Effect of Nonlinear Interactions of Electronic Assemblies in Response to Multiaxial Vibration

Electronic packages are often exposed to complex life cycle environments, and in many cases, that involves exposure to multiaxial vibration. Previous studies have shown that under moderate or high amplitude multiaxial vibration, electronic systems can experience nonlinear response, especially for heavy components with high stand-off. This can produce cross-axis nonlinear interactions, resulting in amplification (or cancellation) of the nonlinear response, in comparison to the responses to uniaxial excitation along orthogonal axes. This nonlinear interaction has obvious implications on vibration durability of the assembly. The study performs a parametric combination of uniaxial and multiaxial vibration testing and modelling on structures that are mechanically equivalent to tall heavy electronic components, with varying loading parameters. Mechanical beams are designed as scaled surrogates to represent the dynamical behavior of Printed Circuit Boards (PCBs) with tall and heavy components on it. To investigate the nonlinear effects of multiaxial vibration excitation under different loading conditions, mechanical beams of different mass and length have been tested under different excitation profiles. The result shows that multiaxial vibration excitation can produce significant amounts of nonlinear cross-axis interactions, thus raising questions about the effectiveness of the traditional methodology of superposition of uniaxial vibration excitation for PWAs. The severity of nonlinear response depends not only on excitation parameters such as frequency ratios, phase relationships and amplitudes, but also on the component architecture. The resulting crossaxis interaction increases as the component becomes taller and heavier, which shows correlation between the size of the component and the nonlinearity of the vibrational response. The findings of this study will provide important guidance for developing protocols for multiaxial vibration testing instead of sequential uniaxial vibration testing.