Using AI and AOI to draw conclusions about the quality of printed circuit boards

Limtronik, based in Limburg an der Lahn (Germany), is a Joint Development Manufacturing (JDM) partner and expert in Electronic Manufacturing Services (EMS). The company accompanies its customers from product development to the final product ready for series production. The company's focus is on the development and production of electronic assemblies as well as customized systems for customers. "Error prevention and quality assurance are top priorities for us as an electronics factory. In addition, we have to meet corresponding standards in some industries. We have therefore already been implementing traceability for several years. The fact that all production data is recorded, documented and evaluated in the course of this also creates the ideal data basis, for example, for developing automated control loops to avoid errors in the production process," explains Gerd Ohl, Managing Director of the company.

Limtronik ensures traceability with a Manufacturing Execution System (MES) from the manufacturer iTAC and two laser markers from SmartRep. These enable each PCB to be marked with an in-house serial number. The laser marker is connected to the MES. The production line only runs if all products have been lasered without errors by the laser and the codes have been assigned. In case of deviations, a complete process interlock of the line takes place.

3D inspection systems for defect detection and process optimization

In addition to the laser markers, inspection systems such as SPI and AOI systems from Koh Young also contribute to automation and quality assurance at Limtronik. The Koh Young solutions are offered and implemented by SmartRep as a service partner.

Koh Young's 3D inspection systems are aimed not only at pure defect detection, but also at controlling and optimizing the entire process. "The solder paste printing process is the most important process for us. If the print is not in order, we get immediate feedback from the Koh Young SPI and can stop and improve the process accordingly," explains Dieter Jung, Head of Technology at Limtronik.

Two Koh Young SPI systems have already been in use since 2011. A third system was added recently. In 2022, the electronics factory also implemented three Koh Young AOI solutions, moving from 2D to 3D inspection technology. The AOI ensures that the quality control of the complete line is displayed. It tracks inspection results across all PCBs and locks the process in the event of poor assembly - preventing serial defects. The AOI stores its data in the MES database. At the end of the process, all data can be retrieved via the database for a unique ID.

Massive reduction of pseudo errors

However, Koh Young's AOI solution goes far beyond fault detection and process interlocking. Trend analyses and histograms can be used to trace the origin of faults and preventive measures can be initiated. In addition, Limtronik can now perform real-time analyses through data evaluation with KSMART. Artificial intelligence is used for programming: Unknown components no longer have to be added to the component library by hand, but are taught by the system itself using Koh Young's auto-programming with the help of artificial intelligence.

"By switching to Koh Young 3D AOI technology, we have been able to reduce our pseudo defects by up to 70-80 percent. This saves us effort and resources that can be used for important tasks in other areas," says Dieter Jung and continues: "Koh Young's solutions have noticeably increased both employee satisfaction and production quality."

Source and further information: Limtronik GmbH