Formation mechanism of Sn-patch between SnAgCu solder and Ti/Ni(V)/Cu under bump metallization

Wang, Kai-Jheng; Tsai, Yu‐Zen; Duh, Jenq‐Gong; Shih, T. I.

doi:10.1557/jmr.2009.0315

Cited by 6 publications

(10 citation statements)

References 18 publications

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“…1 of Ref. 16. In the following, conventional TEM, STEM, and HRTEM characterization of the consumed Ni(V) and porous structure microstructures are presented.…”

Section: Resultsmentioning

confidence: 99%

“…The observation that V was immobile and Ni diffused out from Ni-V alloys has been reported in the literature. [9][10][11][12][13][15][16][17][18][19][20][21] …”

Section: Stem Line Scan Analysesmentioning

confidence: 99%

“…It should be noted that the consumption of Ni(V) UBM during thermal treatments without an applied current has been studied extensively. [9][10][11][12][13][14][15][16][17] The interfacial reactions between Ni-V alloys and Sn-based solders have also been investigated by many research groups. [18][19][20][21][22] …”

Section: Introductionmentioning

confidence: 99%

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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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“…1 of Ref. 16. In the following, conventional TEM, STEM, and HRTEM characterization of the consumed Ni(V) and porous structure microstructures are presented.…”

Section: Resultsmentioning

confidence: 99%

“…The observation that V was immobile and Ni diffused out from Ni-V alloys has been reported in the literature. [9][10][11][12][13][15][16][17][18][19][20][21] …”

Section: Stem Line Scan Analysesmentioning

confidence: 99%

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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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“…Sn-patch was observed in the Ni(V) layer after reflow, in agreement with the literature report. [8][9][10][11][12][13] The area ratio of Sn-patch to the Ni(V) layer was around 13.2% in the Sn-Ag-Cu/UBM 05 solder joint after reflow, and increased to 14.1% after aging for 1000 h due to interdiffusion of Ni and Sn (Fig. 3b).…”

Section: Methodsmentioning

confidence: 99%

“…[3][4][5][6][7][8][9][10][11][12][13] Recently, it was revealed that the Sn-patch consists of an amorphous Sn phase and crystalline V 2 Sn 3 , and a mechanism for its formation was proposed. 11 However, there is little literature concerning the relationship between Sn-patch and solder joint reliability. Zheng et al 12 reported that the fracture surface of Sn-3.5Ag-1.0Cu solder joints with Ti/Ni(V)/Cu UBM became brittle after 30 reflows.…”

Section: Introductionmentioning

confidence: 99%

Impact Testing of Sn-3.0Ag-0.5Cu Solder with Ti/Ni(V)/Cu Under Bump Metallization After Aging at 150°C

Wang

Duh

Sykes³

et al. 2010

Journal of Elec Materi

Self Cite

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Nonmagnetic Ni(V) metal and low consumption rate with solders are the advantages of sputtered Ti/Ni(V)/Cu under bump metallization (UBM). However, a Sn-rich phase (''Sn-patch'' herein) can form in the Ni(V) layer after reflow and aging. In lead-free solder, Sn-patches form and grow more quickly than in Sn-Pb solder. Thus, the effect of Sn-patches on solder joint reliability becomes critical. In this study, Sn-3.0Ag-0.5Cu solder was reflowed with Ti/Ni(V)/Cu UBM at 250°C for 60 s, and then aged at 150°C for various durations. A high-speed impact test was introduced to evaluate solder joint reliability. After impact testing, it was found that, the larger the Sn-patch, the greater the propensity of the solder joint to suffer brittle fracture. The correlation between Sn-patch and solder joint reliability is discussed.

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Al/Ni : V/Ag metal stacks as rear‐side metallization for crystalline silicon solar cells

Jung

Köntges

2012

Progress in Photovoltaics

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Rear sides of crystalline silicon solar cells are usually covered with aluminum on which it is difficult to solder. To ease soldering, we present a durability study for a Ni : V/Ag stack on evaporated Al as rear‐side metallization. We adapt this cost‐effective metallization stack from the microelectronic industry and investigate it as metallization for silicon solar cells. Here, a long‐term stability of the metallization and of the solder joint must be guaranteed for 25 years and is therefore evaluated in detail by thermal aging experiments. During this experiment, the mechanical stability of the solder joints is measured. The chemical stability and the intermetallic compound (IMC) growth within the solder joints are examined by secondary electron microscopy, backscattered electron imaging, and energy dispersive X‐ray analysis. Experiments with either a Sn–Ag‐coated copper tab or pure Sn–Ag solder show two different sorts of IMCs at the Ni : V/Solder interface. With the copper tab, a Cu–Ni–Sn compound, presumably (Cu1 ‐ xNix)6Sn5, grows at the Ni/solder interface, whereas in case of a pure Sn–Ag solder, a Ni–Sn compound grows, which is likely to be Ni3Sn4. Analysis of the reaction kinetics leads to activation energies of 77 and 42 kJ/mol, respectively, for a diffusion‐controlled IMC growth. By using temperature histograms of PV modules in the field, the necessary minimum Ni : V layer thickness is estimated: without a copper tab up to 1.6 µm Ni and with a copper tab less than 0.2 µm may be consumed by IMC formation during 25 years of lifetime. Copyright © 2012 John Wiley & Sons, Ltd.

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Formation mechanism of Sn-patch between SnAgCu solder and Ti/Ni(V)/Cu under bump metallization

Cited by 6 publications

References 18 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

Impact Testing of Sn-3.0Ag-0.5Cu Solder with Ti/Ni(V)/Cu Under Bump Metallization After Aging at 150°C

Al/Ni : V/Ag metal stacks as rear‐side metallization for crystalline silicon solar cells

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