This paper investigates the void formation mechanism induced by chemical interaction between eutectic solder (Sn63/Pb37) wetting and no-flow underfill material curing during flip chip in package assembly. During the process, low weight molecular components, such as fluxing agents and water molecules, could be induced by the chemical interaction between solder wetting and underfill curing when these components are heated to melt and cure, respectively. The low weight molecular components become volatile with exposure to temperatures above their boiling points; this was found to be the main source of the extensively formed underfill voiding. This mechanism of chemically and thermally induced voids was explained using void formation study, differential scanning calorimetry thermogram comparison, and gas chromatography and mass spectroscopy chemical composition identification on the suggested chemical reaction formula. This finding can enhance understanding of the mechanism that drives no-flow underfill voiding and can develop a void-free flip chip assembly process using no-flow underfill material for cost effective and high performance electronics packaging applications. Furthermore, this study provides the design guideline to develop an advanced no-flow underfill having high performance at high temperature range for the lead-free application.
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September 2009
Research Papers
Void Formation Mechanism of Flip Chip in Package Using No-Flow Underfill
Sangil Lee,
Sangil Lee
The George W. Woodruff School of Mechanical Engineering,
e-mail: gtg647p@mail.gatech.edu
Georgia Institute of Technology
, 771 Ferst Drive, Atlanta, GA 30332
Search for other works by this author on:
M. J. Yim,
M. J. Yim
The George W. Woodruff School of Mechanical Engineering,
Georgia Institute of Technology
, 771 Ferst Drive, Atlanta, GA 30332
Search for other works by this author on:
Daniel Baldwin
Daniel Baldwin
The George W. Woodruff School of Mechanical Engineering,
Georgia Institute of Technology
, 771 Ferst Drive, Atlanta, GA 30332
Search for other works by this author on:
Sangil Lee
The George W. Woodruff School of Mechanical Engineering,
Georgia Institute of Technology
, 771 Ferst Drive, Atlanta, GA 30332e-mail: gtg647p@mail.gatech.edu
M. J. Yim
The George W. Woodruff School of Mechanical Engineering,
Georgia Institute of Technology
, 771 Ferst Drive, Atlanta, GA 30332
Daniel Baldwin
The George W. Woodruff School of Mechanical Engineering,
Georgia Institute of Technology
, 771 Ferst Drive, Atlanta, GA 30332J. Electron. Packag. Sep 2009, 131(3): 031014 (5 pages)
Published Online: July 31, 2009
Article history
Received:
March 25, 2009
Revised:
April 18, 2009
Published:
July 31, 2009
Citation
Lee, S., Yim, M. J., and Baldwin, D. (July 31, 2009). "Void Formation Mechanism of Flip Chip in Package Using No-Flow Underfill." ASME. J. Electron. Packag. September 2009; 131(3): 031014. https://doi.org/10.1115/1.3153369
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