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.

Issue Section:
Properties and Property Measurements
Keywords:
Conduction, Measurement Techniques, Thermal Packaging
Topics:
Printed circuit boards, Thermal conductivity, Copper, Epoxy adhesives, Epoxy resins, Glass, Anisotropy, Lumber, Heat, Heat conduction, Insulation, Packaging
1.
Agarwal
 
R. K.
,
Dasgupta
 
A.
,
Pecht
 
M.
, and
Barker
 
D.
,
1991
, “
Prediction of PWB/PCB Thermal Conductivity
,”
Int. J. for Hybrid Microelectronics
, Vol.
14
, pp.
83
–
95
.
2.
Azar, K., and Graebner, J. E., 1996, “Experimental Determination of Thermal Conductivity of Printed Wiring Boards,” Proceedings of the IEEE Semiconductor Thermal Measurement and Management Symposium, (SEMI-THERM), Austin, TX, March 5-7, pp. 169–182.
3.
Azar, K., and Yuan, T. D., 1993, “Effect of Board Conductivity and Air Velocity on Heat Transfer from an Electronic Component,” Proceedings of the Winter Conference of the ASME, New Orleans, LA.
4.
Carslaw, H. S., and Jaeger, J. C., 1959, Conduction of Heat in Solids, 2nd ed. Clarendon, Oxford, p. 21.
5.
Ellison, G. N., 1996, “Thermal Analysis of Circuit Boards and Microelectronic Components Using an Analytical Solution to the Heat Conduction Equation,” Proceedings of the IEEE Semiconductor Thermal Measurement and Management Symposium, (SEMI-THERM), Austin, TX, March 5-7, pp. 144–150.
6.
Graebner
 
J. E.
,
1995
, “
Thermal Conductivity of Printed Wiring Boards
,”
Electronics Cooling
, Vol.
1
, p.
27
27
.
7.
Graebner
 
J. E.
,
Reiss
 
M. E.
,
Seibles
 
L.
,
Hartnett
 
T. M.
,
Miller
 
R. P.
, and
Robinson
 
C. J.
,
1994
, “
Phonon Scattering in Chemical-Vapor-Deposited Diamond
,”
Phys. Rev. B
, Vol.
50
, pp.
3702
–
3713
.
8.
Lemczyk
 
T. F.
,
Mack
 
B. L.
,
Culham
 
J. R.
, and
Yovanovich
 
M. M.
,
1992
, “
PCB Trace Thermal Analysis and Effective Conductivity
,”
ASME JOURNAL OF ELECTRONIC PACKAGING
, Vol.
114
, pp.
413
–
419
.
9.
Maglic, K. D., Cezairliyan, A., and Peletsky, V. E., 1984, eds., Compendium of Thermophysical Property Measurement Methods, Vol. I, Plenum Publishing Corp., New York.
10.
Robinson, P., and Mravic, B., 1996, “Use of a One-dimensional Heat Flow Model to Calculate Circuit Board Thermal Resistance for use in the MQUAD Package Thermal Model,” Proceedings of the IEEE Semiconductor Thermal Measurement and Management Symposium, (SEMI-THERM), Austin, TX, March 5-7, pp. 191–200.
11.
Sarvar
 
F.
,
Poole
 
N. J.
, and
Witting
 
P. A.
,
1990
, “
PCB Glass-Fibre Laminates: Thermal Conductivity Measurements and Their Effect on Simulation
,”
Journal of Electronic Materials
, Vol.
19
, pp.
1345
–
1350
.
12.
Stefani
 
G. G.
,
Goel
 
N. S.
, and
Jenks
 
D. B.
,
1993
, “
An Efficient Numerical Technique for Thermal Characterization of Printed Wiring Boards
,”
ASME JOURNAL OF ELECTRONIC PACKAGING
, Vol.
115
, pp.
366
–
371
.
13.
Vanlaer, H. J. L., and Lasance, C. J. M., 1994, “An Experimental Method to Determine the Effective Thermal Conductivity of Printed Circuit Boards,” in: Thermal Management of Electronic Systems, C. J. Hoogendoorn, R. A. W. M., Henkes, and C. J. M. Lasance, eds., Proceedings of EUROTHERM Seminar 29, Delft, The Netherlands, pp. 201–210.
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