Chapter 5. Assembly and Mounting of Electronic Modules on Printed Circuit Boards

Abstract

Automation and mechanization of assembly and mounting of electronic modules yield the greatest efficiency gains in reducing the manufacturing complexity of products. Key pathways to enhance efficiency include the use of automated equipment and batch processing of new component bases, including surface-mount components. The preparation of electronic components for assembly entails several essential operations, including unpacking, incoming inspection, solderability testing, straightening, and lead forming. To ensure the solderability of printed circuit boards, immersion coatings have become widely adopted, achieved through a chemical displacement reaction in solution, providing sufficiently thin and uniform coatings on areas with exposed copper. Notably, immersion silver application involves the inclusion of organic compound additives to mitigate silver migration. Assembly operations require careful coordination of tolerances on lead and hole diameters, selection of an acceptable method for component fixation, and determination of the optimal arrangement of components on the board. The characteristics of universal machines capable of performing these operations are detailed. Furthermore, methods for fluxing, wave soldering of printed circuit boards, soldering with soldering irons, and employing soldering stations are thoroughly discussed. Special considerations regarding the cleaning of assembly joints and boards after soldering are also highlighted.