Use of optoelectronic tweezers in manufacturing —accurate solder bead positioning

In this work, we analyze the use of optoelectronic tweezers(OETs) to manipulate 45  μm diameter Sn62Pb36Ag2 solder beads with light-induceddielectrophoresis force and we demonstrate high positioning accuracy. It was found that the positional deviation of the solder beads increases with the increase of the trap size. To clarify the underlying mechanism, simulations based on the integration of the Maxwell stress tensor were used to study the force profiles ofOET traps with different sizes. It was found that the solder beads felt a 0.1 nN staticfriction or stiction force due to electrical forces pulling them towards the surface and that this force is not dependent on the size of the trap. The stiction limits the positioning accuracy; however, we show that by choosing a trap that is just larger than the solder bead sub-micron positional accuracy can be achieved.

Source: Applied Physics Letters - December 2, 2016 Category: Physics Authors: Shuailong Zhang, Yongpeng Liu, Joan Juvert, Pengfei Tian, Jean-Claude Navarro, Jonathan M. Cooper and Steven L. Neale Source Type: research