Experimental and Modeling Studies Towards Random Vibration 2011-26-0118

The estimation of the mechanical reliability of the Printed Circuit Board (PCB) in an electronic system is considered to be an important part of the overall reliability of the system. The vibration often plays the key cause of invalidation and component failures. Since it is known that such vibration factors can induce various failures, an understanding of their dynamic response is warranted. Random vibration test is specified for acceptance tests, screening tests and qualification tests as it more closely represents the true environment in which electronic system must operate. In order to achieve a good vibration analysis, it is first necessary to efficiently and accurately understand the dynamic behavior of the system when subjected to specific environment like random vibration. Once the methodology is built, it can be applied for analyzing various systems with greater confidence in estimating their dynamic response.

This paper focuses on the methodology to understand and predict the dynamic behavior of the system using various approaches (like theoretical, numerical and experimental). The modal response of the model is acquired through the theory of vibrations of continuous systems. The same model is analyzed by finite-element method and also by experiment, thus, determining its dynamic properties like modal frequencies, mode shapes etc. Thus, the results obtained through all these approaches are compared in detail. Further, with an effort to understand the force response behavior of the system, Random Vibration analysis is carried out using a commercially available standard finite element software on the same model using specified Power Spectral Density (PSD) level as an input excitation, results in, response PSD and transmissibility curve assuming different damping ratio. Same scenario is replicated with the random vibration testing and then, these various results are compared for deducing the appropriate damping ratio which is one of the very important factor for dynamic analysis. Furthermore, using the result of simulation corresponding to deduced damping ratio, fatigue life is predicted based on three band technique.

As, very small and delicate electronic components are mounted on both sides of the PCB using solder joints, adhesive etc, various nonlinearities are encountered while modelling them for analysis. For avoiding the model complexity and minimizing the affecting variable, a simple cantilever model is considered for the present study.