Random Vibration Analysis of a Printed Wiring Board with Electronic Components

Abstract

A printed wiring board (PWB) with electronic components has been modeled using the finite element technique and compared with the same PWB experimentally tested in a chassis during a 2 hr random vibration test. Accelerometers were attached to the PWB in locations where nodes existed in the finite element model (FEM). The FEM predicted the first natural frequency to within 10 percent of the test results. Due to wedge locks that loosened during the test, the PWB accelerations in the finite element model and the test differed by as much as 40 percent. The ceramic capacitor on the PWB was modeled in detail with leads attached to the PWB to examine bending stresses in the leads. During the 2 hr test there were no failures for those leads with adequate solder joints. A failure did occur, however, on a lead with insufficient solder. A fatigue analysis of the FEM lead bending stresses indicated lead failure if no solder was used, whereas no failures were predicted for properly soldered leads.