Analysis and experimental verification of the competing degradation mechanisms for solder joints under electron current stressing

Ke, Jia-Hong; Yang, Tsung‐Lin; Lai, Yi-Sheng; Kao, C. R.

doi:10.1016/j.actamat.2010.12.048

Cited by 50 publications

(14 citation statements)

References 17 publications

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“…The other is to reduce the operating temperature of the device. Lowering the temperature is also crucial for reducing failure associated with excessive cathode dissolution [4].…”

Section: Discussionmentioning

confidence: 99%

“…Copper diffuses interstitially in Sn, and is a fast diffuser [2]. The rapid diffusion of Cu away from the cathode leads to the excess dissolution of intermetallic compounds and the cathode material [3,4]. Excessive dissolution of the cathode frequently leads to a distinctive serrated interface, with most of the serrated teeth inclined toward a specific direction [5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 98%

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Dominant effects of Sn orientation on serrated cathode dissolution and resulting failure in actual solder joints under electromigration

Yang

et al. 2015

Journal of Alloys and Compounds

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“…The other is to reduce the operating temperature of the device. Lowering the temperature is also crucial for reducing failure associated with excessive cathode dissolution [4].…”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Dominant effects of Sn orientation on serrated cathode dissolution and resulting failure in actual solder joints under electromigration

Yang

et al. 2015

Journal of Alloys and Compounds

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“…In addition, with the changing geometry and aspect ratio between fan-out wiring and vertical bump structure as well as the solder to under bump metallization (UBM) ratio, the impact of current crowding and high current density on bump EM performance for 3D IC interconnect could be very different. For example, UBM consumption has been reported to be one of the dominant failure modes for Pbfree C4 joint [7], where the ratio of solder volume to UBM is much higher than that of the bump, as shown in Fig. 1.…”

Section: Introductionmentioning

confidence: 93%

Generic rules to achieve bump electromigration immortality for 3D IC integration

Chen

Shih

Cai

et al. 2013

2013 IEEE 63rd Electronic Components and Technology Conference

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An immortal solder micro-bump (bump) electromigration (EM) lifetime has been demonstrated for 3D IC integration. This ultimate goal was achieved under strictly controlled conditions, including the optimal design of bump metallurgy, geometry, optimized processes, along with welldefined stressing conditions and manufacturing window. The current carrying capability and EM lifetime of bump have been investigated as functions of stressing conditions which are correlated with the degradation mechanisms. When stressed under the appropriate g conditions, all bump test samples survived prolonged stressing, some over 13,000 hours, without a failure. Cross-sectional analyses revealed that the entire solder joint almost all transformed into intermetallic compounds (IMCs) with very minor or no voids. The resistance plots showed an initial fast rise in resistance due to IMC formation, then gradually leveled off and eventually reached a steady state. The observed degradation mechanism is dominated by IMC formation, which is the same as that of the user conditions. On the other hand, void formation that eventually led to open failure was the dominant degradation mechanism when samples were aggressively stressed. In other words, when all other conditions were the same, the stressing conditions make a huge difference in determining between an almost immortal EM lifetime vs. a short lifetime using the same high quality bumps. The boundary that separates the stressing conditions is roughly defined and will be discussed.In addition, since full IMC bump will become inevitable in the future miniaturized solder interconnect structure, the EM behavior of IMC dominated bump has also been evaluated in this study. Under highly accelerated stressing conditions of 174°C, at 1.6×10 5 A/cm 2 current density, the IMC dominated bumps were able to survive more than 600 hours and are still going strong. In comparison, solder bump failed quickly after just 107 hours when stressed under the same condition. This comparison study clearly demonstrated that IMC dominated joint has significantly higher current carrying capability than that of the solder joint. After reviewing all the data, we have concluded that the failure criteria for solder bump should be raised significantly higher than the 20% criteria traditionally used for the much larger C4 bumps.

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“…A large atomic diffusion flux could induce the failure of solder bumps due to the void formation-and-propagation or the rapid dissolution of UBM at the cathode interfaces. 18,19 Therefore, the back stress flux has a positive effect on retardation of EM failure. However, due to a large amount of lattice sites are created and destroyed at the anode and cathode during stress relaxation, respectively, the back stress is reduced and so the effect of back stress on retardation of EM is less.…”

Section: Sliding Of Sn Grain Boundary In Solder Bumpsmentioning

confidence: 98%

Stress relaxation and failure behavior of Sn–3.0Ag–0.5Cu flip-chip solder bumps undergoing electromigration

et al. 2014

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The stress relaxation and failure behavior of Ni/Sn-3.0Ag-0.5Cu/electroless nickel electroless palladium immersion gold flip-chip solder bumps undergoing electromigration (EM) at 150°C under 1.5 Â 10 4 A/cm 2 was investigated in situ. Three modes of stress relaxation of Sn-3.0Ag-0.5Cu solder bumps were identified. At the cathode, voids and hollows with terrace morphology gradually formed to relieve the tensile stress; at the anode, especially around the current crowding corner, recrystallization of Sn grains and extrusion of hillocks occurred to relieve the compressive stress; in the solder bump, Sn grain boundary sliding that occurred to accommodate the diffusion creep was more pronounced with increasing EM time. Grain boundary sliding is considered to be an indispensable requisite for diffusion creep. The microstructural evolution of solder bumps at the last stage of lifetime was revealed, and the final EM-induced failure mode was the local fusion of a solder bump resulting from the crack formation-and-propagation at the cathode.

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Analysis and experimental verification of the competing degradation mechanisms for solder joints under electron current stressing

Cited by 50 publications

References 17 publications

Dominant effects of Sn orientation on serrated cathode dissolution and resulting failure in actual solder joints under electromigration

Dominant effects of Sn orientation on serrated cathode dissolution and resulting failure in actual solder joints under electromigration

Generic rules to achieve bump electromigration immortality for 3D IC integration

Stress relaxation and failure behavior of Sn–3.0Ag–0.5Cu flip-chip solder bumps undergoing electromigration

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