エア加振・スペックル振動検出法によるはんだ付部検査方式の開発

抄録

A high-speed and highly reliable inspection method which inspects minute solder joints of high-density-mounted devices has been developed. A human inspector touches a solder joint by a pinset to identify a “floating lead” defect which is like a good joint cosmetically. The developed method applies force to solder joints by air jet externally and induces vibration or shift of a floating lead. The vibration or shift is detected as a change of speckle patterns which are produced at a solder joint by laser illumination. For reconciling with highly sensitive detection of speckle pattern changes and separable detection of each individual joint in a narrow pitch row of solder joints, defocus amounts in x and y directions are set separately by a cylindrical lens. For decreasing dispertion of detected light intensities of individual solder joints, a liquid crystal filter is inserted in a detection light path and the control of light intensities of individual joints is realized. As defect judgement, two functions which evaluate proportions of vibration and shift from a detected speekle waveform are introduced. The result shows that the developed inspection method detects floating lead defects accurately with a very low false alarm rate.