Breaking out signals from an integrated circuit footprint

A system comprising:

• a printed wiring board having a plurality of signal routing layers, and a plurality of pads arranged as an integrated circuit package footprint that has a rectangular shape, wherein the plurality of pads are arranged in a grid pattern and are sized to have an average spacing between adjacent pads of 1.3 mm or less, the footprint having an inner pad region, a middle pad region that surrounds the inner pad region, and an outer pad region that surrounds the middle pad region, some of the pads of each pad region being connected to a respective plurality of signal lines formed in the plurality of signal routing layers,
• and wherein some of the signal lines that are connected to outer pads which are located in two corners of the rectangle are routed out of the footprint in a different one of the plurality of signal routing layers that is used to route the signal lines that are connected to outer pads which are located between the two corners, so that there is sufficient space to route out of the footprint some of the signal lines that are connected to inner pads, in the same signal routing layer used to route out the signal lines that are connected to outer pads which are located between adjacent corners, wherein a plurality of pairs of signal lines are routed out of the inner pad region in the same routing layer, wherein each pair of signal lines passes between a respective pair of adjacent pads in the corner and the two signal lines of each pair run parallel to each other through the middle and outer pad regions;
• and
• an integrated circuit package which is installed on the board to electrically connect to the plurality of pads.

A method for laying out a circuit, comprising:

• a) defining a representation of a plurality of pads for an integrated circuit footprint having a polygonal shape, an inner pad region, a middle pad region that surrounds the inner pad region, and an outer pad region that surrounds the middle pad region and that defines a perimeter of the polygonal shape, wherein the plurality of pads are arranged in a grid pattern and are sized to have an average spacing between adjacent pads of 1.3 mm or less;
• b) breaking out a plurality of signals of the middle pad region only on a first routing layer;
• and
• c) breaking out a plurality of signals of the outer pad region only on a second routing layer, except that those that are in a corner of the polygonal shape are broken out on only the first routing layer to make room for breaking out a plurality of pairs signals of the inner pad region on only the second routing layer through the corner;
• and
• d) breaking out the plurality of pairs of signals of the inner pad region on only the second routing layer, through the corner, wherein each pair of signal lines passes between a respective pair of adjacent pads in the corner and the two signal lines of each pair run parallel to each other through the middle and outer pad regions.

An article of manufacture comprising:

• a machine readable medium having instructions stored thereon which, when executed by a processor, cause an electronic system to display a representation of an article of manufacture in which there is an insulating layer between a plurality of signal routing layers, and a plurality of pads arranged as an integrated circuit footprint and formed in a stackup that includes the insulating layer and the plurality of signal layers, wherein the plurality of pads are arranged in a grid pattern and are sized to have an average spacing between adjacent pads of 1.3 mm or less, the footprint having a polygonal shape, an inner pad region, a middle pad region that surrounds the inner pad region, and an outer pad region that surrounds the middle pad region, some of the pads of each pad region being connected to a respective plurality of signal lines formed in the plurality of signal routing layers, and wherein some of the signal lines that are connected to pads of the outer region which are located in a corner of the polygonal shape are routed out of the footprint in a different one of the plurality of signal routing layers that is used to route the signal lines that are connected to pads of the outer region which are located between two adjacent corners of the polygonal shape so that there is sufficient space to route out of the inner pad region of the footprint a plurality of pairs of signal lines in the same routing layer, wherein each pair of signal lines passes between a respective pair of adjacent pads in the corner and the two signal lines of each pair run parallel to each other through the middle and outer pad regions.