Electromigration study in SnAg3.8Cu0.7 solder joints on Ti/Cr-Cu/Cu under-bump metallization

Hsu, Yi Chiung; Shao, T. L.; Yang, Ching Jung; Chen, Chih

doi:10.1007/s11664-003-0015-4

Cited by 31 publications

(9 citation statements)

References 13 publications

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“…The critical condition for triggering electromigration, derived mostly from study of flip chip solder joint, is at above 100 • C and of the order of 10 4 A/cm 2 [14,15]. However, the results in this work indicated that even at room temperature and low current density of 10 2 A/cm 2 , some electromigration-like behaviors in flip chip solder joints can still occur in Sn37Pb BGA solder joints.…”

Section: Resultsmentioning

confidence: 62%

Electric current effect on microstructure of ball grid array solder joint

Chan

2005

Journal of Alloys and Compounds

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Section: Resultsmentioning

confidence: 62%

Electric current effect on microstructure of ball grid array solder joint

Chan

2005

Journal of Alloys and Compounds

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“…This are was believed to have the highest local current density and the highest degree of current crowding initially. [2][3][4][5][6][7][8][9][10] Figure 5 is a zoom-in image for the left side of the void shown in Fig. 2b.…”

Section: Osp Surface Finishmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] To counter the negative effects caused by high current density, several approaches have been proposed and deployed. Two well-known approaches involve better circuit and interconnect designs.…”

Section: Introductionmentioning

confidence: 99%

Effect of surface finish on the failure mechanisms of flip-chip solder joints under electromigration

Lin

Lai

Tsai

et al. 2006

Journal of Elec Materi

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Two substrate surface finishes, Au/Ni and organic solderable preservative (OSP), were used to study the effect of the surface finish on the reliability of flip-chip solder joints under electromigration at 150°C ambient temperature. The solder used was eutectic PbSn, and the applied current density was 5 3 10 3 A/cm 2 at the contact window of the chip. The under bump metallurgy (UBM) on the chip was sputtered Cu/Ni. It was found that the mean-timeto-failure (MTTF) of the OSP joints was six times better than that of the Au/Ni joints (3080 h vs. 500 h). Microstructure examinations uncovered that the combined effect of current crowding and the accompanying local Joule heating accelerated the local Ni UBM consumption near the point of electron entrance. Once Ni was depleted at a certain region, this region became nonconductive, and the flow of the electrons was diverted to the neighboring region. This neighboring region then became the place where electrons entered the joint, and the local Ni UBM consumption was accelerated. This process repeated itself, and the Ni-depleted region extended further on, creating an ever-larger nonconductive region. The solder joint eventually failed when the nonconductive region became too large, making the effective current density very high. Accordingly, the key factor determining the MTTF was the Ni consumption rate. The joints with the OSP surface finish had a longer MTTF because Cu released from the substrate was able to reduce the Ni consumption rate.

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“…[1][2][3][4][5][6][7]10,11,13 In order to understand the degree of current crowding, a three-dimensional finite-element simulation was used to calculate the current density distribution of the joint. Figure 6a shows the mesh geometry used in this study.…”

Section: The Effect Of Current Crowding and Joule Heatingmentioning

confidence: 99%

“…2,3,[10][11][12] In this mechanism, a void forms in the solder at the location with the highest local current density, and the electrons are diverted around the void, making the solder next to the edge of the void become the highest current density region. This causes the void to grow toward the region with the highest current density.…”

Section: Failure Mechanism and The Mttfmentioning

confidence: 99%

Effect of UBM Thickness on the Mean Time to Failure of Flip-Chip Solder Joints under Electromigration

Lin

Lai

Lin

et al. 2007

Journal of Elec Materi

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Flip-chip solder joints with Cu/Ni/Al underbump metallurgy (UBM) on the chip and an Au/Ni surface finish on the substrate were studied under current stressing at an ambient temperature of 150°C. Three different Ni thicknesses in the Cu/Ni/Al UBM (0.3, 0.5, and 0.8 lm) were used in order to investigate the effect of the Ni thickness on reliability. The solder used was eutectic Pb-Sn, and the applied current density was 5 · 10 3 A/cm 2 . The results show that the combined effect of current crowding and the local Joule heating near the entry points of electrons into the joints induced asymmetric Ni UBM consumption. Once the Ni was exhausted in a certain region, this region became nonconductive and the flow of electrons was diverted to the neighboring region. This neighboring region then became the place where electrons entered the joint, and the Ni UBM there was consumed at an accelerated rate. This process repeated itself, and the Ni-depleted region continued to extend, creating an ever larger nonconductive region. The solder joints eventually failed when the nonconductive region extended across the entire contact window of the joints. This failure model supports the observation that joints with a thicker Ni tend to have a longer average lifetime.

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Electromigration study in SnAg3.8Cu0.7 solder joints on Ti/Cr-Cu/Cu under-bump metallization

Cited by 31 publications

References 13 publications

Electric current effect on microstructure of ball grid array solder joint

Electric current effect on microstructure of ball grid array solder joint

Effect of surface finish on the failure mechanisms of flip-chip solder joints under electromigration

Effect of UBM Thickness on the Mean Time to Failure of Flip-Chip Solder Joints under Electromigration

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