SOLDER JOINT INSPECTION USING AIR STIMULATION SPECKLE VIBRATION DETECTION METHOD AND FLUORESCENCE DETECTION METHOD

The fast and highly reliable method reported here uses two techniques to detect all types of defects, such as unsoldered leads, solder bridg es, and misaligned leads in the minute solder joints of high density m ounted devices. One technique uses external force applied by an air je t that vibrates or shifts unsoldered leads. The vibration and shift is detected as a change in the speckle pattern produced by laser illumin ation of the solder joints. The other technique uses fluorescence gene rated by short-wavelength laser illumination. The fluorescence from a printed circuit board produces a silhouette of the solder joint and th is image is processed to detect defects. Experimental results show tha t this inspection method detects all kinds of defects accurately and w ith a very low false alarm rate.