Study on intelligent detecting technology for solder joint quality of SMT based on fuzzy diagnosis technique

The paper proposes a method that realized the solder joints assembly quality fault diagnosis. After an analysis of fuzzy fault diagnosis principle of SMT products, geometrical shape parameters which reflected PQFP solder joint quality were studied. Reasonable shape of components solder joint was built based on minimal energy principle. Then through the study of the real solder shape, the graphic token of SMT solder joint shape is abstracted by x-ray optical method. Afterwards, multiple input and output fuzzy systems were designed and developed. Based on the relation of solder joint shape and graphic parameter, combined with the solder shape theory, fuzzy System for fault diagnosis of solder joints quality in SMT is established by using MATLAB fuzzy toolbox and GUI. Finally, a case was studied to testify its correctness. Applying the fuzzy illation, the type and cause of defection is identified quickly and conveniently.