Critical Review of Size Effects on Microstructure and Mechanical Properties of Solder Joints for Electronic Packaging

Wang, Shaobin; Yao, Yao; Long, Xu

doi:10.3390/app9020227

Cited by 30 publications

(9 citation statements)

References 58 publications

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“…Cu (1) and Sn atoms form a NiAs-type arrangement. Further, Cu (2) atoms partially occupy the trigonal-bipyramidal sites formed by Sn 7 , where the hexagonal unit cell attains an axial ratio c h /a h ≈ √ 3 ∕ 2 (2c, 2a and 2d Wyckoff sites, for Sn, Cu (1) and Cu(2), respectively 7 ), in agreement with the crystal structures of a larger series of phases 8 . Assigning an average occupancy of δ to the Cu(2) sites, the η phase attains a composition Cu(1)Cu(2) δ Sn or, in short, Cu 1+δ Sn, where the composition is quantified in terms of the value of the parameter δ.…”

Section: Introductionsupporting

confidence: 78%

“…(4). 2 (0) and (∞) are taken from the as-homogenized alloy and from the alloy having experienced the longest treatment time. The fitted values of D/R 2 are contained in Table II.…”

Section: Evaluation Of Diffusion Coefficientmentioning

confidence: 99%

“…Sn-rich alloy systems are of fundamental importance in understanding the microstructural changes occurring during the course of many soldering processes, in particular lead-free soldering [1][2][3] . Knowledge of the phase diagram provides the basic fundament for predicting these changes.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Stable and Metastable Phase Equilibria Involving the Cu6Sn5 Intermetallic

Leineweber

Löffler

Martin

2021

J. Electron. Mater.

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Cu6Sn5 intermetallic occurs in the form of differently ordered phases η, η′ and η′′. In solder joints, this intermetallic can undergo changes in composition and the state of order without or while interacting with excess Cu and excess Sn in the system, potentially giving rise to detrimental changes in the mechanical properties of the solder. In order to study such processes in fundamental detail and to get more detailed information about the metastable and stable phase equilibria, model alloys consisting of Cu3Sn + Cu6Sn5 as well as Cu6Sn5 + Sn-rich melt were heat treated. Powder x-ray diffraction and scanning electron microscopy supplemented by electron backscatter diffraction were used to investigate the structural and microstructural changes. It was shown that Sn-poor η can increase its Sn content by Cu3Sn precipitation at grain boundaries or by uptake of Sn from the Sn-rich melt. From the kinetics of the former process at 513 K and the grain size of the η phase, we obtained an interdiffusion coefficient in η of (3 ± 1) × 10−16 m2 s−1. Comparison of this value with literature data implies that this value reflects pure volume (inter)diffusion, while Cu6Sn5 growth at low temperature is typically strongly influenced by grain-boundary diffusion. These investigations also confirm that η′′ forming below a composition-dependent transus temperature gradually enriches in Sn content, confirming that Sn-poor η′′ is metastable against decomposition into Cu3Sn and more Sn-rich η or (at lower temperatures) η′. Graphic Abstract

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Section: Introductionsupporting

confidence: 78%

“…(4). 2 (0) and (∞) are taken from the as-homogenized alloy and from the alloy having experienced the longest treatment time. The fitted values of D/R 2 are contained in Table II.…”

Section: Evaluation Of Diffusion Coefficientmentioning

confidence: 99%

See 1 more Smart Citation

Stable and Metastable Phase Equilibria Involving the Cu6Sn5 Intermetallic

Leineweber

Löffler

Martin

2021

J. Electron. Mater.

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“…The effect of solder volume has been investigated by several researchers to comprehend the IMC thickness at the solder joints [101][102][103][104]. Different solder volumes give rise to different interfacial reactions which in turns affect the formation of interfacial IMC and the microstructure [101].…”

Section: Effect Of Solder Volumementioning

confidence: 99%

Formation and Growth of Intermetallic Compounds in Lead-Free Solder Joints: A Review

et al. 2022

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Recently, research into the factors that influence the formation and growth of intermetallic compounds (IMCs) layer in lead-free solders has piqued interest, as IMCs play an important role in solder joints. The reliability of solder joints is critical to the long-term performance of electronic products. One of the most important factors which are known to influence solder joint reliability is the intermetallic compound (IMC) layer formed between the solder and the substrate. Although the formation of an IMC layer signifies good bonding between the solder and substrate, its main disadvantage is due to its brittle nature. This paper reviews the formation and growth of IMCs in lead-free solder joints detailing the effect of alloying additions, surface finishes, aging time, aging temperature and solder volume. The formation and growth of the brittle IMCs were significantly affected by these factors and could be possibly controlled. This review may be used as a basis in understanding the major factors effecting the IMC formation and growth and relating it to the reliability of solder joints.

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“…With a sustained miniaturization for 3D TSV packaging, the micro solder-joints are being scaled down to be less than twenty microns from the current one hundred microns [3,4]. Such a dramatical reduction in size tends to result in the evolution of microstructure and mechanical properties of the micro-joints, and thereby triggering mechanical reliability issues [5,6]. The interfacial intermetallic compounds (IMCs) layer with a suitable thickness is an excellent indication of metallurgical bonding in solder joints [7].…”

Section: Introductionmentioning

confidence: 99%

IMCs Microstructure Evolution Dependence of Mechanical Properties for Ni/Sn/Ni Micro Solder-Joints

et al. 2020

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The current miniaturization trend of microelectronic devices drives the size of solder joints to continually scale down. The miniaturized joints considerably increase intermetallic compounds (IMCs) volume fraction to trigger mechanical reliability issues. This study investigated precise relationships between varying IMC volumes and mechanical properties of Ni/Sn(20μm)/Ni micro-joints. A designed method that followed the IMC volume as the only variable was used to prepare micro-joint samples with different IMC volumes. The continuously thickened Ni3Sn4 IMCs exhibited a noticeable morphology evolution from rod-like to chunky shape. The subsequent tensile tests showed unexpected tensile strength responses as increasing Ni3Sn4 volume, which was strongly associated with the Ni3Sn4 morphological evolutions. Fractographic analysis displayed that the ductile fracture dominates the 20%–40% IMC micro-joints, whereas the brittle fracture governs the 40%–80% IMC micro-joints. For the ductile fracture-dominated joints, an abnormal reduction in strength occurred as increasing IMCs volume from 20% to 40%. This is primarily due to severe stress concentrations caused by the transformed long rod-typed morphology of the Ni3Sn4. For the brittle fracture-dominated joints, the strength appeared a monotonous increase as the Ni3Sn4 volume increased. This may be attributed to the increased crack resistance resulting from continuous coarsening of the chunky Ni3Sn4 without any voids. Moreover, the finite element analysis was provided to further understand the joint failure mechanisms.

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Critical Review of Size Effects on Microstructure and Mechanical Properties of Solder Joints for Electronic Packaging

Cited by 30 publications

References 58 publications

Stable and Metastable Phase Equilibria Involving the Cu6Sn5 Intermetallic

Stable and Metastable Phase Equilibria Involving the Cu6Sn5 Intermetallic

Formation and Growth of Intermetallic Compounds in Lead-Free Solder Joints: A Review

IMCs Microstructure Evolution Dependence of Mechanical Properties for Ni/Sn/Ni Micro Solder-Joints

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