If you have purchased a computer in the last few years, you've probably noticed that what you thought was a hare then is a tortoise by today's standards. Computers and other electrical devices are only limited by their components. As a result, the demand for high speed PCB designs has increased significantly as the demand for faster computers has increased.

High speed PCB designs usually require several layers--exceeding 20 layers is not uncommon. This contrasts sharply with typical PCB designs which have six boards on average. As the number of layers increases, both the cost of manufacturing and the complexity of the circuitry increase.

Crosstalk in High Speed PCB Designs

On a crowded PCB with several traces, the amount of electrical noise generated can interfere with the signal in any particular trace. This is particularly true in high speed PCB designs that have many more layers than typical boards. The resulting problem, known as crosstalk, is essentially interference created in a trace due to the signal from other traces.

One way to avoid this is to increase the space between traces. Designers, however, are trying to fit more traces onto smaller PCBs so that end products can be smaller. The size of final products, such as computers, is constrained by the size of the circuit boards. Small form factor computers that require motherboards capable of high speeds are only now starting to reach the mainstream. If the speed of computers is to continue increasing, high speed PCB designs must continue to improve.