Fabrication of Ni-W Microgears Using LIGA Process

Microgears made of Ni-W alloy that are expected to have high strength and ductility, i.e., high durability, were successfully fabricated by using the LIGA process with synchrotron radiation. Ni-W electrodeposited alloys have a Vickers hardness of about HV 600 and a tensile strength of about 2000 MPa or above for a sample thickness of up to about 20 mu m. However, they lose their excellent mechanical properties with increasing sample thickness. For this reason, Ni-W electrodeposited alloys have not yet been used in the LIGA process for the fabrication of microcomponents. We consider that the decrease in strength is due to the increased electric resistance of the Ni-W film during electrodeposition. To solve this problem, we developed a new process in which a copper reversing mold is fabricated in the first step, then Ni-W alloy is electrodeposited on the copper reversing mold to prevent the electric resistance from increasing in the second step as the mold forming process. Using this process, microgears with reference diameters from 1000 to 80 mu m were fabricated with high dimensional accuracy.