Study on real-time correction method of die declination angles in LED sorting system

All dies are required to keep consistent angles in LED chip sorting. Usually, rectification orient real-time vision is used for this but it may decrease production efficiency greatly, because one correction may need several adjustments. Considering that all dies to be sorted are adhesive to wafer tape, each is rotated, locations of all other dies change. It is a problem for following positioning and sorting. To solve this problem, an on-line angle correction method basing on translation compensation is put forward. In this way, angle deviations of dies are transformed as translations of recycling bins. Each die declination can be corrected without any rotations. It does little impact on sorting efficiency because the translation of recycling bins acts concurrently with the die ejection and transporting, etc. Techniques on figuring out displacement compensations are discussed in detail. In addition, SPN model of declination angle correction is built to analyze its influence to production rate. With theoretical analysis and experimental results, it is revealed that sort efficiency may decrease by only 3% for angle correction. Such effect is perfectly acceptable.