The Crystal Orientation of β-Sn Grains in Sn-Ag and Sn-Cu Solders Affected by Their Interfacial Reactions with Cu and Ni(P) Under Bump Metallurgy

Seo, Sun-Kyoung; Kang, Sung K.; Cho, Moon Gi; Shih, Da‐Yuan; Lee, Hyuck Mo

doi:10.1007/s11664-009-0902-4

Cited by 58 publications

(23 citation statements)

References 28 publications

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“…Additionally, there are more Sn grains near the substrate and a decreasing number of grains further away from the substrate in Figure 5A, which is indicative of grain selection by competitive growth away from the reaction layer, reminiscent of the growth of a columnar zone out of a chill zone near the wall of a casting [34]. Similar microstructures were reported in Sn-Cu/Cu joints by Seo et al [44]. Note that there are no "long plates" in Figure 5A such as those in freestanding Sn-0.7Cu-0.05Ni (e.g.…”

Section: Tin Grain Structure In Solder Balls On Common Substratessupporting

confidence: 78%

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 Substratessupporting

confidence: 78%

Nucleation and Growth of Tin in Pb-Free Solder Joints

Gourlay

Belyakov

et al. 2015

JOM

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“…Of these, ternary SnAg-Cu solder alloys, with near eutectic compositions and melting temperatures of around 217°C, have been regarded as possible replacements for the traditional Sn-Pb solder used in the electronic packaging industry [9,10]. However, minimizing the excessive growth behavior of the intermetallic compound (IMC) layers at their interface with the mechanical properties of the solder joint reduces the reliability and lifespan of the electronic packaging systems [11]. The formation of coarse primary dendrite-shaped b-Sn grains in the Sn-Ag-Cu solder also retards the resistance to thermal-mechanical fatigue [12].…”

Section: Introductionmentioning

confidence: 99%

Influence of cerium oxide (CeO2) nanoparticles on the microstructure and hardness of tin–silver–copper (Sn–Ag–Cu) solders on silver (Ag) surface-finished copper (Cu) substrates

Fouzder

Chan

Chan³

2014

J Mater Sci: Mater Electron

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Nano-sized, non-reacting, non-coarsening CeO 2 particles with a density close to that of solder alloy were incorporated into Sn-3.0 wt%Ag-0.5 wt%Cu solder paste. The interfacial microstructure and hardness of Ag surfacefinished Cu substrates were investigated, as a function of reaction time, at various temperatures. After the initial reaction, an island-shaped Cu 6 Sn 5 intermetallic compound (IMC) layer was clearly observed at the interfaces of the SnAg-Cu based solders/immersion Ag plated Cu substrates. However, after a prolonged reaction, a very thin, firmly adhering Cu 3 Sn IMC layer was observed between the Cu 6 Sn 5 IMC layer and the substrates. Rod-like Ag 3 Sn IMC particles were also clearly observed at the interfaces. At the interfaces of the Sn-Ag-Cu based solder-Ag/Ni metallized Cu substrates, a (Cu, Ni)-Sn IMC layer was found. Rod-like Ag 3 Sn and needle-shaped Cu 6 Sn 5 IMC particles were also observed on the top surface of the (Cu, Ni)-Sn IMC layer. As the temperature and reaction time increased, so did the thickness of the IMC layers. In the solder ball region of both systems, a fine microstructure of Ag 3 Sn, Cu 6 Sn 5 IMC particles appeared in the b-Sn matrix. However, the growth behavior of the IMC layers of composite solder doped with CeO 2 nanoparticles was inhibited, due to an accumulation of surface-active CeO 2 nanoparticles at the grain boundary or in the IMC layers. In addition, the composite solder joint doped with CeO 2 nanoparticles had a higher hardness value than the plain Sn-Ag-Cu solder joints, due to a well-controlled fine microstructure and uniformly distributed CeO 2 nanoparticles. After 5 min of reaction on immersion Agplated Cu substrates at 250°C, the micro-hardness values of the plain Sn-Ag-Cu solder joint and the composite solder joints containing 1 wt% of CeO 2 nanoparticles were approximately 16.6 and 18.6 Hv, respectively. However after 30 min of reaction, the hardness values were approximately 14.4 and 16.6 Hv, while the micro-hardness values of the plain Sn-Ag-Cu solder joints and the composite solder joints on Ag/Ni metallized Cu substrates after 5 min of reaction at 250°C were approximately 15.9 and 17.4 Hv, respectively. After 30 min of reaction, values of approximately 14.4 and 15.5 Hv were recorded.

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“…Substrate dissolution can substantially change the composition of the solder, which in turn may profoundly influence the physical/chemical characteristics of both the solder and the compound(s) formed at the interface. [2][3][4] Kang et al 4,5 reported that dissolution of a Cu pad into a molten solder altered the crystal orientation and microstructure of the b-Sn grains. A few large grains in pure Sn or Sn-0.5Cu matrixes were replaced by many columnar grains when Cu dissolution was important.…”

Section: Introductionmentioning

confidence: 99%

Effects of Joining Sequence on the Interfacial Reactions and Substrate Dissolution Behaviors in Ni/Solder/Cu Joints

Liu

Peng

et al. 2011

Journal of Elec Materi

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The effects of the joining sequence on the interfacial reactions and substrate dissolution behaviors in Ni/solder/Cu joints were studied by using 500-lm (diameter) Sn-3.5Ag solder balls and substrates with a 375-lm (diameter) opening. Three distinct paths for the joining sequence were studied. In path I, a solder ball was first joined to the Cu substrate and then to the Ni substrate. In path II, a solder ball was joined to both the Cu and Ni substrates simultaneously. Path III had the opposite joining sequence to path I. The results of this study indicated that (Cu,Ni) 6 Sn 5 was the predominant reaction product at both the Ni/solder and solder/Cu interfaces regardless of the joining sequence. However, the composition, morphology, and thickness of the (Cu,Ni) 6 Sn 5 varied considerably with the different paths. The dissolution behaviors of Cu and Ni were also different. Dybkov's dissolution kinetics and Cu-Ni-Sn isotherm data were utilized to rationalize these differences.

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The Crystal Orientation of β-Sn Grains in Sn-Ag and Sn-Cu Solders Affected by Their Interfacial Reactions with Cu and Ni(P) Under Bump Metallurgy

Cited by 58 publications

References 28 publications

Nucleation and Growth of Tin in Pb-Free Solder Joints

Nucleation and Growth of Tin in Pb-Free Solder Joints

Influence of cerium oxide (CeO2) nanoparticles on the microstructure and hardness of tin–silver–copper (Sn–Ag–Cu) solders on silver (Ag) surface-finished copper (Cu) substrates

Effects of Joining Sequence on the Interfacial Reactions and Substrate Dissolution Behaviors in Ni/Solder/Cu Joints

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