Publications Details

Rapid prototyping of a micro pump for microelectronic applications

Wong, C.C.; Chu, Dahwey; Liu, S.L.

A micro electro-hydrodynamic (EHD) injection pump has been developed using laser micromachining technology. Two designs have been fabricated, tested, and evaluated. The first design has two silicon parts with KOH-etched wells which are stacked on the top of each other. The wells are etched into one side of the wafer, and gold is deposited on the other side to serve as the pump electrodes. A Nd:YAG laser is used to drill an array of circular holes in the well region of both silicon parts. This creates a grid distribution with a square pattern. Next the well regions of the silicon parts are aligned, and the parts are bonded together using a Staystik thermoplastic. Together, the bonded siliconpart form the pump. The pump unit is then mounted into a ceramic package with a large hole drilled in the bottom of the package to permit fluid flow. Aluminum ribbon wire bonds are used to connect the pump electrodes to the package leads. Isolation of the metallization and wires is achieved by filling the package cavity and coating the wires with polyimide. When a voltage is applied to the electrodes, ions are injected into the working fluid, such as an organic solvent, thus inducing flow. The second design has the silicon parts oriented {open_quote}back-to-back{close_quote} and bonded together with Stayform. A {open_quote}back-to-back{close_quote} design will decrease the grid distance so that a smaller voltage is required for pumping. Experimental results have demonstrated that this micro pump can achieved a pressure head of about 287 Pa with an applied voltage of 120 V.