Real time X-Ray solder joint inspection with the aid of fuzzy decision making

Wei Xu, Tapio Frantti

Research output: Contribution to journalArticleScientificpeer-review

6 Citations (Scopus)


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.
Original languageEnglish
Pages (from-to)111-125
JournalJournal of Manufacturing Systems
Issue number2
Publication statusPublished - 2002
MoE publication typeA1 Journal article-refereed


  • decision making


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