PWB In-plane Motion Under Vibration Loading

K. Huang, D. Barker
Point of Contact: dbarker@calce.umd.edu

Objective

Extend the current vibration analysis programs in the CALCE software to calculate the in- plane motion of a printed wiring board (PWB) subjected to vibratory loading.

Background

Vibration induced wear is a concern with PCB card edge connectors, which are generally designed to withstand the wear associated with relatively few insertion / extraction cycles, -- generally, fewer than 100 -- but not the large number of cycles that could occur as a result of vibratory motion.

Two types of in-plane vibratory motion can cause connector wear: motion due to rigid body translations, and in-plane motion due to resonant out-of-plane deformation of the PCB. This project is concerned only with the resonant in-plane motion due to the out-of- plane deformation of the PCB.

The CALCE vibration finite element analysis (FEA) programs are optimized to determine the first three mode shapes of a PWB, and then to calculate the dynamic response of the PWB under a prescribed acceleration loading. The program cannot determine the PWB in- plane motions directly due to the assumption that there is no in-plane motion at any imposed boundary condition, that is, at any imposed edge condition or at any interior point where a boundary condition has been specified.

Approach

Use the calculated out-of-plane response of the PWB in the current software to estimate the in-plane motion.

Work Accomplished

The accuracy and range of use of the approximate algorithm for computing in-plane displacement has been determined by comparing the results to solutions solved with a detailed FEA using a geometric non linear general purpose code (P/FEA).

The code for calculating the in-plane motion has been extended and improved to allow the user to specify the fixed of free boundary conditions in the two in-plane directions along any node line or at any node point. An algorithm modification has also been made to improve the determination of the zero in-plane displacement line of a vibrating PWB.

The effect of edge friction on the in-plane displacement has been investigated numerically and been found to be negligible for typical edge card connectors.