Pb-free Sn/3.5Ag electroplating bumping process and under bump metallization (UBM)

Author

Jang, Se-Young ; Wolf, Juergen ; Ehrmann, Oswin ; Gloor, Heinz ; Reichl, Herbert ; Paik, Kyung-Wook

Author_Institution

Samsung Electron. Co. Ltd., Suwon, South Korea

Volume

25

Issue

3

fYear

2002

fDate

7/1/2002 12:00:00 AM

Firstpage

193

Lastpage

202

Abstract

Pb-free solder is one of the biggest issues in today´s electronic packaging industry. This paper introduces a newly developed Sn/3.5Ag alloy plating process for wafer level bumping. The effects of Under Bump Metallization (UBM) on the process, interfacial reaction, and mechanical strength have been investigated. Four different types of sputtering-based UBM layers-TiW/Cu/electroplated Cu, Cr/CrCu/Cu, NiV/Cu, and TiW/NiV-were fabricated with eutectic Pb/63Sn and Sn/3.5Ag solder. The result shows that the Sn/Ag solder gains Cu or Ni from UBM´s and becomes Sn/Ag/Cu or Sn/Ag/Ni during reflow process. Sn/Ag solder has higher reactivity with Cu and Ni than Pb/63Sn. The Intermetallic Compound (IMC) spalling from the interface between UBM/solder has been observed on Cr/CrCu/Cu and TiW/NiV UBM´s. However, the IMC spalling phenomena did not decrease the bump shear strength with a bump size of 110 μm, whereas a size of 60 μm brought a decrease in shear value and failure mode change.

Keywords

electroplated coatings; electroplating; flip-chip devices; mechanical strength; metallisation; packaging; reflow soldering; silver alloys; tin alloys; 110 micron; 60 micron; Cr-CrCu-Cu; NiV-Cu; Pb-free Sn/3.5Ag electroplating bumping process; Pb-free solder; Sn/3.5Ag alloy plating process; SnAg; SnAgCu; SnAgNi; TiW-Cu; TiW-NiV; TiW/Cu/electroplated Cu; bump shear strength; electronic packaging; eutectic Pb/63Sn; failure mode; flip-chip interconnection; interfacial reaction; intermetallic compound spalling; mechanical strength; reflow process; sputtering-based UBM layers; under bump metallization; wafer level bumping; Adhesives; Chromium; Electronics packaging; Flip chip; Materials science and technology; Metallization; Surface tension; Surface-mount technology; Thermal resistance; Tin;

fLanguage

English

Journal_Title

Electronics Packaging Manufacturing, IEEE Transactions on

Publisher

ieee

ISSN

1521-334X

Type

jour

DOI

10.1109/TEPM.2002.801647

Filename

1158829