A methodology for optimization of false call rate in automated optical inspection post reflow

In this paper a methodology for optimization of false call rate in automated optical inspection post reflow is presented. The Automated optical inspection (AOI) of assembled PCB´s is one of the most widely spread non-destructive testing method. It helps to ensure that defects created while the printed circuit board assembly is being manufactured are discovered before the product is shipped to final customer. The issue of false calls has become one of the keys to unlocking the potential of AOI. One primary goal has been that AOI is used most effectively as a feedback tool for yield improvement The presented methodology was introduced into 8 automotive electronics industry projects, where the false call rate was reduced by 56% in 10 months after its implementation. The methodology includes activities such as AOI inspection window optimization, AOI metrics definition, and design guideline for AOI in development (layout, HW and mech. design), bending of panels (warpage) prevention, set optical variation criteria. False call rate can be also dramatically reduced by introducing of 24 bits true color instead of 8 bits grayscale image processing.