Partial plug connections in the automobile industry show normal electrical behavior in the manufacturing final line, but fail later because of the loose connection. Mostly the real failure shows up while the product is already at the customer site, which results in high service costs and loss of reputation.

Given task

Quality assurance in the final production stage is often based on electrical contact detection. Automatic robotic testing or imaging systems will not detect partial connections due to the limited accessibility. Component suppliers are not able to assure 100% correct plug connections in modules (e.g. dashboards). New connectors with indicators or ejection mechanisms are very expensive and still cannot be detected automatically. Due to difficulties in accessing locations of the connections it seemed that there is no easy automatic measurement method.

A universal inspection system that works independently from the installed electrical function even in hard-to-access mounting situations was the development target. Mechanical solutions were not accepted, because they were expensive and needed additional time in production and service.

The solution – fluorescence

m·u·t‘s fluorescence detection system allows you to make accurate contactless optical measurement of incomplete plug/socket mating. UV illumination is established at the inspection facility and the inner part of the plug is treated with a fluorescence dye. The dye can be applied mechanically, either with injection molding or with pad printing during manufacturing. The estimated additional cost per plug connection is lower than 1 cent.

Our Spectrometer TRISTAN® is used to detect characteristic fluorescence signals. If the connection is fully mated, no fluorescent light is emitted. On a partial connection, the fluorescence color will appear in its characteristic spectral range. A area of less than 5 mm2 of an improper connection can be detected from a distance of 200 mm with standard spectrometer components.