Thermal Materials Solve Power Electronics Challenges

Feb 1, 2006 12:00 PM
By Carl Zweben, Ph.D., Advanced Thermal Materials Consultant, Devon, Pa.

The Future

We are in the early stages of a thermal management materials revolution. Al/SiC, the first second-generation thermal material, was only developed about two decades ago. Historically speaking, this is barely the blink of an eye. Most of the new high-performance third-generation materials have been commercialized within the last few years. Based on this perspective, it seems reasonable to expect that in the future there will be significant developments in both materials and processes, leading to improved thermal properties and reduced costs.

Decreasing cost will stimulate further use of these materials in an increasing number of microelectronic, optoelectronic and MEMS applications. One significant barrier is the general lack of awareness of advanced materials among packaging engineers. However, the successful use of diamond particle-reinforced SiC composites in commercial servers suggests that other diamond-reinforced composites merit consideration.

One intriguing area of interest is nanocomposites. Estimates of carbon nanotube thermal conductivity run as high as 6600 W/m-K. Values more than 3000 W/m-K have been measured. Graphite nanoplatelets, which are much cheaper than nanotubes, are another candidate for nanoscale reinforcement, as are nanoparticles of diamond and other thermally conductive materials. While the small size of nanoscale reinforcements results in a large number of interfaces that reduce thermal efficiency, they are certainly worth exploring. It may well be that nanoreinforcements can be used with other reinforcements, such as thermally conductive carbon fibers, to produce hybrid composites with attractive properties. Other potential advantages of nanocomposites are reduced CTE and increased stiffness.

As previously discussed, composite solders with low CTEs are now under development. Combined with the materials discussed in this article, the packaging engineer will have the ability to match thermal expansions throughout the package, improving manufacturing yield, reliability and performance. Because of the unique ability of this and other advanced thermal management materials to meet future packaging requirements, I anticipate that they will play an increasingly important role in the 21^st century.

Acknowledgements

Some of the data in this paper were taken from the following publications, and appear courtesy of the publishers: Kelly, A., and Zweben, C., Editors-in-Chief. Comprehensive Composite Materials, Pergamon Press, Oxford, 2000; Zweben, C. “Composite Materials And Mechanical Design,” Mechanical Engineers' Handbook, Book 1: Materials and Mechanical Design, Third Edition, Myer Kutz, Ed, John Wiley & Sons Inc., New York, 2005.

Zweben, C. “Metal Matrix Composites, Ceramic Matrix Composites, Carbon Matrix Composites and Thermally Conductive Polymer Matrix Composites,” Chapter 5, Handbook of Plastics, Elastomers and Composites, Fourth Edition, A. Harper, Editor-in-Chief, McGraw-Hill, New York, 2002.

References

1. Strand, S.D. “Future Technology in the Global Market,” Power Systems World, Oct. 23-27, 2005.

2. Markoff, J. “Intel's Big Shift After Hitting Technical Wall,” New York Times, May 17, 2004.

3. “Burned Groin Blamed on Laptop,” BBC News World Edition, Nov. 22, 2002.

4. Zweben, C. and Schmidt, K.A. “Advanced Composite Packaging Materials,” Electronic Materials Handbook, ASM International, 1989.

5. Lasance, C. J. M. “Problems with Thermal Interface Material Measurements: Suggestions for Improvement,” Electronics Cooling, November 2003.

6. Fleming, T.F.; Levan, C.D.; and Riley, W.C. “Applications for Ultra-High Thermal Conductivity Fibers,” Proceedings of the 1995 International Electronic Packaging Conference, International Electronic Packaging Society, pp. 493-503.

7. Norley, J. “Natural Graphite Based Materials for Electronics Cooling,” Proceedings of the IMAPS Advanced Technology Workshop on Thermal Management, Oct. 25-27, 2004.

8. Zweben, C. “Electronic Packaging: Heat Sink Materials,” Encyclopedia of Materials: Science and Technology, Vol. 3, 2001, pp. 2676-83.

9. Thaw, J.; Zemany, J.; and Zweben, C. “Metal Matrix Composites for Microwave Packaging Components,” Electronic Packaging and Production, August 1987, pp. 27-29.

Click here for the enhanced PDF version of this article