Effects of Rare-Earth Addition on Properties and Microstructure of Lead-Free Solder Balls |
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Authors: | Yang Yu Zhidong Xia Fu Guo Yaowu Shi |
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Affiliation: | (1) School of Materials Science and Engineering, Beijing University of Technology, Beijing, 100124, China |
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Abstract: | In the present work, lead-free solder balls were manufactured by a uniform droplet spray (UDS) method. The solder used to
produce solder balls was based on the Sn-3.8Ag-0.7Cu alloy. Different amounts of cerium-based mixed rare-earth (RE) elements
were added into the Sn-3.8Ag-0.7Cu solder alloy in order to examine the effects of small amounts of RE additions on the physical
properties, microstructure, and surface smoothness of the solder balls. Results show that a small amount of RE addition has
no obvious effect on the melting temperature, but it decreases the nucleation undercooling degree. Moreover, a small amount
of RE addition (<0.25 wt.%) can improve the surface smoothness of the solder balls. However, when the RE was added up to 0.5 wt.%,
the surface smoothness of the solder balls was deteriorated. From observations of the microstructure of the solder balls,
it is obvious that the RE addition affects solidification behavior, and as a result, the surface smoothness of the solder
balls. |
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Keywords: | Lead-free solder ball rare-earth element uniform droplet spray (UDS) |
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