Crosstalk reduction in electrical interconnects
Embodiments reduce crosstalk between electrical interconnects by offsetting pairs of electrical interconnects in an electrical system to produce a staggered interconnect pattern for which magnetic flux through a loop formed by a victim interconnect pair is effectively canceled. Magnetic field vectors generated by an aggressor pair of interconnects can pass through a loop-bounded surface defined by a victim pair of interconnects in the system. In the staggered interconnect pattern, the victim interconnect pair is offset with respect to the aggressor interconnect pair so that the field vectors passing through the victim pair's loop-bounded surface in one direction are substantially balanced by the field vectors passing through the victim pair's loop-bounded surface in the opposite direction, thereby minimizing the effect of the aggressor pair's magnetic field on the victim pair. Since crosstalk is proportional to the rate of change of the magnetic flux, reducing the magnetic flux can reduce the crosstalk.
1. A method comprising:
first integrating a first pair of electrical interconnects with a package structure to carry first complementary signals;
calculating a location for a second pair of electrical interconnects, such that:
a first axis passing through the first pair is parallel to and non-co-linear with a second axis passing through the second pair,
the location offsets the second pair from the first pair along the second axis by an amount that minimizes an integral of magnetic flux density of a magnetic field over a loop-bounded surface, wherein the first pair defines the magnetic field when carrying the first complementary signals, and the second pair defines the loop-bounded surface when carrying second complementary signals; and
second integrating, at the calculated location, a second pair of electrical interconnects with the package structure to carry the second complementary signals.
2. The method of claim 1 , wherein:
the first integrating comprises separating the first pair of electrical interconnects by a distance d; and
the second integrating comprises offsetting the second pair from the first pair along the second axis by less than d.
3. The method of claim 2 , wherein:
the second integrating comprises offsetting the second pair from the first pair along the second axis by greater than 0.75 d.
4. The method of claim 1 , wherein the first complementary signals are a pair of differential signals.
5. The method of claim 1 , wherein one electrical interconnect of the first pair is a signal path, and another electrical interconnect of the first pair is a corresponding return path.
6. The method of claim 1 , wherein:
the magnetic field comprises a plurality of vectors; and
the second integrating comprises offsetting the second pair from the first pair along the second axis to the location that substantially balances between those of the plurality of vectors crossing the loop-bounded surface in a first direction, and those of the plurality of vectors crossing the loop-bounded surface in a second direction that is opposite the first direction.
7. The method of claim 1 , wherein the calculating comprises:
simulating a crosstalk between the first pair and the second pair over a plurality of candidate offsets; and
identifying the location as a candidate offset resulting in a minimum simulated crosstalk.
8. The method of claim 1 , wherein the calculating comprises:
simulating a crosstalk between the first pair and the second pair over a plurality of candidate offsets; and
selecting one of a plurality of manufacturable offset options closest to a candidate offset resulting in a minimum simulated crosstalk.
9. The method of claim 1 , wherein each electrical interconnect of the first pair of electrical interconnects is at least one of an input/output (I/O) pin, an I/O bump, a ball grid array (BGA) element, or an I/O via.
10. The method of claim 1 , wherein the package structure comprises at least one of an integrated circuit package, a printed circuit board, an electrical socket, an electrical connector, or an electrical interposer.