Microstructure evolution of the Sn–Ag–y%Cu interconnect

Lu, Henry Y.; Balkan, H.; Ng, Koon‐Kwan

doi:10.1016/j.microrel.2005.08.004

Cited by 17 publications

(8 citation statements)

References 17 publications

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“…Cu 6 Sn 5 present within the interior of the joints formed as large irregular-shaped particles. Lu et al [59] also observed large, irregular Cu 6 Sn 5 intermetallic precipitates formed in the bulk of Sn-3.5Ag alloy, when concentrations of Cu exceeded 0.5 wt pct. They showed the existence of Cu 6 Sn 5 precipitates with ''scissor'' type morphology, approximately 25 to 28 lm in size.…”

Section: A Microstructure Characterizationmentioning

confidence: 92%

Microstructure Characterization and Creep Behavior of Pb-Free Sn-Rich Solder Alloys: Part I. Microstructure Characterization of Bulk Solder and Solder/Copper Joints

Sidhu

Chawla

2008

Metall Mater Trans A

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Solders are used as interconnect materials in microelectronic packaging. Traditionally, eutectic and near-eutectic Pb-Sn solder alloys have been used. Due to the toxic nature of lead, environmentally-benign Sn-rich (Pb-free) solders are being developed. In this two part series of articles, we have focused on elucidating the relationship between microstructure and creep behavior of Sn-rich alloys, both in bulk form and at the solder sphere joint level. Part I of our study focuses on a detailed quantitative analysis of the effect of controlled cooling rates on solder microstructures. Bulk solder microstructures from cast bars were compared to smaller solder joint microstructures, reflowed from single solder spheres about 1 mm in diameter. Faster cooling rates resulted in much finer secondary dendrite size and spacing, as well as a much finer distribution of Ag 3 Sn and Cu 6 Sn 5 particles. The companion article, Part II, provides a unified mechanistic understanding of the creep behavior for the Sn-rich solder alloys, intimately linked to the microstructure characterization work reported in Part I.

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Section: A Microstructure Characterizationmentioning

confidence: 92%

Microstructure Characterization and Creep Behavior of Pb-Free Sn-Rich Solder Alloys: Part I. Microstructure Characterization of Bulk Solder and Solder/Copper Joints

Sidhu

Chawla

2008

Metall Mater Trans A

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“…To understand the damage mechanism in solder joints we have to take a closer look at the microstructure. Many authors have investigated the microstructure of lead-free solder joints after the soldering process [53][54][55][56][57][58][59][60].…”

Section: Motivationmentioning

confidence: 99%

“…Since the dendrites and the intermetallic dispersions inside the grains are small compared to the joint size [53][54][55][56][57][58][59][60], a homogeneous description of the grains themselves will be used in the simulation. To be able to construct joints with random grain structures we make the following assumptions for BGA joints with a diameter of 600µm:…”

Section: Grain Structure Generationmentioning

confidence: 99%

A robust preconditioning technique for the extended finite element method

Menk

Bordas

2010

Numerical Meth Engineering

140

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In electronic devices solder joints form a mechanical as well as an electrical connection between the circuit board and the component (e.g. a chip or a resistor). Temperature variations occurring during field use cause crack initiation and crack growth inside the joints. Accurate prediction of the lifetime requires a method to simulate the damage process based on microstructural properties.Numerical simulation of developing cracks and microstructural entities such as grain boundaries and grain junctions gives rise to several problems. The solution contains strong and weak discontinuities as well as weak singularities. To obtain reasonable solutions with the finite element method (FEM) the element edges have to align with the cracks and the grain boundaries, which imposes geometrical restrictions on the mesh choice. Additionally, a large number of elements has to be used in the vicinity of the singularities which increases the computational effort. Both problems can be circumvented with the extended finite element method (X-FEM) by using appropriate enrichment functions.In this thesis the X-FEM will be developed for the simulation of complex microstructural geometries. Due to the anisotropy of the different grains forming a joint and the variety of different microstructural configurations it is not always possible to write the enrichment functions in a closed form. A procedure to determine enrichment functions numerically is explained and tested. As a result, a very simple meshing scheme, which will be introduced here, can be used to simulate developing cracks in solder joint microstructures. Due to the simplicity of the meshing algorithm the simulation can be automated completely. A large number of enrichment functions must be used to realize this. Well-conditioned equation systems, however, cannot be guaranteed for such an approach. To improve the condition number of the X-FEM stiffness matrix and thus the robustness of the solution process a preconditioning technique is derived and applied.This approach makes it possible to develop a new and fully automated procedure for addressing the reliability of solder joints numerically. The procedure relies on the random generation of microstructures. Performing crack growth calculations for a series of these structures makes it possible to address the influence of varying microstructures on the damage process. Material parameters describing the microstructure are determined in an inverse procedure. It will be shown that the numerical results correspond well with experimental observations.

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“…Their size, shape, and distribution play a crucial role in determining the creep, thermomechanical fatigue behavior, ductility, and mechanical shock response of Pb-free solder alloys (Chawla, 2009). The morphology of these IMCs can vary drastically as a function of cooling rate, solder alloy composition, under bump metallization (UBM), and solder joint size (Ochoa et al, 2003; Fix et al, 2005; Lu et al, 2006). A few authors have implemented a deep-etching technique to reveal their evolution from near-spherical to plate-shaped in Ag 3 Sn (Lee & Chen, 2011), and to intersecting rods and bean-like morphology in Cu 6 Sn 5 (Lu et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Nanoscale Three-Dimensional Microstructural Characterization of an Sn-Rich Solder Alloy Using High-Resolution Transmission X-Ray Microscopy (TXM)

et al. 2016

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Three-dimensional (3D) nondestructive microstructural characterization was performed using full-field transmission X-ray microscopy on an Sn-rich alloy, at a spatial resolution of 60 nm. This study highlights the use of synchrotron radiation along with Fresnel zone plate optics to perform absorption contrast tomography for analyzing nanoscale features of fine second phase particles distributed in the tin matrix, which are representative of the bulk microstructure. The 3D reconstruction was also used to quantify microstructural details of the analyzed volume.

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Microstructure evolution of the Sn–Ag–y%Cu interconnect

Cited by 17 publications

References 17 publications

Microstructure Characterization and Creep Behavior of Pb-Free Sn-Rich Solder Alloys: Part I. Microstructure Characterization of Bulk Solder and Solder/Copper Joints

Microstructure Characterization and Creep Behavior of Pb-Free Sn-Rich Solder Alloys: Part I. Microstructure Characterization of Bulk Solder and Solder/Copper Joints

A robust preconditioning technique for the extended finite element method

Nanoscale Three-Dimensional Microstructural Characterization of an Sn-Rich Solder Alloy Using High-Resolution Transmission X-Ray Microscopy (TXM)

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