Backplane with routing to reduce layer count

A backplane comprising:

• a) a first plurality of groups of backplane connector modules including at least a first central group and a second central group, each group disposed in a column, with the columns being parallel, with each connector module having a plurality of contact tails and the connector modules being positioned to leave spaces between modules in each column;
• b) a second plurality of groups of backplane connector modules, each group disposed in a column, with each connector module having a plurality of contact tails and with the columns being parallel to the columns of the first plurality of groups, and the columns being disposed on a first side of the first central group and the second central group;
• c) a third plurality of groups of backplane connector modules, each group disposed in a column, with the columns being parallel to the columns of the first plurality of groups, with each connector module having a plurality of contact tails and the columns being disposed on a second side of the first central group and the second central group;
• d) a first plurality of groups of signal traces, each group connecting contact tails of a first module in each of the second plurality of groups to contact tails of a module in the first central group;
• e) a second plurality of groups of signal traces, each group connecting contact tails of a second module in each of the second plurality of groups to contact tails of a module in the second central group, each group of signal traces in the second plurality of groups passing through a space between adjacent connector modules in the first central group;
• f) a third plurality of groups of signal traces, each group connecting contact tails of a first module in each of the third plurality of groups to contact tails of a module in the second central group;
• and
• g) a fourth plurality of groups of signal traces, each group connecting contact tails of a second module in each of the third plurality of groups to contact tails of a module in the first central group, each group of signal traces in the fourth plurality of groups passing through a space between adjacent connector modules in the second central group.

A method of designing a backplane for an electronic system having a plurality of first type daughter cards each having a plurality of connections to at least two second type daughter cards, with each first type daughter card connected to the backplane at a point that is nearer to the connection point for one of the second type daughter cards than to the connection point for another of the second type daughter cards, the method comprising:

• a) generating a schematic for the backplane;
• b) generating a netlist from the schematic;
• c) back annotating the schematic to direct traces carrying signals from a daughter card to a further one of the second type daughter cards to pass in groups through routing channels between connectors for attaching to a nearer one of the second type daughter cards;
• and
• d) re-generating the netlist from the back annotated netlist.