Influence of Selected Design Variables on Thermo-Mechanical Stress Distributions in Plated-Through-Hole Structures
S. Bhandarkar, A. Dasgupta, D. Barker, M. Pecht, and W. Engelmaier
Abstract:
Failure of plated-through-holes (PTHs) due to thermomechanical stresses
is a well established cause of failure of multilayer printed wiring boards
(MLBs). This paper uses the finite element method (FEM) to examine the
nature of the stress distribution within the PTH structure when the MLB
is subjected to thermal loads. Guidelines are laid out for realistic modelling
of material properties and boundary conditions in the FEM model. Parametric
studies are conducted to study the qualitative effect of several geometric
parameters on the critical stresses in the PTH. Both traditional glass-epoxy
(FR-4) MLBs and highly anisotropic Kevlar-polymide MLBs are examined. Differences
in behavior observed between the two materials underline the pitfalls in
extending the standard design thumb rules for standard FR-4 MLBs to other
MLB materials. The purpose here is to provide guidelines for the reliable
design of PTHs. Actual fatigue life predictions are deferred to a later
paper.
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