Jul 3, 2008
CNTs take the heat out of LEDs
Carbon nanotube thermal interface material (CNT-TIM) has come out ahead in a study by scientists in China. HB-LEDs that were heat sink coupled using CNT-TIM displayed a linear optical response over the input current range 150–900 mA compared with devices configured using commercial TIM, which peaked at 700 mA.
The efficiency, reliability and colour of solid-state lighting devices depend strongly on successful thermal management of the package. Here, carbon nanotubes have a lot to offer thanks to the material's superior thermal properties.
Using an industry standard test set-up, the group found that the average thermal resistance of its CNT-TIM was just 7 mm2 K W–1. For comparison, direct attachment (no TIM) gave a thermal resistance of 107 mm2 K W–1, the use of commercial silver epoxy TIM produced a value of 75 mm2 K W–1 and even a more advanced metal system could only manage 24 mm2 K W–1.
The team's interface material consists of aligned carbon nanotube arrays fabricated on a silicon substrate by microwave plasma-enhanced chemical vapour deposition.
"The film is robust and our sample can withstand at least 0.2 MPa without collapse, which is enough for electronic packaging applications," Kai Zhang of the Hong Kong University of Science and Technology told nanotechweb.org.
Back in the lab, the group is looking to further enhance the thermal performance of the package by improving the bonding between the TIM and the mating surfaces.
The researchers presented their work in Nanotechnology.
About the author
James Tyrrell is editor of nanotechweb.org.