Study on auto-path planning according to grade priority for sorting dies

Semiconductor light-emitting diode (LED) has now become one of the most popular lighting devices. Before diodes are put into process of package, they need be inspected and graded strictly, so following waste will be saved. Cost of inspection and sort is relatively high, it is urgently needed to improve sort efficiency and reduce sort time. This is a problem needs comprehensive consideration. Sort performance is influenced by acts such as feeding, ejecting, transporting, placing, recycle bin positioning, and so on. Stochastic Petri net model of concurrent control of multi-shafts scheduling is built to analyze the performance and its influenced factors. It can be revealed that positioning of recycle bins is the major influence factor. Because of this, a path planning method according grade, the diodes with same grade should get priority to be sorted first, is put forward. Techniques about die search and merge by grade, traversal of forward and backtrack with cross priority are described in detail. With reasonable simulations, this optimization is obviously proved effective to reduce sort time and improve diodes production rate.