Preparation of Printed Circuit Boards

The vast majority of printed circuit boards (PCB’s) are of a rigid variety, the bulk of which are composed of layers of woven glass fiber cloth in a polymeric matrix. Flex circuits, which are becoming quite common, do not typically contain glass fiber, but instead, their bulk is often composed of layers of polyimide. The circuitry in both types of boards is composed of plated and/or foil metal. The metal used is generally copper, while in a few cases, gold and/or nickel plating may be present. Furthermore, depending upon whether the boards have undergone assembly or shock testing, solders of various compositions might also be present. Luckily for the metallographer, the variety of materials present in PCB’s generally do not complicate the preparation methods due to the fact that extremely hard and brittle materials are not commonly found in the boards. This changes, however, when ‘packed’ boards with ceramic or semiconductor components must be sectioned.

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