US Patent 10559507 Direct wafer mapping and selective elastomer deposition

LEDs are manufactured on a substrate layer and picked and placed using a pick-up tool (PUT) onto a target substrate. The PUT typically attaches to an LED via an elastomer layer deposited on a surface of the LED. A given batch of manufactured LEDs may contain operational LEDs as well as non-operational LEDs. In order to separate the operational and non-operational LEDs, the LEDs are placed on a unidirectional conductive film. A voltage difference applied across the electrodes of each LED via the unidirectional conductive film powers the LEDs and causes the operational LEDs to emit light. An electrical parameter of each LED is measured and used to determine whether each LED is operational or non-operational. An elastomer deposition apparatus selectively deposits elastomer material on the operational LEDs, allowing for the operational LEDs to be picked up using the PUT, while not depositing elastomer material on the non-operational LEDs.