Research Papers

Interfacial Compounds Characteristic and Its Reliability Effects on SAC305 Microjoints in Flip Chip Assemblies

[+] Author and Article Information
Ye Tian

School of Mechanical and Electrical Engineering,
Henan University of Technology,
Zhengzhou 450001, China;
School of Materials Science and Engineering,
HuaZhong University of Science and Technology,
Wuhan 430074, China
e-mail: yetian27@163.com

Ning Ren, Xiaoxia Jian, Tie Geng

School of Mechanical and Electrical Engineering,
Henan University of Technology,
Zhengzhou 450001, China

Yiping Wu

School of Materials Science and Engineering,
HuaZhong University of Science and Technology,
Wuhan 430074, China

1Corresponding author.

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received January 28, 2018; final manuscript received May 12, 2018; published online June 11, 2018. Assoc. Editor: Jin Yang.

J. Electron. Packag 140(3), 031007 (Jun 11, 2018) (5 pages) Paper No: EP-18-1009; doi: 10.1115/1.4040298 History: Received January 28, 2018; Revised May 12, 2018

This study mainly focuses on site effects of the Ni pad interface on intermetallic compounds (IMCs) characteristic during assembly reflowing, and attempts to provide a reasonable explanation for this particular finding. Besides, the changes of the resulting IMCs characteristic are characterized during thermal shock (TS) cycling, and their potential influences on thermal–mechanical reliability of microjoints are evaluated experimentally and numerically. The results show that the site on the Ni pad interface of silicon chip has great influence on interfacial reaction products, i.e., interfacial IMCs. After bumps soldering, a great amount of larger diamond-shaped (Cu, Ni)6Sn5 compounds were densely packed at the edge region, while some smaller ones were only scattered at the center region. Moreover, substantial particle-shaped (Ni, Cu)3Sn4 compounds as well as some rod-shaped ones emerged at the spaces between the (Cu, Ni)6Sn5 compounds of the center region. More importantly, such site effects were remained in the microjoints during TS cycling, which induced the formation of larger protruding (Cu, Ni)6Sn5 compounds. Finite element (FE) simulation results showed that the stress was mainly concentrated at the top of the protruding (Cu, Ni)6Sn5 compounds, which can be a critical reason to cause the crack occurrence. Furthermore, the underlying mechanism of the interfacial IMCs characteristic induced by the site effects was attempted to propose during bumps soldering.

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Fig. 1

Top view of microsolder bumps image after bumps soldering

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Fig. 2

Two-dimensional geometric model of flip chip assembly

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Fig. 3

Finite element model of a corner solder joint with interfacial IMCs in flip chip assembly

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Fig. 4

Cross-sectional BSE images of the interfacial IMC layers after bumps soldering: (a) entire microbump; (b) magnified image near the Ni pad

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Fig. 5

Top-view images of interfacial IMC layers at Ni pad interface after bumps soldering: (a) entire pad; (b) magnified edge region; and (c) magnified center region

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Fig. 6

Cross-sectional BSE image of a corner microjoint after 2000 TS cycles

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Fig. 7

Accumulated inelastic strain energy density contour of a corner joint with the IMCs after four cycles

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Fig. 8

Crack occurrence at the (Cu, Ni)6Sn5 protruding interface of a corner microjoint after 3000 cycles

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Fig. 9

Accumulated inelastic strain energy density contour of a corner microjoint without the IMCs after four cycles



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