Computational study for reliability improvement of a circuit board

Abstract

An electronic device consists of electronic components attached on a circuit board. Reliability of such a device is limited to fatigue properties of the components as well as of the board. Printed circuit board (PCB) consists of conducting traces and vertical interconnect access (via) out of copper embedded in a composite material. Usually the composite material is fiber reinforced laminate out of glass fibers and polyimid matrix. Different reasons play a role by choosing the components of the laminate for the board, one of them is its structural strength and fatigue properties. An improvement of board’s lifetime can be proposed by using computational mechanics.

In this work we present the theory and computation of a simplified one layer circuit board conducting electrical signals along its copper via, producing heat that leads to thermal stresses.

Such stresses are high enough to perform a plastic deformation. Although the plastic deformation is small, subsequent use of the electronic device causes accumulating plastic deformation, which ends the lifetime effected by a fatigue failure in the copper via.

Computer simulations provide a convenient method for understanding the nature of this phenomenon as well as predicting the lifetime. We present a coupled and monolithic way for solving the multiphysics problem of this electro-thermo-mechanical system, numerically, by using finite element method in space and finite difference method in time.