Superplastic backward microextrusion of microparts for micro-electro-mechanical systems

This study seeks to establish microforming technologies for micro-electro-mechanical systems (MEMS) parts such as microgears below 50 μm in module. For this purpose, it is important to develop new methods to fabricate microdies and to select suitable materials for microforming. Photochemically machinable glass has been used to fabricate microdies by photolithography and anisotropic etching techniques. Al–78Zn superplastic material and LaAlNi amorphous alloy have been employed in microextrusion. These materials have the great advantage of deformation under very low stresses in comparison with conventional plastic deformation. Furthermore, such materials exhibit good microformability. A new superplastic backward extrusion machine has been developed for this study. Specimens were placed in a container and extruded by a piezoelectric actuator in a vacuum or an argon gas atmosphere. Microextrusion has succeeded in forming microgear shafts. The gear of LaAlNi amorphous alloy is 50 μm in module. For Al–78Zn superplastic alloy, the module is 20 μm and the diameter of the pitch circle is 200 μm.