Adaptive real-time fuzzy X-ray solder joint inspection system

In this paper, a fuzzy logic-based embedded software, Fuzzy Expert System for X-ray Inspection (FESXI), for the inspection of soldering defects in an electronic manufacturing process of Nokia Networks, is presented. The FESXI was developed to improve the X-ray inspection results of signal transmission products by reducing false alarms to prevent unnecessary rework and increasing the throughput time of production. Inspection results are inferred from a set of input measurement values. Each input value is fuzzified using automatically generated and continuously updated fuzzy membership functions, and fuzzy results are inferred with the aid of a compact rule base, where rules are presented by linguistic relations changed into matrix equations form. The model produces more accurate decision-making support than the traditional dual logic-based approach of commercial X-ray machines. Experimental results showed that false alarms can be reduced by about 44% using the software, and since the first test, it has been in daily production use.