Defect diagnosis of solder joints using fuzzy logic

This paper describes how the methods of fuzzy logic can be used in the classification of solder joint inspection results. The inspection results of over 900 circuit boards have been analysed for the purpose of distinguishing the essential characters of defective and decent solder joints. Also the effect of the prevailing average solder amount of each component type on the decision making process has been considered. The developed prototype of a fuzzy classifier of defect reports accomplishes the classification by using the information received from the solder joint inspection system. Defect reports are classified to be either justified or unnecessary. The classifier is able to detect about 80% of unnecessary defect reports and thus reduces the amount of work in the required visual re-inspection.