REDUCTION OF POST-PLACEMENT DEFECTS IN SURFACE MOUNT ASSEMBLY

Post placement defects are typically identified on a surface mount printed circuit board assembly line (i) just after components have been placed on wet solder paste and (ii) after solder reflow. These inspection steps should, in theory, help to identify the causes of the post placement defects and consequently assist in their correction. This research focused on the identification and correction of post placement defects in an ultrafine pitch surface mount printed circuit board assembly environment. Potential causes for post placement defects were identified. A strategy that combined theory with experimentation was used to reduce the incidence of these defects.
The first step was to understand the types of defects that occurred and their frequency. Several factors that could result in post placement defects were then systematically addressed. These included the dimensional integrity of the boards and components used and the impact of the self centering of peripheral leaded components. The results of the experiments conducted within this research along with the appropriate inferences were used to generate recommendations that can reduce the occurrence of post placement defects. Ideas for future research are also provided.