Stencil Design and SPI

Automated in-line solderprocess inspection (SPI) has the potential to deliver some of the highest value among all inspection steps because defects caught at this point in the process require minimal rework. It is simply a matter of cleaning solder paste off the printed circuit board (PCB). Additionally, good printing performance typically represents 80% of a successful SMT assembly process. As the bulk of workmanship-related defects tend to track back to deficiencies in solder paste deposition, closely monitoring control limits in this area has a substantial impact on eliminating defect opportunities.

Automated inspection equipment is only as good as its programming, however. As a result, variations in stencil design created to address design for manufacturability (DfM) considerations can create issues in the way SPI equipment calculates process capability.

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