NASA

Metal Whiskers from Sn-Ag-Cu Alloy Systems

The following images and technical information are posted with permission of the authors:
 
"Tin Whiskers with Special Morphology" 
Yaowu Shi and Hu Hao
haohu@emails.bjut.edu.cn
The Beijing University of Technology
July 2008

Rapid tin whisker growth on the surface of Sn-3.8Ag-0.7Cu-1.0Ce/Er/Y* solder joints has been investigated. The results show that, besides the regular pencil-shaped whiskers, spiral tin whisker; plate-like whisker; bent whiskers with many continuous kinks; tin whisker with a non-constant cross section; branch-type tin whisker and joining-type tin whisker were also found in our study. These tin whiskers are shown as follows:

* Sn = Tin Ag = Silver Cu = Copper
  Ce = Cerium Er = Erbium Y = Yttrium

 1.      Spiral tin whisker and distorted tin whisker


Storage at room temperature in air for 720hr, on the surface of CeSn3 phase


Storage at room temperature in air for 820hr, on the surface of CeSn3 phase

2.      Irregular plate-like tin whisker and regular ribbon-like tin whisker  


Storage at 125
C in air for 20min, then at room temperature for 260hr, on the surface of ErSn3 phase


Storage at 150
C in air for 20min, on the surface of ErSn3 phase

 


3.      Tin whiskers with non-constant cross section  

Storage at 150C in air for 20min, on the surface of ErSn3 phase

 
Storage at room temperature in air for 312hr,
on the surface of ErSn3 phase

4.      Branch-type tin whiskers


Storage at room temperature in air for 312hr, on the surface of CeSn3 phase


Storage at 150C in air for 20min,
on the surface of ErSn3 phase

5.      Tin whisker with a joint  


Storage at room temperature in air for 312hr,
on the surface of CeSn3 phase

 
Responsible NASA Officials:

   Michael Sampson/NASA GSFC Code 306
   Dr. Henning Leidecker/NASA GSFC Code 562
Additional Researchers: 

   Jong Kadesch/Orbital Sciences Corp.
   Jay Brusse/Perot Systems

Last Updated:

July 14, 2008

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