2004 Volume 22 Issue 2 Pages 323-333
Feature extraction of Pb free solder fillet profiles for QFP (Quad Flat Package) lead connection is discussed for the purpose of making it easy to recognize the front fillet profiles. Kinds of Pb free solder used in the present study were Sn-3.5Ag-0.7Cu, Sn 3.5Ag-3.0Bi-1.0Cu and Sn-3.5Ag-2.5Bi-2.5In systems (contents in mass %). Au/Pd/Ni plated leads connected with Pb free solder were mainly investigated and compared with Sn-10Pb solder plated leads. Wetting angles of the top fillets in the vicinity of lead edges were measured by changing the camera angle. The wetting angle and the scattering were different between kinds of solder. The highlight area of front fillet images was, therefore, influenced by the scattering of wetting angles. The luminance distribution affected by the surface roughness of solder fillets was also measured and the scattering of luminance (highlight) was investigated to reduce errors for the front fillet pattern recognition. It was suggested that two factors; the proper camera angle to obtain a highlight area at the top fillet zone and the luminance scattering (standard deviations) were very important for developing the image processing of Pb free solder fillet. A simple image processing method (for averaging the luminance distribution and decreasing the highlight scattering)proposed in the present study was useful for obtaining the stable characteristics extraction of Pb free solder fillet profiles.
