What is Inspection Overlay
An inspection overlay is a transparent sheet or film that is placed over a PCB during the inspection process. This overlay serves as a visual aid to assist in identifying and analyzing defects or anomalies on the PCB.
The purpose of an inspection overlay is to facilitate the comparison between the PCB under inspection and a reference board, often referred to as a “Golden Board.” The overlay may feature markings, grids, or patterns that help inspectors quickly identify any deviations or discrepancies between the two boards.
By overlaying the PCB with a transparent sheet, inspectors can visually compare the features on the PCB with the markings or patterns on the overlay. This comparison allows for the efficient and accurate identification of misaligned components, quality issues with plating on through holes, or the integrity of conformal coatings.
In addition to overlays, various techniques and methodologies are employed during the inspection process to ensure quality control. These may include precise measurements, the use of measurement software, oblique views, and the strategic use of illumination, such as UV lighting for assessing conformal coatings or infrared lighting to reduce glare during soldering checks.
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