Electrical performance of card-on-board interconnections for high-speed digital applications

The continuing increase in circuit density and speed is placing an even greater burden on the electrical performance of intra-system interconnections. Both multiprocessor computer systems and communication networks are expected to require the propagation of 100 Mb/s-1 Gb/s type of data rates over lengths greater than 50 cm on relatively inexpensive card-on-board technologies. It is important to understand the key limiting factors and the directions needed for future development. In this paper we investigate the electrical performance of available high-density printed-circuit cards or boards and highlight the effect of skin-effect and dielectric losses. Several types of commercially available high-performance shielded pinned connectors for large size panels are modelled and their contributions to signal distortion and crosstalk are shown. The complete interconnection path starting from the driver circuit on one card and traversing representative board path to the receiver circuit on another card is analyzed and the practical extendibility limitations are discussed. Experimental results on specially built card and connector paths that emulate the actual use are compared with modelled waveforms.