Machine vision for alignment and inspection in die bonder

Machine vision is widely used in die bonders to provide perfect alignment between the wafer or leadframe and the die pickup tip during pick and place operations respectively. This also results in better detection of bad ink-dotted dies and accurate placing of epoxy resin on the die bond pads of the leadframe. Pattern matching using Pattern Recognition techniques and area alignment using edge detection techniques are the two most widely used methods in providing die and leadframe pad alignment. The increased emphasis on quality improvement on semiconductor assembly has results in the use of machine vision for quality inspection in addition to alignment. The inspection is usually, done at two points in the die bond cycle, one just after epoxy application on the leadframe pad (pre-bond inspection) and the other after the die is bonded to the leadframe pad. The post bond inspect confirms if the placement of the die on the leadframe pad is within the required specification. It also looks for angular die placement as well as for epoxy spills on top of the die.