Thermal Characteristic of Sn-MWCNT Nanocomposite Solder in LED Package

Thermal property is very important in LED lighting and junction temperature due to LED life time and luminous efficiency. An attractive approach to improve the thermal property of the solder joint is application of Multi-wall Carbon Nanotube (MWCNT) due to their outstanding mechanical, electrical and thermal property. However, MWCNTs need process of depositing metal such as Ag, Cu, Pt, Sn and Ni nanoparticle to combine MWCNT with solder. In these materials, Sn is considerable candidate because the predominant composition of lead-free solder alloys is Sn. Various approaches were employed to deposit Sn onto MWCNT. The Polyol method is a synthetic technique with simple, convenient and less energy and material consuming property. However, Sn-MWCNT nanocomposite material has difficulty to fabricate with only using polyol method due to low reduction potential of Sn. Additional process is needed to form well Sn-MWCNT nanocomposite to apply Sn based solder. We investigated Sn-MWCNT composite solder with various content of Sn-MWCNT nanocomposite to application LED package. The MWCNT were reduced with Sn solution using polyol method to form Sn nanoparticle on surface of MWCNT. Subsequently, reducing agent solution were added under magnetic stirring. We investigated effect of additional reducing agent on MWCNT reducing process with various method. The Sn-58Bi solder pastes with various Sn-MWCNT nanocomposite contents were printed on the metal printed circuit boards (MPCBs), followed by bonding with flip-chip bonder. The temperature of LED chip with 0.1 wt.% Sn-MWCNT nanocomposite solder decreased about 3% compared to Sn-58Bi solder.