For the fabrication of a discrete micro actuator using Magnetic Shape Memory (MSM) alloys, various thin film fabrication technologies had to be investigated. Such an actuator needs an excitation coil system which is able to generate a suffice magnetic field of about 0.4T in the MSM material. This is the field strength necessary for affecting a crystalline reorientation of the MSM alloy which causes to the elongation of the material. Another important area for such a system is to coming up with highly permeable flux guide. In both cases, recent developments of the Institute for Microtechnology (imt) were taken advantage of.

The generation of a sufficiently great magnetic field depends on the thin-film coil design, in particular the number of turns and the cross section of the conductor. The latter determines the coil’s current carrying capability. Contrary to previous work, a double layer spiral coil with an aspect ratio of 1.5 to one of the conductor was chosen. It resulted in a conductor with a width of 23.5 µm and a height of 35 µm. There are four turnes per layer, resulting in a total number of 8 turns. To increase the filling factor, the insulation between the coil layers was fabricated of Si₃N₄ layer rather than SU-8^TM used previously. The deposition was accomplished by Plasma Enhanced Chemical Vapour Deposition PECVD in a process minimizing film tensions.

The second development was in the area of improving the magnetic permeability of the used electroplated soft magnetic alloy. A parameter study was conducted, varying the current density in relation to the coated area, as well as the deposition pulse ratio. As a result, relative permeabilities µ_r of up to 100 and 80 could be achieved for flux guides with a thickness of 40 µm and poles with a height of 70 µm, respectively. This was the value which was required to reach the simulated flux density in the MSM material.

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1. Simulation of Discrete Actuators using Magnetic Shape Memory Alloys