An Automated Optical Inspection System for PIP Solder Joint Classification Using Convolutional Neural Networks

In the fields of electronics manufacturing, the application of through-hole devices is still required, as heat dissipation and high current carrying capacity plays an important role. To ensure the highest quality standards, these electronics production processes take a multitude of inspection processes into account. For the detection of error patterns regarding the quality of the solder connections, usually, high-end inspection machines are utilized in the industrial application. The Automated Optical Inspection is a commonly conducted process, using visible light and rule-based inspection routines, setup by process experts for the evaluation of the Region of Interest. The high overhead of creating and maintaining product-specific checking routines and machine acquisition leads to increased costs and severe dependency on expert know-how. A flexible inspection algorithm, implemented into low-cost equipment for image generation is expected to reduce acquisition and optimization costs, and lower dependency on expert knowledge and high-end machinery. In this contribution, we present a novel framework for the automatic, near real-time solder joint classification based on Convolutional Neural Networks, flexibly detecting, and classifying solder connections. We utilize existing Deep Learning architectures for detection and classification. The localization model utilizes a YOLO-architecture (you-only-look-once), learning feature inputs based on a supervised learning approach. Pseudo-labeling is carried out automatically by an anomaly detection model. The image generation is executed by an industrial low-cost camera and an industrial rack-PC. The developed prototype is integrated into the existing production infrastructure. The results indicate a satisfactory detection and classification of the investigated solder connections with the proposed system. Hence, this system represent an alternative to commercially available high-end inspection systems being used for an inline control of Pin-in-Paste and through-hole device solder connections.