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Technical Brief

Micro Copper Pillar Interconnection Using Thermosonic Flip Chip Bonding

[+] Author and Article Information
Bo Wu, Shuanghai Zhang

State Key Laboratory of High Performance
Complex Manufacturing,
School of Mechanical and Electrical Engineering,
Central South University,
Changsha 410083, HN Province, China

Fuliang Wang

State Key Laboratory of High Performance
Complex Manufacturing,
School of Mechanical and Electrical Engineering,
Central South University,
Changsha 410083, HN Province, China
e-mail: wangfuliang@csu.edu.cn

Zhuo Chen

State Key Laboratory of High Performance
Complex Manufacturing,
School of Mechanical and Electrical Engineering,
Central South University,
Changsha 410083, HN Province, China
e-mail: zhuochen@csu.edu.cn

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received February 28, 2018; final manuscript received July 4, 2018; published online August 6, 2018. Assoc. Editor: Jin Yang.

J. Electron. Packag 140(4), 044502 (Aug 06, 2018) (5 pages) Paper No: EP-18-1015; doi: 10.1115/1.4040794 History: Received February 28, 2018; Revised July 04, 2018

The incorporation of a micro copper pillar is considered as the major interconnection method in three-dimensional (3D) integrated circuit (IC) intergradation under high-density I/O conditions. To achieve low-temperature bonding, this study investigated the thermosonic flip chip bonding of a copper pillar with a tin cap. The effect of bonding force on bonding strength was studied, and an average bonding strength 2500 g (approximately 84.8 MPa) was obtained in 2 s, at an optimized bonding force of 0.11 N per 40 μm pillar bump, and substrate temperature of 200 °C. Additionally, the effect of the bonding force on bonding interface microstructure and intermetallic compounds (IMCs) was also investigated. Tin whiskers were also observed at the bonding interface at low bonding forces.

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References

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Figures

Grahic Jump Location
Fig. 1

Structure and interfaces present in TSFC bonding

Grahic Jump Location
Fig. 2

Layout of bumps on (a) flip chip and (b) substrate

Grahic Jump Location
Fig. 3

Scanning electron microscope of copper pillar on (a) flip chip and (b) on substrate

Grahic Jump Location
Fig. 4

Die shear force test curve

Grahic Jump Location
Fig. 5

Effect of bonding force on die shear force

Grahic Jump Location
Fig. 6

Effect of bonding force on bonding interface microstructure: (a) 7 N, (b) 10 N, (c) 13 N, (d) 16 N, (e) 19 N, (f) 25 N, and (g) 30 N

Grahic Jump Location
Fig. 7

Effect of bonding force on the formation of Sn whisk: (a) 7 N, (b) 13 N, and (c) 19 N

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