Summary Chapter Four: Electrical Performance

The good old days of 10 to 16 MHz clock frequencies are gone. It used to be the chief design challenge in circuit boards or packages was routing all the signals in two layers and getting packages that wouldn’t crack during assembly. The electrical properties of the interconnects were not important because they didn’t affect system performance. But the world has changed in the past 10 years. Clock frequencies on chip now are over 3 GHz, and on board, are over 800 MHz. In most systems, as the clock frequency goes up, the rise time always gets shorter. A shorter rise time means signal integrity problems increase dramatically. Signal integrity is broadly concerned with the problems that arise from how the electrical properties of the interconnects and power distribution affect system performance. External signals can affect noise as well as the return path for signals along planes. HDI provides miniaturization, smaller and shorter vias, shorter interconnect lengths with smaller parts and finer pitch devices, thinner and lower dielectric-laser drillable dielectrics and embedded components. These can be enabling techniques for improved high-frequency electrical performance.