Automated assembly of LEDs based on the self-assembly method

Abstract
The long lasting trend of miniaturization leads to increasing functionality but also to continuously shrinking devices. These small devices have to be automatically handled in assembly processes. LEDs (light emitting diode) are reaching nowadays a feed size of 300µm. The automatic handling and positioning of devices is getting more complex with its miniaturization. Surface forces play an increasing role and affect the common handling process. These effects are occurring at device sizes of approx. 500µm and smaller.
The self-assembly process is using these surface forces for a precise handling and positioning of small devices. The surface, on which the device should be positioned, is functionalized in hydrophobic and hydrophile areas. The hydrophile area is wetted with ultrapure water and caught by the hydrophobic surroundings. The device is deposited on this droplet and due to surface tension aligned according the hydrophile shape. Investigations have shown that a transition of the devices onto the droplets can be realized without using standard grippers.