抄録
It is very often that top fillet profiles of Pb free solder connected with QFP (Quad Flat Package) leads fluctuate more than those of Pb eutectic solder and have coarse surface roughness. The fluctuation and surface roughness make it difficult to carry out the feature extraction of the top fillet. The purpose of the present study is, therefore, to extract the top fillet profile characteristics using a simple image processing.
Pb free solder used in the present study was Sn-3.5Ag-0.7Cu. QFP leads plated with Sn-10Pb or Au/Pd/Ni were used as an inspection object. As a prior work, we investigated an appropriate observing direction, that is, the camera angle to obtain highlight in the vicinity of the top fillet (the side of QFP lead edge) and the distribution (fluctuation) of the camera angle were examined, because the camera angle was closely related with the wetting angle at the top fillet. The good profiles of the top fillet could be judged, i.e., the top fillet profiles with a proper wetting angle were decided by whether or not a certain highlight area (island) was observed. It was found that the judgement was possible if the size of the island (number of pixels with level 1 after binarization) was adequately regulated.
