Formation of Sn-multiwalled carbon nanotube composite layer for the application of thermal interface materials

Fabrication of Sn-MWCNT composite layer through reflow of Sn-decorated MWCNT powder was conducted in this study. Commercially available MWCNTs were oxidized by using K
2
Cr
2
O
7
/ H
2
SO
4
solution for the surface modification. The oxidized MWCNTs were dispersed in SnCl
2
/ HCl solution and subsequently a reducing agent NaBH
4
was introduced to form crystalline Sn. During the Sn reduction process, 1,10-phenanthroline capping agent was introduced to control the particle shape and size. It was found that SnO
2
nanoparticles on the surface of MWCNTs and crystalline Sn particles were obtained simultaneously through the chemical reduction reaction. When 1,10-phenanthroline was used, Sn particles had spherical shape and uniform size compared to the one without 1,10-phenanthroline. Afterwards, the Sn-MWCNT powders were mixed with a flux to form a paste for a wetting test on a Cu substrate. After a reflow step of the paste, Sn-MWCNT composite layer could be formed showing no separation between MWCNTs and Sn by bonding of molten Sn to SnO
2
nanoparticles on the surface of MWCNTs.