Growth evolution and formation mechanism of η′-Cu6Sn5 whiskers on η-Cu6Sn5 intermetallics during room-temperature ageing

Zhang, Z.H.; Wei, Caiyun; Han, Jiajia; Cao, Huijun; Chen, H.T.; Li, M.Y.

doi:10.1016/j.actamat.2019.11.032

Cited by 22 publications

(7 citation statements)

References 43 publications

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“…Because small joints have elevated heating/cooling rates, the polymorphic transition of η ↔η may be kinetically retarded owing to the insufficient transition time. It is concerning that this retarded polymorphic transition may cause a transition stress that continuously damages the Cu 6 Sn 5 IMC interconnection [13,14]. Although some researchers have begun to explore the effect of the Cu 6 Sn 5 polymorphic transition on the interconnect reliability [14][15][16], the intrinsic damage mechanism has seldom been reported during multiple reflow processes.…”

Section: Methodsmentioning

confidence: 99%

“…It is concerning that this retarded polymorphic transition may cause a transition stress that continuously damages the Cu 6 Sn 5 IMC interconnection [13,14]. Although some researchers have begun to explore the effect of the Cu 6 Sn 5 polymorphic transition on the interconnect reliability [14][15][16], the intrinsic damage mechanism has seldom been reported during multiple reflow processes. On 7 October, 2019, Samsung Electronics announced that it had developed the industry's first 12-layer-3D-IC, and that the IMC interconnections in such 3D IC may experience over 10 reflow cycles.…”

Section: Methodsmentioning

confidence: 99%

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Damage Mechanism of Cu6Sn5 Intermetallics Due to Cyclic Polymorphic Transitions

et al. 2019

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The formation of high-melting-point Cu6Sn5 interconnections is crucial to overcome the collapse of Sn-based micro-bumps and to produce reliable intermetallic interconnections in three-dimensional (3D) packages. However, because of multiple reflows in 3D package manufacturing, Cu6Sn5 interconnections will experience cyclic polymorphic transitions in the solid state. The repeated and abrupt changes in the Cu6Sn5 lattice due to the cyclic polymorphic transitions can cause extreme strain oscillations, producing damage at the surface and in the interior of the Cu6Sn5 matrix. Moreover, because of the polymorphic transition-induced grain splitting and superstructure phase formation, the reliability of Cu6Sn5 interconnections will thus face great challenges in 3D packages. In addition, the Cu6Sn5 polymorphic transition is structure-dependent, and the η′↔η polymorphic transition will occur at the surface while the η′↔ηs↔η polymorphic transition will occur in the deep matrix. This study can provide in-depth understanding of the structural evolution and damage mechanism of Cu6Sn5 interconnections in real 3D package manufacturing.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Damage Mechanism of Cu6Sn5 Intermetallics Due to Cyclic Polymorphic Transitions

et al. 2019

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“…However, the Cu-Sn IMC interlayers in Cu interconnects formed by this Sn/Cu interfacial reaction are brittle in nature [2]. Moreover, a relatively long soldering time (up to several hours) is necessary for complete removal of the Sn, which may lead to extra thermal stress in the bonded components and affect the reliability of the packaging system [3].…”

Section: Introductionmentioning

confidence: 99%

Diffusion reaction-induced microstructure and strength evolution of Cu joints bonded with Sn-based solder containing Ni-foam

Huang

Xiao

et al. 2020

Materials Letters

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Sn based composite solder, reinforced with low porosity Ni-foam, was used to fabricate high melting point Cu interconnects by soldering at 260 °C. The effects of soldering time on the microstructure and mechanical properties of the joints were investigated. The Sn matrix was rapidly consumed by the formation of (Cu,Ni) 6 Sn 5 and (Ni,Cu) 3 Sn 4 phases in under 10 min. With increasing soldering time, the (Cu,Ni) 6 Sn 5 phase was largely transformed into the (Ni,Cu) 3 Sn 4 phase, accompanied by the refinement in the size of the phases. The average shear strength of the joint soldered for 60 min was up to 76.9 MPa, which is significantly stronger than commonly reported for Cu joints soldered with Sn based alloys.

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“…Because small joints have elevated heating/cooling rates, the polymorphic transition of η′↔η may be kinetically retarded owing to the insufficient transition time. It is concerning that this retarded polymorphic transition may cause a transition stress that continuously damages the Cu6Sn5 IMC interconnection [13,14]. Although some researches have begun to explore the effect of the Cu6Sn5 polymorphic transition on the interconnect reliability [14][15][16], the intrinsic damage mechanism has seldom been reported during multiple reflow processes.…”

Section: Introductionmentioning

confidence: 99%

“…It is concerning that this retarded polymorphic transition may cause a transition stress that continuously damages the Cu6Sn5 IMC interconnection [13,14]. Although some researches have begun to explore the effect of the Cu6Sn5 polymorphic transition on the interconnect reliability [14][15][16], the intrinsic damage mechanism has seldom been reported during multiple reflow processes. In October 7th, 2019, Samsung Electronics announced that it has developed an industry's first 12-layer-3D-IC, and the IMC interconnections in such 3D IC may experience over reflow cycles; because the number of stacking layers will never be an end, a 50-layer 3D IC may be fabricated in the near future, and the IMC interconnections in such 3D IC may experience 50 or even more reflow cycles.…”

Section: Introductionmentioning

confidence: 99%

Damage Mechanism of Cu<sub>6</sub>Sn<sub>5</sub> Intermetallics Due to Cyclic Polymorphic Transitions

Zhang¹,

Wei²,

Cao

et al. 2019

Preprint

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The formation of high-melting-point Cu6Sn5 interconnections is crucial to overcome the collapse of Sn-based micro-bumps and produce reliable intermetallic interconnections in three-dimensional (3D) package. However, because of the multiple reflows in 3D package manufacturing, Cu6Sn5 interconnections will experience the cyclic polymorphic transitions in the solid state. The repeated and abrupt change in the Cu6Sn5 lattice due to the cyclic polymorphic transitions can cause extreme strain oscillations, producing damages at the surface and in the interior of the Cu6Sn5 matrix. Moreover, because of the polymorphic-transition-induced grain splitting and superstructure phase formation, the reliability of Cu6Sn5 interconnections will thus face great challenges in 3D package. In addition, the Cu6Sn5 polymorphic transition is structure-dependent, and the η′↔η polymorphic transition will occur at the surface while the η′↔ηs↔η polymorphic transition will occur in the deep matrix. Our results can provide in-depth understandings of structural evolution and damage mechanism of Cu6Sn5 interconnections in real 3D package manufacturing.

show abstract

Growth evolution and formation mechanism of η′-Cu6Sn5 whiskers on η-Cu6Sn5 intermetallics during room-temperature ageing

Cited by 22 publications

References 43 publications

Damage Mechanism of Cu6Sn5 Intermetallics Due to Cyclic Polymorphic Transitions

Damage Mechanism of Cu6Sn5 Intermetallics Due to Cyclic Polymorphic Transitions

Diffusion reaction-induced microstructure and strength evolution of Cu joints bonded with Sn-based solder containing Ni-foam

Damage Mechanism of Cu<sub>6</sub>Sn<sub>5</sub> Intermetallics Due to Cyclic Polymorphic Transitions

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