Electromigration performance of printed Sn0.7Cu bumps with immersion tin surface finishing for flip chip applications

Author

Kuo, Kuei Hsiao ; Lee, Jason ; Chen, Stan ; Chien, F.L. ; Lee, Rick ; Lau, John

Author_Institution

Wafer Bumping Product Dev. Dept., Siliconware Precision Ind. Co., Ltd. (SPIL), Taichung, Taiwan

fYear

2012

fDate

May 29 2012-June 1 2012

Firstpage

698

Lastpage

702

Abstract

In this study, the electromigration (EM) performance of the low cost printed Sn0.7Cu bumps assembled with commonly used immersion tin (IT) surface finished substrate for flip chip application is investigated and compared to the printed EU bumps. The EM experimental measurement and analysis results show the t50 life of printed SnCu0.7 solder joint is 3X better than that printed eutectic SnPb solder joint under 150°C -500mA condition. Two EM failure mechanisms of SnCu0.7 solder joint are observed. One is void formation at current crowding area and crack propagation through Under Bump Metallurgy (UBM) intermetallic (IMC). The other is UBM and IMC depletion when test temperature is increased to 150°C and 160°C; and solder extrusion through the depletion area is found. The effective activation energy for printed SnCu0.7 solder is 1.20 and the exponent associated with current density is 1.47. The reference design suggestions for EM reliability of printed SnCu0.7 solder joint with immersion tin surface finish are provided in this study.

Keywords

copper alloys; cracks; current density; electromigration; failure analysis; flip-chip devices; reliability; solders; surface finishing; tin alloys; voids (solid); EM experimental measurement; EM failure mechanisms; EM performance; EM reliability; Sn; SnCu; UBM IMC; crack propagation; current -150 mA; current crowding area; current density; effective activation energy; electromigration performance; flip chip applications; immersion tin surface finishing substrate; low cost printed bumps; printed EU bumps; reference design; solder extrusion; temperature 150 degC; that printed eutectic solder joint; under bump metallurgy intermetallic; void formation; Electromigration; Failure analysis; Nickel; Ovens; Soldering; Surface finishing; Tin;

fLanguage

English

Publisher

ieee

Conference_Titel

Electronic Components and Technology Conference (ECTC), 2012 IEEE 62nd

Conference_Location

San Diego, CA

ISSN

0569-5503

Print_ISBN

978-1-4673-1966-9

Electronic_ISBN

0569-5503

Type

conf

DOI

10.1109/ECTC.2012.6248908

Filename

6248908