TABLE OF CONTENTS Lee W. Ritchey
3Com Corp., Santa Clara, California
Printed circuit boards (PCBs) or printed wiring boards (PWBs) can be divided into two general classes which have common characteristics based on their end functions. These two classes have very different materials and design requirements and functions and, as a result, need to be treated differently throughout the design and fabrication processes. The first class contains analog, RF, and microwave PCBs such as are found in stereos, transmitters, receivers, power supplies, automotive controls, microwave ovens, and similar products. The second contains digital-based circuitry such as is found in computers, signal processors, video games, printers, and other products that contain complex digital circuitry. Table 13.1 lists many of the characteristics of each class of PCBs.
| RF, microwave, analog PCB | Digital-based PCB |
|---|---|
| Low circuit complexity | Very high circuit complexity |
| Precise matching of impedance often needed | Tolerant of impedance mismatches |
| Minimizing signal losses essential | Tolerant of lossy materials |
| Small circuit element sizes often essential | Small circuit element sizes desirable |
| Only 1 or 2 layers | Many signal and power layers |
| High feature accuracy needed | Moderate feature accuracy needed |
| Low/uniform... |
