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Yishao Lai - One of the best experts on this subject based on the ideXlab platform.
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effect of Electromigration induced joule heating and strain on microstructural recrystallization in eutectic snpb flip chip solder joints
Materials Chemistry and Physics, 2012Co-Authors: Fanyi Ouyang, Yishao LaiAbstract:Abstract A refinement of the lamellar microstructure was observed in eutectic SnPb solder joints in Electromigration. Electromigration has both atomic flux and electron flow. The latter generated joule heating and the former caused strain. The formation of nanoscale lamellar microstructure spent a large amount of interfacial energy, and we proposed that the driving force comes from the strain induced by Electromigration under a high current density. Kinetically, refinement of the lamellar microstructure required fast atomic diffusion at a high homologous temperature. The joule heating mainly from the on-chip Al interconnect lines tremendously increased the temperature of solder bumps and enabled fast atomic diffusion. The strain induced by Electromigration, when combined with a high homologous temperature, could lead to recrystallization in the sample to form the nanoscale lamellae.
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quantitative x ray microtomography study of 3 d void growth induced by Electromigration in eutectic snpb flip chip solder joints
Scripta Materialia, 2011Co-Authors: Tian Tian, Kai Chen, Alastair A Macdowell, Dula Parkinson, Yishao LaiAbstract:Vacancy flux in eutectic flip-chip SnPb solder joints driven by Electromigration was studied using synchrotron radiation X-ray microtomography technique. The change in void volume and shape in three-dimensional images was measured quantitatively and the product of diffusivity and effective charge number of Electromigration in eutectic SnPb alloy was calculated to be 3.3 × 10−9 and 9.5 × 10−9 cm2 s−1 at 100 and 120 °C, respectively. The activation energy of the effective self-diffusivity in SnPb alloy was measured to be 0.66 eV.
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effect of current crowding on whisker growth at the anode in flip chip solder joints
Applied Physics Letters, 2007Co-Authors: Fanyi Ouyang, Kai Chen, Yishao LaiAbstract:Owing to the line-to-bump configuration in flip chip solder joints, current crowding occurs when electrons enter into or exit from the solder bump. At the cathode contact, where electrons enter into the bump, current crowding induced pancake-type void formation has now been observed widely. At the anode contact, where electrons exit from the bump, we report here that whisker is formed. Results of both eutectic SnPb and SnAgCu solder joints are presented and compared. The cross-sectioned surface in SnPb showed dimple and bulge after Electromigration, while that of SnAgCu remained flat. The difference is due to a larger back stress in the SnAgCu, consequently, Electromigration in SnAgCu is slower than that in SnPb. Nanoindentation markers were used to measure the combined atomic fluxes of back stress and Electromigration.
Chih Chen - One of the best experts on this subject based on the ideXlab platform.
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effect of under bump metallization structure on Electromigration of sn ag solder joints
Advances in materials research, 2012Co-Authors: Hsiaoyun Chen, Minfeng Ku, Chih ChenAbstract:【The effect of under-bump-metallization (UBM) on Electromigration was investigated at temperatures ranging from $135^{\circ}C$ to $165^{\circ}C$ . The UBM structures were examined: 5- ${\mu}m$ -Cu/3- ${\mu}m$ -Ni and $5{\mu}m$ Cu. Experimental results show that the solder joint with the Cu/Ni UBM has a longer Electromigration lifetime than the solder joint with the Cu UBM. Three important parameters were analyzed to explain the difference in failure time, including maximum current density, hot-spot temperature, and Electromigration activation energy. The simulation and experimental results illustrate that the addition 3- ${\mu}m$ -Ni layer is able to reduce the maximum current density and hot-spot temperature in solder, resulting in a longer Electromigration lifetime. In addition, the Ni layer changes the Electromigration failure mode. With the $5{\mu}m$ Cu UBM, dissolution of Cu layer and formation of $Cu_6Sn_5$ intermetallic compounds are responsible for the Electromigration failure in the joint. Yet, the failure mode changes to void formation in the interface of $Ni_3Sn_4$ and the solder for the joint with the Cu/Ni UBM. The measured activation energy is 0.85 eV and 1.06 eV for the joint with the Cu/Ni and the Cu UBM, respectively.】
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Electromigration in sn cu intermetallic compounds
Journal of Applied Physics, 2009Co-Authors: C C Wei, Chuanli Chen, Po Chun Liu, Chih ChenAbstract:As the shrinking in bump size continues, the effect of intermetallic compounds (IMCs) on Electromigration becomes more pronounced. Electromigration in Sn–Cu intermetallic compounds was examined using edge displacement method. It was found that Cu6Sn5 compounds are more susceptible to Electromigration than Cu3Sn compounds. The lower solidus temperature and higher resistivity of the Cu6Sn5 IMCs are responsible for its higher Electromigration rate. Length-dependent Electromigration behavior was found in the stripes of various lengths and the critical length was determined to be between 5 and 10 μm at 225 °C, which corresponded to a critical product between 2.5 and 5 A/cm. Furthermore, the Sn–Cu compounds were proven to have better Electromigration resistance than eutectic SnAgCu solder.
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direct measurement of hot spot temperature in flip chip solder joints under current stressing using infrared microscopy
Journal of Applied Physics, 2008Co-Authors: Hsiang Yao Hsiao, S.w. Liang, Minfeng Ku, Chih ChenAbstract:Several simulation studies reported that a hot spot exists in flip-chip solder bumps under accelerated Electromigration. Yet, there are no experimental data to verify it. In this paper, the temperature distribution during Electromigration in flip-chip SnAg3.5 solder bumps is directly inspected using infrared microscopy. Two clear hot spots are observed in the bump. One is located at the region with peak current density and the other one is at the bump edge under the current-feeding metallization on the chip side. Under a current stress of 1.06×104A∕cm2, the temperature in the two hot spots are 161.7 and 167.8°C, respectively, which surpass the average bump temperature of 150.5°C. In addition, the effect of under-bump-metallization (UBM) thickness on the hot spots is also examined. It indicates that the hot-spot temperature in the solder bump increases for the solder joints with a thinner UBM. Electromigration test indicates that these hot spots have significant influence on the initial failure location.
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study of void formation due to Electromigration in flip chip solder joints using kelvin bump probes
Applied Physics Letters, 2006Co-Authors: Y W Chang, S.w. Liang, Chih ChenAbstract:Kelvin bump probes were fabricated in flip-chip solder joints, and they were employed to monitor the void formation during Electromigration. We found that voids started to form at approximately 5% of the failure time under 0.8A at 150°C, and the bump resistance increased only 0.02mΩ in the initial stage of void formation. Three-dimensional simulation was performed to examine the increase in bump resistance at different stages of void formation, and it fitted the experimental results quite well. This technique provides a systematic way for investigating the void formation during Electromigration.
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Electromigration in eutectic snpb solder lines
Journal of Applied Physics, 2001Co-Authors: Q T Huynh, C Y Liu, Chih ChenAbstract:We have prepared eutectic SnPb solder lines for Electromigration study by a process of solder reflow into V-grooves etched on (001) Si wafer surfaces. They are thick lines and are highly reproducible. We report here results of lines of 100 μm in width and 150 to 800 μm in length, stressed by a current density of 2.8×104 A/cm2 at 150 °C in ambient. The accumulation of a large lump of solder, rather than hillocks of Sn and Pb, was observed at the anode, and depletions and voids were observed at the cathode. By measuring the volume of the lump, we have calculated the average effective charge number of Electromigration in the eutectic solder to be 33, which is close to the reported value of 47 for self-Electromigration in bulk Pb. Using x-ray dispersive analysis, we found that Pb is the dominant diffusing species.
Kingning Tu - One of the best experts on this subject based on the ideXlab platform.
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in situ measurement of Electromigration induced transient stress in pb free sn cu solder joints by synchrotron radiation based x ray polychromatic microdiffraction
Journal of Applied Physics, 2009Co-Authors: Kai Chen, Nobumichi Tamura, Martin Kunz, Kingning TuAbstract:Electromigration-induced hydrostatic elastic stress in Pb-free SnCu solder joints was studied by in situ synchrotron X-ray white beam microdiffraction. The elastic stresses in two different grains with similar crystallographic orientation, one located at the anode end and the other at the cathode end, were analyzed based on the elastic anisotropy of the {beta}-Sn crystal structure. The stress in the grain at the cathode end remained constant except for temperature fluctuations, while the compressive stress in the grain at the anode end was built-up as a function of time during Electromigration until a steady state was reached. The measured compressive stress gradient between the cathode and the anode is much larger than what is needed to initiate Sn whisker growth. The effective charge number of {beta}-Sn derived from the Electromigration data is in good agreement with the calculated value.
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Electromigration in flip chip solder joints having a thick cu column bump and a shallow solder interconnect
Journal of Applied Physics, 2006Co-Authors: Kingning Tu, Seung Wook Yoon, Vaidyanathan KripeshAbstract:In advanced electronic products, current crowding induced Electromigration failure is one of the serious problems in fine pitch flip chip solder joints. To explore a strong resistance against current crowding induced Electromigration failure, a very thick Cu column bump combined with a shallow solder interconnect at 100μm pitch for flip chip applications has been studied in this paper. Results revealed that these interconnects do not fail after 720h of current stressing at 100°C with a current density of 1×104A∕cm2 based on the area of interface between Cu column bump and solder. The reduction of current crowding in the solder region by using thick Cu column bumps increased the reliability against Electromigration induced failure. The current distribution in a flip chip joint of a Cu column bump combined with a shallow solder has been confirmed by simulation. However, Kirkendall void formation was found to be much serious and enhanced by Electromigration at the Cu∕Cu3Sn interface due to the large Cu∕Sn ra...
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Electromigration of eutectic snpb and snag3 8cu0 7 flip chip solder bumps and under bump metallization
Journal of Applied Physics, 2001Co-Authors: Kingning Tu, Darrel R FrearAbstract:The Electromigration damage in flip chip solder bumps of eutectic SnPb and SnAg3.8Cu0.7 was studied after current stressing at 120 °C with 1.5 A. The diameter of the bumps was about 200 μm. The under-bump metallization (UBM) on the chip side was electroless Ni and on the board side was electroplated Cu. Surface marker motion was used to measure the atomic flux driven by Electromigration and to calculate the effective charge number, Z*, of the solder. For eutectic SnPb, Z* is about 36–100 after 39.5 h of Electromigration, but for SnAg3.8Cu0.7 the marker movement was too small to measure Z* even after 200 h of current stressing. While the effect of Electromigration in SnAg3.8Cu0.7 is much smaller than that in eutectic SnPb, hillocks of intermetallic compounds at the anode have been observed in the former. An extensive growth of Ni–Cu–Sn intermetallic compounds in the matrix of both solder bumps was found. A localized dissolution of electroless Ni UBM was observed under current stressing, yet no dissolution ...
Kai Chen - One of the best experts on this subject based on the ideXlab platform.
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quantitative x ray microtomography study of 3 d void growth induced by Electromigration in eutectic snpb flip chip solder joints
Scripta Materialia, 2011Co-Authors: Tian Tian, Kai Chen, Alastair A Macdowell, Dula Parkinson, Yishao LaiAbstract:Vacancy flux in eutectic flip-chip SnPb solder joints driven by Electromigration was studied using synchrotron radiation X-ray microtomography technique. The change in void volume and shape in three-dimensional images was measured quantitatively and the product of diffusivity and effective charge number of Electromigration in eutectic SnPb alloy was calculated to be 3.3 × 10−9 and 9.5 × 10−9 cm2 s−1 at 100 and 120 °C, respectively. The activation energy of the effective self-diffusivity in SnPb alloy was measured to be 0.66 eV.
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in situ measurement of Electromigration induced transient stress in pb free sn cu solder joints by synchrotron radiation based x ray polychromatic microdiffraction
Journal of Applied Physics, 2009Co-Authors: Kai Chen, Nobumichi Tamura, Martin Kunz, Kingning TuAbstract:Electromigration-induced hydrostatic elastic stress in Pb-free SnCu solder joints was studied by in situ synchrotron X-ray white beam microdiffraction. The elastic stresses in two different grains with similar crystallographic orientation, one located at the anode end and the other at the cathode end, were analyzed based on the elastic anisotropy of the {beta}-Sn crystal structure. The stress in the grain at the cathode end remained constant except for temperature fluctuations, while the compressive stress in the grain at the anode end was built-up as a function of time during Electromigration until a steady state was reached. The measured compressive stress gradient between the cathode and the anode is much larger than what is needed to initiate Sn whisker growth. The effective charge number of {beta}-Sn derived from the Electromigration data is in good agreement with the calculated value.
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effect of current crowding on whisker growth at the anode in flip chip solder joints
Applied Physics Letters, 2007Co-Authors: Fanyi Ouyang, Kai Chen, Yishao LaiAbstract:Owing to the line-to-bump configuration in flip chip solder joints, current crowding occurs when electrons enter into or exit from the solder bump. At the cathode contact, where electrons enter into the bump, current crowding induced pancake-type void formation has now been observed widely. At the anode contact, where electrons exit from the bump, we report here that whisker is formed. Results of both eutectic SnPb and SnAgCu solder joints are presented and compared. The cross-sectioned surface in SnPb showed dimple and bulge after Electromigration, while that of SnAgCu remained flat. The difference is due to a larger back stress in the SnAgCu, consequently, Electromigration in SnAgCu is slower than that in SnPb. Nanoindentation markers were used to measure the combined atomic fluxes of back stress and Electromigration.
Fanyi Ouyang - One of the best experts on this subject based on the ideXlab platform.
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effect of Electromigration induced joule heating and strain on microstructural recrystallization in eutectic snpb flip chip solder joints
Materials Chemistry and Physics, 2012Co-Authors: Fanyi Ouyang, Yishao LaiAbstract:Abstract A refinement of the lamellar microstructure was observed in eutectic SnPb solder joints in Electromigration. Electromigration has both atomic flux and electron flow. The latter generated joule heating and the former caused strain. The formation of nanoscale lamellar microstructure spent a large amount of interfacial energy, and we proposed that the driving force comes from the strain induced by Electromigration under a high current density. Kinetically, refinement of the lamellar microstructure required fast atomic diffusion at a high homologous temperature. The joule heating mainly from the on-chip Al interconnect lines tremendously increased the temperature of solder bumps and enabled fast atomic diffusion. The strain induced by Electromigration, when combined with a high homologous temperature, could lead to recrystallization in the sample to form the nanoscale lamellae.
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effect of current crowding on whisker growth at the anode in flip chip solder joints
Applied Physics Letters, 2007Co-Authors: Fanyi Ouyang, Kai Chen, Yishao LaiAbstract:Owing to the line-to-bump configuration in flip chip solder joints, current crowding occurs when electrons enter into or exit from the solder bump. At the cathode contact, where electrons enter into the bump, current crowding induced pancake-type void formation has now been observed widely. At the anode contact, where electrons exit from the bump, we report here that whisker is formed. Results of both eutectic SnPb and SnAgCu solder joints are presented and compared. The cross-sectioned surface in SnPb showed dimple and bulge after Electromigration, while that of SnAgCu remained flat. The difference is due to a larger back stress in the SnAgCu, consequently, Electromigration in SnAgCu is slower than that in SnPb. Nanoindentation markers were used to measure the combined atomic fluxes of back stress and Electromigration.