Inspection System for Nano-meter Particle on Circuit Board used for New-medium with High Power Laser Diode

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Small particles (approximately larger than 1 mu m) adhered on to TFT-LCD (Thin Film Transistor-Liquid Crystal Display) plates in a production process cause the defects in circuit patterns. The particles have been detected strictly in a production process by employing automatic inspection systems.In this development, an automatic particle detection system with a high sensitivity and a high speed has been developed. The theoretical and experimental results with this system are summarized as follows.1. The high sensitive detection has been realized by developing the technology to illuminate a plate with a laser diode obliquely and to detect the forward light scattered by particles obliquely. The detected signal of a particle (diameter=1 mu m) on TFT-LCD has become 8-9 times as large as a detected signal with conventional inspection system when the incident angle is set to 75ﾟ and the detection angle is set to 45ﾟ.2. The high speed detection has been realized by developing a parallel detection system. In this system, the width of detection unit has been reduced to 100mm by combining an optical path for particle detection with an optical path for automatic focusing. The system uses 4 detection units which are controlled independently.3. This system enables to inspect a plate with the size of 360 * 460mm within 20 seconds and detect small particles lager than 1 mu m when the plate is inspected with 4 detection units.