Assembly inspection Automation implementation

This chapter covers why manufacturers inspect printed circuit assemblies, how they have implemented and enhanced visual inspection, what automated inspection systems they are using, and how they have implemented these antomated systems. The scope of this chapter includes only inspection of printed circuit assemblies during the assembly process, as typically shown in Fig. 53.1. Thus, it includes inspection of solder paste after the paste printing process step, components after the component placement process step, and solder joints after the solder reflow process step. Not included, however, is incoming inspection of components and the bare printed circuit board (PCB). The focus of this chapter is on prodnction nse of inspection, not the collection of measurements dnring process development in a research and development (R D) environment. 

Inspection systems normally are dedicated to one type of measurement capabihty solder paste, pre-reflow, or post-reflow inspection. For example, systems for solder paste measurements do not normally also make component placement measurements. The cost of combining different measurement capabilities into one system would typically make that system prohibitively expensive. More importantly, to reduce manufacturing costs, manufacturers want to implement linear, sequential production lines where an assembly always flows in one direction and goes through each machine only once per assembly side. So automated inspection systems fall into three major categories ... 

Successful implementation of automated inspection systems into printed circuit assembly production lines requires a significant investment in training, process analysis, and system integration. 

Assess requirements carefully Start by carefully assessing the requirements for automated inspection in the particular production environment into which the system will be integrated. Determine exactly what kinds of defects are most important for the inspection system to detect, which measurements will most help with process improvement, and what benefits will generate the quickest financial return on investment. This assessment must consider the testing and measurement capability that already has been implemented as well as new requirements arising from future printed circuit assembly designs. 

Implementation of the MID application in series production necessitated the development of a fully automated assembly solution by a manufacturer of special-purpose machines. The 3D placement of the SMDs, the switch elements, and the contact pins is only one of the functions discharged by the system. Others include incoming-goods inspection, electrical testing of the conductor tracks, dispensing the solder paste with optical process monitoring, and final inspection. [116]... 

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