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

Lin, Yen‐Ting; Lai, Yi-Sheng; Lin, Yu-Cheng; Kao, C. R.

doi:10.1007/s11664-007-0293-3

Cited by 25 publications

(3 citation statements)

References 18 publications

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“…The difference became more significant at a higher stressing due to serious heat generation, which in turn caused a higher resistance to electromigration. [24] Current biasing (mA) Figure 4 illustrates the lifetime difference (∆T) of Cu vs Ni UBMs. It is clearly demonstrate ∆T reduces in exponential decay function with current biasing.…”

Section: B Finite Element Modelingmentioning

confidence: 99%

Comparison of electromigration for lead-free solder joints of Cu vs. Ni UBM flip chip structure

Rungyusiri

Sa-ngiamsak

Harnsoongnoen

et al. 2009

2009 6th International Conference on Electrical Engineering/Electronics, Computer, Telecommunications and Information Technolog

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Flip chip solder joints made with Cu and Ni underbump metallurgy (UBM) on the chip under current stressing were studied. The effects of material and various thicknesses (5, 10, 15, and 20 µm) of UBM on reliability were investigated. The solder material used was lead-free (Sn4.0Ag0.5Cu). Time to failure of both cases (Cu and Ni UBMs) was forecasted through the physical damage occurring at the bump under current stressing by using two-dimensional Finite Element Method (FEM). The simulation results conclude that thicker UBM can enhance electromigration reliability. Moreover, the comparison of the time to failure between Cu UBM structure with that of Ni UBM structure indicates that the time to failure of the flip chip solder joint with Cu UBM structure is approximately 5% longer than the case of Ni UBM structure due to the lowering current crowding effect at Cu UBM in the solder joint which is clearly shown in the simulations.

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Section: B Finite Element Modelingmentioning

confidence: 99%

Comparison of electromigration for lead-free solder joints of Cu vs. Ni UBM flip chip structure

Rungyusiri

Sa-ngiamsak

Harnsoongnoen

et al. 2009

2009 6th International Conference on Electrical Engineering/Electronics, Computer, Telecommunications and Information Technolog

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“…Although the voids exist at the intermetallic layer, the electrical signal may still be able to transit through the voids and passes the functional test. Adding Ni layer is the most common solution to extend the lifetime by blocking the Cu/Sn IMC diffusion, as it is more resistant to dissolution into solder joints (Lin et al, 2008); yet, higher resistance will be because of the natural characteristic of Ni layer, and even some of the magnetic sensitive devices may have concern for adding these material; hence, the lifetime and void formation rate is extremely important for the device when to do the design from the initial stage.…”

Section: Introductionmentioning

confidence: 99%

FCCSP IMC growth under reliability stress follows automotive criteria

Liu

Weng

Chen

2019

PRR

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Purpose -The Kirkendall void had been a well-known issue for long-term reliability of semiconductor interconnects; while even the KVs exist at the interfaces of Cu and Sn, it may still be able to pass the condition of unbias long-term reliability testing, especially for 2,000 cycles of temperature cycling test and 2,000 h of high temperature storage. A large number of KVs were observed after 200 cycles of temperature cycling test at the intermetallic Cu 3 Sn layer which locate between the intermetallic Cu 6 Sn 5 and Cu layers. These kinds of voids will grow proportional with the aging time at the initial stage. This paper aims to compare various IMC thickness as a function of stress test, the Cu 3 Sn and Cu 6 Sn 5 do affected seriously by heat, but Ni 3 Sn 4 is not affected by heat or moisture.Design/methodology/approach -The package is the design in the flip chip-chip scale package with bumping process and assembly. The package was put in reliability stress test that followed AEC-Q100 automotive criteria and recorded the IMC growing morphology.Findings -The Cu 6 Sn 5 intermetallic compound is the most sensitive to continuous heat which grows from 3 to 10 mm at high temperature storage 2,000 h testing, and the second is Cu 3 Sn IMC. Cu 6 Sn 5 IMC will convert to Cu 3 Sn IMC at initial stage, and then Kirkendall void will be found at the interface of Cu and Cu 3 Sn IMC, which has quality concerning issue if the void's density grows up. The first phase to form and grow into observable thickness for Ni and lead-free interface is Ni 3 Sn 4 IMC, and the thickness has little relationship to the environmental stress, as no IMC thickness variation between TCT, uHAST and HTSL stress test. The more the Sn exists, the thicker Ni 3 Sn 4 IMC will be derived from this experimental finding compare the Cu/Ni/SnAg cell and Ni/SnAg cell.Research limitations/implications -The research found that FCCSP can pass automotive criteria that follow AEC-Q100, which give the confidence for upgrading the package type with higher efficiency and complexities of the pin design.Practical implications -This result will impact to the future automotive package, how to choose the best package methodology and what is the way to do the package. The authors can understand the tolerance for the kind of flip chip package, and the bump structure is then applied for high-end technology.Originality/value -The overall three kinds of bump structures, Cu/Ni/SnAg, Cu/SnAg and Ni/SnAg, were taken into consideration, and the IMC growing morphology had been recorded. Also, the IMC had changed during the environmental stress, and KV formation was reserved.

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“…By utilizing simulation results, Liang et al found that joints with a thicker Cu UBM exhibited a lower maximum current density and hot spot temperature; the current crowding and local Joule heating effect vanished when the Cu UBM thickness was over than 50 µm (Liang et al 2006a). Moreover, Lin et al also reported that the joints with a thicker Ni UBM tend to have a longer electromigration lifetime (Lin et al 2008). The combination of current crowding and local Joule heating near the entrance point induced asymmetric of consumption Ni UBM.…”

Section: Introductionmentioning

confidence: 99%

Effect of under-bump-metallization structure on electromigration of Sn-Ag solder joints

Chen¹,

Ku²,

Chen³

2012

Advances in materials Research

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The effect of under-bump-metallization (UBM) on electromigration was investigated at temperatures ranging from 135 o C to 165 o C. The UBM structures were examined: 5-µm-Cu/3-µm-Ni and 5 µm 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-µm-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 µm Cu UBM, dissolution of Cu layer and formation of Cu 6 Sn 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 3 Sn 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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Effect of UBM Thickness on the Mean Time to Failure of Flip-Chip Solder Joints under Electromigration

Cited by 25 publications

References 18 publications

Comparison of electromigration for lead-free solder joints of Cu vs. Ni UBM flip chip structure

Comparison of electromigration for lead-free solder joints of Cu vs. Ni UBM flip chip structure

FCCSP IMC growth under reliability stress follows automotive criteria

Effect of under-bump-metallization structure on electromigration of Sn-Ag solder joints

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