Practical measurement method of relative thermal conductivity of core-shell type composite powder


H. Choi1, M. Moon1 and K. Lee1

1R&D Center of Donghyun Electronics Co., Ltd., Cheongbuk, Pyeongtaek-Si, Korea

Keywords: dual functional
property: EMI absorbing, thermal conductive
material: core shell powder

Recently, as the electronic devices become smaller and slimmer, techniques for heat dissipating solutions became the most noteworthy issues in electronic industry. In general, to transfer heat from heat source to heat sink or ambient air, thermal interface materials have been widely used. These thermal interface materials are composed of polymer based ceramic composite. The ceramic fillers act as heat transferring media and high thermally conductive ceramic fillers such as Al2O3, BN, AlN, SiC are being usually used [1-3]. However, it is quietly difficult to know the thermal conductivity of the powder materials until we manufacture a sheet of powder and polymer composite. In addition, many other circumstantial factors such as powder dispersion, filler content, kind of polymer can affect the thermal conductivity during the sheet manufacturing process. So it became important to know the thermal conductivity of powder itself. Until now, measuring the thermal conductivity of a fine powder is almost impossible except by making a bulk type specimen by hot press process [4]. So in this study, we suggested a practical measurement method to evaluate the thermal conductivity of powder itself. Firstly, we manufactured core shell structured composite powder by dry mixing process. As core materials metal powder such as Al, Cu, Fe alloys were tested. And as shell materials high thermally conductive ceramic powders such as Al2O3, BN were tried. High speed super mixer was used to form homogeneous shell layer on the surface of core powder. Thermal conductivity of core shell powders, raw metal powders and ceramic powders were evaluated by modified hot wire method (ASTM E55 pending) and specially designed fixture. And these values are compared with the tap density of individual materials. It was found that modified hot wire method and its supplementary fixture was very practical to evaluate relative thermal conductivity of powder materials and thermal conductivity of powder materials had a relation to materials’ density.

References
  1. A.D. Kraus, A. Bar-Cohen, Advances in Thermal Modeling of Electronic Component and Systems, Volume 4, ASME Press Series (1998)

  2. P. Lall, M.G. Pecht, E. Halkim, Influence of Temperature on Microelectronics and System Reliability, CRC Press (1997)

  3. M. Ogata et al., J. Appl. Polymer Sci., 48, 583-601 (1993)

  4. S.S. Tonapi, R.A. Fillion, F.J. Schattenmann, An Overview of Thermal Management for Next Generation Microelectronics Devices, IEEEI/SEMI, 250 (2003)

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