Observation of amorphous chromium in modified C4 flip chip solder joints after thermal stress testing

Hooghan, Tejpal; Nakahara, S.; Hooghan, Kultaransingh; Privette, R.W; Bachman, Mark; Moyer, R.

doi:10.1016/s0040-6090(03)00679-5

Cited by 3 publications

(2 citation statements)

References 6 publications

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“…The ''solid-state amorphization'' phenomenon due to the interdiffusion of Ni and Sn in Ni(V) thin film had been reported. 16,17 Hooghan et al 30 observed an amorphous Cr layer in modified C4 flip-chip solder joints after thermal stressing. The formation mechanism of the amorphous Cr layer was proposed to be a three-stage process.…”

Section: Ni(v) Ubm Consumptionmentioning

confidence: 99%

Transmission Electron Microscopy Characterization of Ni(V) Metallization Stressed Under High Current Density in Flip Chip Solder Joints

Tsai

Lin

et al. 2010

Journal of Elec Materi

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The Ni(V) under bump metallization (UBM) in flip chip solder joints is known to be consumed in a two-stage process during current stressing. The Ni(V) UBM transforms first to the ''consumed Ni(V)'' state. Then, this consumed Ni(V) transforms to a so-called porous structure. In this study, the details of the consumed Ni(V) and the porous structure were analyzed by transmission electron microscopy. Bright-field images showed that the consumed Ni(V) was a continuous layer without columnar structures and that the porous structure had many voids in the matrix. The compositional analyses showed that V atoms were immobile and trapped in the original Ni(V) layer. Cu and Sn atoms diffused into the original Ni(V) layer, and Ni atoms diffused outward. Selected-area diffraction patterns and high-resolution transmission electron microscopy of the porous structure showed that it was composed of an amorphous matrix with fine crystalline Cu 6 Sn 5 and VSn 2 phases.

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Section: Ni(v) Ubm Consumptionmentioning

confidence: 99%

Transmission Electron Microscopy Characterization of Ni(V) Metallization Stressed Under High Current Density in Flip Chip Solder Joints

Tsai

Lin

et al. 2010

Journal of Elec Materi

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“…18 It was commented that the porous layer might have a high electrical resistance. 18 In other words, the porous structure resulting from the reaction between Cu-Cr and solder might also have the ability to divert the electrons.…”

Section: The Effect Of Current Crowding and Joule Heatingmentioning

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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Transmission electron microscopy characterization of the porous structure induced by high current density in the flip-chip solder joints

Tsai

Lin

Kao

2009

2009 4th International Microsystems, Packaging, Assembly and Circuits Technology Conference

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Observation of amorphous chromium in modified C4 flip chip solder joints after thermal stress testing

Cited by 3 publications

References 6 publications

Transmission Electron Microscopy Characterization of Ni(V) Metallization Stressed Under High Current Density in Flip Chip Solder Joints

Transmission Electron Microscopy Characterization of Ni(V) Metallization Stressed Under High Current Density in Flip Chip Solder Joints

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

Transmission electron microscopy characterization of the porous structure induced by high current density in the flip-chip solder joints

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