Happy Holden
Westwood Associates

Electronics continue to become denser, smaller and more complex. The drive to produce more hand-held applications is obvious, but "Mother Nature" is playing a big role in determining the other drivers. As chip signal rise-times continue to decrease (due to smaller gate geometries) the resulting signals are more susceptible to interconnect parasitics. Signal Integrity (SI) improves with miniaturization. All these smaller size factors are drivers for HDI with microvias.

Integrated Circuit increases in total gates has required more pins, as well as finer pin pitch. Over 2000 pins on a 1.0 mm pitch BGA is not unusual, as is 296 pins on a 0.65 mm pitch device. The faster rise-times, as well as the need for SI, require an increasing number of power and ground pins. Consequently, this drives the need for more layers in multilayers. Again, this drives the need for HDI with microvias.

This paper goes over the STEPS in deciding if you need HDI-microvias and how to START. Included is HDI Standards, design trade-offs, materials selection, fabricator selection and Benchmarking, test vehicles, HDI reliability, electrical performance, and CAD features for HDI.