14.1 INTRODUCTION

Printed wiring assembly (PWA) fabrication is a complex procedure involving a variety of material processing steps. From a failure analysis perspective, a fully populated PWA is one of the most complex structures that an investigator may encounter. In this chapter, the term printed circuit board or PCB describes a bare board consisting of layers of conductors and insulators, while the term printed wiring assembly or PWA refers to a PCB with components attached to it. PCBs are fabricated from composite substrate materials and use laminated and plated copper for high-density electrical interconnections. Soldering processes are used to attach components ranging in complexity from resistors to sophisticated microelectronic devices. In addition, PWAs must often withstand significant mechanical and environmental stress in normal operation. Because of the complex nature of a modern, fully populated PWA, an investigator has a variety of areas to examine when analyzing a PWA failure.

In this chapter, some of the fundamental processes used in printed wiring assembly fabrication are reviewed, the materials used in those processes are discussed, and procedures for examining PWAs during the course of an investigation are covered.

14.2 CONSTRUCTION AND FABRICATION OF A PRINTED CIRCUIT BOARD