Surface-mount Component Characterisation

David Craige Thomas


Computer aided design tools generally characterise surface mounted components in terms of their principle functional behavior. In real world applications components only behave ideally within a limited frequency range. The unintended behaviour outside of this frequency range is called parasitics. The aim of this project was to investigate the effects of parasitics on a range of surface mounted components, develop accurate equivalent circuits and demonstrate the benefits to simulation predictions. The motivation for this project was to improve the use of computer aided design tools within the circuit design process. This paper describes the process of constructing a lumped component equivalent circuit from the components frequency response. The theoretical research conducted led to the design of a modeling program that automates the process. The user is presented with a resistor, capacitor and inductor topology calculated from the de-embedded impedance response of the component. The modelling program went through incremental testing and validation using synthesised data before being implemented in the modelling of an arrangement of passive components. Its application was used to investigate the accumulative effects of parasitics through of modelling of a seven stage Butterworth filter. The results show a significant improvement in the simulation predictions with the likely variations a result of further parasitics associated with the transmission line connecting the components. Sensitivity analysis will show that the level of accuracy of the simulation is subject to the variation in component values, as stipulated by the manufacturers’ tolerances.


Surface-mount Component; Parasitics; Equivalent models

Full Text: