Automatic opitcal through hole inspection method for printed wiring boards using leakage light detection

New automatic through hole inspection techniques for printed wiring boards (PWBs) were developed. The new method called Leakage Light Detection can detect defects such as cracks and breaks in plating of through holes with aspect ratio as large as ten. A prototype system for automatic through hole inspection is constructed, based on these techniques. This system detects defects in a 250 mm × 250 mm area of a PWB in 8 minutes.