Research Update: Carbon nanotubes suck heat from high-performance amps
By Matthew Miller -- EDN, January 5, 2006
Fujitsu has announced that it will employ carbon nanotubes in heat sinks for high-frequency, high-power amplifiers that will find use in next-generation base stations. Because conventional face-up packaging techniques suffer from amplification-limiting inductance, designers commonly use flip-chip packaging for such amplifiers. However, the metal bumps that connect the amplifiers to their pc boards in the flip-chip approach are proving inadequate for dissipating the heat of high-power transistors, according to the company.
Fujitsu's technology replaces the metal bumps with bundles of vertically oriented carbon nanotubes, grown in a proprietary process using an iron-catalyst coating (Figure). The nanotubes offer thermal conductivity of 1400W/(m-K), compared with 400W/(m-K) for copper. According to Fujitsu, the approach yields heat-dissipation levels equivalent to face-up configurations but halves inductance, which in turn yields at least a 2-dB increase in amplification at frequencies of 5 GHz or greater.
Fujitsu, www.fujitsu.com.
