Microstructural evolution of Sn-Zn based lead free solders after temperature and humid atmosphere exposure

Author

Sun, Peng ; Andersson, Cristina ; Wei, Xicheng ; Cheng, Zhaonian ; Shangguan, Dongkai ; Liu, Johan

Author_Institution

Sino-Swedish Microsystem Integration Technol. Centre, Shanghai Univ.

fYear

2005

fDate

27-29 June 2005

Firstpage

1

Lastpage

6

Abstract

The Sn-Zn based lead free solders appear to be an attractive alternative with a melting temperature that is relatively close to eutectic Sn-Pb. The addition of bismuth improves wettability of Sn-Zn alloy and aluminum is found to improve the oxidation resistance of the eutectic Sn-Zn solder. The objective of this study is to explore the degradation of Sn-Zn system solders after temperature and humid atmosphere exposure. Three kinds of Sn-Zn system solders (Sn-9Zn, Sn-8Zn-3Bi and Sn-7Zn-Al(30ppm)) were soldered on copper pad with a layer of Au/Ni and the specimens were stored in 120 degC/100% relative humidity for 96 hours or 192 hours in a pressure cooker. Zn diffused to the surface and interface while coarsening at the same time. The coarser Zn had weak interface with p-Sn matrix and oxidation was formed. The mechanical fatigue test was carried in a displacement-controlled mode and the results show that high temperature humidity exposure decreases the mean life of Sn-Zn system solder joints when they are subjected to 120degC and 100% relative humidity for 192 hours after the pressure cooker test

Keywords

aluminium; bismuth; environmental degradation; fatigue testing; oxidation; solders; tin alloys; wetting; 192 hours; 96 hours; Al; Bi; SnZn; displacement controlled mode; humid atmosphere exposure; lead free solders; mechanical fatigue test; melting temperature; microstructural evolution; oxidation resistance; pressure cooker test; temperature exposure; wettability; Atmosphere; Bismuth; Environmentally friendly manufacturing techniques; Humidity; Lead; Life testing; Oxidation; System testing; Temperature; Zinc;

fLanguage

English

Publisher

ieee

Conference_Titel

High Density Microsystem Design and Packaging and Component Failure Analysis, 2005 Conference on

Conference_Location

Shanghai

Print_ISBN

0-7803-9292-2

Electronic_ISBN

0-7803-9293-0

Type

conf

DOI

10.1109/HDP.2005.251397

Filename

4017438