In addition, the nucleation and growth behavior of primary intermetallics which can be considered an intrinsic reinforcing material in solder joints was studied. Here, the nucleation and growth behavior of primary Cu6Sn5 and β-Sn crystals in some of the most commonly used solder alloys including Sn-0.7Cu and Sn-3.0Ag-0.5Cu is explained. This also includes the effects of Ni additions for refining primary Cu6Sn5 in Sn-Cu solder joints. Using SXRI, observations were made during solder joint solidification, which is difficult using conventional methods. The initial nucleation and solidification kinetics of primary Cu6Sn5 crystals were discussed.The growth of pri...

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“…by crystal growth prior to Sn nucleation) such as the large Ag3Sn plates and Cu6Sn5 rods in BGA joints [53][54][55]. Under BGA soldering conditions the IMCs typically grow as faceted crystals [54,56].…”

Section: Cte Mismatch At Sn-imc Interfacesmentioning

confidence: 99%

Anisotropic thermal expansion of Ni 3 Sn 4 , Ag 3 Sn, Cu 3 Sn, Cu 6 Sn 5 and βSn

et al. 2017

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The directional coefficient of thermal expansion (CTE) of intermetallics in electronic interconnections is a key thermophysical property that is required for microstructurelevel modelling of solder joint reliability. Here, CTE ellipsoids are measured for key solder intermetallics using synchrotron x-ray diffraction (XRD). The role of the crystal structure used for refinement on the CTE shape and temperature dependence is investigated. The results are used to discuss the Sn-IMC orientation relationships (ORs) that minimise the in-plane CTE mismatch on IMC growth facets, which are measured with electron backscatter diffraction (EBSD) in solder joints on Cu and Ni substrates. The CTE mismatch in fully-intermetallic joints is discussed, and the relationship between the directional CTE of monoclinic and hexagonal polymorphs of Cu6Sn5 is explored.

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Controlling Bulk Cu6Sn5 Nucleation in Sn0.7Cu/Cu Joints with Al Micro-alloying

Cited by 20 publications

References 18 publications

Cu6Sn5 crystal growth mechanisms during solidification of electronic interconnections

Cu6Sn5 crystal growth mechanisms during solidification of electronic interconnections

Microstructure Formation in Reinforced Sn-Cu Lead-free Solder Alloys

Anisotropic thermal expansion of Ni 3 Sn 4 , Ag 3 Sn, Cu 3 Sn, Cu 6 Sn 5 and βSn

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