RESEARCH PAPERS: Properties and Property Measurements

Thermal Conductivity Measurements in Printed Wiring Boards

[+] Author and Article Information
J. E. Graebner

Lucent Technologies, Bell Laboratories, 600 Mountain Avenue, PO Box 636, Murray Hill, NJ 07974-0636

K. Azar

Lucent Technologies Inc., Bell Laboratories, North Andover, MA 01845

J. Heat Transfer 119(3), 401-405 (Aug 01, 1997) (5 pages) doi:10.1115/1.2824111 History: Received April 15, 1996; Revised April 11, 1997; Online December 05, 2007


The effective thermal conductivity κ of multilayer printed wiring boards (PWBs) has been measured for heat flowing in a direction either parallel (κ∥ ) or perpendicular (κ⊥ ) to the plane of the board. The conductivity of the glass/epoxy insulating material from which the boards are manufactured is anisotropic (κ∥ ge ≈ 3 × κ⊥ ge ) and nearly three orders of magnitude smaller than the conductivity of copper. This large difference between glass/epoxy and copper produces extremely high anisotropy in PWBs that contain continuous layers of copper. For such boards, values of the board-averaged conductivity in the two directions can differ by a factor of ~100 or more. The value of κ∥ is found to depend on the ratio of the total thickness of continuous layers of copper to the total thickness of glass/epoxy, while it depends hardly at all on the amount of copper circuitry visible on the surface.

Copyright © 1997 by The American Society of Mechanical Engineers
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