Fabrication and characterization of Cu-Sn-Ni-Cu interconnection microstructure for electromigration studies in 3D integration

Xiao, Ming; Munief, Walid; Wu, Fengshun; Lilischkis, Rainer; Oberbillig, Tobias; Saumer, Monika; Xia, Wenfang

doi:10.1108/ssmt-10-2015-0031

Cited by 5 publications

(3 citation statements)

References 32 publications

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“…EM was discussed in the case of different scales and different interconnects such as interconnects of very large-scale integrated systems (Tu, 2002), three dimensional connection structures (Xiao, 2016) or on the bumps of flip-chip components by Brandenburg and Yeh (1998) and Tu (2007). Most papers, including the thorough work of Tu, deal with the now generally obsolete SnPb alloys.…”

Section: Introductionmentioning

confidence: 99%

Advances on high current load effects on lead-free solder joints of SMD chip-size components and BGAs

Straubinger

Géczy

Sipos

et al. 2019

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Purpose This paper aims to present a novel approach on investigating critical current densities in the solder joints of chip-size surface-mounted components or device (SMD) components and ball grid array (BGA) lead-free solder joints with the focus of via-in-pad geometries. The investigation involves a numerical approach and a physical validation with selected geometry configurations and high current loads to reveal possible failure sources. The work is a continuation of a previous study. Design/methodology/approach Current density was investigated using finite element modeling on BGA joints. Dummy BGA components, 0402 and 0603 zero ohm jumper resistors, were used, both in daisy chain setups on standard FR4 printed circuit boards (PCBs). Respective physical loading experiments were set to find effects of elevated current density at hot zones of the joints. Cross-section analysis, scanning electron microscopy and shear force tests were used to analyze the joints. Findings The findings reveal alterations in the joints, while the current loading is not directly affecting the structure. The modeling reveals the current density map in the selected formations with increased current crowding zones. Overall, the degradation does not reach the level of electromigration (EM)-induced voiding due to the limiting factor of the FR4 substrate. Practical implications The heavy current load affects joint reliability, but there are limitations of EM-induced failures on PCB-based assemblies due to the thermomechanical weakness of the FR4 material. Originality/value The experiments investigate current density from a novel aspect on frequently used BGA surface mounted components with modeling configurations focusing on possible effects of via-in-pad structure.

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Section: Introductionmentioning

confidence: 99%

Advances on high current load effects on lead-free solder joints of SMD chip-size components and BGAs

Straubinger

Géczy

Sipos

et al. 2019

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show abstract

“…EM was discussed in the case of different scales and different interconnects, such as very large scale integration interconnects (Tu, 2003) specific 3D interconnects (Xiao et al, 2016) or flipchips (Brandenburg and Yeh, 1998) and (Tu, 2007). However, many papers, including the comprehensive work by Tu, gain knowledge in the eutectic SnPb alloy structureswhich still leave open questions for lead-free solders.…”

Section: Introductionmentioning

confidence: 99%

Effects of high current density on lead-free solder joints of chip-size passive SMD components

Géczy

Straubinger

Kovács

et al. 2018

SSMT

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Purpose -The purpose of this paper is to present a novel approach on investigating critical current densities in the solder joints of chip-size surface mounted device (SMD) components. The investigation involves a numerical approach and a physical validation with selected track-to-pad connections and high current loads (CXs). Design/methodology/approach -During the investigations, shape of solder fillets was calculated in Surface Evolver, and then the current densities were calculated accordingly in the given geometry. For the verification, CX tests were performed on joints at elevated temperatures. The joints were qualified with X-ray microscopy, cross-section analysis and shear tests. Findings -This study ascertained that the inhomogeneity in current density depends on the track-to-pad structure of the joint. Also this study found that the heavy CX decreases the mechanical strength, but the degradation does not reach the level of electromigration (EM)-induced voiding. Practical implications -The heavy CX significantly affects joint reliability and the results point out to EM-induced failure-limitations on printed circuit board (PCB)-based assemblies due to the thermomechanical weakness of the FR4 material. Originality/value -The experiments investigate current density from a novel aspect on more frequently used small-scale components with different track-to-pad configurationspointing out possible failure sources.

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“…Cu has excellent electrical conductivity; yet, it reacts rapidly with Sn-based solder systems to form a variety of intermetallic compounds (IMCs) which can degrade the solder joint reliability Xiao et al, 2016). Therefore, a coating of Ni over the Cu metallization is often used as a diffusion barrier (Chan et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Diffusion of elements during reflow ageing of Sn-Zn solder in liquid state on Ni/Cu substrate – theoretical and experimental study

Mittal

Lin²

2018

SSMT

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Purpose This paper aims to study the diffusion of Zn, Ni and Sn in the liquid state during the reflow ageing of the Sn-Zn solder above its melting point on an Ni/Cu substrate in relation to the formation of intermetallic compounds (IMCs). Design/methodology/approach The Sn-Zn solder is reflowed on Ni/Cu substrates and is aged at 503 K. The formation of IMCs and their composition is characterized using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Diffusion coefficients and diffusion distances of Zn, Ni and Sn in the liquid state during reflow and ageing are theoretically calculated. Both experimental and theoretical behaviours for Ni and Zn diffusions are compared. Findings Calculations show a linear increment in the liquid-state diffusion coefficients of Ni, Zn and Sn in the solder matrix with a rise in temperature, but they remained constant during ageing. However, diffusion distances increased slowly with temperature but manifold with ageing time. The experimental results revealed segregation of Zn and Ni at the interface in the as-reflow aged specimens. The Zn was concentrated at the solder–substrate interface and it reacted with Ni diffusing from the substrate to form Ni-Sn-Zn IMCs. The rapid diffusion of Zn and Ni with the increase in ageing time increased their atomic concentrations in the IMCs against the reduction in Sn concentration owing to a comparatively slower diffusion. Originality/value The novelty of the paper is the detailed study of theoretical diffusion of Zn, Sn and Ni in the liquid state during reflow ageing of Sn-Zn above its melting points on a Ni/Cu substrate. This is compared with values obtained experimentally and related to the mechanisms of IMC formation.

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Fabrication and characterization of Cu-Sn-Ni-Cu interconnection microstructure for electromigration studies in 3D integration

Cited by 5 publications

References 32 publications

Advances on high current load effects on lead-free solder joints of SMD chip-size components and BGAs

Advances on high current load effects on lead-free solder joints of SMD chip-size components and BGAs

Effects of high current density on lead-free solder joints of chip-size passive SMD components

Diffusion of elements during reflow ageing of Sn-Zn solder in liquid state on Ni/Cu substrate – theoretical and experimental study

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