Browsing by Author "Jiang, Don Son"

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Effect of Sn grain orientation and strain distribution in 20-mu m-diameter microbumps on crack formation under thermal cycling tests
(2017-11-01)
Chu, Yi-Cheng
;
Chen, Chih
;
Kao, Nicholas
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Jiang, Don Son
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材料科學與工程學系
The thermo-mechanical properties of microbumps serving as interconnects between Si chips in three-dimensional integrated circuits were examined in this study. Arrays of SnAg microbumps were subjected to temperature cycling tests up to 2500 cycles. Extensive cracks formed in the microbumps, and some of them propagated across the entire microbump. A microstructural analysis by electron back scattering diffraction indicated that the cracks propagated along two paths: Sn grain boundaries with high misorientation angles and SnAg/Ni3Sn4 interfaces. The average Sn grain size was only 7.4 mu m, implying a large proportion of grain boundaries per unit volume, which facilitated crack propagation across the microbump of 20 mu m in diameter.
Nanomechanical properties of Ag solder bumps doped with Pd and Au
(2017-12-01)
Wen, Hua-Chiang
;
Chou, Wu-Ching
;
Lin, Shiuan Huei
;
Jiang, Don Son
;
電子物理學系
As an approach to increasing their reliability, we doped Ag solder bumps with Pd and Au alloys to enhance their creep resistance, which we characterized using a nanoindentation technique. The hardnesses of the pure Ag and the Ag solders doped with Pd:3%, Pd:5%, and Pd:2%-Au:3% were 0.6 +/- 0.1, 1.8 +/- 02, 2.8 +/- 03, and 3.1 +/- 0.5 GPa, respectively. Although the hardness of the Ag solder was enhanced significantly when it contained Pd:2%-Au:3%, it exhibited a lower creep exponent (n > 2). The mechanism of the thermal recovery of the sample appears to be associated with activation of dislocation sources-also the reason for the decrease in hardness. The compounds doped with Pd:2%-Au:3% displayed significantly greater bond strengths and creep exponents, whereas the Pd only compounds exhibited poorer reliability. (C) 2017 Elsevier Ltd. All rights reserved.
Using nanoindentation to investigate the temperature cycling of Sn-37Pb solders
(2017-11-01)
Wen, Hua-Chiang
;
Chou, Wu-Ching
;
Lin, Po-Chen
;
Jeng, Yeau-Ren
;
Chen, Chien-Chang
Using nanoindentation and energy dispersive X-ray spectrometry (EDS), we have conducted an investigation into corner failures to elucidate not only the nanomechanical properties of Sn-37Pb solder balls but also the effects of temperature cycling tests (TCTs). We found that the hardness of Sn-37Pb solder balls was greater in central locations [1.18 +/- 0.05 GPa for room-temperature (RT) sample; 1.3 +/- 0.05 GPa for TCT sample], but had standard values in corner locations (>0.2 +/- 0.02 GPa). The modulus increased after the TCTs. Nevertheless, the mechanical properties were closely related to the average area of the alpha-Pb phase. The average area of the Pb-rich region was more stable after the TCTs than that of the RT sample, due to the enhanced mechanical properties of the Sn-37Pb solder, suggesting good reliability. From an analysis of average areas in the RT sample, it appears that the Pb-rich solid solution that formed led to weak Sn-Pb bonds near the corner locations. Electron back scattered diffraction measurements revealed that grains with grain boundaries formed as a result of accelerated TCT cycling. We conclude that Sn-Pb recrystallization was initiated and propagated after the TCTs, followed by propagation to the interfacial region. (C) 2017 Published by Elsevier Ltd.