Study on automatic angle correction directed by machine vision in power LED dies sorting

All dies are required to keep consistent angles in LED chip sorting. Generally, all chips are adhesive to wafer tape. When each die rotates, all other dies rotate and their positions change. To solve this problem, an on-line angle correction method is put forward. Techniques including reverse computing angle offset and moving displacement for die angle correction are discussed in detail. While, experimental results disclose that it is not enough for power LED die angle correction. Active visual rectification is then used for this. In this way, each correction is done by machine vision detects. Experimental results show that many deficiencies are eliminated and maximum value of die angle declination can be corrected to less than 1.25°. It can be concluded that final effects for angle correction has been better.