Simplified analysis of pcbs response to random vibrations

Abstract eng:
This paper summarizes the results of a research programme that was carried out with the aim to offer an alternative to the standard practice implemented in the aerospace industry to carry out the mechanical design of enclosures containing Printed Circuit Boards (PCBs), and in particular the assessment of the PCBs capability to withstand the launch vibration environment. The response of the PCBs to the vibration environment was calculated using standard FEA and the “smearing” technique (i.e. the electronic components on the PCB are not geometrically modelled, and their influence on the boards dynamics is reproduced by smearing their mass and stiffness contribution on the shell elements representing the board). The level of accuracy that these FE models typically achieve and the influence of the modelling simplifications have been quantified. This allows to calculate suitable Safety Factors that can be applied in specific circumstances to compensate for the inaccuracies in the predictions. The paper then briefly describes a test campaign carried out with the aim to correlate the failure of electronic components on the PCBs with some typical FEA output. The capability to predict the response with a known level of accuracy (compensated by suitable Safety Factors), together with reliable failure criteria for the electronic components on the board, allow us to assess whether or not a design will be able to withstand a particular environment. Although this process requires a certain amount of work to be carried out upfront, its implementation in an industrial environment is relatively straight forward, with the main benefit of reducing considerably the current “trial and error” experimental work.

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