The dependency of the signal behaviour of complex PCB nets on the parasitic parameters (PP) of these nets has been determined by measurements and simulations. These nets can be grouped into the net-parts on the PCB, on the Chip Packages and on the Chips. This was done for nets of several real life PCB designs. It was found that the impact of the chip package only on the signal behaviour of longer PCB nets ( multi-drop, at least 5cm) can vary from significant to not important for the same net. That depends on the signal rise times of the off-chip drivers (OCDs), the geometrical net configuration and the number of switching OCDs. When the OCDs of many board nets e.g. address lines are switching simultaneously, a considerable degradation and deformation of the slopes of the individual address line was observed.

In the investigated cases where signal slope degradation was found it could be shown that the coupling into/between the net-vias plays a key role and significantly determines the signal behaviour of the total net. The energy which causes the via coupling is guided by the surrounding parts of the power plane pairs, in which the coupled vias are embedded. With other words: The coupling between nets and also the di/dt behaviour of groups of switching OCDs are in most cases dominantly determined by the coupling between the vias involved and the - the vias surrounding - power planes.

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