Automatic measurement and grading of LED dies on wafer by machine vision

Dramatic changes are unfolding in lighting technology. Semiconductor light-emitting diode (LED), which was once used mainly as simple indicator lamps in electronics and toys, has now become one of the most popular lighting device in our daily life. As the LED industry becomes prosperous, techniques for improving production efficiency become more and more important. A system integration method is proposed in this paper for improving the LED measurement and sorting speed in the testing process. This approach combines the mechanical technology, optical measurement instruments, and machine vision to create an affordable, flexible, and highly efficient LED grading system. The average speed of measurement and sorting is 3.5 LED dies per second based on repeated testings and evaluations. The experimental results demonstrate the effectiveness and robustness of the proposed system.